New Exact and Asymptotic Results of Dual-Branch MRC over Correlated Nakagami-m Fading Channels
Al-Quwaiee, Hessa
2015-05-01
We present in this paper a new performance analysis results of dual-branch maximal-ratio combining over correlated Nakagami-m fading channels with arbitrary fading parameter. In particular, we derive exact closed-form expressions of the outage probability, the average bit error rate, and the ergodic capacity in terms of the extended generalized bivariate Meijer G- function. Moreover, we also provide simple closed- form asymptotic expressions in the high signal-to- noise ratio regime of these three fundamental performance measures. © 2015 IEEE.
New Exact and Asymptotic Results of Dual-Branch MRC over Correlated Nakagami-m Fading Channels
Al-Quwaiee, Hessa; Alouini, Mohamed-Slim
2015-01-01
We present in this paper a new performance analysis results of dual-branch maximal-ratio combining over correlated Nakagami-m fading channels with arbitrary fading parameter. In particular, we derive exact closed-form expressions of the outage probability, the average bit error rate, and the ergodic capacity in terms of the extended generalized bivariate Meijer G- function. Moreover, we also provide simple closed- form asymptotic expressions in the high signal-to- noise ratio regime of these three fundamental performance measures. © 2015 IEEE.
Cooperative Spectrum Sensing over Non-Identical Nakagami Fading Channels
Rao, Anlei
2012-09-08
Previous works in cooperative spectrum sensing assumed that the channels for sensing and reporting are independent identical distributed (i.i.d). A more practical and appropriate assumption, however, should be that the sensing channels and reporting channels are independent but not necessarily identically distributed (i.n.i.d). In this paper, we derive the false-alarm probability and the detection probability of cooperative spectrum sensing with energy fusion over i.n.i.d Nakagami fading channels. Selected numerical results show that cooperative spectrum sensing still gives considerably better performance results even over i.n.i.d fading channels.
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Madeiro Francisco
2010-01-01
Full Text Available Abstract This paper presents an alternative method for determining exact expressions for the bit error probability (BEP of modulation schemes subject to Nakagami- fading. In this method, the Nakagami- fading channel is seen as an additive noise channel whose noise is modeled as the ratio between Gaussian and Nakagami- random variables. The method consists of using the cumulative density function of the resulting noise to obtain closed-form expressions for the BEP of modulation schemes subject to Nakagami- fading. In particular, the proposed method is used to obtain closed-form expressions for the BEP of -ary quadrature amplitude modulation ( -QAM, -ary pulse amplitude modulation ( -PAM, and rectangular quadrature amplitude modulation ( -QAM under Nakagami- fading. The main contribution of this paper is to show that this alternative method can be used to reduce the computational complexity for detecting signals in the presence of fading.
Rao, Anlei; Alouini, Mohamed-Slim
2012-01-01
In this paper, we analyze the performance of adaptive modulation with single-cell multiuser scheduling over independent but not identical distributed (i.n.i.d.) Nakagami fading channels. Closed-form expressions are derived for the average channel
Full-Duplex Relaying with Improper Gaussian Signaling over Nakagami-m Fading Channels
Gaafar, Mohamed; Khafagy, Mohammad Galal; Amin, Osama; Schaefer, Rafael F.; Alouini, Mohamed-Slim
2017-01-01
We study the potential employment of improper Gaussian signaling (IGS) in full-duplex relaying (FDR) with non-negligible residual self-interference (RSI) under Nakagami- m fading. IGS is recently shown to outperform traditional proper Gaussian
Cooperative Cognitive Radio Systems over Nakagami-m Fading Channels
Hyadi, Amal
2013-05-08
This thesis aims to investigate the incorporation of cooperative techniques in cognitive radio networks over Nakagami-m fading channels. These last years, spectrum sharing mechanisms has gained a lot of interest in the wireless communication domain. Using cooperation in a cognitive set up make the use of spectrum much more efficient. Moreover, it helps to extend the coverage area of the cognitive network and also to reduce the transmitting power and, thus, the generated interference. In this work, we consider two particular scenarios for cooperative cognitive radio systems. The first scenario consider multihop regenerative relaying in an underlay cognitive set up. The cooperation is performed in the secondary system, in the presence of multiple primary users. Both interference power and peak power constraints are taking into account. Closed-form expressions for the statistical characteristics and multiple end- to-end performance metrics are derived. Different scenarios are presented to illustrate the obtained results and Monte Carlo simulations confirm the accuracy of our analytical derivations. In the second part of this work, we consider an overlay cognitive network with the spectrally efficient two-phase two-way relaying protocol. Two relay selection techniques, optimizing both the primary and the secondary communication, are presented. The overall outage performance is investigated and an optimal power allocation scheme, that ameliorate the outage performance of the system, is proposed. Numerical simulations are presented to illustrate and compare the obtained results.
Asymptotic analysis for Nakagami-m fading channels with relay selection
Zhong, Caijun; Wong, Kaikit; Jin, Shi; Alouini, Mohamed-Slim; Ratnarajah, Tharm
2011-01-01
In this paper, we analyze the asymptotic outage probability performance of both decode-and-forward (DF) and amplify-and-forward (AF) relaying systems using partial relay selection and the "best" relay selection schemes for Nakagami-m fading channels
Distributed detection in UWB sensor networks under non-orthogonal Nakagami-m fading
Mehbodniya, Abolfazl; Bielefeld, Daniel; Aissa, Sonia; Mathar, Rudolf; Adachi, Fumiyuki
2011-01-01
. In this paper, we present an opportunistic power assignment strategy for distributed detection in parallel fusion WSNs, considering a Nakagami-m fading model for the communication channel and time-hopping (TH) UWB for the transmitter circuit of the sensor nodes
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Duong Trung Q
2007-01-01
Full Text Available We analyze the exact average symbol error probability (SEP of binary and -ary signals with spatial diversity in Nakagami- (Hoyt fading channels. The maximal-ratio combining and orthogonal space-time block coding are considered as diversity techniques for single-input multiple-output and multiple-input multiple-output systems, respectively. We obtain the average SEP in terms of the Lauricella multivariate hypergeometric function . The analysis is verified by comparing with Monte Carlo simulations and we further show that our general SEP expressions particularize to the previously known results for Rayleigh ( = 1 and single-input single-output (SISO Nakagami- cases.
Xia, Minghua; Aissa, Sonia
2012-01-01
the optimal end-to-end performance, the transmit powers of the secondary source and the relays are optimized with respect to average interference power constraints at primary users and Nakagami-$m$ fading parameters of interference channels (for mathematical
Chen, Yunfei; Alouini, Mohamed-Slim; Tang, Liang; Khan, Fahdahmed
2012-01-01
The performance of adaptive modulation for cognitive radio with opportunistic access is analyzed by considering the effects of spectrum sensing, primary user (PU) traffic, and time delay for Nakagami- m fading channels. Both the adaptive continuous rate scheme and the adaptive discrete rate scheme are considered. Numerical examples are presented to quantify the effects of spectrum sensing, PU traffic, and time delay for different system parameters. © 1967-2012 IEEE.
Chen, Yunfei
2012-09-01
The performance of adaptive modulation for cognitive radio with opportunistic access is analyzed by considering the effects of spectrum sensing, primary user (PU) traffic, and time delay for Nakagami- m fading channels. Both the adaptive continuous rate scheme and the adaptive discrete rate scheme are considered. Numerical examples are presented to quantify the effects of spectrum sensing, PU traffic, and time delay for different system parameters. © 1967-2012 IEEE.
Analysis of D2D Communications over Gamma/Nakagami Fading Channels
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Z. Hussain
2018-04-01
Full Text Available In this paper, we investigate the outage probability, channel capacity and symbol error rate (SER performance of device-to-device (D2D communication systems. The D2D communication system is affected by several co-channel interferers. Gamma fading channel is considered for the D2D communication system. The channel for the co-channel interference is assumed to be Nakagami faded. An expression for the probability density function (PDF of the signal-to-interference ratio (SIR is presented. The PDF is a function of distances between various devices in the D2D system, path-loss, channel fading conditions and signal powers. Based on the PDF expression, we present the expressions for the outage, channel capacity and SER. With the help of numerical results the performance of D2D communication system is discussed under various conditions of interference, path-loss and channel fading.
Outage performance of Decode-and-Forward partial selection in Nakagami-m fading channels
Benjillali, Mustapha
2010-01-01
In this paper, we investigate the outage performance of Decode-and-Forward with partial selection relaying in dualhop cooperative Nakagami-m fading links. The source, based on the unique knowledge of local first hop channel state information, selects the best relay to increase the chances of successful decoding and hence the possibility of cooperation when the direct link is also available. After deriving the exact distribution of the sum of two gamma variates with the same shape parameter, the outage probability of the system-with and without the direct link-is obtained in closed-form. We also derive the ε-outage capacity in different particular cases, and the obtained results- when the channel model is reduced to a Rayleigh fading-are either new or correspond to those previously obtained in other works. Simulation results confirm the accuracy of our analysis for a large selection of system and fading parameters. © 2009 IEEE.
Symbol Error Probability of DF Relay Selection over Arbitrary Nakagami-m Fading Channels
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George C. Alexandropoulos
2013-01-01
Full Text Available We present a new analytical expression for the moment generating function (MGF of the end-to-end signal-to-noise ratio of dual-hop decode-and-forward (DF relaying systems with relay selection when operating over Nakagami-m fading channels. The derived MGF expression, which is valid for arbitrary values of the fading parameters of both hops, is subsequently utilized to evaluate the average symbol error probability (ASEP of M-ary phase shift keying modulation for the considered DF relaying scheme under various asymmetric fading conditions. It is shown that the MGF-based ASEP performance evaluation results are in excellent agreement with equivalent ones obtained by means of computer simulations, thus validating the correctness of the presented MGF expression.
Efficient Cooperative Protocols for Full-Duplex Relaying over Nakagami-m Fading Channels
Khafagy, Mohammad Galal
2015-02-24
In this work, efficient protocols are studied for full-duplex relaying (FDR) with loopback interference over Nakagami-m block fading channels. Recently, a selective decodeand- forward (DF) protocol was proposed for FDR, and was shown to outperform existing protocols in terms of outage over Rayleigh-fading channels. In this work, we propose an incremental selective DF protocol that offers additional power savings, yet yields the same outage performance. We evaluate their outage performance over independent non-identically distributed Nakagami-m fading links, and study their relative performance in terms of the signal-to-noise ratio cumulative distribution function via closed-form expressions. The offered diversity gain is also derived. In addition, we study their performance relative to their half-duplex counterparts, as well as known non-selective FDR protocols. We corroborate our theoretical results with simulation, and confirm that selective cooperation protocols outperform the known non-selective protocols in terms of outage. Finally, we show that depending on the loopback interference level, the proposed protocols can outperform their half-duplex counterparts when high spectral efficiencies are targeted.
Efficient Cooperative Protocols for Full-Duplex Relaying over Nakagami-m Fading Channels
Khafagy, Mohammad Galal; Tammam, Amr; Alouini, Mohamed-Slim; Aissa, Sonia
2015-01-01
In this work, efficient protocols are studied for full-duplex relaying (FDR) with loopback interference over Nakagami-m block fading channels. Recently, a selective decodeand- forward (DF) protocol was proposed for FDR, and was shown to outperform existing protocols in terms of outage over Rayleigh-fading channels. In this work, we propose an incremental selective DF protocol that offers additional power savings, yet yields the same outage performance. We evaluate their outage performance over independent non-identically distributed Nakagami-m fading links, and study their relative performance in terms of the signal-to-noise ratio cumulative distribution function via closed-form expressions. The offered diversity gain is also derived. In addition, we study their performance relative to their half-duplex counterparts, as well as known non-selective FDR protocols. We corroborate our theoretical results with simulation, and confirm that selective cooperation protocols outperform the known non-selective protocols in terms of outage. Finally, we show that depending on the loopback interference level, the proposed protocols can outperform their half-duplex counterparts when high spectral efficiencies are targeted.
Performance Analysis of Iterative Decoding Algorithms for PEG LDPC Codes in Nakagami Fading Channels
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O. Al Rasheed
2013-11-01
Full Text Available In this paper we give a comparative analysis of decoding algorithms of Low Density Parity Check (LDPC codes in a channel with the Nakagami distribution of the fading envelope. We consider the Progressive Edge-Growth (PEG method and Improved PEG method for the parity check matrix construction, which can be used to avoid short girths, small trapping sets and a high level of error floor. A comparative analysis of several classes of LDPC codes in various propagation conditions and decoded using different decoding algorithms is also presented.
Randrianantenaina, Itsikiantsoa
2015-01-01
In this work, the performance of multihop communication over Nakagami-m fading is investigated for both cases without and with diversity combining. Closed form expressions of the average ergodic capacity are derived for each of these cases. Then, an expression of the outage probability is obtained using the inverse of Laplace transform and the average bit error rate is bounded using the Moment-Generating-Function approach. The energy efficiency is analyzed using the "consumption factor" as a metric, and it is derived in closed-form. And based on the obtained expressions, we propose a power allocation strategy maximizing this consumption factor.
Product of the powers of generalized Nakagami-m variates and performance of cascaded fading channels
Yilmaz, Ferkan
2009-11-01
In this paper, we analyze the fading statistics of a generic fading distribution, termed the N-product Generalized Nakagami-m (GNM) distribution (N*GNM distribution), constructed as the product of the power of N statistically independent and non-identically distributed GNM random variables, for the purpose of modeling the cascaded fading channels. In particular, using the Fox\\'s H function, we derive the probability density function, the cumulative distribution function, the moment generating function and the moments of such channels in closed-form. These derived results are a convenient tool to statistically model the cascaded GNM fading channels and to analyze the performance of digital communication systems over these kinds of channels. As such, generic closed-form expressions for the amount of fading, the outage probability, the capacity, the outage capacity and the average bit error probabilities of digital communications systems over cascaded GNM fading channels are presented. Numerical and simulation results, performed to verify the correctness of the proposed formulation, are in perfect agreement.
Adaptive Modulation with Best User Selection over Non-Identical Nakagami Fading Channels
Rao, Anlei
2012-09-08
In this paper, we analyze the performance of adaptive modulation with single-cell multiuser scheduling over independent but not identical distributed (i.n.i.d.) Nakagami fading channels. Closed-form expressions are derived for the average channel capacity, spectral efficiency, and bit-error-rate (BER) for both constant-power variable-rate and variable-power variable-rate uncoded M-ary quadrature amplitude modulation (M-QAM) schemes. We also study the impact of time delay on the average BER of adaptive M-QAM. Selected numerical results show that the multiuser diversity brings a considerably better performance even over i.n.i.d. fading environments.
Rao, Anlei
2012-09-08
In this paper, we analyze the performance of adaptive modulation with single-cell multiuser scheduling over independent but not identical distributed (i.n.i.d.) Nakagami fading channels. Closed-form expressions are derived for the average channel capacity, spectral efficiency, and bit-error-rate (BER) for both constant-power variable-rate and variable-power variable-rate uncoded/coded M-ary quadrature amplitude modulation (M-QAM) schemes. We also study the impact of time delay on the average BER of adaptive M-QAM. Selected numerical results show that the multiuser diversity brings a considerably better performance even over i.n.i.d. fading environments.
Distributed detection in UWB sensor networks under non-orthogonal Nakagami-m fading
Mehbodniya, Abolfazl
2011-09-01
Several attractive features of ultra wideband (UWB) communications make it a good candidate for physical-layer of wireless sensor networks (WSN). These features include low power consumption, low complexity and low cost of implementation. In this paper, we present an opportunistic power assignment strategy for distributed detection in parallel fusion WSNs, considering a Nakagami-m fading model for the communication channel and time-hopping (TH) UWB for the transmitter circuit of the sensor nodes. In a parallel fusion WSN, local decisions are made by local sensors and transmitted through wireless channels to a fusion center. The fusion center processes the information and makes the final decision. Simulation results are provided for the global probability of detection error and relative performance gain to evaluate the efficiency of the proposed power assignment strategy in different fading environments. © 2011 IEEE.
Bit Error Rate Analysis for MC-CDMA Systems in Nakagami- Fading Channels
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Li Zexian
2004-01-01
Full Text Available Multicarrier code division multiple access (MC-CDMA is a promising technique that combines orthogonal frequency division multiplexing (OFDM with CDMA. In this paper, based on an alternative expression for the -function, characteristic function and Gaussian approximation, we present a new practical technique for determining the bit error rate (BER of multiuser MC-CDMA systems in frequency-selective Nakagami- fading channels. The results are applicable to systems employing coherent demodulation with maximal ratio combining (MRC or equal gain combining (EGC. The analysis assumes that different subcarriers experience independent fading channels, which are not necessarily identically distributed. The final average BER is expressed in the form of a single finite range integral and an integrand composed of tabulated functions which can be easily computed numerically. The accuracy of the proposed approach is demonstrated with computer simulations.
Capacity of spectrum sharing Cognitive Radio systems over Nakagami fading channels at low SNR
Sboui, Lokman
2013-06-01
In this paper, we study the ergodic capacity of Cognitive Radio (CR) spectrum sharing systems at low power regime. We focus on Nakagami fading channels. We formally define the low power regime and present closed form expressions of the capacity in the low power regime under various types of interference and/or power constraints, depending on the available channel state information (CSI) of the cross link (CL) between the secondary user transmitter and the primary user receiver. We explicitly characterize two regimes where either the interference constraint or the power constraint dictates the optimal power profile. Our framework also highlights the effects of different fading parameters on the secondary link ergodic capacity. Interestingly, we show that the low power regime analysis provides a specific insight on the capacity behavior of CR that has not been reported by previous studies. © 2013 IEEE.
BER EVALUATION OF LDPC CODES WITH GMSK IN NAKAGAMI FADING CHANNEL
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Surbhi Sharma
2010-06-01
Full Text Available LDPC codes (Low Density Parity Check Codes have already proved its efficacy while showing its performance near to the Shannon limit. Channel coding schemes are spectrally inefficient as using an unfiltered binary data stream to modulate an RF carrier that will produce an RF spectrum of considerable bandwidth. Techniques have been developed to improve this bandwidth inefficiency or spectral efficiency, and ease detection. GMSK or Gaussian-filtered Minimum Shift Keying uses a Gaussian Filter of an appropriate bandwidth so as to make system spectrally efficient. A Nakagami model provides a better explanation to less and more severe conditions than the Rayleigh and Rician model and provide a better fit to the mobile communication channel data. In this paper we have demonstrated the performance of Low Density Parity Check codes with GMSK modulation (BT product=0.25 technique in Nakagami fading channel. In results it is shown that average bit error rate decreases as the ‘m’ parameter increases (Less fading.
On the capacity of nakagami-m fading Channels with full channel state information at low SNR
Rezki, Zouheir
2012-06-01
The capacity of flat Rayleigh fading channels with full channel state information (CSI) at the transmitter and at the receiver at asymptotically low SNR has been recently shown to scale essentially as SNR log(1/SNR)}. In this paper, we investigate the Nakagami-m fading channel capacity with full CSI, and show that the capacity of this channel scales essentially as m/ Omega SNR log(1/SNR), where m is the Nakagami-m fading parameter and where Ω is the channel mean-square. We also show that one-bit CSI at the transmitter is enough to achieve this asymptotic capacity using an On-Off power control scheme. Our framework may be seen as a generalization of previous works as it captures the Rayleigh fading channel as a special case by taking m=1. © 2012 IEEE.
Xia, Minghua; Xing, Chengwen; Wu, Yik-Chung; Aissa, Sonia
2011-01-01
Relay transmission is promising for future wireless systems due to its significant cooperative diversity gain. The performance of dual-hop semi-blind amplify-and-forward (AF) relaying systems was extensively investigated, for transmissions over Rayleigh fading channels or Nakagami-𝑚 fading channels with integer fading parameter. For the general Nakagami-𝑚 fading with arbitrary 𝑚 values, the exact closed-form system performance analysis is more challenging. In this paper, we explicitly derive the moment generation function (MGF), probability density function (PDF) and moments of the end-to-end signal-to-noise ratio (SNR) over arbitrary Nakagami-𝑚 fading channels with semi-blind AF relay. With these results, the system performance evaluation in terms of outage probability, average symbol error probability, ergodic capacity and diversity order, is conducted. The analysis developed in this paper applies to any semi-blind AF relaying systems with fixed relay gain, and two major strategies for computing the relay gain are compared in terms of system performance. All analytical results are corroborated by simulation results and they are shown to be efficient tools to evaluate system performance.
Xia, Minghua
2011-10-01
Relay transmission is promising for future wireless systems due to its significant cooperative diversity gain. The performance of dual-hop semi-blind amplify-and-forward (AF) relaying systems was extensively investigated, for transmissions over Rayleigh fading channels or Nakagami- fading channels with integer fading parameter. For the general Nakagami- fading with arbitrary values, the exact closed-form system performance analysis is more challenging. In this paper, we explicitly derive the moment generation function (MGF), probability density function (PDF) and moments of the end-to-end signal-to-noise ratio (SNR) over arbitrary Nakagami- fading channels with semi-blind AF relay. With these results, the system performance evaluation in terms of outage probability, average symbol error probability, ergodic capacity and diversity order, is conducted. The analysis developed in this paper applies to any semi-blind AF relaying systems with fixed relay gain, and two major strategies for computing the relay gain are compared in terms of system performance. All analytical results are corroborated by simulation results and they are shown to be efficient tools to evaluate system performance.
Consumption Factor Optimization for Multihop Relaying over Nakagami-m Fading channels
Randrianantenaina, Itsikiantsoa
2015-10-06
In this paper, the energy efficiency of multihop relaying over Nakagami-m fading channels is investigated. The “consumption factor”, adopted as a metric to evaluate the energy efficiency, is derived for both amplify-and-forward and decodeand- forward relaying strategies. Then, based on the obtained expressions, we propose a power allocation strategy maximizing the consumption factor. In addition, a sub-optimal, low complexity, power allocation algorithm is proposed and analyzed, and the obtained power allocation scheme is compared in terms of energy efficiency to other power allocation schemes from the literature. Analytical and simulation results confirm the accuracy of our derivations, and assess the performance gains of the proposed approach.
Transmit power optimization for green multihop relaying over Nakagami-m fading channels
Randrianantenaina, Itsikiantsoa
2014-03-01
In this paper, we investigate the optimal transmit power strategy to maximize the energy efficiency of a multihop relaying network. Considering the communication between a source and a destination through multiple Amplify-and-Forward relays, we first give the expression of the total instantaneous system energy consumption. Then, we define the energy efficiency in our context and obtain its expression in closed-form when the communication is over Nakagami-m fading channels. The analysis yields to the derivation of a global transmit power strategy where each individual node is contributing to the end-to-end overall energy efficiency. Numercial results are presented to illustrate the analysis. Comparison with Monte Carlo simulation results confirms the accuracy of our derivations, and assesses the gains of the proposed power optimization strategy. © 2014 IEEE.
Asymptotic analysis for Nakagami-m fading channels with relay selection
Zhong, Caijun
2011-06-01
In this paper, we analyze the asymptotic outage probability performance of both decode-and-forward (DF) and amplify-and-forward (AF) relaying systems using partial relay selection and the "best" relay selection schemes for Nakagami-m fading channels. We derive their respective outage probability expressions in the asymptotic high signal-to-noise ratio (SNR) regime, from which the diversity order and coding gain are analyzed. In addition, we investigate the impact of power allocation between the source and relay terminals and derive the diversity-multiplexing tradeoff (DMT) for these relay selection systems. The theoretical findings suggest that partial relay selection can improve the diversity of the system and can achieve the same DMT as the "best" relay selection scheme under certain conditions. © 2011 IEEE.
Consumption Factor Optimization for Multihop Relaying over Nakagami-m Fading channels
Randrianantenaina, Itsikiantsoa; Benjillali, Mustapha; Alouini, Mohamed-Slim
2015-01-01
In this paper, the energy efficiency of multihop relaying over Nakagami-m fading channels is investigated. The “consumption factor”, adopted as a metric to evaluate the energy efficiency, is derived for both amplify-and-forward and decodeand- forward relaying strategies. Then, based on the obtained expressions, we propose a power allocation strategy maximizing the consumption factor. In addition, a sub-optimal, low complexity, power allocation algorithm is proposed and analyzed, and the obtained power allocation scheme is compared in terms of energy efficiency to other power allocation schemes from the literature. Analytical and simulation results confirm the accuracy of our derivations, and assess the performance gains of the proposed approach.
Transmit power optimization for green multihop relaying over Nakagami-m fading channels
Randrianantenaina, Itsikiantsoa; Benjillali, Mustapha; Alouini, Mohamed-Slim
2014-01-01
In this paper, we investigate the optimal transmit power strategy to maximize the energy efficiency of a multihop relaying network. Considering the communication between a source and a destination through multiple Amplify-and-Forward relays, we first give the expression of the total instantaneous system energy consumption. Then, we define the energy efficiency in our context and obtain its expression in closed-form when the communication is over Nakagami-m fading channels. The analysis yields to the derivation of a global transmit power strategy where each individual node is contributing to the end-to-end overall energy efficiency. Numercial results are presented to illustrate the analysis. Comparison with Monte Carlo simulation results confirms the accuracy of our derivations, and assesses the gains of the proposed power optimization strategy. © 2014 IEEE.
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Yang Lie-Liang
2005-01-01
Full Text Available In this contribution, the performance of wideband code-division multiple-access (W-CDMA systems using space-time-spreading- (STS- based transmit diversity is investigated, when frequency-selective Nakagami- fading channels, multiuser interference, and background noise are considered. The analysis and numerical results suggest that the achievable diversity order is the product of the frequency-selective diversity order and the transmit diversity order. Furthermore, both the transmit diversity and the frequency-selective diversity have the same order of importance. Since W-CDMA signals are subjected to frequency-selective fading, the number of resolvable paths at the receiver may vary over a wide range depending on the transmission environment encountered. It can be shown that, for wireless channels where the frequency selectivity is sufficiently high, transmit diversity may be not necessitated. Under this case, multiple transmission antennas can be leveraged into an increased bitrate. Therefore, an adaptive STS-based transmission scheme is then proposed for improving the throughput of W-CDMA systems. Our numerical results demonstrate that this adaptive STS-based transmission scheme is capable of significantly improving the effective throughput of W-CDMA systems. Specifically, the studied W-CDMA system's bitrate can be increased by a factor of three at the modest cost of requiring an extra 0.4 dB or 1.2 dB transmitted power in the context of the investigated urban or suburban areas, respectively.
Full-Duplex Relaying with Improper Gaussian Signaling over Nakagami-m Fading Channels
Gaafar, Mohamed
2017-10-04
We study the potential employment of improper Gaussian signaling (IGS) in full-duplex relaying (FDR) with non-negligible residual self-interference (RSI) under Nakagami- m fading. IGS is recently shown to outperform traditional proper Gaussian signaling (PGS) in several interference-limited settings. In this work, IGS is employed as an attempt to alleviate RSI. We use two performance metrics, namely, the outage probability and the ergodic rate. First, we provide upper and lower bounds for the system performance in terms of the relay transmit power and circularity coefficient, a measure of the signal impropriety. Then, we numerically optimize the relay signal parameters based only on the channel statistics to improve the system performance. Based on the analysis, IGS allows FDR to operate even with high RSI. The results show that IGS can leverage higher power budgets to enhance the performance, meanwhile it relieves RSI impact via tuning the signal impropriety. Interestingly, one-dimensional optimization of the circularity coefficient, with maximum relay power, offers a similar performance as the joint optimization, which reduces the optimization complexity. From a throughput standpoint, it is shown that IGS-FDR can outperform not only PGS-FDR, but also half-duplex relaying with/without maximum ratio combining over certain regions of the target source rate.
Randrianantenaina, Itsikiantsoa
2015-06-01
The concept of multihop communications (where the source communicates with the destination via many intermediate nodes) has been revisited and adapted to mitigate wireless channel impairments and ensure broader coverage. It has been shown in the literature that, in addition to extending coverage, overcoming shadowing and reducing the transmit power, multihop communications can increase the capacity of the network at a low additional cost. On the other hand, the problem of energy efficiency is one of the current biggest challenges towards green radio communications. Morevover, electromagnetic radiation is at its limit in many contexts, while for battery-powered devices, transmit and circuit energy consumption has to be minimized for better battery lifetime and performance. In this work, the performance of multihop communication over Nakagami-m fading is investigated for both cases without and with diversity combining. Closed form expressions of the average ergodic capacity are derived for each of these cases. Then, an expression of the outage probability is obtained using the inverse of Laplace transform and the average bit error rate is bounded using the Moment-Generating-Function approach. The energy efficiency is analyzed using the "consumption factor" as a metric, and it is derived in closed-form. And based on the obtained expressions, we propose a power allocation strategy maximizing this consumption factor.
Delay performance of a broadcast spectrum sharing network in Nakagami-m fading
Khan, Fahd Ahmed
2014-03-01
In this paper, we analyze the delay performance of a point-to-multipoint secondary network (P2M-SN), which is concurrently sharing the spectrum with a point-to-multipoint primary network (P2M-PN). The channel is assumed to be independent but not identically distributed (i.n.i.d.) and has Nakagami-m fading. A constraint on the peak transmit power of the secondary-user transmitter (SU-Tx) is considered, in addition to the peak interference power constraint. The SU-Tx is assumed to be equipped with a buffer and is modeled using the M/G/1 queueing model. The performance of this system is analyzed for two scenarios: 1) P2M-SN does not experience interference from the primary network (denoted by P2M-SN-NI), and 2) P2M-SN does experience interference from the primary network (denoted by P2M-SN-WI). The performance of both P2M-SN-NI and P2M-SN-WI is analyzed in terms of the packet transmission time, and the closed-form cumulative density function (cdf) of the packet transmission time is derived for both scenarios. Furthermore, by utilizing the concept of timeout, an exact closed-form expression for the outage probability of the P2M-SN-NI is obtained. In addition, an accurate approximation for the outage probability of the P2M-SN-WI is also derived. Furthermore, for the P2M-SN-NI, the analytic expressions for the total average waiting time (TAW-time) of packets and the average number of packets waiting in the buffer of the SU-Tx are also derived. Numerical simulations are also performed to validate the derived analytical results. © 1967-2012 IEEE.
A Unified Approach to the Analysis of Multicarrier DS-CDMA over Nakagami-$M$ Fading Channels
Yang, L-L.; Hanzo, L.
2001-01-01
A class of unified multicarrier DS-CDMA (MC DS-CDMA) schemes is defined and its performance is considered over multipath Nakagami-$M$ fading channels. The spacing between two adjacent subcarriers of the unified MC DS-CDMA scheme is a variable, allowing us to gain insight into the effects of the spacing on the bit error rate (BER) performance of MC DS-CDMA systems. This unified MC DS-CDMA scheme includes the subclasses of multitone DS-CDMA and orthogonal MC DS-CDMA as special cases. The optimu...
Exact Outage Probability of Dual-Hop CSI-Assisted AF Relaying Over Nakagami-m Fading Channels
Xia, Minghua
2012-10-01
In this correspondence, considering dual-hop channel state information (CSI)-assisted amplify-and-forward (AF) relaying over Nakagami- m fading channels, the cumulative distribution function (CDF) of the end-to-end signal-to-noise ratio (SNR) is derived. In particular, when the fading shape factors m1 and m2 at consecutive hops take non-integer values, the bivariate H-function and G -function are exploited to obtain an exact analytical expression for the CDF. The obtained CDF is then applied to evaluate the outage performance of the system under study. The analytical results of outage probability coincide exactly with Monte-Carlo simulation results and outperform the previously reported upper bounds in the low and medium SNR regions.
Benjillali, Mustapha; Hyadi, Amal; Da Costa, Daniel Benevides Da; Alouini, Mohamed-Slim
2013-01-01
In this work, we investigate the performance of cognitive multihop regenerative relaying systems in the "underlay" spectrum sharing scenario. The multiple relays perform "detect-and-forward" relaying strategy to convey a message with an order m quadrature amplitude modulation (m-QAM) from the source to the destination over independent but not necessarily identical Nakagami-m fading channels. We adopt a closed-form analysis framework based on univariate and bivariate Meijer G-functions to derive the end-to-end error performance (in terms of bit and symbol error rates), the outage probability, and the ergodic capacity. Various numerical examples are presented to illustrate the results with a large combination of system and fading parameters, and simulation results confirm the accuracy of our closed-form analysis. © 2013 IEEE.
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Kousa Maan
2005-01-01
Full Text Available The severity of fading on mobile communication channels calls for the combining of multiple diversity sources to achieve acceptable error rate performance. Traditional approaches perform the combining of the different diversity sources using either the conventional selective diversity combining (CSC, equal-gain combining (EGC, or maximal-ratio combining (MRC schemes. CSC and MRC are the two extremes of compromise between performance quality and complexity. Some researches have proposed a generalized selection combining scheme (GSC that combines the best branches out of the available diversity resources ( . In this paper, we analyze a generalized selection combining scheme based on a threshold criterion rather than a fixed-size subset of the best channels. In this scheme, only those diversity branches whose energy levels are above a specified threshold are combined. Closed-form analytical solutions for the BER performances of this scheme over Nakagami fading channels are derived. We also discuss the merits of this scheme over GSC.
Benjillali, Mustapha
2013-09-01
In this work, we investigate the performance of cognitive multihop regenerative relaying systems in the "underlay" spectrum sharing scenario. The multiple relays perform "detect-and-forward" relaying strategy to convey a message with an order m quadrature amplitude modulation (m-QAM) from the source to the destination over independent but not necessarily identical Nakagami-m fading channels. We adopt a closed-form analysis framework based on univariate and bivariate Meijer G-functions to derive the end-to-end error performance (in terms of bit and symbol error rates), the outage probability, and the ergodic capacity. Various numerical examples are presented to illustrate the results with a large combination of system and fading parameters, and simulation results confirm the accuracy of our closed-form analysis. © 2013 IEEE.
Aniba, Ghassane
2011-04-01
This paper presents an optimal adaptive modulation (AM) algorithm designed using a cross-layer approach which combines truncated automatic repeat request (ARQ) protocol and packet combining. Transmissions are performed over multiple-input multiple-output (MIMO) Nakagami fading channels, and retransmitted packets are not necessarily modulated using the same modulation format as in the initial transmission. Compared to traditional approach, cross-layer design based on the coupling across the physical and link layers, has proven to yield better performance in wireless communications. However, there is a lack for the performance analysis and evaluation of such design when the ARQ protocol is used in conjunction with packet combining. Indeed, previous works addressed the link layer performance of AM with truncated ARQ but without packet combining. In addition, previously proposed AM algorithms are not optimal and can provide poor performance when packet combining is implemented. Herein, we first show that the packet loss rate (PLR) resulting from the combining of packets modulated with different constellations can be well approximated by an exponential function. This model is then used in the design of an optimal AM algorithm for systems employing packet combining, truncated ARQ and MIMO antenna configurations, considering transmission over Nakagami fading channels. Numerical results are provided for operation with or without packet combining, and show the enhanced performance and efficiency of the proposed algorithm in comparison with existing ones. © 2011 IEEE.
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Hongji Huang
2017-01-01
Full Text Available This paper studies the relay selection schemes in mobile communication system over Nakagami-m channel. To make efficient use of licensed spectrum, both single relay selection (SRS scheme and multirelays selection (MRS scheme over the Nakagami-m channel are proposed. Also, the intercept probability (IP and outage probability (OP of the proposed SRS and MRS for the communication links depending on realistic spectrum sensing are derived. Furthermore, this paper assesses the manifestation of conventional direct transmission scheme to compare with the proposed SRS and MRS ones based on the Nakagami-m channel, and the security-reliability trade-off (SRT performance of the proposed schemes and the conventional schemes is well investigated. Additionally, the SRT of the proposed SRS and MRS schemes is demonstrated better than that of direct transmission scheme over the Nakagami-m channel, which can protect the communication transmissions against eavesdropping attacks. Additionally, simulation results show that our proposed relay selection schemes achieve better SRT performance than that of conventional direct transmission over the Nakagami-m channel.
Nam, Sung Sik; Ko, Young-Chai; Alouini, Mohamed-Slim
2017-01-01
in the literature. In addition, as a feasible application example in which our new offered derived closed-form results can be applied is presented. In particular, we analyze the outage performance of the finger replacement schemes over Nakagami fading channels
Xia, Minghua
2012-06-01
Since the electromagnetic spectrum resource becomes more and more scarce, improving spectral efficiency is extremely important for the sustainable development of wireless communication systems and services. Integrating cooperative relaying techniques into spectrum-sharing cognitive radio systems sheds new light on higher spectral efficiency. In this paper, we analyze the end-to-end performance of cooperative amplify-and-forward (AF) relaying in spectrum-sharing systems. In order to achieve the optimal end-to-end performance, the transmit powers of the secondary source and the relays are optimized with respect to average interference power constraints at primary users and Nakagami-$m$ fading parameters of interference channels (for mathematical tractability, the desired channels from secondary source to relay and from relay to secondary destination are assumed to be subject to Rayleigh fading). Also, both partial and opportunistic relay-selection strategies are exploited to further enhance system performance. Based on the exact distribution functions of the end-to-end signal-to-noise ratio (SNR) obtained herein, the outage probability, average symbol error probability, diversity order, and ergodic capacity of the system under study are analytically investigated. Our results show that system performance is dominated by the resource constraints and it improves slowly with increasing average SNR. Furthermore, larger Nakagami-m fading parameter on interference channels deteriorates system performance slightly. On the other hand, when interference power constraints are stringent, opportunistic relay selection can be exploited to improve system performance significantly. All analytical results are corroborated by simulation results and they are shown to be efficient tools for exact evaluation of system performance.
Performance of DS-UWB in MB-OFDM and multi-user interference over Nakagami-m fading channels
Mehbodniya, Abolfazl
2011-01-18
The mutual interference between the two ultra wideband (UWB) technologies, which use the same frequency spectrum, will be a matter of concern in the near future. In this context, we present a performance analysis of direct-sequence (DS) UWB communication in the presence of multiband orthogonal frequency division multiplexing (MB-OFDM) UWB interfering transmissions. The channel fading is modeled according to Nakagami-m distribution, and multi-user interference is taken into account. The DS-UWB system performance is evaluated in terms of bit error rate (BER). Specifically, using the characteristic function approach, an analytical expression for the average BER is derived conditioned on the channel impulse response. Numerical and simulation results are provided and compared for different coexistence scenarios. © 2011 John Wiley & Sons, Ltd.
A Simple Exact Error Rate Analysis for DS-CDMA with Arbitrary Pulse Shape in Flat Nakagami Fading
Rahman, Mohammad Azizur; Sasaki, Shigenobu; Kikuchi, Hisakazu; Harada, Hiroshi; Kato, Shuzo
A simple exact error rate analysis is presented for random binary direct sequence code division multiple access (DS-CDMA) considering a general pulse shape and flat Nakagami fading channel. First of all, a simple model is developed for the multiple access interference (MAI). Based on this, a simple exact expression of the characteristic function (CF) of MAI is developed in a straight forward manner. Finally, an exact expression of error rate is obtained following the CF method of error rate analysis. The exact error rate so obtained can be much easily evaluated as compared to the only reliable approximate error rate expression currently available, which is based on the Improved Gaussian Approximation (IGA).
National Research Council Canada - National Science Library
Kalogrias, Christos
2004-01-01
... 802.11a wireless local area network (WLAN) standard receiver when the signal is transmitted over a frequency selective, slow fading Nakagami channel in a worst case, pulse-noise jamming environment...
Lei, Hongjiang; Zhang, Huan; Ansari, Imran Shafique; Ren, Zhi; Pan, Gaofeng; Qaraqe, Khalid A.; Alouini, Mohamed-Slim
2017-01-01
In this paper, the secrecy outage performance of an underlay cognitive decode-and-forward relay network over independent but not necessarily identical distributed (i.n.i.d) Nakagami-m fading channels is investigated, in which the secondary user transmitter communicates with the secondary destination via relays, and an eavesdropper attempts to overhear the information. Based on whether the channel state information (CSI) of the wiretap links is available or not, we analyze the secrecy outage performance with optimal relay selection (ORS) and suboptimal relay selection (SRS) schemes, and multiple relays combining scheme (MRC) scheme is considered for comparison purpose. The exact and asymptotic closed-form expressions for the secrecy outage probability with three different relay selection schemes are derived and verified by Monte-Carlo simulations. The numerical results illustrate that ORS scheme always outperforms SRS and MRC schemes, and SRS scheme is better than MRC scheme in the lower fading parameters scenario. Furthermore, through asymptotic analysis, we find that these three different schemes achieve the same secrecy diversity order, which is determined by the number of the relays, and the fading parameters of the links among the relays and the destination.
Lei, Hongjiang
2017-10-02
In this paper, the secrecy outage performance of an underlay cognitive decode-and-forward relay network over independent but not necessarily identical distributed (i.n.i.d) Nakagami-m fading channels is investigated, in which the secondary user transmitter communicates with the secondary destination via relays, and an eavesdropper attempts to overhear the information. Based on whether the channel state information (CSI) of the wiretap links is available or not, we analyze the secrecy outage performance with optimal relay selection (ORS) and suboptimal relay selection (SRS) schemes, and multiple relays combining scheme (MRC) scheme is considered for comparison purpose. The exact and asymptotic closed-form expressions for the secrecy outage probability with three different relay selection schemes are derived and verified by Monte-Carlo simulations. The numerical results illustrate that ORS scheme always outperforms SRS and MRC schemes, and SRS scheme is better than MRC scheme in the lower fading parameters scenario. Furthermore, through asymptotic analysis, we find that these three different schemes achieve the same secrecy diversity order, which is determined by the number of the relays, and the fading parameters of the links among the relays and the destination.
Nam, Sung Sik
2017-06-19
Complex wireless transmission systems require multi-dimensional joint statistical techniques for performance evaluation. Here, we first present the exact closed-form results on order statistics of any arbitrary partial sums of Gamma random variables with the closedform results of core functions specialized for independent and identically distributed Nakagami-m fading channels based on a moment generating function-based unified analytical framework. These both exact closed-form results have never been published in the literature. In addition, as a feasible application example in which our new offered derived closed-form results can be applied is presented. In particular, we analyze the outage performance of the finger replacement schemes over Nakagami fading channels as an application of our method. Note that these analysis results are directly applicable to several applications, such as millimeter-wave communication systems in which an antenna diversity scheme operates using an finger replacement schemes-like combining scheme, and other fading scenarios. Note also that the statistical results can provide potential solutions for ordered statistics in any other research topics based on Gamma distributions or other advanced wireless communications research topics in the presence of Nakagami fading.
Product of the powers of generalized Nakagami-m variates and performance of cascaded fading channels
Yilmaz, Ferkan; Alouini, Mohamed-Slim
2009-01-01
-identically distributed GNM random variables, for the purpose of modeling the cascaded fading channels. In particular, using the Fox's H function, we derive the probability density function, the cumulative distribution function, the moment generating function
Benkhelifa, Fatma
2013-09-01
The effective capacity have been introduced by Wu and Neji as a link-layer model supporting statistical delay QoS requirements. In this paper, we propose to study the effective capacity of a Nakagami-m fading channel with full channel state information (CSI) at both the transmitter and at the receiver. We focus on the low Signal-to-Noise Ratio (SNR) regime. We show that the effective capacity for any arbitrary but finite statistically delay Quality of Service (QoS) exponent θ, scales essentially as S NRlog(1/SNR) exactly as the ergodic capacity, independently of any QoS constraint. We also characterize the minimum energy required for reliable communication, and the wideband slope to show that our results are in agreement with results established recently by Gursoy et al. We also propose an on-off power control scheme that achieves the capacity asymptotically using only one bit CSI feedback at the transmitter. Finally, some numerical results are presented to show the accuracy of our asymptotic results. © 2013 IEEE.
Enhancing the efficiency of constrained dual-hop variable-gain AF relaying under nakagami-m fading
Zafar, Ammar
2014-07-01
This paper studies power allocation for performance constrained dual-hop variable-gain amplify-and-forward (AF) relay networks in Nakagami- $m$ fading. In this context, the performance constraint is formulated as a constraint on the end-to-end signal-to-noise-ratio (SNR) and the overall power consumed is minimized while maintaining this constraint. This problem is considered under two different assumptions of the available channel state information (CSI) at the relays, namely full CSI at the relays and partial CSI at the relays. In addition to the power minimization problem, we also consider the end-to-end SNR maximization problem under a total power constraint for the partial CSI case. We provide closed-form solutions for all the problems which are easy to implement except in two cases, namely selective relaying with partial CSI for power minimization and SNR maximization, where we give the solution in the form of a one-variable equation which can be solved efficiently. Numerical results are then provided to characterize the performance of the proposed power allocation algorithms considering the effects of channel parameters and CSI availability. © 2014 IEEE.
Outage performance of reactive cooperation in Nakagami-m fading channels
Benjillali, Mustapha
2010-06-01
In this paper, we investigate the outage performance of Decode-and-Forward with reactive relaying in dual-hop cooperetive Nakagaml-m fading links. The destination, based on the umque knowledge of local second hop channel state information, selects the best relay to increase the chances of cooperation when the direct link is also available. After deriving the exact distribution of the variables of interest, the outage probability of the system - with and without the direct link - is obtained in closed-form, and the ε-outage capacity is derived in the particular c.se wh.ere the channel model is reduced to a Rayleigh fading. Simulation results confirm the accuracy of our analysis for a large selection of system and fading parameters.
Outage performance of reactive cooperation in Nakagami-m fading channels
Benjillali, Mustapha; Alouini, Mohamed-Slim
2010-01-01
In this paper, we investigate the outage performance of Decode-and-Forward with reactive relaying in dual-hop cooperetive Nakagaml-m fading links. The destination, based on the umque knowledge of local second hop channel state information, selects
Ansari, Imran Shafique
2012-09-08
The probability distribution function (PDF) and cumulative density function of the sum of L independent but not necessarily identically distributed gamma variates, applicable to maximal ratio combining receiver outputs or in other words applicable to the performance analysis of diversity combining receivers operating over Nakagami-m fading channels, is presented in closed form in terms of Meijer G-function and Fox H-bar-function for integer valued fading parameters and non-integer valued fading parameters, respectively. Further analysis, particularly on bit error rate via PDF-based approach, too is represented in closed form in terms of Meijer G-function and Fox H-bar-function for integer-order fading parameters, and extended Fox H-bar-function (H-hat) for non-integer-order fading parameters. The proposed results complement previous results that are either evolved in closed-form, or expressed in terms of infinite sums or higher order derivatives of the fading parameter m.
Ansari, Imran Shafique; Yilmaz, Ferkan; Alouini, Mohamed-Slim; Kucur, Oguz
2012-01-01
The probability distribution function (PDF) and cumulative density function of the sum of L independent but not necessarily identically distributed gamma variates, applicable to maximal ratio combining receiver outputs or in other words applicable to the performance analysis of diversity combining receivers operating over Nakagami-m fading channels, is presented in closed form in terms of Meijer G-function and Fox H-bar-function for integer valued fading parameters and non-integer valued fading parameters, respectively. Further analysis, particularly on bit error rate via PDF-based approach, too is represented in closed form in terms of Meijer G-function and Fox H-bar-function for integer-order fading parameters, and extended Fox H-bar-function (H-hat) for non-integer-order fading parameters. The proposed results complement previous results that are either evolved in closed-form, or expressed in terms of infinite sums or higher order derivatives of the fading parameter m.
Directory of Open Access Journals (Sweden)
T.-T. Phu
2016-12-01
Full Text Available In this paper, we evaluate probability of non-zero secrecy capacity of multi-hop relay networks over Nakagami-m fading channels in presence of hardware impairments. In the considered protocol, a source attempts to transmit its data to a destination by using multi-hop randomize-and-forward (RF strategy. The data transmitted by the source and relays are overheard by an eavesdropper. For performance evaluation, we derive exact expressions of probability of non-zero secrecy capacity (PoNSC, which are expressed by sums of infinite series of exponential functions and exponential integral functions. We then perform Monte Carlo simulations to verify the theoretical analysis.
Multivariate η-μ fading distribution with arbitrary correlation model
Ghareeb, Ibrahim; Atiani, Amani
2018-03-01
An extensive analysis for the multivariate ? distribution with arbitrary correlation is presented, where novel analytical expressions for the multivariate probability density function, cumulative distribution function and moment generating function (MGF) of arbitrarily correlated and not necessarily identically distributed ? power random variables are derived. Also, this paper provides exact-form expression for the MGF of the instantaneous signal-to-noise ratio at the combiner output in a diversity reception system with maximal-ratio combining and post-detection equal-gain combining operating in slow frequency nonselective arbitrarily correlated not necessarily identically distributed ?-fading channels. The average bit error probability of differentially detected quadrature phase shift keying signals with post-detection diversity reception system over arbitrarily correlated and not necessarily identical fading parameters ?-fading channels is determined by using the MGF-based approach. The effect of fading correlation between diversity branches, fading severity parameters and diversity level is studied.
Ergodic Capacity for the SIMO Nakagami- Channel
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Vagenas EfstathiosD
2009-01-01
Full Text Available This paper presents closed-form expressions for the ergodic channel capacity of SIMO (single-input and multiple output wireless systems operating in a Nakagami- fading channel. As the performance of SIMO channel is closely related to the diversity combining techniques, we present closed-form expressions for the capacity of maximal ratio combining (MRC, equal gain combining (EGC, selection combining (SC, and switch and stay (SSC diversity systems operating in Nakagami- fading channels. Also, the ergodic capacity of a SIMO system in a Nakagami- fading channel without any diversity technique is derived. The latter scenario is further investigated for a large amount of receive antennas. Finally, numerical results are presented for illustration.
Duong Trung Q; Shin Hyundong; Hong Een-Kee
2007-01-01
We analyze the exact average symbol error probability (SEP) of binary and -ary signals with spatial diversity in Nakagami- (Hoyt) fading channels. The maximal-ratio combining and orthogonal space-time block coding are considered as diversity techniques for single-input multiple-output and multiple-input multiple-output systems, respectively. We obtain the average SEP in terms of the Lauricella multivariate hypergeometric function . The analysis is verified by comparing with Monte Carlo simu...
An MGF-based capacity analysis of equal gain combining over fading channels
Yilmaz, Ferkan
2010-09-01
Exact average capacity results for L-branch coherent equal-gain combining (EGC) in correlated and uncorrelated fading channels are not known. This paper develops a novel framework (approach) for capacity analysis of L-branch EGC in generalized fading channels. In addition, Gamma shadowed generalized Nakagami-m fading model is proposed in order to statistically model the fading environments in high frequencies such as 60 GHz and above. Some simulations are carried out and then the obtained results are accentuated by means of numerical analysis based on the proposed framework. Numerical and simulation results, performed to verify the correctness of the proposed framework, are in perfect agreement. ©2010 IEEE.
An MGF-based capacity analysis of equal gain combining over fading channels
Yilmaz, Ferkan; Alouini, Mohamed-Slim
2010-01-01
Exact average capacity results for L-branch coherent equal-gain combining (EGC) in correlated and uncorrelated fading channels are not known. This paper develops a novel framework (approach) for capacity analysis of L-branch EGC in generalized fading channels. In addition, Gamma shadowed generalized Nakagami-m fading model is proposed in order to statistically model the fading environments in high frequencies such as 60 GHz and above. Some simulations are carried out and then the obtained results are accentuated by means of numerical analysis based on the proposed framework. Numerical and simulation results, performed to verify the correctness of the proposed framework, are in perfect agreement. ©2010 IEEE.
Modeling cellular networks in fading environments with dominant specular components
Alammouri, Ahmad; Elsawy, Hesham; Salem, Ahmed Sultan; Di Renzo, Marco; Alouini, Mohamed-Slim
2016-01-01
to the Nakagami-m fading in some special cases. However, neither the Rayleigh nor the Nakagami-m accounts for dominant specular components (DSCs) which may appear in realistic fading channels. In this paper, we present a tractable model for cellular networks
Modeling cellular networks in fading environments with dominant specular components
AlAmmouri, Ahmad
2016-07-26
Stochastic geometry (SG) has been widely accepted as a fundamental tool for modeling and analyzing cellular networks. However, the fading models used with SG analysis are mainly confined to the simplistic Rayleigh fading, which is extended to the Nakagami-m fading in some special cases. However, neither the Rayleigh nor the Nakagami-m accounts for dominant specular components (DSCs) which may appear in realistic fading channels. In this paper, we present a tractable model for cellular networks with generalized two-ray (GTR) fading channel. The GTR fading explicitly accounts for two DSCs in addition to the diffuse components and offers high flexibility to capture diverse fading channels that appear in realistic outdoor/indoor wireless communication scenarios. It also encompasses the famous Rayleigh and Rician fading as special cases. To this end, the prominent effect of DSCs is highlighted in terms of average spectral efficiency. © 2016 IEEE.
On the Ergodic Capacity of Dual-Branch Correlated Log-Normal Fading Channels with Applications
Al-Quwaiee, Hessa; Alouini, Mohamed-Slim
2015-01-01
Closed-form expressions of the ergodic capacity of independent or correlated diversity branches over Log-Normal fading channels are not available in the literature. Thus, it is become of an interest to investigate the behavior of such metric at high
SSC Diversity Receiver over Correlated Fading Channels in the Presence of Cochannel Interference
Directory of Open Access Journals (Sweden)
Panić StefanR
2010-01-01
Full Text Available This paper studies the performances of a dual-branch switched-and-stay combining (SSC diversity receiver, operating over correlated fading in the presence of cochannel interference (CCI. Very useful, novel, infinite series expressions are obtained for the output signal to interference ratio's (SIR's probability density function (PDF and cumulative distribution function (CDF. The performance analysis is based on an outage probability (OP and an average bit error probability (ASEP criteria. ASEP is efficiently evaluated for modulation schemes such as noncoherent frequency-shift keying (NCFSK and binary differentially phase-shift keying (BDPSK. The effects of various parameters, such as input SIR unbalance, the level of correlation between received desired signals and interferences, nonlinearity of the environment, and fading severity on systems performances are graphically presented and analyzed.
Al-Murad, Tamim M.
2010-06-01
In densely deployed sensor networks, correlation among measurements may be high. Spatial sampling through node selection is usually used to minimize this correlation and to save energy consumption. However because of the fading nature of the wireless channels, extra care should be taken when performing this sampling. In this paper, we develop expressions for the distortion which include the channel effects. The asymptotic behavior of the distortion as the number of sensors or total transmit power increase without bound is also investigated. Further, based on the channel and position information we propose and test several node selection schemes.
Al-Murad, Tamim M.
2011-07-01
Evaluating the reliability of wireless sensor networks is becoming more important as theses networks are being used in crucial applications. The outage probability defined as the probability that the error in the system exceeds a maximum acceptable threshold has recently been used as a measure of the reliability of such systems. In this work we find the outage probability of wireless sensor network in different scenarios of distributed sensing where sensors\\' readings are affected by spatial correlation and in the presence of channel fading. © 2011 IEEE.
Wang, Huiqin; Wang, Xue; Lynette, Kibe; Cao, Minghua
2018-06-01
The performance of multiple-input multiple-output wireless optical communication systems that adopt Q-ary pulse position modulation over spatial correlated log-normal fading channel is analyzed in terms of its un-coded bit error rate and ergodic channel capacity. The analysis is based on the Wilkinson's method which approximates the distribution of a sum of correlated log-normal random variables to a log-normal random variable. The analytical and simulation results corroborate the increment of correlation coefficients among sub-channels lead to system performance degradation. Moreover, the receiver diversity has better performance in resistance of spatial correlation caused channel fading.
On the Ergodic Capacity of Dual-Branch Correlated Log-Normal Fading Channels with Applications
Al-Quwaiee, Hessa
2015-05-01
Closed-form expressions of the ergodic capacity of independent or correlated diversity branches over Log-Normal fading channels are not available in the literature. Thus, it is become of an interest to investigate the behavior of such metric at high signal-to-noise (SNR). In this work, we propose simple closed-form asymptotic expressions of the ergodic capacity of dual-branch correlated Log- Normal corresponding to selection combining, and switch-and-stay combining. Furthermore, we capitalize on these new results to find new asymptotic ergodic capacity of correlated dual- branch free-space optical communication system under the impact of pointing error with both heterodyne and intensity modulation/direct detection. © 2015 IEEE.
On SIP Session setup delay for VoIP services over correlated fading channels
DEFF Research Database (Denmark)
Fathi, Hanane; Chakraborty, Shyam S.; Prasad, Ramjee
2006-01-01
In this paper, the session setup delay of the session initiation protocol (SIP) is studied. The transmissions on both the forward and reverse channel are assumed to experience Markovian errors. The session setup delay is evaluated for different transport protocols, and with the use of the radio...... link protocol (RLP). An adaptive retransmission timer is used to optimize SIP performances. Using numerical results, we find that SIP over user datagram protocol (UDP) instead of transport control protocol (TCP) can make the session setup up to 30% shorter. Also, RLP drastically reduces the session...... setup delay down to 4 to 5 s, even in environments with high frame error rates (10%) and significant correlation in the fading process (fDT=0.02). SIP is compared with its competitor H.323. SIP session setup delay with compressed messages outperforms H.323 session setup delay....
Directory of Open Access Journals (Sweden)
Giacomo Leonardi
2007-12-01
Full Text Available Ã¯Â»Â¿This paper investigates the impact of several equalization techniques for multicarrier code division multiple access systems on the performance at both lower and upper layers (i.e., physical and TCP layers. Classical techniques such as maximal ratio combining, equal gain combining, orthogonality restoring combining, minimum mean square error, as well as a partial equalization (PE are investigated in time- and frequency-correlated fading channels with various numbers of interferers. Their impact on the performance at upper level is then studied. The results are obtained through an integrated simulation platform carefully reproducing all main aspects affecting the quality of service perceived by the final user, allowing an investigation of the real gain produced by signal processing techniques at TCP level.
Energy-Efficient Optimization for HARQ Schemes over Time-Correlated Fading Channels
Shi, Zheng
2018-03-19
Energy efficiency of three common hybrid automatic repeat request (HARQ) schemes including Type I HARQ, HARQ with chase combining (HARQ-CC) and HARQ with incremental redundancy (HARQ-IR), is analyzed and joint power allocation and rate selection to maximize the energy efficiency is investigated in this paper. Unlike prior literature, time-correlated fading channels is considered and two widely concerned quality of service (QoS) constraints, i.e., outage and goodput constraints, are also considered in the optimization, which further differentiates this work from prior ones. Using a unified expression of asymptotic outage probabilities, optimal transmission powers and optimal rate are derived in closed-forms to maximize the energy efficiency while satisfying the QoS constraints. These closed-form solutions then enable a thorough analysis of the maximal energy efficiencies of various HARQ schemes. It is revealed that with low outage constraint, the maximal energy efficiency achieved by Type I HARQ is
Soury, Hamza
2013-07-01
This paper considers the average symbol error probability of square Quadrature Amplitude Modulation (QAM) coherent signaling over flat fading channels subject to additive generalized Gaussian noise. More specifically, a generic closedform expression in terms of the Fox H function and the bivariate Fox H function is offered for the extended generalized-K fading case. Simplifications for some special fading distributions such as generalized-K fading, Nakagami-m fading, and Rayleigh fading and special additive noise distributions such as Gaussian and Laplacian noise are then presented. Finally, the mathematical formalism is illustrated by some numerical examples verified by computer based simulations for a variety of fading and additive noise parameters.
Channel allocation and rate adaptation for relayed transmission over correlated fading channels
Hwang, Kyusung
2009-09-01
We consider, in this paper, channel allocation and rate adaptation scheme for relayed transmission over correlated fading channels via cross-layer design. Specifically, jointly considering the data link layer buffer occupancy and channel quality at both the source and relay nodes, we develop an optimal channel allocation and rate adaptation policy for a dual-hop relayed transmission. As such the overall transmit power for the relayed system is minimized while a target packet dropping rate (PDR) due to buffer over flows is guaranteed. In order to find such an optimal policy, the channel allocation and rate adaptation transmission framework is formulated as a constraint Markov decision process (CMDP). The PDR performance of the optimal policy is compared with that of two conventional suboptimal schemes, namely the channel quality based and the buffer occupancy based channel allocation schemes. Numerical results show that for a given power budget, the optimal scheme requires significantly less power than the conventional schemes in order to maintain a target PDR. ©2009 IEEE.
Yahampath, Pradeepa
2017-12-01
Consider communicating a correlated Gaussian source over a Rayleigh fading channel with no knowledge of the channel signal-to-noise ratio (CSNR) at the transmitter. In this case, a digital system cannot be optimal for a range of CSNRs. Analog transmission however is optimal at all CSNRs, if the source and channel are memoryless and bandwidth matched. This paper presents new hybrid digital-analog (HDA) systems for sources with memory and channels with bandwidth expansion, which outperform both digital-only and analog-only systems over a wide range of CSNRs. The digital part is either a predictive quantizer or a transform code, used to achieve a coding gain. Analog part uses linear encoding to transmit the quantization error which improves the performance under CSNR variations. The hybrid encoder is optimized to achieve the minimum AMMSE (average minimum mean square error) over the CSNR distribution. To this end, analytical expressions are derived for the AMMSE of asymptotically optimal systems. It is shown that the outage CSNR of the channel code and the analog-digital power allocation must be jointly optimized to achieve the minimum AMMSE. In the case of HDA predictive quantization, a simple algorithm is presented to solve the optimization problem. Experimental results are presented for both Gauss-Markov sources and speech signals.
Statistics for Ratios of Rayleigh, Rician, Nakagami-m, and Weibull Distributed Random Variables
Directory of Open Access Journals (Sweden)
Dragana Č. Pavlović
2013-01-01
Full Text Available The distributions of ratios of random variables are of interest in many areas of the sciences. In this brief paper, we present the joint probability density function (PDF and PDF of maximum of ratios μ1=R1/r1 and μ2=R2/r2 for the cases where R1, R2, r1, and r2 are Rayleigh, Rician, Nakagami-m, and Weibull distributed random variables. Random variables R1 and R2, as well as random variables r1 and r2, are correlated. Ascertaining on the suitability of the Weibull distribution to describe fading in both indoor and outdoor environments, special attention is dedicated to the case of Weibull random variables. For this case, analytical expressions for the joint PDF, PDF of maximum, PDF of minimum, and product moments of arbitrary number of ratios μi=Ri/ri, i=1,…,L are obtained. Random variables in numerator, Ri, as well as random variables in denominator, ri, are exponentially correlated. To the best of the authors' knowledge, analytical expressions for the PDF of minimum and product moments of {μi}i=1L are novel in the open technical literature. The proposed mathematical analysis is complemented by various numerical results. An application of presented theoretical results is illustrated with respect to performance assessment of wireless systems.
Cooperative Cognitive Radio Systems over Nakagami-m Fading Channels
Hyadi, Amal
2013-01-01
. Using cooperation in a cognitive set up make the use of spectrum much more efficient. Moreover, it helps to extend the coverage area of the cognitive network and also to reduce the transmitting power and, thus, the generated interference. In this work
Soury, Hamza
2012-06-01
This letter considers the average bit error probability of binary coherent signaling over flat fading channels subject to additive generalized Gaussian noise. More specifically, a generic closed form expression in terms of the Fox\\'s H function is offered for the extended generalized-K fading case. Simplifications for some special fading distributions such as generalized-K fading and Nakagami-m fading and special additive noise distributions such as Gaussian and Laplacian noise are then presented. Finally, the mathematical formalism is illustrated by some numerical examples verified by computer based simulations for a variety of fading and additive noise parameters. © 2012 IEEE.
Zorgui, Marwen
2015-06-14
We consider secret-key agreement with public discussion over multiple-input multiple-output (MIMO) Rayleigh fast-fading channels under correlated environment. We assume that transmit, legitimate receiver and eavesdropper antennas are correlated. The legitimate receiver and the eavesdropper are assumed to have perfect channel knowledge while the transmitter has only knowledge of the correlation matrices. First, we derive the expression of the secret-key capacity under the considered setup. Then, we prove that the optimal transmit strategy achieving the secret-key capacity consists in transmitting independent Gaussian signals along the eingenvectors of the transmit correlation matrix. The powers allocated to each channel mode are determined as the solution to a numerical optimization problem that we derive. A necessary and sufficient condition for beamforming (i.e., transmitting along the strongest channel mode) to be capacity-achieving is derived. Finally, we analyze the impact of correlation matrices on the system performance and provide closed-form expressions of the gain/loss due to correlation in the high power regime.
Directory of Open Access Journals (Sweden)
Srinivas Nallagonda
2016-04-01
Full Text Available In this paper we evaluate the performance of cooperative spectrum sensing (CSS where each cognitive radio (CR employs an improved energy detector (IED with multiple antennas and uses selection combining (SC for detecting the primary user (PU in noisy and faded sensing (S channels. We derive an expression for the probability of false alarm and expressions for probability of missed detection in non-faded (AWGN and Rayleigh faded sensing environments in terms of cumulative distribution function (CDF. Each CR transmits its decision about PU via noisy and faded reporting (R channel to fusion center (FC. In this paper we assume that S-channels are noisy and Rayleigh faded while several cases of fading are considered for R-channels such as: (i Hoyt (or Nakagami-q, (ii Rayleigh, (iii Rician (or Nakagami-n, and (iv Weibull. A Binary Symmetric channel (BSC with a fixed error probability (r in the R-channel is also considered. The impact of fading in R-channel, S-channel and several network parameters such as IED parameter, normalized detection threshold, number of CRs, and number of antennas on missed detection and total error probability is assessed. The effects of Hoyt, Rician, and Weibull fading parameters on overall performance of IED-CSS are also highlighted.
Effect of ultrasound frequency on the Nakagami statistics of human liver tissues.
Directory of Open Access Journals (Sweden)
Po-Hsiang Tsui
Full Text Available The analysis of the backscattered statistics using the Nakagami parameter is an emerging ultrasound technique for assessing hepatic steatosis and fibrosis. Previous studies indicated that the echo amplitude distribution of a normal liver follows the Rayleigh distribution (the Nakagami parameter m is close to 1. However, using different frequencies may change the backscattered statistics of normal livers. This study explored the frequency dependence of the backscattered statistics in human livers and then discussed the sources of ultrasound scattering in the liver. A total of 30 healthy participants were enrolled to undergo a standard care ultrasound examination on the liver, which is a natural model containing diffuse and coherent scatterers. The liver of each volunteer was scanned from the right intercostal view to obtain image raw data at different central frequencies ranging from 2 to 3.5 MHz. Phantoms with diffuse scatterers only were also made to perform ultrasound scanning using the same protocol for comparisons with clinical data. The Nakagami parameter-frequency correlation was evaluated using Pearson correlation analysis. The median and interquartile range of the Nakagami parameter obtained from livers was 1.00 (0.98-1.05 for 2 MHz, 0.93 (0.89-0.98 for 2.3 MHz, 0.87 (0.84-0.92 for 2.5 MHz, 0.82 (0.77-0.88 for 3.3 MHz, and 0.81 (0.76-0.88 for 3.5 MHz. The Nakagami parameter decreased with the increasing central frequency (r = -0.67, p < 0.0001. However, the effect of ultrasound frequency on the statistical distribution of the backscattered envelopes was not found in the phantom results (r = -0.147, p = 0.0727. The current results demonstrated that the backscattered statistics of normal livers is frequency-dependent. Moreover, the coherent scatterers may be the primary factor to dominate the frequency dependence of the backscattered statistics in a liver.
Performance of Narrowband Signal Detection under Correlated Rayleigh Fading Based on Synthetic Array
Directory of Open Access Journals (Sweden)
Ali Broumandan
2009-01-01
design parameters of probability of detection (Pd and probability of false alarm (Pfa. An optimum detector based on Estimator-Correlator (EC is developed, and its performance is compared with that of suboptimal Equal-Gain (EG combiner in different channel correlation scenarios. It is shown that in moderate channel correlation scenarios the detection performance of EC and EG is identical. The sensitivity of the proposed method to knowledge of motion parameters is also investigated. An extensive set of measurements based on CDMA-2000 pilot signals using the static antenna and synthetic array are used to experimentally verify these theoretical findings.
A unified MGF-based capacity analysis of diversity combiners over generalized fading channels
Yilmaz, Ferkan
2012-03-01
Unified exact ergodic capacity results for L-branch coherent diversity combiners including equal-gain combining (EGC) and maximal-ratio combining (MRC) are not known. This paper develops a novel generic framework for the capacity analysis of L-branch EGC/MRC over generalized fading channels. The framework is used to derive new results for the gamma-shadowed generalized Nakagami-m fading model which can be a suitable model for the fading environments encountered by high frequency (60 GHz and above) communications. The mathematical formalism is illustrated with some selected numerical and simulation results confirming the correctness of our newly proposed framework. © 2012 IEEE.
Sio, Betsy Menson
2009-01-01
A sky fading from blue to white to red at the horizon, and water darkening from light to midnight blue. Strong diagonals slashing through the image, drawing a viewer's eyes deeper into the picture, and delicate trees poised to convey a sense of beauty. These are the fascinating strengths of the ukiyo-e woodblock prints of Japanese artist Ando…
Frequency and spatial correlation functions in a fading communication channel through the ionosphere
International Nuclear Information System (INIS)
Liu, C.H.; Yeh, K.C.
1975-01-01
Equations for the two-frequency two-position mutual coherence functions are derived under the usual parabolic and Markov approximations. These equations are then solved numerically. It is shown that the mutual coherence functions occur naturally in the study of pulse distortion through a random communication channel and in the investigation of signal correlations. Contour plots of correlation functions show the possibility of having equal values at two frequency separations for a given spatial separation. This behavior is explainable in terms of overlapping Fresnel zones
Directory of Open Access Journals (Sweden)
G. Armbrecht
2007-06-01
Full Text Available Starting from planar broadband log.-per. antenna design, offering the possibility of dual-polarized reception properties, in this article a generalized mathematical approach for rapidly estimating the resulting signal correlation coefficient in a stochastically modeled propagation environment solely based on measured or simulated radiation characteristics of one single antenna element is presented. The obtained results are marking an upper limit and are describing the worst-case scenario according to the signal correlation at the antenna feeding points in terms of line-of-sight (LOS reception in main beam direction. The knowledge of the derived relationship may be helpful especially for antenna designers to combine antenna performance values with the significant communication system performance parameters, as e.g. in case of Multiple-Input Multiple-Output (MIMO and diversity configurations.
Directory of Open Access Journals (Sweden)
Hamid Reza Bahrami
2007-01-01
Full Text Available The ergodic capacity of MIMO frequency-flat and -selective channels depends greatly on the eigenvalue distribution of spatial correlation matrices. Knowing the eigenstructure of correlation matrices at the transmitter is very important to enhance the capacity of the system. This fact becomes of great importance in MIMO wireless systems where because of the fast changing nature of the underlying channel, full channel knowledge is difficult to obtain at the transmitter. In this paper, we first investigate the effect of eigenvalues distribution of spatial correlation matrices on the capacity of frequency-flat and -selective channels. Next, we introduce a practical scheme known as linear precoding that can enhance the ergodic capacity of the channel by changing the eigenstructure of the channel by applying a linear transformation. We derive the structures of precoders using eigenvalue decomposition and linear algebra techniques in both cases and show their similarities from an algebraic point of view. Simulations show the ability of this technique to change the eigenstructure of the channel, and hence enhance the ergodic capacity considerably.
Secure Path Selection under Random Fading
Directory of Open Access Journals (Sweden)
Furqan Jameel
2017-05-01
Full Text Available Application-oriented Wireless Sensor Networks (WSNs promises to be one of the most useful technologies of this century. However, secure communication between nodes in WSNs is still an unresolved issue. In this context, we propose two protocols (i.e. Optimal Secure Path (OSP and Sub-optimal Secure Path (SSP to minimize the outage probability of secrecy capacity in the presence of multiple eavesdroppers. We consider dissimilar fading at the main and wiretap link and provide detailed evaluation of the impact of Nakagami-m and Rician-K factors on the secrecy performance of WSNs. Extensive simulations are performed to validate our findings. Although the optimal scheme ensures more security, yet the sub-optimal scheme proves to be a more practical approach to secure wireless links.
Performance Analysis of Mixed Nakagami- m and Gamma–Gamma Dual-Hop FSO Transmission Systems
Zedini, Emna
2015-02-01
In this paper, we carry out a unified performance analysis of a dual-hop relay system over the asymmetric links composed of both radio-frequency (RF) and unified free-space optical (FSO) links under the effect of pointing errors. Both fixed and variable gain relay systems are studied. The RF link is modeled by the Nakagami-m fading channel and the FSO link by the Gamma-Gamma fading channel subject to both types of detection techniques (i.e., heterodyne detection and intensity modulation with direct detection). In particular, we derive new unified closed-form expressions for the cumulative distribution function, the probability density function, the moment generating function (MGF), and the moments of the end-to-end signal-to-noise ratio (SNR) of these systems in terms of the Meijer\\'s G function. Based on these formulas, we offer exact closed-form expressions for the outage probability (OP), the higher order amount of fading, and the average bit error rate (BER) of a variety of binary modulations in terms of the Meijer\\'s G function. Furthermore, an exact closed-form expression of the end-to-end ergodic capacity is derived in terms of the bivariate G function. Additionally, by using the asymptotic expansion of the Meijer\\'s G function at the high-SNR regime, we derive new asymptotic results for the OP, the MGF, and the average BER in terms of simple elementary functions.
Performance of Cooperative Spectrum Sensing over Non-Identical Fading Environments
Rao, Anlei; Alouini, Mohamed-Slim
2012-01-01
Different from previous works in cooperative spec- trum sensing that assumed the sensing channels independent identically distributed (i.i.d.), we investigate in this paper the independent but not identically distributed (i.n.i.d.) situations. In particular, we derive the false-alarm probability and the detection probability of cooperative spectrum sensing with the scheme of energy fusion over i.n.i.d. Rayleigh, Nakagami, and Rician fading channels. From the selected numerical results, we can see that cooperative spectrum sensing still gives considerably better performance even over i.n.i.d. fading environments.
Performance of Cooperative Spectrum Sensing over Non-Identical Fading Environments
Rao, Anlei
2012-09-08
Different from previous works in cooperative spec- trum sensing that assumed the sensing channels independent identically distributed (i.i.d.), we investigate in this paper the independent but not identically distributed (i.n.i.d.) situations. In particular, we derive the false-alarm probability and the detection probability of cooperative spectrum sensing with the scheme of energy fusion over i.n.i.d. Rayleigh, Nakagami, and Rician fading channels. From the selected numerical results, we can see that cooperative spectrum sensing still gives considerably better performance even over i.n.i.d. fading environments.
Analysis of Coded FHSS Systems with Multiple Access Interference over Generalized Fading Channels
Directory of Open Access Journals (Sweden)
Salam A. Zummo
2009-02-01
Full Text Available We study the effect of interference on the performance of coded FHSS systems. This is achieved by modeling the physical channel in these systems as a block fading channel. In the derivation of the bit error probability over Nakagami fading channels, we use the exact statistics of the multiple access interference (MAI in FHSS systems. Due to the mathematically intractable expression of the Rician distribution, we use the Gaussian approximation to derive the error probability of coded FHSS over Rician fading channel. The effect of pilot-aided channel estimation is studied for Rician fading channels using the Gaussian approximation. From this, the optimal hopping rate in coded FHSS is approximated. Results show that the performance loss due to interference increases as the hopping rate decreases.
Exact capacity analysis of multihop transmission over amplify-and-forward relay fading channels
Yilmaz, Ferkan; Kucur, Oǧuz; Alouini, Mohamed-Slim
2010-01-01
In this paper, we propose an analytical framework on the exact computation of the average capacity of multihop transmission over amplify-and-forward relay fading channels. Our approach relies on the algebraic combination of Mellin and Laplace transforms to obtain exact single integral expressions which can be easily computed by Gauss-Chebyshev Quadrature (GCQ) rule. As such, the derived results are a convenient tool to analyze the average capacity of multihop transmission over amplify-and-forward relay fading channels. As an application of the analytical framework on the exact computation of the average capacity of multihop transmission, some examples are accentuated for generalized Nakagami-m fading channels. Numerical and simulation results, performed to verify the correctness of the proposed formulation, are in perfect agreement. ©2010 IEEE.
Exact capacity analysis of multihop transmission over amplify-and-forward relay fading channels
Yilmaz, Ferkan
2010-09-01
In this paper, we propose an analytical framework on the exact computation of the average capacity of multihop transmission over amplify-and-forward relay fading channels. Our approach relies on the algebraic combination of Mellin and Laplace transforms to obtain exact single integral expressions which can be easily computed by Gauss-Chebyshev Quadrature (GCQ) rule. As such, the derived results are a convenient tool to analyze the average capacity of multihop transmission over amplify-and-forward relay fading channels. As an application of the analytical framework on the exact computation of the average capacity of multihop transmission, some examples are accentuated for generalized Nakagami-m fading channels. Numerical and simulation results, performed to verify the correctness of the proposed formulation, are in perfect agreement. ©2010 IEEE.
Error Rates of M-PAM and M-QAM in Generalized Fading and Generalized Gaussian Noise Environments
Soury, Hamza
2013-07-01
This letter investigates the average symbol error probability (ASEP) of pulse amplitude modulation and quadrature amplitude modulation coherent signaling over flat fading channels subject to additive white generalized Gaussian noise. The new ASEP results are derived in a generic closed-form in terms of the Fox H function and the bivariate Fox H function for the extended generalized-K fading case. The utility of this new general closed-form is that it includes some special fading distributions, like the Generalized-K, Nakagami-m, and Rayleigh fading and special noise distributions such as Gaussian and Laplacian. Some of these special cases are also treated and are shown to yield simplified results.
Zorgui, Marwen; Rezki, Zouheir; Alomair, Basel; Alouini, Mohamed-Slim
2015-01-01
numerical optimization problem that we derive. A necessary and sufficient condition for beamforming (i.e., transmitting along the strongest channel mode) to be capacity-achieving is derived. Finally, we analyze the impact of correlation matrices
Outage and BER analysis for ultrawideband-based WPAN in Nakagami-m fading channels
Mehbodniya, Abolfazl
2011-09-01
This paper presents a performance analysis of multiband orthogonal frequency-division multiplexing (MB-OFDM) in ultra wideband (UWB)-based personal area networks (UPANs). A UPAN consists of devices with different UWB technologies at the physical layer. Approximate expressions for the outage probability and average bit error rate (BER) are derived in closed form for the MB-OFDM target receiver, taking into account multi-user interference (MUI), as well as external interference in the form of time-hopping (TH) and direct-sequence (DS) UWB signals. © 2010 IEEE.
Performance Analysis of OFDM in Frequency Selective, Slowly Fading Nakagami Channels
National Research Council Canada - National Science Library
Count, Patrick
2001-01-01
...) as the modulation technique of choice. Given the incredible growth in the industry as manifest by the seemingly infinite demand for wireless products and services and the accompanying need for superior performance of these systems...
Delay performance of a broadcast spectrum sharing network in Nakagami-m fading
Khan, Fahd Ahmed; Tourki, Kamel; Alouini, Mohamed-Slim; Qaraqe, Khalid A.
2014-01-01
In this paper, we analyze the delay performance of a point-to-multipoint secondary network (P2M-SN), which is concurrently sharing the spectrum with a point-to-multipoint primary network (P2M-PN). The channel is assumed to be independent
Outage and BER analysis for ultrawideband-based WPAN in Nakagami-m fading channels
Mehbodniya, Abolfazl; Aissa, Sonia
2011-01-01
layer. Approximate expressions for the outage probability and average bit error rate (BER) are derived in closed form for the MB-OFDM target receiver, taking into account multi-user interference (MUI), as well as external interference in the form of time
Performance of Generalized Multicarrier DS-CDMA over Nakagami-$m$ Fading Channels
Yang, L-L.; Hanzo, L.
2002-01-01
A class of generalized multicarrier direct sequence code-division multiple-access (MC DS-CDMA) schemes is defined and its performance is considered over multipath Nakagamifading channels. The spacing between two adjacent subcarriers of the generalized MC DS-CDMA is a variable, allowing us to gain insight into the effects of the spacing on the bit error rate (BER) performance of MC DS-CDMA systems. This generalized MC DS-CDMA scheme includes the subclasses of multitone DS-CDMA and orthogonal M...
Performance Analysis of OFDM in Frequency Selective, Slowly Fading Nakagami Channels
National Research Council Canada - National Science Library
Count, Patrick
2001-01-01
In an effort to offer faster, more reliable wireless communications services to the public, many wireless standardization committees have, in recent years, adopted Orthogonal Frequency Division Multiplexing (OFDM...
Adaptive Modulation with Best User Selection over Non-Identical Nakagami Fading Channels
Rao, Anlei; Alouini, Mohamed-Slim
2012-01-01
capacity, spectral efficiency, and bit-error-rate (BER) for both constant-power variable-rate and variable-power variable-rate uncoded M-ary quadrature amplitude modulation (M-QAM) schemes. We also study the impact of time delay on the average BER
Outage performance of Decode-and-Forward partial selection in Nakagami-m fading channels
Benjillali, Mustapha; Alouini, Mohamed-Slim
2010-01-01
, selects the best relay to increase the chances of successful decoding and hence the possibility of cooperation when the direct link is also available. After deriving the exact distribution of the sum of two gamma variates with the same shape parameter
Walker, Ernest; Chen, Xinjia; Cooper, Reginald L.
2010-04-01
An arbitrarily accurate approach is used to determine the bit-error rate (BER) performance for generalized asynchronous DS-CDMA systems, in Gaussian noise with Raleigh fading. In this paper, and the sequel, new theoretical work has been contributed which substantially enhances existing performance analysis formulations. Major contributions include: substantial computational complexity reduction, including a priori BER accuracy bounding; an analytical approach that facilitates performance evaluation for systems with arbitrary spectral spreading distributions, with non-uniform transmission delay distributions. Using prior results, augmented by these enhancements, a generalized DS-CDMA system model is constructed and used to evaluated the BER performance, in a variety of scenarios. In this paper, the generalized system modeling was used to evaluate the performance of both Walsh- Hadamard (WH) and Walsh-Hadamard-seeded zero-correlation-zone (WH-ZCZ) coding. The selection of these codes was informed by the observation that WH codes contain N spectral spreading values (0 to N - 1), one for each code sequence; while WH-ZCZ codes contain only two spectral spreading values (N/2 - 1,N/2); where N is the sequence length in chips. Since these codes span the spectral spreading range for DS-CDMA coding, by invoking an induction argument, the generalization of the system model is sufficiently supported. The results in this paper, and the sequel, support the claim that an arbitrary accurate performance analysis for DS-CDMA systems can be evaluated over the full range of binary coding, with minimal computational complexity.
Capacity of Fading Channels in the Low Power Regime
Benkhelifa, Fatma
2013-01-01
The low power regime has attracted various researchers in the information theory and communication communities to understand the performance limits of wireless systems. Indeed, the energy consumption is becoming one of the major limiting factors in wireless systems. As such, energy-efficient wireless systems are of major importance to the next generation wireless systems designers. The capacity is a metric that measures the performance limit of a wireless system. The study of the ergodic capacity of some fading channels in the low power regime is the main subject of this thesis. In our study, we consider that the receiver has always a full knowledge of the channel state information. However, we assume that the transmitter has possibly imperfect knowledge of the channel state information, i.e. he knows either perfectly the channel or only an estimated version of the channel. Both radio frequency and free space optical communication channel models are considered. The main contribution of this work is the explicit characterization of how the capacity scales as function of the signal-to-noise ratio in the low power regime. This allows us to characterize the gain due to the perfect knowledge compared to no knowledge of the channel state information at the transmitter. In particular, we show that the gain increases logarithmically for radio frequency communication. However, the gain increases as log2(Pavg) or log4(Pavg) for free-space optical communication, where Pavg is the average power constraint imposed to the input. Furthermore, we characterize the capacity of cascaded fading channels and we applied the result to Rayleigh-product fading channel and to a free-space optical link over gamma-gamma atmospheric turbulence in the presence of pointing errors. Finally, we study the capacity of Nakagami-m fading channel under quality of service constraints, namely the effective capacity. We have shown that the effective capacity converges to Shannon capacity in the very low
Exact Symbol Error Probability of Cross-QAM in AWGN and Fading Channels
Directory of Open Access Journals (Sweden)
Zhang Xi-chun
2010-01-01
Full Text Available The exact symbol error probability (SEP performance of -ary cross quadrature amplitude modulation (QAM in additive white Gaussian noise (AWGN channel and fading channels, including Rayleigh, Nakagami-m, Rice, and Nakagami-q (Hoyt channels, is analyzed. The obtained closed-form SEP expressions contain a finite (in proportion to sum of single integrals with finite limits and an integrand composed of elementary (exponential, trigonometric, and/or power functions, thus readily enabling numerical evaluation. Particularly, Gaussian -function is a special case of these integrals and is included in the SEP expressions. Simple and very precise approximations, which contain only Gaussian -function for AWGN channel and contain three terms of the single integrals mentioned above for fading channels, respectively, are also given. The analytical expressions show excellent agreement with the simulation results, and numerical evaluation with the proposed expressions reveals that cross QAM can obtain at least 1.1 dB gain compared to rectangular QAM when SEP < 0.3 in all the considered channels.
Quantitative Ultrasonic Nakagami Imaging of Neck Fibrosis After Head and Neck Radiation Therapy
Energy Technology Data Exchange (ETDEWEB)
Yang, Xiaofeng [Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia (United States); Yoshida, Emi [Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California (United States); Cassidy, Richard J.; Beitler, Jonathan J.; Yu, David S.; Curran, Walter J. [Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia (United States); Liu, Tian, E-mail: tliu34@emory.edu [Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia (United States)
2015-06-01
Purpose: To investigate the feasibility of ultrasound Nakagami imaging to quantitatively assess radiation-induced neck fibrosis, a common sequela of radiation therapy (RT) to the head and neck. Methods and Materials: In a pilot study, 40 study participants were enrolled and classified into 3 subgroups: (1) a control group of 12 healthy volunteers; (2) an asymptomatic group of 11 patients who had received intensity modulated RT for head and neck cancer and had experienced no neck fibrosis; and (3) a symptomatic group of 17 post-RT patients with neck fibrosis. Each study participant underwent 1 ultrasound study in which scans were performed in the longitudinal orientation of the bilateral neck. Three Nakagami parameters were calculated to quantify radiation-induced tissue injury: Nakagami probability distribution function, shape, and scaling parameters. Physician-based assessments of the neck fibrosis were performed according to the Radiation Therapy Oncology Group late morbidity scoring scheme, and patient-based fibrosis assessments were rated based on symptoms such as pain and stiffness. Results: Major discrepancies existed between physician-based and patient-based assessments of radiation-induced fibrosis. Significant differences in all Nakagami parameters were observed between the control group and 2 post-RT groups. Moreover, significant differences in Nakagami shape and scaling parameters were observed among asymptomatic and symptomatic groups. Compared with the control group, the average Nakagami shape parameter value increased by 32.1% (P<.001), and the average Nakagami scaling parameter increased by 55.7% (P<.001) for the asymptomatic group, whereas the Nakagami shape parameter increased by 74.1% (P<.001) and the Nakagami scaling parameter increased by 83.5% (P<.001) for the symptomatic group. Conclusions: Ultrasonic Nakagami imaging is a potential quantitative tool to characterize radiation-induced asymptomatic and symptomatic neck fibrosis.
Quantitative Ultrasonic Nakagami Imaging of Neck Fibrosis After Head and Neck Radiation Therapy
International Nuclear Information System (INIS)
Yang, Xiaofeng; Yoshida, Emi; Cassidy, Richard J.; Beitler, Jonathan J.; Yu, David S.; Curran, Walter J.; Liu, Tian
2015-01-01
Purpose: To investigate the feasibility of ultrasound Nakagami imaging to quantitatively assess radiation-induced neck fibrosis, a common sequela of radiation therapy (RT) to the head and neck. Methods and Materials: In a pilot study, 40 study participants were enrolled and classified into 3 subgroups: (1) a control group of 12 healthy volunteers; (2) an asymptomatic group of 11 patients who had received intensity modulated RT for head and neck cancer and had experienced no neck fibrosis; and (3) a symptomatic group of 17 post-RT patients with neck fibrosis. Each study participant underwent 1 ultrasound study in which scans were performed in the longitudinal orientation of the bilateral neck. Three Nakagami parameters were calculated to quantify radiation-induced tissue injury: Nakagami probability distribution function, shape, and scaling parameters. Physician-based assessments of the neck fibrosis were performed according to the Radiation Therapy Oncology Group late morbidity scoring scheme, and patient-based fibrosis assessments were rated based on symptoms such as pain and stiffness. Results: Major discrepancies existed between physician-based and patient-based assessments of radiation-induced fibrosis. Significant differences in all Nakagami parameters were observed between the control group and 2 post-RT groups. Moreover, significant differences in Nakagami shape and scaling parameters were observed among asymptomatic and symptomatic groups. Compared with the control group, the average Nakagami shape parameter value increased by 32.1% (P<.001), and the average Nakagami scaling parameter increased by 55.7% (P<.001) for the asymptomatic group, whereas the Nakagami shape parameter increased by 74.1% (P<.001) and the Nakagami scaling parameter increased by 83.5% (P<.001) for the symptomatic group. Conclusions: Ultrasonic Nakagami imaging is a potential quantitative tool to characterize radiation-induced asymptomatic and symptomatic neck fibrosis
Observation of auroral fading before breakup
International Nuclear Information System (INIS)
Pellinen, R.J.; Heikkila, W.J.
1978-02-01
We have obtained detailed observations of the onset of auroral breakup using a variety of instruments with time resolution of some tens of seconds. Rapid sequences of all-sky photographs, and fast meridian scans by photometers, show that breakup is usually preceded by moderate brightening, followed by fading of the auroral brightness lasting one or two minutes, before the actual breakup itself. At the time of the fading there is a brief darkening of the poleward sky. Often the breakup is preceded by one or more rapid intensifications, each one preceded by local fading. Pseudo-breakups may also occur without the development of a major event. A bonafide breakup may begin on the fading arc, on an adjacent arc, or in an entirely new region nearby. This optical activity is closely correlated with the development of auroral radar echoes, suggesting that variations in the ionospheric and magnetospheric electric and magnetic fields are responsible for the observed auroral variations. Data from the IMS magnetometer network provide some indication of a correlated response by the local auroral and ionospheric current, although this could be partly due to changes in conductivity. Riometer recordings show a slow decrease in ionsperic radio wave absorption over a period of about ten minutes prior to breakup, with the largest decrease essentially to quiet-time values in the region of auroral fading and subsequent breakup. The implications of these observations regarding the trigger mechanism for the expansion phase of a magnetospheric substorm are discussed. (author)
Classification of breast masses by ultrasonic Nakagami imaging: a feasibility study
Tsui, Po-Hsiang; Yeh, Chih-Kuang; Chang, Chien-Cheng; Liao, Yin-Yin
2008-11-01
Ultrasound is an important clinical tool in noninvasive diagnoses of breast cancer. The Nakagami statistical parameter estimated from the ultrasonic backscattered envelope has been demonstrated to be useful in complementing conventional B-mode scans when classifying breast masses. However, the shadowing effect caused by certain high-attenuation tumors in the B-mode image makes the tumor contour unclear, and thus it is more difficult to choose an appropriate region of interest from which to collect tumor data for estimating the Nakagami parameter. This study explored the feasibility of using the Nakagami parametric image to overcome the shadowing effect for visualizing the properties of breast masses. Experiments were performed on a breast-mimicking phantom and on some typical clinical cases for cysts, fat and tumors (fibroadenoma) (n = 18) in order to explore the performance of the Nakagami image under ideal and practical conditions. The experimental results showed that the Nakagami image pixels (i.e. the local Nakagami parameter) in the cyst, tumor and fat are 0.21 ± 0.01, 0.65 ± 0.05 and 0.98 ± 0.07, respectively, for six independent phantom measurements, and 0.14 ± 0.03, 0.67 ± 0.11 and 0.89 ± 0.08, respectively, for clinical experiments. This suggests that the Nakagami image is able to classify various breast masses (p < 0.005) although the clinical results from tumors of different cases have a larger variance that may be caused by the complexity of real breast tissues. In particular, unlike the B-mode image, the Nakagami image is not subject to significant shadowing effects, making it useful to complement the B-mode image to describe the tumor contour for identifying the tumor-related region when the shadowing effect is stronger or a low system gain is used.
Classification of breast masses by ultrasonic Nakagami imaging: a feasibility study
Energy Technology Data Exchange (ETDEWEB)
Tsui, P-H; Chang, C-C [Division of Mechanics, Research Center for Applied Sciences, Academia Sinica, 128, Section 2, Academia Road, Nankang, Taipei 11529, Taiwan (China); Yeh, C-K; Liao, Y-Y [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan (China)], E-mail: mechang@gate.sinica.edu.tw, E-mail: ckyeh@mx.nthu.edu.tw
2008-11-07
Ultrasound is an important clinical tool in noninvasive diagnoses of breast cancer. The Nakagami statistical parameter estimated from the ultrasonic backscattered envelope has been demonstrated to be useful in complementing conventional B-mode scans when classifying breast masses. However, the shadowing effect caused by certain high-attenuation tumors in the B-mode image makes the tumor contour unclear, and thus it is more difficult to choose an appropriate region of interest from which to collect tumor data for estimating the Nakagami parameter. This study explored the feasibility of using the Nakagami parametric image to overcome the shadowing effect for visualizing the properties of breast masses. Experiments were performed on a breast-mimicking phantom and on some typical clinical cases for cysts, fat and tumors (fibroadenoma) (n = 18) in order to explore the performance of the Nakagami image under ideal and practical conditions. The experimental results showed that the Nakagami image pixels (i.e. the local Nakagami parameter) in the cyst, tumor and fat are 0.21 {+-} 0.01, 0.65 {+-} 0.05 and 0.98 {+-} 0.07, respectively, for six independent phantom measurements, and 0.14 {+-} 0.03, 0.67 {+-} 0.11 and 0.89 {+-} 0.08, respectively, for clinical experiments. This suggests that the Nakagami image is able to classify various breast masses (p < 0.005) although the clinical results from tumors of different cases have a larger variance that may be caused by the complexity of real breast tissues. In particular, unlike the B-mode image, the Nakagami image is not subject to significant shadowing effects, making it useful to complement the B-mode image to describe the tumor contour for identifying the tumor-related region when the shadowing effect is stronger or a low system gain is used.
Error rates of a full-duplex system over EGK fading channels subject to laplacian interference
Soury, Hamza
2017-07-31
This paper develops a mathematical paradigm to study downlink error rates and throughput for half-duplex (HD) terminals served by a full-duplex (FD) base station (BS). Particularly, we study the dominant intra-cell interferer problem that appears between HD users scheduled on the same FD-channel. The distribution of the dominant interference is first characterized via its distribution function, which is derived in closed-form. Assuming Nakagami-m fading, the probability of error for different modulation schemes is studied and a unified closed-form expression for the average symbol error rate is derived. To this end, we show the effective downlink throughput gain, harvested by employing FD communication at a BS that serves HD users, as a function of the signal-to-interference-ratio when compared to an idealized HD interference and noise free BS operation.
Achievable rate of spectrum sharing cognitive radio systems over fading channels at low-power regime
Sboui, Lokman
2014-11-01
We study the achievable rate of cognitive radio (CR) spectrum sharing systems at the low-power regime for general fading channels and then for Nakagami fading. We formally define the low-power regime and present the corresponding closed-form expressions of the achievable rate lower bound under various types of interference and/or power constraints, depending on the available channel state information of the cross link (CL) between the secondary-user transmitter and the primary-user receiver. We explicitly characterize two regimes where either the interference constraint or the power constraint dictates the optimal power profile. Our framework also highlights the effects of different fading parameters on the secondary link (SL) ergodic achievable rate. We also study more realistic scenarios when there is either 1-bit quantized channel feedback from the CL alone or 2-bit feedback from both the CL and the SL and propose simple power control schemes and show that these schemes achieve the previously achieved rate at the low-power regime. Interestingly, we show that the low-power regime analysis provides a specific insight into the maximum achievable rate behavior of CR that has not been reported by previous studies.
3D ultrasound Nakagami imaging for radiation-induced vaginal fibrosis
Yang, Xiaofeng; Rossi, Peter; Shelton, Joseph; Bruner, Debrorah; Tridandapani, Srini; Liu, Tian
2014-03-01
Radiation-induced vaginal fibrosis is a debilitating side-effect affecting up to 80% of women receiving radiotherapy for their gynecological (GYN) malignancies. Despite the significant incidence and severity, little research has been conducted to identify the pathophysiologic changes of vaginal toxicity. In a previous study, we have demonstrated that ultrasound Nakagami shape and PDF parameters can be used to quantify radiation-induced vaginal toxicity. These Nakagami parameters are derived from the statistics of ultrasound backscattered signals to capture the physical properties (e.g., arrangement and distribution) of the biological tissues. In this paper, we propose to expand this Nakagami imaging concept from 2D to 3D to fully characterize radiation-induced changes to the vaginal wall within the radiation treatment field. A pilot study with 5 post-radiotherapy GYN patients was conducted using a clinical ultrasound scanner (6 MHz) with a mechanical stepper. A serial of 2D ultrasound images, with radio-frequency (RF) signals, were acquired at 1 mm step size. The 2D Nakagami shape and PDF parameters were calculated from the RF signal envelope with a sliding window, and then 3D Nakagami parameter images were generated from the parallel 2D images. This imaging method may be useful as we try to monitor radiation-induced vaginal injury, and address vaginal toxicities and sexual dysfunction in women after radiotherapy for GYN malignancies.
A reason of fast and deep fading of centimeter wave
International Nuclear Information System (INIS)
Danzan, D.; Damdinsuren, E.; Hiamjav, J.; Chuluunbaatar, Ch.; Battulga, S.
1992-01-01
First discovered experimentally exactly correlation between of appearance and of disappearance of optical mirage and fast and deep fading of horizontal polarization of centimeter wave. Proved the interference of the straight and reflected rays from the thin layer of air in mirage a reason of this fading. The physical parameters data of the layer of mirage: change of dielectric permeability and n/ h gradient of refraction index of air in this layer are been showed
National Research Council Canada - National Science Library
Tsoumanis, Andreas
2004-01-01
...) coding with soft decision decoding (SDD) and maximum- likelihood detection improves performance as compared to uncoded signals, In addition, the combination of maximum-likelihood detection and error connection coding renders pulsed-noise...
Enhancing the efficiency of constrained dual-hop variable-gain AF relaying under nakagami-m fading
Zafar, Ammar; Radaydeh, Redha Mahmoud; Chen, Yunfei; Alouini, Mohamed-Slim
2014-01-01
-to-end signal-to-noise-ratio (SNR) and the overall power consumed is minimized while maintaining this constraint. This problem is considered under two different assumptions of the available channel state information (CSI) at the relays, namely full CSI
Zafar, Ammar
2013-09-01
In this paper, we study power allocation strategies for a fixed-gain amplify-and-forward relay network employing multiple relays. We consider two optimization problems for the relay network: 1) maximizing the end-to-end signalto- noise ratio (SNR) and 2) minimizing the total power consumption while maintaining the end-to-end SNR over a threshold value. We investigate these two problems for two relaying protocols of all-participate (AP) relaying and selective relaying and two cases of feedback to the relays, full and limited. We show that the SNR maximization problem is concave and the power minimization problem is convex for all protocols and feedback cases considered. We obtain closed-form expressions for the two problems in the case of full feedback and solve the problems through convex programming for limited feedback. Numerical results show the benefit of having full feedback at the relays for both optimization problems. However, they also show that feedback overhead can be reduced by having only limited feedback to the relays with only a small degradation in performance.
Performance of DS-UWB in MB-OFDM and multi-user interference over Nakagami-m fading channels
Mehbodniya, Abolfazl; Aissa, Sonia
2011-01-01
The mutual interference between the two ultra wideband (UWB) technologies, which use the same frequency spectrum, will be a matter of concern in the near future. In this context, we present a performance analysis of direct-sequence (DS) UWB
Benkhelifa, Fatma; Rezki, Zouheir; Alouini, Mohamed-Slim
2013-01-01
information (CSI) at both the transmitter and at the receiver. We focus on the low Signal-to-Noise Ratio (SNR) regime. We show that the effective capacity for any arbitrary but finite statistically delay Quality of Service (QoS) exponent θ, scales essentially
Exact Outage Probability of Dual-Hop CSI-Assisted AF Relaying Over Nakagami-m Fading Channels
Xia, Minghua; Aissa, Sonia; Wu, Yik-Chung
2012-01-01
to evaluate the outage performance of the system under study. The analytical results of outage probability coincide exactly with Monte-Carlo simulation results and outperform the previously reported upper bounds in the low and medium SNR regions.
Aniba, Ghassane; Aissa, Sonia
2011-01-01
works addressed the link layer performance of AM with truncated ARQ but without packet combining. In addition, previously proposed AM algorithms are not optimal and can provide poor performance when packet combining is implemented. Herein, we first show
Lin, Jen-Jen; Cheng, Jung-Yu; Huang, Li-Fei; Lin, Ying-Hsiu; Wan, Yung-Liang; Tsui, Po-Hsiang
2017-05-01
The Nakagami distribution is an approximation useful to the statistics of ultrasound backscattered signals for tissue characterization. Various estimators may affect the Nakagami parameter in the detection of changes in backscattered statistics. In particular, the moment-based estimator (MBE) and maximum likelihood estimator (MLE) are two primary methods used to estimate the Nakagami parameters of ultrasound signals. This study explored the effects of the MBE and different MLE approximations on Nakagami parameter estimations. Ultrasound backscattered signals of different scatterer number densities were generated using a simulation model, and phantom experiments and measurements of human liver tissues were also conducted to acquire real backscattered echoes. Envelope signals were employed to estimate the Nakagami parameters by using the MBE, first- and second-order approximations of MLE (MLE 1 and MLE 2 , respectively), and Greenwood approximation (MLE gw ) for comparisons. The simulation results demonstrated that, compared with the MBE and MLE 1 , the MLE 2 and MLE gw enabled more stable parameter estimations with small sample sizes. Notably, the required data length of the envelope signal was 3.6 times the pulse length. The phantom and tissue measurement results also showed that the Nakagami parameters estimated using the MLE 2 and MLE gw could simultaneously differentiate various scatterer concentrations with lower standard deviations and reliably reflect physical meanings associated with the backscattered statistics. Therefore, the MLE 2 and MLE gw are suggested as estimators for the development of Nakagami-based methodologies for ultrasound tissue characterization. Copyright © 2017 Elsevier B.V. All rights reserved.
Performance Analysis of Ad Hoc Dispersed Spectrum Cognitive Radio Networks over Fading Channels
Directory of Open Access Journals (Sweden)
Mohammad Muneer
2011-01-01
Full Text Available Cognitive radio systems can utilize dispersed spectrum, and thus such approach is known as dispersed spectrum cognitive radio systems. In this paper, we first provide the performance analysis of such systems over fading channels. We derive the average symbol error probability of dispersed spectrum cognitive radio systems for two cases, where the channel for each frequency diversity band experiences independent and dependent Nakagami- fading. In addition, the derivation is extended to include the effects of modulation type and order by considering M-ary phase-shift keying ( -PSK and M-ary quadrature amplitude modulation -QAM schemes. We then consider the deployment of such cognitive radio systems in an ad hoc fashion. We consider an ad hoc dispersed spectrum cognitive radio network, where the nodes are assumed to be distributed in three dimension (3D. We derive the effective transport capacity considering a cubic grid distribution. Numerical results are presented to verify the theoretical analysis and show the performance of such networks.
Fading Evaluation in the 60 GHz Band in Line-of-Sight Conditions
Directory of Open Access Journals (Sweden)
J. Reig
2014-01-01
Full Text Available An exhaustive analysis of the small-scale fading amplitude in the 60 GHz band is addressed for line-of-sight conditions (LOS. From a measurement campaign carried out in a laboratory, we have estimated the distribution of the small-scale fading amplitude over a bandwidth of 9 GHz. From the measured data, we have estimated the parameters of the Rayleigh, Rice, Nakagami-m, Weibull, and α-μ distributions for the small-scale amplitudes. The test of Kolmogorov-Smirnov (K-S for each frequency bin is used to evaluate the performance of such statistical distributions. Moreover, the distributions of the main estimated parameters for such distributions are calculated and approximated for lognormal statistics in some cases. The matching of the above distributions to the experimental distribution has also been analyzed for the lower tail of the cumulative distribution function (CDF. These parameters offer information about the narrowband channel behavior that is useful for a better knowledge of the propagation characteristics at 60 GHz.
Hussain, Syed Imtiaz; Alouini, Mohamed-Slim; Hasna, Mazen Omar
2010-01-01
for a cooperative network with multiple relays operating in amplify-and-forward (AF) mode over identical Nakagami-m channels using exact source-relay-destination signal to noise ratio (SNR) expression. We derive accurate closed form expressions
Secret Sharing over Fast-Fading MIMO Wiretap Channels
Directory of Open Access Journals (Sweden)
Bloch Matthieu
2009-01-01
Full Text Available Secret sharing over the fast-fading MIMO wiretap channel is considered. A source and a destination try to share secret information over a fast-fading MIMO channel in the presence of an eavesdropper who also makes channel observations that are different from but correlated to those made by the destination. An interactive, authenticated public channel with unlimited capacity is available to the source and destination for the secret sharing process. This situation is a special case of the "channel model with wiretapper" considered by Ahlswede and Csiszár. An extension of their result to continuous channel alphabets is employed to evaluate the key capacity of the fast-fading MIMO wiretap channel. The effects of spatial dimensionality provided by the use of multiple antennas at the source, destination, and eavesdropper are then investigated.
Observations of anomalous fading in maiolica
International Nuclear Information System (INIS)
Bowman, S.G.E.
1988-01-01
In the course of an authenticity study on Italian maiolica (tin-glazed earthenware of the Renaissance period), storage at elevated temperature was used to accelerate anomalous fading. Substantial levels of fading were observed in about half of the samples, and in these cases the variation of fading with glow curve temperature accounted for the lack of an equivalent dose plateau. Some evidence was found for a difference in the fading between alpha and beta induced thermoluminescence (TL). More importantly, some samples with unstable natural TL were found: the implications of this for dating and the circumvention of fading are discussed. (author)
Outage Analysis of Train-to-Train Communication Model over Nakagami-m Channel in High-Speed Railway
Directory of Open Access Journals (Sweden)
Pengyu Liu
2013-01-01
Full Text Available This paper analyzes the end-to-end outage performance of high-speed-railway train-to-train communication model in high-speed railway over independent identical and nonidentical Nakagami-m channels. The train-to-train communication is inter-train communication without an aid of infrastructure (for base station. Source train uses trains on other rail tracks as relays to transmit signals to destination train on the same track. The mechanism of such communication among trains can be divided into three cases based on occurrence of possible-occurrence relay trains. We first present a new closed form for the sum of squared independent Nakagami-m variates and then derive an expression for the outage probability of the identical and non-identical Nakagami-m channels in three cases. In particular, the problem is improved by the proposed formulation that statistic for sum of squared Nakagami-m variates with identical m tends to be infinite. Numerical analysis indicates that the derived analytic results are reasonable and the outage performance is better over Nakagami-m channel in high-speed railway scenarios.
Energy Technology Data Exchange (ETDEWEB)
Yang, Xiaofeng; Wu, Ning; Wang, Yuefeng [Radiation Oncology, Emory University, Atlanta, Georgia 30322 (United States); Tridandapani, Srini [Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia 30322 (United States); School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Winship Cancer Institute, Emory University, Atlanta, Georgia 30322 (United States); Beitler, Jonathan J.; Yu, David S.; Curran, Walter J.; Liu, Tian, E-mail: tliu34@emory.edu [Radiation Oncology, Emory University, Atlanta, Georgia 30322 and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322 (United States); Bruner, Deborah W. [Radiation Oncology, Emory University, Atlanta, Georgia 30322 (United States); Winship Cancer Institute, Emory University, Atlanta, Georgia 30322 (United States); School of Nursing, Emory University, Atlanta, Georgia 30322 (United States)
2014-02-15
Purpose: The study aims to investigate whether Nakagami parameters—estimated from the statistical distribution of the backscattered ultrasound radio-frequency (RF) signals—could provide a means for quantitative characterization of parotid-gland injury resulting from head-and-neck radiotherapy. Methods: A preliminary clinical study was conducted with 12 postradiotherapy patients and 12 healthy volunteers. Each participant underwent one ultrasound study in which ultrasound scans were performed in the longitudinal, i.e., vertical orientation on the bilateral parotids. For the 12 patients, the mean radiation dose to the parotid glands was 37.7 ± 9.5 Gy, and the mean follow-up time was 16.3 ± 4.8 months. All enrolled patients experienced grade 1 or 2 late salivary-gland toxicity (RTOG/EORTC morbidity scale). The normal parotid glands served as the control group. The Nakagami-scaling and Nakagami-shape parameters were computed from the RF data to quantify radiation-induced parotid-gland changes. Results: Significant differences in Nakagami parameters were observed between the normal and postradiotherapy parotid glands. Compared with the control group, the Nakagami-scaling parameter of the postradiotherapy group decreased by 25.8% (p < 0.001), and the Nakagami-shape parameter decreased by 31.3% (p < 0.001). The area under the receiver operating characteristic curve was 0.85 for the Nakagami-scaling parameter and was 0.95 for the Nakagami-shape parameter, which further demonstrated the diagnostic efficiency of the Nakagami parameters. Conclusions: Nakagami parameters could be used to quantitatively measure parotid-gland injury following head-and-neck radiotherapy. Moreover, the clinical feasibility was demonstrated and this study provides meaningful preliminary data for future clinical investigation.
Wang, Yue; Wang, Ping; Liu, Xiaoxia; Cao, Tian
2018-03-01
The performance of decode-and-forward dual-hop mixed radio frequency / free-space optical system in urban area is studied. The RF link is modeled by the Nakagami-m distribution and the FSO link is described by the composite exponentiated Weibull (EW) fading channels with nonzero boresight pointing errors (NBPE). For comparison, the ABER results without pointing errors (PE) and those with zero boresight pointing errors (ZBPE) are also provided. The closed-form expression for the average bit error rate (ABER) in RF link is derived with the help of hypergeometric function, and that in FSO link is obtained by Meijer's G and generalized Gauss-Laguerre quadrature functions. Then, the end-to-end ABERs with binary phase shift keying modulation are achieved on the basis of the computed ABER results of RF and FSO links. The end-to-end ABER performance is further analyzed with different Nakagami-m parameters, turbulence strengths, receiver aperture sizes and boresight displacements. The result shows that with ZBPE and NBPE considered, FSO link suffers a severe ABER degradation and becomes the dominant limitation of the mixed RF/FSO system in urban area. However, aperture averaging can bring significant ABER improvement of this system. Monte Carlo simulation is provided to confirm the validity of the analytical ABER expressions.
Fade Mitigation Techniques at Ka-Band
Dissanayake, Asoka (Editor)
1996-01-01
Rain fading is the dominant propagation impairment affecting Ka-band satellite links and rain fade mitigation is a key element in the design of Ka-band satellite networks. Some of the common fade mitigation techniques include: power control, diversity, adaptive coding, and resource sharing. The Advanced Communications Technology Satellite (ACTS) provides an excellent opportunity to develop and test Ka-band rain impairment amelioration techniques. Up-link power control and diversity are discussed in this paper.
Performance of fading multi-user diversity for underlay cognitive networksy
Khan, Fahd Ahmed
2013-05-01
Having multiple secondary users (SUs) can be exploited to achieve multiuser diversity and improve the throughput of the underlay secondary network. In the cognitive setting, satisfying the interference constraint is essential, and thus, a scheduling scheme is considered where some SUs are preselected based on the low interference power. From this subset, the SU that yields the highest throughput is selected for transmission. This scheduling scheme helps to lower the interference power while giving good throughput. For an independent but not identically distributed Nakagami-m fading channel, we obtain exact closed-form expressions of the capacity of this scheduling scheme. Furthermore, the scheduling time of SUs is characterized and closed-form expressions for the mean time after which a SU is selected for transmission are obtained. Numerical simulations are performed to corroborate the derived analytical results. Our results show that at low interference threshold, increasing transmit power of the SUs is not beneficial and results in reduced capacity. Furthermore, the channel idle time (i.e. time that no user is utilizing the channel) reduces with increasing the number of SUs. © 2013 IEEE.
Intergranular Cracking as a Major Cause of Long-Term Capacity Fading of Layered Cathodes.
Liu, Hao; Wolf, Mark; Karki, Khim; Yu, Young-Sang; Stach, Eric A; Cabana, Jordi; Chapman, Karena W; Chupas, Peter J
2017-06-14
Capacity fading has limited commercial layered Li-ion battery electrodes to NCA) electrode change after capacity fade following months of slow charge-discharge. The changes in the reactions that underpin energy storage after long-term cycling directly correlate to the capacity loss; heterogeneous reaction kinetics observed during extended cycles quantitatively account for the capacity loss. This reaction heterogeneity is ultimately attributed to intergranular fracturing that degrades the connectivity of subsurface grains within the polycrystalline NCA aggregate.
When does fading enhance perceptual category learning?
Pashler, Harold; Mozer, Michael C
2013-07-01
Training that uses exaggerated versions of a stimulus discrimination (fading) has sometimes been found to enhance category learning, mostly in studies involving animals and impaired populations. However, little is known about whether and when fading facilitates learning for typical individuals. This issue was explored in 7 experiments. In Experiments 1 and 2, observers discriminated stimuli based on a single sensory continuum (time duration and line length, respectively). Adaptive fading dramatically improved performance in training (unsurprisingly) but did not enhance learning as assessed in a final test. The same was true for nonadaptive linear fading (Experiment 3). However, when variation in length (predicting category membership) was embedded among other (category-irrelevant) variation, fading dramatically enhanced not only performance in training but also learning as assessed in a final test (Experiments 4 and 5). Fading also helped learners to acquire a color saturation discrimination amid category-irrelevant variation in hue and brightness, although this learning proved transitory after feedback was withdrawn (Experiment 7). Theoretical implications are discussed, and we argue that fading should have practical utility in naturalistic category learning tasks, which involve extremely high dimensional stimuli and many irrelevant dimensions. PsycINFO Database Record (c) 2013 APA, all rights reserved.
Fading and shadowing in wireless systems
Shankar, P Mohana
2017-01-01
This book offers a comprehensive overview of fading and shadowing in wireless channels. A number of statistical models including simple, hybrid, compound and cascaded ones are presented along with a detailed discussion of diversity techniques employed to mitigate the effects of fading and shadowing. The effects of co-channel interference before and after the implementation of diversity are also analyzed. To facilitate easy understanding of the models and the analysis, the background on probability and random variables is presented with relevant derivations of densities of the sums, products, ratios as well as order statistics of random variables. The book also provides material on digital modems of interest in wireless systems. The updated edition expands the background materials on probability by offering sections on Laplace and Mellin transforms, parameter estimation, statistical testing and receiver operating characteristics. Newer models for fading, shadowing and shadowed fading are included along with th...
Fading and interference mitigation in wireless communications
Panic, Stefan; Anastasov, Jelena; Spalevic, Petar
2013-01-01
The rapid advancement of various wireless communication system services has created the need to analyze the possibility of their performance improvement. Introducing the basic principles of digital communications performance analysis and its mathematical formalization, Fading and Interference Mitigation in Wireless Communications will help you stay up to date with recent developments in the performance analysis of space diversity reception over fading channels in the presence of cochannel interference.The book presents a unified method for computing the performance of digital communication sys
Performance analysis of selective cooperation with fixed gain relays in Nakagami-m channels
Hussain, Syed Imtiaz; Hasna, Mazen Omar; Alouini, Mohamed-Slim
2012-01-01
Selecting the best relay using the maximum signal to noise ratio (SNR) among all the relays ready to cooperate saves system resources and utilizes the available bandwidth more efficiently compared to the regular all-relay cooperation. In this paper, we analyze the performance of the best relay selection scheme with fixed gain relays operating in Nakagami-. m channels. We first derive the probability density function (PDF) of upper bounded end-to-end SNR of the relay link. Using this PDF, we derive some key performance parameters for the system including average bit error probability and average channel capacity. The analytical results are verified through Monte Carlo simulations. © 2012 Elsevier B.V.
Performance analysis of selective cooperation with fixed gain relays in Nakagami-m channels
Hussain, Syed Imtiaz
2012-09-01
Selecting the best relay using the maximum signal to noise ratio (SNR) among all the relays ready to cooperate saves system resources and utilizes the available bandwidth more efficiently compared to the regular all-relay cooperation. In this paper, we analyze the performance of the best relay selection scheme with fixed gain relays operating in Nakagami-. m channels. We first derive the probability density function (PDF) of upper bounded end-to-end SNR of the relay link. Using this PDF, we derive some key performance parameters for the system including average bit error probability and average channel capacity. The analytical results are verified through Monte Carlo simulations. © 2012 Elsevier B.V.
Fading Characteristics of Wireless Channel on High-Speed Railway in Hilly Terrain Scenario
Directory of Open Access Journals (Sweden)
Fengyu Luan
2013-01-01
Full Text Available This paper focuses on the fading characteristics of wireless channel on High-Speed Railway (HSR in hilly terrain scenario. Due to the rapid speed, the fading characteristics of HSR channel are highly correlated with time or Transmit-Receive distance and have their own special property. To investigate the fading characteristics, the measurement is conducted on the Guangzhou-Shenzhen passenger-dedicated line in China with the speed of 295 km/h in the data-collection area at 2.4 GHz. From the measured data, the amplitude of each path is estimated by using the Subspace-Alternating Generalized Expectation-Maximization (SAGE algorithm along with other parameters of channel impulse responses. Then the fading parameters, including path loss, shadow fading, and K-factor, are analysed. With the numerical results in the measurement and analysis, the fading characteristics have been revealed and modelled. It is supposed that this work has a promotion for HSR communication system design and improvement.
On the MIMO Capacity for Distributed System under Composite Rayleigh/Rician Fading and Shadowing
Directory of Open Access Journals (Sweden)
Santiago González-Aurioles
2015-01-01
Full Text Available Wireless channels are commonly affected by short-term fading and long-term fading (shadowing. The shadowing effects must be taken into account also when mobility is present in the wireless scenario. Using a composite fading model, the total channel capacity can be studied for a scenario with short-term Rayleigh fading along with shadowing. This work provides quantitative results for these kinds of scenarios with Rayleigh fading and shadowing, considering also multiple-input and multiple-output systems, which have not been previously reported. In addition, the channel capacity has been studied in depth in its relation with the shadowing level, signal to noise ratio, and the number of elements in the multiple-input and multiple-output system. Moreover, the channel performance with shadowing has been compared to the one without it. Furthermore, Rician model with shadowing is studied and its results are reported. In addition, correlated and experimental results are provided. It is identified that the distributed MIMO systems can benefit from shadowing in Rician channels. This advantage has not been reported previously. This type of fading is proposed for massive MIMO by others and our results open the door to emulate massive MIMO on a reverberation chamber.
Wireless Energy Harvesting Using Signals from Multiple Fading Channels
Chen, Yunfei; Zhao, Nan; Alouini, Mohamed-Slim
2017-01-01
fading or Gamma-shadowed Rician fading. The received signals are then harvested by using either a single harvester for simultaneous transmissions or multiple harvesters for transmissions at different frequencies, antennas or time slots. Both linear
Space-Time Trellis Coded 8PSK Schemes for Rapid Rayleigh Fading Channels
Directory of Open Access Journals (Sweden)
Salam A. Zummo
2002-05-01
Full Text Available This paper presents the design of 8PSK space-time (ST trellis codes suitable for rapid fading channels. The proposed codes utilize the design criteria of ST codes over rapid fading channels. Two different approaches have been used. The first approach maximizes the symbol-wise Hamming distance (HD between signals leaving from or entering to the same encoderÃ¢Â€Â²s state. In the second approach, set partitioning based on maximizing the sum of squared Euclidean distances (SSED between the ST signals is performed; then, the branch-wise HD is maximized. The proposed codes were simulated over independent and correlated Rayleigh fading channels. Coding gains up to 4 dB have been observed over other ST trellis codes of the same complexity.
Classification of breast masses in ultrasonic B scans using Nakagami and K distributions
International Nuclear Information System (INIS)
Shankar, P M; Dumane, Vishruta A; George, Thomas; Piccoli, Catherine W; Reid, John M; Forsberg, Flemming; Goldberg, Barry B
2003-01-01
Classification of breast masses in greyscale ultrasound images is undertaken using a multiparameter approach. Five parameters reflecting the non-Rayleigh nature of the backscattered echo were used. These parameters, based mostly on the Nakagami and K distributions, were extracted from the envelope of the echoes at the site, boundary, spiculated region and shadow of the mass. They were combined to create a linear discriminant. The performance of this discriminant for the classification of breast masses was studied using a data set consisting of 70 benign and 29 malignant cases. The A z value for the discriminant was 0.96 ± 0.02, showing great promise in the classification of masses into benign and malignant ones. The discriminant was combined with the level of suspicion values of the radiologist leading to an A z value of 0.97 ± 0.014. The parameters used here can be calculated with minimal clinical intervention, so the method proposed here may therefore be easily implemented in an automated fashion. These results also support the recent reports suggesting that ultrasound may help as an adjunct to mammography in breast cancer diagnostics to enhance the classification of breast masses
Schmidt, Barnet Michael
An optimal performance monitoring metric for a hybrid free space optical and radio-frequency (RF) wireless network, the Outage Capacity Objective Function, is analytically developed and studied. Current and traditional methods of performance monitoring of both optical and RF wireless networks are centered on measurement of physical layer parameters, the most common being signal-to-noise ratio, error rate, Q factor, and eye diagrams, occasionally combined with link-layer measurements such as data throughput, retransmission rate, and/or lost packet rate. Network management systems frequently attempt to predict or forestall network failures by observing degradations of these parameters and to attempt mitigation (such as offloading traffic, increasing transmitter power, reducing the data rate, or combinations thereof) prior to the failure. These methods are limited by the frequent low sensitivity of the physical layer parameters to the atmospheric optical conditions (measured by optical signal-to-noise ratio) and the radio frequency fading channel conditions (measured by signal-to-interference ratio). As a result of low sensitivity, measurements of this type frequently are unable to predict impending failures sufficiently in advance for the network management system to take corrective action prior to the failure. We derive and apply an optimal measure of hybrid network performance based on the outage capacity of the hybrid optical and RF channel, the outage capacity objective function. The objective function provides high sensitivity and reliable failure prediction, and considers both the effects of atmospheric optical impairments on the performance of the free space optical segment as well as the effect of RF channel impairments on the radio frequency segment. The radio frequency segment analysis considers the three most common RF channel fading statistics: Rayleigh, Ricean, and Nakagami-m. The novel application of information theory to the underlying physics of the
Asymptotic analysis of downlink MISO systems over Rician fading channels
Falconet, Hugo
2016-06-24
In this work, we focus on the ergodic sum rate in the downlink of a single-cell large-scale multi-user MIMO system in which the base station employs N antennas to communicate with K single-antenna user equipments. A regularized zero-forcing (RZF) scheme is used for precoding under the assumption that each link forms a spatially correlated MIMO Rician fading channel. The analysis is conducted assuming N and K grow large with a non trivial ratio and perfect channel state information is available at the base station. Recent results from random matrix theory and large system analysis are used to compute an asymptotic expression of the signal-to-interference-plus-noise ratio as a function of the system parameters, the spatial correlation matrix and the Rician factor. Numerical results are used to evaluate the performance gap in the finite system regime under different operating conditions. © 2016 IEEE.
Asymptotic analysis of downlink MISO systems over Rician fading channels
Falconet, Hugo; Sanguinetti, Luca; Kammoun, Abla; Debbah, Merouane
2016-01-01
In this work, we focus on the ergodic sum rate in the downlink of a single-cell large-scale multi-user MIMO system in which the base station employs N antennas to communicate with K single-antenna user equipments. A regularized zero-forcing (RZF) scheme is used for precoding under the assumption that each link forms a spatially correlated MIMO Rician fading channel. The analysis is conducted assuming N and K grow large with a non trivial ratio and perfect channel state information is available at the base station. Recent results from random matrix theory and large system analysis are used to compute an asymptotic expression of the signal-to-interference-plus-noise ratio as a function of the system parameters, the spatial correlation matrix and the Rician factor. Numerical results are used to evaluate the performance gap in the finite system regime under different operating conditions. © 2016 IEEE.
Monocular depth effects on perceptual fading.
Hsu, Li-Chuan; Kramer, Peter; Yeh, Su-Ling
2010-08-06
After prolonged viewing, a static target among moving non-targets is perceived to repeatedly disappear and reappear. An uncrossed stereoscopic disparity of the target facilitates this Motion-Induced Blindness (MIB). Here we test whether monocular depth cues can affect MIB too, and whether they can also affect perceptual fading in static displays. Experiment 1 reveals an effect of interposition: more MIB when the target appears partially covered by, than when it appears to cover, its surroundings. Experiment 2 shows that the effect is indeed due to interposition and not to the target's contours. Experiment 3 induces depth with the watercolor illusion and replicates Experiment 1. Experiments 4 and 5 replicate Experiments 1 and 3 without the use of motion. Since almost any stimulus contains a monocular depth cue, we conclude that perceived depth affects perceptual fading in almost any stimulus, whether dynamic or static. Copyright 2010 Elsevier Ltd. All rights reserved.
Fading and Shadowing in Wireless Systems
Shankar, P Mohana
2012-01-01
In recent decades, growth in the field of wireless communications has led to an exponential rise in the number of journals catering to the research community. Still unmet, however, is the need to fully and comprehensively understand the effects of channel degradation brought on by the statistical fluctuations in the channel. These fluctuations mainly manifest as variations in signal power observed in the channel generally modeled using a variety of probability distributions, both in straight forms as well as in compound forms. While the former might explain some of the effects, it is the latter, namely, the compound models, which incorporate both short term and long term power fluctuations in the channel, explain the much more complex nature of the signals in these channels. Fading and Shadowing in Wireless Systems offers a pedagogical approach to the topic, with insight into the modeling and analysis of fading and shadowing. Beginning with statistical background and digital communications, the book is formul...
On Capacity of the Writing onto Fast Fading Dirt Channel
Rini, Stefano; Shamai, Shlomo
2016-01-01
The "Writing onto Fast Fading Dirt" (WFFD) channel is investigated to study the effects of partial channel knowledge on the capacity of the "writing on dirty paper" channel. The WFFD channel is the Gel'fand-Pinsker channel in which the output is obtained as the sum of the input, white Gaussian noise and a fading-times-state term. The fading-times-state term is equal to the element-wise product of the channel state sequence, known only at the transmitter, and a fast fading process, known only ...
International Nuclear Information System (INIS)
Auger, Jean-Claude; McLoughlin, Daragh
2017-01-01
We study the color fading of paints films composed of mixtures of white rutile titanium dioxide and yellow arylide pigments dispersed in two polymer binders at different volume concentrations. The samples were exposed to ultraviolet radiations in an accelerated weathering tester during three weeks. The measured patterns in color variations appeared to be independent of the chemistry of the binders. We then developed a theoretical framework, based on the Radiative transfer Equation of light and the One Particle T-Matrix formalism to simulate the color fading process. The loss of color is correlated to the progressive decrease of the original colored pigment volume-filling fraction as the destructive UV radiations penetrate deeper into the films. The calculated patterns of color variations of paints film composed by mixtures of white pigments with yellow Cadmium Sulfate (CdS) and red Cerium Sulfide (Ce_2S_3) pigments showed the same trend as that seen experimentally. - Highlights: • Theoretical framework to simulate color-fading process of paints. • Good comparison between simulation and experimental data. • Color Fading depends on total amount of perceptible pigments.
Computer models for fading channels with applications to digital transmission
Loo, Chun; Secord, Norman
1991-11-01
The authors describe computer models for Rayleigh, Rician, log-normal, and land-mobile-satellite fading channels. All computer models for the fading channels are based on the manipulation of a white Gaussian random process. This process is approximated by a sum of sinusoids with random phase angle. These models compare very well with analytical models in terms of their probability distribution of envelope and phase of the fading signal. For the land mobile satellite fading channel, results of level crossing rate and average fade duration are given. These results show that the computer models can provide a good coarse estimate of the time statistic of the faded signal. Also, for the land-mobile-satellite fading channel, the results show that a 3-pole Butterworth shaping filter should be used with the model. An example of the application of the land-mobile-satellite fading-channel model to predict the performance of a differential phase-shift keying signal is described.
Flash-induced fading: Dependence on colour and shape similarity
Vergeer, M.L.T.; Lier, R.J. van
2005-01-01
We investigated the effects of perceptual grouping by colour and shape similarity on flash-induced perceptual fading. This flash-induced fading effect (Kanai et al, 2003 Journal of Cognitive Neuroscience 15 664 - 672) is considered as a time-locked variant of the Troxler effect. In the original
Autonomous detection of ISO fade point with color laser printers
Yan, Ni; Maggard, Eric; Fothergill, Roberta; Jessome, Renee J.; Allebach, Jan P.
2015-01-01
Image quality assessment is a very important field in image processing. Human observation is slow and subjective, it also requires strict environment setup for the psychological test 1. Thus developing algorithms to match desired human experiments is always in need. Many studies have focused on detecting the fading phenomenon after the materials are printed, that is to monitor the persistence of the color ink 2-4. However, fading is also a common artifact produced by printing systems when the cartridges run low. We want to develop an automatic system to monitor cartridge life and report fading defects when they appear. In this paper, we first describe a psychological experiment that studies the human perspective on printed fading pages. Then we propose an algorithm based on Color Space Projection and K-means clustering to predict the visibility of fading defects. At last, we integrate the psychological experiment result with our algorithm to give a machine learning tool that monitors cartridge life.
Hussain, Syed Imtiaz; Alouini, Mohamed-Slim; Hasna, Mazen Omar
2011-01-01
In cooperative communications, multiple relays between a source and a destination can increase the diversity gain. Because all the nodes must use orthogonal channels, multiple-relay cooperation becomes spectrally inefficient. Therefore, a bestrelay selection scheme was recently proposed. In this paper, we analyzed the performance of this scheme for a system with the relays operating in amplify-and-forward mode over identical Nakagami-m channels using an exact source-relay-destination signal-to-noise ratio (SNR).We derived accurate closed-form expressions for various system parameters including the probability density function of end-to-end SNR, the average output SNR, the bit error probability, and the channel capacity. The analytical results were verified through Monte Carlo simulations. Copyright © 2011 John Wiley & Sons, Ltd.
Hussain, Syed Imtiaz
2011-05-02
In cooperative communications, multiple relays between a source and a destination can increase the diversity gain. Because all the nodes must use orthogonal channels, multiple-relay cooperation becomes spectrally inefficient. Therefore, a bestrelay selection scheme was recently proposed. In this paper, we analyzed the performance of this scheme for a system with the relays operating in amplify-and-forward mode over identical Nakagami-m channels using an exact source-relay-destination signal-to-noise ratio (SNR).We derived accurate closed-form expressions for various system parameters including the probability density function of end-to-end SNR, the average output SNR, the bit error probability, and the channel capacity. The analytical results were verified through Monte Carlo simulations. Copyright © 2011 John Wiley & Sons, Ltd.
Fade detector for the FODA-TDMA access scheme
Celandroni, Nedo; Ferro, Erina; Marzoli, Antonio
1989-05-01
The First in first out Ordered Demand Assignment-Time Division Multiple Access (FODA-TDMA) satellite access scheme designed for simultaneous transmissions of real time data, like packetized voice and slow-scan images (stream traffic) and data coming from standard EDP applications, such as bulk data tansfer, interactive computer access, mailing, data base enquiry and updating (datagram traffic) is described. When deep fades are experienced due to rain attenuation, the system is able to counter the fade. Techniques to detect the fade are presented.
Modeling of Non-WSSUS Double-Rayleigh Fading Channels for Vehicular Communications
Directory of Open Access Journals (Sweden)
Carlos A. Gutiérrez
2017-01-01
Full Text Available This paper deals with the modeling of nonstationary time-frequency (TF dispersive multipath fading channels for vehicle-to-vehicle (V2V communication systems. As a main contribution, the paper presents a novel geometry-based statistical channel model that facilitates the analysis of the nonstationarities of V2V fading channels arising at a small-scale level due to the time-varying nature of the propagation delays. This new geometrical channel model has been formulated following the principles of plane wave propagation (PWP and assuming that the transmitted signal reaches the receiver antenna through double interactions with multiple interfering objects (IOs randomly located in the propagation area. As a consequence of such interactions, the first-order statistics of the channel model’s envelope are shown to follow a worse-than-Rayleigh distribution; specifically, they follow a double-Rayleigh distribution. General expressions are derived for the envelope and phase distributions, four-dimensional (4D TF correlation function (TF-CF, and TF-dependent delay and Doppler profiles of the proposed channel model. Such expressions are valid regardless of the underlying geometry of the propagation area. Furthermore, a closed-form solution of the 4D TF-CF is presented for the particular case of the geometrical two-ring scattering model. The obtained results provide new theoretical insights into the correlation and spectral properties of small-scale nonstationary V2V double-Rayleigh fading channels.
Performance analysis of power-efficient adaptive interference cancelation in fading channels
Radaydeh, Redha Mahmoud Mesleh; Alouini, Mohamed-Slim
2010-01-01
This paper analyzes the performance of a -steering scheme for highly correlated receive antennas in the presence of statistically unordered co-channel interferers over multipath fading channels. An adaptive activation of receive antennas according to the interfering signals fading conditions is considered in the analysis. Analytical expressions for various system performance measures, including the outage probability, average error probability of different signaling schemes, and raw moments of the combined signal-to-interference-plus-noise ratio (SINR) are obtained in exact forms. Numerical and simulation results for the performance-complexity tradeoff of this scheme is presented and then compared with that of full-size arbitrary interference cancelation and no cancelation scenarios. ©2010 IEEE.
Performance analysis of power-efficient adaptive interference cancelation in fading channels
Radaydeh, Redha Mahmoud Mesleh
2010-12-01
This paper analyzes the performance of a -steering scheme for highly correlated receive antennas in the presence of statistically unordered co-channel interferers over multipath fading channels. An adaptive activation of receive antennas according to the interfering signals fading conditions is considered in the analysis. Analytical expressions for various system performance measures, including the outage probability, average error probability of different signaling schemes, and raw moments of the combined signal-to-interference-plus-noise ratio (SINR) are obtained in exact forms. Numerical and simulation results for the performance-complexity tradeoff of this scheme is presented and then compared with that of full-size arbitrary interference cancelation and no cancelation scenarios. ©2010 IEEE.
Directory of Open Access Journals (Sweden)
Machiko Ishikawa
2011-12-01
Full Text Available The aim of this thesis is to give a post-colonial reading of selected narratives by Nakagami Kenji (1946-1992. Nakagami was the first Akutagawa Prize winning novelist from Japan’s outcaste Burakumin group. Through the production of narrative about this subaltern community, Nakagami confronted the exclusionary systems of hegemonic Japanese thought and the structures created by these systems which deny the principle and lived experience of ‘difference’. Borrowing the post-colonial concept of ‘writing back’ to the hegemonic centre from the work of Bill Ashcroft, Gareth Griffiths and Helen Tiffin’s The Empire Writes Back, this article will analyse Nakagami’s ‘Misaki’ (1976, The Cape, and its sequel, Karekinada (1977, The Sea of Withered Trees. The principal focus will be on Nakagami’s representation of the hidden voice of those on the margins of Japanese society. This approach will position the Burakumin as ‘subalterns’ to the mainstream Japanese society on the basis of Antonio Gramsci’s view of the group. The analysis of ‘Misaki’ and Karekinada will begin with an investigation of Kishū Kumano as a site on the margins of mainstream Japanese society. In analysing these two novels as subaltern narratives, close attention will be given to Nakagami’s use of intertextuality particularly with oral kishu ryūritan folklore.
OPRA capacity bounds for selection diversity over generalized fading channels
Hanif, Muhammad Fainan; Yang, Hongchuan; Alouini, Mohamed-Slim
2014-01-01
, lower and upper bounds on OPRA capacity for selection diversity scheme are presented. These bounds hold for variety of fading channels including log-normal and generalized Gamma distributed models and have very simple analytic expressions for easy
Efficient incremental relaying for packet transmission over fading channels
Fareed, Muhammad Mehboob; Alouini, Mohamed-Slim; Yang, Hongchuan
2014-01-01
In this paper, we propose a novel relaying scheme for packet transmission over fading channels, which improves the spectral efficiency of cooperative diversity systems by utilizing limited feedback from the destination. Our scheme capitalizes
An Automated Fading Procedure to Alter Sexual Responsiveness in Pedophiles
Laws, D. R.; Pawlowski, A. V.
1975-01-01
An automated stimulus fading procedure was used to strengthen sexual responsiveness to adult stimuli in two pedophiles. The degree of responsiveness was indicated by changes in the penile response. Implications for future research are discussed. (Author)
An overview of turbo decoding on fading channels
ATILGAN, Doğan
2009-01-01
A review of turbo coding and decoding has been presented in the literature [1]. In that paper, turbo coding and decoding on AWGN (Additive White Gaussian Noise) channels has been elaborated. In wireless communications, a phenomennon called multipath fading is frequently encountered. Therefore, investigation of efficient techniques to tackle with the destructive effects of fading is essential. Turbo coding has been proven as an efficient channel coding technique for AWGN channels. Some of the ...
Analysis of multipath channel fading techniques in wireless communication systems
Mahender, Kommabatla; Kumar, Tipparti Anil; Ramesh, K. S.
2018-04-01
Multipath fading occurs in any environment where there is multipath propagation and there is some movement of elements within the radio communications system. This may include the radio transmitter or receiver position, or in the elements that give rise to the reflections. The multipath fading can often be relatively deep, i.e. the signals fade completely away, whereas at other times the fading may not cause the signal to fall below a useable strength. Multipath fading may also cause distortion to the radio signal. As the various paths that can be taken by the signals vary in length, the signal transmitted at a particular instance will arrive at the receiver over a spread of times. This can cause problems with phase distortion and inter symbol interference when data transmissions are made. As a result, it may be necessary to incorporate features within the radio communications system that enables the effects of these problems to be minimized. This paper analyses the effects of various types of multipath fading in wireless transmission system.
A new simple model for composite fading channels: Second order statistics and channel capacity
Yilmaz, Ferkan
2010-09-01
In this paper, we introduce the most general composite fading distribution to model the envelope and the power of the received signal in such fading channels as millimeter wave (60 GHz or above) fading channels and free-space optical channels, which we term extended generalized-K (EGK) composite fading distribution. We obtain the second-order statistics of the received signal envelope characterized by the EGK composite fading distribution. Expressions for probability density function, cumulative distribution function, level crossing rate and average fade duration, moments, amount of fading and average capacity are derived. Numerical and computer simulation examples validate the accuracy of the presented mathematical analysis. © 2010 IEEE.
Earth-Space Links and Fade-Duration Statistics
Davarian, Faramaz
1996-01-01
In recent years, fade-duration statistics have been the subject of several experimental investigations. A good knowledge of the fade-duration distribution is important for the assessment of a satellite communication system's channel dynamics: What is a typical link outage duration? How often do link outages exceeding a given duration occur? Unfortunately there is yet no model that can universally answer the above questions. The available field measurements mainly come from temperate climatic zones and only from a few sites. Furthermore, the available statistics are also limited in the choice of frequency and path elevation angle. Yet, much can be learned from the available information. For example, we now know that the fade-duration distribution is approximately lognormal. Under certain conditions, we can even determine the median and other percentiles of the distribution. This paper reviews the available data obtained by several experimenters in different parts of the world. Areas of emphasis are mobile and fixed satellite links. Fades in mobile links are due to roadside-tree shadowing, whereas fades in fixed links are due to rain attenuation.
Rain Fade Compensation for Ka-Band Communications Satellites
Mitchell, W. Carl; Nguyen, Lan; Dissanayake, Asoka; Markey, Brian; Le, Anh
1997-01-01
This report provides a review and evaluation of rain fade measurement and compensation techniques for Ka-band satellite systems. This report includes a description of and cost estimates for performing three rain fade measurement and compensation experiments. The first experiment deals with rain fade measurement techniques while the second one covers the rain fade compensation techniques. The third experiment addresses a feedback flow control technique for the ABR service (for ATM-based traffic). The following conclusions were observed in this report; a sufficient system signal margin should be allocated for all carriers in a network, that is a fixed clear-sky margin should be typically in the range of 4-5 dB and should be more like 15 dB in the up link for moderate and heavy rain zones; to obtain a higher system margin it is desirable to combine the uplink power control technique with the technique that implements the source information rate and FEC code rate changes resulting in a 4-5 dB increase in the dynamic part of the system margin. The experiments would assess the feasibility of the fade measurements and compensation techniques, and ABR feedback control technique.
Hussain, Syed Imtiaz
2010-06-01
In cooperative communication networks, the use of multiple relays between the source and the destination was proposed to increase the diversity gain. Since the source and all the relays must transmit on orthogonal channels, multiple relay cooperation is considered inefficient in terms of channel resources and bandwidth utilization. To overcome this problem, the concept of best relay selection was recently proposed. In this paper, we analyze the performance of the best relay selection scheme for a cooperative network with multiple relays operating in amplify-and-forward (AF) mode over identical Nakagami-m channels using exact source-relay-destination signal to noise ratio (SNR) expression. We derive accurate closed form expressions for various system parameters including probability density function (pdf) of end-to-end SNR, average output SNR, average probability of bit error and average channel capacity. T he analytical results are verified through extensive simulations. It is shown that the best relay selection scheme performs better than the regular all relay cooperation.
Optimum Combining for Rapidly Fading Channels in Ad Hoc Networks
Directory of Open Access Journals (Sweden)
Sonia Furman
2003-10-01
Full Text Available Research and technology in wireless communication systems such as radar and cellular networks have successfully implemented alternative design approaches that utilize antenna array techniques such as optimum combining, to mitigate the degradation effects of multipath in rapid fading channels. In ad hoc networks, these methods have not yet been exploited primarily due to the complexity inherent in the network's architecture. With the high demand for improved signal link quality, devices configured with omnidirectional antennas can no longer meet the growing need for link quality and spectrum efficiency. This study takes an empirical approach to determine an optimum combining antenna array based on 3 variants of interelement spacing. For rapid fading channels, the simulation results show that the performance in the network of devices retrofitted with our antenna arrays consistently exceeded those with an omnidirectional antenna. Further, with the optimum combiner, the performance increased by over 60% compared to that of an omnidirectional antenna in a rapid fading channel.
A Novel Simulation Model for Nonstationary Rice Fading Channels
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Kaili Jiang
2018-01-01
Full Text Available In this paper, we propose a new simulator for nonstationary Rice fading channels under nonisotropic scattering scenarios, as well as the improved computation method of simulation parameters. The new simulator can also be applied on generating Rayleigh fading channels by adjusting parameters. The proposed simulator takes into account the smooth transition of fading phases between the adjacent channel states. The time-variant statistical properties of the proposed simulator, that is, the probability density functions (PDFs of envelope and phase, autocorrelation function (ACF, and Doppler power spectrum density (DPSD, are also analyzed and derived. Simulation results have demonstrated that our proposed simulator provides good approximation on the statistical properties with the corresponding theoretical ones, which indicates its usefulness for the performance evaluation and validation of the wireless communication systems under nonstationary and nonisotropic scenarios.
Fast Faraday fading of long range satellite signals.
Heron, M. L.
1972-01-01
20 MHz radio signals have been received during the day from satellite Beacon-B when it was below the optical horizon by using a bank of narrow filters to improve the signal to noise ratio. The Faraday fading rate becomes constant, under these conditions, at a level determined by the plasma frequency just below the F-layer peak. Variations in the Faraday fading rate reveal fluctuations in the electron density near the peak, while the rate of attaining the constant level depends on the shape of the electron density profile.
Modeling and Simulation of MIMO Mobile-to-Mobile Wireless Fading Channels
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Gholamreza Bakhshi
2012-01-01
Full Text Available Analysis and design of multielement antenna systems in mobile fading channels require a model for the space-time cross-correlation among the links of the underlying multipleinput multiple-output (MIMO Mobile-to-Mobile (M-to-M communication channels. In this paper, we propose the modified geometrical two-ring model, a MIMO channel reference model for M-to-M communication systems. This model is based on the extension of single-bounce two-ring scattering model for flat fading channel under the assumption that the transmitter and the receiver are moving. Assuming single-bounce scattering model in both isotropic and nonisotropic environment, a closed-form expression for the space-time cross-correlation function (CCF between any two subchannels is derived. The proposed model provides an important framework in M-to-M system design, where includes many existing correlation models as special cases. Also, two realizable statistical simulation models are proposed for simulating both isotropic and nonisotropic reference model. The realizable simulation models are based on Sum-of-Sinusoids (SoS simulation model. Finally, the correctness of the proposed simulation models is shown via different simulation scenarios.
Ansari, Imran Shafique
2010-01-01
The introduction of new schemes that are based on the communication among nodes has motivated the use of composite fading models due to the fact that the nodes experience different multipath fading and shadowing statistics, which subsequently
Wireless Energy Harvesting Using Signals from Multiple Fading Channels
Chen, Yunfei
2017-08-01
In this paper, we study the average, the probability density function and the cumulative distribution function of the harvested power. In the study, the signals are transmitted from multiple sources. The channels are assumed to be either Rician fading or Gamma-shadowed Rician fading. The received signals are then harvested by using either a single harvester for simultaneous transmissions or multiple harvesters for transmissions at different frequencies, antennas or time slots. Both linear and nonlinear models for the energy harvester at the receiver are examined. Numerical results are presented to show that, when a large amount of harvested power is required, a single harvester or the linear range of a practical nonlinear harvester are more efficient, to avoid power outage. Further, the power transfer strategy can be optimized for fixed total power. Specifically, for Rayleigh fading, the optimal strategy is to put the total power at the source with the best channel condition and switch off all other sources, while for general Rician fading, the optimum magnitudes and phases of the transmitting waveforms depend on the channel parameters.
Further investigations on 'non-fading' in K-Feldspar
DEFF Research Database (Denmark)
Jain, Mayank; Buylaert, Jan-Pieter; Thomsen, Kristina Jørkov
2015-01-01
, suggesting that the higher the stimulation temperature in post IR-IRSL methods, the greater the ability to access distant electron hole pairs. We further find that the delayed off-time signal in time-resolved IRSL has immense potential for sampling non-fading signal and should be explored further...
Physical Layer Design in Wireless Sensor Networks for Fading Mitigation
Directory of Open Access Journals (Sweden)
Nuo Chen
2013-09-01
Full Text Available This paper presents the theoretical analysis, simulation results and suggests design in digital technology of a physical layer for wireless sensor networks. The proposed design is able to mitigate fading inside communication channel. To mitigate fading the chip interleaving technique is proposed. For the proposed theoretical model of physical layer, a rigorous mathematical analysis is conducted, where all signals are presented and processed in discrete time domain form which is suitable for further direct processing necessary for devices design in digital technology. Three different channels are used to investigate characteristics of the physical layer: additive white Gaussian noise channel (AWGN, AWG noise and flat fading channel and AWG noise and flat fading channel with interleaver and deinterleaver blocks in the receiver and transmitter respectively. Firstly, the mathematical model of communication system representing physical layer is developed based on the discrete time domain signal representation and processing. In the existing theory, these signals and their processing are represented in continuous time form, which is not suitable for direct implementation in digital technology. Secondly, the expressions for the probability of chip, symbol and bit error are derived. Thirdly, the communication system simulators are developed in MATLAB. The simulation results confirmed theoretical findings.
Hard Fusion Based Spectrum Sensing over Mobile Fading Channels in Cognitive Vehicular Networks.
Qian, Xiaomin; Hao, Li; Ni, Dadong; Tran, Quang Thanh
2018-02-06
An explosive growth in vehicular wireless applications gives rise to spectrum resource starvation. Cognitive radio has been used in vehicular networks to mitigate the impending spectrum starvation problem by allowing vehicles to fully exploit spectrum opportunities unoccupied by licensed users. Efficient and effective detection of licensed user is a critical issue to realize cognitive radio applications. However, spectrum sensing in vehicular environments is a very challenging task due to vehicle mobility. For instance, vehicle mobility has a large effect on the wireless channel, thereby impacting the detection performance of spectrum sensing. Thus, gargantuan efforts have been made in order to analyze the fading properties of mobile radio channel in vehicular environments. Indeed, numerous studies have demonstrated that the wireless channel in vehicular environments can be characterized by a temporally correlated Rayleigh fading. In this paper, we focus on energy detection for spectrum sensing and a counting rule for cooperative sensing based on Neyman-Pearson criteria. Further, we go into the effect of the sensing and reporting channel conditions on the sensing performance under the temporally correlated Rayleigh channel. For local and cooperative sensing, we derive some alternative expressions for the average probability of misdetection. The pertinent numerical and simulating results are provided to further validate our theoretical analyses under a variety of scenarios.
A new simple model for composite fading channels: Second order statistics and channel capacity
Yilmaz, Ferkan; Alouini, Mohamed-Slim
2010-01-01
In this paper, we introduce the most general composite fading distribution to model the envelope and the power of the received signal in such fading channels as millimeter wave (60 GHz or above) fading channels and free-space optical channels, which
Directory of Open Access Journals (Sweden)
Amit Grover
2014-08-01
Full Text Available The reliable services along with high throughput can be achieved by using wireless communication systems. These systems also provides a wide coverage because of their features, no doubt MIMO Communication System [1] is one among them. Features provided by these systems ensure the improved system coverage and increased data transmission rate by considering multiple numbers of transmitter and receiver antennas. In this article, the concept of equalization has been considered and finally the performance of the MIMO Systems in Rician flat fading [5] channel is compared with the Rayleigh flat fading channel. It has also been observed that the performance of these Systems in Rician Flat Fading Channel is the best as compare to the Rayleigh Flat Fading Channel [10]. It has been concluded that the successive interference methods provide better performance as compare to others, but their complexity is high. Simulation results shows that ML provides the better performance in comparison to other equalizers but Sphere decoder provides the best performance.
Yilmaz, Ferkan
2012-12-01
The higher-order statistics (HOS) of the channel capacity μn=E[logn (1+γ end)], where n ∈ N denotes the order of the statistics, has received relatively little attention in the literature, due in part to the intractability of its analysis. In this letter, we propose a novel and unified analysis, which is based on the moment generating function (MGF) technique, to exactly compute the HOS of the channel capacity. More precisely, our mathematical formalism can be readily applied to maximal-ratio-combining (MRC) receivers operating in generalized fading environments. The mathematical formalism is illustrated by some numerical examples focusing on the correlated generalized fading environments. © 2012 IEEE.
Directory of Open Access Journals (Sweden)
A. B. Bhattacharya
1998-02-01
Full Text Available The records of VLF atmospherics over Calcutta and then over Kalyani (West Bengal during the torrential rainfall, caused by violent monsoon and post-monsoon depressions, exhibit distinct long-period fadings both at day and night. Interesting results obtained from an analysis of round-the-clock atmospherics data and associated meteorological parameters are reported in this paper. A possible correlation between the severe meteorological activity with the solar geophysical phenomena was studied. The results are indicative of an interesting sequence of solar-terrestrial events. A tentative conclusion is reached, suggesting an origin of the fading from atmospheric gravity waves generated in the centre of activity of the depressions concerned.Key words. Meteorology and atmospheric dynamics · Lightning · Precipitation
Yilmaz, Ferkan; Alouini, Mohamed-Slim
2012-01-01
The higher-order statistics (HOS) of the channel capacity μn=E[logn (1+γ end)], where n ∈ N denotes the order of the statistics, has received relatively little attention in the literature, due in part to the intractability of its analysis. In this letter, we propose a novel and unified analysis, which is based on the moment generating function (MGF) technique, to exactly compute the HOS of the channel capacity. More precisely, our mathematical formalism can be readily applied to maximal-ratio-combining (MRC) receivers operating in generalized fading environments. The mathematical formalism is illustrated by some numerical examples focusing on the correlated generalized fading environments. © 2012 IEEE.
Directory of Open Access Journals (Sweden)
Yoshio Karasawa
2017-01-01
Full Text Available We present four new developments for a multiple-input multiple-output (MIMO over-the-air measurement system based on our previous studies. The first two developments relate to the channel model for multipath environment generation. One is a further simplification of the circuit configuration without performance degradation by reducing the number of delay generation units, which dominate the performance limit when implementing the circuit on a field-programmable gate array (FPGA. The other is to realize spatial correlation characteristics among the input ports on the transmission side, whereas the previously proposed channel model did not consider this correlation. The third development involves the details of implementing the MIMO fading emulator on an FPGA as a two-stage scheme. The fourth is the demonstration of application examples of the developed system.
Radio resource allocation over fading channels under statistical delay constraints
Le-Ngoc, Tho
2017-01-01
This SpringerBrief presents radio resource allocation schemes for buffer-aided communications systems over fading channels under statistical delay constraints in terms of upper-bounded average delay or delay-outage probability. This Brief starts by considering a source-destination communications link with data arriving at the source transmission buffer. The first scenario, the joint optimal data admission control and power allocation problem for throughput maximization is considered, where the source is assumed to have a maximum power and an average delay constraints. The second scenario, optimal power allocation problems for energy harvesting (EH) communications systems under average delay or delay-outage constraints are explored, where the EH source harvests random amounts of energy from renewable energy sources, and stores the harvested energy in a battery during data transmission. Online resource allocation algorithms are developed when the statistical knowledge of the random channel fading, data arrivals...
FADES: A tool for automated fault analysis of complex systems
International Nuclear Information System (INIS)
Wood, C.
1990-01-01
FADES is an Expert System for performing fault analyses on complex connected systems. By using a graphical editor to draw components and link them together the FADES system allows the analyst to describe a given system. The knowledge base created is used to qualitatively simulate the system behaviour. By inducing all possible component failures in the system and determining their effects, a set of facts is built up. These facts are then used to create Fault Trees, or FMEA tables. The facts may also be used for explanation effects and to generate diagnostic rules allowing system instrumentation to be optimised. The prototype system has been built and tested and is preently undergoing testing by users. All comments from these trials will be used to tailor the system to the requirements of the user so that the end product performs the exact task required
Progressive transmission of images over fading channels using rate-compatible LDPC codes.
Pan, Xiang; Banihashemi, Amir H; Cuhadar, Aysegul
2006-12-01
In this paper, we propose a combined source/channel coding scheme for transmission of images over fading channels. The proposed scheme employs rate-compatible low-density parity-check codes along with embedded image coders such as JPEG2000 and set partitioning in hierarchical trees (SPIHT). The assignment of channel coding rates to source packets is performed by a fast trellis-based algorithm. We examine the performance of the proposed scheme over correlated and uncorrelated Rayleigh flat-fading channels with and without side information. Simulation results for the expected peak signal-to-noise ratio of reconstructed images, which are within 1 dB of the capacity upper bound over a wide range of channel signal-to-noise ratios, show considerable improvement compared to existing results under similar conditions. We also study the sensitivity of the proposed scheme in the presence of channel estimation error at the transmitter and demonstrate that under most conditions our scheme is more robust compared to existing schemes.
Troxler Fading, Eye Movements, and Retinal Ganglion Cell Properties
Directory of Open Access Journals (Sweden)
Romain Bachy
2014-12-01
Full Text Available We present four movies demonstrating the effect of flicker and blur on the magnitude and speed of adaptation for foveal and peripheral vision along the three color axes that isolate retinal ganglion cells projecting to magno, parvo, and konio layers of the LGN. The demonstrations support the eye movement hypothesis for Troxler fading for brightness and color, and demonstrate the effects of flicker and blur on adaptation of each class of retinal ganglion cells.
Global solutions to the equation of thermoelasticity with fading memory
Okada, Mari; Kawashima, Shuichi
2017-07-01
We consider the initial-history value problem for the one-dimensional equation of thermoelasticity with fading memory. It is proved that if the data are smooth and small, then a unique smooth solution exists globally in time and converges to the constant equilibrium state as time goes to infinity. Our proof is based on a technical energy method which makes use of the strict convexity of the entropy function and the properties of strongly positive definite kernels.
Radiation degradation of molasses pigment. The fading color and product
International Nuclear Information System (INIS)
Sawai, Teruko; Sekiguchi, Masayuki; Tanabe, Hiroko; Sawai, Takeshi
1993-01-01
Water demand in Tokyo has increased rapidly. Because of the scarcity of water supply sources within the city, Tokyo is dependent on the water from other prefectures. Recycling of municipal effluent is an effective means of coping with water shortage in Tokyo. We have studied the radiation treatment of waste water for recycling. In this paper, the radiation decomposition methods for fading color of molasses pigment in the effluent from the sewage treatment plant and in the food industry wastwater were reported. The refractory organic substances (molasses pigment) in samples were degraded by gamma irradiation. The COD values decreased and the dark brown color faded with increasing dosage. The high molecular weight components of molasses pigment were degraded to lower molecular weight substances and were decomposed finally to carbon dioxide. The organic acids, such as formic acid, acetic acid, oxalic acid, citric acid and succinic acid were measured as intermediates of radiolytic decomposition. When we added hydrogen peroxide in samples to the gamma irradiation process, the dark brown color of molasses pigment faded with greater efficiency. (author)
Analysis of Fade Dynamic at Ku-Band in Malaysia
Directory of Open Access Journals (Sweden)
Siat Ling Jong
2014-01-01
Full Text Available This work investigates fade dynamics of satellite communication systems in equatorial heavy rain region based on a one year of Ku-band propagation measurement campaign carried out in Universiti Teknologi Malaysia (UTM, Johor, Malaysia. First order statistics of rain attenuation are deduced and the results are found to be in good agreement with those obtained from other beacon measurements gathered within the same area (Kuala Lumpur. Moreover, the fade duration and slope statistics of the satellite signal variations are also carefully derived and subsequently compared with the ITU-R recommendation model. Such information is useful for the system operator and radio communication engineer for the design of appropriate fade mitigation techniques as well as the quality of service that could be offered to the user (according to the time interval for a typical day. Further evaluation on the performances of several ITU-R models in the heavy rain region are needed based on the measurement database available of this climatic region.
Secrecy Capacity Analysis over α−μ Fading Channels
Lei, Hongjiang
2017-02-15
In this work, we study the secrecy capacity of the classic Wyner’s model over the α − μ fading channels, where α and μ specify the nonlinearity and clustering of fading channels, respectively. The average secrecy capacity (ASC) is derived in closed-form by using the extended generalized bivariate Fox’s Hfunction (EGBFHF). Moreover, the asymptotic analysis of ASC in high signal-to-noise ratio (SNR) regime is conducted. The asymptotic results unveil that the ASC follows the scaling law of Θ(ln p), where p stands for the ratio between the average powers of main channels and eavesdropping channels. Moreover, the ASC can be enhanced by increasing the transmit SNR, while there exists a ceiling of ASC as the SNRs at both sides are improved simultaneously. The accuracy of the analytical results is validated by Monte-Carlo simulations. The numerical results show that rigorous fading channels are beneficial to the secrecy performance, that is, serious nonlinearity (small α) and sparse clustering (small μ) will lead to the improvement of ASC.
Secrecy Capacity Analysis over α−μ Fading Channels
Lei, Hongjiang; Ansari, Imran Shafique; Pan, Gaofeng; Alomair, Basel; Alouini, Mohamed-Slim
2017-01-01
In this work, we study the secrecy capacity of the classic Wyner’s model over the α − μ fading channels, where α and μ specify the nonlinearity and clustering of fading channels, respectively. The average secrecy capacity (ASC) is derived in closed-form by using the extended generalized bivariate Fox’s Hfunction (EGBFHF). Moreover, the asymptotic analysis of ASC in high signal-to-noise ratio (SNR) regime is conducted. The asymptotic results unveil that the ASC follows the scaling law of Θ(ln p), where p stands for the ratio between the average powers of main channels and eavesdropping channels. Moreover, the ASC can be enhanced by increasing the transmit SNR, while there exists a ceiling of ASC as the SNRs at both sides are improved simultaneously. The accuracy of the analytical results is validated by Monte-Carlo simulations. The numerical results show that rigorous fading channels are beneficial to the secrecy performance, that is, serious nonlinearity (small α) and sparse clustering (small μ) will lead to the improvement of ASC.
DISK-RELATED BURSTS AND FADES IN YOUNG STARS
International Nuclear Information System (INIS)
Findeisen, Krzysztof; Hillenbrand, Lynne; Levitan, David; Sesar, Branimir; Ofek, Eran; Laher, Russ; Surace, Jason
2013-01-01
We present first results from a new, multiyear, time domain survey of young stars in the North America Nebula complex using the Palomar Transient Factory. Our survey is providing an unprecedented view of aperiodic variability in young stars on timescales of days to years. The analyzed sample covers R PTF ≈ 13.5-18 and spans a range of mid-infrared color, with larger-amplitude optical variables (exceeding 0.4 mag root mean squared) more likely to have mid-infrared evidence for circumstellar material. This paper characterizes infrared excess stars with distinct bursts above or fades below a baseline of lower-level variability, identifying 41 examples. The light curves exhibit a remarkable diversity of amplitudes, timescales, and morphologies, with a continuum of behaviors that cannot be classified into distinct groups. Among the bursters, we identify three particularly promising sources that may represent theoretically predicted short-timescale accretion instabilities. Finally, we find that fading behavior is approximately twice as common as bursting behavior on timescales of days to years, although the bursting and fading duty cycle for individual objects often varies from year to year.
Fading AGN Candidates: AGN Histories and Outflow Signatures
Energy Technology Data Exchange (ETDEWEB)
Keel, William C.; Maksym, W. Peter [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States); Lintott, Chris J. [Astrophysics, Oxford University and Adler Planetarium, 1300 S. Lakeshore Drive, Chicago, IL 60605 (United States); Bennert, Vardha N.; Scott, Bryan; Showley, Charles; Flatland, Kelsi [Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407 (United States); Chojnowski, S. Drew [Department of Astronomy, New Mexico State University, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003-8001 (United States); Moiseev, Alexei; Smirnova, Aleksandrina [Special Astrophysical Observatory, Russian Academy of Sciences, Nizhny Arkhyz, 369167 (Russian Federation); Schawinski, Kevin; Sartori, Lia F. [Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-Straße 27, CH-8093 Zurich (Switzerland); Urry, C. Megan [Department of Physics, Yale University, P.O. Box 208120, New Haven, CT 06520-8120 (United States); Pancoast, Anna [Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Schirmer, Mischa, E-mail: wkeel@ua.edu [Gemini Observatory, La Serena (Chile)
2017-02-01
We consider the energy budgets and radiative history of eight fading active galactic nuclei (AGNs), identified from an energy shortfall between the requirements to ionize very extended (radius > 10 kpc) ionized clouds and the luminosity of the nucleus as we view it directly. All show evidence of significant fading on timescales of ≈50,000 yr. We explore the use of minimum ionizing luminosity Q {sub ion} derived from photoionization balance in the brightest pixels in H α at each projected radius. Tests using presumably constant Palomar–Green QSOs, and one of our targets with detailed photoionization modeling, suggest that we can derive useful histories of individual AGNs, with the caveat that the minimum ionizing luminosity is always an underestimate and subject to uncertainties about fine structure in the ionized material. These consistency tests suggest that the degree of underestimation from the upper envelope of reconstructed Q {sub ion} values is roughly constant for a given object and therefore does not prevent such derivation. The AGNs in our sample show a range of behaviors, with rapid drops and standstills; the common feature is a rapid drop in the last ≈2×10{sup 4} yr before the direct view of the nucleus. The e -folding timescales for ionizing luminosity are mostly in the thousands of years, with a few episodes as short as 400 yr. In the limit of largely obscured AGNs, we find additional evidence for fading from the shortfall between even the lower limits from recombination balance and the maximum luminosities derived from far-infrared fluxes. We compare these long-term light curves, and the occurrence of these fading objects among all optically identified AGNs, to simulations of AGN accretion; the strongest variations over these timespans are seen in models with strong and local (parsec-scale) feedback. We present Gemini integral-field optical spectroscopy, which shows a very limited role for outflows in these ionized structures. While rings and
Fading AGN Candidates: AGN Histories and Outflow Signatures
International Nuclear Information System (INIS)
Keel, William C.; Maksym, W. Peter; Lintott, Chris J.; Bennert, Vardha N.; Scott, Bryan; Showley, Charles; Flatland, Kelsi; Chojnowski, S. Drew; Moiseev, Alexei; Smirnova, Aleksandrina; Schawinski, Kevin; Sartori, Lia F.; Urry, C. Megan; Pancoast, Anna; Schirmer, Mischa
2017-01-01
We consider the energy budgets and radiative history of eight fading active galactic nuclei (AGNs), identified from an energy shortfall between the requirements to ionize very extended (radius > 10 kpc) ionized clouds and the luminosity of the nucleus as we view it directly. All show evidence of significant fading on timescales of ≈50,000 yr. We explore the use of minimum ionizing luminosity Q ion derived from photoionization balance in the brightest pixels in H α at each projected radius. Tests using presumably constant Palomar–Green QSOs, and one of our targets with detailed photoionization modeling, suggest that we can derive useful histories of individual AGNs, with the caveat that the minimum ionizing luminosity is always an underestimate and subject to uncertainties about fine structure in the ionized material. These consistency tests suggest that the degree of underestimation from the upper envelope of reconstructed Q ion values is roughly constant for a given object and therefore does not prevent such derivation. The AGNs in our sample show a range of behaviors, with rapid drops and standstills; the common feature is a rapid drop in the last ≈2×10 4 yr before the direct view of the nucleus. The e -folding timescales for ionizing luminosity are mostly in the thousands of years, with a few episodes as short as 400 yr. In the limit of largely obscured AGNs, we find additional evidence for fading from the shortfall between even the lower limits from recombination balance and the maximum luminosities derived from far-infrared fluxes. We compare these long-term light curves, and the occurrence of these fading objects among all optically identified AGNs, to simulations of AGN accretion; the strongest variations over these timespans are seen in models with strong and local (parsec-scale) feedback. We present Gemini integral-field optical spectroscopy, which shows a very limited role for outflows in these ionized structures. While rings and loops of emission
Optimal Training for Time-Selective Wireless Fading Channels Using Cutoff Rate
Directory of Open Access Journals (Sweden)
Tong Lang
2006-01-01
Full Text Available We consider the optimal allocation of resources—power and bandwidth—between training and data transmissions for single-user time-selective Rayleigh flat-fading channels under the cutoff rate criterion. The transmitter exploits statistical channel state information (CSI in the form of the channel Doppler spectrum to embed pilot symbols into the transmission stream. At the receiver, instantaneous, though imperfect, CSI is acquired through minimum mean-square estimation of the channel based on some set of pilot observations. We compute the ergodic cutoff rate for this scenario. Assuming estimator-based interleaving and -PSK inputs, we study two special cases in-depth. First, we derive the optimal resource allocation for the Gauss-Markov correlation model. Next, we validate and refine these insights by studying resource allocation for the Jakes model.
Directory of Open Access Journals (Sweden)
David Overbye
2005-06-01
Full Text Available In this paper we examine the impact of channel fading on the bit error rate of a DS-CDMA communication system. The system employs detectors that incorporate neural networks effecting methods of independent component analysis (ICA, subspace estimation of channel noise, and Hopfield type neural networks. The Rayleigh fading channel model is used. When employed in a Rayleigh fading environment, the ICA neural network detectors that give superior performance in a flat fading channel did not retain this superior performance. We then present a new method of compensating for channel fading based on the incorporation of priors in the ICA neural network learning algorithms. When the ICA neural network detectors were compensated using the incorporation of priors, they give significantly better performance than the traditional detectors and the uncompensated ICA detectors. Keywords: CDMA, Multi-user Detection, Rayleigh Fading, Multipath Detection, Independent Component Analysis, Prior Probability Hebbian Learning, Natural Gradient
International Nuclear Information System (INIS)
Ben-Shachar, B.; German, U.; Weiser, G.
1983-03-01
The fading of LiF and CaF 2 :Dy was investigated and the results were compared to the literature. The effect of thermal annealing was studied in order to reduce the fading in both phosphors and to minimize the effects of the environment on CaF 2 :Dy. Minimizing the fading and knowing its time dependence make possible the exact personal and environmental dosimetry. (Author)
OPRA capacity bounds for selection diversity over generalized fading channels
Hanif, Muhammad Fainan
2014-05-01
Channel side information at the transmitter can increase the average capacity by enabling optimal power and rate adaptation. The resulting optimal power and rate adaptation (OPRA) capacity rarely has a closed-form analytic expression. In this paper, lower and upper bounds on OPRA capacity for selection diversity scheme are presented. These bounds hold for variety of fading channels including log-normal and generalized Gamma distributed models and have very simple analytic expressions for easy evaluation even for kth best path selection. Some selected numerical results show that the newly proposed bounds closely approximate the actual OPRA capacity. © 2014 IEEE.
Fade statistics of M-turbulent optical links
DEFF Research Database (Denmark)
Jurado-Navas, Antonio; Maria Garrido-Balsells, Jose; Castillo-Vazquez, Miguel
2017-01-01
A new and generalized statistical model, called Malaga or simply M distribution, has been derived recently to characterize the irradiance fluctuations of an unbounded optical wavefront propagating through a turbulent medium under all irradiance fluctuation conditions. The aforementioned model...... extends and unifies in a simple analytical closed-form expression most of the proposed statistical models for free-space optical (FSO) communications widely employed until now in the scientific literature. Based on that M model, we have studied some important features associated to its fade statistics...
National Research Council Canada - National Science Library
Ong, Choon
1998-01-01
The performance analysis of a differential phase shift keyed (DPSK) communications system, operating in a Rayleigh fading environment, employing convolutional coding and diversity processing is presented...
Performance Analysis of Rayleigh Fading and Cochannel Interference in Wireless Communication
National Research Council Canada - National Science Library
Gao, Chunjun
2000-01-01
...) performance of adaptive arrays for wireless communications over fading channels in the presence of cochannel interference, particularly the case when the number of interference sources exceeds...
Efficient incremental relaying for packet transmission over fading channels
Fareed, Muhammad Mehboob
2014-07-01
In this paper, we propose a novel relaying scheme for packet transmission over fading channels, which improves the spectral efficiency of cooperative diversity systems by utilizing limited feedback from the destination. Our scheme capitalizes on the fact that relaying is only required when direct transmission suffers deep fading. We calculate the packet error rate for the proposed efficient incremental relaying (EIR) scheme with both amplify and forward and decode and forward relaying. We compare the performance of the EIR scheme with the threshold-based incremental relaying (TIR) scheme. It is shown that the efficiency of the TIR scheme is better for lower values of the threshold. However, the efficiency of the TIR scheme for higher values of threshold is outperformed by the EIR. In addition, three new threshold-based adaptive EIR are devised to further improve the efficiency of the EIR scheme. We calculate the packet error rate and the efficiency of these new schemes to provide the analytical insight. © 2014 IEEE.
The fading of irradiated blue-colored pearls
International Nuclear Information System (INIS)
Okamoto, Shinichi
1982-01-01
The fading of irradiated and natural blue-colored pearls was investigated in this experiment. Thirty natural blue-colored pearls and sixty irradiated blue-colored pearls were used. Some of them were placed at a light position of RT. Another pearls were placed at a dark position of 50 0 C. The irradiated pearls placed at a light position of RT didn't show remarkable fading in their color in 294 days. But the natural blue-colored pearls showed a little recovery from 4% to 8% in reflection factors in 223 days at RT. The irradiated pearls placed at a dark position of 50 0 C showed the recovery from 9% to 14% in 264 days independently of irradiation times. The natural blue-colored pearls also showed the bleaching from 5% to 10% in reflection factor in 86 days at 50 0 C. Both irradiated and natural blue-colored pearls hardly showed their remarkable changes in their chromaticities independently of temperatures. (author)
Color transplant for reverse ageing of faded artworks
Del Mastio, A.; Piva, A.; Barni, M.; Cappellini, V.; Stefanini, L.
2008-02-01
Nowadays, photographs are one of the most used media for communication. Images are used for the representation of documents, Cultural goods, and so on: they are used to pass on a wedge of historical memory of the society. Since its origin, the photographic technique has got several improvements; nevertheless, photos are liable to several damages, both concerning the physical support and concerning the colors and figures which are depicted in it: for example, think about scratches or rips happened to a photo, or think about the fading or red (or yellow) toning concerning the colors of a photo. In this paper, we propose a novel method which is able to assess the original beauty of digital reproductions of aged photos, as well as digital reproductions of faded goods. The method is based on the comparison of the degraded image with a not-degraded one showing similar contents; thus, the colors of the not-degraded image can be transplanted in the degraded one. The key idea is a dualism between the analytical mechanics and the color theory: for each of the degraded and not-degraded images we compute first a scatter plot of the x and y normalized coordinates of their colors; these scatter diagrams can be regarded as a system of point masses, thus provided of inertia axes and an inertia ellipsoid. Moving the scatter diagram of the degraded image over the one belonging to the not-degraded image, the colors of the degraded image can be restored.
Tackling capacity fading in vanadium flow batteries with amphoteric membranes
Oldenburg, Fabio J.; Schmidt, Thomas J.; Gubler, Lorenz
2017-11-01
Capacity fading and poor electrolyte utilization caused by electrolyte imbalance effects are major drawbacks for the commercialization of vanadium flow batteries (VFB). The influence of membrane type (cationic, anionic, amphoteric) on these effects is studied by determining the excess and net flux of each vanadium ion in an operating VFB assembled with a cation exchange membrane (CEM), Nafion® NR212, an anion exchange membrane (AEM), Fumatech FAP-450, and an amphoteric ion exchange membrane (AIEM) synthesized in-house. It is shown that the net vanadium flux, accompanied by water transport, is directed towards the positive side for the CEM and towards the negative side for the AEM. The content of cation and anion exchange groups in the AIEM is adjusted via radiation grafting to balance the vanadium flux between the two electrolyte sides. With the AIEM the net vanadium flux is significantly reduced and capacity fading due to electrolyte imbalances can be largely eliminated. The membrane's influence on electrolyte imbalance effects is characterized and quantified in one single charge-discharge cycle by analyzing the content of the four different vanadium species in the two electrolytes. The experimental data recorded herewith conclusively explains the electrolyte composition after 80 cycles.
Energy Technology Data Exchange (ETDEWEB)
Borg, Matthew K., E-mail: matthew.borg@strath.ac.uk [Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Lockerby, Duncan A., E-mail: duncan.lockerby@warwick.ac.uk [School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom); Reese, Jason M., E-mail: jason.reese@ed.ac.uk [School of Engineering, University of Edinburgh, Edinburgh EH9 3JL (United Kingdom)
2014-02-21
The emergence of new applications of molecular dynamics (MD) simulation calls for the development of mass-statting procedures that insert or delete particles on-the-fly. In this paper we present a new mass-stat which we term FADE, because it gradually “fades-in” (inserts) or “fades-out” (deletes) molecules over a short relaxation period within a MD simulation. FADE applies a time-weighted relaxation to the intermolecular pair forces between the inserting/deleting molecule and any neighbouring molecules. The weighting function we propose in this paper is a piece-wise polynomial that can be described entirely by two parameters: the relaxation time scale and the order of the polynomial. FADE inherently conserves overall system momentum independent of the form of the weighting function. We demonstrate various simulations of insertions of atomic argon, polyatomic TIP4P water, polymer strands, and C{sub 60} Buckminsterfullerene molecules. We propose FADE parameters and a maximum density variation per insertion-instance that restricts spurious potential energy changes entering the system within desired tolerances. We also demonstrate in this paper that FADE compares very well to an existing insertion algorithm called USHER, in terms of accuracy, insertion rate (in dense fluids), and computational efficiency. The USHER algorithm is applicable to monatomic and water molecules only, but we demonstrate that FADE can be generally applied to various forms and sizes of molecules, such as polymeric molecules of long aspect ratio, and spherical carbon fullerenes with hollow interiors.
International Nuclear Information System (INIS)
Borg, Matthew K.; Lockerby, Duncan A.; Reese, Jason M.
2014-01-01
The emergence of new applications of molecular dynamics (MD) simulation calls for the development of mass-statting procedures that insert or delete particles on-the-fly. In this paper we present a new mass-stat which we term FADE, because it gradually “fades-in” (inserts) or “fades-out” (deletes) molecules over a short relaxation period within a MD simulation. FADE applies a time-weighted relaxation to the intermolecular pair forces between the inserting/deleting molecule and any neighbouring molecules. The weighting function we propose in this paper is a piece-wise polynomial that can be described entirely by two parameters: the relaxation time scale and the order of the polynomial. FADE inherently conserves overall system momentum independent of the form of the weighting function. We demonstrate various simulations of insertions of atomic argon, polyatomic TIP4P water, polymer strands, and C 60 Buckminsterfullerene molecules. We propose FADE parameters and a maximum density variation per insertion-instance that restricts spurious potential energy changes entering the system within desired tolerances. We also demonstrate in this paper that FADE compares very well to an existing insertion algorithm called USHER, in terms of accuracy, insertion rate (in dense fluids), and computational efficiency. The USHER algorithm is applicable to monatomic and water molecules only, but we demonstrate that FADE can be generally applied to various forms and sizes of molecules, such as polymeric molecules of long aspect ratio, and spherical carbon fullerenes with hollow interiors
ter Vrugte, Judith; de Jong, Anthonius J.M.; Vandercruysse, Sylke; Wouters, Pieter; van Oostendorp, Herre; Elen, Jan
This study addresses the added value of faded worked examples in a computer game-based learning environment. The faded worked examples were introduced to encourage active selection and processing of domain content in the game. The content of the game was proportional reasoning and participants were
Dependence of (anomalous) fading of infra-red stimulated luminescence on trap occupancy in feldspars
DEFF Research Database (Denmark)
Morthekai, P.; Jain, Mayank; Gach, Grzegorz
2013-01-01
Dose dependency of anomalous fading of infra-red stimulated luminescence (IRSL) from feldspars has been investigated using radiations of different ionisation qualities. The rate of fading of the IRSL signal after proton irradiation (9.4–30%/decade) is on an average almost twice compared...
Performance Analysis of Beamforming in MU-MIMO Systems for Rayleigh Fading Channels
Hassan, Ahmad K.
2017-03-25
This paper characterizes the performance metrics of MU-MIMO systems under Rayleigh fading channels in the presence of both cochannel interference and additive noise with unknown channel state information and known correlation matrices. In the first task, we derive analytical expressions for the cumulative distribution function of the instantaneous signal-to-interference-plus-noise ratio (SINR) for any deterministic beamvectors. As a second task, exact closed-form expressions are derived for the instantaneous capacity, the upper bound on ergodic capacity, and the Gram-Schmidt orthogonalization-based ergodic capacity for similar intra-cell correlation coefficients. Finally, we present the utility of several structured-diagonalization techniques, which can achieve the tractability for the approximate solution of ergodic capacity for both similar as well as different intra-cell correlation matrices. The novelty of this paper is to formulate the received SINR in terms of indefinite quadratic forms, which allows us to use complex residue theory to characterize the system behavior. The analytical expressions obtained closely match simulation results.
Performance Analysis of Beamforming in MU-MIMO Systems for Rayleigh Fading Channels
Hassan, Ahmad K.; Moinuddin, Muhammad; Al-Saggaf, Ubaid M.; Al-Naffouri, Tareq Y.
2017-01-01
This paper characterizes the performance metrics of MU-MIMO systems under Rayleigh fading channels in the presence of both cochannel interference and additive noise with unknown channel state information and known correlation matrices. In the first task, we derive analytical expressions for the cumulative distribution function of the instantaneous signal-to-interference-plus-noise ratio (SINR) for any deterministic beamvectors. As a second task, exact closed-form expressions are derived for the instantaneous capacity, the upper bound on ergodic capacity, and the Gram-Schmidt orthogonalization-based ergodic capacity for similar intra-cell correlation coefficients. Finally, we present the utility of several structured-diagonalization techniques, which can achieve the tractability for the approximate solution of ergodic capacity for both similar as well as different intra-cell correlation matrices. The novelty of this paper is to formulate the received SINR in terms of indefinite quadratic forms, which allows us to use complex residue theory to characterize the system behavior. The analytical expressions obtained closely match simulation results.
Modeling fade patterns of nipple areola complex tattoos following breast reconstruction.
Levites, Heather A; Fourman, Mitchell S; Phillips, Brett T; Fromm, Indira M; Khan, Sami U; Dagum, Alexander B; Bui, Duc T
2014-12-01
Nipple-areolar complex (NAC) tattoos are an effective cosmetic solution for creating a finished look following breast reconstruction procedures. NAC tattoos are prone to significant fading, leading patients to seek revisions. This study was designed to quantify changes in NAC tattoo appearance over time. A total of 71 images of 39 patients were analyzed for NAC tattoo color and shape by 5 blinded medical student graders using a customized scoring system. Subsequently, each image was analyzed using ColorPic software (Iconico, New York, NY). Red/green/blue and hue/saturation/value color parameters were collected. Color quantities were normalized to the individual patient's skin tone to control for variability in lighting. Spearman correlations and nonlinear regressions were calculated utilizing GraphPad Prism 6.0 (GraphPad, La Jolla, CA). The length of time after tattoo placement inversely correlated with color score (P tattoo placement was also inversely correlated with all quantitative color parameters. Each color parameter fit a 1-phase exponential decay model. The decline in qualitative color and shape score agrees with clinical experience of tattoo quality declining over time. The color qualities of the tattoo approach those of the patient's skin over time, ultimately reaching a plateau. This can be modeled using a 1-phase decay equation. In practice, tattoo colors may be selected that compensate for the predictable changes that will occur. The results of this study will help optimize tattoo color and may alleviate the need for NAC tattoo revisions.
Polarimetry and photometry of M87: is the jet fading
Energy Technology Data Exchange (ETDEWEB)
Warren-Smith, R F; King, D J; Scarrott, S M [Durham Univ. (UK). Dept. of Physics
1984-09-15
Optical linear polarization mapping and photometry of M87 is presented in B and R wavebands. The results indicate significant polarization in the galactic nucleus. Polarization in the jet in B is consistent with other recent maps obtained for this area in blue light and no significant variation with wavelength between B and R wavebands is found. The spectral index of the jet radiation is measured to be S=-1.65+-0.2 over the wavelength range observed. Comparison of the integrated B magnitude of the jet with previous independent measurements over the period 1934-80 suggests that the jet is variable and has been fading more or less uniformly by about 0.8 mag per decade between 1964 and 1980.
Asymptotic analysis of multicell massive MIMO over Rician fading channels
Sanguinetti, Luca; Kammoun, Abla; Debbah, Merouane
2017-01-01
This work considers the downlink of a multicell massive MIMO system in which L base stations (BSs) of N antennas each communicate with K single-antenna user equipments randomly positioned in the coverage area. Within this setting, we are interested in evaluating the sum rate of the system when MRT and RZF are employed under the assumption that each intracell link forms a MIMO Rician uncorrelated fading channel. The analysis is conducted assuming that N and K grow large with a non-trivial ratio N/K under the assumption that the data transmission in each cell is affected by channel estimation errors, pilot contamination, and an arbitrary large scale attenuation. Numerical results are used to validate the asymptotic analysis in the finite system regime and to evaluate the network performance under different settings. The asymptotic results are also instrumental to get insights into the interplay among system parameters.
Asymptotic analysis of multicell massive MIMO over Rician fading channels
Sanguinetti, Luca
2017-06-20
This work considers the downlink of a multicell massive MIMO system in which L base stations (BSs) of N antennas each communicate with K single-antenna user equipments randomly positioned in the coverage area. Within this setting, we are interested in evaluating the sum rate of the system when MRT and RZF are employed under the assumption that each intracell link forms a MIMO Rician uncorrelated fading channel. The analysis is conducted assuming that N and K grow large with a non-trivial ratio N/K under the assumption that the data transmission in each cell is affected by channel estimation errors, pilot contamination, and an arbitrary large scale attenuation. Numerical results are used to validate the asymptotic analysis in the finite system regime and to evaluate the network performance under different settings. The asymptotic results are also instrumental to get insights into the interplay among system parameters.
Developing a numerical simulation for fading in feldspar
International Nuclear Information System (INIS)
Larsen, A.; Greilich, S.; Jain, M.; Murray, A.S.
2009-01-01
Most models describing anomalous fading in feldspars are based on analytical solutions. As an alternative approach we present an entirely numerical model based on statistical sampling that simulates stepwise the charge creation/trapping and recombination in a given phosphor. We assume the number density of electrons and holes at any time to be equal, although the model is not bound to that assumption. The model is flexible enough to be used on any combination of geological and laboratory timescales and for any defined configuration of defects. Using this approach we observed reorganization of nearest-neighbor distances with time. The best agreement with experimental data is achieved if we assume the crystal to consist of small subvolumes (nanocrystals) only within which charge carriers are allowed to recombine.
Atropine and ODQ antagonize tetanic fade induced by L-arginine in cats
Directory of Open Access Journals (Sweden)
J.M. Cruciol-Souza
1999-10-01
Full Text Available Although it has been demonstrated that nitric oxide (NO released from sodium nitrite induces tetanic fade in the cat neuromuscular preparations, the effect of L-arginine on tetanic fade and its origin induced by NO have not been studied in these preparations. Furthermore, atropine reduces tetanic fade induced by several cholinergic and anticholinergic drugs in these preparations, whose mechanism is suggested to be mediated by the interaction of acetylcholine with inhibitory presynaptic muscarinic receptors. The present study was conducted in cats to determine the effects of L-arginine alone or after pretreatment with atropine or 1H-[1,2,4]oxadiazole [4,3-a]quinoxalin-1-one (ODQ on neuromuscular preparations indirectly stimulated at high frequency. Drugs were injected into the middle genicular artery. L-arginine (2 mg/kg and S-nitroso-N-acetylpenicillamine (SNAP; 16 µg/kg induced tetanic fade. The Nw-nitro-L-arginine (L-NOARG; 2 mg/kg alone did not produce any effect, but reduced the tetanic fade induced by L-arginine. D-arginine (2 mg/kg did not induce changes in tetanic fade. The tetanic fade induced by L-arginine or SNAP was reduced by previous injection of atropine (1.0 µg/kg or ODQ (15 µg/kg. ODQ alone did not change tetanic fade. The data suggest that the NO-synthase-GC pathway participates in the L-arginine-induced tetanic fade in cat neuromuscular preparations. The tetanic fade induced by L-arginine probably depends on the action of NO at the presynaptic level. NO may stimulate guanylate cyclase increasing acetylcholine release and thereby stimulating presynaptic muscarinic receptors.
Ear-to-Ear On-Body Channel Fading in the ISM-band for Tangentially-Polarized Antennas
DEFF Research Database (Denmark)
Kvist, Søren Helstrup; Thaysen, Jesper; Jakobsen, Kaj Bjarne
2011-01-01
The ear-to-ear on-body channel fading has been studied in the ISM-band. The ear-to-ear path gain was measured on six persons in an indoor environment for a duration of 200 s. The channel fading has been characterized in terms of empirical cumulative distribution functions (CDF), average fade...
International Nuclear Information System (INIS)
Sasho Nikolovski, Sasho; Nikolovska, Lidija; Velevska, Marija; Velev, Velko
2010-01-01
Fading is a process when the latent information of a detector is unintentionally lost mainly due to the thermal influence. Thermoluminescent (TL) detectors have different sensitivities as far as the fading effect. Encapsulated TL detectors mounted within shielded filter holders are used during the personal monitoring of occupationally exposed persons in R. Macedonia. PTFE-Teflon registered trademark polymer is an example of encapsulation material that has a temperature resistance and it allows the luminescence signal to pass through. Since the encapsulated TL detectors cannot be submitted to annealing treatment in an oven, another fading reduction method is needed. The TL evaluation method suggested in this work is based on a specific glow-curve region. Irradiations were conducted using 90Sr/90Y source. Post-irradiation fade investigations were conducted for evaluation periods that varied up to 4 months. Two areas of the TL glow-curve were selected with the WimRems software. They correspond to the high and the low fading emission peaks (the lower temperature peaks display a greater degree of thermal fading than the higher temperature peaks). Post-irradiation fade is a contributing factor that affects the response of a thermoluminescent (TL) phosphor as a function of time. PTFE - Polytetrafluoroethylene most well known by the DuPont brand name Teflon registered trademark. (Author)
Text-fading based training leads to transfer effects on children’s sentence reading fluency
Directory of Open Access Journals (Sweden)
Telse eNagler
2015-02-01
Full Text Available Previous studies used a text-fading procedure as a training tool with the goal to increase silent reading fluency (i.e., proficient reading rate and comprehension. In recently published studies, this procedure resulted in lasting reading enhancements for adult and adolescent research samples. However, studies working with children reported mixed results. While reading rate improvements were observable for Dutch reading children in a text-fading training study, reading fluency improvements in standardized reading tests post-training attributable to the fading manipulation were not detectable. These results raise the question of whether text-fading training is not effective for children or whether research design issues have concealed possible transfer effects. Hence, the present study sought to investigate possible transfer effects resulting from a text-fading based reading training program, using a modified research design. Over a period of three weeks, two groups of German third-graders read sentences either with an adaptive text-fading procedure or at their self-paced reading rate. A standardized test measuring reading fluency at the word, sentence, and text level was conducted pre- and post-training. Text level reading fluency improved for both groups equally. Post-training gains at the word level were found for the text-fading group, however, no significant interaction between groups was revealed for word reading fluency. Sentence level reading fluency gains were found for the text-fading group, which significantly differed from the group of children reading at their self-paced reading routine. These findings provide evidence for the efficacy of text-fading as a training method for sentence reading fluency improvement also for children.
Analysis of rain fade duration models for Earth-to-satellite path based on data measured in Malaysia
International Nuclear Information System (INIS)
Dao, Hassan; Rafiqul, Islam Md; Al-Khateeb, Khalid A S
2013-01-01
Statistical analysis of rain fade duration is crucial information for system engineer to design and plan a fade mitigation technique (FMT) for the satellite communication system. An investigation is carried out based on data measured of one year period in Kuala Lumpur, Malaysia from satellite path of MEASAT3. This paper presents statistical analysis of measured fade duration on high elevation angle (77.4°) in Ku-band compared to three prediction models of fade duration. It is found that none of the models could predict measured fade duration distribution accurately
The thermodynamics of simple materials with fading memory
Day, William Alan
1972-01-01
This Tract gives an account of certain recent attempts to construct a satisfactory theory of thermodynamics for materials which have a memory for the past. Naturally it draws heavily on the writings of those who have made significant contributions to the field. I am particularly grateful to Professor C. A. Truesdell of The lohns Hopkins University for his invitation to write the Tract and to Professor A. E. Green of Oxford for his comments on various parts of the manuscript. Hertford College, Oxford December 1971 W. A. Day Contents Introduction 1 Chapter 1 Preliminaries 5 1. 1 Vector and Tensor Analysis. 5 1. 2 Paths and Line Integrals . 7 1. 3 Kinematics and the Balance Laws 11 1. 4 Simple Materials with Memory 15 21 Chapter 2 A Theory of Thermodynamics . 2. 1 Processes. 21 2. 2 The Thermodynamic Inequality . 23 2. 3 Heat Conduction Inequalities . 24 2. 4 The Conversion of Heat into Mechanical Work 27 31 The Construction of the Entropy Chapter 3 The Clausius Inequality 31 3. 1 3. 2 Fading Memory . 34 3. 3 Th...
Internal tides and deep diel fades in acoustic intensity.
White, Andrew W; Henyey, Frank S; Andrew, Rex K; Mercer, James A; Worcester, Peter F; Dzieciuch, Matthew A; Colosi, John A
2016-11-01
A mechanism is presented by which the observed acoustic intensity is made to vary due to changes in the acoustic path that are caused by internal-tide vertical fluid displacements. The position in range and depth of large-scale caustic structure is determined by the background sound-speed profile. Internal tides cause a deformation of the background profile, changing the positions of the caustic structures-which can introduce intensity changes at a distant receiver. Gradual fades in the acoustic intensity occurring over timescales similar to those of the tides were measured during a low-frequency (284-Hz) acoustic scattering experiment in the Philippine Sea in 2009 [White et al., J. Acoust. Soc. Am. 134(4), 3347-3358 (2013)]. Parabolic equation and Hamiltonian ray-tracing calculations of acoustic propagation through a plane-wave internal tide environmental model employing sound-speed profiles taken during the experiment indicate that internal tides could cause significant gradual changes in the received intensity. Furthermore, the calculations demonstrate how large-scale perturbations to the index of refraction can result in variation in the received intensity.
On the Delay-Energy Tradeoff in Multiuser Fading Channels
Directory of Open Access Journals (Sweden)
Ralf R. Müller
2009-01-01
Full Text Available We consider the delay-energy tradeoff on a fading channel with multiuser diversity. For fixed arbitrary rates of the users, the total transmitted energy is minimized subject to a delay constraint. To achieve this goal we propose a scheme which schedules a subset of all users simultaneously. The scheduled users are allocated power to guarantee successful separation at the detector by successive decoding. In this way, we can benefit from both multiuser diversity and the near-far situation via scheduling and simultaneous transmission, respectively. We analytically show that when the number of users goes to infinity the energy required to guarantee the required user rates can be made as small as required at the cost of a higher delay “delay-energy tradeoff”. We explicitly compute the delay under the proposed scheduling policy and discuss how delay differentiation can be achieved. We extend the results to multiband multiaccess channel. Finally, all the results can be generalized in a straightforward fashion to broadcast channel due to the Gaussian multiaccess-broadcast channel duality.
Directory of Open Access Journals (Sweden)
Liu KJ Ray
2002-01-01
Full Text Available Orthogonal frequency division multiplexing (OFDM is an effective technique for the future 3G communications because of its great immunity to impulse noise and intersymbol interference. The channel estimation is a crucial aspect in the design of OFDM systems. In this work, we propose a channel estimation algorithm based on a time-frequency polynomial model of the fading multipath channels. The algorithm exploits the correlation of the channel responses in both time and frequency domains and hence reduce more noise than the methods using only time or frequency polynomial model. The estimator is also more robust compared to the existing methods based on Fourier transform. The simulation shows that it has more than improvement in terms of mean-squared estimation error under some practical channel conditions. The algorithm needs little prior knowledge about the delay and fading properties of the channel. The algorithm can be implemented recursively and can adjust itself to follow the variation of the channel statistics.
Achievable capacity of a spectrum sharing system over hyper fading channels
Ekin, Sabit; Yilmaz, Ferkan; Ç elebi, Hasari Burak; Qaraqe, Khalid A.; Alouini, Mohamed-Slim; Serpedin, Erchin
2009-01-01
Cognitive radio with spectrum sharing feature is a promising technique to address the spectrum under-utilization problem in dynamically changing environments. In this paper, achievable capacity gain of spectrum sharing systems over dynamic fading
Delay-limited capacity of fading multiple access and broadcast channels in the low power regime
Rezki, Zouheir; Alouini, Mohamed-Slim
2015-01-01
show that for fading channels where the MAC capacity region is strictly positive, it has a multidimensional rectangle structure and thus is simply characterized by single user capacity points. More specifically, we show that at low power, the boundary
MGF Approach to the Analysis of Generalized Two-Ray Fading Models
Rao, Milind; Lopez-Martinez, F. Javier; Alouini, Mohamed-Slim; Goldsmith, Andrea
2015-01-01
We analyze a class of Generalized Two-Ray (GTR) fading channels that consist of two line of sight (LOS) components with random phase plus a diffuse component. We derive a closedform expression for the moment generating function (MGF) of the signal-to-noise ratio (SNR) for this model, which greatly simplifies its analysis. This expression arises from the observation that the GTR fading model can be expressed in terms of a conditional underlying Rician distribution. We illustrate the approach to derive simple expressions for statistics and performance metrics of interest such as the amount of fading, the level crossing rate, the symbol error rate, and the ergodic capacity in GTR fading channels. We also show that the effect of considering a more general distribution for the phase difference between the LOS components has an impact on the average SNR.
Sungjoon Park,; Stark, Wayne E.
2011-01-01
In this paper we present opportunistic relay communication strategies of decode and forward relaying. The channel that we are considering includes pathloss, shadowing, and fast fading effects. We find a simple outage probability formula
A study of optimization problem for amplify-and-forward relaying over weibull fading channels
Ikki, Salama Said; Aissa, Sonia
2010-01-01
This paper addresses the power allocation and relay positioning problems in amplify-and-forward cooperative networks operating in Weibull fading environments. We study adaptive power allocation (PA) with fixed relay location, optimal relay location
Continuous-variable quantum key distribution in uniform fast-fading channels
Papanastasiou, Panagiotis; Weedbrook, Christian; Pirandola, Stefano
2018-03-01
We investigate the performance of several continuous-variable quantum key distribution protocols in the presence of uniform fading channels. These are lossy channels whose transmissivity changes according to a uniform probability distribution. We assume the worst-case scenario where an eavesdropper induces a fast-fading process, where she chooses the instantaneous transmissivity while the remote parties may only detect the mean statistical effect. We analyze coherent-state protocols in various configurations, including the one-way switching protocol in reverse reconciliation, the measurement-device-independent protocol in the symmetric configuration, and its extension to a three-party network. We show that, regardless of the advantage given to the eavesdropper (control of the fading), these protocols can still achieve high rates under realistic attacks, within reasonable values for the variance of the probability distribution associated with the fading process.
Transmit selection for imperfect threshold-based receive MRC in Rayleigh fading channels
Radaydeh, Redha Mahmoud Mesleh; Alouini, Mohamed-Slim
2010-01-01
experience identically distributed and non-identically distributed Rayleigh fading conditions. New closed-form expressions for the combined SNR statistics and some performance measures are presented. The system models adopted herein and the presented
Capacity bounds for kth best path selection over generalized fading channels
Hanif, Muhammad Fainan; Yang, Hongchuan; Alouini, Mohamed-Slim
2014-01-01
Exact ergodic capacity calculation for fading wireless channels typically involves time-consuming numerical evaluation of infinite integrals. In this paper, lower and upper bounds on ergodic capacity for kth best path are presented. These bounds
Higher order capacity statistics of multi-hop transmission systems over Rayleigh fading channels
Yilmaz, Ferkan; Tabassum, Hina; Alouini, Mohamed-Slim
2012-01-01
In this paper, we present an exact analytical expression to evaluate the higher order statistics of the channel capacity for amplify and forward (AF) multihop transmission systems operating over Rayleigh fading channels. Furthermore, we present
Achievable capacity of a spectrum sharing system over hyper fading channels
Ekin, Sabit
2009-11-01
Cognitive radio with spectrum sharing feature is a promising technique to address the spectrum under-utilization problem in dynamically changing environments. In this paper, achievable capacity gain of spectrum sharing systems over dynamic fading environments is studied. For the analysis, a theoretical fading model called hyper fading model that is suitable to the dynamic nature of cognitive radio channel is proposed. Closed-form expression of probability density function (PDF) and cumulative density function (CDF) of the signal-to-noise ratio (SNR) for secondary users in spectrum sharing systems are derived. In addition, the capacity gains achievable with spectrum sharing systems in high and low power regions are obtained. Numerical simulations are performed to study the effects of different fading figures, average powers, interference temperature, and number of secondary users on the achievable capacity.
A tone-aided dual vestigial sideband system for digital communications on fading channels
Hladik, Stephen M.; Saulnier, Gary J.; Rafferty, William
1989-01-01
A spectrally efficient tone-aided dual vestigial sideband (TA/DVSB) system for digital data communications on fading channels is presented and described analytically. This PSK (phase-shift-keying) system incorporates a feed-forward, tone-aided demodulation technique to compensate for Doppler frequency shift and channel- induced, multipath fading. In contrast to other tone-in-band-type systems, receiver synchronization is derived from the complete data VSBs. Simulation results for the Rician fading channel are presented. These results demonstrate the receiver's ability to mitigate performance degradation due to fading and to obtain proper data carrier synchronization, suggesting that the proposed TA/DVSB system has promise for this application. Simulated BER (bit-error rate) data indicate that the TA/DVSB system effectively alleviates the channel distortions of the land mobile satellite application.
Rached, Nadhir B.; Kammoun, Abla; Alouini, Mohamed-Slim; Tempone, Raul
2016-01-01
The outage capacity (OC) is among the most important performance metrics of communication systems over fading channels. The evaluation of the OC, when equal gain combining (EGC) or maximum ratio combining (MRC) diversity techniques are employed
On Outage Performance of Spectrum-Sharing Communication over M-Block Fading
Alabbasi, AbdulRahman; Rezki, Zouheir; Shihada, Basem
2015-01-01
In this paper, we consider a cognitive radio system in which a block-fading channel is assumed. Each transmission frame consists of M blocks and each block undergoes a different channel gain. Instantaneous channel state information about
Song, Xuegui; Cheng, Julian; Alouini, Mohamed-Slim
2014-01-01
Using an auxiliary random variable technique, we prove that binary differential phase-shift keying and binary phase-shift keying have the same asymptotic bit-error rate performance in lognormal fading channels. We also show that differential quaternary phase-shift keying is exactly 2.32 dB worse than quaternary phase-shift keying over the lognormal fading channels in high signal-to-noise ratio regimes.
Muir, K.; Brown, C.; Madill, A.
2015-01-01
The intensity of negative emotions associated with event memories fades to a greater extent over time than positive emotions (Fading Affect Bias or FAB). In this study, we examine how the presence and behaviour of a listener during social disclosure influences the FAB and the linguistic characteristics of event narratives. Participants recalled pleasant and unpleasant events and rated each event for its emotional intensity. Recalled events were then allocated to one of three experimental cond...
Spoon-to-Cup Fading as Treatment for Cup Drinking in a Child with Intestinal Failure
Groff, Rebecca A.; Piazza, Cathleen C.; Zeleny, Jason R.; Dempsey, Jack R.
2011-01-01
We treated a child with intestinal failure who consumed solids on a spoon but not liquids from a cup. We used spoon-to-cup fading, which consisted of taping a spoon to a cup and then gradually moving the bowl of the spoon closer to the edge of the cup. Spoon-to-cup fading was effective for increasing consumption of liquids from a cup. (Contains 2…
SPOON-TO-CUP FADING AS TREATMENT FOR CUP DRINKING IN A CHILD WITH INTESTINAL FAILURE
Groff, Rebecca A; Piazza, Cathleen C; Zeleny, Jason R; Dempsey, Jack R
2011-01-01
We treated a child with intestinal failure who consumed solids on a spoon but not liquids from a cup. We used spoon-to-cup fading, which consisted of taping a spoon to a cup and then gradually moving the bowl of the spoon closer to the edge of the cup. Spoon-to-cup fading was effective for increasing consumption of liquids from a cup.
Asymptotic SER performance comparison of MPSK and MDPSK in wireless fading channels
Song, Xuegui
2015-02-01
We propose a general framework to investigate asymptotic relative performance between M-ary phase-shift keying (MPSK) and M-ary differential phase-shift keying (MDPSK) in wireless fading channels. Using this framework, we provide an alternative derivation for the closed-form expression of the asymptotic performance loss of MDPSK w.r.t. MPSK in an additive white Gaussian noise channel. The same performance loss is also shown to be true for the lognormal fading channels.
Asymptotic SER performance comparison of MPSK and MDPSK in wireless fading channels
Song, Xuegui; Yang, Fan; Cheng, Julian; Alouini, Mohamed-Slim
2015-01-01
We propose a general framework to investigate asymptotic relative performance between M-ary phase-shift keying (MPSK) and M-ary differential phase-shift keying (MDPSK) in wireless fading channels. Using this framework, we provide an alternative derivation for the closed-form expression of the asymptotic performance loss of MDPSK w.r.t. MPSK in an additive white Gaussian noise channel. The same performance loss is also shown to be true for the lognormal fading channels.
Song, Xuegui
2014-09-01
Using an auxiliary random variable technique, we prove that binary differential phase-shift keying and binary phase-shift keying have the same asymptotic bit-error rate performance in lognormal fading channels. We also show that differential quaternary phase-shift keying is exactly 2.32 dB worse than quaternary phase-shift keying over the lognormal fading channels in high signal-to-noise ratio regimes.
Lu, Xiaodong; Mori, Kinji
The market and users' requirements have been rapidly changing and diversified. Under these heterogeneous and dynamic situations, not only the system structure itself, but also the accessible information services would be changed constantly. To cope with the continuously changing conditions of service provision and utilization, Faded Information Field (FIF) has been proposed, which is a agent-based distributed information service system architecture. In the case of a mono-service request, the system is designed to improve users' access time and preserve load balancing through the information structure. However, with interdependent requests of multi-service increasing, adaptability and timeliness have to be assured by the system. In this paper, the relationship that exists among the correlated services and the users' preferences for separate and integrated services is clarified. Based on these factors, the autonomous preference-aware information services integration technology to provide one-stop service for users multi-service requests is proposed. As compared to the conventional system, we show that proposed technology is able to reduce the total access time.
Timely event-related synchronization fading and phase de-locking and their defects in migraine.
Yum, Myung-Kul; Moon, Jin-Hwa; Kang, Joong Koo; Kwon, Oh-Young; Park, Ki-Jong; Shon, Young-Min; Lee, Il Keun; Jung, Ki-Young
2014-07-01
To investigate the characteristics of event-related synchronization (ERS) fading and phase de-locking of alpha waves during passive auditory stimulation (PAS) in the migraine patients. The subjects were 16 adult women with migraine and 16 normal controls. Electroencephalographic (EEG) data obtained during PAS with standard (SS) and deviant stimuli (DS) were used. Alpha ERS fading, the phase locking index (PLI) and de-locking index (DLI) were evaluated from the 10 Hz complex Morlet wavelet components at 100 ms (t100) and 300 ms (t300) after PAS. At t100, significant ERS was found with SS and DS in the migraineurs and controls (P=0.000). At t300 in the controls, ERS faded to zero for DS while in the migraineurs there was no fading for DS. In both groups the PLI for SS and DS was significantly reduced, i.e. de-locked, at t300 compared to t100 (P=0.000). In the migraineurs, the DLI for DS was significantly lower than in the controls (P=0.003). The alpha ERS fading and phase de-locking are defective in migraineurs during passive auditory cognitive processing. The defects in timely alpha ERS fading and in de-locking may play a role in the different attention processing in migraine patients. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
General Switch-and-Stay Combing for Space Diversity over Rayleigh Fading Channels
Directory of Open Access Journals (Sweden)
Yawgeng A. Chau
2012-01-01
Full Text Available Three multibranch switch-and-stay combining (MSSC schemes are analyzed for Rayleigh fading channels, where different decision statistics for antenna switching (i.e., switch statistic are used. Let a and r denote the fading factor and the received baseband signal of a diversity branch, respectively. In contrast to the traditional MSSC that uses the faded signal-to-noise ratio (SNR of diversity branches as the corresponding switch statistic, to enhance the receiver performance, |r|, |ar|, and a new linear combination of a and |r| are used as switch statistics of the three MSSC schemes, respectively. For performance evaluation, the bit error rate (BER of BPSK is derived for the three MSSC schemes over both independent-and-identical distributed (i.i.d. and independent-and-nonidentical distributed (i.n.d. Rayleigh fading channels. To pursue optimal performance, the locally optimal switch threshold (ST of each MSSC scheme is obtained for general i.n.d. fading channels. In addition, the locally optimal ST becomes the globally optimal ST for i.i.d. channels. Numerical results based on the analysis and simulations are presented. In contrast to the MSSC over i.i.d. fading channels, we will show that the performance of MSSC schemes can be improved by increasing the number of branches, if i.n.d. channels are considered.
Capacity limits of spectrum-sharing systems over hyper-fading channels
Ekin, Sabit
2011-01-20
Cognitive radio (CR) with spectrum-sharing feature is a promising technique to address the spectrum under-utilization problem in dynamically changing environments. In this paper, the achievable capacity gain of spectrum-sharing systems over dynamic fading environments is studied. To perform a general analysis, a theoretical fading model called hyper-fading model that is suitable to the dynamic nature of CR channel is proposed. Closed-form expressions of probability density function (PDF) and cumulative density function (CDF) of the signal-to-noise ratio (SNR) for secondary users (SUs) in spectrum-sharing systems are derived. In addition, the capacity gains achievable with spectrum-sharing systems in high and low power regions are obtained. The effects of different fading figures, average fading powers, interference temperatures, peak powers of secondary transmitters, and numbers of SUs on the achievable capacity are investigated. The analytical and simulation results show that the fading figure of the channel between SUs and primary base-station (PBS), which describes the diversity of the channel, does not contribute significantly to the system performance gain. © 2011 John Wiley & Sons, Ltd.
Wireless Transmission of Big Data: A Transmission Time Analysis over Fading Channel
Wang, Wen-Jing; Yang, Hong-Chuan; Alouini, Mohamed-Slim
2018-01-01
In this paper, we investigate the transmission time of a large amount of data over fading wireless channel with adaptive modulation and coding (AMC). Unlike traditional transmission systems, where the transmission time of a fixed amount of data is typically regarded as a constant, the transmission time with AMC becomes a random variable, as the transmission rate varies with the fading channel condition. To facilitate the design and optimization of wireless transmission schemes for big data applications, we present an analytical framework to determine statistical characterizations for the transmission time of big data with AMC. In particular, we derive the exact statistics of transmission time over block fading channels. The probability mass function (PMF) and cumulative distribution function (CDF) of transmission time are obtained for both slow and fast fading scenarios. We further extend our analysis to Markov channel, where transmission time becomes the sum of a sequence of exponentially distributed time slots. Analytical expression for the probability density function (PDF) of transmission time is derived for both fast fading and slow fading scenarios. These analytical results are essential to the optimal design and performance analysis of future wireless transmission systems for big data applications.
Wireless Transmission of Big Data: A Transmission Time Analysis over Fading Channel
Wang, Wen-Jing
2018-04-10
In this paper, we investigate the transmission time of a large amount of data over fading wireless channel with adaptive modulation and coding (AMC). Unlike traditional transmission systems, where the transmission time of a fixed amount of data is typically regarded as a constant, the transmission time with AMC becomes a random variable, as the transmission rate varies with the fading channel condition. To facilitate the design and optimization of wireless transmission schemes for big data applications, we present an analytical framework to determine statistical characterizations for the transmission time of big data with AMC. In particular, we derive the exact statistics of transmission time over block fading channels. The probability mass function (PMF) and cumulative distribution function (CDF) of transmission time are obtained for both slow and fast fading scenarios. We further extend our analysis to Markov channel, where transmission time becomes the sum of a sequence of exponentially distributed time slots. Analytical expression for the probability density function (PDF) of transmission time is derived for both fast fading and slow fading scenarios. These analytical results are essential to the optimal design and performance analysis of future wireless transmission systems for big data applications.
International Nuclear Information System (INIS)
Rasheedy, M.S.; El-Sherif, M.A.; Hefni, M.A.
2008-01-01
Thermoluminescence solid-state detector is widely used to determine the dose in personnel and environmental monitoring for radiation protection purposes, for instance in the field of nuclear power production, medicine and research. However, thermal fading is a limiting factor for a long-term application, especially where temperature is changing significantly during the accumulation period. This paper studied the influence of temperature and duration of storage after irradiation on the thermal fading of the TL signal. Also, this paper discussed the dependence of the thermal fading on the trap parameters of TL glow peak. The most important parameters, which were considered here include the order of kinetics b, the depth of the trap level E (eV) and the frequency factor S (s-1). The dependence of the thermal fading on thermal stability parameters, namely trap depths and frequency factors for the glow peaks is discussed. The variation of the thermal fading as a function of the order of kinetics is demonstrated. In addition, this paper discussed the dependence of the thermal fading on the absorbed dose in case of first-, second- and general-order kinetics. The above-mentioned studies were arranged considering the models of first-, second- and general-order of kinetics
Capacity limits of spectrum-sharing systems over hyper-fading channels
Ekin, Sabit; Yilmaz, Ferkan; Ç elebi, Hasari Burak; Qaraqe, Khalid A.; Alouini, Mohamed-Slim; Serpedin, Erchin
2011-01-01
Cognitive radio (CR) with spectrum-sharing feature is a promising technique to address the spectrum under-utilization problem in dynamically changing environments. In this paper, the achievable capacity gain of spectrum-sharing systems over dynamic fading environments is studied. To perform a general analysis, a theoretical fading model called hyper-fading model that is suitable to the dynamic nature of CR channel is proposed. Closed-form expressions of probability density function (PDF) and cumulative density function (CDF) of the signal-to-noise ratio (SNR) for secondary users (SUs) in spectrum-sharing systems are derived. In addition, the capacity gains achievable with spectrum-sharing systems in high and low power regions are obtained. The effects of different fading figures, average fading powers, interference temperatures, peak powers of secondary transmitters, and numbers of SUs on the achievable capacity are investigated. The analytical and simulation results show that the fading figure of the channel between SUs and primary base-station (PBS), which describes the diversity of the channel, does not contribute significantly to the system performance gain. © 2011 John Wiley & Sons, Ltd.
Moments Based Framework for Performance Analysis of One-Way/Two-Way CSI-Assisted AF Relaying
Xia, Minghua; Aissa, Sonia
2012-01-01
tractability, channels considered in such studies are generally assumed to be subject to Rayleigh fading or to be Nakagami-$m$ channels with integer fading parameters, which is impractical in typical urban environments. In this paper, we propose a unified
International Nuclear Information System (INIS)
Gu, Weijun; Sun, Zechang; Wei, Xuezhe; Dai, Haifeng
2014-01-01
Highlights: • Describe the aging mechanism of lithium-ion battery with electrochemical kinetics. • Establish the fading rate equation based on Eyring Equation. • The established equation is applicable to any reaction order. • Integrate the internal kinetics with external degradation characteristics. - Abstract: Battery life prediction is one of the critical issues that restrict the development of electric vehicles. Among the typical battery life models, the mechanism model focusing on the internal physical or electrochemical processes has a stronger theoretical foundation and greater accuracy. The empirical formula, which relies on the simplified mechanism, has a concise model structure and more flexibility in vehicle applications. However, the internal aging mechanism rarely correlates with the external operating characteristics. Based on the summary of the capacity fading mechanism and the reasoning of the internal kinetics of side reactions during the aging process, a lifetime model of the lithium-ion battery is established in this paper. The solutions to the vital parameters based on the external accelerated life testing results are also presented. The testing sample is a manganese oxide lithium-ion battery of 8 Ah. The validation results indicated that the life model established in this paper can describe the capacity fading law of the lithium-ion battery and the operability and accuracy for vehicle applications
Mohamed, Refaat; Ismail, Mahmoud H.; Newagy, Fatma; Mourad, Heba M.
2013-03-01
Stemming from the fact that the α-μ fading distribution is one of the very general fading models used in the literature to describe the small scale fading phenomenon, in this paper, closed-form expressions for the Shannon capacity of the α-μ fading channel operating under four main adaptive transmission strategies are derived assuming integer values for μ. These expressions are derived for the case of no diversity as well as for selection combining diversity with independent and identically distributed branches. The obtained expressions reduce to those previously derived in the literature for the Weibull as well as the Rayleigh fading cases, which are both special cases of the α-μ channel. Numerical results are presented for the capacity under the four adaptive transmission strategies and the effect of the fading parameter as well as the number of diversity branches is studied.
Channel allocation and rate adaptation for relayed transmission over correlated fading channels
Hwang, Kyusung; Hossain, Md Jahangir; Ko, Youngchai; Alouini, Mohamed-Slim
2009-01-01
at both the source and relay nodes, we develop an optimal channel allocation and rate adaptation policy for a dual-hop relayed transmission. As such the overall transmit power for the relayed system is minimized while a target packet dropping rate (PDR
Al-Murad, Tamim M.; Ghogho, Mounir; Swami, Ananthram
2010-01-01
of the wireless channels, extra care should be taken when performing this sampling. In this paper, we develop expressions for the distortion which include the channel effects. The asymptotic behavior of the distortion as the number of sensors or total transmit
Energy-Efficient Optimization for HARQ Schemes over Time-Correlated Fading Channels
Shi, Zheng; Ma, Shaodan; Yang, Guanghua; Alouini, Mohamed-Slim
2018-01-01
in the optimization, which further differentiates this work from prior ones. Using a unified expression of asymptotic outage probabilities, optimal transmission powers and optimal rate are derived in closed-forms to maximize the energy efficiency while satisfying
Errorless discrimination and picture fading as techniques for teaching sight words to TMR students.
Walsh, B F; Lamberts, F
1979-03-01
The effectiveness of two approaches for teaching beginning sight words to 30 TMR students was compared. In Dorry and Zeaman's picture-fading technique, words are taught through association with pictures that are faded out over a series of trials, while in the Edmark program errorless-discrimination technique, words are taught through shaped sequences of visual and auditory--visual matching-to-sample, with the target word first appearing alone and eventually appearing with orthographically similar words. Students were instructed on two lists of 10 words each, one list in the picture-fading and one in the discrimination method, in a double counter-balanced, repeated-measures design. Covariance analysis on three measures (word identification, word recognition, and picture--word matching) showed highly significant differences between the two methods. Students' performance was better after instruction with the errorless-discrimination method than after instruction with the picture-fading method. The findings on picture fading were interpreted as indicating a possible failure of the shifting of control from picture to printed word that earlier researchers have hypothesized as occurring.
Robust Automatic Modulation Classification Technique for Fading Channels via Deep Neural Network
Directory of Open Access Journals (Sweden)
Jung Hwan Lee
2017-08-01
Full Text Available In this paper, we propose a deep neural network (DNN-based automatic modulation classification (AMC for digital communications. While conventional AMC techniques perform well for additive white Gaussian noise (AWGN channels, classification accuracy degrades for fading channels where the amplitude and phase of channel gain change in time. The key contributions of this paper are in two phases. First, we analyze the effectiveness of a variety of statistical features for AMC task in fading channels. We reveal that the features that are shown to be effective for fading channels are different from those known to be good for AWGN channels. Second, we introduce a new enhanced AMC technique based on DNN method. We use the extensive and diverse set of statistical features found in our study for the DNN-based classifier. The fully connected feedforward network with four hidden layers are trained to classify the modulation class for several fading scenarios. Numerical evaluation shows that the proposed technique offers significant performance gain over the existing AMC methods in fading channels.
On Amplify-and-Forward Relaying Over Hyper-Rayleigh Fading Channels
Directory of Open Access Journals (Sweden)
S. H. Alvi
2014-12-01
Full Text Available Relayed transmission holds promise for the next generation of wireless communication systems due to the performance gains it can provide over non-cooperative systems. Recently hyper-Rayleigh fading, which represents fading conditions more severe than Rayleigh fading, has received attention in the context of many practical communication scenarios. Though power allocation for Amplify-and-Forward (AF relaying networks has been studied in the literature, a theoretical analysis of the power allocation problem for hyper-Rayleigh fading channels is a novel contribution of this work. We develop an optimal power allocation (OPA strategy for a dual-hop AF relaying network in which the relay-destination link experiences hyper-Rayleigh fading. A new closed-form expression for the average signal-to-noise ratio (SNR at destination is derived and it is shown to provide a new upper-bound on the average SNR at destination, which outperforms a previously proposed upper-bound based on the well-known harmonic-geometric mean inequality. An OPA across the source and relay nodes, subject to a sum-power constraint, is proposed and it is shown to provide measurable performance gains in average SNR and SNR outage at the destination relative to the case of equal power allocation.
International Nuclear Information System (INIS)
Usenko, Vladyslav C; Filip, Radim; Heim, Bettina; Peuntinger, Christian; Wittmann, Christoffer; Marquardt, Christoph; Leuchs, Gerd
2012-01-01
Entanglement properties of Gaussian states of light as well as the security of continuous variable quantum key distribution with Gaussian states in free-space fading channels are studied. These qualities are shown to be sensitive to the statistical properties of the transmittance distribution in the cases when entanglement is strong or when channel excess noise is present. Fading, i.e. transmission fluctuations, caused by beam wandering due to atmospheric turbulence, is a frequent challenge in free-space communication. We introduce a method of fading discrimination and subsequent post-selection of the corresponding sub-states and show that it can improve the entanglement resource and restore the security of the key distribution over a realistic fading link. Furthermore, the optimal post-selection strategy in combination with an optimized entangled resource is shown to drastically increase the protocol's robustness to excess noise, which is confirmed for experimentally measured fading channel characteristics. The stability of the result against finite data ensemble size and imperfect channel estimation is also addressed. (paper)
A short-time fading study of Al2O3:C
International Nuclear Information System (INIS)
Nascimento, L.F.; Vanhavere, F.; Silva, E.H.; Deene, Y. De
2015-01-01
This paper studies the short-time fading from Al 2 O 3 :C by measuring optically stimulated luminescence (OSL) signals (Total OSL: T OSL , and Peak OSL: P OSL ) from droplets and Luxel™ pellets. The influence of various bleaching regimes (blue, green and white) and light power is compared. The fading effect is the decay of the OSL signal in the dark at room temperature. Al 2 O 3 :C detectors were submitted to various bleaching regimes, irradiated with a reference dose and read out after different time spans. Investigations were carried out using 2 mm size droplet detectors, made of thin Al 2 O 3 :C powder mixed with a photocured polymer. Tests were compared to Luxel™-type detectors (Landauer Inc.). Short-time post-irradiation fading is present in OSL results (T OSL and P OSL ) droplets for time spans up to 200 s. The effect of short-time fading can be lowered/removed when treating the detectors with high-power and/or long time bleaching regimes; this result was observed in both T OSL and P OSL from droplets and Luxel™. - Highlights: • Droplet composed of thin powder of Al 2 O 3 :C was prepared using a photo-curable polymer. • Powder grain sizes ranged from 5 μm to 35 μm. • Short-time fading was measured for irradiated samples. • Various bleaching regimes and light power was tested. • Droplets were compared to a commercially dosimeter, Luxel™
A practical approach towards minimisation of latent image fading in personnel monitoring films
International Nuclear Information System (INIS)
Dhond, R.V.; Patel, P.H.; Shenoy, K.S.; Adtani, M.M.
1980-01-01
A serious drawback of the film badges used in personnel monitoring is the latent image fading often as high as 95% when they are subjected to extreme climatic conditions such as high humidities and temperatures. Current data on latent image fading in personnel monitoring films of various brands of manufacturers (Kodak, Agfa-Gevaert, Du Pont) are summarized. If individual film packs are hermitically sealed in polythene envelopes, fading is reduced to 20%. Studies were, therefore, conducted on Kodak type 2 films to observe the radiation response of films subjected alternatively to humid (20deg C and 90% r.h.) conditions for 8 hours and dry (20deg C and 30 to 40% r.h.) conditions for 16 hours with a view to find out a practicable and simple method to minimise the error due to fading. The films were then exposed to 600, 1200, 2400 and 4800 mR of radium-226 gammas after one week of storage and replaced in their experimental conditions. The films were processed after zero, one and two weeks of their storage in their respective conditions. Dose versus density curves of films were plotted. A fading less than 10% is shown for a storage period of two weeks. It is also suggested that films be kept in a desiccator having dry silica gel crystals during the periods when they are not being worn by the radiation workers. (M.G.B.)
Schott, Timm Cornelius; Göz, Gernot
2011-03-01
To evaluate the color fading in aqueous solutions of the blue dot wear-compliance indicators of the Invisalign Teen® System outside the oral cavity. The compliance indicators in the Invisalign Teen aligners were tested for color resistance in various aqueous models with no saliva involved. Color fading was observed as a function of time, pH, and temperature while compliance indicators were stored in drinking water or sour soft drinks and in conjunction with the use of cleaning tablets and a dishwasher. The findings of color fading were consistent with the color changes observed when the aligners were being worn by patients. Color fading, notably as observed in connection with acidic soft drinks and cleaning techniques, introduces uncertainty into the assessment of actual patient compliance, as reflected by the fading colors of compliance indicators. Compliance indicators are not immune to simple intentional or unintentional manipulations. Therefore, they can best show an estimate of wear time but cannot be recommended as objective wear-time indicators.
EFFECTS OF RICIAN FADING ON THE OPERATION OF AERONAUTICAL SATELLITE OFDM CHANNEL
Directory of Open Access Journals (Sweden)
Volodymyr Kharchenko
2016-06-01
Full Text Available The aim of this study is to investigate the influence of Rician fading on messages transmission via the aeronautical satellite OFDM channel with adaptive modulation and the development of a method for estimating the parameters of such a channel. Methods: To study the effect of Rician fading on messages transmission via aeronautical satellite OFDM channel with adaptive modulation the original model of the communication channel “Aircraft-Satellite-Ground Station” was built using software package MATLAB Sіmulіnk. The model includes “Aircraft Transmitter”, “Uplink/Downlink Path”, “Satellite Transponder”, and “Ground Station Receiver”. Each modulator block in the modulation bank performs convolutional coding and puncturing using code rates of ½, ²/3, and ¾, data interleaving, BPSK, QPSK, 16-QAM, and 64-QAM modulation. Results: Dependences of Estimated channel SNR on the ratio between the power of the LOS component and the diffuse component, on the downlink gain and delay in the diffuse component for different Doppler spectrum types and Doppler frequency offsets were obtained. A method for estimating the parameters of the satellite channels with fading was proposed. Discussion: The realistic model of aeronautical satellite OFDM link with Rician fading is developed for the first time on a basis of IEEE 802.11a standard and used for channel parameters evaluation. Proposed in this article approach can be considered as a method for estimating parameters of the channel with fading.
Cornelissen, Gerard; Jubaedah; Nurida, Neneng L; Hale, Sarah E; Martinsen, Vegard; Silvani, Ludovica; Mulder, Jan
2018-09-01
Low fertility limits crop production on acidic soils dominating much of the humid tropics. Biochar may be used as a soil enhancer, but little consensus exists on its effect on crop yield. Here we use a controlled, replicated and long-term field study in Sumatra, Indonesia, to investigate the longevity and mechanism of the effects of two contrasting biochars (produced from rice husk and cacao shell, and applied at dosages of 5 and 15tha -1 ) on maize production in a highly acidic Ultisol (pH KCl 3.6). Compared to rice husk biochar, cacao shell biochar exhibited a higher pH (9.8 vs. 8.4), CEC (197 vs. 20cmol c kg -1 ) and acid neutralizing capacity (217 vs. 45cmol c kg -1 ) and thus had a greater liming potential. Crop yield effects of cacao shell biochar (15tha -1 ) were also much stronger than those of rice husk biochar, and could be related to more favorable Ca/Al ratios in response to cacao shell biochar (1.0 to 1.5) compared to rice husk biochar (0.3 to 0.6) and nonamended plots (0.15 to 0.6). The maize yield obtained with the cacao shell biochar peaked in season 2, continued to have a good effect in seasons 3-4, and faded in season 5. The yield effect of the rice husk biochar was less pronounced and already faded from season 2 onwards. Crop yields were correlated with the pH-related parameters Ca/Al ratio, base saturation and exchangeable K. The positive effects of cocoa shell biochar on crop yield in this Ultisol were at least in part related to alleviation of soil acidity. The fading effectiveness after multiple growth seasons, possibly due to leaching of the biochar-associated alkalinity, indicates that 15tha -1 of cocoa shell biochar needs to be applied approximately every third season in order to maintain positive effects on yield. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.
Multiple-Symbol Decision-Feedback Space-Time Differential Decoding in Fading Channels
Directory of Open Access Journals (Sweden)
Wang Xiaodong
2002-01-01
Full Text Available Space-time differential coding (STDC is an effective technique for exploiting transmitter diversity while it does not require the channel state information at the receiver. However, like conventional differential modulation schemes, it exhibits an error floor in fading channels. In this paper, we develop an STDC decoding technique based on multiple-symbol detection and decision-feedback, which makes use of the second-order statistic of the fading processes and has a very low computational complexity. This decoding method can significantly lower the error floor of the conventional STDC decoding algorithm, especially in fast fading channels. The application of the proposed multiple-symbol decision-feedback STDC decoding technique in orthogonal frequency-division multiplexing (OFDM system is also discussed.
Trait anxiety reduces affective fading for both positive and negative autobiographical memories.
Walker, W Richard; Yancu, Cecile N; Skowronski, John J
2014-01-01
The affect associated with negative events fades faster than the affect associated with positive events (the Fading Affect Bias; the FAB). The research that we report examined the relation between trait anxiety and the FAB. Study 1 assessed anxiety using the Depression, Anxiety, and Stress Scale; Studies 2 and 3 used the Beck Anxiety Inventory. Studies 1 and 2 used retrospective procedures to probe positive event memories and negative event memories while Study 3 used a diary procedure. The results of all 3 studies showed that increased anxiety was associated with both a lowered FAB and lower overall affect fading for both positive events and negative events. These results suggest that for people free of trait anxiety, the FAB reflects the operation of a healthy coping mechanism in autobiographical memory that is disrupted by trait anxiety.
Yilmaz, Ferkan
2011-11-01
In this paper, in contrast to the relay selection protocols available in the literature, we propose a partial relay selection protocol utilizing only the shadowing side information of the relays instead of their full channel side information in order to select a relay in a dual-hop relaying system through the available limited feedback channels and power budget. We then presented an exact unified performance expression combining the average bit error probability, ergodic capacity, and moments-generating function of the proposed partial relay selection over generalized fading channels. Referring to the unified performance expression introduced in [1], we explicitly offer a generic unified performance expression that can be easily calculated and that is applicable to a wide variety of fading scenarios. Finally, as an illustration of the mathematical formalism, some numerical and simulation results are generated for an extended generalized-K fading environment, and these numerical and simulation results are shown to be in perfect agreement. © 2011 IEEE.
On the capacity of Rician fading channels with full channel state information at low SNR
Rezki, Zouheir
2012-06-01
The capacity of flat Rayleigh fading channels with full channel state information (CSI) at the transmitter and at the receiver at asymptotically low SNR has been recently shown to scale essentially as SNR log (1/SNR). In this paper, we investigate the Rician fading channel capacity with full CSI, and show that the capacity of this channel scales essentially as 1/1+K SNR log (1 /SNR), where K is the Rician factor. This characterization includes perfect CSI at both the transmitter and the receiver or noisy CSI at the transmitter and perfect CSI at the receiver. We also show that one-bit CSI at the transmitter is enough to achieve this asymptotic capacity using an On-Off power control scheme. Our framework may be seen as a generalization of previous works as it captures the Rayleigh fading channel as a special case by letting K goes to zero. © 2012 IEEE.
A pancultural perspective on the fading affect bias in autobiographical memory.
Ritchie, Timothy D; Batteson, Tamzin J; Bohn, Annette; Crawford, Matthew T; Ferguson, Georgie V; Schrauf, Robert W; Vogl, Rodney J; Walker, W Richard
2015-01-01
The fading affect bias (FAB) refers to the negative affect associated with autobiographical events fading faster than the positive affect associated with such events, a reliable and valid valence effect established by researchers in the USA. The present study examined the idea that the FAB is a ubiquitous emotion regulating phenomenon in autobiographical memory that is present in people from a variety of cultures. We tested for evidence of the FAB by sampling more than 2400 autobiographical event descriptions from 562 participants in 10 cultures around the world. Using variations on a common method, each sample evidenced a FAB: positive affect faded slower than negative affect did. Results suggest that in tandem with local norms and customs, the FAB may foster recovery from negative life events and promote the retention of the positive emotions, within and outside of the USA. We discuss these findings in the context of Keltner and Haidt's levels of analysis theory of emotion and culture.
A Novel Criterion for Optimum MultilevelCoding Systems in Mobile Fading Channels
Institute of Scientific and Technical Information of China (English)
YUAN Dongfeng; WANG Chengxiang; YAO Qi; CAO Zhigang
2001-01-01
A novel criterion that is "capac-ity rule" and "mapping rule" for the design of op-timum MLC scheme over mobile fading channels isproposed.According to this theory,the performanceof multilevel coding with multistage decoding schemes(MLC/MSD) in mobile fading channels is investi-gated,in which BCH codes are chosen as componentcodes,and three mapping strategies with 8ASK mod-ulation are used.Numerical results indicate that whencode rates of component codes in MLC scheme are de-signed based on "capacity rule",the performance ofthe system with block partitioning (BP) is optimumfor Rayleigh fading channels,while the performance ofthe system with Ungerboeck partioning (UP) is bestfor AWGN channels.
Ansari, Imran Shafique
2010-12-01
The introduction of new schemes that are based on the communication among nodes has motivated the use of composite fading models due to the fact that the nodes experience different multipath fading and shadowing statistics, which subsequently determines the required statistics for the performance analysis of different transceivers. The end-to-end signal-to-noise-ratio (SNR) statistics plays an essential role in the determination of the performance of cascaded digital communication systems. In this thesis, a closed-form expression for the probability density function (PDF) of the end-end SNR for independent but not necessarily identically distributed (i.n.i.d.) cascaded generalized-K (GK) composite fading channels is derived. The developed PDF expression in terms of the Meijer-G function allows the derivation of subsequent performance metrics, applicable to different modulation schemes, including outage probability, bit error rate for coherent as well as non-coherent systems, and average channel capacity that provides insights into the performance of a digital communication system operating in N cascaded GK composite fading environment. Another line of research that was motivated by the introduction of composite fading channels is the error performance. Error performance is one of the main performance measures and derivation of its closed-form expression has proved to be quite involved for certain systems. Hence, in this thesis, a unified closed-form expression, applicable to different binary modulation schemes, for the bit error rate of dual-branch selection diversity based systems undergoing i.n.i.d. GK fading is derived in terms of the extended generalized bivariate Meijer G-function.
MGF approach to the capacity analysis of Generalized Two-Ray fading models
Rao, Milind
2015-09-11
We propose a class of Generalized Two-Ray (GTR) fading channels that consists of two line of sight (LOS) components with random phase and a diffuse component. Observing that the GTR fading model can be expressed in terms of the underlying Rician distribution, we derive a closed-form expression for the moment generating function (MGF) of the signal-to-noise ratio (SNR) of this model. We then employ this approach to compute the ergodic capacity with receiver side information. The impact of the underlying phase difference between the LOS components on the average SNR of the signal received is also illustrated. © 2015 IEEE.
Higher order capacity statistics of multi-hop transmission systems over Rayleigh fading channels
Yilmaz, Ferkan
2012-03-01
In this paper, we present an exact analytical expression to evaluate the higher order statistics of the channel capacity for amplify and forward (AF) multihop transmission systems operating over Rayleigh fading channels. Furthermore, we present simple and efficient closed-form expression to the higher order moments of the channel capacity of dual hop transmission system with Rayleigh fading channels. In order to analyze the behavior of the higher order capacity statistics and investigate the usefulness of the mathematical analysis, some selected numerical and simulation results are presented. Our results are found to be in perfect agreement. © 2012 IEEE.
Sungjoon Park,
2011-11-01
In this paper we present opportunistic relay communication strategies of decode and forward relaying. The channel that we are considering includes pathloss, shadowing, and fast fading effects. We find a simple outage probability formula for opportunistic relaying in the channel, and validate the results by comparing it with the exact outage probability. Also, we suggest a new relay selection algorithm that incorporates shadowing. We consider a protocol of broadcasting the channel gain of the previously selected relay. This saves resources in slow fading channel by reducing collisions in relay selection. We further investigate the optimal relay selection period to maximize the throughput while avoiding selection overhead. © 2011 IEEE.
MGF approach to the capacity analysis of Generalized Two-Ray fading models
Rao, Milind; Lopez-Martinez, F. Javier; Alouini, Mohamed-Slim; Goldsmith, Andrea
2015-01-01
We propose a class of Generalized Two-Ray (GTR) fading channels that consists of two line of sight (LOS) components with random phase and a diffuse component. Observing that the GTR fading model can be expressed in terms of the underlying Rician distribution, we derive a closed-form expression for the moment generating function (MGF) of the signal-to-noise ratio (SNR) of this model. We then employ this approach to compute the ergodic capacity with receiver side information. The impact of the underlying phase difference between the LOS components on the average SNR of the signal received is also illustrated. © 2015 IEEE.
International Nuclear Information System (INIS)
Paglietti, A.
1978-01-01
This paper is concerned with the thermodynamical theory of materials with fading memory exhibiting the creep and relaxation properties. It is shown that, once the current thermodynamical approach is followed, the second principle of thermodynamics implies for these materials further restrictions on the free-energy functional in addition to the well-known ones deduced in the general theory of materials with fading memory. The possibility of an experimental check of the current approach and the possibility of an alternative and more general approach are briefly discussed. (author)
An Empirical Rate Constant Based Model to Study Capacity Fading in Lithium Ion Batteries
Directory of Open Access Journals (Sweden)
Srivatsan Ramesh
2015-01-01
Full Text Available A one-dimensional model based on solvent diffusion and kinetics to study the formation of the SEI (solid electrolyte interphase layer and its impact on the capacity of a lithium ion battery is developed. The model uses the earlier work on silicon oxidation but studies the kinetic limitations of the SEI growth process. The rate constant of the SEI formation reaction at the anode is seen to play a major role in film formation. The kinetics of the reactions for capacity fading for various battery systems are studied and the rate constants are evaluated. The model is used to fit the capacity fade in different battery systems.
Gibbons, Jeffrey A; Horowitz, Kyle A; Dunlap, Spencer M
2017-08-01
Unpleasant affect fades faster than pleasant affect (e.g., Walker, Vogl, & Thompson, 1997); this effect is referred to as the Fading Affect Bias (FAB; Walker, Skowronski, Gibbons, Vogl, & Thompson, 2003a). Research shows that the FAB is consistently related to positive/healthy outcomes at a general but not at a specific level of analysis based on event types and individual differences (e.g., Gibbons et al., 2013). Based on the positive outcomes for FAB and negative outcomes for social media (Bolton et al., 2013; Huang, 2010), the current study examined FAB in the context of social media events along with related individual differences. General positive outcomes were shown in the form of robust FAB effects across social media and non-social media events, a larger FAB for non-social media events than for social media events, negative correlations of FAB with depression, anxiety, and stress as well as a positive correlation of FAB with self-esteem. However, the lack of a negative correlation between FAB and anxiety for social media events in a 3-way interaction did not show positive outcomes at a specific level of analysis. Rehearsal ratings mediated the 3-way interaction. Implications are discussed. Copyright © 2017 Elsevier Inc. All rights reserved.
Yilmaz, Ferkan; Alouini, Mohamed-Slim
2012-01-01
function (MGF)-based unified expression for the ABEP and AC of single and multiple link communications with maximal ratio combining. In addition, this paper proposes the hyper-Fox's H fading model as a unified fading distribution of a majority of the well
DEFF Research Database (Denmark)
Yamamoto, Atsushi; Sakata, T.; Hayashi, T.
2010-01-01
This paper presents a MIMO spatial fading emulator, used to represent a street microcell environment. The fading emulator can reproduce a multipath radio propagation environment with either a uniform or non-uniform angular power spectrum (APS) in the horizontal plane. In this paper, we used...
Kingry, Mary Ann
2012-01-01
The effects of instructional fading using completion problems on student performance were investigated in this study. Instructional fading is the gradual withdrawal of the amount of assistance provided to the student and was accomplished in this study using completion problems. They were used to gradually transition the student from completely…
Lindeman, Meghan I H; Zengel, Bettina; Skowronski, John J
2017-07-01
The affect associated with negative (or unpleasant) memories typically tends to fade faster than the affect associated with positive (or pleasant) memories, a phenomenon called the fading affect bias (FAB). We conducted a study to explore the mechanisms related to the FAB. A retrospective recall procedure was used to obtain three self-report measures (memory vividness, rehearsal frequency, affective fading) for both positive events and negative events. Affect for positive events faded less than affect for negative events, and positive events were recalled more vividly than negative events. The perceived vividness of an event (memory vividness) and the extent to which an event has been rehearsed (rehearsal frequency) were explored as possible mediators of the relation between event valence and affect fading. Additional models conceived of affect fading and rehearsal frequency as contributors to a memory's vividness. Results suggested that memory vividness was a plausible mediator of the relation between an event's valence and affect fading. Rehearsal frequency was also a plausible mediator of this relation, but only via its effects on memory vividness. Additional modelling results suggested that affect fading and rehearsal frequency were both plausible mediators of the relation between an event's valence and the event's rated memory vividness.
Yilmaz, Ferkan
2012-07-01
Analysis of the average binary error probabilities (ABEP) and average capacity (AC) of wireless communications systems over generalized fading channels have been considered separately in past years. This paper introduces a novel moment generating function (MGF)-based unified expression for the ABEP and AC of single and multiple link communications with maximal ratio combining. In addition, this paper proposes the hyper-Fox\\'s H fading model as a unified fading distribution of a majority of the well-known generalized fading environments. As such, the authors offer a generic unified performance expression that can be easily calculated, and that is applicable to a wide variety of fading scenarios. The mathematical formulism is illustrated with some selected numerical examples that validate the correctness of the authors\\' newly derived results. © 1972-2012 IEEE.
Nadeem, Qurrat-Ul-Ain; Kammoun, Abla; Debbah, Merouane; Alouini, Mohamed-Slim
2015-01-01
Previous studies have confirmed the adverse impact of fading correlation on the mutual information (MI) of two-dimensional (2D) multiple-input multiple-output (MIMO) systems. More recently, the trend is to enhance the system performance
Campbell, Todd; Longhurst, Max; Duffy, Aaron M.; Wolf, Paul G.; Nagy, Robin
2012-01-01
Teaching science as inquiry is advocated in all national science education documents and by leading science and science teaching organizations. In addition to teaching science as inquiry, we recognize that learning experiences need to connect to students' lives. This article details how we use a sequence of faded scaffolded inquiry supported by…
The fading phase of Igbo language and culture: path to its ...
African Journals Online (AJOL)
The fading phase of Igbo language and culture: path to its revitalisation. ... philosophy of the Igbo man towards himself, his environment and his personal effects, and has discovered that the bane of Igbo language and culture is the Igbo man's attitude towards that which is his, and his easy enchantment with foreign cultures.
Capacity Fade and Its Mitigation in Li-Ion Cells with Silicon-Graphite Electrodes
Energy Technology Data Exchange (ETDEWEB)
Bareño, Javier [Chemical; Shkrob, Ilya A. [Chemical; Gilbert, James A. [Chemical; Klett, Matilda [Chemical; Abraham, Daniel P. [Chemical
2017-09-15
In this study we scrutinize the causes for capacity fade in lithium-ion cells containing silicongraphite (Si-Gr) blends in the negative electrode and examine approaches for minimizing this fade. The causal mechanisms are inferred from data obtained by electrochemistry, microscopy, spectroscopy and thermogravimetry techniques. The presence of SiOxFy signals in the Si-Gr electrode, LixPOyFz compounds in the electrolyte, and SiO2 species on the NCM523 positive electrode, highlight the crucial role of hydrolytically generated HF, which accelerates the degradation of Si particles. The hydrolysis could result from residual moisture in the current electrode fabrication process, which uses aqueous binders. Water can also be released when silanol groups on the Si nanoparticles react with HF to form Si-F compounds. We note that the primary cause of capacity fade in the full cells is the loss of solid electrolyte interphase (SEI) integrity resulting from volume changes in Si particles during electrochemical cycling. Adding fluoroethylene carbonate (FEC) to the conventional electrolyte slows capacity fade through the formation of a cross linked polymer with elastomeric properties. Further gains in cell longevity are possible by excluding water during electrode fabrication, using hydrolytically stable lithium salts, and adopting electrolyte systems that provide more elasticity to the SEI layers.
Parent-Implemented Bedtime Fading and Positive Routines for Children with Autism Spectrum Disorders
Delemere, Emma; Dounavi, Katerina
2018-01-01
Sleep disorders affect a large portion of those with autism spectrum disorder. Behavioural interventions have been found to increase appropriate sleep behaviours. This study sought to examine the efficacy of two stimulus control interventions (bedtime fading and positive routines) on total sleep duration, sleep onset latency and frequency and…
Exploring the Effects of Concreteness Fading across Grades in Elementary School Science Education
Jaakkola, Tomi; Veermans, Koen
2018-01-01
The present study investigates the effects that concreteness fading has on learning and transfer across three grade levels (4-6) in elementary school science education in comparison to learning with constantly concrete representations. 127 9- to 12-years-old elementary school students studied electric circuits in a computer-based simulation…
Noise-based frequency offset modulation in wideband frequency-selective fading channels
Meijerink, Arjan; Cotton, S.L.; Bentum, Marinus Jan; Scanlon, W.G.
2009-01-01
A frequency offset modulation scheme using wideband noise carriers is considered. The main advantage of such a scheme is that it enables fast receiver synchronization without channel adaptation, while providing robustness to multipath fading and in-band interference. This is important for low-power
On Channel Estimation for OFDM/TDM Using MMSE-FDE in a Fast Fading Channel
Directory of Open Access Journals (Sweden)
Gacanin Haris
2009-01-01
Full Text Available Abstract MMSE-FDE can improve the transmission performance of OFDM combined with time division multiplexing (OFDM/TDM, but knowledge of the channel state information and the noise variance is required to compute the MMSE weight. In this paper, a performance evaluation of OFDM/TDM using MMSE-FDE with pilot-assisted channel estimation over a fast fading channel is presented. To improve the tracking ability against fast fading a robust pilot-assisted channel estimation is presented that uses time-domain filtering on a slot-by-slot basis and frequency-domain interpolation. We derive the mean square error (MSE of the channel estimator and then discuss a tradeoff between improving the tracking ability against fading and the noise reduction. The achievable bit error rate (BER performance is evaluated by computer simulation and compared with conventional OFDM. It is shown that the OFDM/TDM using MMSE-FDE achieves a lower BER and a better tracking ability against fast fading in comparison with conventional OFDM.
Wake Up: The American Dream Is Fading, and Our Future Is at Risk.
Martin, David
1988-01-01
Citing some alarming statistics concerning our aging population, declining middle-class birthrates, a burgeoning underclass, and the broadening gap between the rich and poor, this article deplores our society's inability to confront the fading "American Dream" and urges schools to begin recruiting more poor and minority children to the middle…
BER analysis for MPAM signal constellations in the presence of fading and ADC quantization noise
Rizvi, U.H.; Janssen, G.J.M.; Weber, J.H.
2009-01-01
In this letter, closed-form expressions for the bit error rate of M-ary pulse amplitude modulated signal constellations as a function of the analog-to-digital converter word length, the signal-to-noise ratio and the fading distribution, are derived. These results allow for a rapid and accurate
Capacity Fade Analysis of Sulfur Cathodes in Lithium–Sulfur Batteries
Yan, Jianhua; Liu, Xingbo
2016-01-01
Rechargeable lithium–sulfur (Li–S) batteries are receiving ever‐increasing attention due to their high theoretical energy density and inexpensive raw sulfur materials. However, their rapid capacity fade has been one of the key barriers for their further improvement. It is well accepted that the major degradation mechanisms of S‐cathodes include low electrical conductivity of S and sulfides, precipitation of nonconductive Li2S2 and Li2S, and poly‐shuttle effects. To determine these degradation factors, a comprehensive study of sulfur cathodes with different amounts of electrolytes is presented here. A survey of the fundamentals of Li–S chemistry with respect to capacity fade is first conducted; then, the parameters obtained through electrochemical performance and characterization are used to determine the key causes of capacity fade in Li–S batteries. It is confirmed that the formation and accumulation of nonconductive Li2S2/Li2S films on sulfur cathode surfaces are the major parameters contributing to the rapid capacity fade of Li–S batteries. PMID:27981001
Directory of Open Access Journals (Sweden)
Manal Abd-ElAziz Abd-ElZaher
2014-06-01
Full Text Available Disappearing ink is a type of ink which could be used to forge documents as it will fade away without any trace within 40–65 h. Erasable ink is another type of ink easily removed by certain rubbers incorporated in each pen. Both types of inks were applied separately on different types of papers (checks, standard white foolscap, and plain white A4 paper. For vanishing ink, it was observed visually in the first 6 h and then every 6 h. It was found that the vanishing ink disappeared completely within 2 h on checks, 36 h on standard white foolscap paper, and 40 h on plain white A4 paper. For erasable ink, the written strokes were manipulated manually using the incorporated eraser. Deciphering the faded writing failed by the conventional methods, but oblique light can reveal the indentation marks. The faded writing became visible when treated with weak alkaline (NaOH solutions. Erasable ink was deciphered with the aid of infra-red radiation combined with VSC-6000 as clear white traces against red fluorescence. It was concluded that the use of a weak (NaOH solution is an effective method for revealing the faded writing, and the infra-red illumination is also effective.
The Effects of Reinforcer Pairing and Fading on Preschoolers' Snack Selections
Solberg, Katherine M.; Hanley, Gregory P.; Layer, Stacy A.; Ingvarsson, Einar T.
2007-01-01
The effects of reinforcement pairing and fading on preschoolers' snack selections were evaluated in a multiple baseline design. Baseline preferences for snack options were assessed via repeated paired-item preference assessments. Edible, social, and activity-based reinforcers were then exclusively paired with a less preferred snack option. Once…
Fading of CaSO4 thermoluminescent detectors after exposure to charged particles
Czech Academy of Sciences Publication Activity Database
Pachnerová Brabcová, Kateřina; Štěpán, Václav; Kubančák, Ján; Davídková, Marie; Ambrožová, Iva
2017-01-01
Roč. 106, č. 12 (2017), s. 569-572 ISSN 1350-4487 R&D Projects: GA ČR GJ15-16622Y Institutional support: RVO:61389005 Keywords : thermoluminescent detectors * CaSO4:Dy * fading * charged particles Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders OBOR OECD: Nuclear physics Impact factor: 1.442, year: 2016
International Nuclear Information System (INIS)
Su, Laisuo; Zhang, Jianbo; Wang, Caijuan; Zhang, Yakun; Li, Zhe; Song, Yang; Jin, Ting; Ma, Zhao
2016-01-01
Highlights: • The effect of seven principal factors on the aging behavior of lithium ion cells is studied. • Orthogonal design of experiments is used to reduce the experiment units. • Capacity fades linearly during the initial 10% capacity fading period. • Statistical methods are used to compare the significance of each principal factor. • A multi-factor statistical model is developed to predict the aging rate of cells. - Abstract: The aging rate under cycling conditions for lithium-ion cells is affected by many factors. Seven principal factors are systematically examined using orthogonal design of experiments, and statistical analysis was used to identify the order of principal factors in terms of strength in causing capacity fade. These seven principal factors are: the charge and discharge currents (i_1, i_2) during the constant current regime, the charge and discharge cut-off voltages (V_1, V_2) and the corresponding durations (t_1, t_2) during the constant voltage regime, and the ambient temperature (T). An orthogonal array with 18 test units was selected for the experiments. The test results show that (1) during the initial 10% capacity fading period, the capacity faded linearly with Wh-throughput for all the test conditions; (2) after the initial period, certain cycling conditions exacerbated aging rates, while the others remain the same. The statistical results show that: (1) except for t_1, the other six principal factors significantly affect the aging rate; (2) the strength of the principal factors was ranked as: i_1 > V_1 > T > t_2 > V_2 > i_2 > t_1. Finally, a multi-factor statistical aging model is developed to predict the aging rate, and the accuracy of the model is validated.
International Nuclear Information System (INIS)
Ohuchi, H.; Yamadera, A.
2002-01-01
We have been investigating the fading characteristics of imaging plates (IPs) as integral type detectors. The dependence on alpha, beta, and gamma ray radiation and their energies of the fading effect was measured using three types of IPs (BAS-UR, BAS-TR, and BAS-MS). The functions to correct the fading were determined by using the method reported in a previous paper. In all types of IPs, we confirmed that the fading effect is independent of the energy of the incident particles of beta and gamma rays and also independent of radiation except for the first component, which fades out in a very short time after irradiation with alpha rays. These results are very useful in the utilization of IPs as integral detectors in practical radiation fields. Empirically, the fading pattern is known to change when the IP is scanned by different types of image readers. The differences in the fading patterns obtained with two types of image readers, the BAS-1000 and the BAS-5000 (Fuji Film Co.), is discussed. Development of an equation for correcting the effects of the differences in the image readers was attempted
Zhou, Y; Foltis, L; Moore, D J; Rigoletto, R
2009-01-01
The fading of oxidative color in hair as a result of daily shampoo washing activities has become a common problem and a source of frequent complaints by consumers. The fading occurs primarily through hair dye solubility in water. One aspect of the current study investigates the physical and chemical factors that influence hair color fading during the washing process. This is accomplished by testing hair dye dissolution in water from dyed hair samples with variation of surfactant type, pH, and hair type. Furthermore, a new approach to preventing color fading is developed aiming to provide an effective barrier function for hair dye from dissolving into water. The preliminary investigation of a series of polymers with various functional groups indicates that polymers with hydrophobically modified and cationic functionalities are most effective in preventing hair dye dissolution in water. It is also evident that a synergistic effect of the polymer's hydrophobic moieties and cationic charges are important on hair color protection during shampoo washing processes. A primary example of a polymer within this category is a cationic terpolymer of vinylpyrrolidone, dimethylaminopropyl methacrylamide, and methacryloylaminopropyl lauryldimonium chloride (INCI: Polyquaternium-55). The color protection benefit of this polymer is evaluated using newly developed methodologies for evaluating hair color changes, such as hair color fading tests through multiple shampoo washes with mannequin heads and hair tresses, both derived from human hair, colorimetry, and quantitative digital image analysis. In addition, new infrared spectroscopic imaging techniques are used to detect the hair dye deposition behavior inside hair fibers both with and without the color protection treatment. Both visual and instrumental measurement results indicate that Polyquaternium-55 provides a high level of color protection when formulated in a hair color protection regimen with up to 50% color protection. This
Evaluation of fading factor and self-dose for glass dosimeter and thermoluminescence dosimeter
International Nuclear Information System (INIS)
Yamasaki, T.; Yamanishi, H.; Miyake, H.; Komura, K.
2000-01-01
The glass dosimeter (GD) and thermoluminescence dosimeter (TLD) are both passive radiation detectors. They are often used for measuring environmental radiation. In order to measure low dose rate preciously, it is important to evaluate decreased dose due to fading and self-dose during the exposure period. We evaluate the fading factor and self-dose of thee passive detectors, GD and TLD. We select Ogoya tunnel for the experiment. The tunnel is suitable field for measuring faded dose and self-dose because it is low cosmic radiation. At the center of the tunnel, the intensity of cosmic ray is reduced to about 1/177 than the outside of the funnel. We prepared two sets of dosimeters. One set consists of five GDs, five TLDs and some pre-irradiated GDs and TLDs that are exposed to standard radiation of 4 mGy by Cs-137. These dosimeters are put in the 10 cm thick lead box in order to shield the terrestrial gamma ray. One set is located at the center of the tunnel and the other is the outside of the funnel. The dosimeters were exposed for ten months, from May 1998 to March 1999. After the exposure, the readers of dosimeters are carried into the funnel to read out the signals promptly as soon as taking out the dosimeters. As a result of the measurement, four kinds of data are taken for GD and TLD respectively. Assumed that the self-dose and cosmic ray are constant during exposure, the four independent unknown quantities, a self-dose a dose due to cosmic ray and a fading coefficient at the center of the tunnel and at the outside, are considered. Therefore four simultaneous equations should be obtained. From these examinations, the faded dose of GD is less than 1%, but that of TLD is about 16% during ten months. The coefficient for compensation of fading of GD and TLD is given as the half of the each value. At the outside of the tunnel, the measured dose rate of cosmic ray that can pass through the 10 cm lead is evaluated to be about 16 nGy/h by both detectors. The self
Ning, G.; Shum, P.
2007-06-01
We derive the expressions for the power fading including first-order polarization mode dispersion (PMD), chromatic dispersion, chirp parameter as well as polarization-dependent chromatic dispersion (PCD), which is dependent on the angle of precession of output state of polarization around the PMD vector. From the expression for radio frequency (RF) signals power fading, we get the average power fading for chromatic dispersion, chirp parameter, first-order PMD and PCD for both double sideband (DSB) modulation and single sideband (SSB) modulation. We also demonstrate a fast PMD and chromatic dispersion monitoring technology with reduced polarization-dependent gain. The measured results agree well with theoretical analysis.
Gering, Kevin L
2013-08-27
A system includes an electrochemical cell, monitoring hardware, and a computing system. The monitoring hardware periodically samples performance characteristics of the electrochemical cell. The computing system determines cell information from the performance characteristics of the electrochemical cell. The computing system also develops a mechanistic level model of the electrochemical cell to determine performance fade characteristics of the electrochemical cell and analyzing the mechanistic level model to estimate performance fade characteristics over aging of a similar electrochemical cell. The mechanistic level model uses first constant-current pulses applied to the electrochemical cell at a first aging period and at three or more current values bracketing a first exchange current density. The mechanistic level model also is based on second constant-current pulses applied to the electrochemical cell at a second aging period and at three or more current values bracketing the second exchange current density.
Rached, Nadhir B.
2016-01-06
The outage capacity (OC) is among the most important performance metrics of communication systems over fading channels. The evaluation of the OC, when equal gain combining (EGC) or maximum ratio combining (MRC) diversity techniques are employed, boils down to computing the cumulative distribution function (CDF) of the sum of channel envelopes (equivalently amplitudes) for EGC or channel gains (equivalently squared enveloped/ amplitudes) for MRC. Closed-form expressions of the CDF of the sum of many generalized fading variates are generally unknown and constitute open problems. We develop a unified hazard rate twisting Importance Sampling (IS) based approach to efficiently estimate the CDF of the sum of independent arbitrary variates. The proposed IS estimator is shown to achieve an asymptotic optimality criterion, which clearly guarantees its efficiency. Some selected simulation results are also shown to illustrate the substantial computational gain achieved by the proposed IS scheme over crude Monte Carlo simulations.
Transmit selection for imperfect threshold-based receive MRC in Rayleigh fading channels
Radaydeh, Redha Mahmoud Mesleh
2010-01-01
The performance of multiple-antenna diversity systems in which the receiver combines signal replicas per thresholdbased maximal ratio combining (MRC) and the transmitter uses only a single antenna according to receive combined signal strength is studied. The impact of imperfect channel estimation is considered when the received signal replicas undergo independent and flat multipath fading. The analysis is applicable for arbitrary transmit antenna selection when the multiple-antenna channels experience identically distributed and non-identically distributed Rayleigh fading conditions. New closed-form expressions for the combined SNR statistics and some performance measures are presented. The system models adopted herein and the presented analytical results can be used to study the performance of different system architectures under various channel conditions when the implementation complexity is of interest. © 2009 IEEE.
On the capacity of cognitive radio under limited channel state information over fading channels
Rezki, Zouheir
2011-06-01
A spectrum-sharing communication system where the secondary user is aware of the instantaneous channel state information (CSI) of the secondary link, but knows only the statistics and an estimated version of the secondary transmitter-primary receiver (ST-PR) link, is investigated. The optimum power profile and the ergodic capacity of the secondary link are derived for general fading channels (with continuous probability density function) under average and peak transmit-power constraints and with respect to two different interference constraints: an interference outage constraint and a signal-to-interference (SI) outage constraint. When applied to Rayleigh fading channels, our results show, for instance, that the interference constraint is harmful at high-power regime, whereas at low-power regime, it has a marginal impact and no-interference performance may be achieved. © 2011 IEEE.
Turbo coding, turbo equalisation and space-time coding for transmission over fading channels
Hanzo, L; Yeap, B
2002-01-01
Against the backdrop of the emerging 3G wireless personal communications standards and broadband access network standard proposals, this volume covers a range of coding and transmission aspects for transmission over fading wireless channels. It presents the most important classic channel coding issues and also the exciting advances of the last decade, such as turbo coding, turbo equalisation and space-time coding. It endeavours to be the first book with explicit emphasis on channel coding for transmission over wireless channels. Divided into 4 parts: Part 1 - explains the necessary background for novices. It aims to be both an easy reading text book and a deep research monograph. Part 2 - provides detailed coverage of turbo conventional and turbo block coding considering the known decoding algorithms and their performance over Gaussian as well as narrowband and wideband fading channels. Part 3 - comprehensively discusses both space-time block and space-time trellis coding for the first time in literature. Par...
On the outage capacity of the block fading channel at low-power regime
Rezki, Zouheir
2014-06-01
Outage performance of the M-block fading with additive white Gaussian noise (BF-AWGN) is investigated at low-power regime. We consider delay-constrained constant-rate communications with perfect channel state information (CSI) at both the transmitter and the receiver (CSI-TR), under a short-term power constraint. We show that selection diversity that allocates all the power to the strongest block is asymptotically optimal. Then, we provide a simple characterization of the outage probability in the regime of interest. We quantify the reward due to CSI-TR over the constant-rate constant-power scheme and show that this reward increases with the delay constraint. For instance, for Rayleigh fading, we find that a power gain up to 4.3 dB is achievable. © 2014 IEEE.
Delay-limited capacity of fading multiple access and broadcast channels in the low power regime
Rezki, Zouheir
2015-09-11
We study delay-limited (also called zero-outage) capacity region of the fading multi-access channel (MAC) with Gaussian noise and perfect channel state information (CSI) at the receiver and at the transmitters (CSI-TR), in the low-power regime. We show that for fading channels where the MAC capacity region is strictly positive, it has a multidimensional rectangle structure and thus is simply characterized by single user capacity points. More specifically, we show that at low power, the boundary surface of the capacity region shrinks to a single point corresponding to the sum-rate maximizer and that the coordinates of this point coincide with single user capacity bounds. Using the duality of the Gaussian MAC and broadcast channels (BC), we show that time-sharing (or time division multiple access (TDMA)) is asymptotically optimal. © 2015 IEEE.
Rached, Nadhir B.
2015-06-14
The outage capacity (OC) is among the most important performance metrics of communication systems over fading channels. The evaluation of the OC, when Equal Gain Combining (EGC) or Maximum Ratio Combining (MRC) diversity techniques are employed, boils down to computing the Cumulative Distribution Function (CDF) of the sum of channel envelopes (equivalently amplitudes) for EGC or channel gain (equivalently squared enveloped/amplitudes) for MRC. Closed-form expressions of the CDF of the sum of many generalized fading variates are generally unknown and constitute open problems. In this paper, we develop a unified hazard rate twisting Importance Sampling (IS) based approach to efficiently estimate the CDF of the sum of independent arbitrary variates. The proposed IS estimator is shown to achieve an asymptotic optimality criterion, which clearly guarantees its efficiency. Some selected simulation results are also shown to illustrate the substantial computational gain achieved by the proposed IS scheme over crude Monte-Carlo simulations.
Electrochemical capacity fading of polyaniline electrode in supercapacitor: An XPS analysis
Directory of Open Access Journals (Sweden)
Jinxing Deng
2017-04-01
Full Text Available To understand the electrochemical capacity fading of the polyaniline (PANI electrodes in supercapacitors, for the first time, their chemical structure change during electrochemical cycles was traced with XPS analysis after the HCl doped PANI electrodes were subjected to the cyclic voltammetry test in 1.0 M H2SO4 electrolyte for different cycle numbers. The results showed that the chlorine disappeared in the electrode surface, while the surface element contents of sulfur and oxygen increased with the electrochemical cycles increased. It demonstrated that the hydrolytic degradation of the PANI chains and exchange of dopant occurred during the electrochemical cycling, causing the fading in the mechanical and electrochemical performance of the PANI electrodes. This understanding should lead to better design of the conductive polymer-based energy storage devices.
Directory of Open Access Journals (Sweden)
Juinn-Horng Deng
2012-01-01
Full Text Available Single carrier block transmission (SCBT system has become one of the most popular modulation systems due to its low peak-to-average power ratio (PAPR, and it is gradually considered to be used for uplink wireless communication systems. In this paper, a low complexity partial parallel interference cancellation (PIC with maximum ratio combining (MRC technology is proposed to use for receiver to combat the intersymbol interference (ISI problem over multipath fading channel. With the aid of MRC scheme, the proposed partial PIC technique can effectively perform the interference cancellation and acquire the benefit of time diversity gain. Finally, the proposed system can be extended to use for multiple antenna systems to provide excellent performance. Simulation results reveal that the proposed low complexity partial PIC-MRC SIMO system can provide robust performance and outperform the conventional PIC and the iterative frequency domain decision feedback equalizer (FD-DFE systems over multipath fading channel environment.
On Outage Performance of Spectrum-Sharing Communication over M-Block Fading
Alabbasi, AbdulRahman
2015-12-06
In this paper, we consider a cognitive radio system in which a block-fading channel is assumed. Each transmission frame consists of M blocks and each block undergoes a different channel gain. Instantaneous channel state information about the interference links remains unknown to the primary and secondary users. We minimize the secondary user\\'s targeted outage probability over the block-fading channels. To protect the primary user, a statistical constraint on its targeted outage probability is enforced. The secondary user\\'s targeted outage region and the corresponding optimal power are derived. We also propose two sub-optimal power strategies and derive compact expressions for the corresponding outage probabilities. These probabilities are shown to be asymptotic lower and upper bounds on the outage probability. Utilizing these bounds, we derive the exact diversity order of the secondary user outage probability. Selected numerical results are presented to characterize the system\\'s behavior.
Design and Performance Analysis of MISO-ORM-DCSK System over Rayleigh Fading Channels
Directory of Open Access Journals (Sweden)
Gang Zhang
2016-01-01
Full Text Available A novel chaotic communication system, named Orthogonality-based Reference Modulated-Differential Chaos Shift Keying (ORM-DCSK, is proposed to enhance the performance of RM-DCSK. By designing an orthogonal chaotic generator (OCG, the intrasignal interference components in RM-DCSK are eliminated. Also, the signal frame format is expanded so the average bit energy is reduced. As a result, the proposed system has less interference in decision variables. Furthermore, to investigate the bit error rate (BER performance over Rayleigh fading channels, the MISO-ORM-DCSK is studied. The BER expressions of the new system are derived and analyzed over AWGN channel and multipath Rayleigh fading channel. All simulation results not only show that the proposed system can obtain significant improvement but also verify the analysis in theory.
Design of an anti-Rician-fading modem for mobile satellite communication systems
Kojima, Toshiharu; Ishizu, Fumio; Miyake, Makoto; Murakami, Keishi; Fujino, Tadashi
1995-01-01
To design a demodulator applicable to mobile satellite communication systems using differential phase shift keying modulation, we have developed key technologies including an anti-Rician-fading demodulation scheme, an initial acquisition scheme, automatic gain control (AGC), automatic frequency control (AFC), and bit timing recovery (BTR). Using these technologies, we have developed one-chip digital signal processor (DSP) modem for mobile terminal, which is compact, of light weight, and of low power consumption. Results of performance test show that the developed DSP modem achieves good performance in terms of bit error ratio in mobile satellite communication environment, i.e., Rician fading channel. It is also shown that the initial acquisition scheme acquires received signal rapidly even if the carrier-to-noise power ratio (CNR) of the received signal is considerably low.
Directory of Open Access Journals (Sweden)
Surbhi Sharma
2011-06-01
Full Text Available Irregular low-density parity-check (LDPC codes have been found to show exceptionally good performance for single antenna systems over a wide class of channels. In this paper, the performance of LDPC codes with multiple antenna systems is investigated in flat Rayleigh and Rician fading channels for different modulation schemes. The focus of attention is mainly on the concatenation of irregular LDPC codes with complex orthogonal space-time codes. Iterative decoding is carried out with a density evolution method that sets a threshold above which the code performs well. For the proposed concatenated system, the simulation results show that the QAM technique achieves a higher coding gain of 8.8 dB and 3.2 dB over the QPSK technique in Rician (LOS and Rayleigh (NLOS faded environments respectively.
Multicarrier chaotic communications in multipath fading channels without channel estimation
Energy Technology Data Exchange (ETDEWEB)
Wang, Shilian, E-mail: wangsl@nudt.edu.cn; Zhang, Zhili [College of Electrical Science and Engineering, National University of Defense Technology, Changsha, 410073, P R China (China)
2015-01-15
A multi-carrier chaotic shift keying(MC-CSK) communication scheme with low probability of interception(LPI) is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM) subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK) in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.
Multicarrier chaotic communications in multipath fading channels without channel estimation
Directory of Open Access Journals (Sweden)
Shilian Wang
2015-01-01
Full Text Available A multi-carrier chaotic shift keying(MC-CSK communication scheme with low probability of interception(LPI is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.
Rached, Nadhir B.; Kammoun, Abla; Alouini, Mohamed-Slim; Tempone, Raul
2015-01-01
The outage capacity (OC) is among the most important performance metrics of communication systems operating over fading channels. Of interest in the present paper is the evaluation of the OC at the output of the Equal Gain Combining (EGC) and the Maximum Ratio Combining (MRC) receivers. In this case, it can be seen that this problem turns out to be that of computing the Cumulative Distribution Function (CDF) for the sum of independent random variables. Since finding a closedform expression for the CDF of the sum distribution is out of reach for a wide class of commonly used distributions, methods based on Monte Carlo (MC) simulations take pride of price. In order to allow for the estimation of the operating range of small outage probabilities, it is of paramount importance to develop fast and efficient estimation methods as naive Monte Carlo (MC) simulations would require high computational complexity. In this line, we propose in this work two unified, yet efficient, hazard rate twisting Importance Sampling (IS) based approaches that efficiently estimate the OC of MRC or EGC diversity techniques over generalized independent fading channels. The first estimator is shown to possess the asymptotic optimality criterion and applies for arbitrary fading models, whereas the second one achieves the well-desired bounded relative error property for the majority of the well-known fading variates. Moreover, the second estimator is shown to achieve the asymptotic optimality property under the particular Log-normal environment. Some selected simulation results are finally provided in order to illustrate the substantial computational gain achieved by the proposed IS schemes over naive MC simulations.
Global Existence of Classical Solutions to the Equations of Motion for Materials with Fading Memory.
1984-02-01
influence function , history value problems, classical solutions, global existence, decay. Work Unit Number 1 - Applied Analysis Sponsored by the United...introduce an " influence function " h, intended to JIN. characterize the rate at which memory fades, and construct an LP-type space of admissible...histories using the influence function as a weight. Here we use the term influence function to mean a positive, nonincreasing, real-valued function h e L (0
International Nuclear Information System (INIS)
Sun, Xianzhong; Zhang, Xiong; Liu, Wenjie; Wang, Kai; Li, Chen; Li, Zhao; Ma, Yanwei
2017-01-01
Highlights: • Three-electrode pouch cell is used to investigate the capacity fading of AC/HC LIC. • the electrode potential swing is critical for the cycleability of a LIC cell. • Different capacity fading behaviors are discussed. • A large-capacity LIC pouch cell has been assembled with a specific energy of 18.1 Wh kg −1 based on the total weight. - Abstract: Lithium ion capacitor (LIC) is one of the most promising electrochemical energy storage devices, which offers rapid charging-discharging capability and long cycle life. We have fabricated LIC pouch cells using an electrochemically-driven lithium pre-doping method through a three-electrode pouch cell structure. The active materials of cathode and anode of LIC cell are activated carbon and pre-lithiated hard carbon, respectively. The electrochemical performances and the capacity fading behaviors of LICs in the voltage range of 2.0 − 4.0 V have been studied. The specific energy and specific power reach 73.6 Wh kg −1 and 11.9 kW kg −1 based on the weight of the active materials in both cathode and anode, respectively. Since the cycling performance is actually determined by hard carbon anode, the anode potential swings are emphasized. The capacity fading of LIC upon cycling is proposed to be caused by the increases of internal resistance and the consumption of lithium stored in anode. Finally, a large-capacity LIC pouch cell has been assembled with a maximum specific energy of 18.1 Wh kg −1 and a maximum specific power of 3.7 kW kg −1 based on the weight of the whole cell.
OFDM RF power-fading circumvention for long-reach WDM-PON.
Chow, C W; Yeh, C H; Sung, J Y
2014-10-06
We propose and demonstrate an orthogonal frequency division multiplexing (OFDM) radio-frequency (RF) power-fading circumvention scheme for long-reach wavelength-division-multiplexed passive-optical-network (LR-WDM-PON); hence the same capacity of 40 Gb/s can be provided to all the optical-networking-units (ONUs) in the LR-WDM-PON. Numerical analysis and proof-of-concept experiment are performed.
Apparatus and Method for Elimination of Polarization-Induced Fading in Fiber-optic Sensor System
Chan, Hon Man (Inventor); Parker, Jr., Allen R. (Inventor)
2015-01-01
The invention is an apparatus and method of eliminating polarization-induced fading in interferometric fiber-optic sensor system having a wavelength-swept laser optical signal. The interferometric return signal from the sensor arms are combined and provided to a multi-optical path detector assembly and ultimately to a data acquisition and processing unit by way of a switch that is time synchronized with the laser scan sweep cycle.
Liu, Xian
2010-02-10
This paper shows that optical signal transmission over intersatellite links with swaying transmitters can be described as an equivalent fading model. In this model, the instantaneous signal-to-noise ratio is stochastic and follows the reciprocal Pareto distribution. With this model, we show that the transmitter power can be minimized, subject to a specified outage probability, by appropriately adjusting some system parameters, such as the transmitter gain.
Rached, Nadhir B.
2015-11-13
The outage capacity (OC) is among the most important performance metrics of communication systems operating over fading channels. Of interest in the present paper is the evaluation of the OC at the output of the Equal Gain Combining (EGC) and the Maximum Ratio Combining (MRC) receivers. In this case, it can be seen that this problem turns out to be that of computing the Cumulative Distribution Function (CDF) for the sum of independent random variables. Since finding a closedform expression for the CDF of the sum distribution is out of reach for a wide class of commonly used distributions, methods based on Monte Carlo (MC) simulations take pride of price. In order to allow for the estimation of the operating range of small outage probabilities, it is of paramount importance to develop fast and efficient estimation methods as naive Monte Carlo (MC) simulations would require high computational complexity. In this line, we propose in this work two unified, yet efficient, hazard rate twisting Importance Sampling (IS) based approaches that efficiently estimate the OC of MRC or EGC diversity techniques over generalized independent fading channels. The first estimator is shown to possess the asymptotic optimality criterion and applies for arbitrary fading models, whereas the second one achieves the well-desired bounded relative error property for the majority of the well-known fading variates. Moreover, the second estimator is shown to achieve the asymptotic optimality property under the particular Log-normal environment. Some selected simulation results are finally provided in order to illustrate the substantial computational gain achieved by the proposed IS schemes over naive MC simulations.
The capacity of the cascaded fading channel in the low power regime
Benkhelifa, Fatma
2014-04-01
In this paper, we present a simple way to compute the ergodic capacity of cascaded channels with perfect channel state information at both the transmitter and the receiver. We apply our generic results to the Rayleigh-double fading channel, and to the free-space optical channel in the presence of pointing errors and we express their low signal-to-noise ratio capacities. We mainly focus on the low signal-to-noise ratio range.
Physical Layer Security for Cooperative Relaying Over Generalized-K Fading Channels
Wu, Ling; Yang, Liang; Chen, Jianchao; Alouini, Mohamed-Slim
2018-01-01
In this letter, we analyze the secrecy performance for a cooperative diversity system with amplify-and-forward (AF) over generalized-K fading channels. More specifically, some lower bounds on the secrecy performance, such as secure outage probability (SOP), average secrecy capacity (ASC), and strictly positive secrecy capacity (SPSC), are derived in closed-form. Finally, we provide simulation results to verify the accuracy of our analytical results.
Train of four fade in a child with stiff baby syndrome.
LENUS (Irish Health Repository)
Murphy, C
2012-02-03
A case is described of a child with stiff baby syndrome who underwent open reduction and femoral shortening of congenital dislocated hip under general anaesthesia. Neuromuscular function was measured electromyographically and demonstrated a great degree of train of four fade (57%) after sevoflurane inhalational induction of anaesthesia. The response to suxamethonium (2 mg x kg(-1)) was normal. The neuromuscular response to volatile anaesthetic agents and suxamethonium may be abnormal in these children with stiff baby syndrome and intraoperative neuromuscular monitoring is recommended.
Physical Layer Security for Cooperative Relaying Over Generalized-K Fading Channels
Wu, Ling
2018-02-02
In this letter, we analyze the secrecy performance for a cooperative diversity system with amplify-and-forward (AF) over generalized-K fading channels. More specifically, some lower bounds on the secrecy performance, such as secure outage probability (SOP), average secrecy capacity (ASC), and strictly positive secrecy capacity (SPSC), are derived in closed-form. Finally, we provide simulation results to verify the accuracy of our analytical results.
De Paula, E. R.; Moraes, A. D. O.; Vani, B. C.; Sobral, J. H. A.; Abdu, M. A.; Galera Monico, J. F.
2017-12-01
The ionosphere over the peak of the anomaly represents a treat for navigation systems based on GNSS. Brazilian territory is mostly under this harsh layer for satellite communication in general and in particular for navigation, like GPS users, where their receivers tracking performance are damaged under scintillation conditions. Ionospheric scintillation is responsible for significant degradation in the accuracy of navigation and positioning. Phase shifts accompanied by amplitude fades significantly degrades the signal-to-noise ratio of the received signal disrupting the channel and loosing navigation performance. The stronger the scintillations are, more difficulty will be for the GNSS receiver tracking loops to recover the phase and code replicas. These phenomena under specific geophysical conditions may severely affect the system availability and positioning. In this work the temporal characteristics of amplitude scintillation will be analyzed at the three available GPS frequencies, L1, L2C and L5. Aspect like fading duration and depth will be evaluated and compared among the three available frequencies for the current solar cycle. This work will use GPS scintillation data recorded during six months of data during 2014 to 2015 at three stations under Brazilian territory located near the southern crest of the equatorial ionization anomaly. The analysis will be performed focusing on the fading profile of the three frequencies comparing how the fading of those signals behave statistically between them. Aspects like loss of lock, spatial orientation between the signal across the ionospheric irregularity will also be discussed showing how much more susceptible the new frequencies might be in comparison to the widely used and studied L1 frequency.
Capacity bounds for kth best path selection over generalized fading channels
Hanif, Muhammad Fainan
2014-02-01
Exact ergodic capacity calculation for fading wireless channels typically involves time-consuming numerical evaluation of infinite integrals. In this paper, lower and upper bounds on ergodic capacity for kth best path are presented. These bounds have simple analytic expressions which allow their fast evaluation. Numerical results show that the newly proposed bounds closely approximate the exact ergodic capacity for a large variety of system configurations. © 1997-2012 IEEE.
Nam, Sungsik; Hasna, Mazen Omar; Alouini, Mohamed-Slim
2010-01-01
in mind, we capitalize in this paper on some new order statistics results to derive exact closed-form expressions for outage probability of GSC RAKE receivers subject to self-interference over independent and identically distributed Rayleigh fading
On the low SNR capacity of MIMO fading channels with imperfect channel state information
Benkhelifa, Fatma
2014-06-01
The capacity of multiple-input multiple-output (MIMO) Rayleigh fading channels with full knowledge of channel state information (CSI) at both the transmitter and the receiver (CSI-TR) has been shown recently to scale at low signal-to-noise ratio (SNR) essentially as SNR log(1/SNR), independently of the number of transmit and receive antennas. In this paper, we investigate the ergodic capacity of MIMO Rayleigh fading channel with estimated channel state information at the transmitter (CSI-T) and possibly imperfect channel state information at the receiver (CSI-R). Our framework can be seen as a generalization of previous works as it can capture the perfect CSI-TR as a special case when the estimation error variance goes to zero. In this paper, we mainly focus on the low SNR regime, and we show that the capacity scales as (1-α) SNR log(1/SNR), where α is the estimation error variance. This characterization shows the loss of performance due to error estimation over the perfect channel state information at both the transmitter and the receiver. As a by-product of our new analysis, we show that our framework can be also extended to characterize the capacity of MIMO Rician fading channels at low SNR with possibly imperfect CSI-T and CSI-R. © 1972-2012 IEEE.
Rezki, Zouheir
2013-06-01
We study the throughput capacity region of the Gaussian multiaccess (MAC) fading channel with perfect channel state information (CSI) at the receiver (CSI-R) and at the transmitters (CSI-T), at low power regime. We show that it has a multidimensional rectangle structure and thus is simply characterized by single user capacity points. More specifically, we show that at low power regime, the boundary surface of the capacity region shrinks to a single point corresponding to the sum rate maximizer and that the coordinates of this point coincide with single user capacity bounds. Inspired from this result, we propose an on-off scheme, compute its achievable rate, and provide a necessary condition on the fading channels under which this scheme achieves single user capacity bounds of the MAC channel at asymptotically low power regime. We argue that this necessary condition characterizes a class of fading that encompasses all known wireless channels, where the capacity region of the MAC channel has a simple expression in terms of users\\' average power constraints only. © 2013 IEEE.
On the low SNR capacity of MIMO fading channels with imperfect channel state information
Benkhelifa, Fatma
2014-05-01
The capacity of Multiple Input Multiple Output (MIMO) Rayleigh fading channels with full knowledge of channel state information (CSI) at both the transmitter and the receiver (CSI-TR) has been shown recently to scale at low Signal-to-Noise Ratio (SNR) essentially as SNR log(1=SNR), independently of the number of transmit and receive antennas. In this paper, we investigate the ergodic capacity of MIMO Rayleigh fading channel with estimated channel state information at the transmitter (CSI-T) and possibly imperfect channel state information at the receiver (CSI-R). Our framework can be seen as a generalization of previous works as it can capture the perfect CSI-TR as a special case when the estimation error variance goes to zero. In our work, we mainly focus on the low SNR regime and we show that the capacity scales as (1-α) SNR log(1=SNR), where α is the estimation error variance. This characterization shows the loss of performance due to error estimation over the perfect channel state information at both the transmitter and the receiver. As a by-product of our new analysis, we show that our framework can also be extended to characterize the capacity of MIMO Rician fading channels at low SNR with possibly imperfect CSI-T and CSI-R. © 2014 IFIP.
Directory of Open Access Journals (Sweden)
Jaek, Ivar
2007-09-01
Full Text Available According to many publications, alkali feldspars are characterized by specific athermal (anomalous fading of their thermoluminescence and optically-stimulated luminescence. This phenomenon is manifested as spontaneous decline in luminescence intensity over relatively long (months and years time after laboratory irradiation, possibly due to tunnelling of electrons from lattice defects and impurities acting as dosimetric traps. It can hamper reliable luminescent dating of Quaternary deposits on the basis of feldspar extractions due to possible unpredictable underestimation of the ages. In this paper we present some experimental results related to the manifestation of the phenomenon. It is found that, in general case, the assumed long-term anomalous fading cannot be connected to electron tunnelling from the deep dosimetric traps. At the same time, some decrease in the dosimetric luminescence signal observable in just irradiated feldspar samples can really be caused by tunnelling. However, the probability of this process quickly goes down, already within some days after irradiation. Interpretation of some other short- and long-term anomalous fading-like effects requires involvement of radiation- and thermo-induced ionic processes.
Study on the Effect of Calcium and Potassium Spray on Date Bunch Fading Disorder
Directory of Open Access Journals (Sweden)
Hosein Shekofteh
2017-09-01
Full Text Available Introduction: Date bunch fading disorder has been one of the most important problems, which caused economic damage to date plantation area of Iran. It has been first reported on Mozafti cultivar in Kahnuj area, Kerman province. It has often been observed on soft and mid ripening cultivars such as Mozafti, Mordaseng and Kalote. Furthermore, it usually appears on Mozafti cultivar when fruits change from Khalal to Rutab stage. The most important symptoms of this disorder are sudden wilting of fruits and necrotic strips on the upper surface of the main bunch stalk. Incidence and development of these symptoms increase by high temperature, low relative humidity, and hot and dry wind. Several research studies have been carried out on this disorder so far, but the only research about the effect of nutrition on disorder was performed by Rosta (2003. The aim of the present study was to investigate the effect of calcium and potassium spray on date bunch fading and some traits of date fruit in Rigan region, Kerman province. Materials and Methods: The experiment was conducted based on randomized complete block designs with three replicates in Rigan located in east south of Kerman province, Iran, in 2012. Treatments were: T1: control, T2: spray of calcium nitrate at the concentration of 5 ppm, T3: spray of potassium sulfate at the concentration of 5 ppm, and T4: combined spray of calcium nitrate and potassium sulfate at the concentration of 5 ppm. Treatments were applied at Kimri, Hobabok and Khalal stages. Sampling was performed from 3 date palms (3 bunches from each date palm were selected randomly at the second date harvest. Totally, the traits of 200 fruits were measured in each date palm. The traits measured in the present study were: fruit length, fruit diameter, fruit weight, stone weight, stone diameter, and bunch fading percentage. Results and Discussions: According to the data of variance analysis, treatments had a significant effect on wet fruit
A performance study of two hop transmission in mixed underlay RF and FSO fading channels
Ansari, Imran Shafique
2014-04-01
In this work, we present the performance analysis of a dual-hop transmission system composed of asymmetric radio frequency (RF) and free-space optical (FSO) links in underlay cognitive networks. For the RF link, we consider an underlay cognitive network where the secondary users share the spectrum with licensed primary users, where indoor femtocells act as a practical example for such networks. More specifically, we assume that the RF link is subject to an interference constraint. The FSO link accounts for pointing errors and both types of detection techniques (i.e. intensity modulation/direct detection (IM/DD) as well as heterodyne detection). On the other hand, RF link is modeled by the Rayleigh fading distribution that applies power control to maintain the interference at the primary network below a specific threshold whereas the FSO link is modeled by a unified Gamma-Gamma fading distribution. With this model, we derive new exact closed-form expressions for the cumulative distribution function, the probability density function, the moment generating function, and the moments of the end-to-end signal-to-interference plus noise ratio of these systems in terms of the Meijer\\'s G functions. We then capitalize on these results to offer new exact closed-form expressions for the outage probability, the higher-order amount of fading, and the average error rate for binary and Mary modulation schemes, all in terms of Meijer\\'s G functions. All our new analytical results are verified via computer-based Monte-Carlo simulations and are illustrated by some selected numerical results.
HUBBLE STAYS ON TRAIL OF FADING GAMMA-RAY BURST FIREBALL
2002-01-01
A Hubble Space Telescope image of the fading fireball from one of the universe's most mysterious phenomena, a gamma-ray burst. Though the visible component has faded to 1/500th its brightness (27.7 magnitude) from the time it was first discovered by ground- based telescopes last March (the actual gamma-ray burst took place on February 28), Hubble continues to clearly see the fireball and discriminated a surrounding nebulosity (at 25th magnitude) which is considered a host galaxy. The continued visibility of the burst, and the rate of its fading, support theories that the light from a gamma-ray burst is an expanding relativistic (moving near the speed of light) fireball, possibly produced by the collision of two dense objects, such as an orbiting pair of neutron stars. If the burst happened nearby, within our own galaxy, the resulting fireball should have had only enough energy to propel it into space for a month. The fact that this fireball is still visible after six months means the explosion was truly titanic and, to match the observed brightness, must have happened at the vast distances of galaxies. The energy released in a burst, which can last from a fraction of a second to a few hundred seconds, is equal to all of the Sun's energy generated over its 10 billion year lifetime. The false-color image was taken Sept. 5, 1997 with the Space Telescope Imaging Spectrograph. Credit: Andrew Fruchter (STScI), Elena Pian (ITSRE-CNR), and NASA
Methods and Apparatuses for Signaling with Geometric Constellations in a Raleigh Fading Channel
Barsoum, Maged F. (Inventor); Jones, Christopher R. (Inventor)
2017-01-01
Communication systems are described that use signal constellations, which have unequally spaced (i.e. `geometrically` shaped) points. In many embodiments, the communication systems use specific geometric constellations that are capacity optimized at a specific SNR, over the Raleigh fading channel. In addition, ranges within which the constellation points of a capacity optimized constellation can be perturbed and are still likely to achieve a given percentage of the optimal capacity increase compared to a constellation that maximizes d.sub.min, are also described. Capacity measures that are used in the selection of the location of constellation points include, but are not limited to, parallel decode (PD) capacity and joint capacity.
A novel method for combating dispersion induced power fading in dispersion compensating fiber
DEFF Research Database (Denmark)
Lebedev, Alexander; Vegas Olmos, Juan José; Iglesias Olmedo, Miguel
2013-01-01
We experimentally investigate the performance of 60 GHz double sideband (DSB) radio over fiber (RoF) links that employ dispersion compensating fiber (DCF). Error free transmission of 3 Gbps signals over 1 m of wireless distance is reported. In order to overcome experimentally observed chromatic...... dispersion (CD) induced power fading of radio frequency (RF) signal, we propose a method for improvement of RF carrier-to-noise (C/N) ratio through introduction of a degree of RF frequency tunability. Overall results improve important aspects of directly modulated RoF systems and demonstrate the feasibility...
System Performance of Concatenated STBC and Block Turbo Codes in Dispersive Fading Channels
Directory of Open Access Journals (Sweden)
Kam Tai Chan
2005-05-01
Full Text Available A new scheme of concatenating the block turbo code (BTC with the space-time block code (STBC for an OFDM system in dispersive fading channels is investigated in this paper. The good error correcting capability of BTC and the large diversity gain characteristics of STBC can be achieved simultaneously. The resulting receiver outperforms the iterative convolutional Turbo receiver with maximum- a-posteriori-probability expectation maximization (MAP-EM algorithm. Because of its ability to perform the encoding and decoding processes in parallel, the proposed system is easy to implement in real time.
Directory of Open Access Journals (Sweden)
Biçer Cenker
2016-01-01
Full Text Available In this paper, the stability of the adaptive fading extended Kalman filter with the matrix forgetting factor when applied to the state estimation problem with noise terms in the non–linear discrete–time stochastic systems has been analysed. The analysis is conducted in a similar manner to the standard extended Kalman filter’s stability analysis based on stochastic framework. The theoretical results show that under certain conditions on the initial estimation error and the noise terms, the estimation error remains bounded and the state estimation is stable.
Characterization of ten microsatellite loci in midget faded rattlesnake (Crotalus oreganus concolor)
Oyler-McCance, Sara J.; Parker, Joshua M.
2010-01-01
Primers for 10 microsatellite loci were developed for midget faded rattlesnake (Crotalus oreganus concolor), a small bodied subspecies of the Western Rattlesnake, which is found in the Colorado Plateau of eastern Utah, western Colorado and southwestern Wyoming. In a screen of 23 individuals from the most northern portion of the subspecies range in southwestern Wyoming, the 10 loci were found to have levels of variability ranging from 4 to 11 alleles. No loci were found to be linked, although one locus revealed significant departures from Hardy–Weinberg equilibrium. These microsatellite loci will be applicable for population genetic analyses, which will ultimately aid in management efforts for this rare subspecies of rattlesnake.
Rezki, Zouheir
2014-01-01
We study the throughput capacity region of the Gaussian multi-access (MAC) fading channel with perfect channel state information (CSI) at the receiver and at the transmitters, at low power regime. We show that it has a multidimensional rectangle structure and thus is simply characterized by single user capacity points.More specifically, we show that at low power regime, the boundary surface of the capacity region shrinks to a single point corresponding to the sum rate maximizer and that the coordinates of this point coincide with single user capacity bounds. Inspired from this result, we propose an on-off scheme, compute its achievable rate, and show that this scheme achieves single user capacity bounds of the MAC channel for a wide class of fading channels at asymptotically low power regime. We argue that this class of fading encompasses all known wireless channels for which the capacity region of the MAC channel has even a simpler expression in terms of users\\' average power constraints only. Using the duality of Gaussian MAC and broadcast channels (BC), we deduce a simple characterization of the BC capacity region at low power regime and show that for a class of fading channels (including Rayleigh fading), time-sharing is asymptotically optimal. © 2014 IEEE.
Muir, Kate; Brown, Charity; Madill, Anna
2015-01-01
The intensity of negative emotions associated with event memories fades to a greater extent over time than positive emotions (fading affect bias or FAB). In this study, we examine how the presence and behaviour of a listener during social disclosure influences the FAB and the linguistic characteristics of event narratives. Participants recalled pleasant and unpleasant events and rated each event for its emotional intensity. Recalled events were then allocated to one of three experimental conditions: no disclosure, private verbal disclosure without a listener or social disclosure to another participant whose behaviour was experimentally manipulated. Participants again rated the emotional intensity of the events immediately after these manipulations and after a one-week delay. Verbal disclosure alone was not sufficient to enhance the FAB. However, social disclosure increased positive emotional intensity, regardless of the behaviour of the listener. Whilst talking to an interactive listener led unpleasant event memories to decrease in emotional intensity, talking to a non-responsive listener increased their negative emotional intensity. Further, listener behaviour influenced the extent of emotional expression in written event narratives. This study provides original evidence that listener behaviour during social disclosure is an important factor in the effects of social disclosure in the FAB.
Joint nonbinary low-density parity-check codes and modulation diversity over fading channels
Shi, Zhiping; Li, Tiffany Jing; Zhang, Zhongpei
2010-09-01
A joint exploitation of coding and diversity techniques to achieve efficient, reliable wireless transmission is considered. The system comprises a powerful non-binary low-density parity-check (LDPC) code that will be soft-decoded to supply strong error protection, a quadratic amplitude modulator (QAM) that directly takes in the non-binary LDPC symbols and a modulation diversity operator that will provide power- and bandwidth-efficient diversity gain. By relaxing the rate of the modulation diversity rotation matrices to below 1, we show that a better rate allocation can be arranged between the LDPC codes and the modulation diversity, which brings significant performance gain over previous systems. To facilitate the design and evaluation of the relaxed modulation diversity rotation matrices, based on a set of criteria, three practical design methods are given and their point pairwise error rate are analyzed. With EXIT chart, we investigate the convergence between demodulator and decoder.A rate match method is presented based on EXIT analysis. Through analysis and simulations, we show that our strategies are very effective in combating random fading and strong noise on fading channels.
Discrete Multiwavelet Critical-Sampling Transform-Based OFDM System over Rayleigh Fading Channels
Directory of Open Access Journals (Sweden)
Sameer A. Dawood
2015-01-01
Full Text Available Discrete multiwavelet critical-sampling transform (DMWCST has been proposed instead of fast Fourier transform (FFT in the realization of the orthogonal frequency division multiplexing (OFDM system. The proposed structure further reduces the level of interference and improves the bandwidth efficiency through the elimination of the cyclic prefix due to the good orthogonality and time-frequency localization properties of the multiwavelet transform. The proposed system was simulated using MATLAB to allow various parameters of the system to be varied and tested. The performance of DMWCST-based OFDM (DMWCST-OFDM was compared with that of the discrete wavelet transform-based OFDM (DWT-OFDM and the traditional FFT-based OFDM (FFT-OFDM over flat fading and frequency-selective fading channels. Results obtained indicate that the performance of the proposed DMWCST-OFDM system achieves significant improvement compared to those of DWT-OFDM and FFT-OFDM systems. DMWCST improves the performance of the OFDM system by a factor of 1.5–2.5 dB and 13–15.5 dB compared with the DWT and FFT, respectively. Therefore the proposed system offers higher data rate in wireless mobile communications.
Secure Multiple-Antenna Block-Fading Wiretap Channels with Limited CSI Feedback
Hyadi, Amal
2017-07-18
In this paper, we investigate the ergodic secrecy capacity of a block-fading wiretap channel with limited channel knowledge at the transmitter. We consider that the legitimate receiver, the eavesdropper and the transmitter are equipped with multiple antennas and that the receiving nodes are aware of their respective channel matrices. The transmitter, on the other hand, is only provided by a B-bit feedback of the main channel state information. The feedback bits are sent by the legitimate receiver, at the beginning of each fading block, over an error-free public link with limited capacity. The statistics of the main and the eavesdropper channel state information are known at all nodes. Assuming an average transmit power constraint, we establish upper and lower bounds on the ergodic secrecy capacity. Then, we present a framework to design the optimal codebooks for feedback and transmission. In addition, we show that the proposed lower and upper bounds coincide asymptotically as the capacity of the feedback link becomes large, i.e.
Space-Time Water-Filling for Composite MIMO Fading Channels
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available We analyze the ergodic capacity and channel outage probability for a composite MIMO channel model, which includes both fast fading and shadowing effects. The ergodic capacity and exact channel outage probability with space-time water-filling can be evaluated through numerical integrations, which can be further simplified by using approximated empirical eigenvalue and maximal eigenvalue distribution of MIMO fading channels. We also compare the performance of space-time water-filling with spatial water-filling. For MIMO channels with small shadowing effects, spatial water-filling performs very close to space-time water-filling in terms of ergodic capacity. For MIMO channels with large shadowing effects, however, space-time water-filling achieves significantly higher capacity per antenna than spatial water-filling at low to moderate SNR regimes, but with a much higher channel outage probability. We show that the analytical capacity and outage probability results agree very well with those obtained from Monte Carlo simulations.
Wireless Power Transfer in Cooperative DF Relaying Networks with Log-Normal Fading
Rabie, Khaled M.
2017-02-07
Energy-harvesting (EH) and wireless power transfer in cooperative relaying networks have recently attracted a considerable amount of research attention. Most of the existing work on this topic however focuses on Rayleigh fading channels which represents outdoor environments. Unlike these studies, in this paper we analyze the performance of wireless power transfer in two-hop decode-and- forward (DF) cooperative relaying systems in indoor channels characterized by log-normal fading. Three well-known EH protocols are considered in our evaluations: a) time switching relaying (TSR), b) power splitting relaying (PSR) and c) ideal relaying receiver (IRR). The performance is evaluated in terms of the ergodic outage probability for which we derive accurate analytical expressions for the three systems under consideration. Results reveal that careful selection of the EH time and power splitting factors in the TSR- and PSR-based system are important to optimize performance. It is also presented that the optimized PSR system has near- ideal performance and that increasing the source transmit power and/or the energy harvester efficiency can further improve performance.
Energy-harvesting in cooperative AF relaying networks over log-normal fading channels
Rabie, Khaled M.; Salem, Abdelhamid; Alsusa, Emad; Alouini, Mohamed-Slim
2016-01-01
Energy-harvesting (EH) and wireless power transfer are increasingly becoming a promising source of power in future wireless networks and have recently attracted a considerable amount of research, particularly on cooperative two-hop relay networks in Rayleigh fading channels. In contrast, this paper investigates the performance of wireless power transfer based two-hop cooperative relaying systems in indoor channels characterized by log-normal fading. Specifically, two EH protocols are considered here, namely, time switching relaying (TSR) and power splitting relaying (PSR). Our findings include accurate analytical expressions for the ergodic capacity and ergodic outage probability for the two aforementioned protocols. Monte Carlo simulations are used throughout to confirm the accuracy of our analysis. The results show that increasing the channel variance will always provide better ergodic capacity performance. It is also shown that a good selection of the EH time in the TSR protocol, and the power splitting factor in the PTS protocol, is the key to achieve the best system performance. © 2016 IEEE.
Outage Analysis of Spectrum-Sharing over M-Block Fading with Sensing Information
Alabbasi, Abdulrahman
2016-07-13
Future wireless technologies, such as, 5G, are expected to support real-time applications with high data throughput, e.g., holographic meetings. From a bandwidth perspective, cognitive radio is a promising technology to enhance the system’s throughput via sharing the licensed spectrum. From a delay perspective, it is well known that increasing the number of decoding blocks will improve the system robustness against errors, while increasing the delay. Therefore, optimally allocating the resources to determine the tradeoff of tuning the length of decoding blocks while sharing the spectrum is a critical challenge for future wireless systems. In this work, we minimize the targeted outage probability over the block-fading channels while utilizing the spectrum-sharing concept. The secondary user’s outage region and the corresponding optimal power are derived, over twoblocks and M-blocks fading channels. We propose two suboptimal power strategies and derive the associated asymptotic lower and upper bounds on the outage probability with tractable expressions. These bounds allow us to derive the exact diversity order of the secondary user’s outage probability. To further enhance the system’s performance, we also investigate the impact of including the sensing information on the outage problem. The outage problem is then solved via proposing an alternating optimization algorithm, which utilizes the verified strict quasiconvex structure of the problem. Selected numerical results are presented to characterize the system’s behavior and show the improvements of several sharing concepts.
Energy-harvesting in cooperative AF relaying networks over log-normal fading channels
Rabie, Khaled M.
2016-07-26
Energy-harvesting (EH) and wireless power transfer are increasingly becoming a promising source of power in future wireless networks and have recently attracted a considerable amount of research, particularly on cooperative two-hop relay networks in Rayleigh fading channels. In contrast, this paper investigates the performance of wireless power transfer based two-hop cooperative relaying systems in indoor channels characterized by log-normal fading. Specifically, two EH protocols are considered here, namely, time switching relaying (TSR) and power splitting relaying (PSR). Our findings include accurate analytical expressions for the ergodic capacity and ergodic outage probability for the two aforementioned protocols. Monte Carlo simulations are used throughout to confirm the accuracy of our analysis. The results show that increasing the channel variance will always provide better ergodic capacity performance. It is also shown that a good selection of the EH time in the TSR protocol, and the power splitting factor in the PTS protocol, is the key to achieve the best system performance. © 2016 IEEE.
Relay selection in cooperative communication systems over continuous time-varying fading channel
Directory of Open Access Journals (Sweden)
Ke Geng
2017-02-01
Full Text Available In this paper, we study relay selection under outdated channel state information (CSI in a decode-and-forward (DF cooperative system. Unlike previous researches on cooperative communication under outdated CSI, we consider that the channel varies continuously over time, i.e., the channel not only changes between relay selection and data transmission but also changes during data transmission. Thus the level of accuracy of the CSI used in relay selection degrades with data transmission. We first evaluate the packet error rate (PER of the cooperative system under continuous time-varying fading channel, and find that the PER performance deteriorates more seriously under continuous time-varying fading channel than when the channel is assumed to be constant during data transmission. Then, we propose a repeated relay selection (RRS strategy to improve the PER performance, in which the forwarded data is divided into multiple segments and relay is reselected before the transmission of each segment based on the updated CSI. Finally, we propose a combined relay selection (CRS strategy which takes advantage of three different relay selection strategies to further mitigate the impact of outdated CSI.
Multi-Sensor Optimal Data Fusion Based on the Adaptive Fading Unscented Kalman Filter.
Gao, Bingbing; Hu, Gaoge; Gao, Shesheng; Zhong, Yongmin; Gu, Chengfan
2018-02-06
This paper presents a new optimal data fusion methodology based on the adaptive fading unscented Kalman filter for multi-sensor nonlinear stochastic systems. This methodology has a two-level fusion structure: at the bottom level, an adaptive fading unscented Kalman filter based on the Mahalanobis distance is developed and serves as local filters to improve the adaptability and robustness of local state estimations against process-modeling error; at the top level, an unscented transformation-based multi-sensor optimal data fusion for the case of N local filters is established according to the principle of linear minimum variance to calculate globally optimal state estimation by fusion of local estimations. The proposed methodology effectively refrains from the influence of process-modeling error on the fusion solution, leading to improved adaptability and robustness of data fusion for multi-sensor nonlinear stochastic systems. It also achieves globally optimal fusion results based on the principle of linear minimum variance. Simulation and experimental results demonstrate the efficacy of the proposed methodology for INS/GNSS/CNS (inertial navigation system/global navigation satellite system/celestial navigation system) integrated navigation.
K Coverage Probability of 5G Wireless Cognitive Radio Network under Shadow Fading Effects
Directory of Open Access Journals (Sweden)
Ankur S. Kang
2016-09-01
Full Text Available Land mobile communication is burdened with typical propagation constraints due to the channel characteristics in radio systems.Also,the propagation characteristics vary form place to place and also as the mobile unit moves,from time to time.Hence,the tramsmission path between transmitter and receiver varies from simple direct LOS to the one which is severely obstructed by buildings,foliage and terrain.Multipath propagation and shadow fading effects affect the signal strength of an arbitrary Transmitter-Receiver due to the rapid fluctuations in the phase and amplitude of signal which also determines the average power over an area of tens or hundreds of meters.Shadowing introduces additional fluctuations,so the received local mean power varies around the area –mean.The present section deals with the performance analysis of fifth generation wireless cognitive radio network on the basis of signal and interference level based k coverage probability under the shadow fading effects.
Schädler, Marc René; Warzybok, Anna; Meyer, Bernd T.; Brand, Thomas
2016-01-01
To characterize the individual patient’s hearing impairment as obtained with the matrix sentence recognition test, a simulation Framework for Auditory Discrimination Experiments (FADE) is extended here using the Attenuation and Distortion (A+D) approach by Plomp as a blueprint for setting the individual processing parameters. FADE has been shown to predict the outcome of both speech recognition tests and psychoacoustic experiments based on simulations using an automatic speech recognition system requiring only few assumptions. It builds on the closed-set matrix sentence recognition test which is advantageous for testing individual speech recognition in a way comparable across languages. Individual predictions of speech recognition thresholds in stationary and in fluctuating noise were derived using the audiogram and an estimate of the internal level uncertainty for modeling the individual Plomp curves fitted to the data with the Attenuation (A-) and Distortion (D-) parameters of the Plomp approach. The “typical” audiogram shapes from Bisgaard et al with or without a “typical” level uncertainty and the individual data were used for individual predictions. As a result, the individualization of the level uncertainty was found to be more important than the exact shape of the individual audiogram to accurately model the outcome of the German Matrix test in stationary or fluctuating noise for listeners with hearing impairment. The prediction accuracy of the individualized approach also outperforms the (modified) Speech Intelligibility Index approach which is based on the individual threshold data only. PMID:27604782
Directory of Open Access Journals (Sweden)
Birger Kollmeier
2016-06-01
Full Text Available To characterize the individual patient’s hearing impairment as obtained with the matrix sentence recognition test, a simulation Framework for Auditory Discrimination Experiments (FADE is extended here using the Attenuation and Distortion (A+D approach by Plomp as a blueprint for setting the individual processing parameters. FADE has been shown to predict the outcome of both speech recognition tests and psychoacoustic experiments based on simulations using an automatic speech recognition system requiring only few assumptions. It builds on the closed-set matrix sentence recognition test which is advantageous for testing individual speech recognition in a way comparable across languages. Individual predictions of speech recognition thresholds in stationary and in fluctuating noise were derived using the audiogram and an estimate of the internal level uncertainty for modeling the individual Plomp curves fitted to the data with the Attenuation (A- and Distortion (D- parameters of the Plomp approach. The “typical” audiogram shapes from Bisgaard et al with or without a “typical” level uncertainty and the individual data were used for individual predictions. As a result, the individualization of the level uncertainty was found to be more important than the exact shape of the individual audiogram to accurately model the outcome of the German Matrix test in stationary or fluctuating noise for listeners with hearing impairment. The prediction accuracy of the individualized approach also outperforms the (modified Speech Intelligibility Index approach which is based on the individual threshold data only.
Wireless Power Transfer in Cooperative DF Relaying Networks with Log-Normal Fading
Rabie, Khaled M.; Adebisi, Bamidele; Alouini, Mohamed-Slim
2017-01-01
Energy-harvesting (EH) and wireless power transfer in cooperative relaying networks have recently attracted a considerable amount of research attention. Most of the existing work on this topic however focuses on Rayleigh fading channels which represents outdoor environments. Unlike these studies, in this paper we analyze the performance of wireless power transfer in two-hop decode-and- forward (DF) cooperative relaying systems in indoor channels characterized by log-normal fading. Three well-known EH protocols are considered in our evaluations: a) time switching relaying (TSR), b) power splitting relaying (PSR) and c) ideal relaying receiver (IRR). The performance is evaluated in terms of the ergodic outage probability for which we derive accurate analytical expressions for the three systems under consideration. Results reveal that careful selection of the EH time and power splitting factors in the TSR- and PSR-based system are important to optimize performance. It is also presented that the optimized PSR system has near- ideal performance and that increasing the source transmit power and/or the energy harvester efficiency can further improve performance.
Exact capture probability analysis of GSC receivers over i.n.d. Rayleigh fading channels
Nam, Sungsik
2013-07-01
A closed-form expression of the capture probability of generalized selection combining (GSC) RAKE receivers was introduced in [1]. The idea behind this new performance metric is to quantify how the remaining set of uncombined paths affects the overall performance both in terms of loss in power and increase in interference levels. In this previous work, the assumption was made that the fading is both independent and identically distributed from path to path. However, the average strength of each path is different in reality. In order to derive a closed-form expression of the capture probability over independent and non-identically distributed (i.n.d.) fading channels, we need to derive the joint statistics of ordered non-identical exponential variates. With this motivation in mind, we first provide in this paper some new order statistics results in terms of both moment generating function (MGF) and probability density function (PDF) expressions under an i.n.d. assumption and then derive a new exact closed-form expression for the capture probability GSC RAKE receivers in this more realistic scenario. © 2013 IEEE.
Anomalous fading of the TL, Blue-SL and IR-SL signals of fluorapatite
International Nuclear Information System (INIS)
Tsirliganis, N.; Polymeris, G.; Loukou, Z.; Kitis, G.
2006-01-01
The thermoluminescence (TL), blue stimulated luminescence (BSL) and infrared stimulated luminescence (IRSL) signals of fluorapatite (originating from Durango, Mexico) were measured and found to exhibit strong anomalous fading (AF). The experimentally obtained OSL and IRSL decay curves were transformed into pseudo-linear modulated (pseudo-LM) decay curves. The resulting glow-curve shaped pseudo-LM decay curves were analyzed using a deconvolution analysis, similar to the one used for the glow-curve deconvolution (GCD) of TL glow-curves. It was found that the pseudo-LM OSL and IRSL decay curves consist of two components named fast and slow, respectively, and their individual contribution was estimated. The AF of the remnant TL, BSL and IRSL as a function of the storage time was fitted using the tunneling model equations and the fading rate g, in terms of percentage per decade was evaluated. According to the obtained g values, the AF of the BSL and IRSL is stronger than that of the TL. The AF of the fast component of BSL and IRSL is almost the same. The AF of the slow component of IRSL is, by approximately a factor of 2, stronger than that of the BSL
Shakir, Muhammad
2014-06-01
Heterogeneous networks (HetNets) are envisioned to enable next-generation cellular networks by providing higher spectral and energy efficiency. A HetNet is typically composed of multiple radio access technologies where several low-power low-cost operators or user-deployed small-cell base stations (SBSs) complement the macrocell network. In this paper, we consider a two-tier HetNet where the SBSs are arranged around the edge of the reference macrocell such that the resultant configuration is referred to as cell-on-edge (COE). Each mobile user in a small cell is considered capable of adapting its uplink transmit power according to a location-based slow power control mechanism. The COE configuration is observed to increase the uplink area spectral efficiency (ASE) and energy efficiency while reducing the cochannel interference power. A moment-generating-function (MGF)-based approach has been exploited to derive the analytical bounds on the uplink ASE of the COE configuration. The derived expressions are generalized for any composite fading distribution, and closed-form expressions are presented for the generalized- K fading channels. Simulation results are included to support the analysis and to show the efficacy of the COE configuration. A comparative performance analysis is also provided to demonstrate the improvements in the performance of cell-edge users of the COE configuration compared with that of macro-only networks (MoNets) and other unplanned deployment strategies. © 2013 IEEE.
Large-Scale Fading and Time Dispersion Parameters of UWB Channel in Underground Mines
Directory of Open Access Journals (Sweden)
Abdellah Chehri
2008-01-01
Full Text Available RF channel measurements in underground mines have important applications in the field of mobile communications for improving operational efficiency and worker safety. This paper presents an experimental study of the ultra wideband (UWB radio channel, based on extensive sounding campaigns covering the underground mine environment. Measurements were carried out in the frequency band of 2–5 GHz. Various communication links were considered including both line-of-sight (LOS and non-LOS (NLOS scenarios. In this paper, we are interested in more details of the variations of the RMS delay spread and mean excess delay with Tx/Rx separation, and the variation of RMS with mean excess. The distance dependency of path loss and shadowing fading statistics is also investigated. To give an idea about the behaviour of UWB channel in underground mines, a comparison of our approach with other published works is given including path loss exponent, shadow fading variance, mean excess delay, and RMS delay spread.
Secure Multiple-Antenna Block-Fading Wiretap Channels with Limited CSI Feedback
Hyadi, Amal; Rezki, Zouheir; Alouini, Mohamed-Slim
2017-01-01
In this paper, we investigate the ergodic secrecy capacity of a block-fading wiretap channel with limited channel knowledge at the transmitter. We consider that the legitimate receiver, the eavesdropper and the transmitter are equipped with multiple antennas and that the receiving nodes are aware of their respective channel matrices. The transmitter, on the other hand, is only provided by a B-bit feedback of the main channel state information. The feedback bits are sent by the legitimate receiver, at the beginning of each fading block, over an error-free public link with limited capacity. The statistics of the main and the eavesdropper channel state information are known at all nodes. Assuming an average transmit power constraint, we establish upper and lower bounds on the ergodic secrecy capacity. Then, we present a framework to design the optimal codebooks for feedback and transmission. In addition, we show that the proposed lower and upper bounds coincide asymptotically as the capacity of the feedback link becomes large, i.e.
Maximizing Expected Achievable Rates for Block-Fading Buffer-Aided Relay Channels
Shaqfeh, Mohammad
2016-05-25
In this paper, the long-term average achievable rate over block-fading buffer-aided relay channels is maximized using a hybrid scheme that combines three essential transmission strategies, which are decode-and-forward, compress-and-forward, and direct transmission. The proposed hybrid scheme is dynamically adapted based on the channel state information. The integration and optimization of these three strategies provide a more generic and fundamental solution and give better achievable rates than the known schemes in the literature. Despite the large number of optimization variables, the proposed hybrid scheme can be optimized using simple closed-form formulas that are easy to apply in practical relay systems. This includes adjusting the transmission rate and compression when compress-and-forward is the selected strategy based on the channel conditions. Furthermore, in this paper, the hybrid scheme is applied to three different models of the Gaussian block-fading buffer-aided relay channels, depending on whether the relay is half or full duplex and whether the source and the relay have orthogonal or non-orthogonal channel access. Several numerical examples are provided to demonstrate the achievable rate results and compare them to the upper bounds of the ergodic capacity for each one of the three channel models under consideration.
On the Secrecy Capacity Region of the Block-Fading BCC with Limited CSI Feedback
Hyadi, Amal
2017-02-07
In this work, we examine the secrecy capacity region of the block-fading broadcast channel with confidential messages (BCC) when the transmitter has limited knowledge of the channel. In particular, we consider a two-user communication system where the transmitter has one common message to be transmitted to both users and one confidential message intended to only one of them. The confidential message has to be kept secret from the other user to whom the information is not intended. The transmitter is not aware of the channel state information (CSI) of neither channel and is only provided by limited CSI feedback sent at the beginning of each fading block. Assuming an error-free feedback link, we characterize the secrecy capacity region of this channel and show that even with a 1-bit CSI feedback, a positive secrecy rate can still be achieved. Then, we look at the case where the feedback link is not error- free and is rather a binary erasure channel (BEC). In the latter case, we provide an achievable secrecy rate region and show that as long as the erasure event is not a probability 1 event, the transmitter can still transmit the confidential information with a positive secrecy rate.
Maximizing Expected Achievable Rates for Block-Fading Buffer-Aided Relay Channels
Shaqfeh, Mohammad; Zafar, Ammar; Alnuweiri, Hussein; Alouini, Mohamed-Slim
2016-01-01
In this paper, the long-term average achievable rate over block-fading buffer-aided relay channels is maximized using a hybrid scheme that combines three essential transmission strategies, which are decode-and-forward, compress-and-forward, and direct transmission. The proposed hybrid scheme is dynamically adapted based on the channel state information. The integration and optimization of these three strategies provide a more generic and fundamental solution and give better achievable rates than the known schemes in the literature. Despite the large number of optimization variables, the proposed hybrid scheme can be optimized using simple closed-form formulas that are easy to apply in practical relay systems. This includes adjusting the transmission rate and compression when compress-and-forward is the selected strategy based on the channel conditions. Furthermore, in this paper, the hybrid scheme is applied to three different models of the Gaussian block-fading buffer-aided relay channels, depending on whether the relay is half or full duplex and whether the source and the relay have orthogonal or non-orthogonal channel access. Several numerical examples are provided to demonstrate the achievable rate results and compare them to the upper bounds of the ergodic capacity for each one of the three channel models under consideration.
Performance analysis of adaptive modulation for cognitive radios with opportunistic access
Chen, Yunfei; Alouini, Mohamed-Slim; Tang, Liang
2011-01-01
The performance of adaptive modulation for cognitive radio with opportunistic access is analyzed by considering the effects of spectrum sensing and primary user traffic for Nakagami-m fading channels. Both the adaptive continuous rate scheme
Benkhelifa, Fatma
2013-04-01
In this letter, we study the ergodic capacity of a maximum ratio combining (MRC) Rician fading channel with full channel state information (CSI) at the transmitter and at the receiver. We focus on the low Signal-to-Noise Ratio (SNR) regime and we show that the capacity scales as L ΩK+L SNRx log(1SNR), where Ω is the expected channel gain per branch, K is the Rician fading factor, and L is the number of diversity branches. We show that one-bit CSI feedback at the transmitter is enough to achieve this capacity using an on-off power control scheme. Our framework can be seen as a generalization of recently established results regarding the fading-channels capacity characterization in the low-SNR regime. © 2012 IEEE.
Benkhelifa, Fatma; Rezki, Zouheir; Alouini, Mohamed-Slim
2013-01-01
In this letter, we study the ergodic capacity of a maximum ratio combining (MRC) Rician fading channel with full channel state information (CSI) at the transmitter and at the receiver. We focus on the low Signal-to-Noise Ratio (SNR) regime and we show that the capacity scales as L ΩK+L SNRx log(1SNR), where Ω is the expected channel gain per branch, K is the Rician fading factor, and L is the number of diversity branches. We show that one-bit CSI feedback at the transmitter is enough to achieve this capacity using an on-off power control scheme. Our framework can be seen as a generalization of recently established results regarding the fading-channels capacity characterization in the low-SNR regime. © 2012 IEEE.
Reinhart, Richard C.
1993-01-01
The Power Control and Rain Fade Software was developed at the NASA Lewis Research Center to support the Advanced Communications Technology Satellite High Burst Rate Link Evaluation Terminal (ACTS HBR-LET). The HBR-LET is an experimenters terminal to communicate with the ACTS for various experiments by government, university, and industry agencies. The Power Control and Rain Fade Software is one segment of the Control and Performance Monitor (C&PM) Software system of the HBR-LET. The Power Control and Rain Fade Software automatically controls the LET uplink power to compensate for signal fades. Besides power augmentation, the C&PM Software system is also responsible for instrument control during HBR-LET experiments, control of the Intermediate Frequency Switch Matrix on board the ACTS to yield a desired path through the spacecraft payload, and data display. The Power Control and Rain Fade Software User's Guide, Version 1.0 outlines the commands and procedures to install and operate the Power Control and Rain Fade Software. The Power Control and Rain Fade Software Maintenance Manual, Version 1.0 is a programmer's guide to the Power Control and Rain Fade Software. This manual details the current implementation of the software from a technical perspective. Included is an overview of the Power Control and Rain Fade Software, computer algorithms, format representations, and computer hardware configuration. The Power Control and Rain Fade Test Plan provides a step-by-step procedure to verify the operation of the software using a predetermined signal fade event. The Test Plan also provides a means to demonstrate the capability of the software.
Al-Badarneh, Yazan Hussein
2018-01-25
We consider a general selection-diversity (SD) scheme in which the k-th best link is selected from a number of links. We use extreme value theory (EVT) to derive simple closed-form asymptotic expressions for the average throughput, effective throughput and average bit error probability (BEP) for the k-th best link over various channel models that are widely used to characterize fading in wireless communication systems. As an application example, we consider the Weibull fading channel model and verify the accuracy of the derived asymptotic expressions through Monte Carlo simulations.
DEFF Research Database (Denmark)
Yanes, Oscar; Aviles, Francesc X; Roepstorff, Peter
2007-01-01
the intensity fading phenomenon, as well as a comparison with the strategy based on the direct detection of intact complexes by MALDI MS. For this purpose, the study is focused on two different protease-inhibitor complexes naturally occurring in solution, together with a heterogeneous mixture of nonbinding...... molecules derived from a biological extract, to examine the specificity of the approach, i.e., those of carboxypeptidase A (CPA) bound to potato carboxypeptidase inhibitor (PCI) and of trypsin bound to bovine pancreatic trypsin inhibitor (BPTI). Our results show that the intensity fading phenomenon occurs...
Yilmaz, Ferkan
2010-09-01
In this paper, we propose an analytical framework on the exact computation of the average symbol error probabilities (ASEP) of multihop transmission over generalized fading channels when an arbitrary number of amplify-and-forward relays is used. Our approach relies on moment generating function (MGF) framework to obtain exact single integral expressions which can be easily computed by Gauss-Chebyshev Quadrature (GCQ) rule. As such, the derived results are a convenient tool to analyze the ASEP performance of multihop transmission over amplify-and-forward relay fading channels. Numerical and simulation results, performed to verify the correctness of the proposed formulation, are in perfect agreement. © 2010 IEEE.
Yilmaz, Ferkan; Kucur, Oǧuz; Alouini, Mohamed-Slim
2010-01-01
In this paper, we propose an analytical framework on the exact computation of the average symbol error probabilities (ASEP) of multihop transmission over generalized fading channels when an arbitrary number of amplify-and-forward relays is used. Our approach relies on moment generating function (MGF) framework to obtain exact single integral expressions which can be easily computed by Gauss-Chebyshev Quadrature (GCQ) rule. As such, the derived results are a convenient tool to analyze the ASEP performance of multihop transmission over amplify-and-forward relay fading channels. Numerical and simulation results, performed to verify the correctness of the proposed formulation, are in perfect agreement. © 2010 IEEE.
Soury, Hamza
2015-01-07
This work considers the symbol error rate of M-ary phase shift keying (MPSK) constellations over extended Generalized-K fading with Laplacian noise and using a minimum distance detector. A generic closed form expression of the conditional and the average probability of error is obtained and simplified in terms of the Fox’s H function. More simplifications to well known functions for some special cases of fading are also presented. Finally, the mathematical formalism is validated with some numerical results examples done by computer based simulations [1].
Soury, Hamza
2014-06-01
This paper considers the symbol error rate of M-ary phase shift keying (MPSK) constellations over extended Generalized-K fading with Laplacian noise and using a minimum distance detector. A generic closed form expression of the conditional and the average probability of error is obtained and simplified in terms of the Fox\\'s H function. More simplifications to well known functions for some special cases of fading are also presented. Finally, the mathematical formalism is validated with some numerical results examples done by computer based simulations. © 2014 IEEE.
Al-Badarneh, Yazan Hussein; Georghiades, Costas; Alouini, Mohamed-Slim
2018-01-01
We consider a general selection-diversity (SD) scheme in which the k-th best link is selected from a number of links. We use extreme value theory (EVT) to derive simple closed-form asymptotic expressions for the average throughput, effective throughput and average bit error probability (BEP) for the k-th best link over various channel models that are widely used to characterize fading in wireless communication systems. As an application example, we consider the Weibull fading channel model and verify the accuracy of the derived asymptotic expressions through Monte Carlo simulations.
Soury, Hamza; Alouini, Mohamed-Slim
2014-01-01
This paper considers the symbol error rate of M-ary phase shift keying (MPSK) constellations over extended Generalized-K fading with Laplacian noise and using a minimum distance detector. A generic closed form expression of the conditional and the average probability of error is obtained and simplified in terms of the Fox's H function. More simplifications to well known functions for some special cases of fading are also presented. Finally, the mathematical formalism is validated with some numerical results examples done by computer based simulations. © 2014 IEEE.
Soury, Hamza; Alouini, Mohamed-Slim
2015-01-01
This work considers the symbol error rate of M-ary phase shift keying (MPSK) constellations over extended Generalized-K fading with Laplacian noise and using a minimum distance detector. A generic closed form expression of the conditional and the average probability of error is obtained and simplified in terms of the Fox’s H function. More simplifications to well known functions for some special cases of fading are also presented. Finally, the mathematical formalism is validated with some numerical results examples done by computer based simulations [1].
The effect of correlated observations on the performance of distributed estimation
Ahmed, Mohammed
2013-12-01
Estimating unknown signal in Wireless Sensor Networks (WSNs) requires sensor nodes to transmit their observations of the signal over a multiple access channel to a Fusion Center (FC). The FC uses the received observations, which is corrupted by observation noise and both channel fading and noise, to find the minimum Mean Square Error (MSE) estimate of the signal. In this paper, we investigate the effect of the source-node correlation (the correlation between sensor node observations and the source signal) and the inter-node correlation (the correlation between sensor node observations) on the performance of the Linear Minimum Mean Square Error (LMMSE) estimator for three correlation models in the presence of channel fading. First, we investigate the asymptotic behavior of the achieved distortion (i.e., MSE) resulting from both the observation and channel noise in a non-fading channel. Then, the effect of channel fading is considered and the corresponding distortion outage probability, the probability that the distortion exceeds a certain value, is found. By representing the distortion as a ratio of indefinite quadratic forms, a closed-form expression is derived for the outage probability that shows its dependency on the correlation. Finally, the new representation of the outage probability allows us to propose an iterative solution for the power allocation problem to minimize the outage probability under total and individual power constraints. Numerical simulations are provided to verify our analytic results. © 2013 IEEE.
Upper Bounds on the BER Performance of MTCM-STBC Schemes over Shadowed Rician Fading Channels
Directory of Open Access Journals (Sweden)
M. Uysal
2004-08-01
Full Text Available Space-time block coding (STBC provides substantial diversity advantages with a low decoding complexity. However, these codes are not designed to achieve coding gains. Outer codes should be concatenated with STBC to provide additional coding gain. In this paper, we analyze the performance of concatenated trellis-coded STBC schemes over shadowed Rician frequency-flat fading channels. We derive an exact pairwise error probability (PEP expression that reveals the dominant factors affecting performance. Based on the derived PEP, in conjunction with the transfer function technique, we also present upper bounds on the bit error rate (BER, which are further shown to be tight through a Monte-Carlo simulation study.
Directory of Open Access Journals (Sweden)
Dejan Jaksic
2017-01-01
Full Text Available Mathematical modelling of the behavior of the radio propagation at mmWave bands is crucial to the development of transmission and reception algorithms of new 5G systems. In this study we will model 5G propagation in nondeterministic line-of-sight (LOS conditions, when the random nature of LOS component ratio will be observed as Inverse Gamma (IG distributed process. Closed-form expressions will be presented for the probability density function (PDF and cumulative distribution function (CDF of such random process. Further, closed-form expressions will be provided for important performance measures such as level crossing rate (LCR and average fade duration (AFD. Capitalizing on proposed expressions, LCR and AFD will be discussed in the function of transmission parameters.
A novel reduced-complexity group detection structure in MIMO frequency selective fading channels
Qaraqe, Khalid A.; Ahimian, Nariman R.; Alouini, Mohamed-Slim
2010-01-01
In this paper a novel reduced complexity detection method named modified symbol flipping method is introduced and its advantages on reducing the burden of the calculations at the receiver compared to the optimum maximum likelihood detection method on multiple input- multiple output frequency selective fading channels are explained. The initial concept of the symbol flipping method is derived from a preliminary detection scheme named bit flipping which was introduced in [1]. The detection structure employed in this paper is ing, detection, and cancellation. On the detection stage, the proposed method is employed and the results are compared to the group maximum likelihood detection scheme proposed in [2]. Simulation results show that a 6 dB performance gain can be achieved at the expense of a slight increase in complexity in comparison with the conventional symbol flipping scheme. © 2010 Crown.
GPS Multipath Fade Measurements to Determine L-Band Ground Reflectivity Properties
Kavak, Adnan; Xu, Guang-Han; Vogel, Wolfhard J.
1996-01-01
In personal satellite communications, especially when the line-of-sight is clear, ground specular reflected signals along with direct signals are received by low gain, almost omni-directional subscriber antennas. A six-channel, C/A code processing, GPS receiver with an almost omni-directional patch antenna was used to take measurements over three types of ground to characterize 1.575 GHz specular ground reflections and ground dielectric properties. Fade measurements were taken over grass, asphalt, and lake water surfaces by placing the antenna in a vertical position at a fixed height from the ground. Electrical characteristics (conductivity and dielectric constant) of these surfaces (grass, asphalt, lake water) were obtained by matching computer simulations to the experimental results.
A Novel Simulator of Nonstationary Random MIMO Channels in Rayleigh Fading Scenarios
Directory of Open Access Journals (Sweden)
Qiuming Zhu
2016-01-01
Full Text Available For simulations of nonstationary multiple-input multiple-output (MIMO Rayleigh fading channels in time-variant scattering environments, a novel channel simulator is proposed based on the superposition of chirp signals. This new method has the advantages of low complexity and implementation simplicity as the sum of sinusoids (SOS method. In order to reproduce realistic time varying statistics for dynamic channels, an efficient parameter computation method is also proposed for updating the frequency parameters of employed chirp signals. Simulation results indicate that the proposed simulator is effective in generating nonstationary MIMO channels with close approximation of the time-variant statistical characteristics in accordance with the expected theoretical counterparts.
Advanced Fade Countermeasures for DVB-S2 Systems in Railway Scenarios
Directory of Open Access Journals (Sweden)
Niebla CristinaPárraga
2007-01-01
Full Text Available This paper deals with the analysis of advanced fade countermeasures for supporting DVB-S2 reception by mobile terminals mounted on high-speed trains. Recent market studies indicate this as a potential profitable market for satellite communications, provided that integration with wireless terrestrial networks can be implemented to bridge the satellite connectivity inside railway tunnels and large train stations. In turn, the satellite can typically offer the coverage of around 80% of the railway path with existing space infrastructure. This piece of work, representing the first step of a wider study, is focusing on the modifications which may be required in the DVB-S2 standard (to be employed in the forward link in order to achieve reliable reception in a challenging environment such as the railway one. Modifications have been devised trying to minimize the impact on the existing air interface, standardized for fixed terminals.
Advanced Fade Countermeasures for DVB-S2 Systems in Railway Scenarios
Directory of Open Access Journals (Sweden)
Cristina Párraga Niebla
2007-07-01
Full Text Available This paper deals with the analysis of advanced fade countermeasures for supporting DVB-S2 reception by mobile terminals mounted on high-speed trains. Recent market studies indicate this as a potential profitable market for satellite communications, provided that integration with wireless terrestrial networks can be implemented to bridge the satellite connectivity inside railway tunnels and large train stations. In turn, the satellite can typically offer the coverage of around 80% of the railway path with existing space infrastructure. This piece of work, representing the first step of a wider study, is focusing on the modifications which may be required in the DVB-S2 standard (to be employed in the forward link in order to achieve reliable reception in a challenging environment such as the railway one. Modifications have been devised trying to minimize the impact on the existing air interface, standardized for fixed terminals.
A novel reduced-complexity group detection structure in MIMO frequency selective fading channels
Qaraqe, Khalid A.
2010-09-01
In this paper a novel reduced complexity detection method named modified symbol flipping method is introduced and its advantages on reducing the burden of the calculations at the receiver compared to the optimum maximum likelihood detection method on multiple input- multiple output frequency selective fading channels are explained. The initial concept of the symbol flipping method is derived from a preliminary detection scheme named bit flipping which was introduced in [1]. The detection structure employed in this paper is ing, detection, and cancellation. On the detection stage, the proposed method is employed and the results are compared to the group maximum likelihood detection scheme proposed in [2]. Simulation results show that a 6 dB performance gain can be achieved at the expense of a slight increase in complexity in comparison with the conventional symbol flipping scheme. © 2010 Crown.
A study of optimization problem for amplify-and-forward relaying over weibull fading channels
Ikki, Salama Said
2010-09-01
This paper addresses the power allocation and relay positioning problems in amplify-and-forward cooperative networks operating in Weibull fading environments. We study adaptive power allocation (PA) with fixed relay location, optimal relay location with fixed power allocation, and joint optimization of the PA and relay location under total transmit power constraint, in order to minimize the outage probability and average error probability at high signal-to-noise ratios (SNR). Analytical results are validated by numerical simulations and comparisons between the different optimization schemes and their performance are provided. Results show that optimum PA brings only coding gain, while optimum relay location yields, in addition to the latter, diversity gains as well. Also, joint optimization improves both, the diversity gain and coding gain. Furthermore, results illustrate that the analyzed adaptive algorithms outperform uniform schemes. ©2010 IEEE.
Performance of equal gain combining with quantized phases in rayleigh fading channels
Rizvi, Umar H.
2011-01-01
In this paper, we analyze the error probability of equal gain combining with quantized channel phase compensation for binary phase shift keying signalling over Rayleigh fading channels. The probability density and characteristic functions of the combined signal amplitude are derived and used to compute the analytic expressions for the bit error probability in dependance of the number of quantization levels L, the number of diversity branches N-R and the average received signal-to-noise ratio. The analysis is utilized to outline the trade-off between N-R and L and to compare the performance with non-coherent binary frequency shift keying and differential binary phase shift keying schemes under diversity reception. © 2011 IEEE.
Directory of Open Access Journals (Sweden)
Wenjie Peng
2014-01-01
Full Text Available The exact closed-form expressions regarding the outage probability and capacity of distributed MIMO (DMIMO systems over a composite fading channel are derived. This is achieved firstly by using a lognormal approximation to a gamma-lognormal distribution when a mobile station (MS in the cell is in a fixed position, and the so-called maximum ratio transmission/selected combining (MRT-SC and selected transmission/maximum ratio combining (ST-MRC schemes are adopted in uplink and downlink, respectively. Then, based on a newly proposed nonuniform MS cell distribution model, which is more consistent with the MS cell hotspot distribution in an actual communication environment, the average outage probability and capacity formulas are further derived. Finally, the accuracy of the approximation method and the rationality of the corresponding theoretical analysis regarding the system performance are proven and illustrated by computer simulations.
An information-guided channel-hopping scheme for block-fading channels with estimation errors
Yang, Yuli
2010-12-01
Information-guided channel-hopping technique employing multiple transmit antennas was previously proposed for supporting high data rate transmission over fading channels. This scheme achieves higher data rates than some mature schemes, such as the well-known cyclic transmit antenna selection and space-time block coding, by exploiting the independence character of multiple channels, which effectively results in having an additional information transmitting channel. Moreover, maximum likelihood decoding may be performed by simply decoupling the signals conveyed by the different mapping methods. In this paper, we investigate the achievable spectral efficiency of this scheme in the case of having channel estimation errors, with optimum pilot overhead for minimum meansquare error channel estimation, when transmitting over blockfading channels. Our numerical results further substantiate the robustness of the presented scheme, even with imperfect channel state information. ©2010 IEEE.
Institute of Scientific and Technical Information of China (English)
YUAN Dongfeng; WANG Chengxiang; YAO Qi; CAO Zhigang
2001-01-01
Based on "capacity rule", the perfor-mance of multilevel coding (MLC) schemes with dif-ferent set partitioning strategies and decoding meth-ods in AWGN and Rayleigh fading channels is investi-gated, in which BCH codes are chosen as componentcodes and 8ASK modulation is used. Numerical re-sults indicate that MLC scheme with UP strategy canobtain optimal performance in AWGN channels andBP is the best mapping strategy for Rayleigh fadingchannels. BP strategy is of good robustness in bothkinds of channels to realize an optimum MLC system.Multistage decoding (MSD) is a sub-optimal decodingmethod of MLC for both channels. For Ungerboeckpartitioning (UP) and mixed partitioning (MP) strat-egy, MSD is strongly recommended to use for MLCsystem, while for BP strategy, PDL is suggested to useas a simple decoding method compared with MSD.
Compassion fade: affect and charity are greatest for a single child in need.
Directory of Open Access Journals (Sweden)
Daniel Västfjäll
Full Text Available Charitable giving in 2013 exceeded $300 billion, but why do we respond to some life-saving causes while ignoring others? In our first two studies, we demonstrated that valuation of lives is associated with affective feelings (self-reported and psychophysiological and that a decline in compassion may begin with the second endangered life. In Study 3, this fading of compassion was reversed by describing multiple lives in a more unitary fashion. Study 4 extended our findings to loss-frame scenarios. Our capacity to feel sympathy for people in need appears limited, and this form of compassion fatigue can lead to apathy and inaction, consistent with what is seen repeatedly in response to many large-scale human and environmental catastrophes.
X-Ray Brightening and UV Fading of Tidal Disruption Event ASASSN-15oi
Gezari, S.; Cenko, S. B.; Arcavi, I.
2017-12-01
We present late-time observations by Swift and XMM-Newton of the tidal disruption event (TDE) ASASSN-15oi that reveal that the source brightened in the X-rays by a factor of ∼10 one year after its discovery, while it faded in the UV/optical by a factor of ∼100. The XMM-Newton observations measure a soft X-ray blackbody component with {{kT}}{bb}∼ 45 {eV}, corresponding to radiation from several gravitational radii of a central ∼ {10}6 {M}ȯ black hole. The last Swift epoch taken almost 600 days after discovery shows that the X-ray source has faded back to its levels during the UV/optical peak. The timescale of the X-ray brightening suggests that the X-ray emission could be coming from delayed accretion through a newly forming debris disk and that the prompt UV/optical emission is from the prior circularization of the disk through stream–stream collisions. The lack of spectral evolution during the X-ray brightening disfavors ionization breakout of a TDE “veiled” by obscuring material. This is the first time a TDE has been shown to have a delayed peak in soft X-rays relative to the UV/optical peak, which may be the first clear signature of the real-time assembly of a nascent accretion disk, and provides strong evidence for the origin of the UV/optical emission from circularization, as opposed to reprocessed emission of accretion radiation.
Throughput and Delay Analysis of HARQ with Code Combining over Double Rayleigh Fading Channels
Chelli, Ali
2018-01-15
This paper proposes the use of hybrid automatic repeat request (HARQ) with code combining (HARQ-CC) to offer reliable communications over double Rayleigh channels. The double Rayleigh fading channel is of particular interest to vehicle-to-vehicle communication systems as well as amplify-and-forward relaying and keyhole channels. This work studies the performance of HARQ-CC over double Rayleigh channels from an information theoretic perspective. Analytical approximations are derived for the
X-RAY FADING AND EXPANSION IN THE “MINIATURE SUPERNOVA REMNANT” OF GK PERSEI
Energy Technology Data Exchange (ETDEWEB)
Takei, D. [Institute of Physical and Chemical Research (RIKEN), RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148 (Japan); Drake, J. J.; Slane, P. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Yamaguchi, H. [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States); Uchiyama, Y. [Department of Physics, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501 (Japan); Katsuda, S., E-mail: takei@spring8.or.jp [Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, 3-1-1 Yoshino-dai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
2015-03-10
We report on a second epoch of Chandra X-ray imaging spectroscopy of the spatially resolved old nova remnant GK Persei. An ACIS-S3 observation of 97.4 ks was conducted in 2013 November after a lapse of 13.8 yr from the last visit in 2000. The X-ray emitting nebula appeared more faint and patchy compared with the first epoch. The flux decline was particularly evident in fainter regions and the mean decline was 30%–40% in the 0.5–1.2 keV energy band. A typical expansion of the brightest part of the remnant was 1.″9, which corresponds to an expansion rate of 0.″14 yr{sup −1}. The soft X-ray spectra extracted from both the 2000 and 2013 data can be explained by a non-equilibrium ionization collisional plasma model convolved with interstellar absorption, though do not allow us to constrain the origin of the flux evolution. The plasma temperature has not significantly evolved since the 2000 epoch and we conclude that the fading of the X-ray emission is due largely to expansion. This implies that recent expansion has been into a lower density medium, a scenario that is qualitatively consistent with the structure of the circumstellar environment photographed soon after the initial explosion more than a century ago. Fainter areas are fading more quickly than brighter areas, indicating that they are fainter because of a lower ambient medium density and consequently more rapid expansion.
ASEP of MIMO System with MMSE-OSIC Detection over Weibull-Gamma Fading Channel Subject to AWGGN
Directory of Open Access Journals (Sweden)
Keerti Tiwari
2016-01-01
Full Text Available Ordered successive interference cancellation (OSIC is adopted with minimum mean square error (MMSE detection to enhance the multiple-input multiple-output (MIMO system performance. The optimum detection technique improves the error rate performance but increases system complexity. Therefore, MMSE-OSIC detection is used which reduces error rate compared to traditional MMSE with low complexity. The system performance is analyzed in composite fading environment that includes multipath and shadowing effects known as Weibull-Gamma (WG fading. Along with the composite fading, a generalized noise that is additive white generalized Gaussian noise (AWGGN is considered to show the impact of wireless scenario. This noise model includes various forms of noise as special cases such as impulsive, Gamma, Laplacian, Gaussian, and uniform. Consequently, generalized Q-function is used to model noise. The average symbol error probability (ASEP of MIMO system is computed for 16-quadrature amplitude modulation (16-QAM using MMSE-OSIC detection in WG fading perturbed by AWGGN. Analytical expressions are given in terms of Fox-H function (FHF. These expressions demonstrate the best fit to simulation results.
Fleeting, fading, or far-reaching? A knowledge-based model of the persistence of framing effects
Baden, C.; Lecheler, S.
2012-01-01
The social relevance of framing effects hinges upon their ability to persist. This article develops a theoretical account of the conditions under which framing effects should vanish quickly, fade slowly, or cause permanent changes. It argues that the cognitive processes involved in mediating frame
Sheng, Li; Wang, Zidong; Tian, Engang; Alsaadi, Fuad E
2016-12-01
This paper deals with the H ∞ state estimation problem for a class of discrete-time neural networks with stochastic delays subject to state- and disturbance-dependent noises (also called (x,v)-dependent noises) and fading channels. The time-varying stochastic delay takes values on certain intervals with known probability distributions. The system measurement is transmitted through fading channels described by the Rice fading model. The aim of the addressed problem is to design a state estimator such that the estimation performance is guaranteed in the mean-square sense against admissible stochastic time-delays, stochastic noises as well as stochastic fading signals. By employing the stochastic analysis approach combined with the Kronecker product, several delay-distribution-dependent conditions are derived to ensure that the error dynamics of the neuron states is stochastically stable with prescribed H ∞ performance. Finally, a numerical example is provided to illustrate the effectiveness of the obtained results. Copyright © 2016 Elsevier Ltd. All rights reserved.
Yilmaz, Ferkan
2012-06-01
Ergodic capacity is an important performance measure associated with reliable communication at the highest rate at which information can be sent over the channel with a negligible probability of error. In the shadow of this definition, diversity receivers (such as selection combining, equal-gain combining and maximal-ratio combining) and transmission techniques (such as cascaded fading channels, amplify-and-forward multihop transmission) are deployed in mitigating various performance impairing effects such as fading and shadowing in digital radio communication links. However, the exact analysis of ergodic capacity is in general not always possible for all of these forms of diversity receivers and transmission techniques over generalized composite fading environments due to it\\'s mathematical intractability. In the literature, published papers concerning the exact analysis of ergodic capacity have been therefore scarce (i.e., only [1] and [2]) when compared to those concerning the exact analysis of average symbol error probability. In addition, they are essentially targeting to the ergodic capacity of the maximal ratio combining diversity receivers and are not readily applicable to the capacity analysis of the other diversity combiners / transmission techniques. In this paper, we propose a novel moment generating function-based approach for the exact ergodic capacity analysis of both diversity receivers and transmission techniques over generalized composite fading environments. As such, we demonstrate how to simultaneously treat the ergodic capacity analysis of all forms of both diversity receivers and multihop transmission techniques. © 2012 IEEE.
Directory of Open Access Journals (Sweden)
Hongjun Xu
2011-07-01
Full Text Available A channel and delay estimation algorithm for both positive and negative delay, based on the distributed Alamouti scheme, has been recently discussed for base-station–based asynchronous cooperative systems in frequency-flat fading channels. This paper extends the algorithm, the maximum likelihood estimator, to work in frequency-selective fading channels. The minimum mean square error (MMSE performance of channel estimation for both packet schemes and normal schemes is discussed in this paper. The symbol error rate (SER performance of equalisation and detection for both time-reversal space-time block code (STBC and single-carrier STBC is also discussed in this paper. The MMSE simulation results demonstrated the superior performance of the packet scheme over the normal scheme with an improvement in performance of up to 6 dB when feedback was used in the frequency-selective channel at a MSE of 3 x 10^{–2}. The SER simulation results showed that, although both the normal and packet schemes achieved similar diversity orders, the packet scheme demonstrated a 1 dB coding gain over the normal scheme at a SER of 10^{–5}. Finally, the SER simulations showed that the frequency-selective fading system outperformed the frequency-flat fading system.
Fading of the Tl signal in LiF: Mg, Cu, P during a large post irradiation period
International Nuclear Information System (INIS)
Gonzalez, P.R.; Azorin, J.; Furetta, C.
2004-01-01
In this work the obtained results of the study of the fading of the Tl signal in dosemeters of LiF activated with magnesium, copper and phosphorus (LiF:Mg,Cu,P) are presented. The studied dosemeters were LiF: Mg,Cu,P + Ptfe, developed in the ININ, taking like reference to the commercial dosemeter GR200A of Chinese manufacture. In both cases the Tl curve presents four peaks; in LiF: Mg,Cu,P + Ptfe, the peaks of smaller size appear in 359 K, 389 K and 447 K, the main dosimetric peak appears in 486 K; in GR200A, the peaks of smaller size appear in 360 K, 389 K and 445 K; while the main dosimetric peak appears in 487 K. The highest fading shown by the dosemeters of LiF: Mg,Cu,P + Ptfe, it was of 3.07%, value very below the one recommended for dosimetric purposes. While the commercial dosemeters presented a fading until of 6.23%, surpassing with the recommended values. The observed fading, it corresponds to the lost of the Tl signal of the peaks 1 and 2, since the first one disappears few hours after the irradiation, while the peak 2, it disappears completely after 94 days, the peak 3 remained stable during the six months of study, while the peak 4, it showed a slight increment due to the contribution of the dose of natural environmental radiation. (Author)
两种渐消滤波与自适应抗差滤波的综合比较分析%Comparison of Two Fading Filters and Adaptively Robust Filter
Institute of Scientific and Technical Information of China (English)
杨元喜; 高为广
2007-01-01
Two kinds of fading filters and their principles are introduced. An adaptive robust filter is given with corresponding principle. The basic abilities of the fading filters and adaptively robust filter in controlling the influences of the kinematic model errors are analyzed. A practical example is given. The results of the fading filter and adaptively robust filter are compared and analyzed.
International Nuclear Information System (INIS)
Kars, Romee H.; Wallinga, Jakob
2009-01-01
We recently proposed a model that reconstructs the natural dose response curve for K-rich feldspars, using laboratory fading measurements and dose response as input parameters. The model is based on the relationship between recombination centre density and trap lifetime. In this study we test the working of the model by comparing modelled feldspar ages with known quartz OSL ages of the same samples and with anomalous fading-corrected feldspar ages. The modelled feldspar ages are in good agreement with quartz OSL ages and corrected feldspar ages, opening possibilities for future use of the model on samples without independent age constraints. Furthermore, we investigate the effects of trap competition on the build-up of IRSL signal using two new variations of the model. Results show that incorporating trap competition into the model reduces the agreement between feldspar IRSL ages and quartz OSL ages.
Yilmaz, Ferkan
2014-04-01
The main idea in the moment generating function (MGF) approach is to alternatively express the conditional bit error probability (BEP) in a desired exponential form so that possibly multi-fold performance averaging is readily converted into a computationally efficient single-fold averaging - sometimes into a closed-form - by means of using the MGF of the signal-to-noise ratio. However, as presented in [1] and specifically indicated in [2] and also to the best of our knowledge, there does not exist an MGF-based approach in the literature to represent Wojnar\\'s generic BEP expression in a desired exponential form. This paper presents novel MGF-based expressions for calculating the average BEP of binary signalling over generalized fading channels, specifically by expressing Wojnar\\'s generic BEP expression in a desirable exponential form. We also propose MGF-based expressions to explore the amount of dispersion in the BEP for binary signalling over generalized fading channels.
A tâtonnement process with fading memory, stabilization and optimal speed of convergence
International Nuclear Information System (INIS)
Cavalli, Fausto; Naimzada, Ahmad
2015-01-01
The purpose of this work is to provide a way to improve stability and convergence rate of a price adjustment mechanism that converges to a Walrasian equilibrium. We focus on a discrete tâtonnement based on a two-agent, two-good exchange economy, and we introduce memory, assuming that the auctioneer adjusts prices not only using the current excess demand, but also making use of the past excess demand functions. In particular, we study the effect of computing a weighted average of the current and the previous excess demands (finite two level memory) and of all the previous excess demands (infinite memory). We show that suitable weights’ distributions have a stabilizing effect, so that the resulting price adjustment process converge toward the competitive equilibrium in a wider range of situations than the process without memory. Finally, we investigate the convergence speed toward the equilibrium of the proposed mechanisms. In particular, we show that using infinite memory with fading weights approaches the competitive equilibrium faster than with a distribution of quasi-uniform weights.
Improving 3D-Turbo Code's BER Performance with a BICM System over Rayleigh Fading Channel
Directory of Open Access Journals (Sweden)
R. Yao
2016-12-01
Full Text Available Classical Turbo code suffers from high error floor due to its small Minimum Hamming Distance (MHD. Newly-proposed 3D-Turbo code can effectively increase the MHD and achieve a lower error floor by adding a rate-1 post encoder. In 3D-Turbo codes, part of the parity bits from the classical Turbo encoder are further encoded through the post encoder. In this paper, a novel Bit-Interleaved Coded Modulation (BICM system is proposed by combining rotated mapping Quadrature Amplitude Modulation (QAM and 3D-Turbo code to improve the Bit Error Rate (BER performance of 3D-Turbo code over Raleigh fading channel. A key-bit protection scheme and a Two-Dimension (2D iterative soft demodulating-decoding algorithm are developed for the proposed BICM system. Simulation results show that the proposed system can obtain about 0.8-1.0 dB gain at BER of 10^{-6}, compared with the existing BICM system with Gray mapping QAM.
Analysis on Human Blockage Path Loss and Shadow Fading in Millimeter-Wave Band
Directory of Open Access Journals (Sweden)
Hongmei Zhao
2017-01-01
Full Text Available Millimeter-wave (Mm-w is the trend of communication development in the future; users who carry mobile communication equipment could be blocked by others in a crowded population environment. Based on Shooting and Bouncing Ray (SBR method and setting up different orientation receivers (RX, population density, and people fabric property at 28 GHz and 38 GHz, simulating experimental scene similar to station square by Wireless Insite software, we use least square method to do linear-regression analysis for path loss and build path loss model. The result shows that the path loss index has a certain change in the different frequency, orientation receivers, population density, and people fabric. The path loss index of RouteC1 and RouteA2 has an obvious change in the central transmitter (TX. Each route shadow fading obeys Gaussian distribution whose mean is 0. This paper’s result has a theoretical guiding for designing the communication system in a crowded population environment.
Joint Scheduling for Dual-Hop Block-Fading Broadcast Channels
Zafar, Ammar
2012-09-16
In this paper, we propose joint user-and-hop scheduling over dual-hop block-fading broadcast channels in order to exploit multi-user diversity gains and multi-hop diversity gains all together. To achieve this objective, the first and second hops are scheduled opportunistically based on the channel state information and as a prerequisite we assume that the relay, which is half-duplex and operates using decode-and-forward, is capable of storing the received packets from the source until the channel condition of the destined user becomes good to be scheduled. We formulate the joint scheduling problem as maximizing the weighted sum of the long term achievable rates by the users under a stability constraint, which means that on the long term the rate received by the relay should equal the rate transmitted by it, in addition to constant or variable power constraints. We show that this problem is equivalent to a single-hop broadcast channel by treating the source as a virtual user with an optimal priority weight that maintains the stability constraint. We show how to obtain the source weight either off-line based on channel statistics or on real-time based on channel measurements. Furthermore, we consider special cases including the maximum sum rate scheduler and the proportional fair scheduler. We demonstrate via numerical results that our proposed joint scheduling scheme enlarges the rate region as compared with a scheme that employs multi-user scheduling alone.
S0 galaxies are faded spirals: clues from their angular momentum content
Rizzo, Francesca; Fraternali, Filippo; Iorio, Giuliano
2018-05-01
The distribution of galaxies in the stellar specific angular momentum versus stellar mass plane (j⋆ - M⋆) provides key insights into their formation mechanisms. In this paper, we determine the location in this plane of a sample of 10 field/group unbarred lenticular (S0) galaxies from the Calar Alto Legacy Integral Field Area survey. We performed a bulge-disc decomposition both photometrically and kinematically to study the stellar specific angular momentum of the disc components alone and understand the evolutionary links between S0s and other Hubble types. We found that eight of our S0 discs have a distribution in the j⋆ - M⋆ plane that is fully compatible with that of spiral discs, while only two have values of j⋆ lower than the spirals. These two outliers show signs of recent merging. Our results suggest that merger and interaction processes are not the dominant mechanisms in S0 formation in low-density environments. Instead, S0s appear to be the result of secular processes and the fading of spiral galaxies after the shutdown of star formation.
Chelli, Ali
2014-11-01
In this paper, we study the performance of hybrid automatic repeat request (HARQ) with incremental redundancy over double Rayleigh channels, a common model for the fading amplitude of vehicle-to-vehicle communication systems. We investigate the performance of HARQ from an information theoretic perspective. Analytical expressions are derived for the \\\\epsilon-outage capacity, the average number of transmissions, and the average transmission rate of HARQ with incremental redundancy assuming a maximum number of HARQ rounds. Moreover, we evaluate the delay experienced by Poisson arriving packets for HARQ with incremental redundancy. We provide analytical expressions for the expected waiting time, the packet\\'s sojourn time in the queue, the average consumed power, and the energy efficiency. In our study, the communication rate per HARQ round is adjusted to the average signal-to-noise ratio (SNR) such that a target outage probability is not exceeded. This setting conforms with communication systems in which a quality of service is expected regardless of the channel conditions. Our analysis underscores the importance of HARQ in improving the spectral efficiency and reliability of communication systems. We demonstrate as well that the explored HARQ scheme achieves full diversity. Additionally, we investigate the tradeoff between energy efficiency and spectral efficiency.
Light-induced fading of the PSL signal from irradiated herbs and spices
International Nuclear Information System (INIS)
Alberti, A.; Corda, U.; Fuochi, P.; Bortolin, E.; Calicchia, A.; Onori, S.
2007-01-01
Reliability of the photo-stimulated luminescence (PSL) technique, as screening method for irradiated food identification, has been tested with three kinds of herbs and spices (oregano, red pepper and fennel), prepared in two different ways (granular: i.e. seeds and flakes, or powdered), over a long period of storage with different light exposures. The irradiated samples kept in the dark gave always a positive response (the sample is correctly classified as 'irradiated') for the overall examination period. The samples kept under ambient light conditions, in typical commercial glass containers, exhibited a reduction of the PSL signal, more or less pronounced depending on the type of food and packaging. The different PSL response of the irradiated samples is to be related to the quantity and quality of the mineral debris present in the individual food. It was also found that, for the same type of food, the light-induced fading was much stronger for the flaked and seed samples than for the corresponding powder samples, the penetrating capability of light being much more inhibited in powdered than in whole seeds or flaked form samples. The observed light bleaching of the PSL signal in irradiated herbs and spices is of practical relevance since it may lead to false negative classifications
MC-DS-CDMA System based on DWT and STBC in ITU Multipath Fading Channels Model
Directory of Open Access Journals (Sweden)
Nader Abdullah Khadam
2018-03-01
Full Text Available In this paper, the performance of multicarrier direct sequence code division multiple access (MC-DS-CDMA in fixed MC-DS-CDMA and Mobile MC-DS-CDMA applications have been improved by using the compensations of space time block coding and Discrete Fast Fourier transforms (FFT or Discrete Wavelets transform DWT. These MC-DS-CDMA systems had been simulated using MATLAB 2015a. Through simulation of the proposed system, various parameters can be changed and tested. The Bit Error Rate (BERs of these systems are obtained over wide range of signal to noise ratio. All simulation results had been compared with each other using different subcarrier size of FFT or DWT with STBC for 1,2,3 and 4 antennas in transmitter and under different ITU multipath fading channels and different Doppler frequencies (fd. The proposed structures of STBC-MC-DS-CDMA system based on (DWT batter than based on (FFT in varies Doppler frequencies and subcarrier size. Also, proposed system with STBC based on 4 transmitters better than other systems based on 1 or 2 or 3 transmitters in all Doppler frequencies and subcarrier size in all simulation results.
FADING CORONAL STRUCTURE AND THE ONSET OF TURBULENCE IN THE YOUNG SOLAR WIND
Energy Technology Data Exchange (ETDEWEB)
DeForest, C. E. [Southwest Research Institute, 1050 Walnut Street, Boulder, CO (United States); Matthaeus, W. H. [Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States); Viall, N. M. [NASA/Goddard Space Flight Center, Mail Code 671, Greenbelt, MD 20771 (United States); Cranmer, S. R. [University of Colorado, Duane E226, Boulder, CO 80305 (United States)
2016-09-10
Above the top of the solar corona, the young, slow solar wind transitions from low- β , magnetically structured flow dominated by radial structures to high- β , less structured flow dominated by hydrodynamics. This transition, long inferred via theory, is readily apparent in the sky region close to 10° from the Sun in processed, background-subtracted solar wind images. We present image sequences collected by the inner Heliospheric Imager instrument on board the Solar-Terrestrial Relations Observatory ( STEREO /HI1) in 2008 December, covering apparent distances from approximately 4° to 24° from the center of the Sun and spanning this transition in the large-scale morphology of the wind. We describe the observation and novel techniques to extract evolving image structure from the images, and we use those data and techniques to present and quantify the clear textural shift in the apparent structure of the corona and solar wind in this altitude range. We demonstrate that the change in apparent texture is due both to anomalous fading of the radial striae that characterize the corona and to anomalous relative brightening of locally dense puffs of solar wind that we term “flocculae.” We show that these phenomena are inconsistent with smooth radial flow, but consistent with the onset of hydrodynamic or magnetohydrodynamic instabilities leading to a turbulent cascade in the young solar wind.
Exact capture probability analysis of GSC receivers over Rayleigh fading channel
Nam, Sungsik
2010-01-01
For third generation systems and ultrawideband systems, RAKE receivers have been introduced due to the advantage of RAKE receivers which is their ability to combine different replicas of the transmitted signal arriving at different delays in a rich multipath environment. In principle, RAKE receivers combine all resolvable paths which gives the best performance in a rich diversity environment. However, this is usually costly in terms of hardware required as the number of RAKE fingers increases. Therefore, generalized selection combining (GSC) RAKE reception was proposed and has been studied by many researcher as an alternative to the classical two fundamental diversity schemes: maximal ratio combining and selection combining. Previous work on performance analyses of GSC RAKE receivers based on the signal to noise ratio focused on the development of methodologies to derive exact closedform expressions for various performance measures. However, the remaining set of uncombined paths affect the overall performance both in terms of loss in power. Therefore, to have a full understanding of the performance of GSC RAKE receivers, we introduce in this paper the notion of capture probability, which is defined as the ratio of the captured power (essentially combined paths power) to that of the total available power. The major difficulty in these problems is to derive some joint statistics of ordered exponential variates. With this motivation in mind, we capitalize in this paper on some new order statistics results to derive exact closed-form expressions for the capture probability over independent and identically distributed Rayleigh fading channels. © 2010 IEEE.
Stochastic Power Control for Time-Varying Long-Term Fading Wireless Networks
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Charalambous Charalambos D
2006-01-01
Full Text Available A new time-varying (TV long-term fading (LTF channel model which captures both the space and time variations of wireless systems is developed. The proposed TV LTF model is based on a stochastic differential equation driven by Brownian motion. This model is more realistic than the static models usually encountered in the literature. It allows viewing the wireless channel as a dynamical system, thus enabling well-developed tools of adaptive and nonadaptive estimation and identification techniques to be applied to this class of problems. In contrast with the traditional models, the statistics of the proposed model are shown to be TV, but converge in steady state to their static counterparts. Moreover, optimal power control algorithms (PCAs based on the new model are proposed. A centralized PCA is shown to reduce to a simple linear programming problem if predictable power control strategies (PPCS are used. In addition, an iterative distributed stochastic PCA is used to solve for the optimization problem using stochastic approximations. The latter solely requires each mobile to know its received signal-to-interference ratio. Generalizations of the power control problem based on convex optimization techniques are provided if PPCS are not assumed. Numerical results show that there are potentially large gains to be achieved by using TV stochastic models, and the distributed stochastic PCA provides better power stability and consumption than the distributed deterministic PCA.
Fading Coronal Structure and the Onset of Turbulence in the Young Solar Wind
DeForest, C. E.; Matthaeus, W. H.; Viall, N. M.; Cranmer, S. R.
2016-01-01
Above the top of the solar corona, the young, slow solar wind transitions from low-beta, magnetically structured flow dominated by radial structures to high-beta, less structured flow dominated by hydrodynamics. This transition, long inferred via theory, is readily apparent in the sky region close to 10deg from the Sun in processed, background-subtracted solar wind images. We present image sequences collected by the inner Heliospheric Imager instrument on board the Solar-Terrestrial Relations Observatory (STEREO/HI1) in 2008 December, covering apparent distances from approximately 4deg to 24deg from the center of the Sun and spanning this transition in the large-scale morphology of the wind. We describe the observation and novel techniques to extract evolving image structure from the images, and we use those data and techniques to present and quantify the clear textural shift in the apparent structure of the corona and solar wind in this altitude range. We demonstrate that the change in apparent texture is due both to anomalous fading of the radial striae that characterize the corona and to anomalous relative brightening of locally dense puffs of solar wind that we term "flocculae." We show that these phenomena are inconsistent with smooth radial flow, but consistent with the onset of hydrodynamic or magnetohydrodynamic instabilities leading to a turbulent cascade in the young solar wind.
On the performance of multiuser scheduling with post-examining under non-identical fading
Gaaloul, Fakhreddine; Alouini, Mohamed-Slim; Radaydeh, Redha M.; Yang, Hong-Chuan
2012-01-01
We investigate the performance of a multiuser downlink access scheme based on a post-selection switch and examine algorithm. The studied scheme sequentially switches over the users that experience independent and non-identically distributed fading conditions, and selects a single user with an acceptable channel quality as compared to a pre-selected signal-to-noise ratio (SNR) threshold. If no one of the users can satisfy the target channel quality, the base station (BS) takes the advantage of the knowledge of all users channels and serves the user with the best channel quality among all users. This scheme reduces considerably the feedback load but offers a lower average spectral efficiency (ASE) as compared to that of the full feedback system with instantaneous best user selection. On the other hand, it improves the system performances, such as outage probability and average bit error rate (BER), as compared to a system that is based on a standard switching scheme without post-selection. Numerical results for the ASE average BER, and average feed back load, are presented for the cases of outdated and non-outdated rate-adaptive modulation scheme operating over independent and non-identically distributed users.
On the performance of multiuser scheduling with post-examining under non-identical fading
Gaaloul, Fakhreddine
2012-06-11
We investigate the performance of a multiuser downlink access scheme based on a post-selection switch and examine algorithm. The studied scheme sequentially switches over the users that experience independent and non-identically distributed fading conditions, and selects a single user with an acceptable channel quality as compared to a pre-selected signal-to-noise ratio (SNR) threshold. If no one of the users can satisfy the target channel quality, the base station (BS) takes the advantage of the knowledge of all users channels and serves the user with the best channel quality among all users. This scheme reduces considerably the feedback load but offers a lower average spectral efficiency (ASE) as compared to that of the full feedback system with instantaneous best user selection. On the other hand, it improves the system performances, such as outage probability and average bit error rate (BER), as compared to a system that is based on a standard switching scheme without post-selection. Numerical results for the ASE average BER, and average feed back load, are presented for the cases of outdated and non-outdated rate-adaptive modulation scheme operating over independent and non-identically distributed users.
Lu, Xiaodong; Arfaoui, Helene; Mori, Kinji
In highly dynamic electronic commerce environment, the need for adaptability and rapid response time to information service systems has become increasingly important. In order to cope with the continuously changing conditions of service provision and utilization, Faded Information Field (FIF) has been proposed. FIF is a distributed information service system architecture, sustained by push/pull mobile agents to bring high-assurance of services through a recursive demand-oriented provision of the most popular information closer to the users to make a tradeoff between the cost of information service allocation and access. In this paper, based on the analysis of the relationship that exists among the users distribution, information provision and access time, we propose the technology for FIF design to resolve the competing requirements of users and providers to improve users' access time. In addition, to achieve dynamic load balancing with changing users preference, the autonomous information reallocation technology is proposed. We proved the effectiveness of the proposed technology through the simulation and comparison with the conventional system.
Furetta, C.
The paper describes a method, based on fading experiment, for determining the presence of a complex structure in the thermoluminescent glow curve emission from herbs, e.g. oregano and nopal. Because of the polymineral content of the inorganic part of these herbs, the emitted glow curve is the result of several overlapping glow peaks, each one corresponding to another mineral. The initial rise method is also used for determining the activation energy of each component.
Subhrakanti Dey; Minyi Huang
2007-01-01
We consider a joint rate and power control problem in a wireless data traffic relay network with fading channels. The optimization problem is formulated in terms of power and rate selection, and link transmission scheduling. The objective is to seek high aggregate utility of the relay node when taking into account buffer load management and power constraints. The optimal solution for a single transmitting source is computed by a two-layer dynamic programming algorithm which leads to optimal ...
Al-Quwaiee, Hessa
2014-03-01
Starting with the double generalized Gamma (GG) model that was proposed in [1] to describe turbulence-induced fading in free-space optical (FSO) systems, we propose a new unified model which accounts for the impact of pointing errors and type of receiver detector. Based on this new unified model, we study the performance of FSO links operating over these kind of channels. All our analytical results are verified using computer based Monte-Carlo simulations. © 2014 IEEE.
Axarlian, Gabriel Pablo
2015-01-01
AbstractFADE IN:EXPLORING THE EFFECTS OF TECHNOLOGICAL CHANGE ON CONSUMERS AND FIRM REVENUES IN HOME ENTERTAINMENT MARKETS FOR FILM Gabriel Axarlian This dissertation is composed of three related works, two of which are similar in data and time span with the third being more independent in this respect. The three works focus on the nature of the film industry’s adaptation to changing technologies in home entertainment markets. My analysis studies the effectiveness of new strategies as well ...
Tsai, Cheng-Ting; Chi, Yu-Chieh; Lin, Gong-Ru
2015-11-02
The pre-compensation on power fading effect of a colorless laser diode (CLD) carried 40-Gbit/s 256-QAM OFDM transmission during 25-km is demonstrated. By offsetting the DC bias to thrice the threshold (I(th)) and increasing the injection to 0 dBm, the CLD not only enhances its coherence but also suppresses modulation throughput declination and reduces the relative intensity related noise floor to -50 dBm. Modeling the receiving power of the delivered 256-QAM OFDM subcarriers is established, indicating that raising the bias to 3I(th) down-shifts the power fading induced notch to 8.8 GHz. This further degrades the OFDM subcarrier peak power by -2.9 dB after 25-km transmission, and the corresponded signal-to-noise ratio (SNR), error vector magnitude (EVM) and bit-error-rate (BER) are 26.1 dB, 4.9% and 6.5 × 10(-3), respectively. Pre-leveling the OFDM subcarrier as well as the modulation throughput effectively compromises the over-bias enlarged power fading to promote transmission. With a pre-leveled power slope of 1.5 dB/GHz for 256-QAM OFDM data, the modulation throughput declination of the high biased CLD significantly mitigates under BtB transmission, enabling the receiving sensitivity at -7.2 dBm with SNR, EVM and BER of 29.9 dB, 3.1% and 1.5 × 10(-4), respectively. Increasing the pre-leveling slope to 3.2 dB/GHz minimizes the fiber dispersion induced power fading, which improves the receiving SNR, EVM and BER to 27.4 dB, 4.2% and 2.6 × 10(-3), respectively, with receiving sensitivity of -3 dBm and power penalty of 4.2 dB after 25-km SMF transmission.
Al-Quwaiee, Hessa; Ansari, Imran Shafique; Alouini, Mohamed-Slim
2014-01-01
Starting with the double generalized Gamma (GG) model that was proposed in [1] to describe turbulence-induced fading in free-space optical (FSO) systems, we propose a new unified model which accounts for the impact of pointing errors and type of receiver detector. Based on this new unified model, we study the performance of FSO links operating over these kind of channels. All our analytical results are verified using computer based Monte-Carlo simulations. © 2014 IEEE.
Nam, Sung Sik; Ko, Young-Chai; Alouini, Mohamed-Slim; Choi, Seyeong
2017-01-01
. To supplement our previous work, we present a general comprehensive framework for the performance assessment of the proposed finger replacement schemes operating over independent but non-identically distributed (i.n.d.) faded paths. To accomplish this object, we
Yilmaz, Ferkan
2012-06-01
The exact analysis of the higher-order statistics of the channel capacity (i.e., higher-order ergodic capacity) often leads to complicated expressions involving advanced special functions. In this paper, we provide a generic framework for the computation of the higher-order statistics of the channel capacity over generalized fading channels. As such, this novel framework for the higher-order statistics results in simple, closed-form expressions which are shown to be asymptotically tight bounds in the high signal-to-noise ratio (SNR) regime of a variety of fading environment. In addition, it reveals the existence of differences (i.e., constant capacity gaps in log-domain) among different fading environments. By asymptotically tight bound we mean that the high SNR limit of the difference between the actual higher-order statistics of the channel capacity and its asymptotic bound (i.e., lower bound) tends to zero. The mathematical formalism is illustrated with some selected numerical examples that validate the correctness of our newly derived results. © 2012 IEEE.
MODELING THE GAMMA-RAY EMISSION IN THE GALACTIC CENTER WITH A FADING COSMIC-RAY ACCELERATOR
Energy Technology Data Exchange (ETDEWEB)
Liu, Ruo-Yu; Wang, Xiang-Yu; Prosekin, Anton [Max-Planck-Institut für Kernphysik, D-69117 Heidelberg (Germany); Chang, Xiao-Chuan, E-mail: ruoyu@mpi-hd.mpg.de, E-mail: xywang@nju.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)
2016-12-20
Recent HESS observations of the ∼200 pc scale diffuse gamma-ray emission from the central molecular zone (CMZ) suggest the presence of a PeV cosmic-ray accelerator (PeVatron) located in the inner 10 pc region of the Galactic center. Interestingly, the gamma-ray spectrum of the point-like source (HESS J1745-290) in the Galactic center shows a cutoff at ∼10 TeV, implying a cutoff around 100 TeV in the cosmic-ray proton spectrum. Here we propose that the gamma-ray emission from the inner and the outer regions may be explained self-consistently by run-away protons from a single yet fading accelerator. In this model, gamma-rays from the CMZ region are produced by protons injected in the past, while gamma-rays from the inner region are produced by protons injected more recently. We suggest that the blast wave formed in a tidal disruption event (TDE) caused by the supermassive black hole (Sgr A*) could serve as such a fading accelerator. With typical parameters of the TDE blast wave, gamma-ray spectra of both the CMZ region and HESS J1745-290 can be reproduced simultaneously. Meanwhile, we find that the cosmic-ray energy density profile in the CMZ region may also be reproduced in the fading accelerator model when appropriate combinations of the particle injection history and the diffusion coefficient of cosmic rays are adopted.
Rached, Nadhir B.
2016-12-24
In this paper, we develop a generalized momentbased approach for the evaluation of the outage probability (OP) in the presence of co-channel interference and additive white Gaussian noise. The proposed method allows the evaluation of the OP of the signal-to-interference-plus-noise ratio by a power series expansion in the threshold value. Its main advantage is that it does not require a particular distribution for the interference channels. The only necessary ingredients are a power series expansion for the cumulative distribution function of the desired user power and the cross-moments of the interferers\\' powers. These requirements are easily met in many practical fading models, for which the OP might not be obtained in closed-form expression. For a sake of illustration, we consider the application of our method to the Rician fading environment. Under this setting, we carry out a convergence study of the proposed power series and corroborate the validity of our method for different values of fading parameters and various numbers of co-channel interferers.
International Nuclear Information System (INIS)
Lee, Chang Hee; Kim, Kyeong Ah; Lee, Jongmee; Park, Yang Shin; Choi, Jae Woong; Seo, Tae Seok; Park, Cheol Min
2011-01-01
Objective: To evaluate the value of the fade-out sign in the diagnosis of fatty liver (FL) on hepatic ultrasound (US). Methods: We evaluated 127 patients who underwent hepatic US, including 70 patients with FL and 57 normal control subjects. US images were qualitatively evaluated for the presence of the fade-out sign. This sign was considered present if there was a dark band on the deep portion of the liver on the harmonic image when compound sonography (CS) was converted to tissue harmonic CS mode. The degrees of FL were classified into mild, moderate, and severe. The distribution of lengths of dark bands in three groups was examined, and a multiple comparison of the average dark band length was carried out using one-way ANOVA. Results: The fade-out sign was seen in 55 of 70 FL patients (78.6%) compared to 3 of 57 control subjects (5.3%) (p < 0.001). The sensitivity, specificity, accuracy, and positive predictive value of the fade-out sign for the US diagnosis of FL were 78%, 94%, 85.8%, and 94.8%, respectively. Among the 70 FL, there were 28 mild FL (mean length of dark band; 8.3 mm ± 8.2), 31 moderate FL (mean; 28 mm ± 6.3), and 11 severe FL (mean; 51 mm ± 8.3). There were significant differences in band length according to severity (p < 0.01). Conclusion: The fade-out sign on hepatic harmonic US was frequently present in FL. As fat infiltration increased, the fade-out sign lengthened. The fade-out sign offers a specific and new sign of FL.
Directory of Open Access Journals (Sweden)
Markku Renfors
2007-12-01
Full Text Available The ever-increasing public interest in location and positioning services has originated a demand for higher performance global navigation satellite systems (GNSSs. In order to achieve this incremental performance, the estimation of line-of-sight (LOS delay with high accuracy is a prerequisite for all GNSSs. The delay lock loops (DLLs and their enhanced variants (i.e., feedback code tracking loops are the structures of choice for the commercial GNSS receivers, but their performance in severe multipath scenarios is still rather limited. In addition, the new satellite positioning system proposals specify the use of a new modulation, the binary offset carrier (BOC modulation, which triggers a new challenge in the code tracking stage. Therefore, in order to meet this emerging challenge and to improve the accuracy of the delay estimation in severe multipath scenarios, this paper analyzes feedback as well as feedforward code tracking algorithms and proposes the peak tracking (PT methods, which are combinations of both feedback and feedforward structures and utilize the inherent advantages of both structures. We propose and analyze here two variants of PT algorithm: PT with second-order differentiation (Diff2, and PT with Teager Kaiser (TK operator, which will be denoted herein as PT(Diff2 and PT(TK, respectively. In addition to the proposal of the PT methods, the authors propose also an improved early-late-slope (IELS multipath elimination technique which is shown to provide very good mean-time-to-lose-lock (MTLL performance. An implementation of a noncoherent multipath estimating delay locked loop (MEDLL structure is also presented. We also incorporate here an extensive review of the existing feedback and feedforward delay estimation algorithms for direct sequence code division multiple access (DS-CDMA signals in satellite fading channels, by taking into account the impact of binary phase shift keying (BPSK as well as the newly proposed BOC modulation
Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission
International Nuclear Information System (INIS)
Cenko, S. Bradley; Nugent, Peter E.; Miller, Adam A.; Bloom, Joshua S.; Filippenko, Alexei V.; Kulkarni, S. R.; Horesh, Assaf; Carpenter, John; Perley, Daniel A.; Groot, Paul J.; Hallinan, G.; Corsi, Alessandra; Fox, Derek B.; Frail, Dale A.; Gruber, D.; Rau, Arne; Gal-Yam, Avishay; Ofek, Eran O.; MacLeod, Chelsea L.; Kasliwal, Mansi M.
2013-01-01
We report the discovery by the Palomar Transient Factory (PTF) of the transient source PTF11agg, which is distinguished by three primary characteristics: (1) bright (R peak = 18.3 mag), rapidly fading (ΔR = 4 mag in Δt = 2 days) optical transient emission; (2) a faint (R = 26.2 ± 0.2 mag), blue (g' – R = 0.17 ± 0.29 mag) quiescent optical counterpart; and (3) an associated year-long, scintillating radio transient. We argue that these observed properties are inconsistent with any known class of Galactic transients (flare stars, X-ray binaries, dwarf novae), and instead suggest a cosmological origin. The detection of incoherent radio emission at such distances implies a large emitting region, from which we infer the presence of relativistic ejecta. The observed properties are all consistent with the population of long-duration gamma-ray bursts (GRBs), marking the first time such an outburst has been discovered in the distant universe independent of a high-energy trigger. We searched for possible high-energy counterparts to PTF11agg, but found no evidence for associated prompt emission. We therefore consider three possible scenarios to account for a GRB-like afterglow without a high-energy counterpart: an 'untriggered' GRB (lack of satellite coverage), an 'orphan' afterglow (viewing-angle effects), and a 'dirty fireball' (suppressed high-energy emission). The observed optical and radio light curves appear inconsistent with even the most basic predictions for off-axis afterglow models. The simplest explanation, then, is that PTF11agg is a normal, on-axis long-duration GRB for which the associated high-energy emission was simply missed. However, we have calculated the likelihood of such a serendipitous discovery by PTF and find that it is quite small (≈2.6%). While not definitive, we nonetheless speculate that PTF11agg may represent a new, more common (>4 times the on-axis GRB rate at 90% confidence) class of relativistic
Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission
Energy Technology Data Exchange (ETDEWEB)
Cenko, S. Bradley; Nugent, Peter E.; Miller, Adam A.; Bloom, Joshua S.; Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Kulkarni, S. R.; Horesh, Assaf; Carpenter, John; Perley, Daniel A.; Groot, Paul J.; Hallinan, G. [Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Corsi, Alessandra [LIGO Laboratory, California Institute of Technology, MS 100-36, Pasadena, CA 91125 (United States); Fox, Derek B. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Frail, Dale A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Gruber, D.; Rau, Arne [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, D-85748 Garching (Germany); Gal-Yam, Avishay; Ofek, Eran O. [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel); MacLeod, Chelsea L. [Physics Department, United States Naval Academy, 572c Holloway Road, Annapolis, MD 21402 (United States); Kasliwal, Mansi M., E-mail: cenko@astro.berkeley.edu [Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States); and others
2013-06-01
We report the discovery by the Palomar Transient Factory (PTF) of the transient source PTF11agg, which is distinguished by three primary characteristics: (1) bright (R {sub peak} = 18.3 mag), rapidly fading (ΔR = 4 mag in Δt = 2 days) optical transient emission; (2) a faint (R = 26.2 ± 0.2 mag), blue (g' – R = 0.17 ± 0.29 mag) quiescent optical counterpart; and (3) an associated year-long, scintillating radio transient. We argue that these observed properties are inconsistent with any known class of Galactic transients (flare stars, X-ray binaries, dwarf novae), and instead suggest a cosmological origin. The detection of incoherent radio emission at such distances implies a large emitting region, from which we infer the presence of relativistic ejecta. The observed properties are all consistent with the population of long-duration gamma-ray bursts (GRBs), marking the first time such an outburst has been discovered in the distant universe independent of a high-energy trigger. We searched for possible high-energy counterparts to PTF11agg, but found no evidence for associated prompt emission. We therefore consider three possible scenarios to account for a GRB-like afterglow without a high-energy counterpart: an 'untriggered' GRB (lack of satellite coverage), an 'orphan' afterglow (viewing-angle effects), and a 'dirty fireball' (suppressed high-energy emission). The observed optical and radio light curves appear inconsistent with even the most basic predictions for off-axis afterglow models. The simplest explanation, then, is that PTF11agg is a normal, on-axis long-duration GRB for which the associated high-energy emission was simply missed. However, we have calculated the likelihood of such a serendipitous discovery by PTF and find that it is quite small (≈2.6%). While not definitive, we nonetheless speculate that PTF11agg may represent a new, more common (>4 times the on-axis GRB rate at 90% confidence) class of relativistic
In-situ X-ray absorption spectroscopy analysis of capacity fade in nanoscale-LiCoO{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Patridge, Christopher J. [NRC/NRL Cooperative Research Associate, U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Love, Corey T., E-mail: corey.love@nrl.navy.mil [Chemistry Division, Code 6113, U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Swider-Lyons, Karen E. [Chemistry Division, Code 6113, U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Twigg, Mark E. [Electronics Science and Technology Division, Code 6812, U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Ramaker, David E. [Chemistry Division, Code 6189, U.S. Naval Research laboratory, Washington, DC 20375 (United States)
2013-07-15
The local structure of nanoscale (∼10–40 nm) LiCoO{sub 2} is monitored during electrochemical cycling utilizing in-situ X-ray absorption spectroscopy (XAS). The high surface area of the LiCoO{sub 2} nanoparticles not only enhances capacity fade, but also provides a large signal from the particle surface relative to the bulk. Changes in the nanoscale LiCoO{sub 2} metal-oxide bond lengths, structural disorder, and chemical state are tracked during cycling by adapting the delta mu (Δμ) technique in complement with comprehensive extended X-ray absorption fine structure (EXAFS) modeling. For the first time, we use a Δμ EXAFS method, and by comparison of the difference EXAFS spectra, extrapolate significant coordination changes and reduction of cobalt species with cycling. This combined approach suggests Li–Co site exchange at the surface of the nanoscale LiCoO{sub 2} as a likely factor in the capacity fade and irreversible losses in practical, microscale LiCoO{sub 2}. - Graphical abstract: Electrochemical cycling of Li-ion batteries has strong impact on the structure and integrity of the cathode active material particularly near the surface/electrolyte interface. In developing a new method, we have used in-situ X-ray absorption spectroscopy during electrochemical cycling of nanoscale LiCoO{sub 2} to track changes during charge and discharge and between subsequent cycles. Using difference spectra, several small changes in Co-O bond length, Co-O and Co-Co coordination, and site exchange between Co and Li sites can be tracked. These methods show promise as a new technique to better understand processes which lead to capacity fade and loss in Li-ion batteries. - Highlights: • A new method is developed to understand capacity fade in Li-ion battery cathodes. • Structural changes are tracked during Li intercalation/deintercalation of LiCoO{sub 2}. • Surface structural changes are emphasized using nanoscale-LiCoO{sub 2} and difference spectra. • Full multiple
In-situ X-ray absorption spectroscopy analysis of capacity fade in nanoscale-LiCoO2
International Nuclear Information System (INIS)
Patridge, Christopher J.; Love, Corey T.; Swider-Lyons, Karen E.; Twigg, Mark E.; Ramaker, David E.
2013-01-01
The local structure of nanoscale (∼10–40 nm) LiCoO 2 is monitored during electrochemical cycling utilizing in-situ X-ray absorption spectroscopy (XAS). The high surface area of the LiCoO 2 nanoparticles not only enhances capacity fade, but also provides a large signal from the particle surface relative to the bulk. Changes in the nanoscale LiCoO 2 metal-oxide bond lengths, structural disorder, and chemical state are tracked during cycling by adapting the delta mu (Δμ) technique in complement with comprehensive extended X-ray absorption fine structure (EXAFS) modeling. For the first time, we use a Δμ EXAFS method, and by comparison of the difference EXAFS spectra, extrapolate significant coordination changes and reduction of cobalt species with cycling. This combined approach suggests Li–Co site exchange at the surface of the nanoscale LiCoO 2 as a likely factor in the capacity fade and irreversible losses in practical, microscale LiCoO 2 . - Graphical abstract: Electrochemical cycling of Li-ion batteries has strong impact on the structure and integrity of the cathode active material particularly near the surface/electrolyte interface. In developing a new method, we have used in-situ X-ray absorption spectroscopy during electrochemical cycling of nanoscale LiCoO 2 to track changes during charge and discharge and between subsequent cycles. Using difference spectra, several small changes in Co-O bond length, Co-O and Co-Co coordination, and site exchange between Co and Li sites can be tracked. These methods show promise as a new technique to better understand processes which lead to capacity fade and loss in Li-ion batteries. - Highlights: • A new method is developed to understand capacity fade in Li-ion battery cathodes. • Structural changes are tracked during Li intercalation/deintercalation of LiCoO 2 . • Surface structural changes are emphasized using nanoscale-LiCoO 2 and difference spectra. • Full multiple scattering calculations are used to
Path Loss, Shadow Fading, and Line-Of-Sight Probability Models for 5G Urban Macro-Cellular Scenarios
DEFF Research Database (Denmark)
Sun, Shu; Thomas, Timothy; Rappaport, Theodore S.
2015-01-01
This paper presents key parameters including the line-of-sight (LOS) probability, large-scale path loss, and shadow fading models for the design of future fifth generation (5G) wireless communication systems in urban macro-cellular (UMa) scenarios, using the data obtained from propagation...... measurements in Austin, US, and Aalborg, Denmark, at 2, 10, 18, and 38 GHz. A comparison of different LOS probability models is performed for the Aalborg environment. Both single-slope and dual-slope omnidirectional path loss models are investigated to analyze and contrast their root-mean-square (RMS) errors...
Cooney, Michele R; Short, Michelle A; Gradisar, Michael
2018-06-01
To evaluate the efficacy of bedtime fading to reduce sleep disturbances in preschool aged children by using a group parent education format. A repeated-measures design (pretreatment, treatment, post-treatment and two year follow-up). Flinders University Child and Adolescent Sleep Clinic, Adelaide, South Australia. Participants comprised 21 children (M age = 3.0 ± 0.80 years, range = 1.5-4.0 years; 60% girls) identified as having difficulty initiating sleep, night waking, or a combination of both, and their mothers (M age = 36.1 ± 4.2 years). Mothers attended two group sessions that included basic sleep education (sleep needs, sleep architecture, and sleep homeostasis) and bedtime fading instruction. Primary outcome variables were sleep onset latency (SOL), wake after sleep onset (WASO), and bedtime tantrums, and these variables were measured using two week maternal report sleep diaries. Immediate improvements were observed over pretreatment to treatment in average SOL per night (M = 23.2 ± 11.3 min vs. M = 13.0 ± 7.3 min, d = 0.91), average WASO per night (M = 32.4 ± 23.1 min vs. M = 24.0 ± 18.3 min, d = 0.41), and number of bedtime tantrums per week (M = 1.7 ± 3.0 vs. M = 0.4 ± 0.7, d = 0.43). Treatment gains were maintained at two year follow-up. Mothers rated bedtime fading high in terms of usefulness and satisfaction, and they reported that could successfully reimplement the treatment when needed. Bedtime fading is a brief and promising intervention for pre-schoolers' sleep difficulties. This simple intervention can be easily implemented by parents at home with little instructions, resulting in improvements in sleep and bedtime tantrums. Copyright © 2018 Elsevier B.V. All rights reserved.
On the performance of future full-duplex relay selection networks
Khafagy, Mohammad Galal
2015-09-01
In this work, we evaluate the performance of relay selection over Nakagami-m fading channels in the presence of a cluster of full-duplex decode-and-forward relays with self-interference. Specifically, we derive the exact cumulative distribution function of the end-to-end signal-to-interference-plus-noise ratio in the presence of a direct source-destination link. When a direct link exists, all dual-hop paths become mutually correlated due to the common direct-link interference. The presented exact results enable the evaluation of the outage performance and system throughput for fixed-rate transmission systems. The theoretical findings are verified by numerical simulations, where the severity of fading effect in the residual self-interference link is also discussed.
On the performance of future full-duplex relay selection networks
Khafagy, Mohammad Galal; Alouini, Mohamed-Slim; Aissa, Sonia
2015-01-01
In this work, we evaluate the performance of relay selection over Nakagami-m fading channels in the presence of a cluster of full-duplex decode-and-forward relays with self-interference. Specifically, we derive the exact cumulative distribution function of the end-to-end signal-to-interference-plus-noise ratio in the presence of a direct source-destination link. When a direct link exists, all dual-hop paths become mutually correlated due to the common direct-link interference. The presented exact results enable the evaluation of the outage performance and system throughput for fixed-rate transmission systems. The theoretical findings are verified by numerical simulations, where the severity of fading effect in the residual self-interference link is also discussed.
Capacity of fully correlated MIMO system using character expansion of groups
Directory of Open Access Journals (Sweden)
Ejaz Khan
2005-09-01
Full Text Available It is well known that the use of antenna arrays at both sides of communication link can result in high channel capacities provided that the propagation medium is rich scattering. In most previous works presented on MIMO wireless structures, Rayleigh fading conditions were considered. In this work, the capacity of MIMO systems under fully correlated (i.e., correlations between rows and columns of channel matrix fading is considered. We use replica method and character expansions to calculate the capacity of correlated MIMO channel in closed form. In our calculations, it is assumed that the receiver has perfect channel state information (CSI but no such information is available at the transmitter.
Directory of Open Access Journals (Sweden)
Jaewook Lee
2015-06-01
Full Text Available This paper presents an efficient method for estimating capacity-fade uncertainty in lithium-ion batteries (LIBs in order to integrate them into the battery-management system (BMS of electric vehicles, which requires simple and inexpensive computation for successful application. The study uses the pseudo-two-dimensional (P2D electrochemical model, which simulates the battery state by solving a system of coupled nonlinear partial differential equations (PDEs. The model parameters that are responsible for electrode degradation are identified and estimated, based on battery data obtained from the charge cycles. The Bayesian approach, with parameters estimated by probability distributions, is employed to account for uncertainties arising in the model and battery data. The Markov Chain Monte Carlo (MCMC technique is used to draw samples from the distributions. The complex computations that solve a PDE system for each sample are avoided by employing a polynomial-based metamodel. As a result, the computational cost is reduced from 5.5 h to a few seconds, enabling the integration of the method into the vehicle BMS. Using this approach, the conservative bound of capacity fade can be determined for the vehicle in service, which represents the safety margin reflecting the uncertainty.
Celandroni, N.; Ferro, E.; James, N.; Potorti, F.
1992-12-01
A flexible, processor based, TDMA station has been implemented. This station and its associated variable data rate modem enables users to implement very complex frame structures under software control. Burst rates of 512 kb/s-8x192 Mb/s and different coding rates are possible allowing the transmitted bit energy from each station in the network to be adapted to prevailing conditions. The proposed application of the station is the transmission of mixed stream and packet traffic, in a LANs interconnection via satellite environment, using a modification of the FODA technique. The association of the up-link power control feature with the bit and coding rate variation gives the system an interesting ability to cope with fade conditions. The link outage probability is investigated for the Olympus transponder in Ka band. The ability of the system, together with the good performance of Olympus, shows that the Ka band is usable for the above mentioned types of networks without prohibitive fade degradation, at least for limited coverages.
Directory of Open Access Journals (Sweden)
Chenguang Shi
2016-12-01
Full Text Available This paper investigates the joint target parameter (delay and Doppler estimation performance of linear frequency modulation (LFM-based radar networks in a Rice fading environment. The active radar networks are composed of multiple radar transmitters and multichannel receivers placed on moving platforms. First, the log-likelihood function of the received signal for a Rician target is derived, where the received signal scattered off the target comprises of dominant scatterer (DS component and weak isotropic scatterers (WIS components. Then, the analytically closed-form expressions of the Cramer-Rao lower bounds (CRLBs on the Cartesian coordinates of target position and velocity are calculated, which can be adopted as a performance metric to access the target parameter estimation accuracy for LFM-based radar network systems in a Rice fading environment. It is found that the cumulative Fisher information matrix (FIM is a linear combination of both DS component and WIS components, and it also demonstrates that the joint CRLB is a function of signal-to-noise ratio (SNR, target’s radar cross section (RCS and transmitted waveform parameters, as well as the relative geometry between the target and the radar network architectures. Finally, numerical results are provided to indicate that the joint target parameter estimation performance of active radar networks can be significantly improved with the exploitation of DS component.
Shi, Chenguang; Salous, Sana; Wang, Fei; Zhou, Jianjiang
2016-12-06
This paper investigates the joint target parameter (delay and Doppler) estimation performance of linear frequency modulation (LFM)-based radar networks in a Rice fading environment. The active radar networks are composed of multiple radar transmitters and multichannel receivers placed on moving platforms. First, the log-likelihood function of the received signal for a Rician target is derived, where the received signal scattered off the target comprises of dominant scatterer (DS) component and weak isotropic scatterers (WIS) components. Then, the analytically closed-form expressions of the Cramer-Rao lower bounds (CRLBs) on the Cartesian coordinates of target position and velocity are calculated, which can be adopted as a performance metric to access the target parameter estimation accuracy for LFM-based radar network systems in a Rice fading environment. It is found that the cumulative Fisher information matrix (FIM) is a linear combination of both DS component and WIS components, and it also demonstrates that the joint CRLB is a function of signal-to-noise ratio (SNR), target's radar cross section (RCS) and transmitted waveform parameters, as well as the relative geometry between the target and the radar network architectures. Finally, numerical results are provided to indicate that the joint target parameter estimation performance of active radar networks can be significantly improved with the exploitation of DS component.
Half-Duplex and Full-Duplex AF and DF Relaying with Energy-Harvesting in Log-Normal Fading
Rabie, Khaled M.
2017-08-15
Energy-harvesting (EH) and wireless power transfer in cooperative relaying networks have recently attracted a considerable amount of research attention. Most of the existing work on this topic however focuses on Rayleigh fading channels, which represent outdoor environments. In contrast, this paper is dedicated to analyze the performance of dual-hop relaying systems with EH over indoor channels characterized by log-normal fading. Both half-duplex (HD) and full-duplex (FD) relaying mechanisms are studied in this work with decode-and-forward (DF) and amplify-and-forward (AF) relaying protocols. In addition, three EH schemes are investigated, namely, time switching relaying, power splitting relaying and ideal relaying receiver which serves as a lower bound. The system performance is evaluated in terms of the ergodic outage probability for which we derive accurate analytical expressions. Monte Carlo simulations are provided throughout to validate the accuracy of our analysis. Results reveal that, in both HD and FD scenarios, AF relaying performs only slightly worse than DF relaying which can make the former a more efficient solution when the processing energy cost at the DF relay is taken into account. It is also shown that FD relaying systems can generally outperform HD relaying schemes as long as the loop-back interference in FD is relatively small. Furthermore, increasing the variance of the log-normal channel has shown to deteriorate the performance in all the relaying and EH protocols considered.
Directory of Open Access Journals (Sweden)
Gou Hosoya
2013-01-01
Full Text Available Approximate calculation of channel log-likelihood ratio (LLR for wireless channels using Padé approximation is presented. LLR is used as an input of iterative decoding for powerful error-correcting codes such as low-density parity-check (LDPC codes or turbo codes. Due to the lack of knowledge of the channel state information of a wireless fading channel, such as uncorrelated fiat Rayleigh fading channels, calculations of exact LLR for these channels are quite complicated for a practical implementation. The previous work, an LLR calculation using the Taylor approximation, quickly becomes inaccurate as the channel output leaves some derivative point. This becomes a big problem when higher order modulation scheme is employed. To overcome this problem, a new LLR approximation using Padé approximation, which expresses the original function by a rational form of two polynomials with the same total number of coefficients of the Taylor series and can accelerate the Taylor approximation, is devised. By applying the proposed approximation to the iterative decoding and the LDPC codes with some modulation schemes, we show the effectiveness of the proposed methods by simulation results and analysis based on the density evolution.
International Nuclear Information System (INIS)
Dolo, J.M.; Feaugas, V.; Pichot, E.
2000-01-01
The work of L.M.R.I. according to the research agreement contract is constituted of three parts which all contributed to the same objective: the better understanding of the phenomenon of production and disappearing of free radicals in the alanine dosimeter. The first part is the contribution to the accuracy of the measurements parameters and their optimisation. Many parameters such as the power level and the modulation amplitude must be chosen carefully. This part describes how we have defined the limits of the parameter values giving the best arrangement between the four objectives: the better signal-to-noise ratio with the highest amplitude of the central line, and the better reproducibility with a resolution as good as possible. The second part is our contribution to increase the understanding on how external parameters influence the chemical reactions in alanine. Two experimental studies of combined effects have been realised in the laboratory. A multi-parametric approach (experimental design) has shown the complexity of the problem. The chosen methodology permits to give the first global quantitative view of the fading. However the obtained results, that suggested a physico-chemical recombination reaction of the free radicals created during the irradiation, are not sufficient. The last part is a study of the kinetic aspect of the mechanism. The aim of this study is to indicate the number of transient species leading to this radical and their kinetics of reaction. We follow the evolution of the ESR/alanine spectrum shape and correlate the response estimated from the central peak height to the absorbed dose. From these hypothesis we modelize the kinetics of free radical densities and check their fitting with experiment. (author)
International Nuclear Information System (INIS)
Carinou, E.; Askounis, P.; Dimitropoulou, F.; Kiranos, G.; Kyrgiakou, H.; Nirgianaki, E.; Papadomarkaki, E.; Kamenopoulou, V.
2011-01-01
LiF is a well-known thermoluminescent (TL) material used in individual monitoring, and its fading characteristics have been studied for years. In the present study, the fading characteristics (for a period of 150 d) of various commercial LiF materials with different dopants have been evaluated. The materials used in the study are those used in routine procedures by the Personal Dosimetry Dept. of Greek Atomic Energy Commission and in particular, LiF:Mg,Ti (MTS-N, TL Poland), LiF:Mg,Cu,P (MCP-N, TL Poland), LiF:Mg,Cu,P (MCP-Ns, thin active layer detector, TL Poland) and LiF:Mg,Cu,P (TLD100H, Harshaw). The study showed that there is a sensitivity loss in signal of up to 20 % for the MTS-N material for a 150-d period in the pre-irradiation fading phase. The MCP-N has a stable behaviour in the pre-irradiation fading phase, but this also depends on the readout system. As far as the post-irradiation fading effect is concerned, a decrease of up to 20 % for the MTS-N material is observed for the same time period. On the other hand, the LiF:Mg,Cu,P material presents a stable behaviour within ±5 %. These results show that the fading effect is different for each material and should be taken into account when estimating doses from dosemeters that are in use for >2 months. (authors)
International Nuclear Information System (INIS)
Sina, S; Sadeghi, M; Faghihi, R
2014-01-01
Purpose: The pre-irradiation and post-irradiation fading of the Thermoluminescense dosimeter signals were investigated in this study. Methods: Two groups of TLD chips with pre-determined ECC values were used in this study. The two groups were divided into 6 series, each composing of 5 TLD chips.The first group was used for pre-irradiation fading. 5 TLDs were exposed to a known amount of radiation from Cs-137 source, and were read out the next day. After seven days, the other 5 TLDs were exposed to the same amount of radiation and were read out after a day. The other series of 5 TLDs were also exposed after 7,19,28, 59, and 90 days, and were read out a day after irradiation. The loss in TLD signal were obtained for all the above cases. The second group, was used for postirradiation fading. All the TLDs of this group were exposed to a known amount of radiation from Cs-137 source. The 6 series composed of 5 TLDs were read out after 1,7,19,28,59, and 90 days. The above-mentioned procedures for obtaining pre-irradiation, and post-irradiation fading were performed for three storage temperatures (25°C, 4°C, and −18°C). Results: According to the results obtained in this study, in case of pre-irradiation fading study, the signal losses after 90 days are 12%, 24%, and 17% for 25°C, 4°C, and −18°C respectively. In case of post-irradiation fading study, the sensitivity losses after 90 days are 25%, 216%, and 20% for 25°C, 4°C, and −18°C respectively. Conclusion: The results indicate that the optimized time between exposing and reading out, and also the optimized time between annealing and exposing is 1 day.The reduction of Storage temperature will reduce the post-irradiation fading, While temperature reduction does not have any effect on pre-irradiation fading
Energy Technology Data Exchange (ETDEWEB)
Sina, S [Radiation Research Center, Shiraz University, Shiraz (Iran, Islamic Republic of); Sadeghi, M [Nuclear Engineering department, Shiraz university, Shiraz (Iran, Islamic Republic of); Faghihi, R [Radiation Research Center, Shiraz University, Shiraz (Iran, Islamic Republic of); Nuclear Engineering department, Shiraz university, Shiraz (Iran, Islamic Republic of)
2014-06-01
Purpose: The pre-irradiation and post-irradiation fading of the Thermoluminescense dosimeter signals were investigated in this study. Methods: Two groups of TLD chips with pre-determined ECC values were used in this study. The two groups were divided into 6 series, each composing of 5 TLD chips.The first group was used for pre-irradiation fading. 5 TLDs were exposed to a known amount of radiation from Cs-137 source, and were read out the next day. After seven days, the other 5 TLDs were exposed to the same amount of radiation and were read out after a day. The other series of 5 TLDs were also exposed after 7,19,28, 59, and 90 days, and were read out a day after irradiation. The loss in TLD signal were obtained for all the above cases. The second group, was used for postirradiation fading. All the TLDs of this group were exposed to a known amount of radiation from Cs-137 source. The 6 series composed of 5 TLDs were read out after 1,7,19,28,59, and 90 days. The above-mentioned procedures for obtaining pre-irradiation, and post-irradiation fading were performed for three storage temperatures (25°C, 4°C, and −18°C). Results: According to the results obtained in this study, in case of pre-irradiation fading study, the signal losses after 90 days are 12%, 24%, and 17% for 25°C, 4°C, and −18°C respectively. In case of post-irradiation fading study, the sensitivity losses after 90 days are 25%, 216%, and 20% for 25°C, 4°C, and −18°C respectively. Conclusion: The results indicate that the optimized time between exposing and reading out, and also the optimized time between annealing and exposing is 1 day.The reduction of Storage temperature will reduce the post-irradiation fading, While temperature reduction does not have any effect on pre-irradiation fading.
Rezki, Zouheir
2013-07-01
We study the throughput capacity region of the Gaussian multi-access (MAC) fading channel with perfect channel state information (CSI) at the receiver and at the transmitters (CSI-TR), at low power regime. We show that it has a multidimensional rectangle structure and thus is simply characterized by single user capacity points. More specifically, we show that at low power regime, the boundary surface of the capacity region shrinks to a single point corresponding to the sum-rate maximizer and that the coordinates of this point coincide with single user capacity bounds. Using the duality of Gaussian MAC and broadcast channels (BC), we provide a simple characterization of the BC capacity region at low power regime. © 2013 IEEE.
Directory of Open Access Journals (Sweden)
Kim Yong-Seok
2005-01-01
Full Text Available We present the BER analysis of antenna array (AA receiver in reverse-link asynchronous multipath Rician channels and analyze the performance of an improved AA system which applies a reverse-link synchronous transmission technique (RLSTT in order to effectively make a better estimation of covariance matrices at a beamformer-RAKE receiver. In this work, we provide a comprehensive analysis of user capacity which reflects several important factors such as the ratio of the specular component power to the Rayleigh fading power, the shape of multipath intensity profile, and the number of antennas. Theoretical analysis demonstrates that for the case of a strong specular path's power or for a high decay factor, the employment of RLSTT along with AA has the potential of improving the achievable capacity by an order of magnitude.
Directory of Open Access Journals (Sweden)
Subhrakanti Dey
2007-08-01
Full Text Available We consider a joint rate and power control problem in a wireless data traffic relay network with fading channels. The optimization problem is formulated in terms of power and rate selection, and link transmission scheduling. The objective is to seek high aggregate utility of the relay node when taking into account buffer load management and power constraints. The optimal solution for a single transmitting source is computed by a two-layer dynamic programming algorithm which leads to optimal power, rate, and transmission time allocation at the wireless links. We further consider an optimal power allocation problem for multiple transmitting sources in the same framework. Performances of the resource allocation algorithms including the effect of buffer load control are illustrated via extensive simulation studies.
Directory of Open Access Journals (Sweden)
Yishan He
2015-01-01
Full Text Available Fast frequency hopping (FFH is commonly used as an antijamming communication method. In this paper, we propose efficient adaptive jamming suppression schemes for binary phase shift keying (BPSK based coherent FFH system, namely, weighted equal gain combining (W-EGC with the optimum and suboptimum weighting coefficient. We analyze the bit error ratio (BER of EGC and W-EGC receivers with partial band noise jamming (PBNJ, frequency selective Rayleigh fading, and channel estimation errors. Particularly, closed-form BER expressions are presented with diversity order two. Our analysis is verified by simulations. It is shown that W-EGC receivers significantly outperform EGC. As compared to the maximum likelihood (ML receiver in conventional noncoherent frequency shift keying (FSK based FFH, coherent FFH/BPSK W-EGC receivers also show significant advantages in terms of BER. Moreover, W-EGC receivers greatly reduce the hostile jammers’ jamming efficiency.
Directory of Open Access Journals (Sweden)
Selman KULAÇ
2017-08-01
Full Text Available Important interference problems will be able to be encountered especially close areas to the hospitals where wireless implantable medical systems' communication traffic occurs heavily in near future. It is possible that these interferences could cause wireless implant devices to malfunction and harmful effects on patients. In this study, it is proposed to determine threshold distance in order to get less interference for wireless implantable medical systems under shadow fading conditions where MICS band and MetAids band users coexist intensely simultaneously. In this method, threshold power according to the \\cite{FCC} is pulled down by adding extra distance margin in order to minimize the interference effects to the MICS systems using confidence interval calculations. Because received signal strength just below the monitoring threshold power according to the \\cite{FCC} brings about much more interferences for the MICS systems even if listen-before-talk technique is applied.
Wasiczko, Linda M.; Smolyaninov, Igor I.; Davis, Christopher C.
2004-01-01
Free space optics (FSO) is one solution to the bandwidth bottleneck resulting from increased demand for broadband access. It is well known that atmospheric turbulence distorts the wavefront of a laser beam propagating through the atmosphere. This research investigates methods of reducing the effects of intensity scintillation and beam wander on the performance of free space optical communication systems, by characterizing system enhancement using either aperture averaging techniques or nonimaging optics. Compound Parabolic Concentrators, nonimaging optics made famous by Winston and Welford, are inexpensive elements that may be easily integrated into intensity modulation-direct detection receivers to reduce fading caused by beam wander and spot breakup in the focal plane. Aperture averaging provides a methodology to show the improvement of a given receiver aperture diameter in averaging out the optical scintillations over the received wavefront.
Wang, Huiqin; Wang, Xue; Cao, Minghua
2017-02-01
The spatial correlation extensively exists in the multiple-input multiple-output (MIMO) free space optical (FSO) communication systems due to the channel fading and the antenna space limitation. Wilkinson's method was utilized to investigate the impact of spatial correlation on the MIMO FSO communication system employing multipulse pulse-position modulation. Simulation results show that the existence of spatial correlation reduces the ergodic channel capacity, and the reception diversity is more competent to resist this kind of performance degradation.
Confortin, D.; Neevel, H.; Brustolon, M.; Franco, L.; Kettelarij, A.J.; Williams, R.M.; van Bommel, M.R.
2010-01-01
The photo-fading of crystal violet (CV), one of the earliest synthetic dyes and an ink component, is examined both in solution and on paper. Aqueous solutions of CV were exposed to UV light (365nm) and samples were taken at constant time intervals and analysed with a High Performance Liquid
Howlett, Melissa A.; Sidener, Tina M.; Progar, Patrick R.; Sidener, David W.
2011-01-01
The effects of contriving motivating operations (MOs) and script fading on the acquisition of the mand "Where's [object]?" were evaluated in 2 boys with language delays. During each session, trials were alternated in which high-preference items were present (abolishing operation [AO] trials) or missing (establishing operation [EO] trials) from…
International Nuclear Information System (INIS)
Confortin, Daria; Brustolon, Marina; Franco, Lorenzo; Neevel, Han; Bommel, Maarten R van; Kettelarij, Albert J; Williams, Rene M
2010-01-01
The photo-fading of crystal violet (CV), one of the earliest synthetic dyes and an ink component, is examined both in solution and on paper. Aqueous solutions of CV were exposed to UV light (365nm) and samples were taken at constant time intervals and analysed with a High Performance Liquid Chromatography-Photo Diode Array (HPLC-PDA) and Liquid Chromatography-Mass Spectroscopy (LC-MS). Demethylation products were positively identified. Also, deamination probably occurred. The oxidation at the central carbon likely generates Michler's ketone (MK) or its derivatives, but still needs confirmation. To study CV on paper, Whatman paper was immersed in CV and exposed to UV light. Before and after different irradiation periods, reflectance spectra were recorded with Fibre Optic Reflectance Spectrophotometry (FORS). A decrease in CV concentration and a change in aggregation type for CV molecules upon irradiation was observed. Colorimetric L*a*b* values before and during irradiation were also measured. Also, CV was extracted from paper before and after different irradiation periods and analysed with HPLC-PDA. Photo-fading of CV on paper produced the same products as in solution, at least within the first 100 hours of irradiation. Finally, a photo-fading of CV in the presence of MK on Whatman paper was performed. It was demonstrated that MK both accelerates CV degradation and is consumed during the reaction. The degradation pathway identified in this work is suitable for explaining the photo/fading of other dyes belonging to the triarylmethane group.
DEFF Research Database (Denmark)
Thomsen, Kristina Jørkov; Murray, Andrew; Jain, Mayank
2012-01-01
Have recently proposed a new measurement procedure (MET-pIRIR) for luminescence dating using feldspar; they argue that this procedure reduces anomalous fading to negligible levels, and that it is a significant improvement over existing protocols (pIRIR290). Here we compare the measured equivalent...
Lee, YoungJu; Won, Yuho; Kang, Kidoo
2015-04-01
Passive integrating dosemeters [thermoluminescent dosimeter (TLD) and optically stimulated luminescence (OSL)] are the only legally permitted individual dosemeters for occupational external radiation exposure monitoring in Korea. Also its maximum issuing cycle does not exceed 3 months, and the Korean regulations require personal dosemeters for official assessment of external radiation exposure to be issued by an approved or rather an accredited dosimetry service according to ISO/IEC 17025. KHNP (Korea Hydro & Nuclear Power, LTD), a unique operating company of nuclear power plants (NPPs) in Korea, currently has a plan to extend a TLD issuing cycle from 1 to 3 months under the authors' fading error criteria, ±10%. The authors have performed a feasibility study that minimises post-irradiation fading effects within their maximum reading cycle employing pre-heating technique. They repeatedly performed irradiation/reading a bare TLD chip to determine optimum pre-heating conditions by analysing each glow curve. The optimum reading conditions within the maximum reading cycle of 3 months were decided: a pre-heating temperature of 165°C, a pre-heating time of 9 s, a heating rate of 25°C s(-1), a reading temperature of 300°C and an acquisition time of 10 s. The fading result of TLD-600 and TLD-700 carried by newly developed time temperature profile (TTP) showed a much smaller fading effect than that of current TTP. The result showed that the fading error due to a developed TTP resulted in a ∼5% signal loss, whereas a current TTP caused a ∼15% loss. The authors also carried out a legal performance test on newly developed TTP to confirm its possibility as an official dosemeter. The legal performance tests that applied the developed TTP satisfied the criteria for all the test categories. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
DEFF Research Database (Denmark)
Ilic-Delibasic, M.; Pejanovic-Djurisic, M.; Prasad, R.
2012-01-01
OFDM (Orthogonal Frequency Division Multiplexing) is proven to be a very effective modulation and multiple access technique that enables high data rate transmission. Due to its good performance it is already implemented in several standardized technologies, and it is very promising technique...... conditions. In order to calculate BER (Bit Error Rate) for the considered OFDM polarization diversity system with a certain level of the received signals correlation, we propose a novel analytical method. The obtained results are compared with the ones attained by simulation....
Kim, Yong Beom; Lee, Sangseok; Lee, Kyeong Chun; Kim, Ha Jung; Ro, Young Jin; Yang, Hong-Seuk
2017-07-01
This study investigated the effect of muscarinic M 1 and M 2 receptor antagonists on the rocuronium-induced train of four (TOF) fade and tetanic fade, respectively. Ex-vivo phrenic nerves and diaphragms were obtained from adult Sprague-Dawley rats and stabilized in Krebs buffer; the nerve-stimulated muscle TOF fade was observed at 20 s intervals. For the TOF study, phrenic nerves and diaphragms were incubated with pirenzepine (an M 1 blocker) at concentrations of 0 nmol L -1 (control), 10 nmol L -1 (PZP10), or 100 nmol L -1 (PZP100). Rocuronium was then administered incrementally until the first twitch tension had depressed by >95% during TOF stimulation. The mean TOF ratios were compared when the first twitch tensions were depressed by 40%-50%. For the tetanic fade study, 50 Hz/5 s tetani was applied initially, 30 min after the administration of a loading dose of rocuronium and methoctramine (an M 2 receptor blocker, loaded at 0 μmol L -1 [control], 1 μmol L -1 [MET1], or 10 μmol L -1 [MET10]). The EC 95 of rocuronium was significantly lower in the PZP10 group than in the control group. In the PZP10 group, the TOF ratios at 50% and first twitch tension depression were significantly lower than those in the control group (P=.02). During tetanic stimulation, the tetanic fade was significantly enhanced in the MET10 group compared to the other groups. This study shows that antagonists of muscarinic M 1 and M 2 receptors affect the rocuronium-induced neuromuscular block as demonstrated by the reduced EC 95 and TOF ratios (M 1 antagonist, pirenzepine) or the enhanced 50-Hz tetanic fade (M 2 antagonist, methoctramine). © 2017 The Authors. Clinical and Experimental Pharmacology and Physiology Published by John Wiley & Sons Australia, Ltd.
International Nuclear Information System (INIS)
Tao, Laifa; Cheng, Yujie; Lu, Chen; Su, Yuzhuan; Chong, Jin; Jin, Haizu; Lin, Yongshou; Noktehdan, Azadeh
2017-01-01
Highlights: •The model is linked to known physicochemical degradation processes and material properties. •Aging dynamics of various battery formulations can be understood by the proposed model. •Large number of experiments will be reduced to accelerate the battery design process. •This approach can describe batteries under various operating conditions. •The proposed model is simple and easily implemented. -- Abstract: A five-state nonhomogeneous Markov chain model, which is an effective and promising way to accelerate the Li-ion battery design process by investigating the capacity fading dynamics of different formulations during the battery design phase, is reported. The parameters of this model are linked to known physicochemical degradation dynamics and material properties. Herein, the states and behaviors of the active materials in Li-ion batteries are modelled. To verify the efficiency of the proposed model, a dataset from approximately 3 years of cycling capacity fading experiments of various formulations using several different materials provided by Contemporary Amperex Technology Limited (CATL), as well as a NASA dataset, are employed. The capabilities of the proposed model for different amounts (50%, 70%, and 90%) of available experimental capacity data are tested and analyzed to assist with the final design determination for manufacturers. The average relative errors of life cycling prediction acquired from these tests are less than 2.4%, 0.8%, and 0.3%, even when only 50%, 70%, and 90% of the data, respectively, is available for different anode materials, electrolyte materials, and individual batteries. Furthermore, the variance is 0.518% when only 50% of the data are available; i.e., one can save at least 50% of the total experimental time and cost with an accuracy greater than 97% in the design phase, which demonstrates an effective and promising way to accelerate the Li-ion battery design process. The qualitative and quantitative analyses
Directory of Open Access Journals (Sweden)
Laura Garcia
2007-11-01
Full Text Available The inter- and intrasite correlation properties of shadow fading and power-weighted angle spread at both the mobile station and the base station are studied utilizing narrowband multisite MIMO measurements in the 1800Ã¢Â€Â‰MHz band. The influence of the distance between two base stations on the correlation is studied in an urban environment. Measurements have been conducted for two different situations: widely separated as well as closely located base stations. Novel results regarding the correlation of the power-weighted angle spread between base station sites with different separations are presented. Furthermore, the measurements and analysis presented herein confirm the autocorrelation and cross-correlation properties of the shadow fading and the angle spread that have been observed in previous studies.
International Nuclear Information System (INIS)
Giraud, B.G.; Heumann, J.M.; Lapedes, A.S.
1999-01-01
The fact that correlation does not imply causation is well known. Correlation between variables at two sites does not imply that the two sites directly interact, because, e.g., correlation between distant sites may be induced by chaining of correlation between a set of intervening, directly interacting sites. Such 'noncausal correlation' is well understood in statistical physics: an example is long-range order in spin systems, where spins which have only short-range direct interactions, e.g., the Ising model, display correlation at a distance. It is less well recognized that such long-range 'noncausal' correlations can in fact be stronger than the magnitude of any causal correlation induced by direct interactions. We call this phenomenon superadditive correlation (SAC). We demonstrate this counterintuitive phenomenon by explicit examples in (i) a model spin system and (ii) a model continuous variable system, where both models are such that two variables have multiple intervening pathways of indirect interaction. We apply the technique known as decimation to explain SAC as an additive, constructive interference phenomenon between the multiple pathways of indirect interaction. We also explain the effect using a definition of the collective mode describing the intervening spin variables. Finally, we show that the SAC effect is mirrored in information theory, and is true for mutual information measures in addition to correlation measures. Generic complex systems typically exhibit multiple pathways of indirect interaction, making SAC a potentially widespread phenomenon. This affects, e.g., attempts to deduce interactions by examination of correlations, as well as, e.g., hierarchical approximation methods for multivariate probability distributions, which introduce parameters based on successive orders of correlation. copyright 1999 The American Physical Society
Nam, Sung Sik
2017-06-12
A new finger replacement technique which is applicable for RAKE receivers in the soft handover region has been proposed and studied under the ideal assumption that the fading is both independent and identically distributed from path to path. To supplement our previous work, we present a general comprehensive framework for the performance assessment of the proposed finger replacement schemes operating over independent but non-identically distributed (i.n.d.) faded paths. To accomplish this object, we derive new closed-form expressions for the target key statistics which are composed of i.n.d. exponential random variables. With these new expressions, the performance analysis of various wireless communication systems over more practical channel environments can be possible.
International Nuclear Information System (INIS)
Hiroi, Tomoko; Ootaki, Masanori; Nawa, Yukino; Kuwabara, Rie; Tatsunami, Shinobu; Matsui, Hiroaki; Kumazawa, Yutaka; Yamamoto, Takio
2014-01-01
Radiation warning signs posted on the exterior of radiation facilities become faded and discolored with time. There are various types of commercially available laminating films for protecting signs from ultraviolet light. We examined the protection effect of polyvinyl chloride (PVC), acrylic resin and fluororesin films applied to the surface of radiation warning signs. The laminated signs were exposed to direct sunlight on the wall of an air filter chamber of a radiation facility for 1200 days. Simultaneously, another set of laminated signs was exposed to light from a xenon-arc weatherometer for 1200 hours. After exposure, the colors on the surface of each sign were evaluated digitally by using a spectrum colorimeter. The results indicated that lamination with a film that blocks ultraviolet light is effective for protecting the signs from fading and discoloration. For long-term protection under direct sunlight, PVC was the most effective among the three materials tested. (author)
International Nuclear Information System (INIS)
Tsirliganis, N.C.; Polymeris, G.S.; Kitis, G.; Pagonis, V.
2007-01-01
The anomalous fading (AF) of thermoluminescence (TL) and optically stimulated luminescence (OSL) signals in Durango apatite is attributed to tunnelling effects. Electrons from the TL and OSL traps in this material are transferred, via a tunnelling effect, to the recombination sites. The availability of recombination sites for tunnelled electrons is of major importance for the degree of AF rate observed in this material. It is expected that a variation of the number of the electron recombination sites will be reflected in the experimentally measured AF rate. In the present work an investigation of the recombination sites for the tunnelled electrons is attempted by studying the AF effect using a special technique, in which the anomalously faded TL (OSL) is replaced by an equal amount of TL (OSL) induced by a beta dose
Muir, Kate; Madill, Anna; Brown, Charity
2017-11-01
The capacity to perceive internal bodily states is linked to emotional awareness and effective emotional regulation. We explore individual differences in emotional awareness in relation to the fading affect bias (FAB), which refers to the greater dwindling of unpleasant compared to pleasant emotions in autobiographical memory. We consider interoceptive awareness and alexithymia in relation to the FAB, and private event rehearsal as a mediating process. With increasing interoceptive awareness, there was an enhanced FAB, but with increasing alexithymia, there was a decreased FAB. Further, the effects of interoceptive awareness were partially mediated by private rehearsal of pleasant events. We provide novel evidence that capacity for emotional awareness and thus effective processing is an important factor predictive of the FAB. Moreover, our results imply an important role for maintaining positive affect in the FAB. Our findings offer new insights into the effects of interoception and alexithymia on autobiographical memory, and support concepts of the FAB emerging as a result of adaptive emotional regulation processes.
Directory of Open Access Journals (Sweden)
Kang Jin-Gu
2008-01-01
Full Text Available Abstract Transition metal oxides have been suggested as innovative, high-energy electrode materials for lithium-ion batteries because their electrochemical conversion reactions can transfer two to six electrons. However, nano-sized transition metal oxides, especially Co3O4, exhibit drastic capacity decay during discharge/charge cycling, which hinders their practical use in lithium-ion batteries. Herein, we prepared nano-sized Co3O4with high crystallinity using a simple citrate-gel method and used electrochemical impedance spectroscopy method to examine the origin for the drastic capacity fading observed in the nano-sized Co3O4anode system. During cycling, AC impedance responses were collected at the first discharged state and at every subsequent tenth discharged state until the 100th cycle. By examining the separable relaxation time of each electrochemical reaction and the goodness-of-fit results, a direct relation between the charge transfer process and cycling performance was clearly observed.
Hussein, Ahmed Abdulqader; Rahman, Tharek A; Leow, Chee Yen
2015-12-04
Localization is an apparent aspect of a wireless sensor network, which is the focus of much interesting research. One of the severe conditions that needs to be taken into consideration is localizing a mobile target through a dispersed sensor network in the presence of physical barrier attacks. These attacks confuse the localization process and cause location estimation errors. Range-based methods, like the received signal strength indication (RSSI), face the major influence of this kind of attack. This paper proposes a solution based on a combination of multi-frequency multi-power localization (C-MFMPL) and step function multi-frequency multi-power localization (SF-MFMPL), including the fingerprint matching technique and lateration, to provide a robust and accurate localization technique. In addition, this paper proposes a grid coloring algorithm to detect the signal hole map in the network, which refers to the attack-prone regions, in order to carry out corrective actions. The simulation results show the enhancement and robustness of RSS localization performance in the face of log normal shadow fading effects, besides the presence of physical barrier attacks, through detecting, filtering and eliminating the effect of these attacks.
Directory of Open Access Journals (Sweden)
Huu Phu Bui
2010-01-01
Full Text Available Multiple-input multiple-output (MIMO systems employ advanced signal processing techniques. However, the performance is affected by propagation environments and antenna characteristics. The main contributions of the paper are to investigate Doppler spectrum based on measured data in a typical meeting room and to evaluate the performance of MIMO systems based on an eigenbeam-space division multiplexing (E-SDM technique in an indoor time-varying fading environment, which has various distributions of scatterers, line-of-sight wave existence, and mutual coupling effect among antennas. We confirm that due to the mutual coupling among antennas, patterns of antenna elements are changed and different from an omnidirectional one of a single antenna. Results based on the measured channel data in our measurement campaigns show that received power, channel autocorrelation, and Doppler spectrum are dependent not only on the direction of terminal motion but also on the antenna configuration. Even in the obstructed-line-of-sight environment, observed Doppler spectrum is quite different from the theoretical U-shaped Jakes one. In addition, it has been also shown that a channel change during the time interval between the transmit weight matrix determination and the actual data transmission can degrade the performance of MIMO E-SDM systems.
Ben Issaid, Chaouki; Rached, Nadhir B.; Kammoun, Abla; Alouini, Mohamed-Slim; Tempone, Raul
2017-01-01
The Gamma-Gamma distribution has recently emerged in a number of applications ranging from modeling scattering and reverbation in sonar and radar systems to modeling atmospheric turbulence in wireless optical channels. In this respect, assessing the outage probability achieved by some diversity techniques over this kind of channels is of major practical importance. In many circumstances, this is intimately related to the difficult question of analyzing the statistics of a sum of Gamma-Gamma random variables. Answering this question is not a simple matter. This is essentially because outage probabilities encountered in practice are often very small, and hence the use of classical Monte Carlo methods is not a reasonable choice. This lies behind the main motivation of the present work. In particular, this paper proposes a new approach to estimate the left tail of the sum of independent and identically distributed Gamma-Gamma variates. More specifically, we propose a mean-shift importance sampling scheme that efficiently evaluates the outage probability of L-branch maximum ratio combining diversity receivers over Gamma-Gamma fading channels. The proposed estimator satisfies the well-known bounded relative error criterion. We show the accuracy and the efficiency of our approach compared to naive Monte Carlo via some selected numerical simulations.
Nam, Sungsik
2011-08-01
Spread spectrum receivers with generalized selection combining (GSC) RAKE reception were proposed and have been studied as alternatives to the classical two fundamental schemes: maximal ratio combining and selection combining because the number of diversity paths increases with the transmission bandwidth. Previous work on performance analyses of GSC RAKE receivers based on the signal to noise ratio focused on the development of methodologies to derive exact closed-form expressions for various performance measures. However, some open problems related to the performance evaluation of GSC RAKE receivers still remain to be solved such as the exact performance analysis of the capture probability and an exact assessment of the impact of self-interference on GSC RAKE receivers. The major difficulty in these problems is to derive some joint statistics of ordered exponential variates. With this motivation in mind, we capitalize in this paper on some new order statistics results to derive exact closed-form expressions for the capture probability and outage probability of GSC RAKE receivers subject to self-interference over independent and identically distributed Rayleigh fading channels, and compare it to that of partial RAKE receivers. © 2011 IEEE.
Nam, Sungsik
2010-11-01
Previous work on performance analyses of generalized selection combining (GSC) RAKE receivers based on the signal to noise ratio focused on the development of methodologies to derive exact closed-form expressions for various performance measures. However, some open problems related to the performance evaluation of GSC RAKE receivers still remain to be solved such that an assessment of the impact of self-interference on the performance of GSC RAKE receivers. To have a full and exact understanding of the performance of GSC RAKE receivers, the outage probability of GSC RAKE receivers needs to be analyzed as closed-form expressions. The major difficulty in this problem is to derive some joint statistics of ordered exponential variates. With this motivation in mind, we capitalize in this paper on some new order statistics results to derive exact closed-form expressions for outage probability of GSC RAKE receivers subject to self-interference over independent and identically distributed Rayleigh fading channels. © 2010 IEEE.
Do, Nhu Tri; Bao, Vo Nguyen Quoc; An, Beongku
2016-02-26
In this paper, we study relay selection in decode-and-forward wireless energy harvesting cooperative networks. In contrast to conventional cooperative networks, the relays harvest energy from the source's radio-frequency radiation and then use that energy to forward the source information. Considering power splitting receiver architecture used at relays to harvest energy, we are concerned with the performance of two popular relay selection schemes, namely, partial relay selection (PRS) scheme and optimal relay selection (ORS) scheme. In particular, we analyze the system performance in terms of outage probability (OP) over independent and non-identical (i.n.i.d.) Rayleigh fading channels. We derive the closed-form approximations for the system outage probabilities of both schemes and validate the analysis by the Monte-Carlo simulation. The numerical results provide comprehensive performance comparison between the PRS and ORS schemes and reveal the effect of wireless energy harvesting on the outage performances of both schemes. Additionally, we also show the advantages and drawbacks of the wireless energy harvesting cooperative networks and compare to the conventional cooperative networks.
Ben Issaid, Chaouki
2017-04-01
The Gamma-Gamma distribution has recently emerged in a number of applications ranging from modeling scattering and reverbation in sonar and radar systems to modeling atmospheric turbulence in wireless optical channels. In this respect, assessing the outage probability achieved by some diversity techniques over this kind of channels is of major practical importance. In many circumstances, this is intimately related to the difficult question of analyzing the statistics of a sum of Gamma-Gamma random variables. Answering this question is not a simple matter. This is essentially because outage probabilities encountered in practice are often very small, and hence the use of classical Monte Carlo methods is not a reasonable choice. This lies behind the main motivation of the present work. In particular, this paper proposes a new approach to estimate the left tail of the sum of independent and identically distributed Gamma-Gamma variates. More specifically, we propose a mean-shift importance sampling scheme that efficiently evaluates the outage probability of L-branch maximum ratio combining diversity receivers over Gamma-Gamma fading channels. The proposed estimator satisfies the well-known bounded relative error criterion. We show the accuracy and the efficiency of our approach compared to naive Monte Carlo via some selected numerical simulations.
International Nuclear Information System (INIS)
Charles, M.W.
1983-01-01
This paper summarises some techniques for extending the usefulness of conventional phosphors in personnel, environmental and accident dosimetry. An optimised procedure for utilising radiation sensitisation and UV re-estimation in thermoluminescent LiF is presented. In particular it is shown that optimum performance is achieved by using a UV wavelength of 250 +- 10 nm for both the UV/thermal anneal following sensitisation, and for the UV re-estimation procedure. In the case of Harshaw Lif Chips (3x3x0.9 mm 3 ) the sensitivity is increased by a factor of 4-5 to achieve a minimum detectable dose of approx.=10 μGy (2sigma) and a minimum re-estimable dose of 50-100 mGy (2sigma), dependent on batch. Sensitized LiF also exhibits improved tissue equivalence, extended linearity and improved precision at low doses. The information from fast-fading glow peaks, which is normally rejected, is shown to have a useful application to the evaluation of short-term increases in environmental dose rates such as may occur following accidental releases of radioactivity. (orig.)
Directory of Open Access Journals (Sweden)
A. O. Olopade
2014-01-01
Full Text Available Third generation communication systems require receivers with wide bandwidth of operation to support high transmission rates and are also reconfigurable to support various communication standards with different frequency bands. An ideal software defined radio (SDR will be the absolute answer to this requirement but it is not achievable with the current level of technology. This paper proposes the use of a six-port receiver (SPR front-end (FE in a WCDMA communication system. A WCDMA end-to-end physical layer MATLAB demo which includes a multipath channel distortion block is used to determine the viability of the six-port based receiver. The WCDMA signal after passing through a multipath channel is received using a constructed SPR FE. The baseband signal is then calibrated and corrected in MATLAB. The six-port receiver performance is measured in terms of bit error rate (BER. The signal-to-noise ratio (SNR of the transmitted IQ data is varied and the BER profile of the communication system is plotted. The effect of the multipath fading on the receiver performance and the accuracy of the calibration algorithm are obtained by comparing two different measured BER curves for different calibration techniques to the simulated BER curve of an ideal receiver.
Abdulqader Hussein, Ahmed; Rahman, Tharek A.; Leow, Chee Yen
2015-01-01
Localization is an apparent aspect of a wireless sensor network, which is the focus of much interesting research. One of the severe conditions that needs to be taken into consideration is localizing a mobile target through a dispersed sensor network in the presence of physical barrier attacks. These attacks confuse the localization process and cause location estimation errors. Range-based methods, like the received signal strength indication (RSSI), face the major influence of this kind of attack. This paper proposes a solution based on a combination of multi-frequency multi-power localization (C-MFMPL) and step function multi-frequency multi-power localization (SF-MFMPL), including the fingerprint matching technique and lateration, to provide a robust and accurate localization technique. In addition, this paper proposes a grid coloring algorithm to detect the signal hole map in the network, which refers to the attack-prone regions, in order to carry out corrective actions. The simulation results show the enhancement and robustness of RSS localization performance in the face of log normal shadow fading effects, besides the presence of physical barrier attacks, through detecting, filtering and eliminating the effect of these attacks. PMID:26690159