PERFORMANCE OF LDPC CODED FMT SYSTEMS OVER FREQUENCY SELECTIVE FADING CHANNEL
Institute of Scientific and Technical Information of China (English)
Li Qiang; Bi Guangguo; Du Peng
2005-01-01
This paper proposes the Low Density Parity Check (LDPC) coded Filtered MultiTone (FMT) systems with high-order modulation for the high data rate reliable transmission over frequency selective fading channel. For the purpose of accomplishing soft input soft output iterative decoding of LDPC codes, a new soft decision metric generation method is proposed,which obviates the need of the noise variance estimation, for M-PSK/M-QAM-type high-order modulation over frequency selective fading channel. Computer simulation indicates that, there is no performance loss with our new metric, but the complexity of implementation is reduced, and that the LDPC codes are effective to improve the Bit Error Rate (BER) of FMT in frequency selective fading channel.
Performance of transmit-reference radio system in frequency-selective fading channels
Wang, Jing; Haartsen, J.C.
2005-01-01
Noise-based Transmit-Reference (TR) radio system is a simple and practical candidate for ultra-wideband (UWB) communication applications. This paper evaluates the performance of the Transmit-Reference radio system in a frequency-selective fading channel by theoretical analysis and computer
A New Adaptive Channel Estimation for Frequency Selective Time Varying Fading OFDM Channels
Afifi, Wessam M
2010-01-01
In this paper a new algorithm for adaptive dynamic channel estimation for frequency selective time varying fading OFDM channels is proposed. The new algorithm adopts a new strategy that successfully increases OFDM symbol rate. Instead of using a fixed training pilot sequence, the proposed algorithm uses a logic controller to choose among several available training patterns. The controller choice is based on the cross-correlation between pilot symbols over two consecutive time instants (which is considered to be a suitable measure of channel stationarity) as well as the deviation from the desired BER. Simulation results of the system performance confirm the effectiveness of this new channel estimation technique over traditional non-adaptive estimation methods in increasing the data rate of OFDM symbols while maintaining the same probability of error.
Precoded OFDM System for ICI Mitigation over Time-Frequency Selective Fading Channels
Institute of Scientific and Technical Information of China (English)
LONG Yi; KUANG Linling; LU Jianhua
2009-01-01
In orthogonal frequency-division multiplexing (OFDM) systems, the capability to support high mo-bility is greatly limited by the intercarrier interference (ICI) caused by time-frequency selective fading chan-nels. This paper presents a precoded OFDM system for ICI mitigation. A precoder is introduced to relieve the ICI by transmitting N-point composite information symbols at twice the subcarrier interval. A Ha-damard-matrix-like pilot pattern is used to recover the composite information symbols in a postprocessor at the receiver. Simulations show that, compared to the conventional self-cancellation scheme, this scheme gives much better signal-to-interference-noise ratio performance with much less overhead. Furthermore, the scheme can support twice the vehicle speed in time-frequency selective fading channels than the standard OFDM systems without ICI mitigation.
A Non-orthogonal STFC-OFDM on Frequency-Selective Fading Channels
Institute of Scientific and Technical Information of China (English)
XUE Yi; JIANG Ling-ge; HE Chen
2005-01-01
A new non-orthogonal space-time-frequency code (STFC) was proposed. In conjunction with orthogonal frequency-division multiplexing (OFDM), it is appropriate for the application on frequency-selective fading channels. On the basis of the existing non-orthogonal STC, frequency diversity is studied and a new non-orthogonal STFC is further designed. Monte-Carlo simulations show that the non-orthogonal STFC-OFDM has the advantage of large diversity order, high bandwidth efficiency and better BER performance when compared with the orthogonal STC/STFC OFDM and non-orthogonal STC-OFDM systems.
Complexity Iterative Receiver for Turbo-BLAST over Frequency Selective Fading Channels
Institute of Scientific and Technical Information of China (English)
DU Na; XU Da-zhuan
2008-01-01
The computationally efficient iterative receiver is investigated for Turbo-BLAST ( Bell Labs layered space time) system over frequency selective fading channels. Compared with the conventional receiver based on soft interference cancellation ( SIC), an iterative detection scheme based on bit-level cancellation is presented to reduce the complexity of the receiver by decomposing of an M-QAM constellation into a linear combination of binary constellations. Simulation results demonstrate that compared with the conventional SIC scheme, the proposed scheme based on bit-level cancellation performs almost as well as the SIC scheme after several iterations while proving a lot of saving in computational complexity.
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.
Directory of Open Access Journals (Sweden)
Youhua Ma
2012-08-01
Full Text Available In this paper, we consider the joint problem of relay selection and optimal power allocation for multi-relay amplify-and-forward (AF cooperative communication system over frequency selective fading channels. An optimization model combined relay selection and power allocation under a total transmission power budget is formulated. Then, this combinatorial problem is solved in a distributed strategy. Relay selection with a new threshold-based multiple-relay selection (MRS scheme is implemented at first, and then power is allocated between source and the selected relays in an optimized way to maximize channel capacity. Simulation result shows that the proposed joint scenario with relay selection and power allocation achieves better throughput performance than that of parallel-relay scenario (means that random relay is selected to forward data and allocated part of total power on average. Furthermore, the performances of the new MRS scheme and other relay selection strategies are also investigated.
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.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A novel cooperative diversity scheme based on Distributed Space-Time Block Coding and Multi-Carrier Code Division Multiple Access (DSTBC-MC-CDMA) is proposed which works well in frequency selective fading channels with multiple single-antenna users. And an analytical error model is established to describe the symbol decoding errors between interusers, based on which a close form expression for theoretical Bit Error Rate (BER) performance of the scheme is derived to analyze the influence of the interuser decoding errors on the BER performance of the scheme. Then simulation is complimented to verify the analytic result above, which also shows that the BER performance of DSTBC-MC-CDMA outgoes that of non-cooperative MC-CDMA with considerable gains. Furthermore, the simulations coincide with the theoretical results well.
Secured Communication over Frequency-Selective Fading Channels: A Practical Vandermonde Precoding
Directory of Open Access Journals (Sweden)
Mari Kobayashi
2009-01-01
Full Text Available We study the frequency-selective broadcast channel with confidential messages (BCC where the transmitter sends a confidential message to receiver 1 and a common message to receivers 1 and 2. In the case of a block transmission of N symbols followed by a guard interval of L symbols, the frequency-selective channel can be modeled as a N×(N+L Toeplitz matrix. For this special type of multiple-input multiple-output channels, we propose a practical Vandermonde precoding that projects the confidential messages in the null space of the channel seen by receiver 2 while superposing the common message. For this scheme, we provide the achievable rate region and characterize the optimal covariance for some special cases of interest. Interestingly, the proposed scheme can be applied to other multiuser scenarios such as the K+1-user frequency-selective BCC with K confidential messages and the two-user frequency-selective BCC with two confidential messages. For each scenario, we provide the secrecy degree of freedom (s.d.o.f. region of the corresponding channel and prove the optimality of the Vandermonde precoding. One of the appealing features of the proposed scheme is that it does not require any specific secrecy encoding technique but can be applied on top of any existing powerful encoding schemes.
Secured Communication over Frequency-Selective Fading Channels: A Practical Vandermonde Precoding
Directory of Open Access Journals (Sweden)
Debbah Mérouane
2009-01-01
Full Text Available We study the frequency-selective broadcast channel with confidential messages (BCC where the transmitter sends a confidential message to receiver 1 and a common message to receivers 1 and 2. In the case of a block transmission of symbols followed by a guard interval of symbols, the frequency-selective channel can be modeled as a Toeplitz matrix. For this special type of multiple-input multiple-output channels, we propose a practical Vandermonde precoding that projects the confidential messages in the null space of the channel seen by receiver 2 while superposing the common message. For this scheme, we provide the achievable rate region and characterize the optimal covariance for some special cases of interest. Interestingly, the proposed scheme can be applied to other multiuser scenarios such as the -user frequency-selective BCC with confidential messages and the two-user frequency-selective BCC with two confidential messages. For each scenario, we provide the secrecy degree of freedom (s.d.o.f. region of the corresponding channel and prove the optimality of the Vandermonde precoding. One of the appealing features of the proposed scheme is that it does not require any specific secrecy encoding technique but can be applied on top of any existing powerful encoding schemes.
Institute of Scientific and Technical Information of China (English)
ZHANG Xiaodong; BI Guangguo
2001-01-01
A wavelet packet function based multiple access (WPMA) system is developed in this paper to maximize capacity and improve receiver performance over frequency selective multipath fading channels. To design an efficient receiver that mitigates residual multiple access interference (MAI) and intersymbol interference, while improving received signal-to-interference and noise ratio (SINR) simultaneously on the uplink, a multichannel decision feedback equalizer (DFE) following a wavelet packet function based RAKE receiver is proposed. Simulation results show that, over GSM TU channels the developed receiver performs quite well if the power of each user is perfectly controlled or the space diversity combining (SDC) technique is applied.
Secured Communication over Frequency-Selective Fading Channels: a practical Vandermonde precoding
Kobayashi, Mari; Shamai, Shlomo
2009-01-01
In this paper, we study the frequency-selective broadcast channel with confidential messages (BCC) in which the transmitter sends a confidential message to receiver 1 and a common message to receivers 1 and 2. In the case of a block transmission of N symbols followed by a guard interval of L symbols, the frequency-selective channel can be modeled as a N * (N+L) Toeplitz matrix. For this special type of multiple-input multiple-output (MIMO) channels, we propose a practical Vandermonde precoding that consists of projecting the confidential messages in the null space of the channel seen by receiver 2 while superposing the common message. For this scheme, we provide the achievable rate region, i.e. the rate-tuple of the common and confidential messages, and characterize the optimal covariance inputs for some special cases of interest. It is proved that the proposed scheme achieves the optimal degree of freedom (d.o.f) region. More specifically, it enables to send l <= L confidential messages and N-l common mes...
Institute of Scientific and Technical Information of China (English)
Chen Jing; Zhu Qi
2008-01-01
In this paper, the design of signal constellations parameters is studied for Differential Unitary Space-Time Modulation (DUSTM) based on the design criterion of maximizing the diversity product. Farther, noninteger searching method for the signal constellation parameters design is proposed in order to get better codes. Experimental results show that under the different Doppler spread and data transmission rate, the proposed design performs better than the previous design using integer parameters in Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing(MIMO-OFDM) system over frequency-selective fading channels.
Directory of Open Access Journals (Sweden)
Sudesh Gupta
2011-12-01
Full Text Available In this paper we propose a compact MIMO system in frequency-selective fading channels which improves the performance of Wireless Media. A MIMO beam forming system model with mutual coupling and matching network is proposed to cope with frequency-selective fading channels. The overall system proposed transfer matrix is derived using Z-parameter method. The system using the transform matrix which accepts the relay and the delay matrix for the computation. Then apply the diversity criteria by which we can make the code output pair which is distinct. So we can obtain two different pairs one is shows the below value in the MIMO System one is the Higher value. It is the only way to achieve orthogonally. One particular problem with this is that it has uneven power among the symbols it transmits. This means that the signal does not have a constant envelope and that the power each antenna must transmit has to vary, both of which are undesirable. We can take the middle value which overcomes this problem.
Directory of Open Access Journals (Sweden)
Mr. Sudesh Gupta
2011-09-01
Full Text Available In this paper we propose a compact MIMO system in frequency-selective fading channels which improves the performance of Wireless Media. A MIMO beam forming system model with mutual coupling and matching network is proposed to cope with frequency-selective fading channels. The overall system proposed transfer matrix is derived using Z-parameter method. The system using the transform matrix which accepts the relay and the delay matrix for the computation. Then apply the diversity criteria by which we can make the code output pair which is distinct. So we can obtain two different pairs one is shows the below value in the MIMO System one is the Higher value. It is the only way to achieve orthogonally. One particular problem with this is that it has uneven power among the symbols it transmits. This means that the signal does not have a constant envelope and that the power each antenna must transmit has to vary, both of which are undesirable. We can take the middle value which overcomes this problem.
Directory of Open Access Journals (Sweden)
Ahmed BANNOUR
2010-05-01
Full Text Available In this paper we suggest to use the ASTC (Algebraic Space Time Codes as powerful coding technique for IEEE802.11x OFDM standard combined with PAPR reduction scheme. ASTC with their very Algebraic- constructionbased on Quaternionic algebra, have a full rate, full diversity, non-vanishing constant minimum determinant forincreasing spectral efficiency, uniform average transmitted energy per antenna and good shaping, readily lendthemselves to high data rate situations. However, by their construction they require a nonselective flat fadingchannels belonging to narrow-band systems. In fact, such systems are not readily found in airs interfaces. Inopen air we have what are commonly called frequency-selective fading channels. As a matter of fact, it becomesextremely necessary to harness their power for wide-band systems.
Institute of Scientific and Technical Information of China (English)
Du Zheng-Cong; Tang Bin; Liu Li-Xin
2006-01-01
In this paper, a new observation equation of non-Gaussian frequency selective fading Bell Labs layered space time (BLAST) architecture system is proposed, which is used for frequency selective fading channels and non-Gaussian noise in an application environment of BLAST system. With othogonal matrix triangularization (QR decomposition) of the channel matrix, the static observation equation of frequency selective fading BLAST system is transformed into a dynamic state space model, and then the particle filter is used for space-time layered detection. Making the full use of the finite alphabet of the digital modulation communication signal, the optimal proposal distribution can be chosen to produce particle and update the weight. Incorporated with current method of reducing error propagation, a new space-time layered detection algorithm is proposed. Simulation result shows the validity of the proposed algorithm.
On Frequency Offset Estimation Using the iNET Preamble in Frequency Selective Fading Channels
2014-03-01
ASM fields; (bottom) the relationship between the indexes of the received samples r(n), the signal samples s(n), the preamble samples p (n) and the short...frequency offset estimators for SOQPSK-TG equipped with the iNET preamble and operating in ISI channels. Four of the five estimators exam - ined here are...sync marker ( ASM ), and data bits (an LDPC codeword). The availability of a preamble introduces the possibility of data-aided synchro- nization in
Adaptive Resource Allocation for the PB/MC-CDMA System in Frequency Selective Fading Channels
Lee, Kyujin; Lee, Kyesan
We propose Adaptive Resource Allocation for the Partial Block MC-CDMA (ARA-PB/MC-CDMA) system. The ARA-PB/MC-CDMA system aims to improve total throughput performance and frequency efficiency across various channel conditions. It adaptively changes the number of blocks to improve the throughput performance and frequency efficiency according to the Signal to Interference Ratio (SIR). Therefore, the proposed system supports various Quality of Service (QoS) requirements for various SIR values.
Institute of Scientific and Technical Information of China (English)
杨维; 程时昕
2003-01-01
The conventional 2D-Rake receivers for code-division multiple access (CDMA) system over frequency-selective fading channels are generally based on the second-order statistics while assuming perfect array conditions. However, the sensor response, location uncertainty, and the use of sample statistics can severely degrade the performance of second-order statistics processing. And in practical application, it is impossible to calibrate the array frequently. In this paper a cumulant-based 2D-Rake receiver for synchronous CDMA system with decorrelator is presented. Decorrelating is a multi-user detection approach that not only provides a fundamental solution to the mutual interference problem in CDMA communications but also makes it convenient for the decoupled signal to be processed spatially and temporally. High-order signal processing has some inherent advantages over that of second-order. Employing second-order statistics it is impossible to estimate source steering vector blindly, while employing higher than second-order cumulants, this purpose can be achieved. The performance analysis shows that employing cumulant-based signal processing technique the proposed 2D-Rake receiver is blind and demonstrates excellent performance.
Institute of Scientific and Technical Information of China (English)
李勇朝; 廖桂生; 仝文宁
2006-01-01
To improve the performance of space-time coding over downlink frequency-selective correlated fading channels, a novel transmission scheme combining eigenbeamforming and OFDM is proposed. Provided that the channel correlated statistics are available at the transmitter, the wideband correlated fading channels can be converted into an independent FIR channel with 2 transmitting antennas and N receiving antennas by eigenbeamforming and dimension reduction. OFDM is utilized to convert the FIR channel into a group of independent parallel subchannels to carry space-time codes. With the new structure, the performance of space-time coding over downlink wideband correlated fading channels is greatly improved and the system complexity is reduced. Validity of the proposed system is verified by simulations under different conditions. Comparison between the new structure and an available structure is made both theoretically and computationally.
BLIND CHANNEL ESTIMATION IN DELAY DIVERSITY FOR FREQUENCY SELECTIVE CHANNELS
Institute of Scientific and Technical Information of China (English)
Zhao Zheng; Jia Ying; Yin Qinye
2003-01-01
Delay diversity is an effective transmit diversity technique to combat adverse ef-fects of fading. Thus far, previous work in delay diversity assumed that perfect estimates ofcurrent channel fading conditions are available at the receiver and training symbols are requiredto estimate the channel from the transmitter to the receiver. However, increasing the number ofthe antennas increases the required training interval and reduces the available time within whichdata may be transmitted. Learning the channel coefficients becomes increasingly difficult for thefrequency selective channels. In this paper, with the subspace method and the delay character ofdelay diversity, a channel estimation method is proposed, which does not use training symbols. Itaddresses the transmit diversity for a frequency selective channel from a single carrier perspectivein the form of a simple equivalent fiat fading model. Monte Carlo simulations give the perfor-mance of channel estimation and the performance comparison of our channel-estimation-baseddetector with decision feedback equalization, which uses the perfect channel information.
Directory of Open Access Journals (Sweden)
J. Zavrtalek
2015-09-01
Full Text Available The article introduces a novel concept of a PLC modem as a complement to the existing G3 and PRIME standards for communications using medium- or high-voltage overhead or cable lines. The proposed concept is based on the fact that the levels of impulse noise and frequency selectivity are lower on high-voltage lines than on low-voltage ones. Also, the demands for “cost-effective” circuitry design are not so crucial as in the case of modems for low-voltage level. In contract to these positive conditions, however, there is the need to overcome much longer distances and to take into account low SNR on the receiving side. With respect to the listed reasons, our concept makes use of MCM, instead of OFDM. The assumption of low SNR is compensated through the use of an efficient channel coding based on a serially concatenated turbo code. In addition, MCM offers lower latency and PAPR compared to OFDM. Therefore, when using MCM, it is possible to excite the line with higher power. The proposed concept has been verified during experimental transmission of testing data over a real, 5 km long, 22kV overhead line.
Error Probability of MRC in Frequency Selective Nakagami Fading in the Presence of CCI and ACI
Rahman, Mohammad Azizur; Sum, Chin-Sean; Funada, Ryuhei; Sasaki, Shigenobu; Baykas, Tuncer; Wang, Junyi; Harada, Hiroshi; Kato, Shuzo
An exact expression of error rate is developed for maximal ratio combining (MRC) in an independent but not necessarily identically distributed frequency selective Nakagami fading channel taking into account inter-symbol, co-channel and adjacent channel interferences (ISI, CCI and ACI respectively). The characteristic function (CF) method is adopted. While accurate analysis of MRC performance cannot be seen in frequency selective channel taking ISI (and CCI) into account, such analysis for ACI has not been addressed yet. The general analysis presented in this paper solves a problem of past and present interest, which has so far been studied either approximately or in simulations. The exact method presented also lets us obtain an approximate error rate expression based on Gaussian approximation (GA) of the interferences. It is shown, especially while the channel is lightly faded, has fewer multipath components and a decaying delay profile, the GA may be substantially inaccurate at high signal-to-noise ratio. However, the exact results also reveal an important finding that there is a range of parameters where the simpler GA is reasonably accurate and hence, we don't have to go for more involved exact expression.
SPECTRAL CORRELATION METHOD IN THE IDENTIFICATION OF FREQUENCY-SELECTIVE FADING RADIO ENVIRONMENT
Institute of Scientific and Technical Information of China (English)
Weng Hong; Wang Hongyuan; Yu Guowen
2006-01-01
Many modulated communication signals exhibit a cyclostationarity (or periodic correlation) property. To exploit the underlying periodicity of the modulated signal in the real-time recognition scheme of radio environments, this letter introduces a spectral correlation method to identify the number and the direction of multi-path in the environment of frequency-selective fading channel. By simulation, the graphs of spatial spectra corresponding to a certain cycle frequency is presented to show the accuracy of spectral correlation method in multi-path environment recognition.
DEFF Research Database (Denmark)
Christensen, Lars P.B.; Larsen, Jan
2006-01-01
A general Variational Bayesian framework for iterative data and parameter estimation for coherent detection is introduced as a generalization of the EM-algorithm. Explicit solutions are given for MIMO channel estimation with Gaussian prior and noise covariance estimation with inverse-Wishart prio...
Directory of Open Access Journals (Sweden)
Wang Jinpeng
2016-01-01
Full Text Available In this study, a theoretical foundation is built to evaluate the downlink performance of an MC-CDMA cellular system with site diversity operation with and receive antenna diversity combining. An expression for the theoretical conditional bit error rate (BER for the given set of channel gains is derived based on Gaussian approximation of the interference components in the composite receive signal. The local average BER is then obtained by averaging the conditional BER over the given set of channel gains using Monte-Carlo numerical method. The outage probability is measured from the numerically obtained cumulative distribution of the local average BER to determine the downlink capacity. Results from theoretical computation are compared to the results from computer simulation and discussed.
Digital communications over fading channels
Beltz, Nathan E.; Robertson, R. Clark
2004-01-01
In this report, the probabilities of bit error for the most commonly used digital modulation techniques are analyzed. Analytic solutions are developed for the probability of bit error when the signal is affected by the most commonly encountered impairment to system performance for a wireless channel, the transmission of the signal over a fading channel. In this report, the effect of a slow, flat Ricean fading channel on communications systems performance is examined. Since channel fading ...
Institute of Scientific and Technical Information of China (English)
强蔚; 张中兆; 沙学军
2002-01-01
a method is proposed to improve the performance of MC-2D-CDMA in frequency selective fading channel. Each chip of spreading spectrum sequence is contained in two sub-carriers, so when fading is deep in one sub-carrier, the other will compensate and the performance of this model is improved in frequency selective channel. Orthogonal restore combination (ORC) is used to explain the method. Computer simulation is used to exam the relation of signal noise ratio (SNR) and probability of bit error (BER), and the number of subscribers and BER. Then performance is compared among MC-2D-CDMA, MC-DS-CDMA and MC-CDMA.
Institute of Scientific and Technical Information of China (English)
WUGang; TANGYouxi; LIShaoqian
2004-01-01
A novel deterministic model for downlink Multiple-input multiple-output (MIMO) channel with nonisotropic scattering around Mobile station (MS) is presented. For both Space-time codes (STC) scenario and Downlink beam-forming (DBF) scenario, statistical fading characteristics, including level-crossing rate, average duration of fades, and envelope cross-correlation are investigated in frequency-selective fast fading channels. The impact of non-isotropic scattering on capacity of MIMO channel is also studied. Numerical results show that loss of ergodic capacity caused by non-isotropic scattering almost reach 1bit/Hz/s for a 2×2 MIMO channel and maximum achievable capacity will be degraded mainly by transmit correlation rather than non-isotropic scattering.
Space-Time Block Coding for Time Slotted CDMA Systems with Frequency-Selective Fading
Institute of Scientific and Technical Information of China (English)
WANGYingmin; YIKechu; NIUZhongxia; TIANHongxin
2003-01-01
The radio channel fading is one of the most important physical limitations for wireless mobile communications. Space-time coding is a coding technique that is designed for use with multiple transmit antennas and offers an effective transmit diversity technique to combat fading. However, most existing space-time coding schemes assume fiat fading that may not be valid for wideband wireless mobile communication channels. In this paper, a novel spacetime block coding scheme based on block processing is proposed for time slotted CDMA systems with frequencyselective fading. In order to get quasi-orthogonality, we encode the information based on the two data fields (blocks) of a burst, other than the symbols in a data field (block). As a consequence, it is convenient for block processing of joint detection which can be used with just some small modifications of the algorithms with no space-time coding. For decoding the new space time codes, block linear joint detection algorithms are developed. Then, we simplify these algorithms with an iterative procedure. With moderate iterative times, the computation complexity of the simplified algorithms is much less than that of the exact algorithms. Simulation results show that the performance of the simplified joint detection algorithms approximates to that of the exact ones.
Frequency selective tunable spin wave channeling in the magnonic network
Energy Technology Data Exchange (ETDEWEB)
Sadovnikov, A. V., E-mail: sadovnikovav@gmail.com; Nikitov, S. A. [Laboratory “Metamaterials,” Saratov State University, Saratov 410012 (Russian Federation); Kotel' nikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow 125009 (Russian Federation); Beginin, E. N.; Odincov, S. A.; Sheshukova, S. E.; Sharaevskii, Yu. P. [Laboratory “Metamaterials,” Saratov State University, Saratov 410012 (Russian Federation); Stognij, A. I. [Scientific-Practical Materials Research Center, National Academy of Sciences of Belarus, 220072 Minsk (Belarus)
2016-04-25
Using the space-resolved Brillouin light scattering spectroscopy, we study the frequency and wavenumber selective spin-wave channeling. We demonstrate the frequency selective collimation of spin-wave in an array of magnonic waveguides, formed between the adjacent magnonic crystals on the surface of yttrium iron garnet film. We show the control over spin-wave propagation length by the orientation of an in-plane bias magnetic field. Fabricated array of magnonic crystal can be used as a magnonic platform for multidirectional frequency selective signal processing applications in magnonic networks.
Distributive estimation of frequency selective channels for massive MIMO systems
Zaib, Alam
2015-12-28
We consider frequency selective channel estimation in the uplink of massive MIMO-OFDM systems, where our major concern is complexity. A low complexity distributed LMMSE algorithm is proposed that attains near optimal channel impulse response (CIR) estimates from noisy observations at receive antenna array. In proposed method, every antenna estimates the CIRs of its neighborhood followed by recursive sharing of estimates with immediate neighbors. At each step, every antenna calculates the weighted average of shared estimates which converges to near optimal LMMSE solution. The simulation results validate the near optimal performance of proposed algorithm in terms of mean square error (MSE). © 2015 EURASIP.
Wilhelm, Matthias; Schmitt, Jens B
2010-01-01
Key management in wireless sensor networks faces several new challenges. The scale, resource limitations, and new threats such as node capture necessitate the use of an on-line key generation by the nodes themselves. However, the cost of such schemes is high since their secrecy is based on computational complexity. Recently, several research contributions justified that the wireless channel itself can be used to generate information-theoretic secure keys. By exchanging sampling messages during movement, a bit string can be derived that is only known to the involved entities. Yet, movement is not the only possibility to generate randomness. The channel response is also strongly dependent on the frequency of the transmitted signal. In our work, we introduce a protocol for key generation based on the frequency-selectivity of channel fading. The practical advantage of this approach is that we do not require node movement. Thus, the frequent case of a sensor network with static motes is supported. Furthermore, the...
Novel differential unitary space-time modulation schemes for fast fading channels
Institute of Scientific and Technical Information of China (English)
Tian Jifeng; Jiang Haining; Song Wentao; Luo Hanwen
2006-01-01
Differential unitary space-time modulation (DUSTM), which obtains full transmit diversity in slowly flat-fading channels without channel state information, has generated significant interests recently. To combat frequency-selective fading, DUSTM has been applied to each subcarrier of an OFDM system and DUSTM-OFDM system was proposed. Both DUSTM and DUSTM-OFDM, however, are designed for slowly fading channels and suffer performance deterioration in fast fading channels. In this paper, two novel differential unitary space-time modulation schemes are proposed for fast fading channels. For fast flat-fading channels, a sub-matrix interleaved DUSTM (SMI-DUSTM) scheme is proposed, in which matrix-segmentation and sub-matrix based interleaving are introduced into DUSTM system. For fast frequency-selective fading channels, a differential unitary space-frequency modulation (DUSFM) scheme is proposed, in which existing unitary space-time codes are employed across transmit antennas and OFDM subcarriers simultaneously and differential modulation is performed between two adjacent OFDM blocks. Compared with DUSTM and DUSTM-OFDM schemes, SMI-DUSTM and DUSFM-OFDM are more robust to fast channel fading with low decoding complexity, which is demonstrated by performance analysis and simulation results.
Fade margin calculation for channels impaired by Rician fading
Davarian, F.
1985-01-01
Excess path loss due to multipath severely restricts the performance of power limited mobile networks such as those using satellite-aided links. To reduce multipath related losses, the higher elevation angle of the spacecraft can be exploited by utilizing mobile antennas which reduce the strength of the multipath reflections in favor of the line-of-sight signal. The presence of a strong and stable path in a fading link will change the envelope statistics of the received waveform from Rayleigh to a more favorable Rician distribution. It is determined that the excess path loss, or fade margin, of a Rician channel when coherent detection of binary phase shift keying (BPSK) or quaternary phase shift keying (QPSK) signals is considered. The results are presented parametrically such that they can be applied to a wide range of propagation characteristics from heavy fading to nonfading situations. Furthermore, similar results are also given for the case where only limited coverage is provided.
Performance of Multicarrier CDMA Rake System over Rayleigh Fading Channel
Institute of Scientific and Technical Information of China (English)
SONG Li-xin; HUANG Tian-shu; DING Yao-ming
2005-01-01
Based on the theory of multicarrier (MC) technique and the Rake receiver, a multicarrier DSCDMA Rake system is proposed, where a data sequence multiplied by a spreading sequence modulates multiple carriers. The receiver provides a Rake for each subcarrier, and the outputs of the Rakes are combined by a maximal-ratio combiner. The average probability of error of the system is derived from an uncorrelated subcarrier and frequency-selective fading channel model. The system performances are evaluated over Rayleigh fading channel with an exponential multipath intensity profile(MIP) and with a rectangular MIP, respectively,when multipath interference is present. It is found that this kind of model has larger superiority in an exponential MIP than in a rectangular MIP.
Sensitivity of Noncoherent WSSUS Fading Channel Capacity
Durisi, Giuseppe; Bölcskei, Helmut
2011-01-01
The noncoherent capacity of stationary discrete-time fading channels is known to be very sensitive to the fine details of the channel model. More specifically, the measure of the support of the fading-process power spectral density (PSD) determines if noncoherent capacity grows logarithmically in SNR or slower than logarithmically. Such a result is unsatisfactory from an engineering point of view, as the support of the PSD cannot be determined through measurements. The aim of this paper is to assess whether, for general continuous-time fading channels, this sensitivity has a noticeable impact on capacity at SNR values of practical interest. To this end, we consider the general class of band-limited continuous-time Rayleigh-fading channels that satisfy the wide-sense stationary uncorrelated-scattering (WSSUS) assumption and are, in addition, underspread. We show that, for all SNR values of practical interest, the noncoherent capacity of every channel in this class is close to the capacity of an AWGN channel wi...
Secrecy Capacity over Correlated Ergodic Fading Channel
Jeon, Hyoungsuk; Kim, Minki; Lee, Hyuckjae; Ha, Jeongseok
2008-01-01
We investigate the secrecy capacity of an ergodic fading wiretap channel in which the main channel is correlated with the eavesdropper channel. In this study, the full Channel State Information (CSI) is assumed, and thus the transmitter knows the channel gains of the legitimate receiver and the eavesdropper. By analyzing the resulting secrecy capacity we quantify the loss of the secrecy capacity due to the correlation. In addition, we study the asymptotic behavior of the secrecy capacity as Signal-to-Noise Ratio (SNR) tends to infinity. The capacity of an ordinary fading channel logarithmically increases with SNR. On the contrary, the secrecy capacity converges into a limit which can be an upper bound on the secrecy capacity over the fading wiretap channel. We find a closed form of the upper bound for the correlated Rayleigh wiretap channel which also includes the independent case as a special one. Our work shows that the upper bound is determined by only two channel parameters; the correlation coefficient an...
CHANNEL ESTIMATION FOR ITERATIVE DECODING OVER FADING CHANNELS
Institute of Scientific and Technical Information of China (English)
K. H. Sayhood; Wu Lenan
2002-01-01
A method of coherent detection and channel estimation for punctured convolutional coded binary Quadrature Amplitude Modulation (QAM) signals transmitted over a frequency-flat Rayleigh fading channels used for a digital radio broadcasting transmission is presented. Some known symbols are inserted in the encoded data stream to enhance the channel estimation process.The pilot symbols are used to replace the existing parity symbols so no bandwidth expansion is required. An iterative algorithm that uses decoding information as well as the information contained in the known symbols is used to improve the channel parameter estimate. The scheme complexity grows exponentially with the channel estimation filter length. The performance of the system is compared for a normalized fading rate with both perfect coherent detection (corresponding to a perfect knowledge of the fading process and noise variance) and differential detection of Differential Amplitude Phase Shift Keying (DAPSK). The tradeoff between simplicity of implementation and bit-error-rate performance of different techniques is also compared.
Diversity Techniques for Single-Carrier Packet Retransmissions over Frequency-Selective Channels
Directory of Open Access Journals (Sweden)
Inbar Fijalkow
2009-01-01
Full Text Available In data packet communication systems over multipath frequency-selective channels, hybrid automatic repeat request (HARQ protocols are usually used in order to ensure data reliability. For single-carrier packet transmission in slow fading environment, an identical retransmission of the same packet, due to a decoding failure, does not fully exploit the available time diversity in retransmission-based HARQ protocols. In this paper, we compare two transmit diversity techniques, namely, cyclic frequency-shift diversity and bit-interleaving diversity. Both techniques can be integrated in the HARQ scheme in order to improve the performance of the joint detector. Their performance in terms of pairwise error probability is investigated using maximum likelihood detection and decoding. The impact of the channel memory and the modulation order on the performance gain is emphasized. In practice, we use low complexity linear filter-based equalization which can be efficiently implemented in the frequency domain. The use of iterative equalization and decoding is also considered. The performance gain in terms of frame error rate and data throughput is evaluated by numerical simulations.
Secrecy Capacity Region of Fading Broadcast Channels
Liang, Yingbin; Shamai, Shlomo
2007-01-01
The fading broadcast channel with confidential messages (BCC) is investigated, where a source node has common information for two receivers (receivers 1 and 2), and has confidential information intended only for receiver 1. The confidential information needs to be kept as secret as possible from receiver 2. The channel state information (CSI) is assumed to be known at both the transmitter and the receivers. The secrecy capacity region is first established for the parallel Gaussian BCC, and the optimal source power allocations that achieve the boundary of the secrecy capacity region are derived. In particular, the secrecy capacity region is established for the Gaussian case of the Csiszar-Korner BCC model. The secrecy capacity results are then applied to give the ergodic secrecy capacity region for the fading BCC.
Rateless Coding for MIMO Block Fading Channels
Fan, Yijia; Erkip, Elza; Poor, H Vincent
2008-01-01
In this paper the performance limits and design principles of rateless codes over fading channels are studied. The diversity-multiplexing tradeoff (DMT) is used to analyze the system performance for all possible transmission rates. It is revealed from the analysis that the design of such rateless codes follows the design principle of approximately universal codes for parallel multiple-input multiple-output (MIMO) channels, in which each sub-channel is a MIMO channel. More specifically, it is shown that for a single-input single-output (SISO) channel, the previously developed permutation codes of unit length for parallel channels having rate LR can be transformed directly into rateless codes of length L having multiple rate levels (R, 2R, . . ., LR), to achieve the DMT performance limit.
Secrecy Outage Capacity of Fading Channels
Gungor, Onur; Koksal, C Emre; Gamal, Hesham El; Shroff, Ness B
2011-01-01
This paper considers point to point secure communication over flat fading channels under an outage constraint. More specifically, we extend the definition of outage capacity to account for the secrecy constraint and obtain sharp characterizations of the corresponding fundamental limits under two different assumptions on the transmitter CSI (Channel state information). First, we find the outage secrecy capacity assuming that the transmitter has perfect knowledge of the legitimate and eavesdropper channel gains. In this scenario, the capacity achieving scheme relies on opportunistically exchanging private keys between the legitimate nodes. These keys are stored in a key buffer and later used to secure delay sensitive data using the Vernam's one time pad technique. We then extend our results to the more practical scenario where the transmitter is assumed to know only the legitimate channel gain. Here, our achievability arguments rely on privacy amplification techniques to generate secret key bits. In the two cas...
A Reliability Study of RFID Technology in a Fading Channel
2007-06-01
systems. Bit and tag error probabilities are computed for various OOK and M-CSK modulation schemes in a varying Nakagami - m fading channel, and the best...performing schemes are identified for future employment. 15. NUMBER OF PAGES 69 14. SUBJECT TERMS RFID, Fading Channel, Nakagami , On-off...and tag error probabilities are computed for various OOK and M-CSK modulation schemes in a varying Nakagami - m fading channel, and the best performing
Directory of Open Access Journals (Sweden)
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.
CHANNEL ESTIMATION FOR ITERATIVE DECODING OVER FADING CHANNELS
Institute of Scientific and Technical Information of China (English)
K.H.Sayhood; WuLenan
2002-01-01
A method of coherent detection and channel estimation for punctured convolutional coded binary Quadrature Amplitude Modulation (QAM) signals transmitted over a frequency-flat Rayleigh fading channels used for a digital radio broadcasting transmission is presented.Some known symbols are inserted in the encoded data stream to enhance the channel estimation process.The puilot symbols are used to replace the existing parity symbols so no bandwidth expansion is required.An iterative algorithm that uses decoding information as well as the information contained in the known symbols is used to improve the channel parameter estimate.The scheme complexity grows exponentially with the channel estimation filter length,The performance of the system is compared for a normalized fading rate with both perfect coherent detection(Corresponding to a perfect knowledge of the fading process and noise variance)and differential detection of Differential Amplitude Phase Shift Keying (DAPSK).The tradeoff between simplicity of implementation and bit-error-rate performance of different techniques is also compared.
Upper Capacity Bounds of MIMO Wireless Systems Through Fading Channels
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Rachna Mahey
2015-01-01
Full Text Available This paper investigates the upper capacity bounds of MIMO systems with correlation and antenna selection techniques in general fading environments. With Antenna Selection techniques, the increased hardware complexity due to multiple antennas and large number of RF chains can be reduced to a substantial amount, retaining the diversity benefits of MIMO systems. The channel Correlation also affects the capacity of MIMO fading channels. Hence, to evaluate the upper bounds of capacity through fading channels, performance of MIMO systems is exemplified under Nakagami-m and Rayleigh fading channels while considering that the channel characteristics are known at a transmitter. The obtained results give an assessment to the better understanding to the effect of antenna selection and correlation on the capacity of MIMO channels, and how they can be used in different fading environments.
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.
Zhou, Liang; Shimizu, Masahiko
In this paper, we study low complexity transceiver for double space time transmit diversity (DSTTD) and orthogonal frequency division multiplexing (OFDM) system with antenna shuffling. Firstly, we propose a novel antenna shuffling method based on the criterion of minimizing the condition number of channel correlation matrix. The condition number is an indicator about the quality of the channel. By selecting the minimum of condition number which has better channel quality, consequently, a linear detector with respect to this new channel may achieve better performance results. A low complexity variant of the condition number calculation is also proposed, and it is shown that this criterion can be reduced to the minimum mean square error (MMSE) based criterion. Furthermore, the weighted soft decision Viterbi decoding is applied to mitigate noise enhancement inherent to zero forcing (ZF) and MMSE linear receivers and improve error rate performance. Next, we propose an algorithm to reduce the amount of feedback by exploiting the fact that the channel frequency responses across OFDM subcarriers are correlated. In the proposed algorithm, subcarriers are clustered in blocks, which are allocated the same shuffling pattern with the largest number of the shuffling patterns in the cluster. This way, the signaling overhead can be reduced in comparison with each subcarrier based feedback. Extensive simulations show that the proposed techniques for DSTTD-OFDM system outperform other existing techniques under both uncorrelated and highly spatial correlated frequency selective MIMO fading channels.
Ahmad Ansari, Ejaz; Rajatheva, Nandana
Although the topic of multiple-input multiple-output (MIMO) based orthogonal frequency division multiplexing (OFDM) over different fading channels is well investigated, its closed form symbol error rate (SER) expressions and performance results employing orthogonal space time block codes (OSTBCs) over uncorrelated frequency-selective Nakagami-m fading channels are still not available. The closed form expressions are extremely useful for evaluating system's performance without carrying out time consuming simulations. Similarly, the performance results are also quite beneficial for determining the system's performance in the sense that many practical wireless standards extensively employ MIMO-OFDM systems in conjunction with M-ary quadrature amplitude modulation (M-QAM) constellation. This paper thus, derives exact closed form expressions for the SER of M-ary Gray-coded one and two dimensional constellations when an OSTBC is employed and Nt transmit antennas are selected for transmission over frequency-selective Nakagami-m fading channels. For this purpose, first an exact closed-form of average SER expression of OSTBC based MIMO-OFDM system for M-ary phase shift keying (M-PSK) using traditional probability density function (PDF) approach is derived. We then compute exact closed form average SER expressions for M-ary pulse amplitude modulation (M-PAM) and M-QAM schemes by utilizing this generalized result. These expressions are valid over both frequency-flat and frequency-selective Nakagami-m fading MIMO channels and can easily be evaluated without using any numerical integration methods. We also show that average SER of MIMO-OFDM system using OSTBC in case of frequency-selective Rayleigh fading channels remains independent to the number of taps, L of that fading channel and the performance of the same system for two-tap un-correlated Rayleigh and Nakagami-m fading channels is better than that of the correlated one. Moreover, Monte Carlo simulation of MIMO-OFDM system
Directory of Open Access Journals (Sweden)
Chen Yu-Fan
2006-01-01
Full Text Available An adaptive minimum mean-square error (MMSE array receiver based on the fuzzy-logic recursive least-squares (RLS algorithm is developed for asynchronous DS-CDMA interference suppression in the presence of frequency-selective multipath fading. This receiver employs a fuzzy-logic control mechanism to perform the nonlinear mapping of the squared error and squared error variation, denoted by ( , , into a forgetting factor . For the real-time applicability, a computationally efficient version of the proposed receiver is derived based on the least-mean-square (LMS algorithm using the fuzzy-inference-controlled step-size . This receiver is capable of providing both fast convergence/tracking capability as well as small steady-state misadjustment as compared with conventional LMS- and RLS-based MMSE DS-CDMA receivers. Simulations show that the fuzzy-logic LMS and RLS algorithms outperform, respectively, other variable step-size LMS (VSS-LMS and variable forgetting factor RLS (VFF-RLS algorithms at least 3 dB and 1.5 dB in bit-error-rate (BER for multipath fading channels.
Performance Evaluation of DWT based Multicarrier Systems over Frequency Selective Channels
Suganya.M; Ramanathan R
2015-01-01
In this work, the performance of DWT based OFDM is studied and compared it with conventional FFT based OFDM over frequency selective channels in different test environments. The Bit Error Rate (BER) estimation is done to evaluate the performance of both the systems. In DWT based OFDM, different wavelet families such as haar, daubechies, coiflet and biorthogonal were used with different levels of decomposition. The simulation results show that in all channels, DWT based OFDM requires less SNR ...
Optimum Multiuser Detector for Multipath Slow Fading Asynchronous CDMA Channels
Institute of Scientific and Technical Information of China (English)
WangZhaocheng; YangZhixing; 等
1995-01-01
A structure of optimum multiuser detector for asynchronous CDMA in multipath slow fading channels is derived and the significant performance gain over the conventional RAKE receiv-er is shown by simulation.
Institute of Scientific and Technical Information of China (English)
WANGDonghua; ZHOUYuanhua; SUPengcheng; GEJingyan
2004-01-01
A robust video transmission scheme based on space-time coded Orthogonal frequency division multiplexing (OFDM) over broadband wireless fading channels is proposed. Considering the MPEG-4 standardized data partitioning method doesn't take care of important high frequency information of IVOP and Direct current (DC) coefficients of PVOP and has poor error concealment effects for lost texture data with abundant details, a more robust data partitioning method called NewDP is designed after significances of some MPEG-4 Simple profile (SP) bitstreams' syntactical elements are carefully analyzed and tested. Then, the UEP method based on Systemic ratecompatible punctured convolutional channel codes (SRCPC) is applied to protect layered video bitstreams with different priorities. For fighting with fading and noise in wireless channels, Space-time block codes (STBC) combined with OFDM are applied in our scheme. STBC can provide diversity gains by multiple transmit antennae while OFDM can effectively alleviate frequency-selective fading effects, making our scheme more robust as well as higher transmitting rates. Simulation results show that our scheme can get better video transmission effects over broadband wireless fading channels than the schemes using the Equal error protection method (EEP) or based on the MPEG-4 standardized data partitioning methods.
On Successive Refinement of Diversity for Fading ISI Channels
Dusad, S
2007-01-01
Rate and diversity impose a fundamental tradeoff in communications. This tradeoff was investigated for Intersymbol Interference (ISI) channels in [4]. A different point of view was explored in [1] where high-rate codes were designed so that they have a high-diversity code embedded within them. Such diversity embedded codes were investigated for flat fading channels and in this paper we explore its application to ISI channels. In particular, we investigate the rate tuples achievable for diversity embedded codes for scalar ISI channels through particular coding strategies. The main result of this paper is that the diversity multiplexing tradeoff for fading ISI channels is indeed successively refinable. This implies that for fading single input single output (SISO) ISI channels one can embed a high diversity code within a high rate code without any performance loss (asymptotically). This is related to a deterministic structural observation about the asymptotic behavior of frequency response of channel with respe...
Secret Sharing over Fast-Fading MIMO Wiretap Channels
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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.
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.
Turbo Detection in Rayleigh flat fading channel with unknown statistics
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Paul Fortier
2010-11-01
Full Text Available The turbo detection of turbo coded symbols over correlated Rayleigh flat fading channels generatedaccording to Jakes’ model is considered in this paper. We propose a method to estimate the channelsignal-to-noise ratio (SNR and the maximum Doppler frequency. These statistics are required bythe linear minimum mean squared error (LMMSE channel estimator. To improve the system convergence,we redefine the channel reliability factor by taking into account the channel estimationerror statistics. Simulation results for rate 1=3 turbo code and two different normalized fading ratesshow that the use of the new reliability factor greatly improves the performance. The improvementis more substantial when channel statistics are unknown.
Performance Analysis of STTC MIMO-OFDM Systems over Rayleigh Fading Channels
Institute of Scientific and Technical Information of China (English)
BAIWei; HEChen; JIANGLingge
2003-01-01
Multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) is one of the most promising scheme for achieving high data rate and large system capacity over wireless networks. This paper addresses the error performance analysis of the Space-time trellis code (STTC) MIMO-OFDM systems over quasistatic, frequency selective Rayleigh fading channels. Using the Chernoff bound combined with transfer function bounding technique, we provide a new analytical method. To quantify the upper bound of the error performance, we derive the probability density function (pdf) of the frequency domain fading channel and make a novel approximation to the Euclidean distance. Monte Carlo simulation results indicate that the derived upper bounds are quite accurate in a broad range of Signal-to-noise ratio (SNR).
BER Performance for Downlink MC-CDMA Systems over Rician Fading Channels
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Vimal K. Dubey
2005-04-01
Full Text Available We consider downlink multicarrier code-division multiple-access (MC-CDMA systems using binary phase-shift keying (BPSK modulation scheme and maximal ratio combining (MRC in frequency-selective Rician fading channels. A time-domain method to obtain bit error rate (BER by calculating moment generating function (MGF of the decision variable for a tapped-delay-line channel model is proposed. This method does not require any assumption regarding the statistical or spectral distribution of multiple access interference (MAI, and it is also not necessary to assume that the fading encountered by the subcarriers is independent of each other. The analytical formula is also verified by simulations.
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.
A Survey of Fading Models for Mobile Radio Channel Characterization
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L. D. Arya
2010-02-01
Full Text Available Future 3G and 4G mobile communication systems will be required to support wide range of data rates and quality of service matrix. For the efficient design of data link and transport protocols system designer needs knowledge of the statistical properties of physicallayer. Studies have shown that without proper characterization of the channel, blind application of existing protocols and transmission policy may results in disastrous performance unless proper measures are not being taken. Channel characterization also helps in llocation of resources, selection of transmission policy andprotocols. A feasible measure is to have an accurate and thoroughly reproducible optimum channel model which can mimic the mobile radio channel in diversities of fading error environments. Objective of channel model is to supply proper outputs for designing of upper layer protocol in such a fashion as if it were running on the actualphysical layer. The model should fit very well to the measured data and should easily handle analytically. Various approaches for characterization of fading mobile channels have appeared in iterature over last five decades. This article surveys the fading channel models for proper characterization of the radio channel andprovides approaches to classify the existing channel models. The paper also presents the contribution made by these channel models with their assumptions, suitability, applications, shortcomingsand further improvement issues. In present environment Markov Models are best suited for characterization of the fading radio channel. Inthese models radio channel is presented in terms of fading states and modeled as stochastic process. A proper constructed channel model may be valuable means to enhance the reliability and capacity of future mobile radio channel.
Information-theoretically Secret Key Generation for Fading Wireless Channels
Ye, Chunxuan; Reznik, Alex; Shah, Yogendra; Trappe, Wade; Mandayam, Narayan
2009-01-01
The multipath-rich wireless environment associated with typical wireless usage scenarios is characterized by a fading channel response that is time-varying, location-sensitive, and uniquely shared by a given transmitter-receiver pair. The complexity associated with a richly scattering environment implies that the short-term fading process is inherently hard to predict and best modeled stochastically, with rapid decorrelation properties in space, time and frequency. In this paper, we demonstrate how the channel state between a wireless transmitter and receiver can be used as the basis for building practical secret key generation protocols between two entities. We begin by presenting a scheme based on level crossings of the fading process, which is well-suited for the Rayleigh and Rician fading models associated with a richly scattering environment. Our level crossing algorithm is simple, and incorporates a self-authenticating mechanism to prevent adversarial manipulation of message exchanges during the protoco...
Hardware Emulation of Wireless Communication Fading Channels
2011-01-01
selective fading sim- ulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 2 The datapath of the C 1 2 ISI generator...module. . . . . . . . . . . . . . . . . . 73 3 The datapath of the CM module. . . . . . . . . . . . . . . . . . . . . . . . 74 4 The memory usage...module which finds the matrix square root of CISI . The datapath of the C 1 2 ISI generator is shown in Fig. 3. The q1 and q2 counters range from −Q1 to
Low-Complexity Iterative Receiver for Space-Time Coded Signals over Frequency Selective Channels
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Mohamed Siala
2002-05-01
Full Text Available We propose a low-complexity turbo-detector scheme for frequency selective multiple-input multiple-output channels. The detection part of the receiver is based on a List-type MAP equalizer which is a state-reduction algorithm of the MAP algorithm using per-survivor technique. This alternative achieves a good tradeoff between performance and complexity provided a small amount of the channel is neglected. In order to induce the good performance of this equalizer, we propose to use a whitened matched filter (WMF which leads to a white-noise Ã¢Â€Âœminimum phaseÃ¢Â€Â channel model. Simulation results show that the use of the WMF yields significant improvement, particularly over severe channels. Thanks to the iterative turbo processing (detection and decoding are iterated several times, the performance loss due to the use of the suboptimum List-type equalizer is recovered.
BER Performance Analysis of Rake Receiver in Rayleigh Fading Channel for UMTS environment
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Pravindra Kumar
2010-06-01
Full Text Available The goal for the third generation of mobile communications system is to integrate a wide variety of communication services such as high speed data, video and multimedia traffic as well as voice signals. Under the Universal Mobile Telecommunication System (UMTS environment the Third Generation (3G has many advantages such as highly efficient spectrum utilisation and variable user data rates. In this paper, we present the bit error rate (BER performance analysis of Rake Receiver under UMTS environment with BPSK modulation technique and the convolutional coding at the transmitter and viterbi decoding at the receiver side. The Standard Gaussian Approximation (SGA is used to evaluate the performance of Rake Receiver over a frequency selective Rayleigh fading channel. The data is modulated, encoded, spread and transmitted through a frequency selective Rayleigh fading channel. The transmitted signal is corrupted by multiple access interference, and is further corrupted by AWGNat the receiver. In the receiver, dispreading, decoded and demodulated. Rake Receiver, directive antenna are employed to improve the system performance. We examined the BER performance of Rake Receiver with, varying the number of users, spreading factor, Rake fingers, Interfering Cells, and the value of directivity of antenna at base Station. From the results we have seen that the BER performance of Rake Receiver is affected by varying these parameters and gives useful results.
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
A Simple Capacity Formula for Correlated Diversity Rayleigh Fading Channels
Institute of Scientific and Technical Information of China (English)
CHENG Xing-qing; SU Shu-chun; LI Dao-ben
2004-01-01
Abstract: The system capacity can be considerably increased if we appropriately exploit the randomness of multipath propagation. A simple average capacity formula is derived for correlated diversity Rayleigh fading channels through linear transformation method.Numerical results that illustrate the effect of correlation parameter and diversity order on the diversitycapacity are also presented.
Frequency Offset Influence on MDPSK Signal Reception in Fading Channel
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S. N. Stošović
2013-11-01
Full Text Available The symbol error probability of M-ary differential phase shift keying (MDPSK receiver, in the presence of carrier frequency offset, is analysed in this paper. The paper proposes a novel multiple symbol differential detection (MSDD receiver. The influence of various receiver’s parameters on the error probability is analysed. The theoretical symbol error probability is derived and compared to the Monte-Carlo simulation results, for an AWGN channel. The analysis shows a good agreement between the theoretical and simulation results. The influence of the frequency offset in the Rician fading channel, using Monte-Carlo simulation, is also considered for the same receiver’s parameters as in the AWGN channel. Simulation results show good system performances in the case of Rician fading channel, also.
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.
A simple channel estimator for space-time coded OFDM systems in rapid fading channels
Institute of Scientific and Technical Information of China (English)
单淑伟; 罗汉文; 宋文涛
2004-01-01
A simple channel estimator for space-time coded orthogonal frequency division multiplexing (OFDM) systems in rapid fading channels is proposed. The channels at the training bauds are estimated using the EM (expectation-maximization) algorithm, while the channels at the data bauds are estimated based on the method for modelling the time-varying channel as the linear combination of several time-invariant " Doppler channels". Computer simulations showed that this estimator outperforms the decision-directed tracking in rapid fading channels and that the performance of this method can be improved by iteration.
A simple channel estimator for space-time coded OFDM systems in rapid fading channels
Institute of Scientific and Technical Information of China (English)
SHAN Shu-wei(单淑伟); LUO Han-wen(罗汉文); SONG Wen-tao(宋文涛)
2004-01-01
A simple channel estimator for space-time coded orthogonal frequency division multiplexing (OFDM) systems in rapid fading channels is proposed. The channels at the training bauds are estimated using the EM (expectation-maximization) algorithm, while the channels at the data bauds are estimated based on the method for modelling the time-varying channel as the linear combination of several time-invariant "Doppler channels". Computer simulations showed that this estimator outperforms the decision-directed tracking in rapid fading channels and that the performance of this method can be improved by iteration.
Directory of Open Access Journals (Sweden)
Gelle Guillaume
2004-01-01
Full Text Available This paper deals with optimized channel coding for OFDM transmissions (COFDM over frequency-selective channels using irregular low-density parity-check (LDPC codes. Firstly, we introduce a new characterization of the LDPC code irregularity called irregularity profile. Then, using this parameterization, we derive a new criterion based on the minimization of the transmission bit error probability to design an irregular LDPC code suited to the frequency selectivity of the channel. The optimization of this criterion is done using the Gaussian approximation technique. Simulations illustrate the good performance of our approach for different transmission channels.
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.
A Differential MIMO SC-FDE Transceiver Design over Multipath Fast Fading Channels
Deng, Juinn-Horng; Hwang, Jeng-Kuang
In this paper, we propose a new differential MIMO single-carrier system with frequency-domain equalization (SC-FDE) aided by the insertion of cyclic prefix. This block transmission system not only inherits all the merits of the SISO SC-FDE system, but is also equipped with a differential space-time block coding (DSTBC) such as to combat the fast-changing frequency selective fading channels without the needs to estimate and then compensate the channel effects. Hence, for practical applications, it has the additional merits of decoding simplicity and robustness against high mobility transmission environments. Computer simulations show that the proposed system can provide diversity benefit as the non-differential system does, while greatly reducing the receiver complexity.
Asymptotically Optimal Downlink Scheduling over Markovian Fading Channels
Ouyang, Wenzhuo; Shroff, Ness B
2011-01-01
We consider the scheduling problem in downlink wireless networks with heterogeneous, Markov-modulated, ON/OFF channels. It is well-known that the performance of scheduling over fading channels heavily depends on the accuracy of the available Channel State Information (CSI), which is costly to acquire. Thus, we consider the CSI acquisition via a practical ARQ-based feedback mechanism whereby channel states are revealed at the end of only scheduled users' transmissions. In the assumed presence of temporally-correlated channel evolutions, the desired scheduler must optimally balance the exploitation-exploration trade-off, whereby it schedules transmissions both to exploit those channels with up-to-date CSI and to explore the current state of those with outdated CSI. In earlier works, Whittle's Index Policy had been suggested as a low-complexity and high-performance solution to this problem. However, analyzing its performance in the typical scenario of statistically heterogeneous channel state processes has remai...
Controlling Ion Conductance and Channels to Achieve Synaptic-like Frequency Selectivity
Institute of Scientific and Technical Information of China (English)
Siheng Lu; Fei Zeng; Wenshuai Dong; Ao Liu; Xiaojun Li; Jingting Luo
2015-01-01
Enhancing ion conductance and controlling transport pathway in organic electrolyte could be used to modulate ionic kinetics to handle signals. In a Pt/Poly(3-hexylthiophene-2,5-diyl)/Polyethylene?LiCF3SO3/Pt hetero-junction, the electrolyte layer handled at high temperature showed nano-fiber microstructures accompanied with greatly improved salt solubility. Ions with high mobility were confined in the nano-fibrous channels leading to the semiconducting polymer layer, which is favorable for modulating dynamic doping at the semiconducting polymer/electrolyte interface by pulse frequency. Such a device realized synaptic-like frequency selectivity, i.e., depression at low frequency stimulation but potentiation at high-frequency stimulation.
Spreading Code Assignment Strategies for MIMO-CDMA Systems Operating in Frequency-Selective Channels
Directory of Open Access Journals (Sweden)
Dahmane AdelOmar
2009-01-01
Full Text Available Abstract Code Division Multiple Access (CDMA and multiple input multiple output- (MIMO- CDMA systems suffer from multiple access interference (MAI which limits the spectral efficiency of these systems. By making these systems more power efficient, we can increase the overall spectral efficiency. This can be achieved through the use of improved modulation and coding techniques. Conventional MIMO-CDMA systems use fixed spreading code assignments. By strategically selecting the spreading codes as a function of the data to be transmitted, we can achieve coding gain and introduce additional degrees of freedom in the decision variables at the output of the matched filters. In this paper, we examine the bit error rate performance of parity bit-selected spreading and permutation spreading under different wireless channel conditions. A suboptimal detection technique based on maximum likelihood detection is proposed for these systems operating in frequency selective channels. Simulation results demonstrate that these code assignment techniques provide an improvement in performance in terms of bit error rate (BER while providing increased spectral efficiency compared to the conventional system. Moreover, the proposed strategies are more robust to channel estimation errors as well as spatial correlation.
Signal Classification in Fading Channels Using Cyclic Spectral Analysis
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Eric Like
2009-01-01
Full Text Available Cognitive Radio (CR, a hierarchical Dynamic Spectrum Access (DSA model, has been considered as a strong candidate for future communication systems improving spectrum efficiency utilizing unused spectrum of opportunity. However, to ensure the effectiveness of dynamic spectrum access, accurate signal classification in fading channels at low signal to noise ratio is essential. In this paper, a hierarchical cyclostationary-based classifier is proposed to reliably identify the signal type of a wide range of unknown signals. The proposed system assumes no a priori knowledge of critical signal statistics such as carrier frequency, carrier phase, or symbol rate. The system is designed with a multistage approach to minimize the number of samples required to make a classification decision while simultaneously ensuring the greatest reliability in the current and previous stages. The system performance is demonstrated in a variety of multipath fading channels, where several multiantenna-based combining schemes are implemented to exploit spatial diversity.
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...
Sphere Lower Bound for Rotated Lattice Constellations in Fading Channels
Fabregas, Albert Guillen i
2007-01-01
We study the error probability performance of rotated lattice constellations in frequency-flat Nakagami-$m$ block-fading channels. In particular, we use the sphere lower bound on the underlying infinite lattice as a performance benchmark. We show that the sphere lower bound has full diversity. We observe that optimally rotated lattices with largest known minimum product distance perform very close to the lower bound, while the ensemble of random rotations is shown to lack diversity and perform far from it.
A New Sequential Detection Based on Hopfield Neural Network in Frequency Selective Fading Channels
Institute of Scientific and Technical Information of China (English)
WengJianfeng; BiGuangguo
1995-01-01
In this paper,a new Hopfield Neural Network(HNN) detector is described to estimate the transmitted sequences from the received signals in mobile communications and order to avoid the convergence of HNN in local minima,a new decreasing step algorithm(DSA) is presented to search the optimum sequence quickly on the basis of the traditional Simulated Annealing (SA)al-gorithm.Computer simulation results show that the new HNN detector provides almost the same performance as that of the Viterbi detector with less calculations. Moreover,compared with Viterbi detector ,direct hardware implementation for HNN detector is feasible and convenient es-pecially for the long constraint length convolutional code.
Blind CP-OFDM and ZP-OFDM Parameter Estimation in Frequency Selective Channels
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Vincent Le Nir
2009-01-01
Full Text Available A cognitive radio system needs accurate knowledge of the radio spectrum it operates in. Blind modulation recognition techniques have been proposed to discriminate between single-carrier and multicarrier modulations and to estimate their parameters. Some powerful techniques use autocorrelation- and cyclic autocorrelation-based features of the transmitted signal applying to OFDM signals using a Cyclic Prefix time guard interval (CP-OFDM. In this paper, we propose a blind parameter estimation technique based on a power autocorrelation feature applying to OFDM signals using a Zero Padding time guard interval (ZP-OFDM which in particular excludes the use of the autocorrelation- and cyclic autocorrelation-based techniques. The proposed technique leads to an efficient estimation of the symbol duration and zero padding duration in frequency selective channels, and is insensitive to receiver phase and frequency offsets. Simulation results are given for WiMAX and WiMedia signals using realistic Stanford University Interim (SUI and Ultra-Wideband (UWB IEEE 802.15.4a channel models, respectively.
Streaming Transmitter over Block-Fading Channels with Delay Constraint
Cocco, Giuseppe; Ibars, Christian
2012-01-01
Data streaming transmission, in which the data arrives at the transmitter gradually over time is studied. It is assumed that the transmitter receives a new message at each channel block at a constant rate which is fixed by an underlying application, and tries to broadcast these messages to users within a certain deadline. The channels are assumed to be block fading and independent over blocks and users. The performance measure is the average total rate of received information at the users within the transmission deadline. Three different encoding schemes are proposed and compared with an informed transmitter upper bound in terms of the average total rate for a set of users with varying channel qualities. Analytical upper bounds on the average total rate are derived for all the proposed schemes. It is shown that no single transmission strategy dominates the others at all channel settings, and the best transmitter streaming scheme depends on the distribution of the average channel conditions over the users.
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Tamer A. Kadous
2003-01-01
Full Text Available The goal of this paper is to compare the performance of the linear minimum mean square error (MMSE detector for a class of code division multiple access (CDMA systems in time and frequency selective channels. Specifically, we consider direct sequence (DS-CDMA, multicarrier (MC-CDMA, and the MC-DS-CDMA systems. Two key tools are used in our development. First, a general time-frequency framework that includes the different CDMA systems as special cases. Second, the duality between time and frequency domains that is used to derive equivalences between the different CDMA systems operating over purely frequency selective and purely time selective channels. We then combine the insights obtained from these special cases to assess the performance of CDMA systems over time and frequency selective channels. We provide sufficient conditions for the codes employed by the CDMA systems for the equivalences to hold. Numerical results are presented to illustrate the results.
Simplified 3D Fading Channels Adopted in MIMO Beamforming Schemes
Institute of Scientific and Technical Information of China (English)
Joy Iong-Zong Chen; Bo Huei Lee
2015-01-01
A simplified three-dimension (3D) fading channel model deployed in a multi-input multi-output (MIMO) beamforming system is explored in this article. Both angle of arrival (AoA) and angle of departure (AoD) which impact the overall system performance are examined. The numerical results are given for validating the accuracy of the theoretical derived formulas. Furthermore, the performances of the model with different number of transmitters and receivers are studied and compared. The increment in AoA parameters definitely generates the impact of the system performance when the consideration of simplified 3D channels.
Block-Fading Channels with Delayed CSIT at Finite Blocklength
DEFF Research Database (Denmark)
Trillingsgaard, Kasper Fløe; Popovski, Petar
2014-01-01
In many wireless systems, the channel state information at the transmitter (CSIT) can not be learned until after a transmission has taken place and is thereby outdated. In this paper, we study the benefits of delayed CSIT on a block-fading channel at finite blocklength. First, the achievable rates...... of a family of codes that allows the number of codewords to expand during transmission, based on delayed CSIT, are characterized. A fixed-length and a variable-length characterization of the rates are provided using the dependency testing bound and the variable-length setting introduced by Polyanskiy et al...
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.
Performance Analysis of LDPC on Rician Fading Channels
Institute of Scientific and Technical Information of China (English)
LIN Jia-ru; WU Wei-ling
2006-01-01
This paper analyzes and simulates the performance of irregular low-density parity check (LDPC) codes on Rician fading channels.The authors also modified the brief propagation decoding algorithm,proved the symmetry and showed the stability conditions of the channels,and calculated the Shannon limits on Rician channels in this paper.By using Visual C++ programming to simulate the performance,the result indicates that when code length N =3,072 and code rate R = 1/3,the difference with the Shannon limit is about 2 dB.Therefore,the performance of LDPC is also very effective on all kinds of channels,including the Rician kind.
EVALUATION OF MIMO SYSTEM CAPACITY OVER RAYLEIGH FADING CHANNEL
Directory of Open Access Journals (Sweden)
Emad. Mohamed
2015-06-01
Full Text Available High transmission data rate, spectral efficiency and reliability are essential for future wireless communications systems. MIMO (multi-input multi-output diversity technique is a band width efficient system achieving high data transmission which eventually establishing a high capacity communication system. Without needing to increase the transmitted power or the channel bandwidth, gain in capacity can be considerably improved by varying the number of antennas on both sides. Correlated and uncorrelated channels MIMO system was considered in this paper for different number of antennas and different SNR over Rayleigh fading channel. At the transmitter both CSI(channel state information technique and Water filling power allocation principle was also considered in this paper
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.
Rottenberg, Francois; Mestre, Xavier; Horlin, Francois; Louveaux, Jerome
2017-02-01
The design of linear precoders or decoders for multiuser (MU) multiple-input multiple-output (MIMO) filterbank multicarrier (FBMC) modulations in the case of strong channel frequency selectivity is presented. The users and the base station (BS) communicate using space division multiple access (SDMA). The low complexity proposed solution is based on a single tap per-subcarrier precoding/decoding matrix at the base station (BS) in the downlink/uplink. As opposed to classical approaches that assume flat channel frequency selectivity at the subcarrier level, the BS does not make this assumption and takes into account the distortion caused by channel frequency selectivity. The expression of the FBMC asymptotic mean squared error (MSE) in the case of strong channel selectivity derived in earlier works is developed and extended. The linear precoders and decoders are found by optimizing the MSE formula under two design criteria, namely zero forcing (ZF) or minimum mean squared error (MMSE). Finally, simulation results demonstrate the performance of the optimized design. As long as the number of BS antennas is larger than the number of users, it is shown that those extra degrees of freedom can be used to compensate for the channel frequency selectivity.
DVB-T Digital Terrestrial Television Transmission over Fading Channels
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R. Stukavec
2008-09-01
Full Text Available The paper deals with the transmission of the digital television signal according to the DVB-T standard in SFN network over fading channels for the fixed reception. The laboratory transmission system for the real broadcasting based on R&S RF test and measuring equipments is presented including the transmission parameters setup. The results of broadcasting over Gausian, Ricean and Rayleigh channels and results of the echo impairments are presented and discussed with the theory and simulation results. The BER before and after Viterbi decoding and according to MER equal to S/N ratio in the channel from the constellation diagram were compared in all transmission experiments. Additional picture quality evaluation is presented using DVQL-W metric that monitors blockiness structures in MPEG-2 compressed pictures and gives notice of known "cliff-off" effect.
Discrete Multiwavelet Critical-Sampling Transform-Based OFDM System over Rayleigh Fading Channels
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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.
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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
Error Resilient Image Transmission over Wireless Fading Channels
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M Padmaja,
2010-05-01
Full Text Available Nowadays transferring images and video over wireless channels is becoming more use of the medium. However, a wireless medium is not very reliable in the way that it adds unwanted components and noise to the wireless transmission. So there may be a loss of data. Due to this possible loss of data without the capability of resending a correct version we need a system to protect and correct such losses. The transmission of images over wireless channels is examined using reorganization of the compressed images into error-resilient, product-coded streams. The product-code consists of Turbo-codes or Reed–Solomon codes which are optimized using an iterative process. The wireless channel used for the testing phase is a Rayleigh Fading channel with Additive White Gaussian Noise (AWGN added as a noisecomponent. In this paper we propose protection techniques for image transmission and compare the performance of various protection methods for all JPEG standards. The proposed image standard model was found to perform very well in protecting the images against quality degradation during transmission over wireless channels. The strength of the protection plays a large part in the protection of the image and should be chosen to suit the particular channel in use. Thedefault protection also provides very strong protection for the user who does not wish to choose their own setting.
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.
Optimal Packet Scheduling on an Energy Harvesting Fading Channel
Ozcelik, F Mehmet; Uysal-Biyikoglu, Elif
2012-01-01
An offline transmission completion time minimization problem for an energy harvesting transmitter is considered. Specifically, optimal power and rate allocation for data packets arriving at arbitrary but known instances is studied. Communication takes place under a fading channel and transmitter is restricted with a limited energy storage capability. An optimal policy takes into account the channel state as well as the state of energy and data buffers. Moreover, the solution needs to strike a tradeoff between energy efficiency and delay. By exhibiting an equivalent convex problem, the unique optimal scheduling solution is obtained through an iterative convex optimization technique, sequential unconstrained minimization. The optimal solution under finite and infinite energy storage is examined on problem instances.
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.
Asyhari, A Taufiq; Fàbregas, Albert Guillén i
2011-01-01
We study a noncoherent multiple-input multiple-output (MIMO) fading multiple-access channel (MAC), where the transmitters and the receiver are aware of the statistics of the fading, but not of its realisation. We analyse the rate region that is achievable with nearest neighbour decoding and pilot-assisted channel estimation and determine the corresponding pre-log region, which is defined as the limiting ratio of the rate region to the logarithm of the SNR as the SNR tends to infinity.
Institute of Scientific and Technical Information of China (English)
Xiao Hailin; Nie Zaiping; Yang Shiwen
2007-01-01
The novel closed-form expressions for the average channel capacity of dual selection diversity is presented, as well as, the bit-error rate (BER) of several coherent and noncoherent digital modulation schemes in the correlated Weibull fading channels with nonidentical statistics.The results are expressed in terms of Meijer's Gfunction, which can be easily evaluated numerically.The simulation results are presented to validate the proposed theoretical analysis and to examine the effects of the fading severity on the concerned quantities.
On the Channel Capacity of Multiantenna Systems with Nakagami Fading
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Kaiser Thomas
2006-01-01
Full Text Available We discuss the channel capacity of multiantenna systems with the Nakagami fading channel. Analytic expressions for the ergodic channel capacity or its lower bound are given for SISO, SIMO, and MISO cases. Formulae for the outage probability of the capacity are presented. It is shown that the channel capacity could be increased logarithmically with the number of receive antennas for SIMO case; while employing 3–5 transmit antennas (irrespective of all other parameters considered herein can approach the best advantage of the multiple transmit antenna systems as far as channel capacity is concerned for MISO case. We have shown that for a given SNR, the outage probability decreases considerably with the number of receive antennas for SIMO case, while for MISO case, the upper bound of the outage probability decreases with the number of transmit antennas when the transmission rate is lower than some value, but increases instead when the transmission rate is higher than another value. A critical transmission rate is identified.
On Channel Estimation for OFDM/TDM Using MMSE-FDE in a Fast Fading Channel
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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.
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.
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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.
Fast DOA estimation using wavelet denoising on MIMO fading channel
Meenakshi, A V; Kayalvizhi, R; Asha, S
2011-01-01
This paper presents a tool for the analysis, and simulation of direction-of-arrival (DOA) estimation in wireless mobile communication systems over the fading channel. It reviews two methods of Direction of arrival (DOA) estimation algorithm. The standard Multiple Signal Classification (MUSIC) can be obtained from the subspace based methods. In improved MUSIC procedure called Cyclic MUSIC, it can automatically classify the signals as desired and undesired based on the known spectral correlation property and estimate only the desired signal's DOA. In this paper, the DOA estimation algorithm using the de-noising pre-processing based on time-frequency conversion analysis was proposed, and the performances were analyzed. This is focused on the improvement of DOA estimation at a lower SNR and interference environment. This paper provides a fairly complete image of the performance and statistical efficiency of each of above two methods with QPSK signal.
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Bui Francis Minhthang
2006-01-01
Full Text Available Methods for providing good spectral efficiency, without disadvantaging the delivered quality of service (QoS, in time-varying fading channels are presented. The key idea is to allocate system resources according to the encountered channel. Two approaches are examined: variable-size burst construction, and adaptive modulation. The first approach adapts the burst size according to the channel rate of change. In doing so, the available training symbols are efficiently utilized. The second adaptation approach tracks the operating channel quality, so that the most efficient modulation mode can be invoked while guaranteeing a target QoS. It is shown that these two methods can be effectively combined in a common framework for improving system efficiency, while guaranteeing good QoS. The proposed framework is especially applicable to multistate channels, in which at least one state can be considered sufficiently slowly varying. For such environments, the obtained simulation results demonstrate improved system performance and spectral efficiency.
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.
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.
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.
Wireless Fading Channel Models: From Classical to Stochastic Differential Equations
Energy Technology Data Exchange (ETDEWEB)
Olama, Mohammed M [ORNL; Djouadi, Seddik M [ORNL; Charalambous, Prof. Charalambos [University of Cyprus
2010-01-01
The wireless communications channel constitutes the basic physical link between the transmitter and the receiver antennas. Its modeling has been and continues to be a tantalizing issue, while being one of the most fundamental components based on which transmitters and receivers are designed and optimized. The ultimate performance limits of any communication system are determined by the channel it operates in. Realistic channel models are thus of utmost importance for system design and testing. In addition to exponential power path-loss, wireless channels suffer from stochastic short term fading (STF) due to multipath, and stochastic long term fading (LTF) due to shadowing depending on the geographical area. STF corresponds to severe signal envelope fluctuations, and occurs in densely built-up areas filled with lots of objects like buildings, vehicles, etc. On the other hand, LTF corresponds to less severe mean signal envelope fluctuations, and occurs in sparsely populated or suburban areas. In general, LTF and STF are considered as superimposed and may be treated separately. Ossanna was the pioneer to characterize the statistical properties of the signal received by a mobile user, in terms of interference of incident and reflected waves. His model was better suited for describing fading occurring mainly in suburban areas (LTF environments). It is described by the average power loss due to distance and power loss due to reflection of signals from surfaces, which when measured in dB's give rise to normal distributions, and this implies that the channel attenuation coefficient is log-normally distributed. Furthermore, in mobile communications, the LTF channel models are also characterized by their special correlation characteristics which have been reported. Clarke introduced the first comprehensive scattering model describing STF occurring mainly in urban areas. An easy way to simulate Clarke's model using a computer simulation is described. This model was
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.
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.
Tuzlukov, Vyacheslav
2011-06-01
In this paper, we consider the problem of M-ary signal detection based on the generalized approach to signal processing (GASP) in noise over a single-input multiple-output (SIMO) channel affected by frequency-dispersive Rayleigh distributed fading and corrupted by additive non-Gaussian noise modeled as spherically invariant random process. We derive both the optimum generalized detector (GD) structure based on GASP and a suboptimal reduced-complexity GD applying the low energy coherence approach jointly with the GASP in noise. Both GD structures are independent of the actual noise statistics. We also carry out a performance analysis of both GDs and compare with the conventional receivers. The performance analysis is carried out with reference to the case that the channel is affected by a frequency-selective fading and for a binary frequency-shift keying (BFSK) signaling format. The results obtained through both a Chernoff-bounding technique and Monte Carlo simulations reveal that the adoption of diversity also represents a suitable means to restore performance in the presence of dispersive fading and impulsive non-Gaussian noise. It is also shown that the suboptimal GD incurs a limited loss with respect to the optimum GD and this loss is less in comparison with the conventional receiver.
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.
Hadei, Sayed A
2011-01-01
In this paper, we propose novel low-complexity adaptive channel estimation techniques for mob ile wireless chan- n els in presence of Rayleigh fading, carrier frequency offsets (CFO) and random channel variations. We show that the selective p artial update of the estimated channel tap-weight vector offers a better trade-off between the performance and computational complexity, compared to the full update of the estimated channel tap-weight vector. We evaluate the mean-square weight error of th e proposed methods and demonstrate the usefulness of its via simulation studies.
Performance of MC-2D-CDMA over Frequency Selective Channel
Institute of Scientific and Technical Information of China (English)
赵刚
2002-01-01
The de-spreading algorithm of MC-2D-CDMA (Multi-Carrier 2-Dimension Code Division Multiple Access) uses a simple correlator and complex spread spectrum sequences. Each chip of spreading spectrum sequence is in two sub-carriers. With one sub-carrier in deep fading, the chip in the other sub-carrier would compensate to improve performance. Orthogonal restore correlation (ORC) explained the algorithm. The performance was examined analytically and by computer simulations. The performance is better than that of regular MC-2D-CDMA model.
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.
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.
Outage Capacity Analysis of TAS/MRC Systems over Arbitrary Nakagami-m Fading Channels
Hung, Chia-Chun; Chiang, Ching-Tai; Lin, Shyh-Neng; Wu, Rong-Ching
A simple closed-form approximation for the outage capacity of Transmit Antenna Selection/Maximal-Ratio Combining (TAS/MRC) systems over independent and identically distributed (i.i.d) Nakagami-m fading channels is derived while the fading index is a positive integer. When the Nakagami-m fading index is not an integer, the approximate outage capacity is derived as a single infinite series of Gamma function. Computer simulations verify the accuracy of the approximate results.
Analysis of Coded FHSS Systems with Multiple Access Interference over Generalized Fading Channels
Directory of Open Access Journals (Sweden)
Zummo SalamA
2008-01-01
Full Text Available Abstract 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.
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.
Estimation of FBMC/OQAM fading channels using dual Kalman filters.
Aldababseh, Mahmoud; Jamoos, Ali
2014-01-01
We address the problem of estimating time-varying fading channels in filter bank multicarrier (FBMC/OQAM) wireless systems based on pilot symbols. The standard solution to this problem is the least square (LS) estimator or the minimum mean square error (MMSE) estimator with possible adaptive implementation using recursive least square (RLS) algorithm or least mean square (LMS) algorithm. However, these adaptive filters cannot well-exploit fading channel statistics. To take advantage of fading channel statistics, the time evolution of the fading channel is modeled by an autoregressive process and tracked by Kalman filter. Nevertheless, this requires the autoregressive parameters which are usually unknown. Thus, we propose to jointly estimate the FBMC/OQAM fading channels and their autoregressive parameters based on dual optimal Kalman filters. Once the fading channel coefficients at pilot symbol positions are estimated by the proposed method, the fading channel coefficients at data symbol positions are then estimated by using some interpolation methods such as linear, spline, or low-pass interpolation. The comparative simulation study we carried out with existing techniques confirms the effectiveness of the proposed method.
Estimation of FBMC/OQAM Fading Channels Using Dual Kalman Filters
Directory of Open Access Journals (Sweden)
Mahmoud Aldababseh
2014-01-01
Full Text Available We address the problem of estimating time-varying fading channels in filter bank multicarrier (FBMC/OQAM wireless systems based on pilot symbols. The standard solution to this problem is the least square (LS estimator or the minimum mean square error (MMSE estimator with possible adaptive implementation using recursive least square (RLS algorithm or least mean square (LMS algorithm. However, these adaptive filters cannot well-exploit fading channel statistics. To take advantage of fading channel statistics, the time evolution of the fading channel is modeled by an autoregressive process and tracked by Kalman filter. Nevertheless, this requires the autoregressive parameters which are usually unknown. Thus, we propose to jointly estimate the FBMC/OQAM fading channels and their autoregressive parameters based on dual optimal Kalman filters. Once the fading channel coefficients at pilot symbol positions are estimated by the proposed method, the fading channel coefficients at data symbol positions are then estimated by using some interpolation methods such as linear, spline, or low-pass interpolation. The comparative simulation study we carried out with existing techniques confirms the effectiveness of the proposed method.
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.
Directory of Open Access Journals (Sweden)
Ankita Shukla
2011-09-01
Full Text Available We consider multiplexing systems in correlated multiple-input multiple-output (MIMO fading channels with equal power allocated to each transmit antenna. Under several constraints, the number and subset of transmit antennas together with the transmit symbol constellations are determined assuming knowledge of the channel correlation matrices. The maximum outage data rate of the SCR receiver is seen to be close to the outage channel capacity. Identification of the channel matrix is of main concern in wireless multiple input multiple output (MIMO systems. To maximize the SNR, the best way to utilize a MIMO system is to communicate on the top singular vectors of the channel matrix. In this paper we addresses t several issues and the problem of channel tracking and equalization for multi-input multi-output (MIMO time-varying frequency-selective channels. These channels model the effects of inter-symbol interference (ISI, co-channel interference (CCI, and noise. Via singular value decomposition (SVD analysis, the precoder is used to be shown to outperform the orthogonal frequency division multiplexing (OFDM precoder in bit-error-rate (BER, transmission rate, and receiver implementation.
A subspace-based parameter estimation algorithm for Nakagami-m fading channels
Dianat, Sohail; Rao, Raghuveer
2010-04-01
Estimation of channel fading parameters is an important task in the design of communication links such as maximum ratio combining (MRC). The MRC weights are directly related to the fading channel coefficients. In this paper, we propose a subspace based parameter estimation algorithm for the estimation of the parameters of Nakagami-m fading channels in the presence of additive white Gaussian noise. Comparisons of our proposed approach are made with other techniques available in the literature. The performance of the algorithm with respect to the Cramer-Rao bound (CRB) is investigated. Computer simulation results for different signal to noise ratios (SNR) are presented.
A cross-layer adaptive transmission scheme over correlated fading channels
Institute of Scientific and Technical Information of China (English)
XIAO Junfeng; QIU Jing; CHENG Shiduan
2007-01-01
Conventional adaptive transmission schemes perform poorly in wireless correlated slow-fading channels.A cross-layer adaptive transmission scheme combined with selective repeat automatic repeat request(SR-ARQ)is proposed.We apply a multi-state Markov system model for analyzing the performance of systems and optimizing the selection of modulation levels and packet sizes in correlated fading channels,which is also described by a finite-state Markov chain.A general closed-form expression of the average throughput for our suggested scheme is presented.Numerical results show that our adaptive scheme combined with SR-ARQ can obtain good performance in correlated fading channels.
A Simulation Study on the Throughput Performance of TCP over Wireless Fading Channel
Institute of Scientific and Technical Information of China (English)
YAO Ling; JI Hong; YUE Guang-xin
2004-01-01
Using Markov model and the network simulator-NS, this paper studies the TCP throughput performance in wireless fading channel where the packets losses are always caused by high and burst errors. The results show that the burstiness in packet errors caused by slow multipath fading benefits Reno compared to i.i.d packet errors.
Li, Min
2014-07-01
In this paper, the performance of beamforming (BF) for a dual-hop amplify-and-forward (AF) relay network, where the source and destination are each equipped with multiple antennas, is investigated. It is assumed that the source-relay and relay-destination channels experience mixed fading distributions, namely, correlated Nakagami-m/Rician and correlated Rician/Nakagami-m, respectively. By considering fixed-gain relaying, analytical expressions for outage probability (OP) and average symbol error rate (ASER) are derived in closed-form. Numerical results are presented to demonstrate the efficacy of our performance analysis, also illustrate the impact of channel correlation, fading severity, Rician factor and antenna configuration on the performance of the system. It is shown that the correlated Nakagami-m/Rician fading channel can achieve better performance than the correlated Rician/Nakagami-m fading channel with the increase of fading severity parameter, and the correlated Rician/Nakagami-m fading channel may outperform the correlated Nakagami-m/Rician fading channel by enlarging the Rician factor.
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.
A New Generation Method for Spatial-Temporal Correlated MIMO Nakagami Fading Channel
Directory of Open Access Journals (Sweden)
Qiu-Ming Zhu
2012-01-01
Full Text Available A new generation method for spatial and temporal correlated multiple-input multiple-output (MIMO Nakagami fading channel is proposed, which has low complexity and is applicable for arbitrary fading parameters and prespecified correlation coefficients of different subchannel. The new scheme can be divided into two steps: (1 generate independent Nakagami fading sequences for each subchannel based on a novel rejection method; (2 introduce the temporal and spatial correlation based on the relationships between Rayleigh, Gamma, and Nakagami random processes. The analysis and simulation results show that the proposed simulator has a good agreement with the theoretical model on fading envelope distribution, spatial-temporal correlation characteristic.
COMPUTER SIMULATION OF RAYLEIGH FADING CHANNELS IN MC-CDMA SYSTEMS
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
For Multi-Carrier-Code Division Multiple Access (MC-CDMA) systems, it is usually assumed that the fading of the subcarriers is frequency non-selective and independent of each other.This paper shows that the two assumptions are incompatible. In fact, the MC-CDMA signals at each subcarrier undergo fading that are highly correlated. Based on this observation, this paper develops a simulation algorithm for Rayleigh fading channels via frequency-domain correlation function, which incorporates the Doppler effect simultaneously. Numerical examples are presented to demonstrate the effectiveness of the new algorithm, with the conclusion that the independence assumption of subcarrier fading overrates the system performance.
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.
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...
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.
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.
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.
Performance of MC-CDMA Systems with Orthogonal Transmit Diversity over Rayleigh Fading Channel
Institute of Scientific and Technical Information of China (English)
樊凌涛; 李高志; 陈健
2003-01-01
Transmit diversity has been recently proposed to reduce the effects of fading channels in various wireless applications. Orthogonal transmit diersity (OTD) is one of the standardized techniques in 3G systems. In this paper, we apply orthogonal transmit diversity technique to multicarrier CDMA systems. Andlysis and simulation results show that performance benefits can be achieved compared with conventioal MC-CDMA systems in multipath fading channels.
A Tight Lower Bound to the Outage Probability of Discrete-Input Block-Fading Channels
Nguyen, Khoa D; Rasmussen, Lars K
2007-01-01
In this correspondence, we propose a tight lower bound to the outage probability of discrete-input Nakagami-m block-fading channels. The approach permits an efficient method for numerical evaluation of the bound, providing an additional tool for system design. The optimal rate-diversity trade-off for the Nakagami-m block-fading channel is also derived and a tight upper bound is obtained for the optimal coding gain constant.
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.
A NEW ML DETECTION ALGORITHM FOR ORTHOGONAL MULTICODE SYSTEM IN NAKAGAMI FADING CHANNEL
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Based on the Maximum-Likelihood (ML) criterion, this paper proposes a novel noncoherent de-tection algorithm for Orthogonal Multicode (OM) system in Nakagami fading channel. Some theoreticalanalysis and simulation results are presented. It is shown that the proposed ML algorithm is at least 0.7 dBbetter than the conventional Matched-Filter (MF) algorithm for uncoded systems, in both non-fading and fad-ing channels. For the consideration of practical application, it is further simplified in complexity. Comparedwith the original ML algorithm, the simplified ML algorithm can provide significant reduction in complexitywith small degradation in performance.
Directory of Open Access Journals (Sweden)
Jyoteesh Malhotra
2011-03-01
Full Text Available By using versatile generic-K statistical model, a performance analysis of wireless system has been carried out through the composite fading channel scenarios. The composite fading model used here is flexible enough to represent all forms of mixed shadowed-fading channel conditions. With the aid of moment generating function (MGF approach and Padé approximation (PA technique, different performance measures such as outage probability and average bit error rate (ABER have been evaluated for a variety of digital modulation formats. In contrast to previously obtained relatively complicated expressions in terms of MeijerG & Whittaker special functions, the PA technique has been used here to find tractable rational expressions for the MGF of output SNR. Using these simple rational expressions, the performance evaluations have been done for both single- and multichannel receivers under different shadowed-fading channel conditions. The numerical results are also validated through computer simulations, which show a perfect match.
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.
PERFORMANCE ANALYSIS OF CHANNEL ESTIMATION FOR LDPC-CODED OFDM SYSTEM IN MULTIPATH FADING CHANNEL
Institute of Scientific and Technical Information of China (English)
Zhu Qi; Li Hao; Feng Guangzeng
2006-01-01
In this paper, the channel estimation techniques for Orthogonal Frequency Division Multiplexing (OFDM) systems based on pilot arrangement are studied and we apply Low Density Parity Check (LDPC) codes to the system of IEEE 802.16a with OFDM modulation. First investigated is the influence of channel estimation schemes on LDPC-code based OFDM system in static and multipath fading channels. According to the different propagation environments in 802.16a system, a dynamic channel estimation scheme is proposed.A good irregular LDPC code is designed with code rate of 1/2 and code length of 1200. Simulation results show that the performance of LDPC coded OFDM system proposed in this paper is better than that of the convolution Turbo coded OFDM system proposed in IEEE standard 802.16a.
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.
CYCLOSTATIONARITY-BASED OFDM SIGNAL SENSING OVER DOUBLY-SELECTIVE FADING CHANNELS
Institute of Scientific and Technical Information of China (English)
Tian Jinfeng; Jiang Yonglei; Chen Huaxia; Hu Honglin
2011-01-01
In this paper,using cyclostationarity-based sensing method to detect the presence of Orthogonal Frequency Division Multiplexing (OFDM) signal over doubly-selective fading channels is studied.By approximating the channel with Basis Expansion Model (BEM),we derive the second-order cyclostationary statistics of the received OFDM signal over doubly-selective fading channels.Theoretical analysis indicates that new cyclostationary signatures produced by Doppler spread and multipath delay can be further exploited in the detecting process.Simulation examples demonstrate that the sensing methods using channel-induced cyclostationary features provide substantial improvements on detection performance.
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.
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.
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.
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.
A Practical Adaptive TuCM Scheme for Rayleigh Flat Fading Channels
Institute of Scientific and Technical Information of China (English)
伍守豪; 宋文涛
2004-01-01
A practical adaptive turbo coded modulation (TuCM) scheme was proposed and its adaptive method was described. With some hardware considerations, a suboptimal optimization algorithm that the number of fading regions is variable was put forward. Furthermore, the cutoff fade depth of power adaptation was modified to reduce the interruption probability. The results show that the proposed adaptive TuCM comes within 3 dB of Rayleigh fading channel capacity, and exhibits about 3 dB power gain relative to the conventional adaptive trellis-coded modulation (TCM), and is easy to realize by hardware.
A Unified MGF-Based Capacity Analysis of Diversity Combiners over Generalized Fading Channels
Yilmaz, Ferkan
2010-01-01
Unified exact average capacity results for L-branch coherent diversity receivers 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.
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.
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.
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.
Performance of quasi-optimum digital FM demodulators for fading channels
Dharamsi, M. T.; Gupta, S. C.
1975-01-01
This paper deals with the problem of digital demodulation of FM signals transmitted over Rayleigh and Rician fading channels. The Rayleigh and Rician fading channels are represented by two quadrature multiplicative nonzero mean white Gaussian processes in addition to an additive zero-mean white Gaussian noise. Quasi-optimum digital baseband demodulation algorithms using various nonlinear estimation techniques are derived. The digital demodulator structures are then simulated on a digital computer for an FM system with first order message spectrum for various values of the parameters for Rayleigh and Rician channels.
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.
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.
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.
Codebook Design and Hybrid Digital/Analog Coding for Parallel Rayleigh Fading Channels
Shi, Shuying; Larsson, Erik G.; Skoglund, Mikael
2011-01-01
Low-delay source-channel transmission over parallel fading channels is studied. In this scenario separate sourceand channel coding is highly suboptimal. A scheme based on hybrid digital/analog joint source-channel coding istherefore proposed, employing scalar quantization and polynomial-based analog bandwidth expansion. Simulationsdemonstrate substantial performance gains. Funding agencies|European Community|248993|EL-LIIT||Knut and Alice Wallenberg Foundation||
Adaptive Channel Equalization Using Multiplicative Neural Network for Rayleigh Faded Channel
Directory of Open Access Journals (Sweden)
P. Sivakumar
2011-01-01
Full Text Available Problem statement: Digital transmission over band-limited communication channel largely suffers from ISIS and various noise sources. The presence of ISI and noise causes bit errors in the received signal. Equalization is necessary at the receiver to overcome these channel impairment to recover the original transmitted sequence. Traditionally equalization is considered as equivalent to inverse filtering and implemented using linear-perform under severe distortion conditions when Signal to Noise Ratio (SNR is poor. Equalization can be considered as a non-linear classification problem and optimum solution is given by Bayesian solution. Non-linear techniques like Artificial Neutral Networks (ANN are very good choice for non-linear classification problems. Several non-lines are equalizers have been implemented using ANN which outperformed LTE and solved the problem of equalization to the varying degree of sources. Approach: Forward neural network architecture with optimum number of nodes was used to achieve adaptive channel equalization. Summation at each node was replaced by multiplications which result in powerful mapping. The equalizer was tested on Rayleigh fading channel with a BPSK signal. Results: Results showed that proposed equalizer provides simplified architecture and improvement in the bit error rate at various levels of signal to noise ratio for Rayleigh faded channel. Conclusion: A high order feed forward network equalizer with multiplicative neuron is proposed in this study. Use of Multiplication allows direct computing of polynomial inputs and approximation with fewer nodes. Performance comparison in terms of network architecture and BER performance suggest the better classification capability of the proposed MNN equalizer over RRBF.
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.
Communications by vocoder on a mobile satellite fading channel
dal Degan, N.; Perosino, F.; Rusina, F.
The performance of a LPC vocoder system is analyzed under various bit rate and fading errors. The error generation model developed to estimate error probability, and length of error bursts and distributions is described. Two algorithms that will improve burst are proposed. The evaluation of the spectral distance measures of the voice coding system is examined. The intelligibility, quality, and acceptability of the system are assessed using the mean opinion scores method.
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.
Directory of Open Access Journals (Sweden)
Mohamed Abd El-latif
2012-01-01
Full Text Available In this paper the encoder design of two parallel concatenated convolutional codes (PCCC have been introduced. Concept of puncturing is also considered. PCCC is also named as Turbo codes. Decoding process of turbo-codes using a maximum a posteriori (MAP algorithm has been discussed. Different parameters affect the BER performance of turbo codes are introduced .The previous studies focusing on the turbo-codes performance in (AWGN and Rayleigh multipath- fading channels. The real importance of Nakagami –m fading model lies in the fact that it can often be used to fit the indoor channel measurements for digital cellular systems such as global system mobile (GSM. In this paper, the BER performance and comparative study of turbo-codes in Nakagami multipath- fading channel is verified using Matlab simulation program.
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.
Multiple-Symbol Decision-Feedback Space-Time Differential Decoding in Fading Channels
Directory of Open Access Journals (Sweden)
Yan Liu
2002-03-01
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.
Pappi, Koralia N; Chronis, Theodore N; Karagiannidis, George K
2012-01-01
This is the second part of a two-part series of papers, where the error performance of multidimensional lattice constellations with signal space diversity (SSD) is investigated. In Part I, following a novel combinatorial geometrical approach which is based on parallelotope geometry, we have presented an exact analytical expression and two closed-form bounds for the symbol error probability (SEP) in Additive White Gaussian Noise (AWGN). In the present Part II, we extend the analysis and present a novel analytical expression for the Frame Error Probability (FEP) of multidimensional lattice constellations over Nakagami-m fading channels. As the FEP of infinite lattices is lower bounded by the Sphere Lower Bound (SLB), we propose the Sphere Upper Bound (SUB) for block fading channels. Furthermore, two novel bounds for the FEP of multidimensional lattice constellations over block fading channels, named Multiple Sphere Lower Bound (MSLB) and Multiple Sphere Upper Bound (MSUB), are presented. The expressions for the...
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.
Extended Generalized-K (EGK): A New Simple and General Model for Composite Fading Channels
Yilmaz, Ferkan
2010-01-01
In this paper, we introduce a generalized composite fading distribution (termed extended generalized-K (EGK)) to model the envelope and the power of the received signal in millimeter wave (60 GHz or above) and free-space optical channels. We obtain the first and the second-order statistics of the received signal envelope characterized by the EGK composite fading distribution. In particular, expressions for probability density function, cumulative distribution function, level crossing rate and average fade duration, and fractional moments are derived. In addition performance measures such as amount of fading, average bit error probability, outage probability, average capacity, and outage capacity are offered in closed-form. Selected numerical and computer simulation examples validate the accuracy of the presented mathematical analysis.
AN ITERATIVE PARTICLE FILTER SIGNAL DETECTOR FOR MIMO FAST FADING CHANNELS
Institute of Scientific and Technical Information of China (English)
Yang Tao; Hu Bo
2008-01-01
For flat fast fading Multiple-Input Multiple-Output (MIMO) channels, this paper presents a sampling based channel estimation and an iterative Particle Filter (PF) signal detection scheme. The channel estimation is comprised of two parts: the adaptive iterative update on the channel distribution mean and a regular update on the "adaptability" via pilot. In the detection procedure, the PF is employed to produce the optimal decision given the known received signal and the sequence of the channel samples, where an asymptotic optimal importance density is constructed, and in terms of the asymptotic update order, the Parallel Importance Update (PIU) and the Serial Importance Update (SIU) scheme are performed respectively. The simulation results show that for the given fading channel, if an appropriate pilot mode is selected, the proposed scheme is more robust than the conventional Kalman filter based superimposed detection scheme.
Institute of Scientific and Technical Information of China (English)
Chen Zhi; Li Shaoqian; Dong Binhong
2008-01-01
A novel non-coherent detection scheme for differential frequency hopping (DFH) system is proposed in asynchronous multi-user environments over Rayleigh-fading channels. The synchronous and asynchronous multi-user performances of DFH with the conventional detection scheme and this novel detection scheme are analyzed, respectively. The performance results are validated with simulation. The results of analyses and simulations prove two conclusions. Firstly, the performance of asynchronous multi-user DFH system overcomes that of synchronous multi-user DFH system over Rayleigh-fading channel. Secondly, the novel detection scheme can achieve better performance than the conventional non-coherent detection scheme in asynchronous multi-user environments.
Multicarrier CDMA Systems with Transmit Diversity in Two—Ray Multipath Fading Channels
Institute of Scientific and Technical Information of China (English)
FANLingtao; CHENJian
2003-01-01
Transmit diversity is recently proposed to reduce the effects in fading channels in various wireless applications. In this paper, we apply a transmit diversity technique to downlink multicarrier CDMA (Code devision multiple access) systems, which utilize the cyclic shift ver-sions of the normal spread codes as the spread sequences in transmit diversity branches. A RAKE-like parallel receiver is employed in frequency domain to obtain diversity gains.Simulation results show that performance benefits can be achieved compared to conventional MC-CDMA systems in Z-ray multipath fading channels.
EXACT ERROR PROBABILITY OF ORTHOGONAL SPACE-TIME BLOCK CODES OVER FLAT FADING CHANNELS
Institute of Scientific and Technical Information of China (English)
Xu Feng; Yue Dianwu
2007-01-01
Space time block coding is a modulation scheme recently discovered for the transmit antenna diversity to combat the effects of wireless fading channels. Using the equivalent Single-Input Single-Output (SISO) model, this paper presents closed-form expressions for the exact Symbol Error Rate (SER) and Bit Error Rate (BER) of Orthogonal Space-Time Block Codes (OSTBCs) with M-ary Phase-Shift Keying (MPSK) and M-ary Quadrature Amplitude Modulation (MQAM) over flat uncorrelated Nakagami-m and Ricean fading channels.
Performance analysis of digital FM demodulators for fading channels in the threshold region
Dharamsi, M. T.; Gupta, S. C.
1976-01-01
The quasi-optimum digital FM demodulators for fading channels reported earlier (1975) reflected the system performance accurately under high signal to noise ratio conditions. In this paper, the prediction of the system performance for low SNR values is considered. A new set of error variance algorithms is developed from the filter algorithm assuming a Gaussian distribution for the state estimation errors and taking the effect of high frequency terms into consideration. Simulation analysis for an FM system with Rician fading channel shows that these algorithms predict the system performance accurately in the threshold region.
Secure Communication over Fading Channels with Statistical QoS Constraints
Qiao, Deli; Gursoy, Mustafa Cenk; Velipasalar, Senem
2010-01-01
In this paper, the secure transmission of information over an ergodic fading channel is investigated in the presence of statistical quality of service (QoS) constraints. We employ effective capacity, which provides the maximum constant arrival rate that a given process can support while satisfying statistical delay constraints, to measure the secure throughput of the system, i.e., effective secure throughput. We assume that the channel side information (CSI) of the main channel is available a...
Turbo Equalization for Frequency Selective Fading MIMO Channels%频选衰落MIMO信道的Turbo均衡
Institute of Scientific and Technical Information of China (English)
金奕丹; 吴伟陵
2006-01-01
针对Turbo编码频选慢衰落MIMO信道,提出基于滑窗式概率数据辅助(Probabilistic Data Association)的软输出判决反馈均衡和软输入软输出Turbo信道解码器间迭代处理的Turbo均衡算法.充分利用已获得的信息,实现信道均衡与信道解码的迭代更新,克服传统判决反馈均衡器误差传播的缺陷.仿真表明,该系统经3次迭代就可获得较为满意的符号间干扰消除效果.
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...
A Fast-CSMA Algorithm for Deadline-Constrained Scheduling over Wireless Fading Channels
Li, Bin
2012-01-01
Recently, low-complexity and distributed Carrier Sense Multiple Access (CSMA)-based scheduling algorithms have attracted extensive interest due to their throughput-optimal characteristics in general network topologies. However, these algorithms are not well-suited for serving real-time traffic under time-varying channel conditions for two reasons: (1) the mixing time of the underlying CSMA Markov Chain grows with the size of the network, which, for large networks, generates unacceptable delay for deadline-constrained traffic; (2) since the dynamic CSMA parameters are influenced by the arrival and channel state processes, the underlying CSMA Markov Chain may not converge to a steady-state under strict deadline constraints and fading channel conditions. In this paper, we attack the problem of distributed scheduling for serving real-time traffic over time-varying channels. Specifically, we consider fully-connected topologies with independently fading channels (which can model cellular networks) in which flows wi...
How to Achieve the Optimal DMT of Selective Fading MIMO Channels?
Mroueh, Lina
2010-01-01
In this paper, we consider a particular class of selective fading channel corresponding to a channel that is selective either in time or in frequency. For this class of channel, we propose a systematic way to achieve the optimal DMT derived in Coronel and B\\"olcskei, IEEE ISIT, 2007 by extending the non-vanishing determinant (NVD) criterion to the selective channel case. A new code construction based on split NVD parallel codes is then proposed to satisfy the NVD parallel criterion. This result is of significant interest not only in its own right, but also because it settles a long-standing debate in the literature related to the optimal DMT of selective fading channels.
LNN Blind Multi-user Detection Algorithm for Multi-path-fading CDMA Channels
Institute of Scientific and Technical Information of China (English)
LI Yan-ping; WANG Hua-kui; MIAO Rui-qing
2006-01-01
A blind multi-user detection algorithm (BMUD) which is suitable for multi-path-fading Channels based on Lagrange neural network (LNN) is proposed. Based on the minimum output energy (MOE) criterion, the blind detection algorithm is formulated as a constrained optimization problem inherently and is then resolved efficiently using the neural network. Compared with the previous RLS(recursive least squares )-MOE blind detection algorithm or for multi-path channel, the BMUD based on LNN has better performances: lower computational complexity, faster convergence speed and capability in the multi-path-fading channel. The bit error rate (BER) and signal-to-interference-and-noise ratio(SINR) performances of the detection algorithm in multi-path channel are close to that in single path channel.
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 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.
Directory of Open Access Journals (Sweden)
Chen Bor-Sen
2010-01-01
Full Text Available A recursive maximum-likelihood (RML algorithm for channel estimation under rapidly fading channel and colored noise in a multicarrier code-division multiple-access (MC-CDMA system is proposed in this paper. A moving-average model with exogenous input (MAX is given to describe the transmission channel and colored noise. Based on the pseudoregression method, the proposed RML algorithm can simultaneously estimate the parameters of channel and colored noise. Following the estimation results, these parameters can be used to enhance the minimum mean-square error (MMSE equalizer. Considering high-speed mobile stations, a one-step linear trend predictor is added to improve symbol detection. Simulation results indicate that the proposed RML estimator can track the channel more precisely than the conventional estimator. Meanwhile, the performance of the proposed enhanced MMSE equalizer is robust to the rapidly Rayleigh fading channel under colored noise in the MC-CDMA systems.
Zlatanov, Nikola; Karagiannidis, George K; 10.1109/LCOMM.2008.081058
2009-01-01
We present novel exact expressions and accurate closed-form approximations for the level crossing rate (LCR) and the average fade duration (AFD) of the double Nakagami-m random process. These results are then used to study the second order statistics of multiple input multiple output (MIMO) keyhole fading channels with space-time block coding. Numerical and computer simulation examples validate the accuracy of the presented mathematical analysis and show the tightness of the proposed approximations.
Performance Analysis of Amplify-and-Forward Relaying over Shadowed Nakagami-m Fading Channels
Cai, Chunxiao; Cai, Yueming; Yang, Weiwei
2011-11-01
In the paper, the closed-form approximation for outage probability and symbol error probability are presented for amplify-and-forward cooperative network over shadowed Nakagami-m Fading Channels. Our results are verified through comparison with Monte Carlo simulations. It shows that our theoretical results can provide good approximations to the numerical results.
Outage probability of opportunistic decode-and-forward relaying over Nakagami-m fading channels
Institute of Scientific and Technical Information of China (English)
CHUAI Gang; ZHANG Bao-zhi; LIU Xing-mei; GAO Li
2009-01-01
In this article, the outage probability behavior of a relay network over Nakagami-m fading channels is analyzed. Both reactive and proactive opportunistic decode-and-forward (DAF) strategies are considered. The closed-form solutions to the outage probabilities on both opportunistic DAF strategies are derived. Simulation results conf'Lrrn the presented mathematical analysis.
Distributive Network Utility Maximization (NUM) over Time-Varying Fading Channels
Chen, Junting; Lau, Vincent K N
2011-01-01
Distributed network utility maximization (NUM) has received an increasing intensity of interest over the past few years. Distributed solutions (e.g., the primal-dual gradient method) have been intensively investigated under fading channels. As such distributed solutions involve iterative updating and explicit message passing, it is unrealistic to assume that the wireless channel remains unchanged during the iterations. Unfortunately, the behavior of those distributed solutions under time-varying channels is in general unknown. In this paper, we shall investigate the convergence behavior and tracking errors of the iterative primal-dual scaled gradient algorithm (PDSGA) with dynamic scaling matrices (DSC) for solving distributive NUM problems under time-varying fading channels. We shall also study a specific application example, namely the multi-commodity flow control and multi-carrier power allocation problem in multi-hop ad hoc networks. Our analysis shows that the PDSGA converges to a limit region rather tha...
Performance Analysis and Formulation of Turbo Coded OFDM over Rayleigh & Rician Fading Channel
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Avijit Patel
2012-05-01
Full Text Available In wireless communication, to attain high throughput and better transmission quality, there is a need of better system design . Orthogonal Frequency Division Multiplexing (OFDM is a techniques for parallel transmission. The performance of OFDM can be improved by using some kind of channel coding. This form of OFDM is called coded-OFDM (COFDM. In this paper Turbo code is used as channel coding with OFDM, called Turbo coded OFDM .This paper compares the performance of Turbo coded OFDM using binary phase shift keying (BPSK , Quadrature Phase Shift Keying (QPSK , Quadrature Amplitude Modulation (QAM modulation technique for different Rayleigh and Rician fading channel . Results is formulated that a combination fading channel and modulation technique gives better performance.
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.
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.
Efficient LLR Calculation for Non-Binary Modulations over Fading Channels
Yazdani, Raman
2010-01-01
Log-likelihood ratio (LLR) computation for non-binary modulations over fading channels is complicated. A measure of LLR accuracy on asymmetric binary channels is introduced to facilitate good LLR approximations for non-binary modulations. Considering piecewise linear LLR approximations, we prove convexity of optimizing the coefficients according to this measure. For the optimized approximate LLRs, we report negligible performance losses compared to true LLRs.
Node Isolation Probability of Wireless Adhoc Networks in Nagakami Fading Channel
Babu, A V; 10.5121/ijcnc.2010.2202
2010-01-01
This paper investigates the issue of connectivity of a wireless adhoc network in the presence of channel impairments. We derive analytical expressions for the node isolation probability in an adhoc network in the presence of Nakagami-m fading with superimposed lognormal shadowing. The node isolation probability is the probability that a randomly chosen node is not able to communicate with none of the other nodes in the network. An extensive investigation into the impact of path loss exponent, lognormal shadowing, Nakagami fading severity index, node density, and diversity order on the node isolation probability is conducted. The presented results are beneficial for the practical design of ad hoc networks.
Performance analysis of EGC combining over correlated Nakagami-m fading channels
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Milić Dejan
2012-01-01
Full Text Available In this paper, performance analysis of diversity technique with equal gain combining method (EGC with two branches for the detection of signals in wireless communication systems is presented. In the following analysis, it is assumed that the fading via channels is Nakagami-m correlated. The first order statistical characteristics of the system are analysed. Useful formulae for the probability density function (pdf and cumulative distribution function (CDF of EGC output SIR are derived, and the effects of the fading severity on the output signal are observed.
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AMITA SONI
2009-03-01
Full Text Available Channel time-variation (or fading is the major source of impairment in digital wireless communications. This occurs due to mobility of the user or of the objects in the propagation environment. The limited spectral bandwidth necessitates the use of resource sharing schemes between multiple users. As the transmission medium is shared between the users, this leads to interference between the users. Sharing of resource results in interference such as multiple access interference. This paper deals with methods to study and mitigate such interference considering Rayleigh fading channels. There are various classes of fading conditions. The use of CDMA is under active research as a viable alternative to TDMA and FDMA. Performance in this system is limited by narrowband and multiple access interference. Various methods are used to mitigate them. But here, linear MMSE detector is considered. MMSE technique results in interference rejection. Its adaptive form is applied to Rayleigh fading channels, which are reflective and nondispersive. It results into better results than before.
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.
Receiver Diversity Combining Using Evolutionary Algorithms in Rayleigh Fading Channel
Akbari, Mohsen; Manesh, Mohsen Riahi
2014-01-01
In diversity combining at the receiver, the output signal-to-noise ratio (SNR) is often maximized by using the maximal ratio combining (MRC) provided that the channel is perfectly estimated at the receiver. However, channel estimation is rarely perfect in practice, which results in deteriorating the system performance. In this paper, an imperialistic competitive algorithm (ICA) is proposed and compared with two other evolutionary based algorithms, namely, particle swarm optimization (PSO) and genetic algorithm (GA), for diversity combining of signals travelling across the imperfect channels. The proposed algorithm adjusts the combiner weights of the received signal components in such a way that maximizes the SNR and minimizes the bit error rate (BER). The results indicate that the proposed method eliminates the need of channel estimation and can outperform the conventional diversity combining methods. PMID:25045725
Receiver Diversity Combining Using Evolutionary Algorithms in Rayleigh Fading Channel
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Mohsen Akbari
2014-01-01
Full Text Available In diversity combining at the receiver, the output signal-to-noise ratio (SNR is often maximized by using the maximal ratio combining (MRC provided that the channel is perfectly estimated at the receiver. However, channel estimation is rarely perfect in practice, which results in deteriorating the system performance. In this paper, an imperialistic competitive algorithm (ICA is proposed and compared with two other evolutionary based algorithms, namely, particle swarm optimization (PSO and genetic algorithm (GA, for diversity combining of signals travelling across the imperfect channels. The proposed algorithm adjusts the combiner weights of the received signal components in such a way that maximizes the SNR and minimizes the bit error rate (BER. The results indicate that the proposed method eliminates the need of channel estimation and can outperform the conventional diversity combining methods.
Secure Communication over Fading Channels with Statistical QoS Constraints
Qiao, Deli; Velipasalar, Senem
2010-01-01
In this paper, the secure transmission of information over an ergodic fading channel is investigated in the presence of statistical quality of service (QoS) constraints. We employ effective capacity, which provides the maximum constant arrival rate that a given process can support while satisfying statistical delay constraints, to measure the secure throughput of the system, i.e., effective secure throughput. We assume that the channel side information (CSI) of the main channel is available at the transmitter side. Depending on the availability of the CSI of the eavesdropper channel, we obtain the corresponding optimal power control policies that maximize the effective secure throughput. In particular, when the CSI of the eavesdropper channel is available at the transmitter, the transmitter can no longer wait for transmission when the main channel is much better than the eavesdropper channel due to the introduction of QoS constraints. Moreover, the CSI of the eavesdropper channel becomes useless as QoS constr...
On Amplify-and-Forward Relaying Over Hyper-Rayleigh Fading Channels
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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.
Fading probability density function of free-space optical communication channels with pointing error
Zhao, Zhijun; Liao, Rui
2011-06-01
The turbulent atmosphere causes wavefront distortion, beam wander, and beam broadening of a laser beam. These effects result in average power loss and instantaneous power fading at the receiver aperture and thus degrade performance of a free-space optical (FSO) communication system. In addition to the atmospheric turbulence, a FSO communication system may also suffer from laser beam pointing error. The pointing error causes excessive power loss and power fading. This paper proposes and studies an analytical method for calculating the FSO channel fading probability density function (pdf) induced by both atmospheric turbulence and pointing error. This method is based on the fast-tracked laser beam fading profile and the joint effects of beam wander and pointing error. In order to evaluate the proposed analytical method, large-scale numerical wave-optics simulations are conducted. Three types of pointing errors are studied , namely, the Gaussian random pointing error, the residual tracking error, and the sinusoidal sway pointing error. The FSO system employs a collimated Gaussian laser beam propagating along a horizontal path. The propagation distances range from 0.25 miles to 2.5 miles. The refractive index structure parameter is chosen to be Cn2 = 5×10-15m-2/3 and Cn2 = 5×10-13m-2/3. The studied cases cover from weak to strong fluctuations. The fading pdf curves of channels with pointing error calculated using the analytical method match accurately the corresponding pdf curves obtained directly from large-scale wave-optics simulations. They also give accurate average bit-error-rate (BER) curves and outage probabilities. Both the lognormal and the best-fit gamma-gamma fading pdf curves deviate from those of corresponding simulation curves, and they produce overoptimistic average BER curves and outage probabilities.
PERFORMANCE OF CLOSED LOOP TRANSMIT DIVERSITY IN A RAYLEIGH FADING CHANNEL
Institute of Scientific and Technical Information of China (English)
Yang Xin; You Xiaohu
2006-01-01
In this paper, the closed loop transmit diversity technology for the Wideband Code Division Multiple Access(WCDMA) systems is investigated in a multipath Rayleigh fading channel. The RAKE receiver model and the weighing vector algorithm are presented. The performance is theoretically analyzed in terms of the average maximal Signal-to-Noise Ratio(SNR) gain available over the Space-Time block coding based Transmit Diversity(STTD) technology. Theoretic analysis and simulation results show that the closed loop transmit diversity can provide a 3dB performance gain over the open loop scheme in a single path fading channel, while the performance gain decreases dramatically with the increasing inherent multipath diversity of the wireless channel.
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.
Power Allocation for Fading Channels with Peak-to-Average Power Constraints
Nguyen, Khoa D; Rasmussen, Lars K
2008-01-01
Power allocation with peak-to-average power ratio constraints is investigated for transmission over Nakagami-m fading channels with arbitrary input distributions. In the case of delay-limited block-fading channels, we find the solution to the minimum outage power allocation scheme with peak-to-average power constraints and arbitrary input distributions, and show that the signal-to-noise ratio exponent for any finite peak-to-average power ratio is the same as that of the peak-power limited problem, resulting in an error floor. In the case of the ergodic fully-interleaved channel, we find the power allocation rule that yields the maximal information rate for an arbitrary input distribution and show that capacities with peak-to-average power ratio constraints, even for small ratios, are very close to capacities without peak-power restrictions.
To Cooperate, or Not to Cooperate in Imperfectly-Known Fading Channels
Zhang, Junwei
2008-01-01
In this paper, communication over imperfectly-known fading channels with different degrees of cooperation is studied. The three-node relay channel is considered. It is assumed that communication starts with the network training phase in which the receivers estimate the fading coefficients of their respective channels. In the data transmission phase, amplify-and-forward and decode-and-forward relaying schemes are employed. For different cooperation protocols, achievable rate expressions are obtained. These achievable rate expressions are then used to find the optimal resource allocation strategies. In particular, the fraction of total time or bandwidth that needs to be allocated to the relay for best performance is identified. Under a total power constraint, optimal allocation of power between the source and relay is investigated. Finally, bit energy requirements in the low-power regime are studied.
Rached, Nadhir Ben
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.
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.
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Kuttathatti S. Vishvaksenan
2011-01-01
Full Text Available Problem statement: This study presents the performance analysis of multi-user Multi Input Multi Output (MIMO assisted interleave based multiple-access system. In IDMA, different interleavers are used to distinguish users as against different signature sequence in a conventional code-Division Multiple-Access (CDMA scheme. Approach: The basic principle of IDMA is that the interleaver is unique for the users. Results: In this study, we consider that Interleavers are generated independently and randomly. Also the IDMA technique is extended to multi user MIMO IDMA with multi-user detection. At the receiver, OSIC detector is realized using ZF for frequency fading channel to combat MAI and MUI problem. The performance of the system is analyzed for different channel conditions using extensive simulation runs based on Monte Carlo simulation trials. Conclusion: It is shown that the IDMA scheme can achieve near single user performance in situations with very large numbers of users while maintaining very low receiver complexity. It is discerned from the computer simulation results that IDMA outperforms CDMA in frequency selective channel for high load conditions.
Robustness of predictive sensor network routing in fading channels
Muraleedharan, Rajani; Osadciw, Lisa A.
2005-06-01
Sensors have varied constraints, which make the network challenging for communicating with peers. In this paper, an extension, to the physical layer of the previous predictive sensor network model using the ant system is proposed. The tiny and low-cost sensor nodes are made of RF wireless links, where the states of the nodes vary with respect to time and environment. The ant system is a learning algorithm, that can be used to solve any NP hard communication problem and possesses characteristics such as robustness and versatility. The ant system possesses unique features that keep the network functional by detecting weak links and re-routing the agents. The swarm agents are distributed along the network, where the agent communicates with its neighbors (agents) by means of pheromone deposition and tabu list. The transition probability in the ant system includes an objective function, which is influenced by the poset weights. The poset weights on each of the orthogonal communication parameters greatly affects the decisions made by ant system. The agents carry updated information of its previous nodes, which helps in monitoring the strength of the communication links. Through simulation, comparison between DSSS-BPSK and Bluetooth-GFSK signals are shown. This paper demonstrates the robustness of the model under slow/fast fading, and energy loss at node during transmission. Implementation of this algorithm should be able to handle hostile environmental conditions and human tampering of data. The performance of the network is evaluated based on accuracy and response time of the agents within the network.
Institute of Scientific and Technical Information of China (English)
YUE DianWu; WANG Qian
2009-01-01
Orthogonal space-time block codes (OSTBCs) are an efficient mean In order to exploit the diversity offered by the wireless multiple-input multiple-output (MIMO) channel.This paper considers capacity problems of OSTBCs over spatially correlated multiple-input single-out (MISO) Rayleigh fading channels in the presence of spatially correlated Rayleigh co-channel interference and additive Gaussian noise,and derives exact expressions of the ergodic capacity and outage probability (capacity distribution) for such OSTBCs.Some numerical examples are given to illustrate the effect of co-channel interference on the ergodic and outage capacity of OSTBCs.
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Kuttathatti S. Vishvaksenan
2011-01-01
Full Text Available Problem statement: This study presents the performance analysis of turbo assisted Interleave Division Multiple-Access (IDMA system with Multi Input Multi Output (MIMO support for multi user scenario over correlated frequency selective and uncorrelated frequency selective channel. Approach: The key principle of IDMA is that interleaver unique which distinguishes the users in contrast to spreading sequence in Code Division Multiple Access System (CDMA. Results: In this work, we assume that Interleavers are generated independently and randomly. At the receiver, we employed Ordered SIC (OSIC technique using ZF and MMSE criterion to combat Inter Antenna Interference (IAI and Multi User Interference (MUI problem along with iterative decoding to improve the performance in terms of BER. The performance of system has been discussed for different channel conditions with realistic channel model using extensive simulation runs based on Monte Carlo simulation trials. We have exhibited the flexibility and robustness provided by MIMO-IDMA. Conclusion/Recommendations: It has been proved from the results that IDMA principle can be applied to realize many potential performance gains highlighted by information theory, including coding gain multiplexing gain and multiuser gain. Simulation results presented to demonstrate the benefits of IDMA with MUD and iterative decoding. It is discerned that IDMA performs better than CDMA in frequency selective channel for high load conditions which is assessed through computer simulation results.
Takeuchi, Keigo
2012-01-01
User selection (US) with Zero-forcing beamforming (ZF-BF) is considered in fast fading Gaussian vector broadcast channels (VBCs) with perfect channel state information (CSI) at the transmitter. A novel criterion for US is proposed, which depends on both CSI and the data symbols, while the conventional criteria only depend on CSI. Since the optimization of US based on the proposed criterion is infeasible, a greedy algorithm of data-dependent US is proposed to perform the optimization approximately. An overhead issue arises in fast fading channels: On every update of US, the transmitter may inform each user whether he/she has been selected, using a certain fraction of resources. This overhead results in a significant rate loss for fast fading channels. In order to circumvent this overhead issue, iterative detection and decoding schemes are derived on the basis of belief propagation (BP). The proposed iterative schemes require no information about whether each user has been selected. The proposed US scheme is co...
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M. Gangadharappa
2010-07-01
Full Text Available In this paper, we have presented how the capacity of cellular system can be enhanced by using Space Division Multiple Access (SDMA with directive antenna in mobile communication systems. One of the biggest draw back of wireless environment is the limited bandwidth. However,the users sharing this limited bandwidth have been increased considerably. SDMA is a technology by which the capacity of the existing mobile communication system can economically be increased. Adaptive Antenna provides a spot beam for each users in the cells as it moves. This paper analysis the comparison of average Bit Error Rate (BER of SDMA and Code Division Multiple Access (CDMAtechnique and the way in which SDMA can be introduced to increase the capacity of a cellular system in Frequency Selective Multipath Rayleigh Fading Channel. The BER is found for a standard omni directional base station antenna, and the another set of curve is found for flat top beam having a directivity of 8 dB. We see that SDMA offers improved capacity in wireless communication system.
A Novel MLC Scheme with M2-QAM Constellations over AWGN and Rayleigh Fading Channels
Institute of Scientific and Technical Information of China (English)
YUANDongfeng; ZHANGPeng; WayneE.Stark
2003-01-01
Optimal multilevel codes (MLC) with M2-QAM constellations are considered with focus on both AWGN and Rayleigh fading channels. With the proposition of three new set partitioning rules for M2-QAM constellations, a novel simplified MLC scheme with a very simple MSD (Multistage decoding) structure comes into being, which is operated on the capacity rule. Compared with traditional MLC/MSD scheme the new MLC/MSD structure greatly reduces the calculation of the individual capacities in MLC system because the new set partitioning rules ensure the independency of two dimensions symbols. Furthermore the new MLC/MSD system cannot enhance any performance loss and the time delay is just 1/2 of that with traditional partitioning rules. As an example 64-QAM constellation with three new set partitioning rules are provided. Their performance is simulated over AWGN and Rayleigh fading channels by choosing BCH codes as the component codes.
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Gaoning He
2010-01-01
Full Text Available A Bayesian game-theoretic model is developed to design and analyze the resource allocation problem in K-user fading multiple access channels (MACs, where the users are assumed to selfishly maximize their average achievable rates with incomplete information about the fading channel gains. In such a game-theoretic study, the central question is whether a Bayesian equilibrium exists, and if so, whether the network operates efficiently at the equilibrium point. We prove that there exists exactly one Bayesian equilibrium in our game. Furthermore, we study the network sum-rate maximization problem by assuming that the users coordinate according to a symmetric strategy profile. This result also serves as an upper bound for the Bayesian equilibrium. Finally, simulation results are provided to show the network efficiency at the unique Bayesian equilibrium and to compare it with other strategies.
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.
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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.
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.
Performance of Adaptive Subchannel Assignment-Based MIMO/OFDM Systems over Multipath Fading Channels
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Adaptive antenna arrays at both the base and mobile stations can further increase system capacity and improve the quality of service of conventional orthogonal frequency division multiplexing (OFDM) systems. Conventional adaptive antenna array-based multiple-input multiple-output (MIMO)/OFDM systems use the sub-carriers characterized by the largest eigenvalue to transmit the OFDM symbols. This paper describes the performance of adaptive subchannel assignment-based MIMO/OFDM systems over multipath fading channels. The system adaptively selects the eigenvectors associated with the relatively large subchannel eigenvalues to generate the antenna array weights at the base and mobile stations and then adaptively assigns the corresponding best subchannels to transmit the OFDM symbols. Simulation results show that the proposed system can achieve better performance than the conventional adaptive antenna array-based MIMO/OFDM system over multipath fading channels.
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.
On the Eavesdropper's Correct Decision in Gaussian and Fading Wiretap Channels Using Lattice Codes
Ernvall-Hytönen, Anne-Maria
2011-01-01
In this paper, the probability of Eve the Eavesdropper's correct decision is considered both in the Gaussian and Rayleigh fading wiretap channels when using lattice codes for the transmission. First, it is proved that the secrecy function determining Eve's performance attains its maximum at y=1 on all known extremal even unimodular lattices. This is a special case of a conjecture by Belfiore and Sol\\'e. Further, a very simple method to verify or disprove the conjecture on any given unimodular lattice is given. Second, preliminary analysis on the behavior of Eve's probability of correct decision in the fast fading wiretap channel is provided. More specifically, we compute the truncated inverse norm power sum factors in Eve's probability expression. The analysis reveals a performance-secrecy-complexity tradeoff: relaxing on the legitimate user's performance can significantly increase the security of transmission. The confusion experienced by the eavesdropper may be further increased by using skewed lattices, bu...
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.
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.
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.
BER Performance of Frequency Domain Differential Demodulation OFDM in Flat Fading Channel
Institute of Scientific and Technical Information of China (English)
SONG Lijun; TANG Youxi; LI Shaoqian; HUANG Shunji
2003-01-01
A closed form expression for the bit error rate (BER) performance of frequency domain differential demodulation(FDDD) for orthogonal frequency division multiplexing system in flat fading channel is derived. The performance is evaluated by computer simulation and compared with the time domain differential demodulation(TDDD). The results indicate that the performance of FDDD is better than that of TDDD, and the lower band of BER in the former is lower than that of the latter.
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.
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.
On the performance analysis of SSC diversity system over η-μ fading channels
Khatalin, Sari
2016-06-01
In this paper, we study key performance measures of dual-branch switch-and-stay combining (SSC) system operating in ? fading environment. Specifically, analytical expressions for the kth order moment, average signal-to-noise ratio, amount of fading and outage probability are obtained for an SSC system operating over ? fading channels. Expressions of the average bit error rate (BER) for coherent detection and non-coherent detection were also derived with SSC for various modulation schemes. The BER expressions for the coherent detection case were derived using the moment generating function-based approach. Some of the final expressions are presented in the form of infinite series. Therefore, those series are truncated and upper bounds are derived for truncation errors. Expressions to determine the optimum adaptive switching thresholds are also presented. Corresponding results for Nakagami-q and Nakagami-m fading are derived in this paper as special cases. Numerical results are provided to demonstrate the applications of the new results.
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.
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.
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.
Joint Power and Resource Allocation for Block-Fading Relay-Assisted Broadcast Channels
Shaqfeh, Mohammad
2012-01-01
We provide the solution for optimizing the power and resource allocation over block-fading relay-assisted broadcast channels in order to maximize the long term average achievable rates region of the users. The problem formulation assumes regenerative (repetition coding) decode-and-forward (DF) relaying strategy, long-term average total transmitted power constraint, orthogonal multiplexing of the users messages within the channel blocks, possibility to use a direct transmission (DT) mode from the base station to the user terminal directly or a relaying (DF) transmission mode, and partial channel state information. We show that our optimization problem can be transformed into an equivalent "no-relaying" broadcast channel optimization problem with each actual user substituted by two virtual users having different channel qualities and multiplexing weights. The proposed power and resource allocation strategies are expressed in closed-form that can be applied practically in centralized relay-assisted wireless netw...
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.
Secure Broadcasting over Fading Channels with Statistical QoS Constraints
Qiao, Deli; Velipasalar, Senem
2010-01-01
In this paper, the fading broadcast channel with confidential messages is studied in the presence of statistical quality of service (QoS) constraints in the form of limitations on the buffer length. We employ the effective capacity formulation to measure the throughput of the confidential and common messages. We assume that the channel side information (CSI) is available at both the transmitter and the receivers. Assuming average power constraints at the transmitter side, we first define the effective secure throughput region, and prove that the throughput region is convex. Then, we obtain the optimal power control policies that achieve the boundary points of the effective secure throughput region.
Capacity of Fading Gaussian Channel with an Energy Harvesting Sensor Node
Rajesh, R
2010-01-01
Network life time maximization is becoming an important design goal in wireless sensor networks. Energy harvesting has recently become a preferred choice for achieving this goal as it provides near perpetual operation. We study such a sensor node with an energy harvesting source and compare various architectures by which the harvested energy is used. We find its Shannon capacity when it is transmitting its observations over a fading AWGN channel with perfect/no channel state information provided at the transmitter. We also obtain the capacity with a finite energy buffer via Markov decision theory.
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.
Multiple trellis coded modulation (MTCM) performance on a fading mobile satellite channel
Simon, Marvin K.; Divsalar, Dariush
1987-01-01
The author recently introduced the notion of multiple trellis coding, in which more than one channel symbol per trellis branch is transmitted. He showed that on the ideal additive white Gaussian noise (AWGN) channel, the combination of multiple trellis coding with M-ary modulation yields a performance gain with symmetric signal sets comparable to and in some cases better than that previously achieved only with signal constellation asymmetry. The combination of conventional trellis coding with multiple phase-shift-keyed (MPSK) signaling has recently been shown by the author to be a well-suited modulation/coding scheme for transmission over the fading mobile satellite channel. In particular, a rate 2/3 coded 8-PSK scheme operating at 4800 b/s is currently under development for use in NASA's Mobile Satellite Experiment (MSAT-X). The author applies the multiple trellis-coded modulation technique in the same fading mobile satellite environment, extending the analysis results previously found for its performance over the AWGN channel to the MSAT-X channel.
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.
Ergodic and Outage Performance of Fading Broadcast Channels with 1-Bit Feedback
Niu, Bo; Somekh, Oren; Haimovich, Alexander M
2010-01-01
In this paper, the ergodic sum-rate and outage probability of a downlink single-antenna channel with K users are analyzed in the presence of Rayleigh flat fading, where limited channel state information (CSI) feedback is assumed. Specifically, only 1-bit feedback per fading block per user is available at the base station. We first study the ergodic sum-rate of the 1-bit feedback scheme, and consider the impact of feedback delay on the system. A closed-form expression for the achievable ergodic sum-rate is presented as a function of the fading temporal correlation coefficient. It is proved that the sum-rate scales as loglogK, which is the same scaling law achieved by the optimal non-delayed full CSI feedback scheme. The sum-rate degradation due to outdated CSI is also evaluated in the asymptotic regimes of either large K or low SNR. The outage performance of the 1-bit feedback scheme for both instantaneous and outdated feedback is then investigated. Expressions for the outage probabilities are derived, along w...
Djordjevic, Goran T.; Antic, Dragan
2013-12-01
In this paper, the outage performance of a dual-branch switch and stay combining (SSC) diversity receiver operating over composite multipath Nakagami-m fading/gamma shadowing channels in the presence of a co-channel interference is determined. For a single channel composite fading environment, we derive the new analytical expressions for the probability density function and cumulative distribution function of the instantaneous signal-to-interference (SIR) ratio that can be used as alternatives to the previously published results. In the case of non-identically distributed and power unbalanced SSC branches with arbitrary fading parameters, the outage performance is determined. The choice of optimal switching threshold in minimum outage probability sense is discussed. The results show the outage probability dependence on simultaneous effects of the SIR unbalancing, as well as multipath fading and shadowing severities. The analytical results are confirmed by Monte Carlo simulations.
Performance of RCPC-Encoded V-BLAST MIMO In Nakagami-m Fading Channel
Sari, L; Gunawan, D
2010-01-01
Multiple Input Multiple Output (MIMO) wireless communication link has been theoretically proven to be reliable and capable of achieving high capacity. However, these two advantageous characteristics tend to be addressed separately in many major researches. Researches on various approaches to attain both characteristics in a single MIMO system are still on-going and an established approach is yet to be concluded. To address this problem, in this paper a Vertical Bell Laboratories Layered Space-Time (V-BLAST) MIMO enhanced with Rate-Compatible Convolutional (RCPC) codes with Zero Forcing (ZF) and Minimum Mean Squared Error (MMSE)-based detection is proposed. The analytical BER of the system is presented and numerically analyzed. The system performance is analyzed in Nakagami-m fading channel, which provides accuracy and flexibility in matching the signals statistics compared to other fading models. The complexity which arises in the calculations of the RCPC codes parameters is significantly reduced by using equ...
Alternative Awaiting and Broadcast for Two-Way Relay Fading Channels
Liu, Jianquan; Tao, Meixia
2011-01-01
We investigate a two-way relay (TWR) fading channel based on store-and-forward (SF), where two source nodes wish to exchange information with the help of a relay node. A new upper bound on the ergodic sum-capacity for the TWR fading system is derived when delay tends to infinity.We further propose two alternative awaiting and broadcast (AAB) schemes: pure partial decoding (PPD) with SF-I and combinatorial decoding (CBD) with SF-II, which approach the new upper bound at high SNR with unbounded and bounded delay respectively. Numerical results show that the proposed AAB schemes significantly outperform the traditional physical layer network coding (PLNC) methods without delay. Compared to the traditional TWR schemes without delay, the proposed CBD with SF-II method significantly improves the maximum sum-rate with an average delay of only some dozen seconds in the relay buffer.
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.
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.
Optimal Training for Time-Selective Wireless Fading Channels Using Cutoff Rate
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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.
Spectral Efficiency of Multiple Access Fading Channels with Adaptive Interference Cancellation
Shakya, Indu L
2012-01-01
Reliable estimation of users' channels and data in rapidly time varying fading environments is a very challenging task of multiuser detection (MUD) techniques that promise impressive capacity gains for interference limited systems such as non-orthogonal CDMA and spatial multiplexing MIMO based LTE. This paper analyzes relative channel estimation error performances of conventional single user and multiuser receivers for an uplink of DS-CDMA and shows their impact on output signal to interference and noise ratio (SINR) performances. Mean squared error (MSE) of channel estimation and achievable spectral efficiencies of these receivers obtained from the output SINR calculations are then compared with that achieved with new adaptive interference canceling receivers. It is shown that the adaptive receivers using successive (SIC) and parallel interference cancellation (PIC) methods offer much improved channel estimation and SINR performances, and hence significant increase in achievable sum date rates.
A Novel Simulator of Nonstationary Random MIMO Channels in Rayleigh Fading Scenarios
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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.
A Novel Statistical Channel Model for Turbulence-Induced Fading in Free-Space Optical Systems
Aminikashani, Mohammadreza; Kavehrad, Mohsen
2015-01-01
In this paper, we propose a new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions. The proposed model, termed Double Generalized Gamma (Double GG), is based on a doubly stochastic theory of scintillation and developed via the product of two Generalized Gamma (GG) distributions. The proposed Double GG distribution generalizes many existing turbulence channel models and provides an excellent fit to the published plane and spherical waves simulation data. Using this new statistical channel model, we derive closed form expressions for the outage probability and the average bit error as well as corresponding asymptotic expressions of free-space optical communication systems over turbulence channels. We demonstrate that our derived expressions cover many existing results in the literature earlier reported for Gamma-Gamma, Double-Weibull and K channels as special cases.
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.
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.
Joda, Roghayeh
2012-01-01
In this paper, delay-limited transmission of quasi-stationary sources over block fading channels are considered. Considering distortion outage probability as the performance measure, two source and channel coding schemes with power adaptive transmission are presented. The first one is optimized for fixed rate transmission, and hence enjoys simplicity of implementation. The second one is a high performance scheme, which also benefits from optimized rate adaptation with respect to source and channel states. In high SNR regime, the performance scaling laws in terms of outage distortion exponent and asymptotic outage distortion gain are derived, where two schemes with fixed transmission power and adaptive or optimized fixed rates are considered as benchmarks for comparisons. Various analytical and numerical results are provided which demonstrate a superior performance for source and channel optimized rate and power adaptive scheme. It is also observed that from a distortion outage perspective, the fixed rate adap...
Applications of Tauberian Theorem for High-SNR Analysis of Performance over Fading Channels
Zhang, Yuan
2011-01-01
This paper derives high-SNR asymptotic average error rates over fading channels by relating them to the outage probability, under mild assumptions. The analysis is based on the Tauberian theorem for Laplace transforms which is grounded on the notion of regular variation, and applies to a wider range of channel distributions than existing approaches. The theory of regular variation is argued to be the proper mathematical framework for finding sufficient and necessary conditions for outage events to dominate high-SNR error rate performance. It is proved that the diversity order being $d$ and the cumulative distribution function (CDF) of the channel power gain having variation exponent $d$ at 0 imply each other, provided that the instantaneous error rate is upper-bounded by an exponential function of the instantaneous SNR. High-SNR asymptotic average error rates are derived for specific instantaneous error rates. Compared to existing approaches in the literature, the asymptotic expressions are related to the cha...
Analysis of Energy Efficiency in Fading Channels under QoS Constraints
Gursoy, Mustafa Cenk; Velipasalar, Senem
2008-01-01
Energy efficiency in fading channels in the presence of Quality of Service (QoS) constraints is studied. Effective capacity, which provides the maximum arrival rate that a wireless channel can sustain while satisfying statistical QoS constraints, is considered. Spectral efficiency--bit energy tradeoff is analyzed in the low-power and wideband regimes by employing the effective capacity formulation, rather than the Shannon capacity. Through this analysis, energy requirements under QoS constraints are identified. The analysis is conducted under two assumptions: perfect channel side information (CSI) available only at the receiver and perfect CSI available at both the receiver and transmitter. In particular, it is shown in the low-power regime that the minimum bit energy required under QoS constraints is the same as that attained when there are no such limitations. However, this performance is achieved as the transmitted power vanishes. Through the wideband slope analysis, the increased energy requirements at lo...
Transmission Strategies in Multiple Access Fading Channels with Statistical QoS Constraints
Qiao, Deli; Velipasalar, Senem
2010-01-01
Effective capacity, which provides the maximum constant arrival rate that a given service process can support while satisfying statistical delay constraints, is analyzed in a multiuser scenario. In particular, the effective capacity region of fading multiple access channels (MAC) in the presence of quality of service (QoS) constraints is studied. Perfect channel side information (CSI) is assumed to be available at both the transmitters and the receiver. It is initially assumed the transmitters send the information at a fixed power level and hence do not employ power control policies. Under this assumption, the performance achieved by superposition coding with successive decoding techniques is investigated. It is shown that varying the decoding order with respect to the channel states can significantly increase the achievable throughput region. In the two-user case, the optimal decoding strategy is determined for the scenario in which the users have the same QoS constraints. The performance of orthogonal trans...
Directory of Open Access Journals (Sweden)
Lingyang Song
2008-05-01
Full Text Available We propose double-differential (DD modulation for the amplify-and-forward protocol over Nakagami-m fading channels with carrier offsets. We propose an emulated maximum ratio combining (EMRC decoder, which could be used by the double-differential receiver in the absence of exact channel knowledge. Approximate bit error rate (BER analysis is performed for the proposed double-differential modulation-based cooperative communication system. The proposed double-differential system is immune to random carrier offsets, whereas the conventional single-differential modulation-based cooperative system breaks down. In addition, the proposed scheme is able to perform better than the same rate training-based cooperative system which utilizes training data for finding estimates of carrier offsets and channel gains.
On the Achievable Rate of Stationary Rayleigh Flat-Fading Channels with Gaussian Inputs
Dörpinghaus, Meik
2011-01-01
In this work, we consider a discrete-time stationary Rayleigh flat-fading channel with unknown channel state information at transmitter and receiver. The law of the channel is presumed to be known to the receiver. In addition, we assume the power spectral density (PSD) of the fading process to be compactly supported. For i.i.d. zero-mean proper Gaussian input distributions, we investigate the achievable rate. One of the main contributions is the derivation of two new upper bounds on the achievable rate with zero-mean proper Gaussian input symbols. The first one holds only for the special case of a rectangular PSD and depends on the SNR and the spread of the PSD. Together with a lower bound on the achievable rate, which is achievable with i.i.d. zero-mean proper Gaussian input symbols, we have found a set of bounds which is tight in the sense that their difference is bounded. Furthermore, we show that the high SNR slope is characterized by a pre-log of 1-2f_d, where f_d is the normalized maximum Doppler freque...
Joint Network Coding and Opportunistic Transmission for Two-Way Relay Fading Channels
Liu, Jianquan; Xu, Youyun
2011-01-01
We investigate a two-way relay (TWR) fading channel where two source nodes wish to exchange information with the help of a relay node. The capacity of two-way relaying is known to be limited by the hop with weak channel condition due to immediate forwarding. In this paper, we introduce store-andforward (SF) relay protocol and present a joint network coding and opportunistic transmission (NCOT) for TWR channel. Through the use of NCOT method, a new upper bound on the ergodic sum-capacity for the TWR fading system is derived when delay tends to infinity. We further propose two alternative awaiting and broadcast (AAB) schemes: pure partial decoding (PPD) with SF-I and combinatorial decoding (CBD) with SF-II, which approach the new upper bound at high SNR with unbounded and bounded delay respectively. Numerical results show that the proposed AAB schemes significantly outperform the traditional physical layer network coding (PLNC) methods without delay. Compared to the traditional TWR schemes without delay, the pr...
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.
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.
GENETIC ALGORITHM FOR DECODING LINEAR CODES OVER AWGN AND FADING CHANNELS
Directory of Open Access Journals (Sweden)
H. BERBIA
2011-08-01
Full Text Available This paper introduces a decoder for binary linear codes based on Genetic Algorithm (GA over the Gaussian and Rayleigh flat fading channel. The performances and compututional complexity of our decoder applied to BCH and convolutional codes are good compared to Chase-2 and Viterbi algorithm respectively. It show that our algorithm is less complex for linear block codes of large block length; furthermore it's performances can be improved by tuning the decoder's parameters, in particular the number of individuals by population and the number of generations
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 l...... 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....
Statistical Analysis of Multipath Fading Channels Using Generalizations of Shot Noise
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Djouadi SeddikM
2008-01-01
Full Text Available Abstract This paper provides a connection between the shot-noise analysis of Rice and the statistical analysis of multipath fading wireless channels when the received signals are a low-pass signal and a bandpass signal. Under certain conditions, explicit expressions are obtained for autocorrelation functions, power spectral densities, and moment-generating functions. In addition, a central limit theorem is derived identifying the mean and covariance of the received signals, which is a generalization of Campbell_s theorem. The results are easily applicable to transmitted signals which are random and to CDMA signals.
Performance Analysis of Iterative Decoding Algorithms for PEG LDPC Codes in Nakagami Fading Channels
Directory of Open Access Journals (Sweden)
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.
Institute of Scientific and Technical Information of China (English)
Ma Piming; Yuan Dongfeng
2005-01-01
If the degree distribution is chosen carefully, the irregular low-density parity-check (LDPC) codes can outperform the regular ones. An image transmission system is proposed by combining regular and irregular LDPC codes with 16QAM/64QAM modulation to improve both efficiency and reliability. Simulaton results show that LDPC codes are good coding schemes over fading channel in image communication with lower system complexity. More over, irregular codes can obtain a code gain of about 0.7 dB compared with regular ones when BER is 10-4. So the irregular LDPC codes are more suitable for image transmission than the regular codes.
Capacity of MIMO LAS-CDMA System Under Correlating Multi-Path Fading Channels
Institute of Scientific and Technical Information of China (English)
WANG Jun-xuan; RAO Wen-yuan; LI Dao-ben
2005-01-01
Capacity of MIMO LAS-CDMA systems under multi-path fading channels with two different correlating models were studied in the paper. Influences of the two models parameters on capacity were analyzed. The numerical results present that: according to the Various Scattering Environments correlating model, when the inner-elements distance of antennas array is large than 0.5λ, correlation almost does not take from the system capacity; for the Salz-Winter correlating model, the spread angle at receiver is the other key factor, it also influence the system capacity greatly.
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.
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.
Performance analysis of adaptive M-QAM over a flat-fading Nakagami-m channel
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Tahmid Quazi
2011-01-01
Full Text Available Channel adaptive M-ary quadrature amplitude modulation (M-QAM schemes have been developed to provide higher average link spectral efficiency by taking advantage of the time-varying nature of wireless fading channels. Much of the earlier work on such schemes uses the assumption that thresholds designed for additive white Gaussian noise (AWGN channels can be directly applied to slowly varying block-fading channels. The thresholds are calculated with a commonly used approximation bit error rate (BER expression in these schemes. The first aim of this paper was to investigate the accuracy of using this common BER expression in a fading channel. This was done by comparing the result of the average BER expression derived using the approximate expression with results of simulations over a Nakagami-m block-fading channel. The second aim was to show that the inaccuracy in the threshold values determined using the closed form approximation expression would lead to inappropriate operation of the adaptive M-QAM scheme in a fading channel. This was done by comparing expected theoretical values with the simulation results. Two alternative approximate BER expressions for M-QAM in AWGN were then presented and used to determine the average M-QAM of BER over a Nakagami-m fading channel. The comparison between the average BER expressions and the simulation showed a much closer match. More accurate thresholds for the adaptive M-QAM system were then determined using one of the two average BER expressions and the accuracy of these threshold points was then verified using simulation results.
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.
ERASED-CHASE DECODING FOR RS-CODED MPSK SIGNALING OVER A RAYLEIGH FADING CHANNEL
Institute of Scientific and Technical Information of China (English)
Xu Chaojun; Sun Yue; Wang Xinmei
2007-01-01
In this paper,a novel dual-metric,the maximum and minimum Squared Euclidean Distance Increment(SEDI)brought by changing the hard decision symbol,is introduced to measure the reliability of the received M-ary Phase Shift Keying(MPSK)symbols over a Rayleigh fading channel.Based on the dual-metric,a Chase-type soft decoding algorithm,which is called erased-Chase algorithm,is developed for Reed-Solomon(RS)coded MPSK schemes.The proposed algorithm treats the unreliable symbols with small maximum SEDI as erasures,and tests the non-erased unreliable symbols with small minimum SEDI as the Chase-2 algorithm does.By introducing optimality test into the decoding procedure,much more reduction in the decoding complexity can be achieved.Simulation results of the RS(63,42,22)-coded 8-PSK scheme over a Rayleigh fading channel show that the proposed algorithm provides a very efficient tradeoff between the decoding complexity and the error performance.Finally,an adaptive scheme for the number of erasures is introduced into the decoding algorithm.
Directory of Open Access Journals (Sweden)
K.Kavitha
2014-03-01
Full Text Available Multilevel Space Time Trellis Coded Modulation with antenna grouping, which has been proposed recently, has coding gain and diversity gain, which in turn provide high throughput with considerable low computational complexity. However its performance is limited by predefining the antenna groups per component codes. In this paper Multilevel Spatial Multiplexing-Space Time Trellis Coded Modulation (ML-SM-STTCM has been proposed, in which antenna group selection is made based on spatial modulation based on trellis coding proposed by Ertugrul Basar and team. This idea maximizes the spatial diversity. Since only selected antennas are used to transmit the signal, and also the antennas with less cross correlation are in the selected groups, we could able to achieve improved BER performance even in the fast fading channel. Since the antenna selection is based on the component code in the system, at the decoder without increase in the computational complexity, we could achieve better error performance. The performance of the proposed system is analysed with Viterbi decoding algorithm and sub optimal sequential decoding algorithm. In this system, the antenna groups are non-overlapping, hence, it needs Nt, the number transmitter antennas, more than what is required at time t. The computer simulation reveals that the proposed system gives better BER performance compared to Multilevel Space Time Trellis Coded Modulation (ML STTCM over fast fading channel with the same computational complexity both at the transmitter and receiver.
Kang, Xin; Nallanathan, Arumugam; Garg, Hari Krishna; Zhang, Rui
2008-01-01
A cognitive radio network (CRN) is formed by either allowing the secondary users (SUs) in a secondary communication network (SCN) to opportunistically operate in the frequency bands originally allocated to a primary communication network (PCN) or by allowing SCN to coexist with the primary users (PUs) in PCN as long as the interference caused by SCN to each PU is properly regulated. In this paper, we consider the latter case, known as spectrum sharing, and study the optimal power allocation strategies to achieve the ergodic capacity and the outage capacity of the SU fading channel under different types of power constraints and fading channel models. In particular, besides the interference power constraint at PU, the transmit power constraint of SU is also considered. Since the transmit power and the interference power can be limited either by a peak or an average constraint, various combinations of power constraints are studied. It is shown that there is a capacity gain for SU under the average over the peak ...
Performance Analysis of Ad Hoc Dispersed Spectrum Cognitive Radio Networks over Fading Channels
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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.
Joint Scheduling for Dual-Hop Block-Fading Broadcast Channels
Ammar, Zafar
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.
Power Allocation for Discrete-Input Non-Ergodic Block-Fading Channels
Nguyen, Khoa D; Rasmussen, Lars K
2007-01-01
We consider power allocation algorithms for fixed-rate transmission over Nakagami-m non-ergodic block-fading channels with perfect transmitter and receiver channel state information and discrete input signal constellations under both short- and long-term power constraints. Optimal power allocation schemes are shown to be direct applications of previous results in the literature. We show that the SNR exponent of the optimal short-term scheme is given by the Singleton bound. We also illustrate the significant gains available by employing long-term power constraints. Due to the nature of the expressions involved, the complexity of optimal schemes may be prohibitive for system implementation. We propose simple sub-optimal power allocation schemes whose outage probability performance is very close to the minimum outage probability obtained by optimal schemes.
A Concatenated ML Decoder for ST/SFBC-OFDM Systems in Double Selective Fading Channels
Institute of Scientific and Technical Information of China (English)
李明齐; 张文军
2004-01-01
This paper presented a concatenated maximum-likelihood (ML) decoder for space-time/space-frequency block coded orthogonal frequency diversion multiplexing (ST/SFBC-OFDM) systems in double selective fading channels. The proposed decoder first detects space-time or space-frequency codeword elements separately. Then, according to the coarsely estimated codeword elements, the ML decoding is performed in a smaller constellation element set to searching final codeword. It is proved that the proposed decoder has optimal performances if and only if subchannels are constant during a codeword interval. The simulation results show that the performances of proposed decoder is close to that of the optimal ML decoder in severe Doppler and delay spread channels. However, the complexity of proposed decoder is much lower than that of the optimal ML decoder.
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.
Zhao, Zhijun; Liao, Rui
2011-03-01
Free-space optical (FSO) communication systems suffer from average power loss and instantaneous power fading due to the atmospheric turbulence. The channel fading probability density function (pdf) is of critical importance for FSO communication system design and evaluation. The performance and reliability of FSO communication systems can be greatly enhanced if fast-tacking devices are employed at the transmitter in order to compensate laser beam wander at the receiver aperture. The fast-tracking method is especially effective when communication distance is long. This paper studies the fading probability density functions of both fast-tracked and untracked FSO communication channels. Large-scale wave-optics simulations are conducted for both tracked and untracked lasers. In the simulations, the Kolmogorov spectrum is adopted, and it is assumed that the outer scale is infinitely large and the inner scale is negligibly small. The fading pdfs of both fast-tracked and untracked FSO channels are obtained from the simulations. Results show that the fast-tracked channel fading can be accurately modeled as gamma-distributed if receiver aperture size is smaller than the coherence radius. An analytical method is given for calculating the untracked fading pdfs of both point-like and finite-size receiver apertures from the fast-tracked fading pdf. For point-like apertures, the analytical method gives pdfs close to the well-known gamma-gamma pdfs if off-axis effects are omitted in the formulation. When off-axis effects are taken into consideration, the untracked pdfs obtained using the analytical method fit the simulation pdfs better than gamma-gamma distributions for point-like apertures, and closely fit the simulation pdfs for finite-size apertures where gamma-gamma pdfs deviate from those of the simulations significantly.
Repeat-punctured superorthogonal convolutional turbo codes on AWGN and flat Rayleigh fading channels
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Fambirai Takawira
2010-10-01
Full Text Available Repeat-punctured turbo codes, an extension of the conventional turbo-coding scheme, has shown a significant increase in bit-error rate performance at moderate to high signal-to-noise ratios for short frame lengths. Superorthogonal convolutional turbo codes (SCTC makes use of superorthogonal signals to improve the performance of the conventional turbo codes and a coding scheme that applies the repeat-punctured technique into SCTC has shown to perform better. We investigated two new low-rate coding schemes, repeat-punctured superorthogonal convolutional turbo codes (RPSCTC and dual-repeat-punctured superorthogonal convolutional turbo codes (DRPSCTC, that make use of superorthogonal signaling, together with repetition and puncturing, to improve the performance of SCTC for reliable and effective communications. Simulation results in the additive white Gaussian noise (AWGN channel and the frequency non-selective Rayleigh fading channel are presented together with analytical bounds of bit error probabilities, derived from transfer function bounding techniques. From the simulation results and the analytical bounds presented, it is evident that RPSCTC and DRPSCTC offer a more superior performance than SCTC in the AWGN channel, as well as in flat Rayleigh non-line-of-sight fading channels. The distance spectrum is also presented for the new schemes and accounts for the performance improvement rendered in simulations. It is important to note that the improved performance that SCTC, and consequently RPSCTC and DRPSCTC, exhibit is achieved at the expense of bandwidth expansion and complexity and would be ideal for power-limited satellite communication links or interference-limited systems.
Javed, Umer; He, Di; Liu, Peilin
2016-08-05
The transmission of signals in a hybrid satellite-terrestrial system (HSTS) in the presence of co-channel interference (CCI) is considered in this study. Specifically, we examine the problem of amplify-and-forward (AF)-based relaying in a hybrid satellite-terrestrial link, where the relay node is operating in the presence of a dominant co-channel interferer. It is assumed that direct connection between a source node (satellite) and a destination node (terrestrial receiver) is not available due to masking by obstacles in the surrounding. The destination node is only able to receive signals from the satellite with the help of a relay node located at the ground. In the proposed HSTS, the satellite-relay channel follows the shadowed Rice fading; and the channels of interferer-relay and relay-destination links experience generalized Nakagami-m fading. For the considered AF-based HSTS, we first develop the analytical expression for the moment generating function (MGF) of the overall output signal-to-interference-plus-noise ratio (SINR). Then, based on the derived exact MGF, we derive novel expressions for the average symbol error rate (SER) of the considered HSTS for the following digital modulation techniques: M-ary phase shift keying (M-PSK), M-ary quadrature amplitude modulation (M-QAM) and M-ary pulse amplitude modulation (M-PAM). To significantly reduce the computational complexity for utility in system-level simulations, simple analytical approximation for the exact SER in the high signal-to-noise ratio (SNR) regime is presented to provide key insights. Finally, numerical results and the corresponding analysis are presented to demonstrate the effectiveness of the developed performance evaluation framework and to view the impact of CCI on the considered HSTS under varying channel conditions and with different modulation schemes.
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.
Institute of Scientific and Technical Information of China (English)
Xiang Zheng; Zhang Taiyi; Sun Jiancheng
2006-01-01
A new strategy for noise reduction of fast fading channel is presented. Firstly, more information is acquired utilizing the reconstructed embedding phase space. Then, based on the Recurrent Least Squares Support Vector Machines (RLS-SVM), noise reduction of the fast fading channel is realized. This filtering technique does not make use of the spectral contents of the signal. Based on the stability and the fractal of the chaotic attractor, the RLS-SVM algorithm is a better candidate for the nonlinear time series noise-reduction. The simulation results shows that better noise-reduction performance is acquired when the signal to noise ratio is 12dB.
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.
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.
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.
Pairwise Check Decoding for LDPC Coded Two-Way Relay Block Fading Channels
Liu, Jianquan; Xu, Youyun
2011-01-01
Partial decoding is known to have the potential to achieve a larger rate region than that of full decoding in two-way relay (TWR) channels. Existing partial decoding realizations are however designed for Gaussian channels and with a static physical layer network coding (PLNC) mapping. In this paper, we propose a new channel coding solution at the relay, called \\emph{pairwise check decoding} (PCD), for low-density parity-check (LDPC) coded TWR system over block fading channels. The main idea is to form a check relationship table (check-relation-tab) for the superimposed LDPC coded packet pair in the multiple access (MA) phase in conjunction with an adaptive PLNC mapping in the broadcast (BC) phase. Using PCD, we then present a partial decoding method, two-stage closest-neighbor clustering with PCD (TS-CNC-PCD), with the aim of minimizing the worst pairwise error performance. Moreover, a kind of correlative rows optimization, named as the minimum correlation optimization (MCO), is proposed for selecting the bet...
Lee, Wooju; Yoon, Dongweon
Cooperative relay selection, in which one of multiple relays is selected to retransmit the source signal to the destination, has received considerable attention in recent years, because it is a simple way to obtain cooperative diversity in wireless networks. The exact expression of outage probability for a decode-and-forward cooperative relay selection with multiple source and destination antennas over Rayleigh fading channels was recently derived in [9]. In this letter, we derive the exact expressions of outage probability and diversity-multiplexing tradeoff over independent and non-identically distributed Nakagami-m fading channels as an extension of [9]. We then analyze the effects of various parameters such as fading conditions, number of relays, and number of source and destination antennas on the outage probability.
Sithamparanathan, Kandeepan; Piesiewicz, Radoslaw
In this paper we study and present some results on the performances of frequency tracking for Ka-band satellite communications in rain fading channels. The carrier frequency is tracked using a 2nd order hyperbolic phase detector based digital-phase locked loop (D-PLL). The hyperbolic D-PLL has the capability of extending the tracking range compared to the other D-PLL and hence can be designed such that to achieve low phase jitter performance for improved carrier tracking. We present the design and analysis of the D-PLL and show some simulation results on the frequency tracking performance for Ka-band rain fading channel. The results are compared with the non-fading noise only case and comparative analyses are made.
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.
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.
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.
Upper Bounds on the BER Performance of MTCM-STBC Schemes over Shadowed Rician Fading Channels
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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.
Performance analysis of ARQ schemes with code combining over Nakagami-m fading channel
Institute of Scientific and Technical Information of China (English)
XU Wen-bo; NIU Kai; LIN Jia-ru; HE Zhi-qiang
2009-01-01
This article investigates the performance of hybrid automatic repeat request (HARQ) with code combining over the ideally interleaved Nakagami-m fading channel. Two retransmission protocols with coherent equal gain code combining are adopted, where the entire frame and several selected portions of the frame are repeated in protocols Ⅰ and Ⅱ, respectively. Protocol Ⅱ could be viewed as a generalization of the recently proposed reliability-based HARQ. To facilitate performance analysis, an approximation of the product of two independent Nakagami-m distributed random variables is first developed. Then the approximate analysis is utilized to obtain exact frame error probability (FEP) for protocol Ⅰ, and the upper bound of the FEP for protocol Ⅱ. Furthermore, the throughput performance of both two protocols is presented. Simulation results show the reliability of the theoretical analysis, where protocol Ⅱ outperforms protocol Ⅰ in the throughput performance due to the reduced amount of transmitted information.
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.
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.
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.
Performance of Hybrid Concatenated Trellis Codes CPFSK with Iterative Decoding over Fading Channels
Gergis, Labib Francis
2011-01-01
Concatenation is a method of building long codes out of shorter ones, it attempts to meet the problem of decoding complexity by breaking the required computation into manageable segments. Concatenated Continuous Phase Frequency Shift Keying (CPFSK) facilitates powerful error correction. CPFSK also has the advantage of being bandwidth efficient and compatible with nonlinear amplifiers. Bandwidth efficient concatenated coded modulation schemes were designed for communication over Additive White Gaussian noise (AWGN), and Rayleigh fading channels. An analytical bounds on the performance of serial concatenated convolutional codes (SCCC), and parallel concatenated convolutionalcodes (PCCC), were derived as a base of comparison with the third category known as hybrid concatenated trellis codes scheme (HCTC). An upper bound to the average maximum-likelihood bit error probability of the three schemes were obtained. Design rules for the parallel, outer, and inner codes that maximize the interleaver's gain were discuss...
MPSK Symbol-based Soft-Information-Forwarding Scheme in Rayleigh Fading Channels
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Huamei Xin
2014-06-01
Full Text Available In this paper, we proposed a symbol-based multiple phase shift keying (MPSK soft-information-forwarding (SIF scheme for a two-hop parallel relay wireless network in Rayleigh fading channel. First the binary information streams at the source are mapped into MPSK symbols, and the relays construct the relay processing function by passing the intermediate soft decisions. Then the relays broadcast the processed symbols to the destination. After the maximum ratio combination, the received symbols at the destination can be decided by maximum-likelihood (ML decision. Four MPSK symbol-based forwarding schemes are investigated and the simulation results show that the bit error rate (BER performance of soft information forwarding scheme has better BER performance than the existing memoryless forwarding scheme based on MPSK modulation, and it is more practical than the SIF scheme based on BPSK modulation
Transmission with Energy Harvesting Nodes in Fading Wireless Channels: Optimal Policies
Ozel, Omur; Yang, Jing; Ulukus, Sennur; Yener, Aylin
2011-01-01
Wireless systems comprised of rechargeable nodes have a significantly prolonged lifetime and are sustainable. A distinct characteristic of these systems is the fact that the nodes can harvest energy throughout the duration in which communication takes place. As such, transmission policies of the nodes need to adapt to these harvested energy arrivals. In this paper, we consider optimization of point-to-point data transmission with an energy harvesting transmitter which has a limited battery capacity, communicating in a wireless fading channel. We consider two objectives: maximizing the throughput by a deadline, and minimizing the transmission completion time of the communication session. We optimize these objectives by controlling the time sequence of transmit powers subject to energy storage capacity and causality constraints. We, first, study optimal offline policies. We introduce a directional water-filling algorithm which provides a simple and concise interpretation of the necessary optimality conditions. ...
On the Achievable Throughput Region of Multiple-Access Fading Channels with QoS Constraints
Qiao, Deli; Velipasalar, Senem
2009-01-01
Effective capacity, which provides the maximum constant arrival rate that a given service process can support while satisfying statistical delay constraints, is analyzed in a multiuser scenario. In particular, we study the achievable effective capacity region of the users in multiaccess fading channels (MAC) in the presence of quality of service (QoS) constraints. We assume that channel side information (CSI) is available at both the transmitters and the receiver, and superposition coding technique with successive decoding is used. When the power is fixed at the transmitters, we show that varying the decoding order with respect to the channel state can significantly increase the achievable throughput region. For a two-user case, we obtain the optimal decoding strategy when the users have the same QoS constraints. Meanwhile, it is shown that time-division multiple-access (TDMA) can achieve better performance than superposition coding with fixed successive decoding order at the receiver side for certain QoS con...
Channel estimation for MIMO-OFDM systems in rapid fading channels%MIMO-OFDM系统中快衰落信道的估计
Institute of Scientific and Technical Information of China (English)
吴赟; 罗汉文; 宋文涛; 黄建国
2007-01-01
A channel estimation approach for orthogonal frequency division multiplexing with multiple-input and multipleoutput(MIMO-OFDM)in rapid fading channels is proposed.This approach combines the advantages of an optimal training sequence based least-square(DLS)algorithm and an expectation-maximization(EM)algorithm.The channels at the training blocks are estimated using an estimator based on the OLS algorithm.To compensate for the fast Rayleigh fading at the data blocks,a time domain based Gaussian interpolation filter is presented.Furthermore,an EM algorithm is introduced to improve the performance of channel estimation by a few iterations.Simulations show that this channel estimation approach can effectively track rapid channel variation.
Liang, Bin; Gunawan, Erry; Law, Choi Look; Teh, Kah Chan
Analytical expressions based on the Gauss-Chebyshev quadrature (GCQ) rule technique are derived to evaluate the bit-error rate (BER) for the time-hopping pulse position modulation (TH-PPM) ultra-wide band (UWB) systems under a Nakagami-m fading channel. The analyses are validated by the simulation results and adopted to assess the accuracy of the commonly used Gaussian approximation (GA) method. The influence of the fading severity on the BER performance of TH-PPM UWB system is investigated.
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.
Fu, Hua
2007-01-01
This paper is concerned with optimum diversity receiver structure and its performance analysis of differential phase shift keying (DPSK) with differential detection over nonselective, independent, nonidentically distributed, Rayleigh fading channels. The fading process in each branch is assumed to have an arbitrary Doppler spectrum with arbitrary Doppler bandwidth, but to have distinct, asymmetric fading power spectral density characteristic. Using 8-DPSK as an example, the average bit error probability (BEP) of the optimum diversity receiver is obtained by calculating the BEP for each of the three individual bits. The BEP results derived are given in exact, explicit, closed-form expressions which show clearly the behavior of the performance as a function of various system parameters.
Fu, Hua
2010-01-01
This paper is concerned with the error performance analysis of binary differential phase shift keying with differential detection over the nonselective, Rayleigh fading channel with combining diversity reception. Space antenna diversity reception is assumed. The diversity branches are independent, but have nonidentically distributed statistics. The fading process in each branch is assumed to have an arbitrary Doppler spectrum with arbitrary Doppler bandwidth. Both optimum diversity reception and suboptimum diversity reception are considered. Results available previously apply only to the case of first and second-order diversity. Our results are more general in that the order of diversity is arbitrary. Moreover, the bit error probability (BEP) result is obtained in an exact, closed-form expression which shows the behavior of the BEP as an explict function of the one-bit-interval fading correlation coefficient at the matched filter output, the mean signal-to-noise ratio per bit per branch and the order of diver...
A Comparative Study of Relaying Schemes with Decode-and-Forward over Nakagami-m Fading Channels
Alexandropoulos, George C; Sofotasios, Paschalis C
2011-01-01
Utilizing relaying techniques to improve performance of wireless systems is a promising avenue. However, it is crucial to understand what type of relaying schemes should be used for achieving different performance objectives under realistic fading conditions. In this paper, we present a general framework for modelling and evaluating the performance of relaying schemes based on the decode-and-forward (DF) protocol over independent and not necessarily identically distributed (INID) Nakagami-m fading channels. In particular, we present closed-form expressions for the statistics of the instantaneous output signal-to-noise ratio of four significant relaying schemes with DF; two based on repetitive transmission and the other two based on relay selection (RS). These expressions are then used to obtain closed-form expressions for the outage probability and the average symbol error probability for several modulations of all considered relaying schemes over INID Nakagami-m fading. Importantly, it is shown that when the...
Frequency selective infrared sensors
Davids, Paul; Peters, David W
2013-05-28
A frequency selective infrared (IR) photodetector having a predetermined frequency band. The exemplary frequency selective photodetector includes: a dielectric IR absorber having a first surface and a second surface substantially parallel to the first surface; an electrode electrically coupled to the first surface of the dielectric IR absorber; and a frequency selective surface plasmonic (FSSP) structure formed on the second surface of the dielectric IR absorber. The FSSP structure is designed to selectively transmit radiation in the predetermined frequency band that is incident on the FSSP structure substantially independent of the angle of incidence of the incident radiation on the FSSP structure.
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.
Outage behavior of slow fading channels with power control using noisy quantized CSIT
Ekbatani, Siavash; Jafarkhani, Hamid
2008-01-01
The topic of this study is the outage behavior of multiple-antenna slow fading channels with quantized feedback and partial power control. A fixed-rate communication system is considered. It is known from the literature that with error-free feedback, the outage-optimal quantizer for power control has a circular structure. Moreover, the diversity gain of the system increases polynomially with the cardinality of the power control codebook. Here, a similar system is studied, but when the feedback link is error-prone. We prove that in the high-SNR regime, the optimal quantizer structure with noisy feedback is still circular and the optimal Voronoi regions are contiguous non-zero probability intervals. Furthermore, the optimal power control codebook resembles a channel optimized scalar quantizer (COSQ), i.e., the Voronoi regions merge with erroneous feedback information. Using a COSQ, the outage performance of the system is superior to that of a no-feedback scheme. However, asymptotic analysis shows that the diver...
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.
Writing on Dirty Paper with Resizing and its Application to Quasi-Static Fading Broadcast Channels
Zhang, Wenyi; Laneman, J Nicholas
2007-01-01
This paper studies a variant of the classical problem of ``writing on dirty paper'' in which the sum of the input and the interference, or dirt, is multiplied by a random variable that models resizing, known to the decoder but not to the encoder. The achievable rate of Costa's dirty paper coding (DPC) scheme is calculated and compared to the case of the decoder's also knowing the dirt. In the ergodic case, the corresponding rate loss vanishes asymptotically in the limits of both high and low signal-to-noise ratio (SNR), and is small at all finite SNR for typical distributions like Rayleigh, Rician, and Nakagami. In the quasi-static case, the DPC scheme is lossless at all SNR in terms of outage probability. Quasi-static fading broadcast channels (BC) without transmit channel state information (CSI) are investigated as an application of the robustness properties. It is shown that the DPC scheme leads to an outage achievable rate region that strictly dominates that of time division.
Power Allocation for Discrete-Input Delay-Limited Fading Channels
Nguyen, Khoa D; Rasmussen, Lars K
2007-01-01
We consider power allocation algorithms for fixed-rate transmission over Nakagami-m non-ergodic block-fading channels with perfect transmitter and receiver channel state information and discrete input signal constellations, under both short- and long-term power constraints. Optimal power allocation schemes are shown to be direct applications of previous results in the literature. We show that the SNR exponent of the optimal short-term scheme is given by m times the Singleton bound. We also illustrate the significant gains available by employing long-term power constraints. In particular, we analyze the optimal long-term solution, showing that zero outage can be achieved provided that the corresponding short-term SNR exponent with the same system parameters is strictly greater than one. Conversely, if the short-term SNR exponent is smaller than one, we show that zero outage cannot be achieved. In this case, we derive the corresponding long-term SNR exponent as a function of the Singleton bound. Due to the natu...
Analysis of 1-bit Output Noncoherent Fading Channels in the Low SNR Regime
Mezghani, Amine
2010-01-01
We consider general multi-antenna fading channels with coarsely quantized outputs, where the channel is unknown to the transmitter and receiver. This analysis is of interest in the context of sensor network communication where low power and low cost are key requirements (e.g. standard IEEE 802.15.4 applications). This is also motivated by highly energy constrained communications devices where sampling the signal may be more energy consuming than processing or transmitting it. Therefore the analog-to-digital converters (ADCs) for such applications should be low-resolution, in order to reduce their cost and power consumption. In this paper, we consider the extreme case of only 1-bit ADC for each receive signal component. We derive asymptotics of the mutual information up to the second order in the signal-to-noise ratio (SNR) under average and peak power constraints and study the impact of quantization. We show that up to second order in SNR, the mutual information of a system with two-level (sign) output signal...
Xu, Yong; Lu, Renquan; Shi, Peng; Li, Hongyi; Xie, Shengli
2016-12-15
This paper considers finite-time distributed state estimation for discrete-time nonlinear systems over sensor networks. The Round-Robin protocol is introduced to overcome the channel capacity constraint among sensor nodes, and the multiplicative noise is employed to model the channel fading. In order to improve the performance of the estimator under the situation, where the transmission resources are limited, fading channels with different stochastic properties are used in each round by allocating the resources. Sufficient conditions of the average stochastic finite-time boundedness and the average stochastic finite-time stability for the estimation error system are derived on the basis of the periodic system analysis method and Lyapunov approach, respectively. According to the linear matrix inequality approach, the estimator gains are designed. Finally, the effectiveness of the developed results are illustrated by a numerical example.
Effects of Time-Variant WSSUS Channel on the Performance of OFDM Systems
Institute of Scientific and Technical Information of China (English)
ZHANG Jie; SU Ling; ZHANG Ping
2004-01-01
The long symbol duration makes Orthogonal Frequency Division Multiplexing (OFDM) robust against frequency-selective fading, and also makes OFDM sensitive to time-selective fading. First, this paper deduces the Inter-subCarrier Interference (ICI) caused by time-selective fading, and then analyzes in detail how time-selective fading affects the performance of OFDM system, e.g. Bit-Error Rate (BER) and the channel capacity of each subcarrier. At last, some simulation figures are given.
Directory of Open Access Journals (Sweden)
Rugini Luca
2010-01-01
Full Text Available We evaluate the probability of error of linearly modulated signals, such as phase-shift keying (PSK and quadrature amplitude modulation (QAM, in the presence of Gaussian cochannel interference (CCI and Rayleigh fading channels. Specifically, we assume that the fading channel of the CCI is maximally correlated with the fading channel of the signal of interest (SOI. In practical applications, the maximal correlation of the CCI channel with the SOI channel occurs when the CCI is generated at the transmitter, such as the multiuser interference in downlink systems, or when a transparent repeater relays some thermal noise together with the SOI. We analytically evaluate the error probability by using a series expansion of generalized hypergeometric functions. A convenient truncation criterion is also discussed. The proposed theoretical approach favorably compares with alternative approaches, such as numerical integration and Monte Carlo estimation. Among the various applications of the proposed analysis, we illustrate the effect of nonlinear amplifiers in orthogonal frequency-division multiplexing (OFDM systems, the downlink reception of code-division multiple-access (CDMA signals, and the outdoor-to-indoor relaying of Global Positioning System (GPS signals.
Institute of Scientific and Technical Information of China (English)
ZOU Yu-long; ZHENG Bao-yu
2008-01-01
MIMO technology proposed in recent years can effectively combat the multipath fading of wireless channel and can considerably enlarge the channel capacity, which has been investigated widely by researchers. However, its performance analysis over correlated block-fading Rayleigh channel is still an open and challenging objective. In this article, an analytic expression of bit error rate (BER) is presented for multiple phase shift keying (MPSK) space-time code, with differential detection over correlated block-fading Rayleigh channel. Through theoretical analysis of BER, it can be found that the differential space-time scheme without the need for channel state information (CSI) at receiver achieves distinct performance gain compared with the traditional nonspace-time system. And then, the system simulation is complimented to verify the above result, showing that the diversity system based on the differential space-time block coding (DSTBC) outperforms the traditional nonspace- time system with diversity gain in terms of BER. Furthermore, the numerical results also demonstrate that the error floor of the differential space-time system is much lower than that of the differential nonspace-time system.
Directory of Open Access Journals (Sweden)
M. Deriche
2008-02-01
Full Text Available A detailed analysis of the multiple access interference (MAI for synchronous downlink CDMA systems is carried out for BPSK signals with random signature sequences in Nakagami-m fading environment with known channel phase. This analysis presents a unified approach as Nakagami-m fading is a general fading distribution that includes the Rayleigh, the one-sided Gaussian, the Nakagami-q, and the Rice distributions as special cases. Consequently, new explicit closed-form expressions for the probability density function (pdf of MAI and MAI plus noise are derived for Nakagami-m, Rayleigh, one-sided Gaussian, Nakagami-q, and Rician fading. Moreover, optimum coherent reception using maximum likelihood (ML criterion is investigated based on the derived statistics of MAI plus noise and expressions for probability of bit error are obtained for these fading environments. Furthermore, a standard Gaussian approximation (SGA is also developed for these fading environments to compare the performance of optimum receivers. Finally, extensive simulation work is carried out and shows that the theoretical predictions are very well substantiated.
Directory of Open Access Journals (Sweden)
Pragya Gupta
2012-09-01
Full Text Available Demands for capacity in wireless communications, driven by cellular mobile, Internet and multimedia services have been rapidly increasing worldwide. On the other hand, the available radio spectrum is limited and the communication capacity needs cannot be met without a significant increase in communication spectral efficiency. Coding techniques designed for multiple antenna transmission are called space-time coding. Space-time coding can achieve transmit diversity and coding gain over spatially uncoded systems without sacrificing the bandwidth. Space-time trellis code (STTC has been widely applied to coded multiple-input multiple-output (MIMO systems because of its gains in coding and diversity. Diversity techniques are used to reduce the effect of fading. Space-time trellis code is a bandwidth and power efficient method of communication over Rayleigh fading that realizes the benefits of multiple transmit and receive antennas. In this paper we present analytical performance results for space–time trellis codes over spatially correlated Rayleigh fading channels. In this paper we analyze and compare the 8-PSK STTC over Rayleigh fading Channels for determining Performance.
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.
A Novel OFDM Channel Estimation Algorithm with ICI Mitigation over Fast Fading Channels
Directory of Open Access Journals (Sweden)
C. Tao
2010-06-01
Full Text Available Orthogonal frequency-division multiplexing (OFDM is well-known as a high-bit-rate transmission technique, but the Doppler frequency offset due to the high speed movement destroys the orthogonality of the subcarriers resulting in the intercarrier interference (ICI, and degrades the performance of the system at the same time. In this paper a novel OFDM channel estimation algorithm with ICI mitigation based on the ICI self-cancellation scheme is proposed. With this method, a more accurate channel estimation is obtained by comb-type double pilots and then ICI coefficients can be obtained to mitigate the ICI on each subcarrier under the assumption that the channel impulse response (CIR varies in a linear fashion. The theoretical analysis and simulation results show that the bit error rate (BER and spectral efficiency performances are improved significantly under high-speed mobility conditions (350 km/h – 500 km/h in comparison to ZHAO’s ICI self-cancellation scheme.
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.
Directory of Open Access Journals (Sweden)
Md. Zahangir Alam
2011-01-01
Full Text Available The paper proposes a novel technique for reducing noise in M-ary signal transmission through wireless fading channel using wavelet denoising that play the key role. The paper also explains that the conventional threshold-based technique is not capable of denoising M-ary quadrature amplitude modulated (M-QAM signals having multilevel wavelet coefficients through wireless fading channels. A detailed step by step wavelet decomposition and reconstruction processes are discussed here to transform a signal function into wavelet coefficients using simulation software like MATLAB. A 16-QAM modulated symbol through a Rician fading channel is weighted by a control variable of complex form to force the mean of each detail coefficient except low frequency component to zero to enhance noiseless property. The bit error rate (BER performance of the simulation results are furnished to show the effectiveness of the proposed technique. The root mean square of the deviation of the reconstruct signal from the original signal is used to express the effectiveness of the proposed technique. The traditional denoising provides very high value (above 90% of the percentage root mean square difference (PDR and the proposed technique provides only 10% PDR value for the symbol through a noisy channel. The result of the simulation study reveals that the BER performance can be increased using an appropriate control variable to force the mean of each detail coefficient to zero.
Improving 3D-Turbo Code's BER Performance with a BICM System over Rayleigh Fading Channel
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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.
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.
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.
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Yuan Ouyang
2015-01-01
Full Text Available This paper presents the performance analysis of the multiband orthogonal frequency division multiplexing (MB-OFDM ultra-wideband (UWB systems for multipath fading and multiuser interference channels. A closed form approximation of the BER performance of the MB-OFDM UWB system with multiple interferences is proposed. Based on the derived approximation, the effects on the BER performance for the choice of the codeword constraint lengths of the convolutional encoder, the length of the cyclic prefix, and the multiuser environments of two or more interferers are thoroughly discussed. Four UWB multipath fading channels are also investigated for the BER performance of the MB-OFDM UWB system. The simulated results provide us with useful information to appropriately choose the parameters of the MB-OFDM UWB system for the sake of achieving the BER performance that conforms to requirement of the FCC standards.
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.
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Suresh Kumar Jindal
2015-04-01
Full Text Available In this paper, the problem of dual polarization based MIMO Processing in Shadowed-Rician (SR fading land mobile satellite (LMS channels is studied. It is shown in literature that polarization is used as a interference rejection method; and, most of the existing analytical results are not in closed-form. In this paper, we derive the closed-form expressions of the moment generating (MGF function of the received signal-to-noise ratio of the MRC based receiver in SR fading LMS channels. Then we provide closed-form expressions of the symbol error rate (SER by using MGF approach. The analytical diversity order and capacity of the considered scheme is also derived. It is shown by by derived closed-form capacity expression that the capacity of the considered dual polarization based scheme is improved; and it is found very useful in practical satellite communication systems.
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.
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.
Rached, Nadhir Ben
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.
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
For differential phase shift keying (DPSK) and noncoherent frequency shift keying (NFSK) systems over fading channels, the post-detection combining method is a popular means for improving the bit error performance. However, the bit error performance of such systems over Nakagami channels with an arbitrary covariance matrix and real distinct fading parameters has been seldom described in the literature. This paper studies the problem using a generic correlated Nakagami fading model and presents a closed form solution which is used to study the influence of the fading parameters and the signal-to-noise ratio (SNR) distribution ratios among all the branches on the bit error performance. Moreover, the average SNRs of each branch are not restricted to one value in the analysis. The closed form solution developed for the problem can be used to study the influence of the fading parameters and the SNR distribution ratios on the error performance.
Multiband frequency selective surface
Wu, Te-Kao
1998-10-01
This paper addresses the similarity of microwave/millimeter wave frequency selective surfaces (FSS) to optical filters. Specifically, the design approaches of the 4-band FSSs developed for NASA's CASSINI high gain antenna are described in detail. Representative RF test results are given to demonstrate the validity of these designs. These design approaches are very general and can be applied to multiband optical filters.
2008-12-01
ANALYSIS OF A JTIDS/LINK-16-TYPE WAVEFORM TRANSMITTED OVER SLOW, FLAT NAKAGAMI FADING CHANNELS IN THE PRESENCE OF NARROWBAND INTERFERENCE by...Performance Analysis of a JTIDS/Link-16-type Waveform Transmitted over Slow, Flat Nakagami Fading Channels in the Presence of Narrowband Interference 6...performance of a JTIDS/Link-16-type waveform in both additive white Gaussian noise (AWGN) and narrowband interference transmitted over a slow, flat Nakagami
2005-03-01
Wright-Patterson AFB OH, March 2004. AFIT/GE/ENG/04-20. 7. Papoulis, Athanasios and S. Unnikrishna Pillai . Probability, Random Variables, and...Upper Saddle River, New Jersey 07458, 2001. 129 13. Swackhammer, Patrick J. Design and Simulation of a Multiple Access Trans- form Domain Communication
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Yong-Seok Kim
2004-08-01
Full Text Available An improved antenna array (AA has been introduced, in which reverse-link synchronous transmission technique (RLSTT is incorporated to effectively make better an estimation of covariance matrices at a beamformer-RAKE receiver. While RLSTT is effective in the first finger at the RAKE receiver in order to reject multiple-access interference (MAI, the beamformer estimates the desired user's complex weights, enhancing its signal and reducing cochannel interference (CCI from the other directions. In this work, it is attempted to provide a comprehensive analysis of user capacity which reflects several important factors such as the shape of multipath intensity profile (MIP, the number of antennas, and power control error (PCE. Theoretical analysis, confirmed by the simulations, demonstrates that the orthogonality provided by employing RLSTT along with AA may make the DS-CDMA system insensitive to the PCE even with fewer numbers of antennas.
Xu, Ding; Li, Qun
2017-01-01
This paper addresses the power allocation problem for cognitive radio (CR) based on hybrid-automatic-repeat-request (HARQ) with chase combining (CC) in Nakagamimslow fading channels. We assume that, instead of the perfect instantaneous channel state information (CSI), only the statistical CSI is available at the secondary user (SU) transmitter. The aim is to minimize the SU outage probability under the primary user (PU) interference outage constraint. Using the Lagrange multiplier method, an iterative and recursive algorithm is derived to obtain the optimal power allocation for each transmission round. Extensive numerical results are presented to illustrate the performance of the proposed algorithm.
Van Torre, Patrick; Vanveerdeghem, Peter; Rogier, Hendrik
2014-01-01
In off-body communication systems low-cost and compact transceivers are important for realistic applications. An autonomous off-body wireless node was designed and integrated onto a textile antenna. Channel measurements were performed for an indoor non line-off-sight 4x2 MIMO (Multiple-Input Multiple-Output) link using four off-body transmitting nodes and two similar fixed receiving nodes. The channel behavior is characterized as Rayleigh fading with lognormal shadowing and is fitted to a mod...
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Muhammad Imran Akram
2012-01-01
Full Text Available This paper presents the statistical properties of the vehicle-to-vehicle Nakagami-Hoyt (Nakagami-q channel model under non-isotropic condition. The spatial time correlation function (STCF, the power spectral density (PSD, squared time autocorrelation function (SQCF, level crossing rate (LCR, and the average duration of Fade (ADF of the Nakagami-Hoyt channel have been derived under the assumption that both the transmitter and receiver are nonstationary having nonomnidirectional antennas. A simulator that uses the inverse-fast-fourier-transform- (IFFT- based computation method is designed for this model. The simulator and analytical results are compared.
Panajotović, Aleksandra; Sekulović, Nikola; Drača, Dragan; Stefanović, Mihajlo; Stefanović, Časlav
2013-12-01
A dual selection combining (SC) receiver with correlated and unbalanced diversity branches operating in interference-limited Nakagami-m fading environment is considered in this paper. Actually, average fade duration (AFD) of SC system applying desired signal decision algorithm is obtained. Numerical results can be used to examine the effects of fading severity, input signal-to-interference ratio (SIR) unbalance and level of branch correlation on the AFD, as well as the correctness of proposed analytical formulation.
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.
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.
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
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Pragya Gupta
2012-09-01
Full Text Available Demands for capacity in wireless communications, drivenby cellular mobile, Internet and multimedia services havebeen rapidly increasing worldwide. On the other hand, theavailable radio spectrum is limited and the communicationcapacity needs cannot be met without a significantincrease in communication spectral efficiency. Codingtechniques designed for multiple antenna transmission arecalled space-time coding. Space-time coding can achievetransmit diversity and coding gain over spatially uncodedsystems without sacrificing the bandwidth. Space-timetrellis code (STTC has been widely applied to codedmultiple-input multiple-output (MIMO systems because ofits gains in coding and diversity. Diversity techniques areused to reduce the effect of fading. Space-time trellis codeis a bandwidth and power efficient method ofcommunication over Rayleigh fading that realizes thebenefits of multiple transmit and receive antennas. In thispaper we present analytical performance results for space–time trellis codes over spatially correlated Rayleigh fadingchannels. In this paper we analyze and compare the 8-PSKSTTC over Rayleigh fading Channels for determiningPerformance.
Multihop Diversity in Wideband OFDM Systems: The Impact of Spatial Reuse and Frequency Selectivity
Oyman, Ozgur
2008-01-01
The goal of this paper is to establish which practical routing schemes for wireless networks are most suitable for wideband systems in the power-limited regime, which is, for example, a practically relevant mode of operation for the analysis of ultrawideband (UWB) mesh networks. For this purpose, we study the tradeoff between energy efficiency and spectral efficiency (known as the power-bandwidth tradeoff) in a wideband linear multihop network in which transmissions employ orthogonal frequency-division multiplexing (OFDM) modulation and are affected by quasi-static, frequency-selective fading. Considering open-loop (fixed-rate) and closed-loop (rate-adaptive) multihop relaying techniques, we characterize the impact of routing with spatial reuse on the statistical properties of the end-to-end conditional mutual information (conditioned on the specific values of the channel fading parameters and therefore treated as a random variable) and on the energy and spectral efficiency measures of the wideband regime. Ou...
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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
Yao, Hongchao; Wang, Huali
2007-11-01
Modeling of rain fading channel dynamics is essential to the real-time prediction of link availability for Ka-band satellite communication system under rain attenuation impairment, and can validate fade mitigation techniques (FMT) such as adaptive transmission and diversity. The mechanism of dynamic rain attenuation model based on time-series generator is firstly concerned in this paper. We further provide a scheme and implementation of real-time simulator for dynamic rain fading channels based on Hardware-in-the-loop (HIL) simulation method and general Field Programmable Logic Array (FPGA) device. Finally, the impact of adaptive modulation fade countermeasures (AMFC) in the different state of rain attenuation is evaluated with simulation results.
Wang, Xin
2010-01-01
Optimal and suboptimal decentralized estimators in wireless sensor networks (WSNs) over orthogonal multiple-access fading channels are studied in this paper. Considering multiple-bit quantization before digital transmission, we develop maximum likelihood estimators (MLEs) with both known and unknown channel state information (CSI). When training symbols are available, we derive a MLE that is a special case of the MLE with unknown CSI. It implicitly uses the training symbols to estimate the channel coefficients and exploits the estimated CSI in an optimal way. To reduce the computational complexity, we propose suboptimal estimators. These estimators exploit both signal and data level redundant information to improve the estimation performance. The proposed MLEs reduce to traditional fusion based or diversity based estimators when communications or observations are perfect. By introducing a general message function, the proposed estimators can be applied when various analog or digital transmission schemes are u...
Ksairi, Nassar; Bianchi, Pascal; Hachem, Walid
2009-01-01
In this work, a new static relaying protocol is introduced for half duplex single-relay networks, and its performance is studied in the context of communications over slow fading wireless channels. The proposed protocol is based on a Decode or Quantize and Forward (DoQF) approach. In slow fading scenarios, two performance metrics are relevant and complementary, namely the outage probability gain and the Diversity-Multiplexing Tradeoff (DMT). First, we analyze the behavior of the outage probability P_o associated with the proposed protocol as the SNR tends to infinity. In this case, we prove that SNR^2 P_o converges to a constant. We refer to this constant as the outage gain and we derive its closed-form expression for a general class of wireless channels that includes the Rayleigh and the Rice channels as particular cases. We furthermore prove that the DoQF protocol has the best achievable outage gain in the wide class of half-duplex static relaying protocols. A method for minimizing the outage gain with resp...
Wang, Rui; Huang, Kaibin
2009-01-01
In this paper, utilizing the relay buffers, we propose an opportunistic decode-wait-and-forward relay scheme for a point-to-point communication system with a half-duplexing relay network to better exploit the time diversity and relay mobility. For instance, we analyze the asymptotic throughput-delay tradeoffs in a dense relay network for two scenarios: (1) fixed relays with \\textit{microscopic fading} channels (multipath channels), and (2) mobile relays with \\textit{macroscopic fading} channels (path loss). In the first scenario, the proposed scheme can better exploit the \\textit{multi-relay diversity} in the sense that with $K$ fixed relays and a cost of $\\mathcal{O}(K)$ average end-to-end packet delay, it could achieve the same optimal asymptotic average throughput as the existing designs (such as regular decode-and-forward relay schemes) with $K^2$ fixed relays. In the second scenario, the proposed scheme achieves the maximum throughput of $\\Theta(\\log K)$ at a cost of $\\mathcal{O}(K/q)$ average end-to-end...
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Sulyman Ahmed Iyanda
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 M branches out of the L available diversity resources (M ≤ L . 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.
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...
Lee, Jaeyoon; Yoon, Dongweon; Park, Sang Kyu
Recently, we provided closed-form expressions involving two-dimensional (2-D) joint Gaussian Q-function for the symbol error rate (SER) and bit error rate (BER) of an arbitrary 2-D signal with I/Q unbalances over an additive white Gaussian noise (AWGN) channel [1]. In this letter, we extend the expressions to Nakagami-m fading channels. Using Craig representation of the 2-D joint Gaussian Q-function, we derive an exact and general expression for the error probabilities of arbitrary 2-D signaling with I/Q phase and amplitude unbalances over Nakagami-m fading channels.
Channel estimation for physical layer network coding systems
Gao, Feifei; Wang, Gongpu
2014-01-01
This SpringerBrief presents channel estimation strategies for the physical later network coding (PLNC) systems. Along with a review of PLNC architectures, this brief examines new challenges brought by the special structure of bi-directional two-hop transmissions that are different from the traditional point-to-point systems and unidirectional relay systems. The authors discuss the channel estimation strategies over typical fading scenarios, including frequency flat fading, frequency selective fading and time selective fading, as well as future research directions. Chapters explore the performa
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.
Abdallah, Saeed; Psaromiligkos, Ioannis N.
2012-03-01
We analyze the mean-squared error (MSE) performance of widely linear (WL) and conventional subspace-based channel estimation for single-input multiple-output (SIMO) flat-fading channels employing binary phase-shift-keying (BPSK) modulation when the covariance matrix is estimated using a finite number of samples. The conventional estimator suffers from a phase ambiguity that reduces to a sign ambiguity for the WL estimator. We derive closed-form expressions for the MSE of the two estimators under four different ambiguity resolution scenarios. The first scenario is optimal resolution, which minimizes the Euclidean distance between the channel estimate and the actual channel. The second scenario assumes that a randomly chosen coefficient of the actual channel is known and the third assumes that the one with the largest magnitude is known. The fourth scenario is the more realistic case where pilot symbols are used to resolve the ambiguities. Our work demonstrates that there is a strong relationship between the accuracy of ambiguity resolution and the relative performance of WL and conventional subspace-based estimators, and shows that the less information available about the actual channel for ambiguity resolution, or the lower the accuracy of this information, the higher the performance gap in favor of the WL estimator.
Attitude Estimation for In-Service Base Station Antenna Using Downlink Channel Fading Statistics
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Cen Ling
2015-01-01
Full Text Available A maximum-likelihood-estimation method is proposed for extracting the attitude of a sectoring base station (BS antenna by using the received signal strengths observed by multiple user equipments (UEs in this contribution. This method calculates the likelihood function of the antenna attitude derived by taking into account the multiscale fading statistics, that is, path loss, shadowing, and multipath fading. Depending on whether a calibration result of these fading statistics is available or not, the proposed method can be utilized in either calibration-based estimation (CBE or calibration-free estimation (CFE approaches. The performance of both methods is evaluated by Monte-Carlo simulations and real experiments. The results obtained demonstrate that the estimation accuracy of both CBE and CFE approaches increases when the percentage of UEs in the line-of-sight (LoS condition among all available UEs increases and, moreover, the total number of UEs has no significant impact on the estimation accuracy. Furthermore, the CFE exhibits more robust performance than the CBE particularly in the case where the calibration results involve uncertainties.
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.
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L. Polak
2010-12-01
Full Text Available The paper deals with the third (and last part of results of the Czech Science Foundation research project that was aimed into the simulation and measurement of the transmission distortions of the digital terrestrial television according to DVB-T/H standards. In this part the transmission of the digital television according to DVB-T/H standard over the fading channels and their models and profiles for fixed, portable and mobile reception is analyzed. Impact of the fading channels and their models on Modulation Error Rate from I/Q constellations and Bit Error Rates before and after Viterbi decoding in DVB-T/H signal decoding is presented.
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.
El-Bahaie, Ebtehal H.; Al-Hussaini, Emad K.
2010-12-01
In this paper analytical and simulation results for the decentralized detection of unknown signals are introduced. Parallel sensor network scheme is assumed. Additive White Gaussian Noise (AWGN) and Nakagami fading are assumed in both links, that is, from the source to the decentralized local sensors and from the sensors to the fusion center. Furthermore, diversity employing Square Law Combining (SLC) or Square Law Selection (SLS) is considered at each sensor, for both independent and correlated branches. Appreciable improvements are obtained with the increase of the number of sensors and the diversity employment.
Error Analysis of Fixed-Gain AF Relaying with MRC Over Nakagami-m Fading Channels
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S. H. Alvi
2016-04-01
Full Text Available This article investigates the error performance of wireless communication systems that employ binary modulations and Amplify-and-Forward (AF relaying over flat Nakagami-m faded links with maximum ratio combining (MRC at destination. Specifically, we derive a simple yet accurate closed-form approximation for the average bit error probability (ABEP and closed-form expressions for its tight upper and lower bounds. The effect of power imbalance between the relayed links is also studied. Numerical investigations show good agreement between proposed theoretical results and simulations whereas our performance bounds are shown to be tighter than previously proposed bounds for the case of unbalanced relayed links.
Performance Evaluation of a Non-Coherent Digital Delay-Locked Loop in Rayleigh Fading Channels
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Mohamed G. El-Tarhuni
2010-11-01
Full Text Available PN code tracking is one of the most important factors that affect the performance of spread spectrumreceivers. It is desirable to maintain PN code tracking for a long period of time and with high accuracy.This paper presents a non-coherent digital delay-locked loop (DLL for code tracking in direct-sequencespread spectrum (DS-SS systems. The proposed technique utilizes three non-coherent correlators withtime-diversity followed by a lock detector. Analytical results for the mean time to lose lock, also calledmean hold-in time, are derived for both additive white Gaussian noise and Rayleigh fading channelsusing a Markov chain model. Computer simulation results are also presented to validate the analyticalresults. It is shown that the proposed loop can maintain lock for relatively long periods of time underpractical range of signal-to-noise ratio. For instance, the loop maintains lock for more than106 framesfor an energy per bit-to-noise power spectral density (Eb/No of 4 dB or better. It is also shown that themean hold-in time performance is only slightly degraded due to fading because of the time diversity gainutilized by the loop in obtaining the timing information. Finally, the ability of the proposed technique tosuccessfully track randomly and linearly varying delays is demonstrated.
Analytic Nakagami fading parameter estimation in dependent noise channel using copula
Gholizadeh, Mohammad Hossein; Amindavar, Hamidreza; Ritcey, James A.
2013-12-01
In this paper, the probability density function (PDF) estimation is introduced in the framework of estimating the Nakagami fading parameter. This approach provides an analytic procedure for finding the fading parameter. Using the copula theory, an accurate PDF estimate is obtained even when the desired signal is corrupted in a noisy environment. In the real world, the noise samples could be highly dependent on the main signal. Copula-based models are a general set of statistical models defined for any multivariate random variable. Thus, they depict the statistical behavior of a received signal including two dependent terms, representative of the desired signal and noise. Previous works in the Nakagami parameter determination have mainly examined estimation based on either a noiseless sample model or an independent trivial noisy one. In this paper, we consider a more comprehensive situation about the noise destruction and our investigation is done in low signal-to-noise ratios. The parametric bootstrap method approves the accuracy of the analytically estimated PDF, and simulation results show that the new estimator has superior performance over conventional estimators.
Performance Improvement in Spatially Multiplexed MIMO Systems over Weibull-Gamma Fading Channel
Tiwari, Keerti; Saini, Davinder S.; Bhooshan, Sunil V.
2016-11-01
In multiple-input multiple-output (MIMO) systems, spatial demultiplexing at the receiver has its own significance. Thus, several detection techniques have been investigated. There is a tradeoff between computational complexity and optimal performance in most of the detection techniques. One of the detection techniques which gives improved performance and acceptable level of complexity is ordered successive interference cancellation (OSIC) with minimum mean square error (MMSE). However, optimal performance can be achieved by maximum likelihood (ML) detection but at a higher complexity level. Therefore, MMSE-OSIC with candidates (OSIC2) detection is recommended as a solution. In this paper, spatial multiplexed (SM) MIMO systems are considered to evaluate error performance with different detection techniques such as MMSE-OSIC, ML and MMSE-OSIC2 in a composite fading i. e. Weibull-gamma (WG) fading environment. In WG distribution, Weibull and gamma distribution represent multipath and shadowing effects, respectively. Simulation results illustrate that MMSE-OSIC2 detection technique gives the improved symbol error rate (SER) performance which is similar to ML performance and its complexity level approaches to MMSE-OSIC.
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.
CSIR Research Space (South Africa)
Myburgh, HC
2009-05-01
Full Text Available long channels. Its computational complexity is linear in the data block length and approximately independent of the channel memory length, whereas conventional equalization algorithms have computational complexity linear in the data block length...
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.
Institute of Scientific and Technical Information of China (English)
张艳语; 朱义君; 张水莲
2012-01-01
In frequency-selective MIMO channel,a null space based linear transceiver scheme based on precoding was proposed. Each data vector and corresponding decoding matrix are in the joint null space of other delay channel matrices. Frequency -selective MIMO channel is transformed into several spatially orthogonal flat matrix sub-channels.The precoding research over frequency flat channel is directly applicable to the selective channel, thoroughly removing up ISI problem of Z domain method with i-dentical computation. Simulation results show that the proposed algorithm is of better capacity and error performance.%针对选择性MIMO信道多经分离问题,提出了一种基于预编码的收发联合设计方案.该方案中的每路发射矢量及其解码矩阵处于其他时延信道的共同零空间,把选择性信道多径分离为空间正交的若干平坦子信道,从而使平坦信道的预编码研究成果可以直接应用于选择性MIMO信道,解决了传统Z域处理中未消除ISI的问题,复杂度为Z域方法的L(多径数目)倍.仿真结果表明,该算法具有较好容量性能和误码率性能.
Directory of Open Access Journals (Sweden)
Een-Kee Hong
2007-12-01
Full Text Available We analyze the exact average symbol error probability (SEP of binary and M-ary signals with spatial diversity in Nakagami-q (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 FD(n. 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 (q = 1 and single-input single-output (SISO Nakagami-q cases.
Taniguchi, Tetsuki; Sha, Shen; Karasawa, Yoshio
In multiple input multiple output (MIMO) communication systems, eigenvalues of channel correlation matrices play an essential role for the performance analysis, and particularly the investigation about their behavior under time-variant environment ruled by a certain statistics is an important problem. This paper first gives the theoretical expressions for the marginal distributions of all the ordered eigenvalues of MIMO correlation matrices under i. i. d. (independent and identically distributed) Rayleigh fading environment. Then, an approximation method of those marginal distributions is presented: We show that the theory of SIMO space diversity using maximal ratio combining (MRC) is applicable to the approximation of statistical distributions of all eigenvalues in MIMO systems with the same number of diversity branches. The derived approximation has a monomial form suitable for the calculation of various performance measures utilized in MIMO systems. Through computer simulations, the effectiveness of the proposed method is demonstrated.
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.
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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)
Dey Subhrakanti
2007-01-01
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.
Amariucai, George T
2010-01-01
In this paper we study the problem of half-duplex active eavesdropping in fast fading channels. The active eavesdropper is a more powerful adversary than the classical eavesdropper. It can choose between two functional modes: eavesdropping the transmission between the legitimate parties (Ex mode), and jamming it (Jx mode) -- the active eavesdropper cannot function in full duplex mode. We consider a conservative scenario, when the active eavesdropper can choose its strategy based on the legitimate transmitter-receiver pair's strategy -- and thus the transmitter and legitimate receiver have to plan for the worst. We show that conventional physical-layer secrecy approaches perform poorly (if at all), and we introduce a novel encoding scheme, based on very limited and unsecured feedback -- the Block-Markov Wyner (BMW) encoding scheme -- which outperforms any schemes currently available.
A Capacity Improvement Method for CDMA based Mesh Networks in SUI Multipath Fading Channels
Zeeshan, Muhammad; Malik, Muhammad Yasir
2011-01-01
Code Division Multiple Access (CDMA) is the most promising candidate for wideband data access. This is due to the advantage of soft limit on the number of active mobile devices. Many wireless mesh systems impose an upper bound on the BER performance which restricts the increase in number of mobile users. Capacity is further reduced in Multipath Fading Environment (MFE). This paper presents an effective method of improving the capacity of a CDMA based mesh network by managing the transmitted powers of the mobile devices and using MMSE based Multiuser Detection (MUD). The proposed scheme improves the capacity two times as compared to the conventional CDMA based mesh network. Simulation results have been presented to demonstrate the effectiveness of the proposed scheme.
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 M-QAM, M-DPSK and M-PSK with MRC diversity in a Nakagami-m fading channel
Institute of Scientific and Technical Information of China (English)
Alam S.M.Shamsul Alam; Choi GoangSeog
2014-01-01
The nature of a wireless communication channel is very unpredictable. To design a good communication link, it is required to know the statistical model of the channel accurately. The average symbol error probability (ASER) was analyzed for different modulation schemes. A unified analytical framework was presented to obtain closed-form solutions for calculating the ASER of M-ary differential phase-shift keying (M-DPSK), coherent M-ary phase-shift keying (M-PSK), and quadrature amplitude modulation (QAM) over single or multiple Nakagami-m fading channels. Moreover, the ASER was estimated and evaluated by using the maximal ratio-combining (MRC) diversity technique. Simulation results show that an error rate of the fading channel typically depends on Nakagami parameters (m), space diversity (N), and symbol rate (M). A comparison between M-PSK, M-DPSK, and M-QAM modulation schemes was shown, and the results prove that M-ary QAM (M-QAM) demonstrates better performance compared to M-DPSK and M-PSK under all fading and non-fading conditions.
Hadei, Sayed A
2011-01-01
This paper provides analytical performance of the low-complexity family of affine projection algorithms on the estimation of multipath Rayleigh fading channels in the presence of carrier frequency offsets (CFO) and random channel variations. Our analysis is based on the calculation of the error correlation matrix of the estimation, the mean-square weight error (MSWE) and the mean-square estimation error (MSE) parameters. The analysis does not use strong assumptions like small or large step-size, and explicit closed-form expressions for the MSE of estimation are obtained only from common hypotheses in wireless communication context. In this paper, the optimum stepsize parameters minimizing the MSE of estimation are analytically derived without any simplified assumptions. For the sake of comparison with other analytical approaches, we also investigate the performance of the introduced algorithms by the energy conservation relation. Likewise for exact performance analysis, we evaluate all the moment terms that a...
Issaid, Chaouki Ben
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.
Directory of Open Access Journals (Sweden)
T. Gnanasekaran
2008-01-01
Full Text Available Problem statement: In this study we propose a method to improve the performance of Maximum A-Posteriori Probability Algorithm, which is used in turbo decoder. Previously the performance of turbo decoder is improved by means of scaling the channel reliability value. Approach: A modification in MAP algorithm proposed in this study, which achieves further improvement in forward error correction by means of scaling the extrinsic information in both decoders without introducing any complexity. The encoder is modified with a new puncturing matrix, which yields Unequal Error Protection (UEP. This modified MAP algorithm is analyzed with the traditional turbo code system Equal Error Protection (EEP and also with Unequal Error Protection (UEP both in AWGN channel and fading channel. Result: MAP and modified MAP achieve coding gain of 0.6 dB over EEP in AWGN channel. The MAP and modified MAP achieve coding gain of 0.4 dB and 0.9dB over EEP respectively in Rayleigh fading channel. Modified MAP in UEP class 1 and class 2 gained 0.8 dB and 0.6 dB respectively in AWGN channel where as in fading channel class 1 and 2 gained 0.4 dB and 0.6 dB respectively. Conclusion/Recommendations: The modified MAP algorithm improves the Bit Error Rate (BER performance in EEP as well as UEP both in AWGN and fading channels. We propose modified MAP error correction algorithm with UEP for broad band communication.
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Bahrami Hamid Reza
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.
WATER-FILLING SPACE-TIME CODE IN CORRELATED FLAT RAYLEIGH FADING MISO CHANNELS
Institute of Scientific and Technical Information of China (English)
Cheng Jian; Chen Ming; Cheng Shixin
2003-01-01
In this paper, STC with water-filling transmit power distribution in MISO systemis proposed when the partial channel information feedback is possible, for example, at slow fadingscenario. The performances of the water-filling STC including water-filling STTC and water-filling STBC are analyzed. Performance comparison of the Ungerboeck's 2/3 trellis coded 8PSKmodulated 2-STBC and 2-STTCs with QPSK is given out in different channel correlation.
Huang, Huang
2009-01-01
In this paper, we consider the delay-sensitive power and transmission threshold control design in S-ALOHA network with FSMC fading channels. The random access system consists of an access point with K competing users, each has access to the local channel state information (CSI) and queue state information (QSI) as well as the common feedback (ACK/NAK/Collision) from the access point. We seek to derive the delay-optimal control policy (composed of threshold and power control). The optimization problem belongs to the memoryless policy K-agent infinite horizon decentralized Markov decision process (DEC-MDP), and finding the optimal policy is shown to be computationally intractable. To obtain a feasible and low complexity solution, we recast the optimization problem into two subproblems, namely the power control and the threshold control problem. For a given threshold control policy, the power control problem is decomposed into a reduced state MDP for single user so that the overall complexity is O(NJ), where N a...
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.
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Slavche Pejoski
2014-01-01
Full Text Available We present a framework for cross-layer optimized real time multiuser encoding of video using a single layer H.264/AVC and transmission over MIMO wireless channels. In the proposed cross-layer adaptation, the channel of every user is characterized by the probability density function of its channel mutual information and the performance of the H.264/AVC encoder is modeled by a rate distortion model that takes into account the channel errors. These models are used during the resource allocation of the available slots in a TDMA MIMO communication system with capacity achieving channel codes. This framework allows for adaptation to the statistics of the wireless channel and to the available resources in the system and utilization of the multiuser diversity of the transmitted video sequences. We show the effectiveness of the proposed framework for video transmission over Rayleigh MIMO block fading channels, when channel distribution information is available at the transmitter.
Institute of Scientific and Technical Information of China (English)
林家儒; 吴伟陵; 冯志勇
2001-01-01
Analyzes the performance of DS／CDMA systems on multipath Nakagami fading channels and proposes a modified decoding algorithm of turbo code on multipath Nakagami fading channels,i.e.the signal with maximum ratio combiner divides by the all square of amplitudes of the channel,calculate the probability function γ for Turbo code,and then decode the signal as Turbo decoding.%分析了宽带DS／CDMA系统在Nakagami信道中的性能的基础上，针对Nakagami信道对Turbo码译码提出了修正算法——由Rake接收输出经最大比例合并等处理后的信号、除以信道幅度参数αmi的平方之和、以高斯分布计算Turbo码译码的γ函数、进行Turbo码译码.
Directory of Open Access Journals (Sweden)
C. Stefanovic
2013-12-01
Full Text Available A very efficient technique that reduces fading and channel interference influence is selection diversity based on the signal to interference ratio (SIR. In this pa¬per, system performances of selection combiner (SC over correlated Nakagami-m channels with constant correlation model are analyzed. Closed-form expressions are obtained for the output SIR probability density function (PDF and cumulative distribution function (CDF which is main contribution of this paper. Outage probability and the average error probability for coherent, noncoherent modulation are derived. Numerical results presented in this paper point out the effects of fading severity and cor¬relation on the system performances. The main contribu¬tion of this analysis for multibranch signal combiner is that it has been done for general case of correlated co-channel interference (CCI.
National Research Council Canada - National Science Library
Moinuddin, M; Sheikh, A U. H; Zerguine, A; Deriche, M
.... This analysis presents a unified approach as Nakagami- fading is a general fading distribution that includes the Rayleigh, the one-sided Gaussian, the Nakagami- , and the Rice distributions as special cases...
Zhong, Caijun
2010-09-01
This paper studies the ergodic capacity of multiple-input multiple-output (MIMO) systems with a single co-channel interferer in the low signal-to-noise-ratio (SNR) regime. Two MIMO models namely Rician and Rayleigh-product channels are investigated. Exact analytical expressions for the minimum energy per information bit, {Eb/N0min, and wideband slope, S0, are derived for both channels. Our results show that the minimum energy per information bit is the same for both channels while their wideband slopes differ significantly. Further, the impact of the numbers of transmit and receive antennas, the Rician K factor, the channel mean matrix and the interference-to-noise-ratio (INR) on the capacity, is addressed. Results indicate that interference degrades the capacity by increasing the required minimum energy per information bit and reducing the wideband slope. Simulation results validate our analytical results. © 2010 IEEE.
EVALUATION OF BER FOR VARIOUS FADING CHANNEL IN DWT BASED MIMO-OFDM SYSTEM
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D. Meenakshi
2013-04-01
Full Text Available MIMO communication is mainly use in the OFDM to improve the communication performance and capacity. DWT based MIMO-OFDM is used in this paper. Compare to the FFT based MIMO-OFDM it has lot advantages. There is no need for cyclic prefix, flexibility and optimal resolution. Ripple(Wavelet concept has developed as a fresh scientific implement with the aim of preserve be functional in several applications such as processing of image, biomedical manufacturing, radar, physics, organize systems also message systems. The essential region of purpose of ripples in communication system: numerous accesses. A fresh modulation/multiplexing scheme consuming ripple transform remained planned for (3rd production organization project 3GPP systems. This fresh modulation system implemented in (orthogonal frequency division multiplexing OFDM scheme in addition to conventional based(FFT transform blocks is replaced by wavelet transform blocks. There are many multiplicity of ripple transforms are offered, out of which four were chosen. They are Haar, Daubechies, Bi-orthogonal and reverse Bi-orthogonal transforms. Haar wavelet is best one of among all types of wavelet. The performance of DWT based MIMO-OFDM is calculated by bit error rate (BER in various channel that is AWGN channel and Rayleigh channel. Using MATLAB-Simulation which channel is best for the DWT based MIMO-OFDM.
Park, Kihong
2012-09-01
In this paper, we investigate secrecy communications in two-hop wireless relaying networks which consist of one source, one amplify-and-forward (AF) relay, one legitimate destination, and one eavesdropper. To prevent the eavesdropper from intercepting the source message, we make the destination send the intended noise to the AF relay during the first phase. This is referred to as cooperative jamming. According to the channel information at the destination, we address two types of jamming power allocation; (i) rate-optimal power allocation and (ii) outage-optimal power allocation. More specifically, without the instantaneous channel knowledge for the eavesdropper side, the outage probability of the secrecy rate is minimized with respect to the intended noise power level. We show that the outage-optimal allocation gives almost the same outage probability as the rateoptimal one. In addition, the jamming power consumption can be significantly reduced compared to the fixed and rate-optimal power allocation methods. © 2012 IEEE.
On Multiple Users Scheduling Using Superposition Coding over Rayleigh Fading Channels
Zafar, Ammar
2013-02-20
In this letter, numerical results are provided to analyze the gains of multiple users scheduling via superposition coding with successive interference cancellation in comparison with the conventional single user scheduling in Rayleigh blockfading broadcast channels. The information-theoretic optimal power, rate and decoding order allocation for the superposition coding scheme are considered and the corresponding histogram for the optimal number of scheduled users is evaluated. Results show that at optimality there is a high probability that only two or three users are scheduled per channel transmission block. Numerical results for the gains of multiple users scheduling in terms of the long term throughput under hard and proportional fairness as well as for fixed merit weights for the users are also provided. These results show that the performance gain of multiple users scheduling over single user scheduling increases when the total number of users in the network increases, and it can exceed 10% for high number of users
On the Error Rate Analysis of Dual-Hop Amplify-and-Forward Relaying in Generalized-K Fading Channels
Directory of Open Access Journals (Sweden)
George P. Efthymoglou
2010-01-01
Full Text Available We present novel and easy-to-evaluate expressions for the error rate performance of cooperative dual-hop relaying with maximal ratio combining operating over independent generalized- fading channels. For this system, it is hard to obtain a closed-form expression for the moment generating function (MGF of the end-to-end signal-to-noise ratio (SNR at the destination, even for the case of a single dual-hop relay link. Therefore, we employ two different upper bound approximations for the output SNR, of which one is based on the minimum SNR of the two hops for each dual-hop relay link and the other is based on the geometric mean of the SNRs of the two hops. Lower bounds for the symbol and bit error rates for a variety of digital modulations can then be evaluated using the MGF-based approach. The final expressions are useful in the performance evaluation of amplify-and-forward relaying in a generalized composite radio environment.
Le, Minh Hung; Liyana-Pathirana, Ranjith
2003-06-01
The unequal error protection (UEP) codes with wavelet-based algorithm for video compression over wide-band code division multiple access (W-CDMA), additive white Gaussian noise (AWGN) and Rayleigh fading channels are analysed. The utilization of Wavelets has come out to be a powerful method for compress video sequence. The wavelet transform compression technique has shown to be more appropriate to high quality video applications, producing better quality output for the compressed frames of video. A spatially scalable video coding framework of MPEG2 in which motion correspondences between successive video frames are exploited in the wavelet transform domain. The basic motivation for our coder is that motion fields are typically smooth that can be efficiently captured through a multiresolutional framework. Wavelet decomposition is applied to video frames and the coefficients at each level are predicted from the coarser level through backward motion compensation. The proposed algorithms of the embedded zero-tree wavelet (EZW) coder and the 2-D wavelet packet transform (2-D WPT) are investigated.
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.
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.
Yu, Xiangbin; Dong, Tao; Xu, Dazhuan; Bi, Guangguo
2010-09-01
By introducing an orthogonal space-time coding scheme, multiuser code division multiple access (CDMA) systems with different space time codes are given, and corresponding system performance is investigated over a Nakagami-m fading channel. A low-complexity multiuser receiver scheme is developed for space-time block coded CDMA (STBC-CDMA) systems. The scheme can make full use of the complex orthogonality of space-time block coding to simplify the high decoding complexity of the existing scheme. Compared to the existing scheme with exponential decoding complexity, it has linear decoding complexity. Based on the performance analysis and mathematical calculation, the average bit error rate (BER) of the system is derived in detail for integer m and non-integer m, respectively. As a result, a tight closed-form BER expression is obtained for STBC-CDMA with an orthogonal spreading code, and an approximate closed-form BER expression is attained for STBC-CDMA with a quasi-orthogonal spreading code. Simulation results show that the proposed scheme can achieve almost the same performance as the existing scheme with low complexity. Moreover, the simulation results for average BER are consistent with the theoretical analysis.
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.
Saturation Throughput - Delay Analysis of IEEE 802.11 DCF in Fading Channel
Hadzi-Velkov, Zoran
2010-01-01
In this paper, we analytically analyzed the impact of an error-prone channel over all performance measures in a trafficsaturated IEEE 802.11 WLAN. We calculated station's transmission probability by using the modified Markov chain model of the backoff window size that considers the frame-error rates and maximal allowable number of retransmission attempts. The frame error rate has a significant impact over theoretical throughput, mean frame delay, and discard probability. The peak throughput of a WLAN is insensitive of the maximal number of retransmissions. Discard probabilities are insensitive to the station access method, Basic or RTS/CTS.
基于Nakagami衰落的分集合并系统性能分析%Performance Analysis of Diversity System over Nakagami Fading Channels
Institute of Scientific and Technical Information of China (English)
朱秋明; 吕卫华; 黄嘉乐; 徐大专; 陈小敏; 唐亚平
2013-01-01
分集技术可有效提高无线通信系统抗衰落性能,通过将Nakagami衰落下的分集系统等效为单输入单输出系统,推导获得了选择合并(Selection combining,SC)、等增益合并(Equal gain combining,EGC)和最大比合并(Maximal ratio combining,MRC)3种方式下系统的输出信噪比和中断概率等性能表达式,并提出一种基于改进的Nakagami分集信道舍弃法模型用于数值仿真与验证.仿真结果表明,理论表达式结果与仿真值非常吻合,可用于辅助瑞利、莱斯和Nakagami等多种信道衰落下分集系统的参数选择、算法设计和性能评估.%Diversity combining is an effective technique to combat signal fading and improve the performance of wireless communication system significantly.The diversity system over Nakagami fading channels is equivalent as a single input and single output (SISO) system.Then,the expressions of system parameter such as signal-to-noise ratio (SNR) distribution and outage probability are derived for selection combining (SC),equal gain combining (EGC) and maximal ratio combining (MRC) schemes under Nakagami fading channels.A modified Nakagami fading model based on rejection method is also presented to numerical simulation and validation.Numerical simulation results show that the theoretical results match the simulation results very well,which is helpful for parameter selection,algorithm design and performance evaluation of diversity system over various fading such as Rayleigh,Rice and Nakagami.
Institute of Scientific and Technical Information of China (English)
张艳语; 朱义君; 张水莲
2013-01-01
基于投影空间,提出了频率选择性MIMO (FS-MIMO)信道下一种实现块传输的收发联合设计方案.通过收发联合分离多径,把选择性信道转化为了若干正交的平坦MIMO等效信道,增加了系统设计的自由度.给出了一种容量最优的功率分配方案,推导了其误码率和信道容量的解析式.仿真结果验证了理论分析的正确性,该方案在高信噪比时与非块传输相比容量增益为L(多径数目).%Based on orthogonal projection,a transceiver scheme is proposed for MIMO block transmission over frequency-selective channel.By separating multi-path components,the selective MIMO channel is decomposed into L (the number of multi-path components) flat orthogonal MIMO effective channels,increasing degrees of freedom of system design.The analytical expressions of BER and capacity are given,based on proposed capacity-optimal power allocation.Simulation results show that compared with the existing non-block transmission,the capacity gain is L in high SNR regime.
MQAM和MPSK在Nakagami衰落信道中的BER性能%BER performance of MQAM and MPSK in Nakagami fading channel
Institute of Scientific and Technical Information of China (English)
谢俊松; 范平志; DARNELL Mike
2004-01-01
Based on the BER performance of MQAM and MPSK in AWGN channel with sufficient accuracy, BER performance of MQAM and MPSK in Nakagami-m fading channel with or without MRC diversity is derived and evaluated. Analytical and numerical results show that previous results obtained for AWGN, Rayleigh fading or even Rician fading channels with or without MRC diversity can be considered as special cases of the results presented in this paper.%基于AWGN信道中MQAM和MPSK的BER性能的近似准确分析结果,本文导出并分析了MQAM和MPSK在Nakagami-m衰落信道中采用或不采用MRC分集时的BER性能.分析结果表明,在AWGN信道、瑞利衰落信道甚至莱斯衰落信道下,现有采用或不采用MRC分集的系统性能分析结果均可以作为本文分析结果的特例.
Blind cooperative diversity using distributed space-time coding in block fading channels
Tourki, Kamel
2010-08-01
Mobile users with single antennas can still take advantage of spatial diversity through cooperative space-time encoded transmission. In this paper, we consider a scheme in which a relay chooses to cooperate only if its source-relay channel is of an acceptable quality and we evaluate the usefulness of relaying when the source acts blindly and ignores the decision of the relays whether they may cooperate or not. In our study, we consider the regenerative relays in which the decisions to cooperate are based on a signal-to-noise ratio (SNR) threshold and consider the impact of the possible erroneously detected and transmitted data at the relays. We derive the end-to-end bit-error rate (BER) expression and its approximation for binary phase-shift keying modulation and look at two power allocation strategies between the source and the relays in order to minimize the end-to-end BER at the destination for high SNR. Some selected performance results show that computer simulations based results coincide well with our analytical results. © 2010 IEEE.
相关Nakagami衰落分集信道仿真与分析%Simulation and Analysis of Diversity Channels under Correlated Nakagami Fading
Institute of Scientific and Technical Information of China (English)
朱秋明; 徐大专; 王成华; 陈小敏; 孙翔
2012-01-01
针对传统Nakagami衰落仿真方法难以提供精确互相关性的问题,提出一种适用于不同支路功率和衰落系数的相关Nakagami衰落信道仿真模型.证明了Nakagami和Gamma随机变量相关系数的内在联系,利用相关Gamma变量的均方根获得相关Nakagami衰落,推导了该模型输出幅值分布的误差表达式.仿真结果表明:该模型实现简单,仿真输出衰落幅值、相位分布与理论值吻合,互相关性能优于传统模型；其中第1支路通常由单个Gamma变量直接产生,仿真输出衰落的分布误差为0.%Aiming at the problem of the traditional Nakagami fading simulation method that can not provide accurate cross-correlation, a simulation model for correlated Nakagami fading channels suitable for unequal branch powers and fading parameters is proposed. The relationships between the correlation coefficients of Gamma and Nakagami random variables are proved. The correlated Nakagami fadings are generated by using the square roots of correlated Gamma variables. The error expression of the model's output envelope distribution is derived. Simulation results show that: the model is easier to achieve, the simulation fading envelope and phase distributions are close to the theoretical results,and the cross-correlation is more accurate than other models;the distribution error of the first simulation branch is zero, because it is always generated by one Gamma variable.
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.
复合衰落信道建模及模拟方法研究%Modeling and Simulation for Composite Fading Channel
Institute of Scientific and Technical Information of China (English)
朱秋明; 戴秀超; 刘星麟; 陈小敏; 周生奎
2015-01-01
针对传统信道模拟器仅考虑多径衰落的问题，建立了包含路径损耗、阴影衰落和多径衰落的复合衰落信道模型，提出了一种基于高斯变量分解和谐波叠加原理的硬件模拟方法，推导了该方法输出衰落幅值理论分布与仿真参数的内在联系，并详细分析了可编程逻辑器件定点化模型输出周期性及位宽选择等问题。针对原型化模拟器的实测结果表明，该模拟方法输出信道衰落的统计特性与理论值吻合，可用于实验室中无线通信系统的性能测试和验证。%The traditional channel emulator usually only consider the effects of small scale fading caused by multipath propagation.A composite fading channel model including path loss,shadowing (known as large scale fading)and mul-tipath fading is established,and a novel hardware generation method based on Gaussian decomposition and sum-of-sinusoids (SOS)theory is presented in this paper,which is suitable for hardware to realize.On this basis,the theoretical probability density function (PDF)of output fading envelope,as well as the relationship between output PDF and simulation parame-ters is derived.The periodicity of output fading sequences and data width selection for the fixed point model based on field programmable gate array (FPGA)are also analyzed.The experimental results for prototype emulator show that the output fading’s statistical properties agree well with the theoretical ones.So it can be used for performance evaluation and algo-rithm verification of wireless communication system in the lab.
MIMO-OC Scheme to Suppress Co-channel Interference
Zhang, Wei Jiong; Zhou, Xi Lang; Jin, Rong Hong
In this letter, we present a multiple-input multiple-output (MIMO) optimal combining (OC) scheme based on alternate iteration. With the channel state information (CSI) of co-channel interferers (CCIs), this algorithm can be used in flat fading and frequency selective channels to suppress CCIs. Compared with the optimal transceiver of MIMO maximal ratio combining (MRC) systems, results of simulation show that this scheme improves the uplink transmission performance significantly.
Symbols detection for frequency-selective V-BLAST OFDM systems
Institute of Scientific and Technical Information of China (English)
Wu Xiaojun; Li Xing; Wang Jilong
2005-01-01
As the combining form of the orthogonal frequency-division multiplexing (OFDM) technique and the vertical Bell Labs layered space-time (V-BLAST) architecture, the V-BLAST OFDM system can better meet the demand of next-generation (NextG) broadband mobile wireless multimedia communications. The symbols detection problem of the V-BLAST OFDM system is investigated under the frequency-selective fading environment. The joint space-frequency demultiplexing operation is proposed in the V-BLAST OFDM system. Successively, one novel half-rate rotational invariance joint space-frequency coding scheme for the V-BLAST OFDM system is proposed. By elegantly exploiting the above rotational invariance property, we derive one direct symbols detection scheme without knowing channels state information (CSI) for the frequency-selective V-BLAST OFDM system. Extensive simulation results demonstrate the validity of the novel half-rate rotational invariance joint space-frequency coding scheme and the performance of the direct symbols detection scheme.
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.
Ansari, Imran Shafique; Alouini, Mohamed-Slim; Kucur, Oğuz
2012-01-01
The probability density function (PDF) and cumulative distribution function of the sum of L independent but not necessarily identically distributed gamma variates, applicable to the output statistics of maximal ratio combining (MRC) receiver operating over Nakagami-m fading channels or in other words to the statistical analysis of the scenario where the sum of squared Nakagami-m distributions are user-of-interest, is presented in closed-form in terms of well-known Meijer's G function and easily computable Fox's \\={H} function for integer valued and non-integer valued diversity orders (i.e., m fading parameter of Nakagami fading environment), respectively. Further analysis, particularly on bit error rate via PDF-based approach, too is represented in closed form in terms of Meijer's G function and Fox's \\={H} function for integer valued diversity orders, and extended Fox's \\={H} function ($\\hat{H}$) for non-integer valued diversity orders. The proposed results complement previous elegant results that are either...
Fan, Xiaozheng; Wang, Yan; Hu, Manfeng
2016-01-01
In this paper, the fuzzy [Formula: see text] output-feedback control problem is investigated for a class of discrete-time T-S fuzzy systems with channel fadings, sector nonlinearities, randomly occurring interval delays (ROIDs) and randomly occurring nonlinearities (RONs). A series of variables of the randomly occurring phenomena obeying the Bernoulli distribution is used to govern ROIDs and RONs. Meanwhile, the measurement outputs are subject to the sector nonlinearities (i.e. the sensor saturations) and we assume the system output is [Formula: see text], [Formula: see text]. The Lth-order Rice model is utilized to describe the phenomenon of channel fadings by setting different values of the channel coefficients. The aim of this work is to deal with the problem of designing a full-order dynamic fuzzy [Formula: see text] output-feedback controller such that the fuzzy closed-loop system is exponentially mean-square stable and the [Formula: see text] performance constraint is satisfied, by means of a combination of Lyapunov stability theory and stochastic analysis along with LMI methods. The proposed fuzzy controller parameters are derived by solving a convex optimization problem via the semidefinite programming technique. Finally, a numerical simulation is given to illustrate the feasibility and effectiveness of the proposed design technique.
Performance analysis of CS-DCSK over Nakagami-m fading channels%CS-DCSK在Nakagami-m衰落信道下的性能分析
Institute of Scientific and Technical Information of China (English)
陈志贵; 徐位凯
2012-01-01
The code-shifted differential chaos shift keying(CS-DCSK) is an improved scheme of DCSK, which eliminates the delay circuits in receiver. It simplifies the implementation of system. For the study of the performance of CS-DCSK over the generalization multipath fading channels, based on Gaussian approximation (GA) the BER performance is analyzed o-ver Nakagami-m fading channel. The expression of bit error rate( BER) is presented. Simulation results and numerical results show that the analyzed results are well consistent with the simulation results. And the BERs of different channel parameter in are compared and the reasons are analyzed.%码复用差分混沌移位键控(code-shifted differential chaos shift keying,CS-DCSK)是一种DCSK的改进方案,其消除了接收机的延时电路,简化了系统实现.为了研究在一般化的多径衰落信道下的性能,基于高斯近似(Gaussian approximation,GA)方法分析了CS-DCSK在Nakagami-m衰落信道下的误比特率(bit error rate,BER)性能,给出了BER的数值积分解.计算机仿真验证了分析结果,比较了不同信道参数m条件下的误比特率性能,并分析了原因.
Institute of Scientific and Technical Information of China (English)
燕兵; 史治平; 于清苹; 张忠培
2009-01-01
A model of MIMO system over spatial correlative and frequency selective channel is constructed. The non - binary RA codes are adapted as channel codes at the transmitter,and a correlative and uncorre-latod channel adaptive iterative detection method using soft interference cancellation is adapted at the re-ceiver. In this method, the sliding window based on MMSE method is used to cancel inter - symbol interfer-ence(ISI), then joint antenn as maximum likelihood detection is performed, finally soft information is pas-sod from detector to decoder,thus one iteration process(called JAD SC/MMSE) is completed. This model brings very low bit error rate (BER), and its advanced scheme, where diversity in modulation field is added at the transmitter,can achieve better performance. For contrast, BER of the common scheme, based on an-tenna by antenna detection which uses MMSE only (ABA SC/MMSE) is very poor. The simulation result also proves the opinion above.%给出了一种频率选择性信道下空间相关MIMO的系统模型,其发送端采用准循环系统RA码,接收端采用一种对空间相关和非相关信道均适用的软干扰消除迭代检测算法.该算法首先采用基于最小均方误差检测(MMSE)的滑动窗口模型进行干扰消除,然后采用多天线联合最大似然检测(ML)以得到软信息,再将得到的软信息传递到译码器译码并输出发送比特的软信息作为下一次迭代的先验信息,即完成一次迭代.此模型能够取得比较好的误码率性能(BER),其改进方案既增加了发送端的调制域分集,性能又有提升.作为比较,基于软干扰消除的逐天线MMSE迭代检测的方案(ABA SC/MMSE)性能很差.仿真结果也证明了以上观点.
Research of Nakagami fading channel model in mine mobile communica-tion%矿井移动通信中Nakagami衰落信道模型的研究
Institute of Scientific and Technical Information of China (English)
张长森; 张艳芳
2014-01-01
According to the current development status of mine mobile communication, aiming at the variability of statistical characteristics of fast fading multipath signal amplitude in a mine wireless channel, this paper puts forward a Nakagami amplitude statistics fading channel simulation model based on the Matlab. And using this model, the transceiver at the same transmission distance in the straight empty roadway, simulated fading effect of Nakagami for 900 MHz, 1 800 MHz and 2.45 GHz bands of the electromagnetic wave, simulation model is verified by using QPSK signal which is inputted. The results demonstrate that the model has the advantages of simple process, strong operability and more precise description of mine mobile communication channel fading process, the model is of great reference value to improvement in the overall performance of the mine mobile communication.%根据目前矿井移动通信的发展状况，针对矿井无线信道快衰落多径信号幅度统计特性的可变性，提出了一种基于Matlab的Nakagami幅度统计衰落信道仿真模型。利用该模型，对空直巷道中收发信机在相同传输距离下，针对900 MHz、1800 MHz和2.45 GHz频段的电磁波对Nakagami衰落的影响进行了仿真，并将QPSK信号作为输入信号进一步的验证。结果表明，该模型具有创建过程简单，可操作性强，对矿井移动通信信道衰落过程描述较为精确等优点，这对矿井移动通信整体性能的提高具有较大的参考价值。
Djordjević, Nebojša; Jaksić, Branimir S.; Matović, Ana; Matović, Marija; Smilić, Marko
2015-11-01
A system with macrodiversity selection combining (SC) receiver and for microdiversity equal gain combining (EGC) receivers is considered. Received signal is subjected, simultaneously to multipath fading and shadowing, resulting in signal envelope and signal power variation. Closed form expressions for moments of macrodiversity SC receiver output signal envelope are calculated. Numerical expressions are plotted to present the influences of Gamma shadowing severity and Nakagami-m severity on moments of proposed system output signal.
Luk, Eric K.; Fagan, Anthony D.
1994-03-01
The performance of microwave digital radio systems is severely degraded by multipath fading and also by the nonlinear power amplifier at the transmitter, the combined effects of these result in a time varying nonlinear channel. In this paper, the multilayer perceptron (MLP) based equalizer is investigated for use on such channels. It is found to outperform the conventional approach, that is, the use of a transversal equalizer at the receiver operating with a signal predistorter placed before the non-linear power amplifier at the transmitter. An L- level non-linear function is used as a node activation for the MLP. Two update schemes are investigated, one being a complex version of the back propagation algorithm, the other a complex version of the delta-bar-delta algorithm.
Statistical analysis on the optical fading in free space optical channel for RoFSO link design
Kim, Kyung-Hwan; Higashino, Takeshi; Tsukamoto, Katsutoshi; Komaki, Shozo; Kazaura, Kamugisha; Matsumoto, Mitsuji
2010-01-01
This paper presents empirical probability density functions (p.d.fs) of variance and fluctuation speed of scintillation, through analyzing a number of experimental data measured in Japan by a statistical model. The model enables us to treat scintillation speed by one parameter of cut-off frequency in the power spectral density (PDS). By using the model and based on the two p.d.fs, we also present simulation results on the level crossing rate (LCR) and average fade duration (AFD). Combined the two results, an outage probabilities corresponding to a threshold optical intensity can be derived.
Models of Stochastic Differential Equations for Correlated Fading Channels%相关衰落信道的随机微分方程模型
Institute of Scientific and Technical Information of China (English)
扈罗全; 施亚申; 陆全荣; 朱洪波
2009-01-01
研究使用随机微分方程产生相关衰落信道中接收机的抽头统计量.使用Iangevin方程对发生Doppler频移的随机相位进行建模,在对多径分量的幅度增益进行合理建模以后,从理论上证明表征抽头带通信号的统计特性仍然服从Rayleigh分布.使用仿真方法研究了相关衰落信道统计量的一些统计特性,发现随机相位是具有一定相关关系的高斯变量,所得抽头为独立的Rayleigh变量.%Stochastic differential equations (SDE) are applied to generate correlated random variables as receiver taper of fading channels. It is assumed that the random phases can be modeled through a Langevin equation and the amplitude gains follow a reasonable distribution, which are characterized by SDE. We further prove that the band-passed signals of tap in multipath channel still follow Rayleigh distribution. Simulation results of statistical character-istics of correlated fading channel, such as correlation function and Doppler power spectrum, agree well with the theo-retic values. The random phase is correlated Ganssian variables and the taper is the independent Rayleigh variables, which demonstrate the applicability of the proposed methodology.
Turbo-TCM在AWGN和Rayleigh衰落信道下的性能研究%Turbo-TCM Performance under AWGN and Rayleigh Fading Channels
Institute of Scientific and Technical Information of China (English)
任俊涛; 王睦重; 邵定蓉
2003-01-01
A simple algorithm for Turbo-TCM decoding was given in this paper.With this algorithm, Turbo-TCM can easily be used to real systems with various code rates and modulations of QPSK, 8PSK, 16QAM or 64QAM.The bit error ratio performance was studied under AWGN and fading channels.The simulation results were also given in this paper.%给出了一种简单的Turbo-TCM解调译码方法,使用这种方法可较容易地把Turbo码用于各种编码速率和QPSK,8PSK,16QAM或64QAM等各种调制方式下的TCM系统中.研究了各种编码速率和调制方式的Turbo-TCM在AWGN和Rayleigh 衰落信道下的性能,并给出了仿真试验结果.
Institute of Scientific and Technical Information of China (English)
童新海; 甘仲民; 杨喜根
2001-01-01
研究了采用Turbo码技术的抗衰落性能,首先分析了Turbo码在卫星移动遮蔽Rician衰落信道下的误差纠错性能限,然后通过计算机仿真模拟了三种不同的卫星移动衰落信道下Turbo码的性能,研究了不同衰落信道特性对Turbo码性能的影响情况,同时还讨论了在衰落信道下Turbo码的子码约束长度和交织器长度两个主要参数对性能的影响情况。%In this paper, theoretical analysis of error rate performance about Turbocode on Mobile satellite shadowed Rician fading channel is presented. And comparison with the performance on AWGN is discussed. The simulation results by computer on three different mobile satellite fading channel is also presented. The influence on Turbocode performance of different fading channel characteristic is highlighted. In the meantime, the roles of two Turbocode main parametersconstitute code constraint length and the interleaver lengthon Mobile satellite shadowed fading channel is discussed.
Ben Issaid, Chaouki
2016-06-01
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 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, a well-desired property characterizing the robustness of importance sampling schemes, for both identically and non-identically independent distributed cases. We show the accuracy and the efficiency of our approach compared to naive Monte Carlo via some selected numerical simulations.
Issaid, Chaouki ben
2017-01-26
The Gamma-Gamma distribution has recently emerged in a number of applications ranging from modeling scattering and reverberation 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 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 Gamma-Gamma variates. More specifically, we propose robust importance sampling schemes that efficiently evaluates the outage probability of diversity receivers over Gamma-Gamma fading channels. The proposed estimators satisfy the well-known bounded relative error criterion for both maximum ratio combining and equal gain combining cases. We show the accuracy and the efficiency of our approach compared to naive Monte Carlo via some selected numerical simulations.
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.
衰落信道下能量检测的性能分析%Performance analysis of energy detection in fading channels
Institute of Scientific and Technical Information of China (English)
邹丽; 张士兵; 吉晓东
2011-01-01
在认知无线电系统中,大部分的无线信道可以表征为NAKAGAMI衰落信道或莱斯衰落信道.针对NAKAGAMI衰落信道和莱斯衰落信道环境下的能量检测,分析了频谱检测虚警概率和漏检概率与信道模型参数之间的关系,比较了单用户检测和多用户合作检测性能,得到了虚警概率和漏检概率数学表达式,为能量检测器的设计提供了性能参考界.数值仿真结果表明,NAKAGAMI信道下,能量检测性能随衰落因子和平均信噪比的增大而改善;莱斯衰落信道下,能量检测性能随平均信噪比的增大而提高;多用户合作检测性能分别比单用户提高1一2个数量级.%In cognitive radio, most channels can be characterized by Nakagami channel model or Rician channel model. Starting from the energy detection in Nakagami channel and Rician channel, this paper analyzed the relationships of the false alarm and miss detection probabilities with the channel parameters, compared the pedormances of single user detection with cooperative detection, derived the expressions of false alarm probability and miss detection probability. It provided an upper bound for designing energy detector. Numerical results showed that the detection performance becomes better with the increasing of channel fading factor or average signal-to-noise ratio(SNR) in Nakagami channel, and the detection performance becomes rather better as the increasing of average SNR in Rician channel. Compared with single user detector, the cooperative detector improved the performance 1 ～ 2 exponential quantity in false alarm probability and miss detection probability.
Fade-Free Mobile Communication
Stevenson, C. R.
1986-01-01
Scheme for mobile communication reduces multipath fading and interference between adjacent channels. Proposed communication system lends itself to almost completely digital implementation, eliminating costly and bulky crystal filters. Scheme suitable for satellite-aided or terrestrial mobile communication, including cellular mobile telephony, at frequencies in 150-to-900-MHz range.
Institute of Scientific and Technical Information of China (English)
王哲; 张晓林; 陈雷
2009-01-01
For multipath fading channel, an image transmission method which combines wavelet transform and orthogonal frequency division multiplexing ( OFDM ) adaptive modulation was proposed, and the algorithm for joint source channel optimal allocation of channel bandwidth and power was presented as well. Following the presentation of system structure, the problems such as the implementation and distortion estimation of image transmission based on wavelet transform over noisy channel, and optimal bit-power allocation for multi bit error rate ( BER) OFDM adaptive modulation were modeled and analyzed, modeling and analysis facilitate the combination of source quantization coding and OFDM adaptive modulation, and a joint source channel optimal bandwidth and power allocating algorithm was also developed. Simulations and analysis show that the image transmission using joint source-channel coding modulation over multipath fading channel can be achieved with small coding complexity and delay, and performance can be improved due to joint source-channel optimal allocation of bandwidth and power.%针对多径衰落信道提出了一种基于小波变换并结合OFDM(Orthogonal Fre-queney Division Multiplexing)自适应调制的图像传输方法和信源信道联合带宽功率优化分配算法.给出了编码传输方法结构,对有噪信道下基于小波变换的图像编码传输实现和失真估计问题及多误码率OFDM自适应调制比特功率优化分配问题进行了建模和分析,使得信源量化编码与OFDM调制能够方便地结合起来,并进一步得到了相应的信源信道联合优化带宽功率分配方法.仿真和分析表明,该方法实现了多径信道下图像的信源信道联合编码调制传输,编解码复杂度和延迟小,且信源信道联合优化的带宽功率分配可有效提高信道资源利用效率.
Yilmaz, Ferkan
2011-01-01
Relay technology has recently gained great interest in millimeter wave (60 GHz or above) radio frequencies as a promising transmission technique improving the quality of service, providing high data rate, and extending the coverage area without additional transmit power in deeply shadowed wireless environments. The performance of relay-based systems depends considerably on which relay selection protocols are used. These protocols are typically using the channel side information (CSI). Specifically, the relay terminal (RT) is chosen among all available RTs by a centralized entity (CE) which receives all RTs' CSI via feedback channels. However, in the millimeter wave radio frequencies, the rate of the variation of the CSI is much higher than that of a classical system operating in 6 GHz frequencies under the same mobility conditions, which evidently results in a serious problem causing outdated (inaccurate) CSI for the relay selection protocol at the CE since the feedback channels have a backhaul / transmission...
DEFF Research Database (Denmark)
Cavalcante, Lucas Costa Pereira; Silveira, Luiz F. Q.; Rommel, Simon
2016-01-01
Millimeter wave communications based on photonic technologies have gained increased attention to provide optic fiber-like capacity in wireless environments. However, the new hybrid fiber-wireless channel represents new challenges in terms of signal transmission performance analysis. Traditionally......, such systems use diversity schemes in combination with digital signal processing (DSP) techniques to overcome effects such as fading and inter-symbol interference (ISI). Wavelet Channel Coding (WCC) has emerged as a technique to minimize the fading effects of wireless channels, which is a mayor challenge...... in systems operating in the millimeter wave regime. This work takes the WCC one step beyond by performance evaluation in terms of bit error probability, over time-varying, frequency-selective multipath Rayleigh fading channels. The adopted propagation model follows the COST207 norm, the main international...
Coney, Thom A.
1996-01-01
Performance status of the Adaptive Rain Fade Compensation includes: (1) The rain fade protocol is functional detecting fades, providing an additional 10 dB of margin and seamless transitions to and from coded operation; (2) The stabilization of the link margins and the optimization of rain fade decision thresholds has resulted in improved BER performance; (3) Characterization of the fade compensation algorithm is ongoing.
Bellili, Faouzi; Meftehi, Rabii; Affes, Sofiene; Stephenne, Alex
2015-01-01
In this paper, we tackle for the first time the problem of maximum likelihood (ML) estimation of the signal-to-noise ratio (SNR) parameter over time-varying single-input multiple-output (SIMO) channels. Both the data-aided (DA) and the non-data-aided (NDA) schemes are investigated. Unlike classical techniques where the channel is assumed to be slowly time-varying and, therefore, considered as constant over the entire observation period, we address the more challenging problem of instantaneous (i.e., short-term or local) SNR estimation over fast time-varying channels. The channel variations are tracked locally using a polynomial-in-time expansion. First, we derive in closed-form expressions the DA ML estimator and its bias. The latter is subsequently subtracted in order to obtain a new unbiased DA estimator whose variance and the corresponding Cram\\'er-Rao lower bound (CRLB) are also derived in closed form. Due to the extreme nonlinearity of the log-likelihood function (LLF) in the NDA case, we resort to the expectation-maximization (EM) technique to iteratively obtain the exact NDA ML SNR estimates within very few iterations. Most remarkably, the new EM-based NDA estimator is applicable to any linearly-modulated signal and provides sufficiently accurate soft estimates (i.e., soft detection) for each of the unknown transmitted symbols. Therefore, hard detection can be easily embedded in the iteration loop in order to improve its performance at low to moderate SNR levels. We show by extensive computer simulations that the new estimators are able to accurately estimate the instantaneous per-antenna SNRs as they coincide with the DA CRLB over a wide range of practical SNRs.
Directory of Open Access Journals (Sweden)
L. Polak
2015-02-01
Full Text Available From the point of technical innovations the development and standardization of Digital Video Broadcasting – 2nd Generation Terrestrial (DVB-T2 and Long-Term Evolution (LTE systems are definitely the most significant results in the last decade. These systems have a very high potential to fulfill the highest user requirements, but they can operate in the same frequency spectrum. As a result, different co-existence scenarios can occur. In this paper, we explore and measure the co-existence between DVB-T2-Lite (e.g. portable TV and LTE multimedia services in ideal and portable fading channel models. Theoretical backgrounds of the investigated co-existence scenarios, proposal and realization of an appropriate workplace for their measuring and evaluation are presented and described. Moreover, deeper investigation of the mutual influence of the DVB-T2 system on the LTE one is also explored and graphically illustrated. The obtained results show that these co-existences could be critical for both systems from the point of providing multimedia services with a constant level of Quality of Services (QoS.
Do, Nhu Tri; Bao, Vo Nguyen Quoc; An, Beongku
2016-01-01
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. PMID:26927119
Wunderlich, S.; Welpot, M.; Gaspard, I.
2014-11-01
The markets for smart home products and services are expected to grow over the next years, driven by the increasing demands of homeowners considering energy monitoring, management, environmental controls and security. Many of these new systems will be installed in existing homes and offices and therefore using radio based systems for cost reduction. A drawback of radio based systems in indoor environments are fading effects which lead to a high variance of the received signal strength and thereby to a difficult predictability of the encountered path loss of the various communication links. For that reason it is necessary to derive a statistical path loss model which can be used to plan a reliable and cost effective radio network. This paper presents the results of a measurement campaign, which was performed in six buildings to deduce realistic radio channel models for a high variety of indoor radio propagation scenarios in the short range devices (SRD) band at 868 MHz. Furthermore, a potential concept to reduce the variance of the received signal strength using a circular polarized (CP) patch antenna in combination with a linear polarized antenna in an one-to-one communication link is presented.
Institute of Scientific and Technical Information of China (English)
罗骥; 袁东风
2005-01-01
Two different set partitioning strategies used in Turbo TCM, UP (Ungerboeck Partitioning) and BP (Block Partitioning) are compared over Rayleigh fading channels. The performance of Turbo TCM with the two set partitioning strategies and different frame length over Rayleigh fading channels is evaluated. The simulation results of 8PSK and 8ASK modulation and some significant conclusions are also given in this paper.%比较了衰落信道下两种不同的集分割方式,UP (Ungerboeck 分割) 和 BP (分组分割)对Turbo TCM性能的影响.研究了在两种不同映射以及不同帧长度下Turbo TCM的性能.并给出了在8PSK和8ASK两种调制方式下的仿真试验结果,通过比较得出了很有意义的结果.
Scheduling for dual-hop block-fading channels with two source-user pairs sharing one relay
Zafar, Ammar
2013-09-01
In this paper, we maximize the achievable rate region of a dual-hop network with two sources serving two users independently through a single shared relay. We formulate the problem as maximizing the sum of the weighted long term average throughputs of the two users under stability constraints on the long term throughputs of the source-user pairs. In order to solve the problem, we propose a joint user-and-hop scheduling scheme, which schedules the first or second hop opportunistically based on instantaneous channel state information, in order to exploit multiuser diversity and multihop diversity gains. Numerical results show that the proposed joint scheduling scheme enhances the achievable rate region as compared to a scheme that employs multi-user scheduling on the second-hop alone. Copyright © 2013 by the Institute of Electrical and Electronic Engineers, Inc.
Channel estimation in DCT-based OFDM.
Wang, Yulin; Zhang, Gengxin; Xie, Zhidong; Hu, Jing
2014-01-01
This paper derives the channel estimation of a discrete cosine transform-(DCT-) based orthogonal frequency-division multiplexing (OFDM) system over a frequency-selective multipath fading channel. Channel estimation has been proved to improve system throughput and performance by allowing for coherent demodulation. Pilot-aided methods are traditionally used to learn the channel response. Least square (LS) and mean square error estimators (MMSE) are investigated. We also study a compressed sensing (CS) based channel estimation, which takes the sparse property of wireless channel into account. Simulation results have shown that the CS based channel estimation is expected to have better performance than LS. However MMSE can achieve optimal performance because of prior knowledge of the channel statistic.
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
Frequency selectivity at very low centre frequencies
DEFF Research Database (Denmark)
Orellana, Carlos Andrés Jurado; Pedersen, Christian Sejer; Marquardt, Torsten
2010-01-01
A significant factor in the decrease of sensitivity to low-frequency sound is the helicotrema shunt effect. In humans, it causes a slope increase of the middle-ear transfer function (METF) from 6 dB/oct to 12 dB/oct below approximately 50 Hz [Marquardt et al., J.Acoust. Soc. Am. 121, 3628......-3638 (2007)]. Recent experiments showed that the exact frequency varies from individual to individual. Besides, the helicotrema region in the METF has been found to highly influence frequency selectivity for centre frequencies (CFs) below 80 Hz (Jurado and Moore in prep). By using individual METF...... in the shape of the METFs, thought to be affected by the helicotrema impedance. Preliminary analysis indicates that individual differences in the METFs might underlay the observed individual differences in frequency selectivity. Main effects predicted by the calculations are a pronounced flattening off...
瑞利衰落信道下SR-ARQ-AMS系统时延性能研究%On delay performance of SR-ARQ-AMS over Rayleigh fading channels
Institute of Scientific and Technical Information of China (English)
黎锁平; 高彦; 侯尚林; 马成业
2012-01-01
针对瑞利衰落信道,对一种结合选择式自动请求重传(SR-ARQ)技术的自适应调制系统(SR-ARQ-AMS)及其传输原理进行了分析,构造了一个有限状态Markov链来描述其瑞利衰落信道.利用等效时延的思想,建立了发送端带有休假的M/G/1非空竭服务排队模型描述该自适应调制系统.考虑了经有限次传输未成功分组的服务时延对系统时延性能的影响,求得了该系统分组平均等待时延、分组平均时延和归一化最大吞吐量的解析式.通过数值模拟分析了各参数对系统时延性能的影响,进而得到提高系统传输速率的方法.仿真结果表明SR-ARQ-AMS在瑞利衰落信道下能获得更好的系统时延性能.%Conventional adaptive transmission schemes performed poorly in wireless correlated slow-fading channels. The transmission scheme and the system model of adaptive modulation system combined with selective repeat automatic repeat request (SR-ARQ) over Rayleigh fading channels is analyzed firstly, a finite-state Markov chain is modeled for describing Rayleigh fading channels and adaptive modulation system. A queuing model with vacations is established by using the equivalent service delay method. The expression of system's main performance measures, such as system's average waiting delay time, average delay time and normalized maximum throughput are gained, which take into account the delay of lost packet transmitting limited times. The influence of various parameters on system delay is analyzed by numerical simulation and then we obtain the method to enhance system transmission efficiency. Numerical results show that SR-ARQ-AMS offers a better delay performance in Rayleigh fading channel.
Bell, David; Gevargiz, John; Vaisnys, Arvydas; Julian, David
1995-01-01
produce long delay multipath and create a frequency selective fading environment. Enter now OFDM, spread spectrum, equalization and other techniques that are capable of deconvolving the channel effects and effecting significant performance improvements by extracting the frequency diversity or time diversity components comprising the received signal.
Directory of Open Access Journals (Sweden)
Stevan M. Berber
2014-06-01
Full Text Available Chaotic spreading sequences can increase secrecy and resistance to interception in signal transmission. Chaos-based CDMA systems have been well investigated in the case of flat fading and noise presence in the channel. However, these systems operating in wideband channels, characterized by the frequency selective fading and white Gaussian noise, have not been investigated to the level of understanding their practical applications. This paper presents a detailed mathematical model of a CDMA system based on chaotic spreading sequences. In a theoretical analysis, all signals are represented in the discrete time domain. Using the theory of discrete time stochastic processes, the probability of error expressions are derived in a closed form for a multi-user chaos based CDMA system. For the sake of comparison, the expressions for the probability of error are derived separately for narrowband and wideband channels. The application of the system interleaving technique is investigated in particular, which showed that this technique can substantially improve probability of error in the system. The system is simulated and the findings of the simulation confirmed theoretically expected results. Possible improvements in the probability of bit error due to multipath channel nature, with and without interleavers, are quantified depending on the random delay and the number of users in the system. In the analyzed system, a simplified version of the wideband channel model, proposed for modern wideband wireless networks, is used. Introduction Over the past years, the demand for wireless communications has increased substantially due to advancements in mobile communication systems and networks. Following these increasing demands, modern communication systems require the ability to handle a large number of users to process and transmit wideband signals through complex frequency selective channels. One of the techniques for transmission of multi-user signals is the
A frequency selective acoustic transducer for directional Lamb wave sensing.
Senesi, Matteo; Ruzzene, Massimo
2011-10-01
A frequency selective acoustic transducer (FSAT) is proposed for directional sensing of guided waves. The considered FSAT design is characterized by a spiral configuration in wavenumber domain, which leads to a spatial arrangement of the sensing material producing output signals whose dominant frequency component is uniquely associated with the direction of incoming waves. The resulting spiral FSAT can be employed both for directional sensing and generation of guided waves, without relying on phasing and control of a large number of channels. The analytical expression of the shape of the spiral FSAT is obtained through the theoretical formulation for continuously distributed active material as part of a shaped piezoelectric device. Testing is performed by forming a discrete array through the points of the measurement grid of a scanning laser Doppler vibrometer. The discrete array approximates the continuous spiral FSAT geometry, and provides the flexibility to test several configurations. The experimental results demonstrate the strong frequency dependent directionality of the spiral FSAT and suggest its application for frequency selective acoustic sensors, to be employed for the localization of broadband acoustic events, or for the directional generation of Lamb waves for active interrogation of structural health.
Adaptive rain fade compensation
Rautio, J. C.
1980-01-01
A large available margin must be provided for satellite communications systems operating near 20 GHz, which occasionally experience fades due to rain attenuation. It is proposed that this margin may be achieved in high-capacity FDMA satellites by dynamically providing a large margin to those links which are experiencing deep fades, while maintaining a small fade margin on all others. Single-beam SCPC operation and multiple-beam, satellite-switched FDMA systems are described, and the optimization of the dynamic FDMA links in a severely fading environment is investigated. A solution is derived which takes into account: (1) transponder intermodulation distortion, (2) cochannel and cross-polarization antenna interference, and (3) rain fade characteristics. The sample system configuration presented shows that such systems reach availability levels approaching 0.9999 at Ka-Band.
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...
Frequency Selective Surfaces with Nanoparticles Unit Cell
Directory of Open Access Journals (Sweden)
Nga Hung Poon
2015-09-01
Full Text Available The frequency selective surface (FSS is a periodic structure with filtering performance for optical and microwave signals. The general periodic arrays made with patterned metallic elements can act as an aperture or patch on a substrate. In this work, two kinds of materials were used to produce unit cells with various patterns. Gold nanoparticles of 25 nm diameter were used to form periodic monolayer arrays by a confined photocatalytic oxidation-based surface modification method. As the other material, silver gel was used to create multiple layers of silver. Due to the ultra-thin nature of the self-assembled gold nanoparticle monolayer, it is very easy to penetrate the FSS with terahertz radiation. However, the isolated silver islands made from silver gel form thicker multiple layers and contribute to much higher reflectance. This work demonstrated that multiple silver layers are more suitable than gold nanoparticles for use in the fabrication of FSS structures.
RBF multiuser detector with channel estimation capability in a synchronous MC-CDMA system.
Ko, K; Choi, S; Kang, C; Hong, D
2001-01-01
The authors propose a multiuser detector with channel estimation capability using a radial basis function (RBF) network in a synchronous multicarrier-code division multiple access (MC-CDMA) system. The authors propose to connect an RBF network to the frequency domain to effectively utilize the frequency diversity. Simulations were performed over frequency-selective and multi-path fading channels. These simulations confirmed that the proposed receiver can be used both for the channel estimation and as a multi-user receiver, thus permitting an increase in the number of active users.
Weighted Max-Min Resource Allocation for Frequency Selective Channels
Zehavi, Ephi; Levanda, Ronny; Han, Zhu
2010-01-01
In this paper, we discuss the computation of weighted max-min rate allocation using joint TDM/FDM strategies under a PSD mask constraint. We show that the weighted max-min solution allocates the rates according to a predetermined rate ratio defined by the weights, a fact that is very valuable for telecommunication service providers. Furthermore, we show that the problem can be efficiently solved using linear programming. We also discuss the resource allocation problem in the mixed services scenario where certain users have a required rate, while the others have flexible rate requirements. The solution is relevant to many communication systems that are limited by a power spectral density mask constraint such as WiMax, Wi-Fi and UWB.
Directory of Open Access Journals (Sweden)
James Osuru Mark
2011-01-01
Full Text Available The multicarrier code division multiple access (MC-CDMA system has received a considerable attention from researchers owing to its great potential in achieving high data rates transmission in wireless communications. Due to the detrimental effects of multipath fading the performance of the system degrades. Similarly, the impact of non-orthogonality of spreading codes can exist and cause interference. This paper addresses the performance of multicarrier code division multiple access system under the influence of frequency selective generalized η-µ fading channel and multiple access interference caused by other active users to the desired one. We apply Gaussian approximation technique to analyse the performance of the system. The avearge bit error rate is derived and expressed in Gauss hypergeometic functions. Maximal ratio combining diversity technique is utilized to alleviate the deleterious effect of multipath fading. We observed that the system performance improves when the parameter η increase or decreasse in format 1 or format 2 conditions respectively.
Flexible frequency selective metamaterials for microwave applications.
Gao, Bo; Yuen, Matthew M F; Ye, Terry Tao
2017-03-21
Metamaterials have attracted more and more research attentions recently. Metamaterials for electromagnetic applications consist of sub-wavelength structures designed to exhibit particular responses to an incident EM (electromagnetic) wave. Traditional EM (electromagnetic) metamaterial is constructed from thick and rigid structures, with the form-factor suitable for applications only in higher frequencies (above GHz) in microwave band. In this paper, we developed a thin and flexible metamaterial structure with small-scale unit cell that gives EM metamaterials far greater flexibility in numerous applications. By incorporating ferrite materials, the thickness and size of the unit cell of metamaterials have been effectively scaled down. The design, mechanism and development of flexible ferrite loaded metamaterials for microwave applications is described, with simulation as well as measurements. Experiments show that the ferrite film with permeability of 10 could reduce the resonant frequency. The thickness of the final metamaterials is only 0.3mm. This type of ferrite loaded metamaterials offers opportunities for various sub-GHz microwave applications, such as cloaks, absorbers, and frequency selective surfaces.
Continuous metal plasmonic frequency selective surfaces.
Zhang, Jianfa; Ou, Jun-Yu; Papasimakis, Nikitas; Chen, Yifang; Macdonald, Kevin F; Zheludev, Nikolay I
2011-11-07
In the microwave part of the spectrum, where losses are minimal, metal films regularly patterned (perforated) on the sub-wavelength scale achieve spectral selectivity by balancing the transmission and reflection characteristics of the surface. Here we show for optical frequencies, where joule losses are important, that periodic structuring of a metal film without violation of continuity (i.e. without perforation) is sufficient to achieve substantial modification of reflectivity. By engineering the geometry of the structure imposed on a surface one can dramatically change the perceived color of the metal without employing any form of chemical modification, thin-film coating or diffraction effects. This novel frequency selective effect is underpinned by plasmonic Joule losses in the constituent elements of the patterns (dubbed 'intaglio' and 'bas relief' metamaterials to distinguish indented and raised structures respectively) and is specific to the optical part of the spectrum. It has the advantage of maintaining the integrity of metal surfaces and is well suited to high-throughput fabrication via techniques such as nano-imprint.
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
In this paper, a new scheme that combines Space-Time Block-Coding (STBC) based on an Alamouti-like scheme and the Least Squares (LS) channel estimation using optimal training sequences in Cyclic-Prefix-based (CP)\\Single-Carrier (SC) systems is proposed. With two transmit antennas, based on Cramer-Rao lower bound for channel estimation, it is shown that the Periodic Complementary Set (PCS) is optimal over frequency-selective fading channels. Compared with the normal scheme without STBC, 3dB Mean Square Error (MSE) performance gains and fewer restrictions on the length of channel impulse response are demonstrated.
Institute of Scientific and Technical Information of China (English)
白鹭; 郭静波
2011-01-01
本文在文献[1]的基础上，研究多径衰落信道条件下采用无先导卡尔曼滤波混沌拟合对混沌直扩通信的可破解性．由针对混沌直扩信号的无先导卡尔曼滤波混沌拟合的状态空间方程出发，分析了多径衰落信道对于无先导卡尔曼滤波混沌拟合过程中的跟踪误差的影响，得到了信息码状态估计的值域范围，从而提出了多径衰落信道下混沌直扩信号可被破解的充分条件定理．仿真结果表明，在满足充分条件下，混沌直扩信号无论是通过时不变信道还是时变信道，都可以被成功破解，并且具有良好的误码率性能．%Blind demodulation （breaking） of chaotic direct sequence spread spectrum （CD3S） signals is a challenging and leading issue under muhipath fading channel in the field of chaotic communication. Until now, there are neither equalization methods to remove the impact of the channel, nor the immediate breaking methods. Based on the existing study, the breakability of CD3S signals is analyzed under multipath fading channel by using unscented Kalman filter （UKF） chaotic fitting in this paper. Beginning with the state space equation for the CD3S signals in UKF chaotic fitting, the channel influence on the tracking error is analyzed in the process of UKF chaotic fitting, then the range of the message state estimation is derived, and finally a sufficient condition theorem is proposed for the CD3S signals to be broken. Simulation results show that CD3S signals can be broken successfully under the proposed condition with excellent performance of bit error rate （BER） , no matter whether the channel characteristic is either time-invariant or time-variant.
Frequency selective surfaces with multiple periodic elements
Reed, Jeffrey Alan
A thorough computer design study using the method of Chen1,2,3 was undertaken for band-pass filters constructed from frequency selective surfaces (FSSs). The FSSs, modeled as thin, perfectly conducting surfaces with periodically arranged apertures, were designed to produce a transmission profile with a bandpass characteristic centered at 10.6 μm and to have various specified bandwidths. The effects of aperture shape and dimensions, configuration and periodicity of the aperture array, and presence of a dielectric substrate were examined in- depth. For comparison purposes, a complimentary array of metallic patches was also examined. The successful design (a thin, planar sheet of aluminum perforated with narrow rectangular apertures in a triangular array configuration on a thick zinc selenide substrate) provided a preliminary set of basic design rules for creating bandpass filters from FSSs. Dual resonance transmission profiles were generated by considering a FSS with a group of apertures as the periodic element. Chen's method1,2,3 was modified to work with periodic groups of up to four rectangular or circular shaped apertures (or metallic patches). Combinations of different length narrow slot apertures, combinations of square and narrow slot apertures, and variation of periodicity along alternating rows of narrow slot apertures, all produced a dual resonance transmission profile in the computer model. For the combination of different length narrow apertures, the dual resonance resulted from the natural resonance associated with the two different length narrow apertures, while for the combination of squares and narrow slots, an enhancement of the Wood's anomaly at the diffraction edge created the second resonance peak. Variation of the periodicity along alternating rows produced a dual resonance because each of the 'superimposed arrays' had a different periodicity. The presence of Wood's anomalies in the transmission profile was also examined. Finally, 'proof of
Institute of Scientific and Technical Information of China (English)
王世练; 胡登鹏; 张智力; 卢树军
2015-01-01
为提高差分混沌键控的传输效率及其在衰落信道下的传输性能，提出了多载波混沌键控及类差分混沌键控检测方法，发射端每隔 M个 OFDM符号间隔插入由混沌参考信号构成的“导频”，在此间隔内其他 M－1个 OFDM符号即以此混沌参考信号生成的混沌键控信号，接收端提取“导频”并将之与其他 OFDM符号进行相关积分，恢复出 M－1比特信息。进一步给出了 MIMO 多径衰落信道下的多载波混沌键控分集发射与接收方法，发射端采用不同混沌信号以获得一定的发射分集增益，接收端不需要任何信道先验信息，对各天线的相关积分输出进行等增益合并，可获得空间分集增益和频域分集增益。性能分析和计算机仿真表明，在“导频”插入间隔大于2的情况下，多载波混沌键控的功率效率大于差分混沌键控，且传输性能优于差分混沌键控。%To improve the frequency efficiency and the transmission performance of differential chaos shift keying under wireless fading channel,a multi-carrier chaotic shift keying communication scheme is proposed.In each block size of MOFDMsymbols,one pilot OFDMsymbol inserted time-spaced in all-frequency is used to transmit the reference chaotic signal and the other M-1 OFDM symbols is used to transmit the information-bearing signals,which spread by the reference chaotic signal.At the receiver,a differential detector is constructed and the information bits from the correlations between the pilot OFDMsymbol and the other M-1 OFDMsymbols in each block size of Mare recovered.A multi-carrier chaotic shift keying transceiver under MIMO multipath fading channels with no channel state information is presented,in which a distinct chaotic sequence at each transmit antenna is used to spread the same data symbol and the detection statistics at each receive antenna are combined with equal gain for symbol detection.Both performance analysis
Memory Can Fade After Menopause
... page: https://medlineplus.gov/news/fullstory_161930.html Memory Can Fade After Menopause But women still outperform ... their own age, but new research suggests that memory may fade as estrogen levels drop during menopause. ...
HF Detecting Radar and Communication Frequency Selection System
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Real time communication (RTC) frequency selecting system is used to the maximum usable frequency (MUF) between two communication points, then finds the best frequency between 0. 85 MUF and 1.0MUF. Determination of electric wave delay is mostly introduced, and of MUF values, the form of frequencycontrolling code and relative interface circuits in the frequency selecting system are introduced in detail.
2013-09-01
5 4.1 NAKAGAMI -M FADING CHANNEL MODEL ...................................................................... 6 5. SIMULATION...modeled using a Nakagami -m distribution. A special instance of the Nakagami -m multipath fading channel is the Rayleigh fading channel, which is...decomposed into the following contributions and losses: , (7) where LAPM is the propagation loss calculated by APM. 4.1 NAKAGAMI -M FADING CHANNEL
Optimal training sequences for MIMO systems under correlated fading
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The optimal design of training sequences for channel estimation in multiple-input multiple-output (MIMO) systems under spatially correlated fading is considered.The channel is assumed to be a block-fading model with spatial correlation known at both the transmitter and the receiver.To minimize the channel estimation error,optimal training sequences are designed to exploit full information of the spatial correlation under the criterion of minimum mean square error (MMSE).It is investigated that the spatial correlation is helpful to decrease the estimation error and the proposed training sequences have good performance via simulations.
Institute of Scientific and Technical Information of China (English)
罗骥; 张曦林; 袁东风
2005-01-01
提出了一种改进型的Code-Matched交织器,它能减少低重量码的数量,从而提高Turbo码的性能.这种改进型的Code-Matched交织器可以适用于多种不同生成矩阵产生的Turbo码,而且不会影响Turbo码在中高信噪比处的性能.同时,在Rayleigh信道下,这种交织器能降低错误平台.%A novel Code-Matched interleaver is proposed which decreases the number of the low weight codewords to improve the performance of the Turbo code. The modified design can adapt more kinds of Turbo codes determined by the generator matrix, while it doesn't decrease the bit error rate performance of Turbo codes at moderate to high signal to noise ratio. At the same time, in Rayleigh fading channel, the new Code-Matched interleaver can also debase the error floor.
Institute of Scientific and Technical Information of China (English)
徐凌伟; 张浩; 吕婷婷; 施威; Gulliver T A
2015-01-01
The Average Symbol Error Probability(ASEP)and Outage Probability(OP)of the Switched Diversity Com-bining(SDC)receiving system under n-Rayleigh fading channels are investigated in this paper. Based on the method of the Probability Density Function(PDF)of the Signal-to-Noise Ratio(SNR), the exact and approximate expressions of the ASEP are derived for several q-ary modulation schemes, including Phase Shift Keying modulation(PSK), and Pulse Ampli-tude Modulation(PAM). The exact closed form expressions of OP are also presented. Then the ASEP and OP perfor-mance under different conditions is evaluated through numerical simulations, and the accuracy of the analytical results is verified. The simulation results show that the diversity branches L, the fading factor n, and the switching threshold rth have an important influence on the ASEP and OP performance.%在n-Rayleigh信道下，研究了切换合并接收系统的平均符号误码率和中断概率性能。基于信噪比的概率密度函数的方法，推导了切换合并接收系统在n-Rayleigh衰落信道上采用q进制相移键控调制，和脉冲幅度调制的平均符号误码率的精确和近似表达式。同时，也得到了中断概率的精确闭合表达式。对不同系统条件下的平均符号误码率和中断概率性能做了数值仿真，验证了理论分析结果的正确性。仿真结果表明：分集支路数L，衰弱因子n，以及切换门限rth对系统的平均符号误码率和中断概率性能有着重要的影响。
Directory of Open Access Journals (Sweden)
D. Krstic
2016-12-01
Full Text Available In this paper, wireless mobile communication system with macrodiversity reception is considered. Macrodiversity system is consisting of macrodiversity selection combining (SC receiver and three microdiversity SC receivers. Propagation channel suffers α-μ short term fading and Gamma long term fading resulting in system performance degradation. Analytical closed form expression for average level crossing rate (LCR of macrodiversity SC receiver output signal envelope is obtained. Mathematical results are analyzed, presenting the influence of long term fading parameters and short term fading parameters on average level crossing rate. Obtained results can be used in the process of simulation and design of real-world environments mobile cellular telecommunication systems.
Paulson, Kevin S.; Basarudin, Hafiz
2011-08-01
Several research groups in Europe are developing joint channel simulators for arbitrarily complex networks of terrestrial and slant path, microwave telecommunications links. Currently, the Hull Rain Fade Network Simulator (HRFNS) developed at University of Hull can simulate rain fade on arbitrary terrestrial networks in the southern United Kingdom, producing joint rain fade time series with a 10 s integration time. This paper reports on work to broaden the function of the existing HRFNS to include slant paths such as Earth-space links and communications to high altitude platforms and unmanned airborne systems. The area of application of the new simulation tool is being extended to the whole of Europe, and other fade mechanisms are being included. Nimrod/OPERA has been chosen as the input meteorological data sets for the new system to simulate rain fade. Zero-degree isotherm heights taken from NCEP/NCAR Reanalysis Data are used in conjunction with the Eden-Bacon sleet (wet snow) model to introduce melting layer effects. Other fading mechanisms, including cloud fade, scintillation and absorption losses by atmospheric gasses, can be added to the simulator. The simulator is tested against ITU-R models for rain fade distribution experienced by terrestrial and Earth-space links in the southern United Kingdom. Statistics of fade dynamics, i.e., fade slope and fade duration, for a simulated Earth-space link are compared to International Telecommunication Union models.
Frequency Selectivity Behaviour in the Auditory Midbrain: Implications of Model Study
Institute of Scientific and Technical Information of China (English)
KUANG Shen-Bing; WANG Jia-Fu; ZENG Ting
2006-01-01
By numerical simulations on frequency dependence of the spiking threshold, i.e. on the critical amplitude of periodic stimulus, for a neuron to fire, we find that bushy cells in the cochlear nuclear exhibit frequency selectivity behaviour. However, the selective frequency band of a bushy cell is far away from that of the preferred spectral range in human and mammal auditory perception. The mechanism underlying this neural activity is also discussed. Further studies show that the ion channel densities have little impact on the selective frequency band of bushy cells. These findings suggest that the neuronal behaviour of frequency selectivity in bushy cells at both the single cell and population levels may be not functionally relevant to frequency discrimination. Our results may reveal a neural hint to the reconsideration on the bushy cell functional role in auditory information processing of sound frequency.
Hadzi-Velkov, Zoran
2009-01-01
This letter provides closed-form expressions for the outage probability, the average level crossing rate (LCR) and the average fade duration (AFD) of a dual diversity selection combining (SC) system exposed to the combined influence of the cochannel interference (CCI) and the thermal noise (AWGN) in Nakagami fading channel. The branch selection is based on the desired signal power SC algorithm with all input signals assumed to be independent, while the powers of the desired signals in all diversity branches are mutually equal but distinct from the power of the interference signals. The analytical results reduce to known solutions in the cases of an interference-limited system in Rayleigh fading and an AWGN-limited system in Nakagami fading. The average LCR is determined by an original approach that does not require explicit knowledge of the joint PDF of the envelope and its time derivative, which also paves the way for similar analysis of other diversity systems.
Performance analysis of selection diversity in Nakagami fading channel%选择式合并方法在Nakagami信道上的性能分析
Institute of Scientific and Technical Information of China (English)
陈云飞; 罗汉文; 宋文涛
2001-01-01
This paper proceeds an evaluation of selection diversity inNakagami fa ding channel according to the principle of maximum output level.Closed form expr ession of bit error rate is derived and compared with the principle of maximum s ignal noise ratio.Numerical result shows a slight deterioration but a great redu ction of complexity.%文根据最大输出电平准则，对选择式合并在Nakagami信道上的性能作了比以往理论分析更符合实际的评价，导出了误码率的闭式解，并与最大信噪比准则时作了比较。结果表明，采用最大输出电平准则时系统的性能稍有恶化，但实现的复杂度却大为降低。
Directory of Open Access Journals (Sweden)
Basile L. AGBA
2008-06-01
Full Text Available Mobile ad hoc networks (MANET are very difficult to design in terms of scenarios specification and propagation modeling. All these aspects must be taken into account when designing MANET. For cost-effective designing, powerful and accurate simulation tools are needed. Our first contribution in this paper is to provide a global approach process (GAP in channel modeling combining scenarios and propagation in order to have a better analysis of the physical layer, and finally to improve performances of the whole network. The GAP is implemented in an integrated simulation tool, Ad-SMPro. Moreover, channel statistics, throughput and delay are some key points to be considered when studying a mobile wireless networks. A carefully analysis of mobility effects over second order channel statistics and system performances is made based on our optimized simulation tool, Ad-SMProl. The channel is modeled by large scale fading and small scale fading including Doppler spectrum due to the double mobility of the nodes. Level Cross Rate and Average Duration of Fade are simulated as function of double mobility degree, a defined to be the ratio of the nodes' speeds. These results are compared to the theoretical predictions. We demonstrate that, in mobile ad hoc networks, flat fading channels and frequency-selective fading channels are differently affected. In addition, Bit Error rate is analysed as function of the ratio of the average bit energy to thermal noise density. Other performances (such as throughput, delay and routing traffic are analysed and conclusions related to the proposed simulation model and the mobility effects are drawn.
Institute of Scientific and Technical Information of China (English)
啜钢; 刘振兴; 王涛
2011-01-01
To solve the complicated problem of analysis of outage performance in cooperative communication system, a theoretical analysis method is proposed. A selection relay model with a direct link over independent identically distributed Nakagami-m fading channels is considered based on the power restricted cooperative communication system. An analytical expression of outage probability is derived and the outage performance is analyzed for this model. The optimal power allocation is also investigated and a power allocation factor in a specific relay number is given. Simulations show that the outage performance is evidently improved compared with other selection relay models. The optimal power allocation ia also investigated and a power allocation factor in a specific relay number is given.%为了解决协作通信系统中选择中继算法中断性能分析复杂的问题,提出了一种新的中断分析方法.基于功率受限协作通信系统,考虑Nakagami-m独立同分布信道下一种带有直通链路的选择中继模型,在该模型下推导了中断概率表达式,分析了系统的中断性能,经仿真验证了理论分析的准确性.探讨了优化功率分配,给出特定中继数情况下的功率分配系数.分析结果表明,在该模型下的中断性能与已有模型相比均有所提高.
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.
Frequency Selective Surfaces for extended Bandwidth backing reflector functions
Pasian, M.; Neto, A.; Monni, S.; Ettorre, M.; Gerini, G.
2008-01-01
This paper deals with the use of Frequency Selective Surfaces (FSS) to increase the Efficiency × Bandwidth product in Ultra-Wide Band (UWB) antenna arrays whose efficiency is limited by the front-to-back ratio. If the backing reflector is realized in one metal plane solution its location will be sui
Multiple Fading Factors Kalman Filter for SINS Static Alignment Application
Institute of Scientific and Technical Information of China (English)
GAO Weixi; MIAO Lingjuan; NI Maolin
2011-01-01
To solve the problem that the standard Kalman filter cannot give the optimal solution when the system model and stochastic information are unknown accurately,single fading factor Kalman filter is suitable for simple systems.But for complex systems with multi-variable,it may not be sufficient to use single fading factor as a multiplier for the covariance matrices.In this paper,a new multiple fading factors Kalman filtering algorithm is presented.By calculating the unbiased estimate of the innovation sequence covariance using fenestration,the fading factor matrix is obtained.Adjusting the covariance matrix of prediction error Pk|k-1 using fading factor matrix,the algorithm provides different rates of fading for different filter channels.The proposed algorithm is applied to strapdown inertial navigation system(SINS) initial alignment,and simulation and experimental results demonstrate that,the alignment accuracy can be upgraded dramatically when the actual system noise characteristics are different from the pre-set values.The new algorithm is less sensitive to uncertainty noise and has better estimation effect of the parameters.Therefore,it is of significant value in practical applications.
Institute of Scientific and Technical Information of China (English)
李泳志; 陶成; 刘留; 卢艳萍; 刘凯
2016-01-01
该文考虑一种分布式大规模MIMO系统，假设基站端与用户之间的信道为莱斯信道，研究了该系统中基站选择的算法。首先给出了系统采用匹配滤波和迫零预编码时，用户下行可达速率的闭式表达式，并分析了系统的功率效率性能。然后基于此闭式表达式，以最大化系统的频谱效率为目标，提出了基于增量选择和基于用户优先级的基站选择算法。这两种算法只需要系统获取基站端与用户之间的信道统计特征信息，从而有效降低了系统开销。仿真结果表明，所提出的两种基站选择算法性能仍能逼近最优算法。特别地，当采用匹配滤波预编码且基站端天线数趋于无穷时，基于用户优先级的基站选择算法优于基于增量选择的算法。%The Base Station (BS) selection for distributed massive MIMO system is studied. The channels between the BSs and the users are assumed to be Rician fading. First the closed-form expressions of downlink achievable rates for Matched-Filter (MF) and Zero-Forcing (ZF) precoding are derived respectively, and the power efficiency performance of the system is investigated. Based on the closed-form expressions, the approximate incremental BS selection and the approximate user priority BS selection algorithms are proposed, both of which only require the statistical Channel State Information (CSI), to maximize the system spectral efficiency. Numerical results show that the proposed algorithms perform close to the optimal one. Specifically, it is shown that the approximate user priority BS selection algorithm outperforms the approximate incremental one when the BSs utilize the MF precoding in the large scale antenna limit.
1980-01-01
2348 Robert Wallace Raytheon (617) 762-6700 J. A. O’Brien DCEC/R210 (703) 437-2266 Gayton Yancey Raytheon (617) 762-6700 George H. Hagn SRI International (703) 524-2053 David R. Smith DCEC/R220 (703) 437-2316 A- 2
Time-Frequency Based Channel Estimation for High-Mobility OFDM Systems-Part I: MIMO Case
Önen, Erol; Akan, Aydın; Chaparro, LuisF
2010-12-01
Multiple-input multiple-output (MIMO) systems hold the potential to drastically improve the spectral efficiency and link reliability in future wireless communications systems. A particularly promising candidate for next-generation fixed and mobile wireless systems is the combination of MIMO technology with Orthogonal Frequency Division Multiplexing (OFDM). OFDM has become the standard method because of its advantages over single carrier modulation schemes on multipath, frequency selective fading channels. Doppler frequency shifts are expected in fast-moving environments, causing the channel to vary in time, that degrades the performance of OFDM systems. In this paper, we present a time-varying channel modeling and estimation method based on the Discrete Evolutionary Transform to obtain a complete characterization of MIMO-OFDM channels. Performance of the proposed method is evaluated and compared on different levels of channel noise and Doppler frequency shifts.
A Full Performance Analysis of Channel Estimation Methods for Time Varying OFDM Systems
Aida, Zaier; 10.5121/ijmnct.2011.1201
2012-01-01
In this paper, we have evaluated various methods of time-frequency-selective fading channels estimation in OFDM system and some of them improved under time varying conditions. So, these different techniques will be studied through different algorithms and for different schemes of modulations (16 QAM, BPSK, QPSK, ...). Channel estimation gathers different schemes and algorithms, some of them are dedicated for slowly time varying (such as block type arrangement insertion, Bayesian Cramer-Rao Bound, Kalman estimator, Subspace estimator, ...) whereas the others concern highly time varying channels (comb type insertion, ...). There are others methods that are just suitable for stationary channels like blind or semi blind estimators. For this aim, diverse algorithms were used for these schemes such as Least Squares estimator LS, Least Minimum Squares LMS, Minimum Mean-Square-Error MMSE, Linear Minimum Mean-Square-Error LMMSE, Maximum Likelihood ML, ... to refine estimators shown previously.
Random Matrix Model for Nakagami-Hoyt Fading
Kumar, Santosh; 10.1109/TIT.2010.2044060
2011-01-01
Random matrix model for the Nakagami-q (Hoyt) fading in multiple-input multiple-output (MIMO) communication channels with arbitrary number of transmitting and receiving antennas is considered. The joint probability density for the eigenvalues of H{\\dag}H (or HH{\\dag}), where H is the channel matrix, is shown to correspond to the Laguerre crossover ensemble of random matrices and is given in terms of a Pfaffian. Exact expression for the marginal density of eigenvalues is obtained as a series consisting of associated Laguerre polynomials. This is used to study the effect of fading on the Shannon channel capacity. Exact expressions for higher order density correlation functions are also given which can be used to study the distribution of channel capacity.
Directory of Open Access Journals (Sweden)
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.
Conceptual Study of OFDM-Coding, PAPR Reduction, Channel Estimation
Directory of Open Access Journals (Sweden)
S S Riya Rani
2014-06-01
Full Text Available At present for high data rate transmission, Orthogonal Frequency Division Multiplexing (OFDM which is one of multi-carrier modulation (MCM techniques offers a considerable spectral efficiency; multipath delay spread tolerance, immunity to the frequency selective fading channels and power efficiency. As a result, OFDM has widely been deployed in many wireless communication standards such as Digital Video Broadcasting (DVB.In using turbo codes for OFDM performance can be sufficiently improved as seen in LTE standard systems. One of the challenging issues for Orthogonal Frequency Division Multiplexing (OFDM system is its high Peak-to-Average Power Ratio (PAPR. In this paper we present turbo coded OFDM systems, its channel estimation scheme and methods for reducing PAPR in the system.
Pätzold, Matthias
2011-01-01
Providing a comprehensive overview of the modelling, analysis and simulation of mobile radio channels, this book gives a detailed understanding of fundamental issues and examines state-of-the-art techniques in mobile radio channel modelling. It analyses several mobile fading channels, including terrestrial and satellite flat-fading channels, various types of wideband channels and advanced MIMO channels, providing a fundamental understanding of the issues currently being investigated in the field. Important classes of narrowband, wideband, and space-time wireless channels are explored in deta
On Comparison of DFT-Based and DCT-Based Channel Estimation for OFDM System
Directory of Open Access Journals (Sweden)
Saqib Saleem
2011-05-01
Full Text Available For high data rate communication with the required Quality of Service (QoS in 3G and 4G systems, Orthogonal Frequency Division Multiplexing (OFDM is proposed, which is capable to resist the channel impairments caused by high mobility conditions, by dividing the frequency-selective fading channel into narrowband flat fading channels. In this paper two time-domain channel estimation techniques, Discrete Fourier Transform (DFT and Discrete Cosine Transform (DCT, are compared based on the time-domain channel impulse response (CIR energy characteristics and they have less complexity and efficient performance than Linear Minimum Mean Square Error (LMMSE and Least Square Error (LSE. The effect of power limitation in terms of SNR and the number of multipaths for a wireless channel is determined to compare these transform approaches. Two well known performance criteria: Mean Square Error (MSE and Symbol Error Rate (SER are used for comparison by using Monte Carlo Simulations for Quadrature Phase Shift Keying (QPSK modulation.
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.
Gui, Guan; Xu, Li; Shan, Lin; Adachi, Fumiyuki
2014-01-01
In orthogonal frequency division modulation (OFDM) communication systems, channel state information (CSI) is required at receiver due to the fact that frequency-selective fading channel leads to disgusting intersymbol interference (ISI) over data transmission. Broadband channel model is often described by very few dominant channel taps and they can be probed by compressive sensing based sparse channel estimation (SCE) methods, for example, orthogonal matching pursuit algorithm, which can take the advantage of sparse structure effectively in the channel as for prior information. However, these developed methods are vulnerable to both noise interference and column coherence of training signal matrix. In other words, the primary objective of these conventional methods is to catch the dominant channel taps without a report of posterior channel uncertainty. To improve the estimation performance, we proposed a compressive sensing based Bayesian sparse channel estimation (BSCE) method which cannot only exploit the channel sparsity but also mitigate the unexpected channel uncertainty without scarifying any computational complexity. The proposed method can reveal potential ambiguity among multiple channel estimators that are ambiguous due to observation noise or correlation interference among columns in the training matrix. Computer simulations show that proposed method can improve the estimation performance when comparing with conventional SCE methods.
Wireless structural sensor made with frequency selective surface antenna
Jang, Sang-Dong; Kim, Jaehwan
2012-04-01
Nondestructive Structural health monitoring (SHM) system using wireless sensor network is the one of important issue for aerospace and civil engineering. Chipless passive wireless sensor system is one of novel methods for SHM which uses the electromagnetic wave characteristic change by geometrical change of electromagnetic resonators or impedance change of functional material sensing part without RFID chip. In this paper, the chipless passive wireless SHM sensor using frequency selective surface (FSS) is investigated. Electromagnetic characteristic change of FSS by mechanical strain or structural damage is investigated by simulation and experiment.
Channel estimation based on distributed compressed sensing in amplify-and-forward relay networks
Institute of Scientific and Technical Information of China (English)
WANG Dong-hao; NIU Kai; HE Zhi-qiang; TIAN Bao-yu
2010-01-01
In orthogonal frequency-division multiplexing(OFDM)amplify-and-forward(AF)relay networks,in order to exploit diversity gains over frequency-selective fading channels,the receiver needs to acquire the knowledge of channel state information(CSI).In this article,based on the recent methodology of distributed compressed sensing(DCS),a novel channel estimation scheme is proposed.The joint sparsity model 2(JSM-2)in DCS theory and simultaneous orthogonal matching pursuit(SOMP)are both introduced to improve the estimation performance and increase the spectral efficiency.Simulation results show that compared with current compressed sensing(CS)methods,the estimation error of our scheme is reduced dramatically in high SNR region while the pilot number is still kept small.
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.
Boutin, Karl; Lecours, Michel; Pelletier, Marcel; Delisle, Gilles Y.
1990-01-01
In a mobile satellite system with a frequency reuse cellular configuration, significant co-channel interference can be experienced due to the antenna sidelobe level. The signal will be subjected not only to its own fading, but also to the effect of the varying degree of fading on co-channel interferer, and this interference will behave differently in the up and in the down link. This paper presents a quantitative evaluation of the combined effects of fades and co-channel interference on a mobile satellite link.
A review of fade detection techniques
Pergal, F. J.
1990-01-01
Several proposed propagation fade detection techniques are reviewed in light of general requirements presented for beacon fade characterization. The discussion includes an analysis of phase lock versus frequency lock beacon tracking loops and of excess noise injection type radiometers. The Advanced Communications Technology Satellite (ACTS) beacon fade detection schemes proposed by the Communications Satellite Corporation and the Jet Propulsion Laboratory are examined along with the fade detection technique used by Harris in the Advanced Communications Technology Satellite (ACTS) low burst rate (LBR) terminal.
Fading Types in Wireless Communications Systems
Directory of Open Access Journals (Sweden)
R. Reiz
2008-05-01
Full Text Available In this paper fading models areconsidered. In particular we divide the models intothree classes by separating the received signal in threescale of spatial variation such as fast fading, slow fading(shadowing and path loss. Moreover, several models forsmall scale fading are considered such as Rayleigh,Ricean, Nakagami and Weibull distributions. Slowfading is also investigated as well as serial and site-tositecorrelations are compared.
Perceptual Fading without Retinal Adaptation
Hsieh, Po-Jang; Colas, Jaron T.
2012-01-01
A retinally stabilized object readily undergoes perceptual fading and disappears from consciousness. This startling phenomenon is commonly believed to arise from local bottom-up sensory adaptation to edge information that occurs early in the visual pathway, such as in the lateral geniculate nucleus of the thalamus or retinal ganglion cells. Here…
Institute of Scientific and Technical Information of China (English)
白慧卿; 金梁; 钟州; 黄开枝
2015-01-01
针对现有物理层安全编码方法对信道差异利用不充分导致安全间隙较大的问题，本文首先建立了衰落信道下的物理层安全传输模型；然后通过分析不同衰落幅度下私密信息的译码错误概率，给出了与信道衰落幅度特征相匹配的私密信息隐藏位置选取规则；最后结合私密信息置乱将译码残余比特错误扩散到整个码字中，进一步提高窃听者对私密信息的译码错误概率。仿真结果表明，该方法的安全间隙比直接传输和仅私密信息置乱的方法分别缩小了23.5dB 和4.5dB。%This paper focused on the problem that the existing physical layer secrecy coding has a large security gap caused by the insufficient using of channel characteristic difference.Firstly,this study established a physical layer secrecy transmission model in fading channel.Then through the analysis of the bit error probability of confidential information under different channel fading amplitude,a channel fading amplitude matched confidential information hiding place selection rule is given.Finally the scrambling was used to spread the error to the whole code words,which increased Eve’s error probabil-ity.The simulation results show that the security gap of this method is reduced by 23.5dB and 4.5dB compared with direct transfer and scrambling,respectively.
Frequency selective surface structure optimized by genetic algorithm
Institute of Scientific and Technical Information of China (English)
Lu Jun; Wang Jian-Bo; Sun Guan-Cheng
2009-01-01
Frequency selective surface(FSS)is a two-dimensional periodic structure which has prominent characteristics of bandpass or bandblock when interacting with electromagnetic waves.In this paper,the thickness,the dielectric constant,the element graph and the arrangement periodicity of an FSS medium are investigated by Genetic Algorithm(GA)when an electromagnetic wave is incident on the FSS at a wide angle,and an optimized FSS structure and transmission characteristics are obtained.The results show that the optimized structure has better stability in relation to incident angle of electromagnetic wave and preserves the stability of centre frequency even at an incident angle as large as 80°,thereby laying the foundation for the application of FSS to curved surfaces at wide angles.
Optically transparent frequency selective surfaces on flexible thin plastic substrates
Energy Technology Data Exchange (ETDEWEB)
Dewani, Aliya A., E-mail: a.ashraf@griffith.edu.au; O’Keefe, Steven G.; Thiel, David V.; Galehdar, Amir [School Of Electrical Engineering, Griffith University, Brisbane, 4111 (Australia)
2015-02-15
A novel 2D simple low cost frequency selective surface was screen printed on thin (0.21 mm), flexible transparent plastic substrate (relative permittivity 3.2). It was designed, fabricated and tested in the frequency range 10-20 GHz. The plane wave transmission and reflection coefficients agreed with numerical modelling. The effective permittivity and thickness of the backing sheet has a significant effect on the frequency characteristics. The stop band frequency reduced from 15GHz (no backing) to 12.5GHz with polycarbonate. The plastic substrate thickness beyond 1.8mm has minimal effect on the resonant frequency. While the inner element spacing controls the stop-band frequency, the substrate thickness controls the bandwidth. The screen printing technique provided a simple, low cost FSS fabrication method to produce flexible, conformal, optically transparent and bio-degradable FSS structures which can find their use in electromagnetic shielding and filtering applications in radomes, reflector antennas, beam splitters and polarizers.