WorldWideScience

Sample records for voice channel capacity

  1. On Cellular MIMO Channel Capacity

    Science.gov (United States)

    Adachi, Koichi; Adachi, Fumiyuki; Nakagawa, Masao

    To increase the transmission rate without bandwidth expansion, the multiple-input multiple-output (MIMO) technique has recently been attracting much attention. The MIMO channel capacity in a cellular system is affected by the interference from neighboring co-channel cells. In this paper, we introduce the cellular channel capacity and evaluate its outage capacity, taking into account the frequency-reuse factor, path loss exponent, standard deviation of shadowing loss, and transmission power of a base station (BS). Furthermore, we compare the cellular MIMO downlink channel capacity with those of other multi-antenna transmission techniques such as single-input multiple-output (SIMO) and space-time block coded multiple-input single-output (STBC-MISO). We show that the optimum frequency-reuse factor F that maximizes 10%-outage capacity is 3 and both 50%- and 90%-outage capacities is 1 irrespective of the type of multi-antenna transmission technique, where q%-outage capacity is defined as the channel capacity that gives an outage probability of q%. We also show that the cellular MIMO channel capacity is always higher than those of SIMO and STBC-MISO.

  2. Quantum channel capacities - multiparty communication

    CERN Document Server

    Demianowicz, M; Demianowicz, Maciej; Horodecki, Pawel

    2006-01-01

    We analyze different aspects of multiparty communication over quantum memoryless channels and generalize some of key results known from bipartite channels to that of multiparty scenario. In particular, we introduce multiparty versions of minimal subspace transmission fidelity and entanglement transmission fidelity. We also provide alternative, local, versions of fidelities and show their equivalence to the global ones in context of capacity regions defined. The equivalence of two different capacity notions with respect to two types of the fidelities is proven. In analogy to bipartite case it is shown, via sufficiency of isometric encoding theorem, that additional classical forward side channel does not increase capacity region of any quantum channel with $k$ senders and $m$ receivers which represents a compact unit of general quantum networks theory. The result proves that recently provided capacity region of multiple access channel ([M. Horodecki et al, Nature {\\bf 436} 673 (2005)], [J.Yard et al, quant-ph/0...

  3. Capacities of quantum amplifier channels

    Science.gov (United States)

    Qi, Haoyu; Wilde, Mark M.

    2017-01-01

    Quantum amplifier channels are at the core of several physical processes. Not only do they model the optical process of spontaneous parametric down-conversion, but the transformation corresponding to an amplifier channel also describes the physics of the dynamical Casimir effect in superconducting circuits, the Unruh effect, and Hawking radiation. Here we study the communication capabilities of quantum amplifier channels. Invoking a recently established minimum output-entropy theorem for single-mode phase-insensitive Gaussian channels, we determine capacities of quantum-limited amplifier channels in three different scenarios. First, we establish the capacities of quantum-limited amplifier channels for one of the most general communication tasks, characterized by the trade-off between classical communication, quantum communication, and entanglement generation or consumption. Second, we establish capacities of quantum-limited amplifier channels for the trade-off between public classical communication, private classical communication, and secret key generation. Third, we determine the capacity region for a broadcast channel induced by the quantum-limited amplifier channel, and we also show that a fully quantum strategy outperforms those achieved by classical coherent-detection strategies. In all three scenarios, we find that the capacities significantly outperform communication rates achieved with a naive time-sharing strategy.

  4. The design of a digital voice data compression technique for orbiter voice channels

    Science.gov (United States)

    1975-01-01

    Voice bandwidth compression techniques were investigated to anticipate link margin difficulties in the shuttle S-band communication system. It was felt that by reducing the data rate on each voice channel from the baseline 24 (or 32) Kbps to 8 Kbps, additional margin could be obtained. The feasibility of such an alternate voice transmission system was studied. Several factors of prime importance that were addressed are: (1) achieving high quality voice at 8 Kbps; (2) performance in the presence of the anticipated shuttle cabin environmental noise; (3) performance in the presence of the anticipated channel error statistics; and (4) minimal increase in size, weight, and power over the current baseline voice processor.

  5. A TDM link with channel coding and digital voice.

    Science.gov (United States)

    Jones, M. W.; Tu, K.; Harton, P. L.

    1972-01-01

    The features of a TDM (time-division multiplexed) link model are described. A PCM telemetry sequence was coded for error correction and multiplexed with a digitized voice channel. An all-digital implementation of a variable-slope delta modulation algorithm was used to digitize the voice channel. The results of extensive testing are reported. The measured coding gain and the system performance over a Gaussian channel are compared with theoretical predictions and computer simulations. Word intelligibility scores are reported as a measure of voice channel performance.

  6. Analytical Expression for the MIMO Channel Capacity

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yifei; ZHAO Ming; XIAO Limin; WANG Jing

    2006-01-01

    This paper presents analytical expressions for the multiple-input multiple-output (MIMO) channel capacity in frequency-flat Rayleigh fading environments. An exact analytical expression is given for the ergodic capacity for single-input multiple-output (SIMO) channels. The analysis shows that the SIMO channel capacity can be approximated by a Gaussian random variable and that the MIMO channel capacity can be approximated as the sum of multiple SIMO capacities. The SIMO channel results are used to derive approximate closed-form expressions for the MIMO channel ergodic capacity and the complementary cumulative distribution function (CCDF) of the MIMO channel capacity (outage capacity). Simulations show that these theoretical results are good approximations for MIMO systems with an arbitrary number of transmit or receive antennas. Moreover, these analytical expressions are relatively simple which makes them very useful for practical computations.

  7. The quantum capacity with symmetric side channels

    CERN Document Server

    Smith, G; Winter, A; Smith, Graeme; Smolin, John A.; Winter, Andreas

    2006-01-01

    We present an upper bound for the quantum channel capacity that is both additive and convex. Our bound can be interpreted as the capacity of a channel for high-fidelity communication when assisted by the family of all channels mapping symmetrically to their output and environment. The bound seems to be quite tight, and for degradable quantum channels it coincides with the unassisted channel capacity. Using this symmetric side channel capacity, we find new upper bounds on the capacity of the depolarizing channel. We also briefly indicate an analogous notion for distilling entanglement using the same class of (one-way) channels, yielding one of the few genuinely 1-LOCC monotonic entanglement measures.

  8. Ergodic channel capacity of the spatial correlated rayleigh MIMO channel

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hui-ping; WU Ping; LIU Ai-jun

    2007-01-01

    The theoretical capacity of the spatial correlated Rayleigh multiple input multiple output (MIMO) channel is an important issue in MIMO technology. In this article, an ergodic channel capacity formula of the spatial correlated rayleigh MIMO channel is provided, which is deduced when two antennas exist at either the transmitter or the receiver. The multi-dimensional least-squares fit algorithm is employed to narrow the difference between the theoretical formula capacity and the practical capacity. Simulation results show that the theoretical capacity approaches the practical one closely.

  9. Secrecy Capacity over Correlated Ergodic Fading Channel

    CERN Document Server

    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...

  10. Effective capacity of correlated MISO channels

    KAUST Repository

    Zhong, Caijun

    2011-06-01

    This paper presents an analytical performance investigation of the capacity limits of correlated multiple-input single-output (MISO) channels in the presence of quality-of-service (QoS) requirements. Exact closed-form expression for the effective capacity of correlated MISO channels is derived. In addition, simple expressions are obtained at the asymptotic high and low signal-to-noise ratio (SNR) regimes, which provide insights into the impact of various system parameters on the effective capacity of the system. Also, a complete characterization of the impact of spatial correlation on the effective capacity is provided with the aid of a majorization theory result. The findings suggest that antenna correlation reduce the effective capacity of the channels. Moreover, a stringent QoS requirement causes a significant reduction in the effective capacity but this can be effectively alleviated by increasing the number of antennas. © 2011 IEEE.

  11. Capacity of Discrete Molecular Diffusion Channels

    CERN Document Server

    Einolghozati, Arash; Beirami, Ahmad; Fekri, Faramarz

    2011-01-01

    In diffusion-based molecular communications, messages can be conveyed via the variation in the concentration of molecules in the medium. In this paper, we intend to analyze the achievable capacity in transmission of information from one node to another in a diffusion channel. We observe that because of the molecular diffusion in the medium, the channel possesses memory. We then model the memory of the channel by a two-step Markov chain and obtain the equations describing the capacity of the diffusion channel. By performing a numerical analysis, we obtain the maximum achievable rate for different levels of the transmitter power, i.e., the molecule production rate.

  12. Modified MIMO Cube for Enhanced Channel Capacity

    Directory of Open Access Journals (Sweden)

    Lajos Nagy

    2012-01-01

    Full Text Available This paper deals with the optimization of MIMO antenna elements' position in modified MIMO cube for getting maximal channel capacity in indoor environment. The dependence of the channel capacity on the antenna orientation was analyzed by simulations. We have also examined the effect of the frequency dependence of the antenna system (in case of conjugate matching and nonconjugate matching for the channel capacity. Based on the simulation results in the created and measured antenna system, the antennas were at a right angle to each other. At the two chosen different structures, we measured the antenna parameters and the channel capacity. In this paper, we present the results of the measurements which clearly confirm our simulations. We will point out the differences between the two antenna structures.

  13. Ergodic Capacity for the SIMO Nakagami- Channel

    Directory of Open Access Journals (Sweden)

    Vagenas EfstathiosD

    2009-01-01

    Full Text Available This paper presents closed-form expressions for the ergodic channel capacity of SIMO (single-input and multiple output wireless systems operating in a Nakagami- fading channel. As the performance of SIMO channel is closely related to the diversity combining techniques, we present closed-form expressions for the capacity of maximal ratio combining (MRC, equal gain combining (EGC, selection combining (SC, and switch and stay (SSC diversity systems operating in Nakagami- fading channels. Also, the ergodic capacity of a SIMO system in a Nakagami- fading channel without any diversity technique is derived. The latter scenario is further investigated for a large amount of receive antennas. Finally, numerical results are presented for illustration.

  14. A New Covert Channel over Cellular Voice Channel in Smartphones

    OpenAIRE

    Aloraini, Bushra; Johnson, Daryl; Stackpole, Bill; Mishra, Sumita

    2015-01-01

    Investigating network covert channels in smartphones has become increasingly important as smartphones have recently replaced the role of traditional computers. Smartphones are subject to traditional computer network covert channel techniques. Smartphones also introduce new sets of covert channel techniques as they add more capabilities and multiple network connections. This work presents a new network covert channel in smartphones. The research studies the ability to leak information from the...

  15. Twenty-Channel Voice Response System.

    Science.gov (United States)

    1981-06-01

    programs and vocabulary. 0 Telephone Company (TELCO) Switched Lines - provides access to VRS using telephones. * Bell 407C Data Sets - Converts the Touch...from the twenty 407C units. 0 DLII-E - Asynchronous interface to the 11/34 unibus for the VOTRAX unit. * 20 Channel ADPCM Decoder - a specially designed

  16. Sensitivity of Noncoherent WSSUS Fading Channel Capacity

    CERN Document Server

    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...

  17. Secrecy Outage Capacity of Fading Channels

    CERN Document Server

    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...

  18. Capacity Bounds for Parallel Optical Wireless Channels

    KAUST Repository

    Chaaban, Anas

    2016-01-01

    A system consisting of parallel optical wireless channels with a total average intensity constraint is studied. Capacity upper and lower bounds for this system are derived. Under perfect channel-state information at the transmitter (CSIT), the bounds have to be optimized with respect to the power allocation over the parallel channels. The optimization of the lower bound is non-convex, however, the KKT conditions can be used to find a list of possible solutions one of which is optimal. The optimal solution can then be found by an exhaustive search algorithm, which is computationally expensive. To overcome this, we propose low-complexity power allocation algorithms which are nearly optimal. The optimized capacity lower bound nearly coincides with the capacity at high SNR. Without CSIT, our capacity bounds lead to upper and lower bounds on the outage probability. The outage probability bounds meet at high SNR. The system with average and peak intensity constraints is also discussed.

  19. Channel Capacity Estimation using Free Probability Theory

    CERN Document Server

    Ryan, Øyvind

    2007-01-01

    In many channel measurement applications, one needs to estimate some characteristics of the channels based on a limited set of measurements. This is mainly due to the highly time varying characteristics of the channel. In this contribution, it will be shown how free probability can be used for channel capacity estimation in MIMO systems. Free probability has already been applied in various application fields such as digital communications, nuclear physics and mathematical finance, and has been shown to be an invaluable tool for describing the asymptotic behaviour of many systems when the dimensions of the system get large (i.e. the number of antennas). In particular, introducing the notion of free deconvolution, we provide hereafter an asymptotically (in the number of antennas) unbiased capacity estimator (w.r.t. the number of observations) for MIMO channels impaired with noise. Another unbiased estimator (for any number of observations) is also constructed by slightly modifying the free probability based est...

  20. Quantum biological channel modeling and capacity calculation.

    Science.gov (United States)

    Djordjevic, Ivan B

    2012-12-10

    Quantum mechanics has an important role in photosynthesis, magnetoreception, and evolution. There were many attempts in an effort to explain the structure of genetic code and transfer of information from DNA to protein by using the concepts of quantum mechanics. The existing biological quantum channel models are not sufficiently general to incorporate all relevant contributions responsible for imperfect protein synthesis. Moreover, the problem of determination of quantum biological channel capacity is still an open problem. To solve these problems, we construct the operator-sum representation of biological channel based on codon basekets (basis vectors), and determine the quantum channel model suitable for study of the quantum biological channel capacity and beyond. The transcription process, DNA point mutations, insertions, deletions, and translation are interpreted as the quantum noise processes. The various types of quantum errors are classified into several broad categories: (i) storage errors that occur in DNA itself as it represents an imperfect storage of genetic information, (ii) replication errors introduced during DNA replication process, (iii) transcription errors introduced during DNA to mRNA transcription, and (iv) translation errors introduced during the translation process. By using this model, we determine the biological quantum channel capacity and compare it against corresponding classical biological channel capacity. We demonstrate that the quantum biological channel capacity is higher than the classical one, for a coherent quantum channel model, suggesting that quantum effects have an important role in biological systems. The proposed model is of crucial importance towards future study of quantum DNA error correction, developing quantum mechanical model of aging, developing the quantum mechanical models for tumors/cancer, and study of intracellular dynamics in general.

  1. Quantum Biological Channel Modeling and Capacity Calculation

    Directory of Open Access Journals (Sweden)

    Ivan B. Djordjevic

    2012-12-01

    Full Text Available Quantum mechanics has an important role in photosynthesis, magnetoreception, and evolution. There were many attempts in an effort to explain the structure of genetic code and transfer of information from DNA to protein by using the concepts of quantum mechanics. The existing biological quantum channel models are not sufficiently general to incorporate all relevant contributions responsible for imperfect protein synthesis. Moreover, the problem of determination of quantum biological channel capacity is still an open problem. To solve these problems, we construct the operator-sum representation of biological channel based on codon basekets (basis vectors, and determine the quantum channel model suitable for study of the quantum biological channel capacity and beyond. The transcription process, DNA point mutations, insertions, deletions, and translation are interpreted as the quantum noise processes. The various types of quantum errors are classified into several broad categories: (i storage errors that occur in DNA itself as it represents an imperfect storage of genetic information, (ii replication errors introduced during DNA replication process, (iii transcription errors introduced during DNA to mRNA transcription, and (iv translation errors introduced during the translation process. By using this model, we determine the biological quantum channel capacity and compare it against corresponding classical biological channel capacity. We demonstrate that the quantum biological channel capacity is higher than the classical one, for a coherent quantum channel model, suggesting that quantum effects have an important role in biological systems. The proposed model is of crucial importance towards future study of quantum DNA error correction, developing quantum mechanical model of aging, developing the quantum mechanical models for tumors/cancer, and study of intracellular dynamics in general.

  2. Secrecy Capacity Region of Fading Broadcast Channels

    CERN Document Server

    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.

  3. Information capacities of quantum measurement channels

    Science.gov (United States)

    Holevo, A. S.

    2013-03-01

    We study the relation between the unassisted and entanglement-assisted classical capacities C and Cea of entanglement-breaking channels. We argue that the gain of entanglement assistance Cea/C > 1 generically for measurement channels with unsharp observables; in particular for the measurements with pure posterior states the information loss in the entanglement-assisted protocol is zero, resulting in an arbitrarily large gain for very noisy or weak signal channels. This is illustrated by examples of continuous observables corresponding to state tomography in finite dimensions and heterodyne measurement. In contrast, state preparations are characterized by the property of having no gain of entanglement assistance, Cea/C = 1.

  4. Capacity of Sparse Wideband Channels with Partial Channel Feedback

    CERN Document Server

    Hariharan, Gautham; Sayeed, Akbar M

    2008-01-01

    This paper studies the ergodic capacity of wideband multipath channels with limited feedback. Our work builds on recent results that have established the possibility of significant capacity gains in the wideband/low-SNR regime when there is perfect channel state information (CSI) at the transmitter. Furthermore, the perfect CSI benchmark gain can be obtained with the feedback of just one bit per channel coefficient. However, the input signals used in these methods are peaky, that is, they have a large peak-to-average power ratios. Signal peakiness is related to channel coherence and many recent measurement campaigns show that, in contrast to previous assumptions, wideband channels exhibit a sparse multipath structure that naturally leads to coherence in time and frequency. In this work, we first show that even an instantaneous power constraint is sufficient to achieve the benchmark gain when perfect CSI is available at the receiver. In the more realistic non-coherent setting, we study the performance of a tra...

  5. Private Capacity of Quantum Channels is Not Additive

    Science.gov (United States)

    Li, Ke; Winter, Andreas; Zou, Xubo; Guo, Guangcan

    2009-09-01

    Recently there has been considerable activity on the subject of the additivity of various quantum channel capacities. Here, we construct a family of channels with a sharply bounded classical and, hence, private capacity. On the other hand, their quantum capacity when combined with a zero private (and zero quantum) capacity erasure channel becomes larger than the previous classical capacity. As a consequence, we can conclude for the first time that the classical private capacity is nonadditive. In fact, in our construction even the quantum capacity of the tensor product of two channels can be greater than the sum of their individual classical private capacities. We show that this violation occurs quite generically: every channel can be embedded into our construction, and a violation occurs whenever the given channel has a larger entanglement-assisted quantum capacity than (unassisted) classical capacity.

  6. The Holevo capacity of a generalized amplitude-damping channel

    Institute of Scientific and Technical Information of China (English)

    Hou Li-Zhen; Fang Mao-Fa

    2007-01-01

    The Holevo capacity of a generalized amplitude-damping channel is investigated by using a numerical method.It is shown that the Holevo capacity depends on the channel parameters representing the ambient temperature and fidelity. In particular, under a special condition, the Holevo capacity of the generalized amplitude-damping channel can be written as an analytical expression.

  7. Quasi-superactivation for the classical capacity of quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Gyongyosi, Laszlo, E-mail: gyongyosi@hit.bme.hu [Quantum Technologies Laboratory, Department of Telecommunications, Budapest University of Technology and Economics, 2 Magyar tudosok krt, Budapest, H-1117, Hungary and Information Systems Research Group, Mathematics and Natural Sciences, Hungarian Ac (Hungary); Imre, Sandor [Quantum Technologies Laboratory, Department of Telecommunications, Budapest University of Technology and Economics, 2 Magyar tudosok krt, Budapest, H-1117 (Hungary)

    2014-12-04

    The superactivation effect has its roots in the extreme violation of additivity of the channel capacity and enables to reliably transmit quantum information over zero-capacity quantum channels. In this work we demonstrate a similar effect for the classical capacity of a quantum channel which previously was thought to be impossible.

  8. Entanglement required in achieving entanglement-assisted channel capacities

    CERN Document Server

    Bowen, G

    2002-01-01

    Entanglement shared between the two ends of a quantum communication channel has been shown to be a useful resource in increasing both the quantum and classical capacities for these channels. The entanglement-assisted capacities were derived assuming an unlimited amount of shared entanglement per channel use. In this paper, bounds are derived on the minimum amount of entanglement required per use of a channel, in order to asymptotically achieve the capacity. This is achieved by introducing a class of entanglement-assisted quantum codes. Codes for classes of qubit channels are shown to achieve the quantum entanglement-assisted channel capacity when an amount of shared entanglement per channel given by, E = 1 - Q_E, is provided. It is also shown that for very noisy channels, as the capacities become small, the amount of required entanglement converges for the classical and quantum capacities.

  9. Shannon Meets Nyquist: Capacity Limits of Sampled Analog Channels

    CERN Document Server

    Chen, Yuxin; Goldsmith, Andrea J

    2011-01-01

    We explore two fundamental questions at the intersection of sampling theory and information theory: how is channel capacity affected by sampling below the channel's Nyquist rate, and what sub-Nyquist sampling strategy should be employed to maximize capacity. In particular, we first derive the capacity of sampled analog channels for two prevalent sampling mechanisms: filtering followed by sampling and sampling following filter banks. Connections between sampling and MIMO Gaussian channels are illuminated based on this analysis. Optimal prefilters that maximize capacity are identified for both cases, as well as several kinds of channels for which these sampling mechanisms are optimal to maximize capacity at sub-Nyquist rates. We also highlight connections between sampled analog channel capacity and minimum mean squared error estimation from sampled data. In particular, it is shown that for both filtering and filter-bank sampling strategies, the filters maximizing capacity and minimizing mean squared error are e...

  10. CAPACITY ALLOCATION IN A COMPETITIVE MULTI-CHANNEL SUPPLY CHAIN

    Institute of Scientific and Technical Information of China (English)

    Kaijun LIU; Zigang ZHANG

    2007-01-01

    This paper addresses the capacity allocation problem for a capacitated manufacturer who can distribute her product to the end customers through an independent retailer channel as well as through her direct channel. Demands of the channels are substitutable, which induces competition between them. We show that to avoid channel competition, it is possible for the manufacturer to deny the retailer of capacity. Specifically, if channel substitution rate is high, a retailer of low demand will never be allocated any capacity even when the available capacity is ample. While, if the channel substitution rate is low, capacity allocation strategy depends on the retailer's demand and the available capacity.Many other interesting managerial insights are provided and illustrated with numerical examples.

  11. Trade-off capacities of the quantum Hadamard channels

    CERN Document Server

    Bradler, Kamil; Touchette, Dave; Wilde, Mark M

    2010-01-01

    Coding theorems in quantum Shannon theory express the ultimate rates at which a sender can transmit information over a noisy quantum channel. More often than not, the known formulas expressing these transmission rates are intractable, requiring an optimization over an infinite number of uses of the channel. Researchers have rarely found quantum channels with a tractable classical or quantum capacity, but when such a finding occurs, it demonstrates a complete understanding of that channel's capabilities for transmitting classical or quantum information. Here, we show that the three-dimensional capacity region for entanglement-assisted transmission of classical and quantum information is tractable for the Hadamard class of channels. Examples of Hadamard channels include generalized dephasing channels, cloning channels, and the Unruh channel. The generalized dephasing channels and the cloning channels are natural processes that occur in quantum systems through the loss of quantum coherence or stimulated emission...

  12. A note on quantum entropy inequalities and channel capacities

    Science.gov (United States)

    Fan, Heng

    2003-12-01

    Quantum entropy inequalities are studied. Some quantum entropy inequalities are obtained by several methods. For an entanglement breaking channel, we show that the entanglement-assisted classical capacity is upper bounded by log d. A relationship between entanglement-assisted and one-shot unassisted capacities is obtained. This relationship shows the entanglement-assisted channel capacity is upper bounded by the sum of log d and the one-shot unassisted classical capacity.

  13. Inequalities and Separations Among Assisted Capacities of Quantum Channels

    Science.gov (United States)

    Bennett, Charles H.; Devetak, Igor; Shor, Peter W.; Smolin, John A.

    2006-04-01

    We exhibit quantum channels whose classical and quantum capacities, when assisted by classical feedback, exceed their unassisted classical Holevo capacity. These channels are designed to be noisy in a way that can be corrected with the help of the output and a reference system entangled with part of the input. A similar construction yields quantum channels whose classical capacity, when assisted by two-way classical communication independent of the source, exceeds their classical capacity assisted by feedback alone. We give a hierarchy of capacity inequalities and open questions.

  14. Methods for Estimating Capacities of Gaussian Quantum Channels

    CERN Document Server

    Pilyavets, Oleg V; Mancini, Stefano

    2009-01-01

    We present a perturbative approach to the problem of estimating capacities of Gaussian quantum channels. It relies on the expansion of the von Neumann entropy of Gaussian states as a function of the symplectic eigenvalues of the quadratures covariance matrices. We apply this method to the classical capacity of a lossy bosonic channel for both the memory and memoryless cases.

  15. The Holevo-Schumacher-Westmoreland Channel Capacity for a Class of Qudit Unital Channels

    CERN Document Server

    Cortese, J A

    2004-01-01

    The Holevo-Schumacher-Westmoreland (HSW) classical (entanglement-unassisted) channel capacity for a class of qudit unital channels is shown to be C = log2(d) - Smin, where d is the dimension of the qudit, and Smin is the minimum possible von Neumann entropy at the channel output. The HSW channel capacity for tensor products of this class of unital qudit channels is shown to obey the same formula.

  16. Upper Capacity Bounds of MIMO Wireless Systems Through Fading Channels

    Directory of Open Access Journals (Sweden)

    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.

  17. Channel capacities of an exactly solvable spin-star system

    Science.gov (United States)

    Arshed, Nigum; Toor, A. H.; Lidar, Daniel A.

    2010-06-01

    We calculate the entanglement-assisted and -unassisted channel capacities of an exactly solvable spin star system, which models the quantum dephasing channel. The capacities for this non-Markovian model exhibit a strong dependence on the coupling strengths of the bath spins with the system, the bath temperature, and the number of bath spins. For equal couplings and bath frequencies, the channel becomes periodically noiseless.

  18. Channel Capacities of an Exactly Solvable Spin-Star System

    CERN Document Server

    Arshed, N; Lidar, D A

    2010-01-01

    We calculate the entanglement-assisted and unassisted channel capacities of an exactly solvable spin star system, which models the quantum dephasing channel. The capacities for this non-Markovian model exhibit a strong dependence on the coupling strengths of the bath spins with the system, the bath temperature, and the number of bath spins. For equal couplings and bath frequencies, the channel becomes periodically noiseless.

  19. Capacity Comparison of CDMA and TDMA in Vector Broadcast Channel

    Institute of Scientific and Technical Information of China (English)

    ZHAO Shao-gang; XIAO Zhen-grong; WU Wei-ling

    2004-01-01

    The sum-rate capacity of CDMA and TDMA in vector broadcast channel is researched. An upper bound of sum-rate capacity in CDMA system and a lower bound of sum-rate capacity in TDMA system are derived respectively. According to these two bounds, the ratio of the two bounds at most can achieve min(M,K). Here M is the antenna number of the transmitter and K is the number of the user in this vector broadcast channel.

  20. Statistical-mechanical analysis of multiuser channel capacity with imperfect channel state information

    Institute of Scientific and Technical Information of China (English)

    Wang Hui-Song; Zeng Gui-Hua

    2008-01-01

    In this paper,the effect of imperfect channel state information at the receiver, which is caused by noise and other interference, on the multi-access channel capacity is analysed through a statistical-mechanical approach. Replica analyses focus on analytically studying how the minimum mean square error (MMSE) channel estimation error appears in a multiuser channel capacity formula. And the relevant mathematical expressions are derived. At the same time,numerical simulation results are demonstrated to validate the Replica analyses. The simulation results show how the system parameters, such as channel estimation error, system load and signal-to-noise ratio, affect the channel capacity.

  1. Expansion coding: Achieving the capacity of an AEN channel

    CERN Document Server

    Koyluoglu, O Ozan; Si, Hongbo; Vishwanath, Sriram

    2012-01-01

    A general method of coding over expansions is proposed, which allows one to reduce the highly non-trivial problem of coding over continuous channels to a much simpler discrete ones. More specifically, the focus is on the additive exponential noise (AEN) channel, for which the (binary) expansion of the (exponential) noise random variable is considered. It is shown that each of the random variables in the expansion corresponds to independent Bernoulli random variables. Thus, each of the expansion levels (of the underlying channel) corresponds to a binary symmetric channel (BSC), and the coding problem is reduced to coding over these parallel channels while satisfying the channel input constraint. This optimization formulation is stated as the achievable rate result, for which a specific choice of input distribution is shown to achieve a rate which is arbitrarily close to the channel capacity in the high SNR regime. Remarkably, the scheme allows for low-complexity capacity-achieving codes for AEN channels, using...

  2. Design of a digital voice data compression technique for orbiter voice channels

    Science.gov (United States)

    1975-01-01

    Candidate techniques were investigated for digital voice compression to a transmission rate of 8 kbps. Good voice quality, speaker recognition, and robustness in the presence of error bursts were considered. The technique of delayed-decision adaptive predictive coding is described and compared with conventional adaptive predictive coding. Results include a set of experimental simulations recorded on analog tape. The two FM broadcast segments produced show the delayed-decision technique to be virtually undegraded or minimally degraded at .001 and .01 Viterbi decoder bit error rates. Preliminary estimates of the hardware complexity of this technique indicate potential for implementation in space shuttle orbiters.

  3. On E-Capacity Region of the Wiretap Channel

    Directory of Open Access Journals (Sweden)

    Nasrin Afshar

    2013-09-01

    Full Text Available We study the E-capacity region of the wiretap channel. A random coding bound for E-capacity region is obtained. When E tends to 0, the proposed inner bound converges to the capacity region obtained by Csiszár and Körner

  4. Effective capacity of multiple antenna channels: Correlation and keyhole

    KAUST Repository

    Zhong, Caijun

    2012-01-01

    In this study, the authors derive the effective capacity limits for multiple antenna channels which quantify the maximum achievable rate with consideration of link-layer delay-bound violation probability. Both correlated multiple-input single-output and multiple-input multiple-output keyhole channels are studied. Based on the closed-form exact expressions for the effective capacity of both channels, the authors look into the asymptotic high and low signal-to-noise ratio regimes, and derive simple expressions to gain more insights. The impact of spatial correlation on effective capacity is also characterised with the aid of a majorisation theory result. It is revealed that antenna correlation reduces the effective capacity of the channels and a stringent quality-of-service requirement causes a severe reduction in the effective capacity but can be alleviated by increasing the number of antennas. © 2012 The Institution of Engineering and Technology.

  5. Capacity of Fading Channels in the Low Power Regime

    KAUST Repository

    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

  6. Capacity Regions and Sum-Rate Capacities of Vector Gaussian Interference Channels

    CERN Document Server

    Shang, Xiaohu; Kramer, Gerhard; Poor, H Vincent

    2009-01-01

    The capacity regions of vector, or multiple-input multiple-output, Gaussian interference channels are established for very strong interference and aligned strong interference. Furthermore, the sum-rate capacities are established for Z interference, noisy interference, and mixed (aligned weak/intermediate and aligned strong) interference. These results generalize known results for scalar Gaussian interference channels.

  7. OPRA capacity bounds for selection diversity over generalized fading channels

    KAUST Repository

    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.

  8. Secrecy Capacity of a Class of Orthogonal Relay Eavesdropper Channels

    Directory of Open Access Journals (Sweden)

    Aggarwal Vaneet

    2009-01-01

    Full Text Available The secrecy capacity of relay channels with orthogonal components is studied in the presence of an additional passive eavesdropper node. The relay and destination receive signals from the source on two orthogonal channels such that the destination also receives transmissions from the relay on its channel. The eavesdropper can overhear either one or both of the orthogonal channels. Inner and outer bounds on the secrecy capacity are developed for both the discrete memoryless and the Gaussian channel models. For the discrete memoryless case, the secrecy capacity is shown to be achieved by a partial decode-and-forward (PDF scheme when the eavesdropper can overhear only one of the two orthogonal channels. Two new outer bounds are presented for the Gaussian model using recent capacity results for a Gaussian multiantenna point-to-point channel with a multiantenna eavesdropper. The outer bounds are shown to be tight for two subclasses of channels. The first subclass is one in which the source and relay are clustered, and the eavesdropper receives signals only on the channel from the source and the relay to the destination, for which the PDF strategy is optimal. The second is a subclass in which the source does not transmit to the relay, for which a noise-forwarding strategy is optimal.

  9. K-user Interference Channels: General Outer Bound and Sum-capacity for Certain Gaussian Channels

    CERN Document Server

    Tuninetti, Daniela

    2011-01-01

    This paper derives an outer bound on the capacity region of a general memoryless interference channel with an arbitrary number of users. The derivation follows from a generalization of the techniques developed by Kramer and by Etkin et al for the Gaussian two-user channel. The derived bound is the first known outer bound valid for any memoryless channel. In Gaussian noise, classes of channels for which the proposed bound gives the sum-rate capacity are identified, including degraded channels and a class of Z-channels.

  10. Capacities of Lossy Bosonic Memory Channels

    Science.gov (United States)

    Lupo, Cosmo; Giovannetti, Vittorio; Mancini, Stefano

    2010-01-01

    We introduce a general model describing correlated noise effects in quantum optical communication via attenuating media. The memory effects account for the environment finite relaxation times, which are unavoidable in any realistic model. The use of a proper set of collective field variables allows us to unravel the memory, showing that the n-fold concatenation of the memory channel is unitarily equivalent to the direct product of n single-mode lossy bosonic channels. We then compute the ultimate (classical and quantum) transmission rates, showing their enhancement with respect to the memoryless case and proving that coherent state encoding is optimal.

  11. On Capacity Regions of Interference Channels with Mismatched Local Views

    CERN Document Server

    Kao, David T -H

    2011-01-01

    We study the capacity regions of two-user interference channels where transmitters base their transmission decisions on local views of the channel state. Under the local view model, each transmitter knows only a subset of the four channel gains, which may be mismatched from the other transmitter. We consider a set of seven local views, and find that for five out of the seven local views, TDMA is sufficient to achieve the capacity region of the deterministic interference channel. Conversely for these five views, no policy can achieve a rate point outside the TDMA region without inducing a corner case of sub-TDMA performance in another channel state. The common trait shared by the two remaining local views - those with the potential to outperform TDMA - is transmitter knowledge of the outgoing interference link, emphasizing its importance in creating opportunities to use more advanced schemes. Our conclusions are extended to bounded gap characterizations of the capacity region for the Gaussian interference chan...

  12. Ergodic Capacity for the SIMO Nakagami-m Channel

    Directory of Open Access Journals (Sweden)

    Efstathios D. Vagenas

    2009-01-01

    Full Text Available This paper presents closed-form expressions for the ergodic channel capacity of SIMO (single-input and multiple output wireless systems operating in a Nakagami-m fading channel. As the performance of SIMO channel is closely related to the diversity combining techniques, we present closed-form expressions for the capacity of maximal ratio combining (MRC, equal gain combining (EGC, selection combining (SC, and switch and stay (SSC diversity systems operating in Nakagami-m fading channels. Also, the ergodic capacity of a SIMO system in a Nakagami-m fading channel without any diversity technique is derived. The latter scenario is further investigated for a large amount of receive antennas. Finally, numerical results are presented for illustration.

  13. Impact of channel estimation error on channel capacity of multiple input multiple output system

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In order to investigate the impact of channel estimation error on channel capacity of multiple input multiple output (MIMO) system, a novel method is proposed to explore the channel capacity in correlated Rayleigh fading environment. A system model is constructed based on the channel estimation error at receiver side. Using the properties of Wishart distribution, the lower bound of the channel capacity is derived when the MIMO channel is of full rank. Then a method is proposed to select the optimum set of transmit antennas based on the lower bound of the mean channel capacity. The novel method can be easily implemented with low computational complexity. The simulation results show that the channel capacity of MIMO system is sensitive to channel estimation error, and is maximized when the signal-to-noise ratio increases to a certain point. Proper selection of transmit antennas can increase the channel capacity of MIMO system by about 1 bit/s in a flat fading environment with deficient rank of channel matrix.

  14. Relationship Between Capacity and Pathloss for Indoor MIMO Channels

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ødum; Andersen, Jørgen Bach; Bauch, Gerhard

    2006-01-01

    MIMO transmission systems exploit scattering in the radio channel to achieve high capacity for a given SNR. A high pathloss is generally expected for channels with rich scattering, suggesting that a high SNR and rich multipath are competing goals. The current work investigates this issue based...

  15. On the classical capacity of quantum Gaussian channels

    Science.gov (United States)

    Lupo, Cosmo; Pirandola, Stefano; Aniello, Paolo; Mancini, Stefano

    2011-02-01

    The set of quantum Gaussian channels acting on one bosonic mode can be classified according to the action of the group of Gaussian unitaries. We look for bounds on the classical capacity for channels belonging to such a classification. Lower bounds can be efficiently calculated by restricting the study to Gaussian encodings, for which we provide analytical expressions.

  16. On the classical capacity of quantum Gaussian channels

    CERN Document Server

    Lupo, Cosmo; Aniello, Paolo; Mancini, Stefano

    2010-01-01

    The set of quantum Gaussian channels acting on one bosonic mode can be classified according to the action of the group of Gaussian unitaries. We look for bounds on the classical capacity for channels belonging to such a classification. Lower bounds can be efficiently calculated by restricting to Gaussian encodings, for which we provide analytical expressions.

  17. On the classical capacity of quantum Gaussian channels

    Energy Technology Data Exchange (ETDEWEB)

    Lupo, Cosmo; Mancini, Stefano [School of Science and Technology, University of Camerino, I-62032 Camerino (Italy); Pirandola, Stefano [Department of Computer Science, University of York, York YO10 5GH (United Kingdom); Aniello, Paolo, E-mail: cosmo.lupo@unicam.it, E-mail: pirs@cs.york.ac.uk, E-mail: paolo.aniello@na.infn.it, E-mail: stefano.mancini@unicam.it [Dipartimento di Scienze Fisiche dell' Universita di Napoli Federico II, Complesso Universitario di Monte Sant' Angelo, Via Cintia, I-80126 Napoli (Italy)

    2011-02-15

    The set of quantum Gaussian channels acting on one bosonic mode can be classified according to the action of the group of Gaussian unitaries. We look for bounds on the classical capacity for channels belonging to such a classification. Lower bounds can be efficiently calculated by restricting the study to Gaussian encodings, for which we provide analytical expressions.

  18. MIMO Channel Capacity for Handsets in Data Mode Operation

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ødum; Yanakiev, Boyan; Bonev, Ivan Bonev

    2010-01-01

    The current paper concerns realistic evaluation of the capacity of the MIMO channel between a BS and handheld device, such as a PDA or smart phone, held in front of the user’s body (data mode). The work is based on measurements of the MIMO channel between two widely separated BSs in a micro...

  19. MIMO Channel Capacity for Handsets in Data Mode Operation

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ødum; Yanakiev, Boyan; Bonev, Ivan Bonev

    2010-01-01

    The current paper concerns realistic evaluation of the capacity of the MIMO channel between a BS and handheld device, such as a PDA or smart phone, held in front of the user’s body (data mode). The work is based on measurements of the MIMO channel between two widely separated BSs in a micro-cellular...

  20. Capacity of the Degraded Half-Duplex Relay Channel

    CERN Document Server

    Vijayakumaran, Saravanan; Lok, Tat M

    2007-01-01

    A discrete memoryless half-duplex relay channel is constructed from a broadcast channel from the source to the relay and destination and a multiple access channel from the source and relay to the destination. When the relay listens, the channel operates in the broadcast mode. The channel switches to the multiple access mode when the relay transmits. If the broadcast component channel is physically degraded, the half-duplex relay channel will also be referred to as physically degraded. The capacity of this degraded half-duplex relay channel is examined. It is shown that the block Markov coding suggested in the seminal paper by Cover and El Gamal can be modified to achieve capacity for the degraded half-duplex relay channel. In the code construction, the listen-transmit schedule of the relay is made to depend on the message to be sent and hence the schedule carries information itself. If the schedule is restricted to be deterministic, it is shown that the capacity can be achieved by a simple management of infor...

  1. 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.

  2. Towards the Capacity Region of Multiplicative Linear Operator Broadcast Channels

    CERN Document Server

    Pang, Yimin

    2010-01-01

    Recent research indicates that packet multicasting employing random linear network coding can be regarded as transmitting subspaces as codewords over a linear operator channel (LOC). A LOC is normally viewed as a discrete memoryless unicast subspace channel over a finite field. In this paper we propose the framework of linear operator broadcast channels (LOBCs) and start initial work on determining their capacity region. LOBC correspond to a single-source multiple-recipients network, where every recipient's subchannel is a LOC having its own capacity. Our discussion concerns a class of constant-dimension multiplicative LOBCs (CMLOBCs), whose input subspaces have constant dimension and missing vectors of a subspace constitute the only possible channel interference. We first give a necessary and sufficient condition for a CMLOBC being stochastically degraded. Then we classify weakly and strongly degraded CMLOBCs. By numerically computing capacity regions with an Arimoto-Blahut type algorithm and discussing seve...

  3. Additive Classical Capacity of Quantum Channels Assisted by Noisy Entanglement

    Science.gov (United States)

    Zhuang, Quntao; Zhu, Elton Yechao; Shor, Peter W.

    2017-05-01

    We give a capacity formula for the classical information transmission over a noisy quantum channel, with separable encoding by the sender and limited resources provided by the receiver's preshared ancilla. Instead of a pure state, we consider the signal-ancilla pair in a mixed state, purified by a "witness." Thus, the signal-witness correlation limits the resource available from the signal-ancilla correlation. Our formula characterizes the utility of different forms of resources, including noisy or limited entanglement assistance, for classical communication. With separable encoding, the sender's signals across multiple channel uses are still allowed to be entangled, yet our capacity formula is additive. In particular, for generalized covariant channels, our capacity formula has a simple closed form. Moreover, our additive capacity formula upper bounds the general coherent attack's information gain in various two-way quantum key distribution protocols. For Gaussian protocols, the additivity of the formula indicates that the collective Gaussian attack is the most powerful.

  4. Low-SNR Capacity of MIMO Optical Intensity Channels

    KAUST Repository

    Chaaban, Anas

    2017-09-18

    The capacity of the multiple-input multiple-output (MIMO) optical intensity channel is studied, under both average and peak intensity constraints. We focus on low SNR, which can be modeled as the scenario where both constraints proportionally vanish, or where the peak constraint is held constant while the average constraint vanishes. A capacity upper bound is derived, and is shown to be tight at low SNR under both scenarios. The capacity achieving input distribution at low SNR is shown to be a maximally-correlated vector-binary input distribution. Consequently, the low-SNR capacity of the channel is characterized. As a byproduct, it is shown that for a channel with peak intensity constraints only, or with peak intensity constraints and individual (per aperture) average intensity constraints, a simple scheme composed of coded on-off keying, spatial repetition, and maximum-ratio combining is optimal at low SNR.

  5. Capacity Bounds and High-SNR Capacity of MIMO Intensity-Modulation Optical Channels

    KAUST Repository

    Chaaban, Anas

    2017-06-01

    The capacity of the intensity modulation direct detection multiple-input multiple-output channel is studied. Therein, the nonnegativity constraint of the transmit signal limits the applicability of classical schemes, including precoding. Thus, new ways are required for deriving capacity lower and upper bounds for this channel. To this end, capacity lower bounds are developed by deriving the achievable rates of two precoding-free schemes: Channel inversion and QR decomposition. The achievable rate of a DC-offset SVD-based scheme is also derived as a benchmark. Then, capacity upper bounds are derived and compared against the lower bounds. As a result, the capacity at high signal-to-noise ratio (SNR) is characterized for the case where the number of transmit apertures is not larger than the number of receive apertures, and is shown to be achievable by the QR decomposition scheme. This is shown for a channel with average intensity or peak intensity constraints. For a channel with both constraints, the high-SNR capacity is approximated within a small gap. Extensions to a channel with more transmit apertures than receive apertures are discussed, and capacity bounds for this case are derived.

  6. Secrecy Capacity of the Wiretap Channel with Noisy Feedback

    CERN Document Server

    Lai, Lifeng; Poor, H Vincent

    2007-01-01

    In this work, the role of noisy feedback in enhancing the secrecy capacity of the wiretap channel is investigated. A model is considered in which the feed-forward and feedback signals share the same noisy channel. More specifically, a discrete memoryless modulo-additive channel with a full-duplex destination node is considered first, and it is shown that a judicious use of feedback increases the perfect secrecy capacity to the capacity of the source-destination channel in the absence of the wiretapper. In the achievability scheme, the feedback signal corresponds to a private key, known only to the destination. Then a half-duplex system is considered, for which a novel feedback technique that always achieves a positive perfect secrecy rate (even when the source-wiretapper channel is less noisy than the source-destination channel) is proposed. These results hinge on the modulo-additive property of the channel, which is exploited by the destination to perform encryption over the channel without revealing its key...

  7. On the Channel Capacity of Multiantenna Systems with Nakagami Fading

    Directory of Open Access Journals (Sweden)

    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.

  8. Inequalities and separations among assisted capacities of quantum channels

    CERN Document Server

    Bennett, C H; Shor, P W; Smolin, J A; Bennett, Charles H.; Devetak, Igor; Shor, Peter W.; Smolin, John A.

    2004-01-01

    We exhibit discrete memoryless quantum channels whose quantum capacity assisted by two-way classical communication, $Q_2$, exceeds their unassisted one-shot Holevo capacity $C_H$. These channels may be thought of as having a data input and output, along with a control input that partly influences, and a control output that partly reveals, which of a set of unitary evolutions the data undergoes en route from input to output. The channel is designed so that the data's evolution can be exactly inferred by a classically coordinated processing of 1) the control output, and 2) a reference system entangled with the control input, but not from either of these resources alone. Thus a two-way classical side channel allows the otherwise noisy evolution of the data to be corrected, greatly increasing the capacity. The same family of channels provides examples where the classical capacity assisted by classical feedback, $C_B$, and the quantum capacity assisted by classical feedback $Q_B$, both exceed $C_H$. A related chan...

  9. On the capacity of Rician fading channels with full channel state information at low SNR

    KAUST Repository

    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.

  10. Power optimization for maximum channel capacity in MIMO relay system

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Introducing multiple-input multiple-output (MIMO) relay channel could offer significant capacity gain.And it is of great importance to develop effective power allocation strategies to achieve power efficiency and improve channel capacity in amplify-and-forward relay system.This article investigates a two-hop MIMO relay system with multiple antennas in relay node (RN) and receiver (RX).Maximizing capacity with antenna selection (MCAS) and maximizing capacity with eigen-decomposition (MCED) schemes are proposed to efficiently allocate power among antennas in RN under first and second hop limited scenarios.The analysis and simulation results show that both MCED and MCAS can improve the channel capacity compared with uniform power allocation (UPA) scheme in most of the studied areas.The MCAS bears comparison with MCED with an acceptable capacity loss, but lowers the complexity by saving channel state information (CSI) feedback to the transmitter (TX).Moreover, when the RN is close to RX, the performance of UPA is also close to the upper bound as the performance of first hop is limited.

  11. Ergodic Capacity of Cognitive Radio under Imperfect Channel State Information

    CERN Document Server

    Rezk, Zouheir

    2012-01-01

    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 outage constraint. When applied to Rayleigh fading channels, our results show, for instance, that the interference constraint is harmful at high-power regime in the sense that the capacity does not increase with the power, whereas at low-power regime, it has a marginal impact and no-interference performance corresponding to the ergodic capacity under average or peak transmit power constraint in absence of ...

  12. Capacity bounds for parallel IM-DD optical wireless channels

    KAUST Repository

    Chaaban, Anas

    2016-07-26

    A system consisting of parallel intensity-modulation direct-detection optical wireless channels with a total average intensity constraint is studied. Capacity upper and lower bounds for this system are derived. If channel-state information is available at the transmitter, the bounds have to be optimized with respect to intensity allocation over the parallel channels. The optimization of the lower bound is non-convex, however, the Karush-Kuhn-Tucker conditions can be used to find a list of possible solutions one of which is optimal. The optimal solution can then be found by an exhaustive search algorithm, which is computationally expensive. To overcome this, we propose a low-complexity intensity allocation algorithm which is nearly optimal. The optimized capacity lower bound coincides with the capacity at high signal-to-noise ratio. © 2016 IEEE.

  13. Capacities of lossy bosonic channel with correlated noise

    Energy Technology Data Exchange (ETDEWEB)

    Lupo, Cosmo; Pilyavets, Oleg V; Mancini, Stefano [Dipartimento di Fisica, Universita di Camerino, I-62032 Camerino (Italy)], E-mail: cosmo.lupo@unicam.it, E-mail: pilyavets@gmail.com, E-mail: stefano.mancini@unicam.it

    2009-06-15

    We evaluate the information capacities of a lossy bosonic channel with correlated noise. The model generalizes the one recently discussed by Pilyavets et al (2008 Phys. Rev. A 77 052324), where memory effects come from the interaction with correlated environments. Environmental correlations are quantified by a multimode squeezing parameter, which vanishes in the memoryless limit. We show that a global encoding/decoding scheme, which involves input-entangled states among different channel uses, is always preferable with respect to a local one in the presence of memory. Moreover, in a certain range of the parameters, we provide an analytical expression for the classical capacity of the channel showing that a global encoding/decoding scheme allows it to be attained. All the results can be applied to a broad class of bosonic Gaussian channels.

  14. Capacities of lossy bosonic channel with correlated noise

    Science.gov (United States)

    Lupo, Cosmo; Pilyavets, Oleg V.; Mancini, Stefano

    2009-06-01

    We evaluate the information capacities of a lossy bosonic channel with correlated noise. The model generalizes the one recently discussed by Pilyavets et al (2008 Phys. Rev. A 77 052324), where memory effects come from the interaction with correlated environments. Environmental correlations are quantified by a multimode squeezing parameter, which vanishes in the memoryless limit. We show that a global encoding/decoding scheme, which involves input-entangled states among different channel uses, is always preferable with respect to a local one in the presence of memory. Moreover, in a certain range of the parameters, we provide an analytical expression for the classical capacity of the channel showing that a global encoding/decoding scheme allows it to be attained. All the results can be applied to a broad class of bosonic Gaussian channels.

  15. 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

  16. Polaractivation for classical zero-error capacity of qudit channels

    Energy Technology Data Exchange (ETDEWEB)

    Gyongyosi, Laszlo, E-mail: gyongyosi@hit.bme.hu [Quantum Technologies Laboratory, Department of Telecommunications, Budapest University of Technology and Economics, 2 Magyar tudosok krt, Budapest, H-1117, Hungary and Information Systems Research Group, Mathematics and Natural Sciences, Hungarian Ac (Hungary); Imre, Sandor [Quantum Technologies Laboratory, Department of Telecommunications, Budapest University of Technology and Economics, 2 Magyar tudosok krt, Budapest, H-1117 (Hungary)

    2014-12-04

    We introduce a new phenomenon for zero-error transmission of classical information over quantum channels that initially were not able for zero-error classical communication. The effect is called polaractivation, and the result is similar to the superactivation effect. We use the Choi-Jamiolkowski isomorphism and the Schmidt-theorem to prove the polaractivation of classical zero-error capacity and define the polaractivator channel coding scheme.

  17. On the secrecy capacity of the wiretap channel with imperfect main channel estimation

    KAUST Repository

    Rezki, Zouheir

    2014-10-01

    We study the secrecy capacity of fast fading channels under imperfect main channel (between the transmitter and the legitimate receiver) estimation at the transmitter. Lower and upper bounds on the ergodic secrecy capacity are derived for a class of independent identically distributed (i.i.d.) fading channels. The achievable rate follows from a standard wiretap code in which a simple on-off power control is employed along with a Gaussian input. The upper bound is obtained using an appropriate correlation scheme of the main and eavesdropper channels and is the best known upper bound so far. The upper and lower bounds coincide with recently derived ones in case of perfect main CSI. Furthermore, the upper bound is tight in case of no main CSI, where the secrecy capacity is equal to zero. Asymptotic analysis at high and low signal-to-noise ratio (SNR) is also given. At high SNR, we show that the capacity is bounded by providing upper and lower bounds that depend on the channel estimation error. At low SNR, however, we prove that the secrecy capacity is asymptotically equal to the capacity of the main channel as if there were no secrecy constraint. Numerical results are provided for i.i.d. Rayleigh fading channels.

  18. MIMO channel capacity with full CSI at Low SNR

    KAUST Repository

    Tall, Abdoulaye

    2012-10-01

    In this paper, we characterize the ergodic capacity of Multiple Input Multiple Output (MIMO) Rayleigh fading channels with full channel state information (CSI) at both the transmitter (CSI-T) and the receiver (CSI-R) at asymptotically low signal-to-noise ratio (SNR). A simple analytical expression of the capacity is derived for any number of transmit and receive antennas. This characterization clearly shows the substantial gain in terms of capacity over the no CSI-T case and gives a good insight on the effect of the number of antennas used. In addition, an On-Off transmission scheme is proposed and is shown to be asymptotically capacity-achieving. © 2012 IEEE.

  19. CAPACITY EVALUATION OF MULTI-CHANNEL WIRELESS AD HOC NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Li Jiandong; Zygmunt J. Haas; Min Sheng

    2003-01-01

    In this paper, the capacity of multi-channel, multi-hop ad hoc network is evaluated.In particular, the performance of multi-hop ad hoc network with single channel IEEE 802.11MAC utilizing different topologies is shown. Also the scaling laws of throughputs for large-scale ad hoc networks and the theoretical guaranteed throughput bounds for multi-channel gridtopology systems are proposed. The results presented in this work will help researchers to choosethe proper parameter settings in evaluation of protocols for multi-hop ad hoc networks.

  20. The Subliminal Channel and Its Capacity in Proxy Signatures

    Institute of Scientific and Technical Information of China (English)

    DONGQingkuan; BAIEnjian; XIAOGuozhen

    2004-01-01

    A type of new broadband subliminal channel in proxy signatures is constructed. In proxy signatures the proxy signer signs a message on behalf of the original signer, so it is no sense that the original signer (the subliminal receiver in our construction) abuses the signing power.And the original signer can limit the signing power of the proxy signer, so our construction avoids the defect existing in the traditional broadband subliminal channel. Finally,other types of subliminal channels in proxy signature and their capacity are also briefly discussed.

  1. On the Capacity of Interference Channels with One Cooperating Transmitter

    CERN Document Server

    Maric, I; Krämer, G; Shamai, S

    2007-01-01

    Inner and outer bounds are established on the capacity region of two-sender, two-receiver interference channels where one transmitter knows both messages. The transmitter with extra knowledge is referred to as being cognitive. The inner bound is based on strategies that generalize prior work, and include rate-splitting, Gel'fand-Pinsker coding and cooperative transmission. A general outer bound is based on the Nair-El Gamal outer bound for broadcast channels. A simpler bound is presented for the case in which one of the decoders can decode both messages. The bounds are evaluated and compared for Gaussian channels.

  2. On Ergodic Secrecy Capacity for Gaussian MISO Wiretap Channels

    CERN Document Server

    Li, Jiangyuan

    2010-01-01

    A Gaussian multiple-input single-output (MISO) wiretap channel model is considered, where there exists a transmitter equipped with multiple antennas, a legitimate receiver and an eavesdropper each equipped with a single antenna. We study the problem of finding the optimal input covariance that achieves ergodic secrecy capacity subject to a power constraint where only statistical information about the eavesdropper channel is available at the transmitter. This is a non-convex optimization problem that is in general difficult to solve. Existing results address the case in which the eavesdropper or/and legitimate channels have independent and identically distributed Gaussian entries with zero-mean and unit-variance, i.e., the channels have trivial covariances. This paper addresses the general case where eavesdropper and legitimate channels have nontrivial covariances. A set of equations describing the optimal input covariance matrix are proposed along with an algorithm to obtain the solution. Based on this framew...

  3. On the capacity of multiaccess fading channels with full channel state information at low power regime

    KAUST Repository

    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.

  4. Wideband MIMO Channel Capacity Analysis in Multiprobe Anechoic Chamber Setups

    DEFF Research Database (Denmark)

    Fan, Wei; Kyosti, Pekka; Nielsen, Jesper Ødum

    2016-01-01

    This paper discusses over the air (OTA) testing for multiple input multiple output (MIMO) capable terminals with emphasis on wideband MIMO channel capacity analysis in a multi-probe anechoic chamber setup. In the literature, the spatial correlation simulation accuracy at the receiver (Rx) side ha...

  5. On the secrecy capacity of the MISO wiretap channel under imperfect channel estimation

    KAUST Repository

    Rezki, Zouheir

    2014-12-01

    We consider a wiretap channel consisting of a source with multiple antennas, a legitimate receiver and an eavesdropper with a single antenna each. The channels between the source and the receivers undergo fast fading. We assume that the transmitter, in addition to the statistics of both channels, is only aware of a noisy version of the CSI to the legitimate receiver referred to as main channel. The legitimate receiver is aware of both its instantaneous channel gain and the transmitter\\'s estimate of the main channel. On the other hand, the eavesdropper\\'s receiver, in addition to its instantaneous channel realization, is aware of the actual main CSI and the transmitter\\'s estimate as well. While the capacity of this channel is still open even with perfect CSI at the transmitter, we provide in this paper upper and lower bounds on the secrecy capacity. The upper bound is tighter than the one corresponding to perfect main CSI and the gap between the two upper bounds is characterized in function of the channel estimation error variance, at high-SNR. Furthermore, we show that our upper and lower bounds coincide in the case of no main CSI providing a trivial secrecy capacity.

  6. Capacity of a Nonlinear Optical Channel with Finite Memory

    CERN Document Server

    Agrell, Erik; Durisi, Giuseppe; Karlsson, Magnus

    2014-01-01

    The channel capacity of a nonlinear, dispersive fiber-optic link is revisited. To this end, the popular Gaussian noise (GN) model is extended with a parameter to account for the finite memory of realistic fiber channels. This finite-memory model is harder to analyze mathematically but, in contrast to previous models, it is valid also for nonstationary or heavy-tailed input signals. For uncoded transmission and standard modulation formats, the new model gives the same results as the regular GN model when the memory of the channel is about 10 symbols or more. These results confirm previous results that the GN model is accurate for uncoded transmission. However, when coding is considered, the results obtained using the finite-memory model are very different from those obtained by previous models, even when the channel memory is large. In particular, the peaky behavior of the channel capacity, which has been reported for numerous nonlinear channel models, appears to be an artifact of applying models derived for i...

  7. On the ergodic secrecy capacity of the wiretap channel under imperfect main channel estimation

    KAUST Repository

    Rezki, Zouheir

    2011-11-01

    The ergodic secrecy capacity of the wiretap channel is known when the main channel (between the transmitter and the legitimate receiver) state information (CSI) is perfect at the transmitter and the coherence period is sufficiently large to enable random coding arguments in each block. In a fast fading scenario, when the codeword length spans many coherence periods, the secrecy capacity is still not known. In this paper, we present a framework that characterizes this secrecy capacity under imperfect main channel estimation at the transmitter. Inner and outer bounds on the ergodic secrecy capacity are derived for a class of independent identically distributed (i.i.d.) fading channels. The achievable rate is a simple on-off scheme using a Gaussian input. The upper bound is obtained using an appropriate correlation scheme of the main and the eavesdropper channels. The upper and the lower bounds coincide with recently derived ones in the perfect main CSI extreme. Furthermore, the lower bound matches the upper bound in no main CSI extreme, where the secrecy capacity is equal to zero. Numerical results are provided for independent identically distributed (i.i.d.) Rayleigh fading channels. © 2011 IEEE.

  8. On the low SNR capacity of MIMO fading channels with imperfect channel state information

    KAUST Repository

    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.

  9. On the low SNR capacity of MIMO fading channels with imperfect channel state information

    KAUST Repository

    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.

  10. Secrecy Capacity Analysis over α−μ Fading Channels

    KAUST Repository

    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.

  11. Zero-Error Capacity of a Class of Timing Channels

    DEFF Research Database (Denmark)

    Kovacevic, M.; Popovski, Petar

    2014-01-01

    We analyze the problem of zero-error communication through timing channels that can be interpreted as discrete-time queues with bounded waiting times. The channel model includes the following assumptions: 1) time is slotted; 2) at most N particles are sent in each time slot; 3) every particle is ...... constructed, and a linear-time decoding algorithm for these codes devised. In the particular case N = 1, K = 1, the capacity is equal to φ, where φ = (1 + √5)/2 is the golden ratio, and constructed codes give another interpretation of the Fibonacci sequence....

  12. Achieving near-Capacity on Large Discrete Memoryless Channels

    CERN Document Server

    Mezghani, Amine; Nossek, Josef A

    2010-01-01

    We propose a method to increase the capacity achieved by uniform prior in discrete memoryless channels (DMC) with high input cardinality. It consists in appropriately reducing the input set. Different design criteria of the input subset are discussed. We develop an efficient algorithm to solve this problem based on the maximization of the cut-off rate. The method is applied to a mono-bit transceiver MIMO system, and it is shown that the capacity can be approached within tenths of a dB by employing standard binary codes while avoiding the use of distribution shapers.

  13. Channel Capacity Bounds in the Presence of Quantized Channel State Information

    Directory of Open Access Journals (Sweden)

    Makki Behrooz

    2010-01-01

    Full Text Available The goal of this paper is to investigate the effect of channel side information on increasing the achievable rates of continuous power-limited non-Gaussian channels. We focus on the case where (1 there is imperfect channel quality information available to the transmitter and the receiver and (2 while the channel gain is continuously varying, there are few cross-region changes, and the noise characteristics remain in each detection region for a long time. The results are presented for two scenarios, namely, reliable and unreliable region detection. Considering short- and long-term power constraints, the capacity bounds are found for log-normal and two different Nakagami-based channel distributions, and for both Max-Lloyd and equal probability quantization approaches. Then, the optimal gain partitioning approach, maximizing the achievable rates, is determined. Finally, general equations for the channel capacity bounds and optimal channel partitioning in the case of unreliable region detection are presented. Interestingly, the results show that, for high SNR's, it is possible to determine a power-independent optimal gain partitioning approach maximizing the capacity lower bound which, in both scenarios, is identical for both short- and long-term power constraints.

  14. RFID Ownership Transfer with Positive Secrecy Capacity Channels

    Directory of Open Access Journals (Sweden)

    Jorge Munilla

    2016-12-01

    Full Text Available RFID ownership transfer protocols (OTPs transfer tag ownership rights. Recently, there has been considerable interest in such protocols; however, guaranteeing privacy for symmetric-key settings without trusted third parties (TTPs is a challenge still unresolved. In this paper, we address this issue and show that it can be solved by using channels with positive secrecy capacity. We implement these channels with noisy tags and provide practical values, thus proving that perfect secrecy is theoretically possible. We then define a communication model that captures spatiotemporal events and describe a first example of symmetric-key based OTP that: (i is formally secure in the proposed communication model and (ii achieves privacy with a noisy tag wiretap channel without TTPs.

  15. Delays and the Capacity of Continuous-time Channels

    CERN Document Server

    Khanna, Sanjeev

    2011-01-01

    Any physical channel of communication offers two potential reasons why its capacity (the number of bits it can transmit in a unit of time) might be unbounded: (1) Infinitely many choices of signal strength at any given instant of time, and (2) Infinitely many instances of time at which signals may be sent. However channel noise cancels out the potential unboundedness of the first aspect, leaving typical channels with only a finite capacity per instant of time. The latter source of infinity seems less studied. A potential source of unreliability that might restrict the capacity also from the second aspect is delay: Signals transmitted by the sender at a given point of time may not be received with a predictable delay at the receiving end. Here we examine this source of uncertainty by considering a simple discrete model of delay errors. In our model the communicating parties get to subdivide time as microscopically finely as they wish, but still have to cope with communication delays that are macroscopic and va...

  16. On the Capacity of the Noncausal Relay Channel

    CERN Document Server

    Wang, Lele

    2011-01-01

    This paper studies the noncausal relay channel, also known as the relay channel with unlimited lookahead, introduced by El Gamal, Hassanpour, and Mammen. Unlike the standard relay channel model, where the relay encodes its signal based on the previous received output symbols, the relay in the noncausal relay channel encodes its signal as a function of the entire received sequence. In the existing coding schemes, the relay uses this noncausal information solely to recover the transmitted message and then cooperates with the sender to communicate this message to the receiver. However, it is shown in this paper that by applying the Gelfand--Pinsker coding scheme, the relay can take further advantage of the noncausally available information, which can achieve strictly higher rates than existing coding schemes. This paper also provides a new upper bound on the capacity of the noncausal relay that strictly improves upon the cutset bound. These new lower and upper bounds on the capacity coincide for the class of deg...

  17. On environment-assisted capacities of quantum channels

    CERN Document Server

    Winter, A

    2005-01-01

    Following initial work by Gregoratti and Werner [J. Mod. Optics 50, 913-933, 2003 and quant-ph/0403092] and Hayden and King [quant-ph/0409026], we study the problem of the capacity of a quantum channel assisted by a "friendly (channel) environment" that can locally measure and communicate classical messages to the receiver. Previous work [quant-ph/0505038] has yielded a capacity formula for the quantum capacity under this kind of help from the environment. Here we study the problem of the environment-assisted classical capacity, which exhibits a somewhat richer structure (at least, it seems to be the harder problem). There are several, presumably inequivalent, models of the permitted local operations and classical communications between receiver and environment: one-way, arbitrary, separable and PPT POVMs. In all these models, the task of decoding a message amounts to discriminating a set of possibly entangled states between the two receivers, by a class of operations under some sort of locality constraint. A...

  18. A new simple model for composite fading channels: Second order statistics and channel capacity

    KAUST Repository

    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.

  19. Full Spectrum Analytical Channel Design with the Capacity/Supply Ratio (CSR)

    National Research Council Canada - National Science Library

    Travis R Stroth; Brian P Bledsoe; Peter A Nelson

    2017-01-01

    .... The Capacity/Supply Ratio (CSR) approach-an extension of the Copeland method of analytical channel design for sand channels-balances the sediment transport capacity of a design reach with the sediment supply of a stable upstream...

  20. Achieving the Secrecy Capacity of Wiretap Channels Using Polar Codes

    CERN Document Server

    Mahdavifar, Hessam

    2010-01-01

    Suppose Alice wishes to send messages to Bob through a communication channel C_1, but her transmissions also reach an eavesdropper Eve through another channel C_2. The goal is to design a coding scheme that makes it possible for Alice to communicate both reliably and securely. Reliability is measured in terms of Bob's probability of error in recovering the message, while security is measured in terms of the mutual information between the message and Eve's observations. Wyner showed that the situation is characterized by a single constant C_s, called the secrecy capacity, which has the following meaning: for all $\\epsilon > 0$, there exist coding schemes of rate $R \\ge C_s - \\epsilon$ that asymptotically achieve both the reliability and the security objectives. However, his proof of this result is based upon a nonconstructive random-coding argument. To date, despite a considerable research effort, the only case where we know how to construct coding schemes that achieve secrecy capacity is when Eve's channel C_...

  1. Study and Analysis Capacity of MIMO Systems for AWGN Channel Model Scenarios

    Directory of Open Access Journals (Sweden)

    Hussain Bohra

    2014-10-01

    Full Text Available Future wireless communication systems can utilize the spatial properties of the wireless channel to enhance the spectral efficiency and therefore increases its channel capacity. This can be designed by deploying multiple antennas at both the transmitter side and receiver side. The basic measure of performance is the capacity of a channel; the maximum rate of communication for which arbitrarily small error probability can be achieved. The AWGN (additive white Gaussian noise channel introduces the notion of capacity through a heuristic argument. The AWGN channel is then used as a basic building block to check the capacity of wireless fading channels in contrast to the AWGN channel. There is no single definition of capacity for fading channels that is applicable in all situations. Several notions of capacity are developed, and together they form a systematic study of performance limits of fading channels. The various capacity measures allow us to observe clearly the various types of resources available in fading channels: degrees of freedom, power and diversity. The MIMO systems capacity can be enhanced linearly with large the number of antennas. This paper elaborates the study of MIMO system capacity using the AWGN Channel Model, Channel Capacity, Channel Fast Fading, Spatial Autocorrelation and Power delay profile for various channel environments.

  2. On the secrecy capacity of the broadcast wiretap channel with imperfect channel state information

    KAUST Repository

    Hyadi, Amal

    2014-12-01

    In this paper, we consider secure broadcasting over fast fading channels. Assuming imperfect main channel state information (CSI) at the transmitter, we first provide an upper and a lower bounds on the ergodic secrecy capacity when a common message is broadcasted to multiple legitimate receivers in the presence of one eavesdropper. For this case, we show that the secrecy rate is limited by the legitimate receiver having, on average, the worst main channel link. Then, we present an expression for the achievable secrecy sum-rate when each legitimate receiver is interested in an independent message. The special cases of high SNR, perfect and no-main CSI are also analyzed. Numerical results are presented to illustrate the obtained results for the case of independent but not necessarily identically distributed Rayleigh fading channels.

  3. Capacity of 1-to-K Broadcast Packet Erasure Channels with Channel Output Feedback (Full Version)

    CERN Document Server

    Wang, Chih-Chun

    2010-01-01

    This paper focuses on the 1-to-K broadcast packet erasure channel (PEC), which is a generalization of the broadcast binary erasure channel from the binary symbol to that of arbitrary finite fields GF(q) with sufficiently large q. We consider the setting in which the source node has instant feedback of the channel outputs of the K receivers after each transmission. The capacity region of the 1-to-K PEC with COF was previously known only for the case K=2. Such a setting directly models network coded packet transmission in the downlink direction with integrated feedback mechanisms (such as Automatic Repeat reQuest (ARQ)). The main results of this paper are: (i) The capacity region for general 1-to-3 broadcast PECs, and (ii) The capacity region for two types of 1-to-$K$ broadcast PECs: the symmetric PECs, and the spatially independent PECs with one-sided fairness constraints. This paper also develops (iii) A pair of outer and inner bounds of the capacity region for arbitrary 1-to-K broadcast PECs, which can be ea...

  4. Capacity of orthogonal space-time block codes in MISO fading channels with co-channel interference and noise

    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.

  5. Channel capacity and digital modulation schemes in correlated Weibull fading channels with nonidentical statistics

    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.

  6. MIMO Intensity-Modulation Channels: Capacity Bounds and High SNR Characterization

    KAUST Repository

    Chaaban, Anas

    2016-10-01

    The capacity of MIMO intensity modulation channels is studied. The nonnegativity of the transmit signal (intensity) poses a challenge on the precoding of the transmit signal, which limits the applicability of classical schemes in this type of channels. To resolve this issue, capacity lower bounds are developed by using precoding-free schemes. This is achieved by channel inversion or QR decomposition to convert the MIMO channel to a set of parallel channels. The achievable rate of a DC-offset SVD based scheme is also derived as a benchmark. Then, a capacity upper bound is derived and is shown to coincide with the achievable rate of the QR decomposition based scheme at high SNR, consequently characterizing the high-SNR capacity of the channel. The high-SNR gap between capacity and the achievable rates of the channel inversion and the DC-offset SVD based schemes is also characterized. Finally, the ergodic capacity of the channel is also briefly discussed.

  7. Conditions for equality between entanglement-assisted and unassisted classical capacities of a quantum channel

    CERN Document Server

    Shirokov, M E

    2011-01-01

    Both necessary and sufficient conditions of coincidence of the entanglement-assisted capacity with the Holevo capacity of a quantum channel are obtained. By using these conditions the equality between these capacities as well as the strict inequality between them are proved for several classes of quantum channel. In particular, it is shown that coincidence of the entanglement-assisted capacity with the Holevo capacity of a quantum channel implies that the $\\chi$-essential part of this channel is entanglement-breaking (the $\\chi$-essential part is defined as a restriction of a channel obtained by discarding all states useless for transmission of classical information). The above conditions and their corollaries are extended to quantum channels with linear constraints. By using these conditions it is shown that the question of coincidence of the entanglement-assisted capacity with the Holevo capacity of a constrained channel depends on the form of the constraint.

  8. Bounds on the capacity region of a class of compound interference channels

    CERN Document Server

    Raja, Adnan; Viswanath, Pramod

    2008-01-01

    We derive inner and outer bounds on the capacity region of a class of compound interference channels and quantify the gap between these bounds. From this we derive the capacity region of the compound version of El Gamal and Costa's deterministic interference channel, and characterize to within 2 bits the capacity region of scalar compound Gaussian interference channels. One of our main contributions is a novel achievable scheme for compound interference channels.

  9. Optimal Power Allocation for Fading Channels in Cognitive Radio Networks: Ergodic Capacity and Outage Capacity

    CERN Document Server

    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 ...

  10. Entanglement-Assisted Classical Capacity of a Generalized Amplitude Damping Channel

    Institute of Scientific and Technical Information of China (English)

    HOU Li-Zhen; FANG Mao-Fa

    2007-01-01

    The entanglement-assisted capacity of a generalized amplitude damping channel is investigated by using the properties of partial symmetry and concavity of mutual information. The numerical and analytical results of the entanglement-assisted capacity are obtained under certain conditions. It is shown that the entanglement-assisted capacity depends on the channel parameters representing the ambient temperature and dissipation, and the prior entanglement between sender and receiver can approximately double the classical capacity of the generalized amplitude damping channel.

  11. On the capacity of cognitive radio under limited channel state information over fading channels

    KAUST Repository

    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.

  12. Capacity of 1-to-K Broadcast Packet Erasure Channels with Channel Output Feedback

    CERN Document Server

    Wang, Chih-Chun

    2010-01-01

    This paper focuses on the 1-to-K broadcast packet erasure channel (PEC), which is a generalization of the broadcast binary erasure channel from the binary symbol to that of arbitrary finite fields GF(q) with sufficiently large q. We consider the setting in which the source node has instant feedback of the channel outputs of the K receivers after each transmission. Such a setting directly models network coded packet transmission in the downlink direction with integrated feedback mechanisms (such as Automatic Repeat reQuest (ARQ)). The main results of this paper are: (i) The capacity region for general 1-to-3 broadcast PECs, and (ii) The capacity region for two classes of 1-to-K broadcast PECs: the symmetric PECs, and the spatially independent PECs with one-sided fairness constraints. This paper also develops (iii) A pair of outer and inner bounds of the capacity region for arbitrary 1-to-K broadcast PECs, which can be evaluated by any linear programming solver. For most practical scenarios, the outer and inner...

  13. Information Theoretic Exemplification of the Impact of Transmitter-Receiver Cognition on the Channel Capacity

    CERN Document Server

    Anzabi-Nezhad, Nima S; Kakhki, Mohammad Molavi

    2011-01-01

    In this paper, we study, information theoretically, the impact of transmitter and or receiver cognition on the channel capacity. The cognition can be described by state information, dependent on the channel noise and or input. Specifically, as a new idea, we consider the receiver cognition as a state information dependent on the noise and we derive a capacity theorem based on the Gaussian version of the Cover-Chiang capacity theorem for two-sided state information channel. As intuitively expected, the receiver cognition increases the channel capacity and our theorem shows this increase quantitatively. Also, our capacity theorem includes the famous Costa theorem as its special cases.

  14. Channel Capacity of DWDM Networks with Cross-phase Modulation Effect

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In dense wavelength division multiplexing(DWDM) optical transmission systems, cross phase modulation(XPM) due to Kerr effect causes phase shift and intensity modulation in each channel, which will lead the channel capacity to be a random variable. An expression of the channel capacity dealing with XPM effect is presented, and the correctness and accuracy of this method are demonstrated by numerical simulation.

  15. Sounds like a winner: voice pitch influences perception of leadership capacity in both men and women.

    Science.gov (United States)

    Klofstad, Casey A; Anderson, Rindy C; Peters, Susan

    2012-07-01

    It is well known that non-human animals respond to information encoded in vocal signals, and the same can be said of humans. Specifically, human voice pitch affects how speakers are perceived. As such, does voice pitch affect how we perceive and select our leaders? To answer this question, we recorded men and women saying 'I urge you to vote for me this November'. Each recording was manipulated digitally to yield a higher- and lower-pitched version of the original. We then asked men and women to vote for either the lower- or higher-pitched version of each voice. Our results show that both men and women select male and female leaders with lower voices. These findings suggest that men and women with lower-pitched voices may be more successful in obtaining positions of leadership. This might also suggest that because women, on average, have higher-pitched voices than men, voice pitch could be a factor that contributes to fewer women holding leadership roles than men. Additionally, while people are free to choose their leaders, these results clearly demonstrate that these choices cannot be understood in isolation from biological influences.

  16. On the capacity of nakagami-m fading Channels with full channel state information at low SNR

    KAUST Repository

    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.

  17. On the Secrecy Capacity of MISO Visible Light Communication Channels

    KAUST Repository

    Arfaoui, Mohamed Amine

    2017-02-07

    We study the secrecy capacity of the multiple- input single-output (MISO) Gaussian wiretap visible light communication (VLC) channel. We study a typical VLC scenario with one transmitter, one legitimate receiver, and one eavesdropper. Specifically, we compute the achievable secrecy rate for various input signaling distributions, including the truncated generalized normal (TGN) and uniform distributions. The transmitter is equipped with multiple light sources, while the legitimate and unauthorized receivers are each equipped with a single photodetector. We analyze the achievable secrecy rates via transmit beamforming and artificial noise. In addition, both zero-forcing beamforming and robust beamforming are considered. In the former case, the location of the eavesdropper is assumed to be known, whereas in the latter case, the location of the eavesdropper is unknown. Our numerical results show that the secrecy rate achieved by the TGN distribution is significantly improved as compared to those achieved by the truncated Gaussian and uniform distributions, for both zero-forcing beamforming and robust beamforming. We also derive an upper bound on the achievable secrecy capacity that we used to assess the closeness of the achievable secrecy rates to the derived bound.

  18. Channel polarization: A method for constructing capacity-achieving codes for symmetric binary-input memoryless channels

    OpenAIRE

    Arikan, Erdal

    2008-01-01

    A method is proposed, called channel polarization, to construct code sequences that achieve the symmetric capacity $I(W)$ of any given binary-input discrete memoryless channel (B-DMC) $W$. The symmetric capacity is the highest rate achievable subject to using the input letters of the channel with equal probability. Channel polarization refers to the fact that it is possible to synthesize, out of $N$ independent copies of a given B-DMC $W$, a second set of $N$ binary-input channels $\\{W_N^{(i)...

  19. On the capacity of multiple access and broadcast fading channels with full channel state information at low SNR

    KAUST Repository

    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.

  20. The capacity of the cascaded fading channel in the low power regime

    KAUST Repository

    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.

  1. Average capacity for optical wireless communication systems over exponentiated Weibull distribution non-Kolmogorov turbulent channels.

    Science.gov (United States)

    Cheng, Mingjian; Zhang, Yixin; Gao, Jie; Wang, Fei; Zhao, Fengsheng

    2014-06-20

    We model the average channel capacity of optical wireless communication systems for cases of weak to strong turbulence channels, using the exponentiation Weibull distribution model. The joint effects of the beam wander and spread, pointing errors, atmospheric attenuation, and the spectral index of non-Kolmogorov turbulence on system performance are included. Our results show that the average capacity decreases steeply as the propagation length L changes from 0 to 200 m and decreases slowly down or tends to a stable value as the propagation length L is greater than 200 m. In the weak turbulence region, by increasing the detection aperture, we can improve the average channel capacity and the atmospheric visibility as an important issue affecting the average channel capacity. In the strong turbulence region, the increase of the radius of the detection aperture cannot reduce the effects of the atmospheric turbulence on the average channel capacity, and the effect of atmospheric visibility on the channel information capacity can be ignored. The effect of the spectral power exponent on the average channel capacity in the strong turbulence region is higher than weak turbulence region. Irrespective of the details determining the turbulent channel, we can say that pointing errors have a significant effect on the average channel capacity of optical wireless communication systems in turbulence channels.

  2. On the low SNR capacity of maximum ratio combining over rician fading channels with full channel state information

    KAUST Repository

    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.

  3. Low SNR capacity for MIMO Rician and Rayleigh-product fading channels with single co-channel interferer and noise

    KAUST Repository

    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.

  4. Channel capacity of multiple-input multiple-output systems with transmit and receive correlation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In order to investigate the impact of channel model parameters on the channel capacity of a multipleinput multiple-output (MIMO) system,a novel method is proposed to explore the channel capacity under Rayleigh flat fading with correlated transmit and receive antennas.The optimal transmitting direction which can achieve maximum channel capacity is derived using random matrices theory.In addition,the closed-form expression for the channel capacity of MIMO systems is given by utilizing the properties of Wishart distribution when SNR is high.Computer simulation results show that the channel capacity is maximized when the antenna spacing increases to a certain point,and furthermore,the larger the scattering angle is,the more quickly the channel capacity converges to its maximum.At high SNR (>12 dB),the estimation of capacity is close to its true value.And,when the same array configuration is adopted both at the transmitter and the receiver,the UCA yields higher channel capacity than ULA.

  5. Higher order capacity statistics of multi-hop transmission systems over Rayleigh fading channels

    KAUST Repository

    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.

  6. On the capacity of multiple access and broadcast fading Channels with full channel state information at low power regime

    KAUST Repository

    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.

  7. Polarized Uniform Linear Array System: Beam Radiation Pattern, Beamforming Diversity Order, and Channel Capacity

    Directory of Open Access Journals (Sweden)

    Xin Su

    2015-01-01

    Full Text Available There have been many studies regarding antenna polarization; however, there have been few publications on the analysis of the channel capacity for polarized antenna systems using the beamforming technique. According to Chung et al., the channel capacity is determined by the density of scatterers and the transmission power, which is obtained based on the assumption that scatterers are uniformly distributed on a 3D spherical scattering model. However, it contradicts the practical scenario, where scatterers may not be uniformly distributed under outdoor environment, and lacks the consideration of fading channel gain. In this study, we derive the channel capacity of polarized uniform linear array (PULA systems using the beamforming technique in a practical scattering environment. The results show that, for PULA systems, the channel capacity, which is boosted by beamforming diversity, can be determined using the channel gain, beam radiation pattern, and beamforming diversity order (BDO, where the BDO is dependent on the antenna characteristics and array configurations.

  8. On Feedback and the Classical Capacity of a Noisy Quantum Channel

    CERN Document Server

    Bowen, G; Nagarajan, Rajagopal

    2003-01-01

    In Shannon information theory the capacity of a memoryless communication channel cannot be increased by the use of feedback from receiver to sender. In this paper the use of classical feedback is shown to provide no increase in the unassisted classical capacity of a memoryless quantum channel when feedback is used across non-entangled input states, or when the channel is an entanglement--breaking channel. This gives a generalization of the Shannon theory for certain classes of feedback protocols when transmitting through noisy quantum communication channels.

  9. Capacity of Discrete-Time Wiener Phase Noise Channels to Within a Constant Gap

    OpenAIRE

    Barletta, Luca; Rini, Stefano

    2017-01-01

    The capacity of the discrete-time channel affected by both additive Gaussian noise and Wiener phase noise is studied. Novel inner and outer bounds are presented, which differ of at most $6.65$ bits per channel use for all channel parameters. The capacity of this model can be subdivided in three regimes: (i) for large values of the frequency noise variance, the channel behaves similarly to a channel with circularly uniform iid phase noise; (ii) when the frequency noise variance is small, the e...

  10. Capacity Limits and Multiplexing Gains of MIMO Channels with Transceiver Impairments

    OpenAIRE

    Björnson, Emil; Zetterberg, Per; Bengtsson, Mats; Ottersten, Björn

    2013-01-01

    International audience; The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas. This letter analyzes if this result holds when there are distortions from physical transceiver impairments. We prove analytically that such physical MIMO channels have a finite upper capacity limit, for any channel distribution and SNR. The high-SNR slope thus collapses to zero. This appears discouraging, but we prove the encouraging result t...

  11. On the Capacity of the Discrete Memoryless Broadcast Channel with Feedback

    CERN Document Server

    Shayevitz, Ofer

    2010-01-01

    A coding scheme for the discrete memoryless broadcast channel with {noiseless, noisy, generalized} feedback is proposed, and the associated achievable region derived. The scheme is based on a block-Markov strategy combining the Marton scheme and a lossy version of the Gray-Wyner scheme with side-information, where in each block the transmitter sends fresh data and update information that allows the receivers to improve the channel outputs observed in the previous block. The region is evaluated for two specific broadcast channels : A generalization of Dueck's channel, and a noisy version of Blackwell's channel. With noiseless feedback, the region is shown to exceed the corresponding no-feedback capacity region in both cases, and for the former channel also yields the noiseless-feedback capacity region. A simple continuity argument verifies an improvement over the no-feedback capacity region for both channels, in the limit of low feedback noise.

  12. Private classical capacity with a symmetric side channel and its application to quantum cryptography

    Science.gov (United States)

    Smith, Graeme

    2008-08-01

    We study the symmetric-side-channel-assisted private capacity of a quantum channel, for which we provide a single-letter formula. This capacity is additive, convex, and, for degradable channels, equal to the unassisted private capacity. While a channel’s (unassisted) capacity for private classical communication may be strictly larger than its quantum capacity, we will show that these capacities are equal for degradable channels, thus demonstrating the equivalence of privacy and quantum coherence in this context. We use these ideas to find new bounds on the key rate of quantum key distribution protocols with one-way classical post-processing. For the Bennett-Brassard 1984 protocol, our results demonstrate that collective attacks are strictly stronger than individual attacks.

  13. Ergodic Capacity Analysis in Cognitive Radio Systems under Channel Uncertainty

    CERN Document Server

    Akin, Sami

    2010-01-01

    In this paper, pilot-symbol-assisted transmission in cognitive radio systems over time selective flat fading channels is studied. It is assumed that causal and noncausal Wiener filter estimators are used at the secondary receiver with the aid of training symbols to obtain the channel side information (CSI) under an interference power constraint. Cognitive radio model is described together with detection and false alarm probabilities determined by using a Neyman-Person detector for channel sensing. Subsequently, for both filters, the variances of estimate errors are calculated from the Doppler power spectrum of the channel, and achievable rate expressions are provided considering the scenarios which are results of channel sensing. Numerical results are obtained in Gauss-Markov modeled channels, and achievable rates obtained by using causal and noncausal filters are compared and it is shown that the difference is decreasing with increasing signal-to-noise ratio (SNR). Moreover, the optimal probability of detect...

  14. A rigorous proof of MIMO channel capacity's increase with antenna number

    Institute of Scientific and Technical Information of China (English)

    GONG Jian-min; M.R. Soleymani; J.F.Hayes

    2008-01-01

    It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity, in the multiple-input multiple-output(MIMO) communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.

  15. A review on synchronous CDMA systems: optimum overloaded codes, channel capacity, and power control

    Directory of Open Access Journals (Sweden)

    Hosseini Seyed Amirhossein

    2011-01-01

    Full Text Available Abstract This paper is a tutorial review on important issues related to code-division multiple-access (CDMA systems such as channel capacity, power control, and optimum codes; specifically, we consider optimum overloaded codes that achieve errorless transmission in the absence of noise for the binary and nonbinary cases. A survey of lower and upper bounds for the sum channel capacity of such systems is given in the presence and absence of channel noise. The asymptotic results for the channel capacity are also investigated. The channel capacity, errorless transmission codes, and power estimation for near-far effects are also explored. The emphasis of this tutorial review is on the overloaded CDMA systems.

  16. Three-Way Channels With Multiple Unicast Sessions: Capacity Approximation via Network Transformation

    KAUST Repository

    Chaaban, Anas

    2016-09-28

    A network of three nodes mutually communicating with each other is studied. This multi-way network is a suitable model for three-user device-to-device communications. The main goal of this paper is to characterize the capacity region of the underlying Gaussian three-way channel (3WC) within a constant gap. To this end, a capacity outer bound is derived using cut-set bounds and genie-aided bounds. For achievability, the 3WC is first transformed into an equivalent star channel. This latter is then decomposed into a set of “successive” sub-channels, leading to a sub-channel allocation problem. Using backward decoding, interference neutralization, and known results on the capacity of the star-channel relying of physical-layer network coding, an achievable rate region for the 3WC is obtained. It is then shown that the achievable rate region is within a constant gap of the developed outer bound, leading to the desired capacity approximation. Interestingly, in contrast to the Gaussian two-way channel (TWC), adaptation is necessary in the 3WC. Furthermore, message splitting is another ingredient of the developed scheme for the 3WC, which is not required in the TWC. The two setups are, however, similar in terms of their sum-capacity pre-log, which is equal to 2. Finally, some interesting networks and their approximate capacities are recovered as special cases of the 3WC, such as the cooperative broadcast channel and multiple access channel.

  17. Approximating the Constellation Constrained Capacity of the MIMO Channel with Discrete Input

    DEFF Research Database (Denmark)

    Yankov, Metodi Plamenov; Forchhammer, Søren; Larsen, Knud J.;

    2015-01-01

    In this paper the capacity of a Multiple Input Multiple Output (MIMO) channel is considered, subject to average power constraint, for multi-dimensional discrete input, in the case when no channel state information is available at the transmitter. We prove that when the constellation size grows......, the QAM constrained capacity converges to Gaussian capacity, directly extending the AWGN result from [1]. Simulations show that for a given constellation size, a rate close to the Gaussian capacity can be achieved up to a certain SNR point, which can be found efficiently by optimizing the constellation...... for the equivalent orthogonal channel, obtained by the singular value decomposition. Furthermore, lower bounds on the constrained capacity are derived for the cases of square and tall MIMO matrix, by optimizing the constellation for the equivalent channel, obtained by QR decomposition....

  18. Primary Rate-Splitting Achieves Capacity for the Gaussian Cognitive Interference Channel

    CERN Document Server

    Rini, Stefano; Goldsmith, Andrea

    2012-01-01

    The cognitive interference channel models cognitive overlay radio systems, where cognitive radios overhear the transmission of neighboring nodes. Capacity for this channel is not known in general. For the Gaussian case capacity is known in three regimes, usually denoted as the "weak interference", "very strong interference" and "primary decodes cognitive". This paper provides a new capacity result, based on rate-splitting of the primary user's message into a public and private part and that generalizes the capacity results in the "very strong interference" and "primary decodes cognitive" regimes. This result indicates that capacity of the cognitive interference channel not only depends on channel conditions but also the level of cooperation with the primary user.

  19. Delay-limited capacity of fading multiple access and broadcast channels in the low power regime

    KAUST Repository

    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.

  20. On Ergodic Secrecy Capacity of Multiple Input Wiretap Channel with Statistical CSIT

    CERN Document Server

    Lin, Shih-Chun

    2012-01-01

    We consider the secure transmission in ergodic fast-Rayleigh fading multiple-input single-output single-antennaeavesdropper (MISOSE) wiretap channels. We assume that the statistics of both the legitimate and eavesdropper channels is the only available channel state information at the transmitter (CSIT). By introducing a new secrecy capacity upper bound, we prove that the secrecy capacity is achieved by Gaussian input without prefixing. To attain this, we form another MISOSE channel for upper-bounding, and tighten the bound by finding the worst correlations between the legitimate and eavesdropper channel coefficients. The resulting upper bound is tighter than the others in the literature which are based on modifying the correlation between the noises at the legitimate receiver and eavesdropper. Next, we fully characterize the ergodic secrecy capacity by showing that the optimal channel input covariance matrix is a scaled identity matrix, with the transmit power allocated uniformly among the antennas. The key t...

  1. On the Capacity of Compound State-Dependent Channels with States Known at the Transmitter

    CERN Document Server

    Piantanida, Pablo

    2010-01-01

    This paper investigates the capacity of compound state-dependent channels with non-causal state information available at only the transmitter. A new lower bound on the capacity of this class of channels is derived. This bound is shown to be tight for the special case of compound channels with stochastic degraded components, yielding the full characterization of the capacity. Specific results are derived for the compound Gaussian Dirty-Paper (GDP) channel. This model consists of an additive white Gaussian noise (AWGN) channel corrupted by an additive Gaussian interfering signal, known at the transmitter only, where the input and the state signals are affected by fading coefficients whose realizations are unknown at the transmitter. Our bounds are shown to be tight for specific cases. Applications of these results arise in a variety of wireless scenarios as multicast channels, cognitive radio and problems with interference cancellation.

  2. Capacity Theorems for Quantum Multiple Access Channels - Part I: Classical-Quantum and Quantum-Quantum Capacity Regions

    CERN Document Server

    Yard, J; Hayden, P; Yard, Jon; Devetak, Igor; Hayden, Patrick

    2005-01-01

    We consider quantum channels with two senders and one receiver. For an arbitrary such channel, we give multi-letter characterizations of two different two-dimensional capacity regions. The first region characterizes the rates at which it is possible for one sender to send classical information, while the other sends quantum information. The second region gives the rates at which each sender can send quantum information. We give an example of a channel with a single-letter classical-quantum region. We conclude with connections to other work and a conjecture on a generalization where each user simultaneously sends classical and quantum information.

  3. Effect of Decoherence Induced by a Spin Environment on Quantum Channel Capacity

    Institute of Scientific and Technical Information of China (English)

    MA Xiao-San; CHENG Mu-Tian; ZHAO Guang-Xing; WANG An-Min

    2012-01-01

    We investigate the effect of decoherence from a spin environment on the quantum channel capacity. Our results imply that the time evolution of the quantum channel capacity depends on the number of freedom degrees of the environment, the tunneling element, the initial state of the environment, and the system-environment coupling strength. From the analysis, we find that the strong tunneling elements and the weak coupling strength can enhance the quantum channel capacity while the environment with a large number of freedom degrees and the strong coupling strength will shrink it.

  4. Gaussian bosonic synergy: quantum communication via realistic channels of zero quantum capacity

    CERN Document Server

    Smith, Graeme; Yard, Jon

    2011-01-01

    As with classical information, error-correcting codes enable reliable transmission of quantum information through noisy or lossy channels. In contrast to the classical theory, imperfect quantum channels exhibit a strong kind of synergy: there exist pairs of discrete memoryless quantum channels, each of zero quantum capacity, which acquire positive quantum capacity when used together. Here we show that this "superactivation" phenomenon also occurs in the more realistic setting of optical channels with attenuation and Gaussian noise. This paves the way for its experimental realization and application in real-world communications systems.

  5. Approximating the constellation constrained capacity of the MIMO channel with discrete input

    DEFF Research Database (Denmark)

    Yankov, Metodi Plamenov; Forchhammer, Søren; Larsen, Knud J.

    2015-01-01

    In this paper the capacity of a Multiple Input Multiple Output (MIMO) channel is considered, subject to average power constraint, for multi-dimensional discrete input, in the case when no channel state information is available at the transmitter. We prove that when the constellation size grows, t...... for the equivalent orthogonal channel, obtained by the singular value decomposition. Furthermore, lower bounds on the constrained capacity are derived for the cases of square and tall MIMO matrix, by optimizing the constellation for the equivalent channel, obtained by QR decomposition....

  6. Secrecy Capacity of a Class of Broadcast Channels with an Eavesdropper

    CERN Document Server

    Ekrem, Ersen

    2008-01-01

    We study the security of communication between a single transmitter and multiple receivers in a broadcast channel in the presence of an eavesdropper. We consider several special classes of channels. As the first model, we consider the degraded multi-receiver wiretap channel where the legitimate receivers exhibit a degradedness order while the eavesdropper is more noisy with respect to all legitimate receivers. We establish the secrecy capacity region of this channel model. Secondly, we consider the parallel multi-receiver wiretap channel with a less noisiness order in each sub-channel, where this order is not necessarily the same for all sub-channels. We establish the common message secrecy capacity and sum secrecy capacity of this channel. Thirdly, we study a special class of degraded parallel multi-receiver wiretap channels and provide a stronger result. In particular, we study the case with two sub-channels two users and one eavesdropper, where there is a degradedness order in each sub-channel such that in...

  7. Gaussian Relay Channel Capacity to Within a Fixed Number of Bits

    CERN Document Server

    Chang, Woohyuk; Lee, Yong H

    2010-01-01

    In this paper, we show that the capacity of the three-node Gaussian relay channel can be achieved to within 1 and 2 bit/sec/Hz using compress-and-forward and amplify-and-forward relaying, respectively.

  8. On the secrecy capacity of the broadcast wiretap channel with limited CSI feedback

    KAUST Repository

    Hyadi, Amal

    2016-10-27

    In this paper, we investigate the problem of secure broadcasting over block-fading channels with limited channel knowledge at the transmitter. More particularly, we analyze the effect of having imperfect channel state information (CSI) via a finite rate feedback on the throughput of a broadcast channel where the transmission is intended for multiple legitimate receivers in the presence of an eavesdropper. First, we partially characterize the ergodic secrecy capacity of the system when the source broadcasts the same information to all the receivers, i.e., common message transmission. Then, we look at the independent messages case, where the transmitter broadcasts multiple independent messages to the legitimate receivers. For this case, we present lower and upper bounds on the ergodic secrecy sum-capacity. In both scenarios, we show that the proposed lower and upper bounds coincide asymptotically as the capacity of the feedback links becomes large, hence, fully characterizing the secrecy capacity in this case.

  9. Closed Form Secrecy Capacity of MIMO Wiretap Channels with Two Transmit Antennas

    CERN Document Server

    Li, Jiangyuan

    2011-01-01

    A Gaussian multiple-input multiple-output (MIMO) wiretap channel model is considered. The input is a two-antenna transmitter, while the outputs are the legitimate receiver and an eavesdropper, both equipped with multiple antennas. All channels are assumed to be known. The problem of obtaining the optimal input covariance matrix that achieves secrecy capacity subject to a power constraint is addressed, and a closed-form expression for the secrecy capacity is obtained.

  10. Digital Non-Linear Equalization for Flexible Capacity Ultradense WDM Channels for Metro Core Networking

    DEFF Research Database (Denmark)

    Arlunno, Valeria; Zhang, Xu; Larsen, Knud J.

    2011-01-01

    We experimentally demonstrate that digital non-linear equalization allows for using independent tunable DFB lasers spaced at 12.5 GHz for ultradense WDM PM-QPSK flexible capacity channels for metro core networking.......We experimentally demonstrate that digital non-linear equalization allows for using independent tunable DFB lasers spaced at 12.5 GHz for ultradense WDM PM-QPSK flexible capacity channels for metro core networking....

  11. On the Secrecy Capacity of the Multiple-Antenna Wiretap Channel with Limited CSI Feedback

    KAUST Repository

    Hyadi, Amal

    2015-12-01

    We study the ergodic secrecy capacity of a block fading wiretap channel when there are multiple antennas at the transmitter, the legitimate receiver and the eavesdropper. We consider that the receivers are aware of their respective channel matrices while the transmitter is only provided by a B-bits 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. Assuming an average transmit power constraint, we provide an upper and a 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; hence, fully characterizing the secrecy capacity in this case.

  12. Novel asymptotic results on the high-order statistics of the channel capacity over generalized fading channels

    KAUST Repository

    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.

  13. Eigenstructures of MIMO Fading Channel Correlation Matrices and Optimum Linear Precoding Designs for Maximum Ergodic Capacity

    Directory of Open Access Journals (Sweden)

    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.

  14. COMPUTATION OF MOMENTUM TRANSFER COEFFICIENT AND CONVEYANCE CAPACITY IN COMPOUND CHANNELS

    Institute of Scientific and Technical Information of China (English)

    WANG Hua; YANG Ke-jun; CAO Shu-you; LIU Xing-nian

    2007-01-01

    The momentum transfer coefficient is an important parameter for determining the apparent shear stress at the vertical interface between the main channel and its associated flood plains, the cross-sectional mean velocity and the discharge capacity in compound channels. In this article, under the Boussinesq assumption and through analyzing the characteristics of velocity distribution in the interacting region between the main channel and its associated flood plain, the expression of momentum transfer coefficient was theoretically derived. On the basis of force balance, the expression of vertical apparent shear stress was obtained. By applying the experimental data from the British Engineering Research Council Flood Channel Facility (SERC-FCF), the relationship between the momentum transfer coefficient with the relative depth and the ratio of the flood plain width to the main channel width, was established, And hence the conveyance capacity in compound channels was calculated with Liu and Dong's method. The computed results show that the momentum transfer coefficient relationship obtained is viable.

  15. Effective Capacity Analysis of Cognitive Radio Channels for Quality of Service Provisioning

    CERN Document Server

    Akin, Sami

    2009-01-01

    In this paper, cognitive transmission under quality of service (QoS) constraints is studied. In the cognitive radio channel model, it is assumed that the secondary transmitter sends the data at two different average power levels, depending on the activity of the primary users, which is determined by channel sensing performed by the secondary users. A state-transition model is constructed for this cognitive transmission channel. Statistical limitations on the buffer lengths are imposed to take into account the QoS constraints. The maximum throughput under these statistical QoS constraints is identified by finding the effective capacity of the cognitive radio channel. This analysis is conducted for fixed-power/fixed-rate, fixed-power/variable-rate, and variable-power/variable-rate transmission schemes under different assumptions on the availability of channel side information (CSI) at the transmitter. The impact upon the effective capacity of several system parameters, including channel sensing duration, detect...

  16. On the ergodic secret message capacity of the wiretap channel with finite-rate feedback

    KAUST Repository

    Rezki, Zouheir

    2012-07-01

    We study the secret message capacity of an ergodic block fading wiretap channel with partial channel state information at the transmitter and perfect channel state information at the receivers. We consider that in addition to the statistics of the main and the eavesdropper channel state information (CSI), the sender is provided by the legitimate receiver with a q-bit feedback, at the beginning of each coherence block, through an error-free feedback channel, with capacity q bits. We establish upper and lower bounds on the secrecy capacity. We show that a positive secrecy rate is achievable even when the feedback is at the end of each coherence block and q = 1. We also show that the lower and the upper bounds coincide asymptotically as q → ∞. Finally, asymptotic analysis at high Signal-to-Noise Ratio (SNR) are presented where it is found that the capacity is bounded at high-SNR and present a simple suboptimal scalar quantizer that is capacity achieving, without the need of any numerical optimization, as q → ∞. When applied to Rayleigh fading channels, we show that, at high-SNR, a 4-bit feedback achieves 90% of the secrecy capacity when perfect main CSI is available at the transmitter. © 2012 IEEE.

  17. Asymptotic Ergodic Capacity Analysis of Composite Lognormal Shadowed Channels

    KAUST Repository

    Ansari, Imran Shafique

    2015-05-01

    Capacity analysis of composite lognormal (LN) shadowed links, such as Rician-LN, Gamma-LN, and Weibull-LN, is addressed in this work. More specifically, an exact closed-form expression for the moments of the end-to-end signal-to-noise ratio (SNR) of a single composite link transmission system is presented in terms of well- known elementary functions. Capitalizing on these new moments expressions, we present asymptotically tight lower bounds for the ergodic capacity at high SNR. All the presented results are verified via computer-based Monte-Carlo simulations. © 2015 IEEE.

  18. User Influence on MIMO Channel Capacity for Handsets in Data Mode Operation

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ødum; Yanakiev, Boyan Radkov; Bonev, Ivan Bonev;

    2012-01-01

    The current paper concerns realistic evaluation of the capacity of the MIMO channel between a BS and handheld device, such as a PDA or smartphone, held in front of the user’s body (data mode). The work is based on measurements of the MIMO channel between two widely separated BSs in a micro...

  19. On the Symmetric Feedback Capacity of the K-user Cyclic Z-Interference Channel

    CERN Document Server

    Tandon, Ravi; Poor, H Vincent

    2011-01-01

    The K-user cyclic Z-interference channel models a situation in which the kth transmitter causes interference only to the (k-1)th receiver in a cyclic manner, i.e., the first transmitter causes interference only to the Kth receiver. The impact of noiseless feedback on the capacity of this channel is studied by focusing on the Gaussian cyclic Z-interference channel. To this end, the symmetric feedback capacity of the linear shift deterministic cyclic Z-interference channel (LD-CZIC) is completely characterized for all interference regimes. Using insights from the linear deterministic channel model, the symmetric feedback capacity of the Gaussian cyclic Z-interference channel is characterized up to within a constant number of bits. As a byproduct of the constant gap result, the symmetric degrees of freedom with feedback for the Gaussian cyclic Z-interference channel are also characterized. These results highlight that the symmetric feedback capacities for both linear and Gaussian channel models are in general fu...

  20. Estimation of MIMO channel capacity from phase-noise impaired measurements

    DEFF Research Database (Denmark)

    Pedersen, Troels; Yin, Xuefeng; Fleury, Bernard Henri

    2008-01-01

    phase noise samples affecting measurement samples collected with real TDMMIMO channel sounders are correlated. In this contribution a capacity estimator that accounts for the phase noise correlation is proposed. The estimator is based on a linear minimum mean square error estimate of the MIMO channel...

  1. On Antenna Design Objectives and the Channel Capacity of MIMO Handsets

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ødum; Yanakiev, Boyan; Barrio, Samantha Caporal Del;

    2014-01-01

    The branch correlation coefficient (BCC), the branch power ratio (BPR), and the total mean power (TMP) are often used to characterize the mobile multiple-input multiple- output (MIMO) channel. This work investigates to which degree these parameters are useful for maximizing the channel capacity o...

  2. Reliability Capacity of Half-Duplex Channels with Strict Deadlines

    DEFF Research Database (Denmark)

    Costa, Rui; Roetter, Daniel Enrique Lucani; Vinhoza, Tiago

    2015-01-01

    A fundamental characterization of a half-duplex wireless system with packet losses under traffic with hard deadlines is instrumental to understanding and developing efficient, coding aware policies for real-time applications. We set forth the concept of reliability capacity with a limited number...

  3. Information channel capacity in the field theory estimation

    Energy Technology Data Exchange (ETDEWEB)

    Sładkowski, J., E-mail: jan.sladkowski@us.edu.pl [Department of Astrophysics and Cosmology, Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Syska, J., E-mail: jacek.syska@us.edu.pl [Department of Field Theory and Particle Physics, Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland)

    2012-12-03

    The construction of the information capacity for the vector position parameter in the Minkowskian space–time is presented. This lays the statistical foundations of the kinematical term of the Lagrangian of the physical action for many field theory models, derived by the extremal physical information method of Frieden and Soffer.

  4. Simultaneous classical-quantum capacities of quantum multiple access channels

    CERN Document Server

    Yard, J

    2005-01-01

    The rates at which classical and quantum information can be simultaneously transmitted from two spatially separated senders to a single receiver over an arbitrary quantum channel are characterized. Two main results are proved in detail. The first describes the region of rates at which one sender can send classical information while the other sends quantum information. The second describes those rates at which both senders can send quantum information. For each of these situations, an example of a channel is given for which the associated region admits a single-letter description. This is the author's Ph.D. dissertation, submitted to the Department of Electrical Engineering at Stanford University in March, 2005. It represents an expanded version of the paper quant-ph/0501045, containing a number of tutorial chapters which may be of independent interest for those learning about quantum Shannon theory.

  5. The Capacity of Finite-State Channels in the High-Noise Regime

    CERN Document Server

    Pfister, Henry D

    2010-01-01

    This paper considers the derivative of the entropy rate of a hidden Markov process with respect to the observation probabilities. The main result is a compact formula for the derivative that can be evaluated easily using Monte Carlo methods. It is applied to the problem of computing the capacity of a finite-state channel (FSC) and, in the high-noise regime, the formula has a simple closed-form expression that enables series expansion of the capacity of a FSC. This expansion is evaluated for a binary-symmetric channel under a (0,1) run-length limited constraint and an intersymbol-interference channel with Gaussian noise.

  6. A Monotonically Increasing Lower Bound on the Capacity of the Fiber-Optical Channel

    CERN Document Server

    Keykhosravi, Kamran; Durisi, Giuseppe

    2015-01-01

    An achievable rate is derived for the fiber-optical channel, described by the nonlinear Schr\\"odinger equation and discretized in time and space. The model takes into account the effects of nonlinearity, dispersion, and noise. The obtained achievable rate goes to infinity with a pre-log factor of one half as the power grows large. Since any achievable rate is a lower bound on the capacity of the same channel, the result proves that the capacity of the discretized fiber-optical channel grows unboundedly.

  7. MIMO channel capacity using antenna selection and water pouring

    OpenAIRE

    Cuan Cortes, Jose V.; Vargas-Rosales, Cesar; Munoz Rodriguez, David

    2014-01-01

    Abstract The use of multiple-input multiple-output (MIMO) communication systems has attracted considerable attention due to capacity and performance improvements without increasing the required bandwidth or transmission power. Although MIMO improves the transmission rate and provides reliable communication, these advantages come at a high cost, since multiple radio frequency (RF) chains have to be employed. Therefore, cost-effective implementation of MIMO systems remains as an important chall...

  8. Capacity bounds for kth best path selection over generalized fading channels

    KAUST Repository

    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.

  9. Low SNR Capacity of FSO Links over Gamma-Gamma Atmospheric Turbulence Channels

    KAUST Repository

    Benkhelifa, Fatma

    2013-01-27

    In this paper, we study the ergodic capacity of free space optical communication systems over Gamma-Gamma atmospheric turbulence fading channels with perfect channel state information at both the transmitter and the receiver. In our framework, we mainly focus on the low signal-to-noise ratio range and show that the ergodic capacity scales proportionally to SNR log^4(1/SNR). We show also that one-bit CSI feedback at the transmitter is enough to achieve this capacity using an on-o ff power control scheme.

  10. Low SNR Capacity of FSO Links over Gamma-Gamma Atmospheric Turbulence Channels

    KAUST Repository

    Benkhelifa, Fatma

    2013-02-23

    In this paper, we study the ergodic capacity of free space optical communication systems over Gamma-Gamma atmospheric turbulence fading channels with perfect channel state information at both the transmitter and the receiver. In our framework, we mainly focus on the low signal-to-noise ratio range and show that the ergodic capacity scales proportionally to SNR log^4(1/SNR). We show also that one-bit CSI feedback at the transmitter is enough to achieve this capacity using an on-off power control scheme.

  11. A General Achievable Rate Region for Multiple-Access Relay Channels and Some Certain Capacity Theorems

    CERN Document Server

    Osmani-Bojd, Mohammad; Hodtani, Ghosheh Abed

    2011-01-01

    In this paper, we obtain a general achievable rate region and some certain capacity theorems for multiple-access relay channel (MARC), using decode and forward (DAF) strategy at the relay, superposition coding at the transmitters. Our general rate region (i) generalizes the achievability part of Slepian-Wolf multiple-access capacity theorem to the MARC, (ii) extends the Cover-El Gamal best achievable rate for the relay channel with DAF strategy to the MARC, (iii) gives the Kramer-Wijengaarden rate region for the MARC, (iv) meets max-flow min-cut upper bound and leads to the capacity regions of some important classes of the MARC.

  12. Capacity-Approaching Signal Constellations for the Additive Exponential Noise Channel

    CERN Document Server

    Goff, Stéphane Y Le

    2011-01-01

    We present a new family of signal constellations, called log constellations, that can be used to design near-capacity coded modulation schemes over additive exponential noise (AEN) channels. Log constellations are designed by geometrically approximating the input distribution that maximizes the AEN channel capacity. The mutual information achievable over AEN channels with both coded modulation (CM) and bit-interleaved coded modulation (BICM) approaches is evaluated for various signal sets. In the case of CM, the proposed log constellations outperform, sometimes by over half a decibel, the best existing signal sets available from the literature, and can display error performance within only 0.12 dB of the AEN channel capacity. In the context of BICM, log constellations do not offer significant performance advantages over the best existing constellations. As the potential performance degradation resulting from the use of BICM instead of CM is larger than 1 dB, BICM may however not be a suitable design approach ...

  13. Fading Characteristics and Capacity of Deterministic Downlink MIMO Fading Channel with Non-Isotropic Scattering

    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.

  14. The Approximate Sum Capacity of the Symmetric Gaussian K-User Interference Channel

    CERN Document Server

    Ordentlich, Or; Nazer, Bobak

    2012-01-01

    Interference alignment has emerged as a powerful tool in the analysis of multi-user networks. Despite considerable recent progress, the capacity region of the Gaussian K-user interference channel is still unknown in general, in part due to the challenges associated with alignment on the signal scale using lattice codes. This paper develops a new framework for lattice interference alignment, based on the compute-and-forward approach. Within this framework, each receiver decodes by first recovering two or more linear combinations of the transmitted codewords with integer-valued coefficients and then solving these equations for its desired codeword. For the special case of symmetric channel gains, this framework is used to derive the approximate sum capacity of the Gaussian interference channel, up to an explicitly defined outage set of the channel gains. The key contributions are the capacity lower bounds for the weak through strong interference regimes, where each receiver should jointly decode its own codewor...

  15. Capacity Bounds and Exact Results for the Cognitive Z-interference Channel

    CERN Document Server

    Liu, Nan; Cheng, Yinghui; Goldsmith, Andrea J; Shamai, Shlomo

    2011-01-01

    We study the discrete memoryless Z-interference channel (ZIC) where the transmitter of the pair that suffers from interference is cognitive. We first provide an upper bound on the capacity of this channel. We then show that, when the channel of the transmitter-receiver pair that does not experience interference is deterministic, our proposed upper bound matches the known lower bound provided by Cao and Chen in 2008. The obtained results imply that, unlike in the Gaussian cognitive ZIC, in the considered channel superposition encoding at the non-cognitive transmitter as well as Gel'fand-Pinsker encoding at the cognitive transmitter are needed in order to minimize the impact of interference. As a byproduct of the obtained capacity region, we obtain the capacity under the generalized Gel'fand-Pinsker conditions where a transmitter-receiver pair communicates in the presence of interference noncausally known at the encoder.

  16. Fundamental Limits of Parallel Optical Wireless Channels: Capacity Results and Outage Formulation

    KAUST Repository

    Chaaban, Anas

    2016-10-26

    Multi-channel (MC) optical wireless communication (OWC) systems employing wave-division multiplexing for outdoors free-space optical communications, or multi-user timedivision multiple access for indoors visible-light communications, e.g., can be modeled as parallel channels. Multi-input multioutput OWC systems can also be transformed, possibly with some performance loss, to parallel channels using pre-/postcoding. Studying the performance of such MC-OWC systems requires characterizing the capacity of the underlying parallel channels. In this paper, upper and lower bounds on the capacity of constant parallel OWC channels with a total average intensity constraint are derived. Then, the paper focuses on finding intensity allocations that maximize the lower bounds given channel-state information at the transmitter (CSIT). Due to its nonconvexity, the KKT conditions are used to describe a list of candidate allocations. Instead searching exhaustively for the best solution, low-complexity near-optimal algorithms are proposed. The resulting optimized lower bound nearly coincides with capacity at high signal-to-noise ratio (SNR). Under a quasi-static channel model and in the absence of CSIT, outage probability upper and lower bounds are derived. Those bounds also meet at high SNR, thus characterizing the outage capacity in this regime. Finally, the results are extended to a system with both average and peak intensity constraints.

  17. Ergodic secret message capacity of the wiretap channel with finite-rate feedback

    KAUST Repository

    Rezki, Zouheir

    2014-06-01

    We study the secret message capacity of an ergodic block fading wiretap channel with partial channel state information at the transmitter and perfect channel state information at the receivers, under both a short term power constraint (STPC) and a long term power constraint (LTPC). We consider that in addition to the statistics of the main and the eavesdropper channel state information (CSI), the sender is provided by the legitimate receiver with a q-bit feedback, at the beginning of each coherence block, through an error-free public channel, with capacity q bits. We establish upper and lower bounds on the secrecy capacity. We show that the lower and the upper bounds coincide asymptotically as q → ∞. When applied to Rayleigh fading channels, we show that, a 4-bit feedback achieves about 90% of the secrecy capacity when perfect main CSI is available at the transmitter. Finally, asymptotic analysis at high and low Signal-to-Noise Ratio (SNR) is presented. It is found that the capacity is bounded at high-SNR, whereas at asymptotically low-SNR, the lower bounds and the upper bound scale linearly with SNR under STPC. Furthermore, subject to LTPC, the capacity at low-SNR is equal to the capacity of the main channel without secrecy constraint and with perfect CSI at both the transmitter and the receiver, under a mild condition on the fading statistics. We also show that a positive secrecy rate is achievable even when the feedback is at the end of each coherence block and q=1. © 2002-2012 IEEE.

  18. The Deterministic Sum Capacity of a Multiple Access Channel Interfering with a Point to Point Link

    CERN Document Server

    Bühler, Jörg

    2011-01-01

    In this paper, we use the linear deterministic approximation model to study a two user multiple access channel mutually interfering with a point to point link, which represents a basic setup of a cellular system. We derive outer bounds on the achievable sum rate and construct coding schemes achieving the outer bounds. For a large parameter range, the sum capacity is identical to the sum capacity of the interference channel obtained by silencing the weaker user in the multiple access channel. For other interference configurations, the sum rate can be increased using interference alignment, which exploits the channel gain difference of the users in the multiple access channel. From these results, lower bounds on the generalized degrees of freedom for the Gaussian counterpart are derived.

  19. A deterministic equivalent for the capacity analysis of correlated multi-user MIMO channels

    CERN Document Server

    Couillet, Romain; Silverstein, Jack W

    2009-01-01

    This paper provides the analysis of capacity expressions in multi-user and multi-cell systems when the transmitters and receivers have a large number of correlated antennas. Our main contribution mathematically translates into a deterministic equivalent of the Shannon transform of a class of large dimensional random matrices. This class of large matrices is used in this contribution to model (i) multi-antenna multiple access (MAC) and broadcast channels (BC) with transmit and receive channel correlation, (ii) multiple-input multiple-output (MIMO) communications with inter-cell interference and channel correlation both at the base stations and at the receiver. These models extend the classical results on multi-user MIMO capacities in independent and identically distributed (i.i.d.) Gaussian channels to the more realistic Gaussian channels with separable variance profile. On an information theoretical viewpoint, this article provides: in scenario (i), an asymptotic description of the MAC and BC rate regions as ...

  20. MIMO capacity for deterministic channel models: sublinear growth

    DEFF Research Database (Denmark)

    Bentosela, Francois; Cornean, Horia; Marchetti, Nicola

    2013-01-01

    This is the second paper by the authors in a series concerned with the development of a deterministic model for the transfer matrix of a MIMO system. In our previous paper, we started from the Maxwell equations and described the generic structure of such a deterministic transfer matrix...... some generic assumptions, we prove that the capacity grows much more slowly than linearly with the number of antennas. These results reinforce previous heuristic results obtained from statistical models of the transfer matrix, which also predict a sublinear behavior....

  1. Reliability Capacity of Half-Duplex Channels with Strict Deadlines

    DEFF Research Database (Denmark)

    Costa, Rui; Roetter, Daniel Enrique Lucani; Vinhoza, Tiago;

    2015-01-01

    A fundamental characterization of a half-duplex wireless system with packet losses under traffic with hard deadlines is instrumental to understanding and developing efficient, coding aware policies for real-time applications. We set forth the concept of reliability capacity with a limited number...... and in terms of its advantages towards the mean number of packets that can be transmitted reliably. Optimal schemes for leveraging feedback are presented and the results show that a judicious use of even a single feedback packet can have a significant impact on the mean performance....

  2. On the Capacity Region and the Generalized Degrees of Freedom Region for the MIMO Interference Channel with Feedback

    OpenAIRE

    Ashraphijuo, Mehdi; Aggarwal, Vaneet; Wang, Xiaodong

    2012-01-01

    In this paper, we study the effect of feedback on two-user MIMO interference channels. The capacity region of MIMO interference channels with feedback is characterized within a constant number of bits, where this constant is independent of the channel matrices. Further, it is shown that the capacity region of a MIMO interference channel with feedback and its reciprocal interference channel are within a constant number of bits. Finally, the generalized degrees of freedom region for the MIMO in...

  3. Antenna Array Structures Effect on Water-Filling Capacity of Indoor NLOS MIMO Channel

    Institute of Scientific and Technical Information of China (English)

    L(U) Jian-gang; L(U) Ying-hua; DU Juan; LI Yun-zhuang; WANG Xu-ying

    2005-01-01

    A 2-D Shooting and Bouncing Ray-tracing method (SBR) is used to analyze the different antenna array structure effect on the water-filling Capacity Complementary Cumulative Distribution Functions (CCDFS) of indoor Non-Line-of-Sight (NLOS) Multiple-Input Multiple-Output (MIMO) channel. The results have shown that in NLOS indoor environment different antenna array structures affect on the CCDFS differently. The CCDFS of MIMO systems with antenna spacing 5λ change slightly with antenna array structures and all approach the in independent and identically distribution (i.i.d.) rayleigh channel water-filling capacity. When antenna spacing decreased to 0.5λ, the capacities of MIMO systems drop also, and change with antenna array structures greatly. The results on outage water-filling capacity also show that there exist a fixed relationship that i.i.d. rayleigh channel capacity is larger than the capacity equipped with linear antenna array which is larger than the capacity equipped with rectangular antenna array and the capacity equipped with circular antenna array.

  4. Maximizing Networking Capacity in Multi-Channel Multi-Radio Wireless Networks

    Institute of Scientific and Technical Information of China (English)

    万鹏俊; 万志国

    2014-01-01

    Providing each node with one or more multi-channel radios offers a promising avenue for enhancing the network capacity by simultaneously exploiting multiple non-overlapping channels through different radio interfaces and mitigating interferences through proper channel assignment. However, it is quite challenging to effectively utilize multiple channels and/or multiple radios to maximize throughput capacity. The National Natural Science Foundation of China (NSFC) Pro ject 61128005 conducted comprehensive algorithmic-theoretic and queuing-theoretic studies of maximizing wireless networking capacity in multi-channel multi-radio (MC-MR) wireless networks under the protocol interference model and fundamentally advanced the state of the art. In addition, under the notoriously hard physical interference model, this project has taken initial algorithmic studies on maximizing the network capacity, with or without power control. We expect the new techniques and tools developed in this project will have wide applications in capacity planning, resource allocation and sharing, and protocol design for wireless networks, and will serve as the basis for future algorithm developments in wireless networks with advanced features, such as multi-input multi-output (MIMO) wireless networks.

  5. Capacity of cognitive radio under imperfect secondary and cross link channel state information

    KAUST Repository

    Sboui, Lokman

    2011-09-01

    In this paper, we study the ergodic capacity of secondary user channel in a spectrum sharing scenario in which the secondary transmitter is instantaneously aware of estimated versions of the cross link (between the secondary transmitter and the primary receiver) and the secondary link Channel State Information (CSI). The secondary link optimal power profile along with the ergodic capacity are derived for a class of fading channels, under an average power constraint and an instantaneous interference outage constraint. We also show that our framework is rather general as it encompasses several previously studied spectrum sharing settings as special cases. In order to gain some insights on the capacity behavior, numerical results are shown for independent Rayleigh fading channels where it is found for instance, that at low SNR regime, only the secondary channel estimation matters and that the cross link CSI has no effect on the ergodic capacity; whereas at high SNR regime, the capacity is rather driven by the cross link CSI. © 2011 IEEE.

  6. On Achievable Network Capacity and Throughput-Achieving Policies over Markov ON/OFF Channels

    CERN Document Server

    Li, Chih-ping

    2010-01-01

    We study the fundamental network capacity of a single-hop wireless downlink under two assumptions: (1) channels are never explicitly probed and thus instantaneous states are never known; (2) channels are modeled as Markov ON/OFF chains. This is an important network model to explore because practically channel probing may be infeasible, and in this case we shall use channel memory to improve network throughput. Computing in closed-form the capacity region of this network is difficult because it involves solving partially observable Markov decision processes. Instead, in this paper we construct an inner and an outer bound on the capacity region. In case of symmetric channels, the proximity of the inner and the outer bound to the true capacity region is analyzed. We show that the two bounds are tight when the network serves a large number of users with balanced traffic. We also propose a simple queue-dependent policy that can stabilize the network with any data rates strictly within the inner capacity bound. Thi...

  7. On the Sum-Capacity with Successive Decoding in Interference Channels

    CERN Document Server

    Zhao, Yue; Avestimehr, A Salman; Diggavi, Suhas N; Pottie, Gregory J

    2011-01-01

    In this paper, we investigate the sum-capacity of the two-user Gaussian interference channel with Gaussian superposition coding and successive decoding. We first examine an approximate deterministic formulation of the problem, and introduce the complementarity conditions that capture the use of Gaussian coding and successive decoding. In the deterministic channel problem, we find the constrained sum-capacity and its achievable schemes with the minimum number of messages, first in symmetric channels, and then in general asymmetric channels. We show that the constrained sum-capacity oscillates as a function of the cross link gain parameters between the information theoretic sum-capacity and the sum-capacity with interference treated as noise. Furthermore, we show that if the number of messages of either of the two users is fewer than the minimum number required to achieve the constrained sum-capacity, the maximum achievable sum-rate drops to that with interference treated as noise. We provide two algorithms (a ...

  8. 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.

  9. Exact capacity analysis of multihop transmission over amplify-and-forward relay fading channels

    KAUST Repository

    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.

  10. On the BER and capacity analysis of MIMO MRC systems with channel estimation error

    KAUST Repository

    Yang, Liang

    2011-10-01

    In this paper, we investigate the effect of channel estimation error on the capacity and bit-error rate (BER) of a multiple-input multiple-output (MIMO) transmit maximal ratio transmission (MRT) and receive maximal ratio combining (MRC) systems over uncorrelated Rayleigh fading channels. We first derive the ergodic (average) capacity expressions for such systems when power adaptation is applied at the transmitter. The exact capacity expression for the uniform power allocation case is also presented. Furthermore, to investigate the diversity order of MIMO MRT-MRC scheme, we derive the BER performance under a uniform power allocation policy. We also present an asymptotic BER performance analysis for the MIMO MRT-MRC system with multiuser diversity. The numerical results are given to illustrate the sensitivity of the main performance to the channel estimation error and the tightness of the approximate cutoff value. © 2011 IEEE.

  11. Effective capacity of Nakagami-m fading channels with full channel state information in the low power regime

    KAUST Repository

    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.

  12. Channel capacity and receiver deployment optimization for multi-input multi-output visible light communications.

    Science.gov (United States)

    Wang, Jin-Yuan; Dai, Jianxin; Guan, Rui; Jia, Linqiong; Wang, Yongjin; Chen, Ming

    2016-06-13

    Multi-input multi-output (MIMO) technique is attractive for visible light communication (VLC), which exploits the high signal-to-noise ratio (SNR) of a single channel to overcome the capacity limitation due to the small modulation bandwidth of the light emitting diode. This paper establishes a MIMO VLC system under the non-negativity, peak power and dimmable average power constraints. Assume that perfect channel state information at the transmitter is known, the MIMO channel is changed to parallel, non-interfering sub-channels by using the singular value decomposition (SVD). Based on the SVD, the lower bound on the channel capacity for MIMO VLC is derived by employing entropy power inequality and variational method. Moreover, by maximizing the derived lower bound on the capacity under the given constraints, the receiver deployment optimization problem is formulated. The problem is solved by employing the principle of particle swarm optimization. Numerical results verify the derived capacity bound and the proposed deployment optimization scheme.

  13. An MGF-based capacity analysis of equal gain combining over fading channels

    KAUST Repository

    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.

  14. Capacity of Fading Gaussian Channel with an Energy Harvesting Sensor Node

    CERN Document Server

    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.

  15. On the computation of the higher-order statistics of the channel capacity over generalized fading channels

    KAUST Repository

    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.

  16. Capacity of spectrum sharing Cognitive Radio systems over Nakagami fading channels at low SNR

    KAUST Repository

    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.

  17. Determination of optimal lot size and production rate for multi-production channels with limited capacity

    Science.gov (United States)

    Huang, Yeu-Shiang; Wang, Ruei-Pei; Ho, Jyh-Wen

    2015-07-01

    Due to the constantly changing business environment, producers often have to deal with customers by adopting different procurement policies. That is, manufacturers confront not only predictable and regular orders, but also unpredictable and irregular orders. In this study, from the perspective of upstream manufacturers, both regular and irregular orders are considered in coping with the situation in which an uncertain demand is faced by the manufacturer, and a capacity confirming mechanism is used to examine such demand. If the demand is less than or equal to the capacity of the ordinary production channel, the general supply channel is utilised to fully account for the manufacturing process, but if the demand is greater than the capacity of the ordinary production channel, the contingency production channel would be activated along with the ordinary channel to satisfy the upcoming high demand. Besides, the reproductive property of the probability distribution is employed to represent the order quantity of the two types of demand. Accordingly, the optimal production rates and lot sizes for both channels are derived to provide managers with insights for further production planning.

  18. Outage Capacity Analysis of TAS/MRC Systems over Arbitrary Nakagami-m Fading Channels

    Science.gov (United States)

    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.

  19. RESEARCH ON SYSTEM DYNAMICS MODEL OF CONVEYANCE CAPACITY IN SYMMETRIC COMPOUND CHANNELS

    Institute of Scientific and Technical Information of China (English)

    YANG Ke-jun; CAO Shu-you; LIU Xing-nian

    2005-01-01

    Stage-discharge curves are particularly important in river basin management. For a compound channel, the stage-discharge curve is often difficult to be extrapolated to yield estimates of level for a given frequency of flow. By analyzing a large number of experimental data from Science and Engineering Research Council Flood Channel Facility (SERC-FCF) and applying system dynamics method, the authors established system dynamics model of conveyance capacity when rivers flow in an overbank mode, spilling onto the adjoining flood plain. The model was applied to a compound channel. And the corresponding simulated results are shown to attain high accurcy.

  20. The Approximate Capacity Region of the Symmetric $K$-user Gaussian Interference Channel with Strong Interference

    KAUST Repository

    Chaaban, Anas

    2016-03-01

    The symmetric K-user interference channel is studied with the goal of characterizing its capacity region in the strong interference regime within a constant gap. The achievable rate region of a scheme combining rate-splitting at the transmitters and interference alignment and successive decoding/computation at the receivers is derived. Next it is shown that this scheme achieves the so-called greedy-max corner points of the capacity region within a constant gap. By combining this result with previous results by Ordentlich et al. on the sum-capacity of the symmetric interference channel, a constant gap characterization of the capacity region for the strong interference regime is obtained. This leads to the first approximate characterization of the capacity region of the symmetric K-user IC. Furthermore, a new scheme that achieves the sum-capacity of the channel in the strong interference regime within a constant gap is also proposed, and the corresponding gap is calculated. The advantage of the new scheme is that it leads to a characterization within a constant gap without leaving an outage set contrary to the scheme by Ordentlich et al..

  1. Zero-error channel capacity and simulation assisted by non-local correlations

    CERN Document Server

    Cubitt, Toby S; Matthews, William; Winter, Andreas

    2010-01-01

    Shannon's theory of zero-error communication is re-examined in the broader setting of using one classical channel to simulate another exactly, and in the presence of various resources that are all classes of non-signalling correlations: Shared randomness, shared entanglement and arbitrary non-signalling correlations. Specifically, when the channel being simulated is noiseless, this reduces to the zero-error capacity of the channel, assisted by the various classes of non-signalling correlations. When the resource channel is noiseless, it results in the "reverse" problem of simulating a noisy channel exactly by a noiseless one, assisted by correlations. In both cases, 'one-shot' separations between the power of the different assisting correlations are exhibited. The most striking result of this kind is that entanglement can assist in zero-error communication, in stark contrast to the standard setting of communicaton with asymptotically vanishing error in which entanglement does not help at all. In the asymptoti...

  2. On the Capacity of the Interference Channel with a Cognitive Relay

    CERN Document Server

    Rini, Stefano; Devroye, Natasha; Goldsmith, Andrea

    2011-01-01

    The InterFerence Channel with a Cognitive Relay (IFC-CR) consists of the classical interference channel with two independent source-destination pairs whose communication is aided by an additional node, referred to as the cognitive relay, that has a priori knowledge of both sources' messages. This a priori message knowledge is termed cognition and idealizes the relay learning the messages of the two sources from their transmissions over a wireless channel. This paper presents new inner and outer bounds for the capacity region of the general memoryless IFC-CR that are shown to be tight for a certain class of channels. The new outer bound follows from arguments originally devised for broadcast channels among which Sato's observation that the capacity region of channels with non-cooperative receivers only depends on the channel output conditional marginal distributions. The new inner bound is shown to include all previously proposed coding schemes and it is thus the largest known achievable rate region to date. T...

  3. The Shannon capacity of a communication channel,graph Ramsey number anda conjecture of Erd(o)s

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    We briefly introduce the connection betweenthe Shannon capacity of a communication channel andgraph Ramsey number, which may receive attention fromresearchers on communication theory and graph theory.

  4. On the low SNR capacity of log-normal turbulence channels with full CSI

    KAUST Repository

    Benkhelifa, Fatma

    2014-09-01

    In this paper, we characterize the low signal-To-noise ratio (SNR) capacity of wireless links undergoing the log-normal turbulence when the channel state information (CSI) is perfectly known at both the transmitter and the receiver. We derive a closed form asymptotic expression of the capacity and we show that it scales essentially as λ SNR where λ is the water-filling level satisfying the power constraint. An asymptotically closed-form expression of λ is also provided. Using this framework, we also propose an on-off power control scheme which is capacity-achieving in the low SNR regime.

  5. The capacity of a class of 3-receiver broadcast channels with degraded message sets

    CERN Document Server

    Nair, Chandra

    2007-01-01

    Korner and Marton established the capacity region for the 2-receiver broadcast channel with degraded message sets. No progress has been made since this work on extending their result to broadcast channels with more than 2 receivers, even with only 2 degraded message sets. In a recent paper, it was conjectured that the straightforward extension of the Korner-Marton region to more than 2 receivers is optimal for the class of multilevel broadcast channels. In this paper we show that this conjecture is false. We establish the capacity region for 3-receiver multilevel broadcast channels and show that it can be strictly larger than the straightforward extension of the Korner-Marton region. The key new idea is indirect decoding, whereby a receiver who cannot directly decode a cloud center, finds it indirectly by decoding satellite codewords. This idea is then used to establish new inner and outer bounds on the capacity region of the general 3-receiver broadcast channel with 2 and 3 degraded message sets. We show tha...

  6. Feedback Capacity of the Gaussian Interference Channel to within 2 Bits

    CERN Document Server

    Suh, Changho

    2010-01-01

    We characterize the capacity region to within 2 bits/s/Hz and the symmetric capacity to within 1 bit/s/Hz for the two-user Gaussian interference channel (IC) with feedback. We develop achievable schemes and derive a new outer bound to arrive at this conclusion. One consequence of the result is that feedback provides multiplicative gain, i.e., the gain becomes arbitrarily large for certain channel parameters. It is a surprising result because feedback has been so far known to provide no gain in memoryless point-to-point channels and only bounded additive gain in multiple access channels. The gain comes from using feedback to maximize resource utilization, thereby enabling more efficient resource sharing between the interfering users. The result makes use of a deterministic model to provide insights into the Gaussian channel. This deterministic model is a special case of El Gamal-Costa deterministic model and as a side-generalization, we establish the exact feedback capacity region of this general class of dete...

  7. Low-SNR Capacity of Parallel IM-DD Optical Wireless Channels

    KAUST Repository

    Chaaban, Anas

    2016-11-29

    The capacity of parallel intensity-modulation and direct-detection (IM-DD) optical wireless channels with total average intensity and per-channel peak intensity constraints is studied. The optimal intensity allocation at low signal-to-noise ratio (SNR) is derived, leading to the capacity-achieving onoff keying (OOK) distribution. Interestingly, while activating the strongest channel is optimal if (i) the peak intensity is fixed, this is not the case if (ii) the peak intensity is proportional to the average intensity. The minimum average optical intensity per bit is also studied, and is characterized for case (i) where it is achievable at low SNR. However, in case (ii), the average optical intensity per bit grows indefinitely as SNR decreases, indicating that lower optical intensity per bit can be achieved at moderate SNR than at low SNR.

  8. Distributed Antenna Channels with Regenerative Relaying: Relay Selection and Asymptotic Capacity

    Directory of Open Access Journals (Sweden)

    Aitor del Coso

    2007-11-01

    Full Text Available Multiple-input-multiple-output (MIMO techniques have been widely proposed as a means to improve capacity and reliability of wireless channels, and have become the most promising technology for next generation networks. However, their practical deployment in current wireless devices is severely affected by antenna correlation, which reduces their impact on performance. One approach to solve this limitation is relaying diversity. In relay channels, a set of N wireless nodes aids a source-destination communication by relaying the source data, thus creating a distributed antenna array with uncorrelated path gains. In this paper, we study this multiple relay channel (MRC following a decode-and-forward (D&F strategy (i.e., regenerative forwarding, and derive its achievable rate under AWGN. A half-duplex constraint on relays is assumed, as well as distributed channel knowledge at both transmitter and receiver sides of the communication. For this channel, we obtain the optimum relay selection algorithm and the optimum power allocation within the network so that the transmission rate is maximized. Likewise, we bound the ergodic performance of the achievable rate and derive its asymptotic behavior in the number of relays. Results show that the achievable rate of regenerative MRC grows as the logarithm of the Lambert W function of the total number of relays, that is, 𝒞=log⁡2(W0(N. Therefore, D&F relaying, cannot achieve the capacity of actual MISO channels.

  9. Distributed Antenna Channels with Regenerative Relaying: Relay Selection and Asymptotic Capacity

    Directory of Open Access Journals (Sweden)

    del Coso Aitor

    2007-01-01

    Full Text Available Multiple-input-multiple-output (MIMO techniques have been widely proposed as a means to improve capacity and reliability of wireless channels, and have become the most promising technology for next generation networks. However, their practical deployment in current wireless devices is severely affected by antenna correlation, which reduces their impact on performance. One approach to solve this limitation is relaying diversity. In relay channels, a set of wireless nodes aids a source-destination communication by relaying the source data, thus creating a distributed antenna array with uncorrelated path gains. In this paper, we study this multiple relay channel (MRC following a decode-and-forward (D&F strategy (i.e., regenerative forwarding, and derive its achievable rate under AWGN. A half-duplex constraint on relays is assumed, as well as distributed channel knowledge at both transmitter and receiver sides of the communication. For this channel, we obtain the optimum relay selection algorithm and the optimum power allocation within the network so that the transmission rate is maximized. Likewise, we bound the ergodic performance of the achievable rate and derive its asymptotic behavior in the number of relays. Results show that the achievable rate of regenerative MRC grows as the logarithm of the Lambert W function of the total number of relays, that is, . Therefore, D&F relaying, cannot achieve the capacity of actual MISO channels.

  10. Quantum Enigma Machines and the Locking Capacity of a Quantum Channel

    Science.gov (United States)

    Guha, Saikat; Hayden, Patrick; Krovi, Hari; Lloyd, Seth; Lupo, Cosmo; Shapiro, Jeffrey H.; Takeoka, Masahiro; Wilde, Mark M.

    2014-01-01

    The locking effect is a phenomenon that is unique to quantum information theory and represents one of the strongest separations between the classical and quantum theories of information. The Fawzi-Hayden-Sen locking protocol harnesses this effect in a cryptographic context, whereby one party can encode n bits into n qubits while using only a constant-size secret key. The encoded message is then secure against any measurement that an eavesdropper could perform in an attempt to recover the message, but the protocol does not necessarily meet the composability requirements needed in quantum key distribution applications. In any case, the locking effect represents an extreme violation of Shannon's classical theorem, which states that information-theoretic security holds in the classical case if and only if the secret key is the same size as the message. Given this intriguing phenomenon, it is of practical interest to study the effect in the presence of noise, which can occur in the systems of both the legitimate receiver and the eavesdropper. This paper formally defines the locking capacity of a quantum channel as the maximum amount of locked information that can be reliably transmitted to a legitimate receiver by exploiting many independent uses of a quantum channel and an amount of secret key sublinear in the number of channel uses. We provide general operational bounds on the locking capacity in terms of other well-known capacities from quantum Shannon theory. We also study the important case of bosonic channels, finding limitations on these channels' locking capacity when coherent-state encodings are employed and particular locking protocols for these channels that might be physically implementable.

  11. Many-body physics and the capacity of quantum channels with memory

    Energy Technology Data Exchange (ETDEWEB)

    Plenio, M B; Virmani, S [QOLS, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom)], E-mail: s.virmani@imperial.ac.uk

    2008-04-15

    In most studies of the capacity of quantum channels, it is assumed that the errors in the use of each channel are independent. However, recent work has begun to investigate the effects of memory or correlations in the error, and has led to suggestions that there can be interesting non-analytic behaviour in the capacity of such channels. In a previous paper, we pursued this issue by connecting the study of channel capacities under correlated error to the study of critical behaviour in many-body physics. This connection enables the use of techniques from many-body physics to either completely solve or understand qualitatively a number of interesting models of correlated error with analogous behaviour to associated many-body systems. However, in order for this approach to work rigorously, there are a number of technical properties that need to be established for the lattice systems being considered. In this paper, we discuss these properties in detail, and establish them for some classes of many-body system.

  12. Next-to-leading-order corrections to capacity for a nondispersive nonlinear optical fiber channel in the intermediate power region

    Science.gov (United States)

    Panarin, A. A.; Reznichenko, A. V.; Terekhov, I. S.

    2017-01-01

    We consider the optical fiber channel modeled by the nonlinear Schrödinger equation with zero dispersion and additive Gaussian noise. Using the Feynman path-integral approach for the model, we find corrections to conditional probability density function, output signal distribution, conditional and output signal entropies, and the channel capacity at large signal-to-noise ratio. We demonstrate that the correction to the channel capacity is positive for large signal power. Therefore, this correction increases the earlier calculated capacity for a nondispersive nonlinear optical fiber channel in the intermediate power region.

  13. Sum Capacity of Gaussian Interfering Multiple Access Channels in the Low Interference Regime

    CERN Document Server

    Jose, Jubin; Vishwanath, Sriram

    2011-01-01

    This paper establishes the sum capacity of Gaussian interfering multiple access channels (IF-MACs) in a low interference regime. IF-MACs studied consist of two MACs, with arbitrary number of users, interfering with each other. In the low interference regime, treating interference as noise along with successive decoding is shown to be sum rate optimal. The regime characterized in this paper solely depends on the minimum direct to indirect channel gain ratios, net interference to noise ratio and net signal to noise ratio associated with both MACs.

  14. Digital non-linear equalization for flexible capacity ultradense WDM channels for metro core networking.

    Science.gov (United States)

    Arlunno, Valeria; Zhang, Xu; Larsen, Knud J; Zibar, Darko; Monroy, Idelfonso Tafur

    2011-12-12

    An experimental demonstration of Ultradense WDM with advanced digital signal processing is presented. The scheme proposed allows the use of independent tunable DFB lasers spaced at 12.5 GHz for ultradense WDM PM-QPSK flexible capacity channels for metro core networking. To allocate extremely closed carriers, we demonstrate that a digital non-linear equalization allow to mitigate inter-channel interference and improve overall system performance in terms of OSNR. Evaluation of the algorithm and comparison with an ultradense WDM system with coherent carriers generated from a single laser are also reported. © 2011 Optical Society of America

  15. Digital non-linear equalization for flexible capacity ultradense WDM channels for metro core networking

    DEFF Research Database (Denmark)

    Arlunno, Valeria; Zhang, Xu; Larsen, Knud J.

    2011-01-01

    An experimental demonstration of Ultradense WDM with advanced digital signal processing is presented. The scheme proposed allows the use of independent tunable DFB lasers spaced at 12.5 GHz for ultradense WDM PM-QPSK flexible capacity channels for metro core networking. To allocate extremely closed...... carriers, we demonstrate that a digital non-linear equalization allow to mitigate inter-channel interference and improve overall system performance in terms of OSNR. Evaluation of the algorithm and comparison with an ultradense WDM system with coherent carriers generated from a single laser are also...

  16. Lower Bounds on the Capacity of the Relay Channel with States at the Source

    Directory of Open Access Journals (Sweden)

    Abdellatif Zaidi

    2009-01-01

    Full Text Available We consider a state-dependent three-terminal full-duplex relay channel with the channel states noncausally available at only the source, that is, neither at the relay nor at the destination. This model has application to cooperation over certain wireless channels with asymmetric cognition capabilities and cognitive interference relay channels. We establish lower bounds on the channel capacity for both discrete memoryless (DM and Gaussian cases. For the DM case, the coding scheme for the lower bound uses techniques of rate-splitting at the source, decode-and-forward (DF relaying, and a Gel'fand-Pinsker-like binning scheme. In this coding scheme, the relay decodes only partially the information sent by the source. Due to the rate-splitting, this lower bound is better than the one obtained by assuming that the relay decodes all the information from the source, that is, full-DF. For the Gaussian case, we consider channel models in which each of the relay node and the destination node experiences on its link an additive Gaussian outside interference. We first focus on the case in which the links to the relay and to the destination are corrupted by the same interference; and then we focus on the case of independent interferences. We also discuss a model with correlated interferences. For each of the first two models, we establish a lower bound on the channel capacity. The coding schemes for the lower bounds use techniques of dirty paper coding or carbon copying onto dirty paper, interference reduction at the source and decode-and-forward relaying. The results reveal that, by opposition to carbon copying onto dirty paper and its root Costa's initial dirty paper coding (DPC, it may be beneficial in our setup that the informed source uses a part of its power to partially cancel the effect of the interference so that the uninformed relay benefits from this cancellation, and so the source benefits in turn.

  17. On the Capacity of FSO Links over Gamma-Gamma Atmospheric Turbulence Channels Using OOK Signaling

    Directory of Open Access Journals (Sweden)

    Antonio García-Zambrana

    2010-01-01

    Full Text Available A new upper bound on the capacity of power- and bandwidth-constrained optical wireless links over gamma-gamma atmospheric turbulence channels with intensity modulation and direct detection is derived when on-off keying (OOK formats are used. In this free-space optical (FSO scenario, unlike previous capacity bounds derived from the classic capacity of the well-known additive white Gaussian noise (AWGN channel with uniform input distribution, a new closed-form upper bound on the capacity is found by bounding the mutual information subject to an average optical power constraint and not only to an average electrical power constraint, showing the fact that the input distribution that maximizes the mutual information varies with the turbulence strength and the signal-to-noise ratio (SNR. Additionally, it is shown that an increase of the peak-to-average optical power ratio (PAOPR provides higher capacity values. Simulation results for the mutual information are further demonstrated to confirm the analytical results under several turbulence conditions.

  18. A unified MGF-based capacity analysis of diversity combiners over generalized fading channels

    KAUST Repository

    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.

  19. A Unified MGF-Based Capacity Analysis of Diversity Combiners over Generalized Fading Channels

    CERN Document Server

    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.

  20. The Capacity of the Semi-Deterministic Cognitive Interference Channel with a Common Cognitive Message and Approximate Capacity for the Gaussian Case

    CERN Document Server

    Rini, Stefano

    2012-01-01

    In this paper the study of the cognitive interference channel with a common message, a variation of the classical cognitive interference channel in which the cognitive message is decoded at both receivers. We derive the capacity for the semideterministic channel in which the output at the cognitive decoder is a deterministic function of the channel inputs. We also show capacity to within a constant gap and a constant factor for the Gaussian channel in which the outputs are linear combinations of the channel inputs plus an additive Gaussian noise term. Most of these results are shown using an interesting transmission scheme in which the cognitive message, decoded at both receivers, is also pre-coded against the interference experienced at the cognitive decoder. The pre-coding of the cognitive message does not allow the primary decoder to reconstruct the interfering signal. The cognitive message acts instead as a side information at the primary receiver when decoding its intended message.

  1. Capacity bounds for the 2-user Gaussian IM-DD optical multiple-access channel

    KAUST Repository

    Al-Ebraheemy, Omer M. S.

    2016-11-01

    Optical wireless communications (OWC) is a potential solution for coping with the mismatch between the users growing demand for higher data-rates and the wireless network capabilities. In this paper, a multi-user OWC scenario is studied from an in formation-theoretic perspective. The studied network consists of two users communicating simultaneously with one access point using OWC, thus establishing an optical uplink channel. The capacity of this network is an important metric which reflects the highest possible communication rates that can be achieved over this channel. Capacity outer and inner bounds are derived, and are shown to be fairly tight in the high signal-to-noise ratio regime. © 2016 IEEE.

  2. Superimposed XOR: Approaching Capacity Bounds of the Two-Way Relay Channels

    CERN Document Server

    Liu, Jianquan; Xu, Youyun; Wang, Xiaodong

    2010-01-01

    In two-way relay channels, bitwise XOR and symbol-level superposition coding are two popular network-coding based relaying schemes. However, neither of them can approach the capacity bound when the channels in the broadcast phase are asymmetric. In this paper, we present a new physical layer network coding (PLNC) scheme, called \\emph{superimposed XOR}. The new scheme advances the existing schemes by specifically taking into account the channel asymmetry as well as information asymmetry in the broadcast phase. We obtain its achievable rate regions over Gaussian channels when integrated with two known time control protocols in two-way relaying. We also demonstrate their average maximum sum-rates and service delay performances over fading channels. Numerical results show that the proposed superimposed XOR achieves a larger rate region than both XOR and superposition and performs much better over fading channels. We further deduce the boundary of its achievable rate region of the broadcast phase in an explicit an...

  3. Geometry of human vocal folds and glottal channel for mathematical and biomechanical modeling of voice production.

    Science.gov (United States)

    Sidlof, Petr; Svec, Jan G; Horácek, Jaromír; Veselý, Jan; Klepácek, Ivo; Havlík, Radan

    2008-01-01

    Current models of the vocal folds derive their shape from approximate information rather than from exactly measured data. The objective of this study was to obtain detailed measurements on the geometry of human vocal folds and the glottal channel in phonatory position. A non-destructive casting methodology was developed to capture the vocal fold shape from excised human larynges on both medial and superior surfaces. Two female larynges, each in two different phonatory configurations corresponding to low and high fundamental frequency of the vocal fold vibrations, were measured. A coordinate measuring machine was used to digitize the casts yielding 3D computer models of the vocal fold shape. The coronal sections were located in the models, extracted and fitted by piecewise-defined cubic functions allowing a mathematical expression of the 2D shape of the glottal channel. Left-right differences between the cross-sectional shapes of the vocal folds were found in both the larynges.

  4. A Lower Bound on the per Soliton Capacity of the Nonlinear Optical Fibre Channel

    CERN Document Server

    Shevchenko, Nikita A; Derevyanko, Stanislav A; Alvarado, Alex; Bayvel, Polina; Turitsyn, Sergei K

    2015-01-01

    A closed-form expression for a lower bound on the per soliton capacity of the nonlinear optical fibre channel in the presence of (optical) amplifier spontaneous emission (ASE) noise is derived. This bound is based on a non-Gaussian conditional probability density function for the soliton amplitude jitter induced by the ASE noise and is proven to grow logarithmically as the signal-to-noise ratio increases.

  5. On the capacity of cognitive radio under limited channel state information

    KAUST Repository

    Rezki, Zouheir

    2010-09-01

    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 of the secondary transmitter-primary receiver 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 that the interference constraint is harmful at high-power regime, whereas at lowpower regime, it has a marginal impact and no-interference performance may be achieved. © 2010 IEEE.

  6. A Unified Simulation Approach for the Fast Outage Capacity Evaluation over Generalized Fading Channels

    KAUST Repository

    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.

  7. On the Capacity Region for Cognitive Multiple Access over White Space Channels

    CERN Document Server

    Zhang, Huazi; Zhang, Zhaoyang

    2012-01-01

    Cognitive Radio (CR) has stirred great interest with its potential to exploit the already scarce spectrum resource. The cognitive multiple access channels (CogMAC) are commonly seen in many applications, such as the Cognitive Radio Sensor Networks (CRSN), and the 802.22 cognitive Wireless Regional Area Networks (WRAN). In this paper, the primary user (PU) activities are treated as on/off side information, which can be obtained causally or non-causally. The cognitive MAC channels are then modeled as multi-switch channels and their rate regions are characterized. Explicit forms of outer and inner bounds of this rate region are derived by assuming additional side information, and they are shown to be tight in some special cases. An optimal rate and power allocation scheme that maximizes the sum rate is also proposed. The numerical results show the importance of side information in enhancing the capacity and the effectiveness of our rate allocation scheme.

  8. A unified simulation approach for the fast outage capacity evaluation over generalized fading channels

    KAUST Repository

    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.

  9. Ergodic Capacity of Cognitive Radio Under Imperfect Channel-State Information

    KAUST Repository

    Rezki, Zouheir

    2012-09-08

    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 link is investigated. The optimum power profile and the ergodic capacity of the secondary link are derived for general fading channels [with a continuous probability density function (pdf)] under the average and peak transmit power constraints and with respect to the following two different interference constraints: 1) an interference outage constraint and 2) a signal-to-interference outage constraint. When applied to Rayleigh fading channels, our results show, for example, that the interference constraint is harmful at the high-power regime, because the capacity does not increase with the power, whereas at the low-power regime, it has a marginal impact and no-interference performance, which corresponds to the ergodic capacity under average or peak transmit power constraint in the absence of the primary user, may be achieved. © 2012 IEEE.

  10. Capacity limits of spectrum-sharing systems over hyper-fading channels

    KAUST Repository

    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.

  11. Capacity Bounds for the Gaussian IM-DD Optical Multiple-Access Channel

    KAUST Repository

    Chaaban, Anas

    2017-03-18

    Optical wireless communications (OWC) is a promising technology for closing the mismatch between the growing number of connected devices and the limited wireless network capabilities. Similar to downlink, uplink can also benefit from OWC for establishing connectivity between such devices and an optical access point. In this context, the incoherent intensitymodulation and direct-detection (IM-DD) scheme is desirable in practice. Hence, it is important to understand the fundamental limits of communication rates over an OWC uplink employing IM-DD, i.e., the channel capacity. This uplink, modeled as a Gaussian multiple-access channel (MAC) for indoors OWC, is studied in this paper, under the IM-DD constraints which form the main difference with the standard Gaussian MAC commonly studied in the radio-frequency context. Capacity region outer and inner bounds for this channel are derived. The bounds are fairly close at high signal-to-noise ratio (SNR), where a truncated- Gaussian input distribution achieves the capacity region within a constant gap. Furthermore, the bounds coincide at low SNR showing the optimality of on-off keying combined with successive cancellation decoding in this regime. At moderate SNR, an optimized uniformly-spaced discrete input distribution achieves fairly good performance.

  12. Achievable capacity of a spectrum sharing system over hyper fading channels

    KAUST Repository

    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.

  13. On the Ergodic Capacity of Dual-Branch Correlated Log-Normal Fading Channels with Applications

    KAUST Repository

    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.

  14. Channel-conveyance capacity, channel change, and sediment transport in the lower Puyallup, White, and Carbon Rivers, western Washington

    Science.gov (United States)

    Czuba, Jonathan A.; Czuba, Christiana R.; Magirl, Chistopher S.; Voss, Frank D.

    2010-01-01

    Draining the volcanic, glaciated terrain of Mount Rainier, Washington, the Puyallup, White, and Carbon Rivers convey copious volumes of water and sediment down to Commencement Bay in Puget Sound. Recent flooding in the lowland river system has renewed interest in understanding sediment transport and its effects on flow conveyance throughout the lower drainage basin. Bathymetric and topographic data for 156 cross sections were surveyed in the lower Puyallup River system by the U.S. Geological Survey (USGS) and were compared with similar datasets collected in 1984. Regions of significant aggradation were measured along the Puyallup and White Rivers. Between 1984 and 2009, aggradation totals as measured by changes in average channel elevation were as much as 7.5, 6.5, and 2 feet on the Puyallup, White, and Carbon Rivers, respectively. These aggrading river sections correlated with decreasing slopes in riverbeds where the rivers exit relatively confined sections in the upper drainage and enter the relatively unconstricted valleys of the low-gradient Puget Lowland. Measured grain-size distributions from each riverbed showed a progressive fining downstream. Analysis of stage-discharge relations at streamflow-gaging stations along rivers draining Mount Rainier demonstrated the dynamic nature of channel morphology on river courses influenced by glaciated, volcanic terrain. The greatest rates of aggradation since the 1980s were in the Nisqually River near National (5.0 inches per year) and the White River near Auburn (1.8 inches per year). Less pronounced aggradation was measured on the Puyallup River and the White River just downstream of Mud Mountain Dam. The largest measured rate of incision was measured in the Cowlitz River at Packwood (5.0 inches per year). Channel-conveyance capacity estimated using a one-dimensional hydraulic model decreased in some river reaches since 1984. The reach exhibiting the largest decrease (about 20-50 percent) in channel

  15. Capacity of Strong and Very Strong Gaussian Interference Relay-without-delay Channels

    CERN Document Server

    Chang, Hyunseok

    2011-01-01

    In this paper, we study the interference relay-without-delay channel which is an interference channel with a relay helping the communication. We assume the relay's transmit symbol depends not only on its past received symbols but also on its current received symbol, which is an appropriate model for studying amplify-and-forward type relaying when the overall delay spread is much smaller than the inverse of the bandwidth. For the discrete memoryless interference relay-without-delay channel, we show an outer bound using genie-aided outer bounding. For the Gaussian interference relay-without-delay channel, we define strong and very strong interference relay-without-delay channels and propose an achievable scheme based on instantaneous amplify-and-forward (AF) relaying. We also propose two outer bounds for the strong and very strong cases. Using the proposed achievable scheme and outer bounds, we show that our scheme can achieve the capacity exactly when the relay's transmit power is greater than a certain thresh...

  16. Mathematical expression of discharge capacity of compound open channels using MARS technique

    Science.gov (United States)

    Parsaie, Abbas; Haghiabi, Amir Hamzeh

    2017-03-01

    In this paper, analytical methods, artificial neural network (ANN) and multivariate adaptive regression splines (MARS) techniques were utilised to estimate the discharge capacity of compound open channels (COC). To this end, related datasets were collected from literature. The results showed that the divided channel method with a coefficient of determination ( R 2) value of 0.76 and root mean square error (RMSE) value of 0.162 has the best performance, among the various analytical methods tested. The performance of applied soft computing models with R 2=0.97 and RMSE = 0.03 was found to be more accurate than analytical approaches. Comparison of MARS with the ANN model, in terms of developed discrepancy ratio (DDR) index, showed that the accuracy of MARS model was better than that of MLP model. Reviewing the structure of the derived MARS model showed that the longitudinal slope of the channel ( S), relative flow depth ( H r ) and relative area ( A r ) have a high impact on modelling and forecasting the discharge capacity of COCs.

  17. Meandered Monopoles for 700 MHz LTE Handsets and Improved MIMO Channel Capacity Performance

    Directory of Open Access Journals (Sweden)

    I. Dioum

    2011-12-01

    Full Text Available In this paper, we present the design and the measurement of MIMO meandered monopole antennas and the computation of their channel capacity performance. The initial proposed handset-system is composed of a meandered monopole operating in the LTE 700 MHz band, connected to a parasitic radiating element for the upper 2.5 GHz LTE band. Two antennas of the same kind are then closely positioned on the same 120x50 mm2 Printed Circuit Board (PCB. A neutralization line connects the two antennas to enhance their port-to-port isolation in the 700 MHz band. The computation of the channel capacity performance in this band is based on propagation simulations performed with the GRIMM model from the CREMANT. Two system-prototypes are evaluated: one with the neutralization line for enhanced port-to-port isolation and a second without the neutralization exhibiting poor antenna-to-antenna isolation. It is demonstrated that the neutralization technique helps in giving a minimum improvement of 12% of the capacity performance of the handset-system, and a maximum improvement 46%, in the chosen environment.

  18. Achieving the capacity of half-duplex degraded relay channels using polar coding

    Institute of Scientific and Technical Information of China (English)

    Duo Bin; Wang Zhenyong; Gu Xuemai; Guo Qing

    2014-01-01

    In this paper, a novel transmission protocol based on polar coding is proposed for the half-duplex degraded relay channel. In the proposed protocol, referred to as the partial message relaying, the relay only needs to forward a part of the decoded source message that the destination needs according to the exquisite nested structure of polar codes. Theoretically, it is proved that the scheme can achieve the capacity of the half-duplex relay channel under the decode-and-forward (DF) cooperation strategy while enjoying low encoding/decoding complexity. Practically, in order to minimize the global transmission power, the optimization of the power allocation is performed between the source and the relay by using information theoretic tools. Furthermore, a joint iterative soft parallel interference cancellation receiver structure is developed to suit to the proposed scheme. Simulation results show that the proposed scheme outperforms the conventional scheme designed by low-density parity-check (LDPC) codes.

  19. On the Capacity of Memoryless Finite-State Multiple-Access Channels with Asymmetric State Information at the Encoders

    CERN Document Server

    Como, Giacomo

    2010-01-01

    A single-letter characterization is provided for the capacity region of finite-state multiple-access channels, when the channel state process is an independent and identically distributed sequence, the transmitters have access to partial (quantized) state information, and complete channel state information is available at the receiver. The partial channel state information is assumed to be asymmetric at the encoders. As a main contribution, a tight converse coding theorem is presented. The difficulties associated with the case when the channel state has memory are discussed and connections to decentralized stochastic control theory are presented.

  20. An Isomorphism between Lyapunov Exponents and Shannon's Channel Capacity

    Energy Technology Data Exchange (ETDEWEB)

    Friedland, Gerald [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Metere, Alfredo [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-06-07

    We demonstrate that discrete Lyapunov exponents are isomorphic to numeric overflows of the capacity of an arbitrary noiseless and memoryless channel in a Shannon communication model with feedback. The isomorphism allows the understanding of Lyapunov exponents in terms of Information Theory, rather than the traditional definitions in chaos theory. The result also implies alternative approaches to the calculation of related quantities, such as the Kolmogorov Sinai entropy which has been linked to thermodynamic entropy. This work provides a bridge between fundamental physics and information theory. It suggests, among other things, that machine learning and other information theory methods can be employed at the core of physics simulations.

  1. Outage and Capacity Performance Evaluation of Distributed MIMO Systems over a Composite Fading Channel

    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.

  2. On the Relationship between Transmission Power and Capacity of an Underwater Acoustic Communication Channel

    CERN Document Server

    Lucani, Daniel E; Médard, Muriel

    2008-01-01

    The underwater acoustic channel is characterized by a path loss that depends not only on the transmission distance, but also on the signal frequency. As a consequence, transmission bandwidth depends on the transmission distance, a feature that distinguishes an underwater acoustic system from a terrestrial radio system. The exact relationship between power, transmission band, distance and capacity for the Gaussian noise scenario is a complicated one. This work provides a closed-form approximate model for 1) power consumption, 2) band-edge frequency and 3) bandwidth as functions of distance and capacity required for a data link. This approximate model is obtained by numerical evaluation of analytical results which takes into account physical models of acoustic propagation loss and ambient noise. The closed-form approximations may become useful tools in the design and analysis of underwater acoustic networks.

  3. On the Capacity of the Intensity-Modulation Direct-Detection Optical Broadcast Channel

    KAUST Repository

    Chaaban, Anas

    2016-01-12

    The capacity of the intensity-modulation directdetection optical broadcast channel (OBC) is investigated, under both average and peak intensity constraints. An outer bound on the capacity region is derived by adapting Bergmans’ approach to the OBC. Inner bounds are derived by using superposition coding with either truncated-Gaussian (TG) distributions or discrete distributions. While the discrete distribution achieves higher rates, the TG distribution leads to a simpler representation of the achievable rate region. At high signal-to-noise ratio (SNR), it is shown that the TG distribution is nearly optimal. It achieves the symmetric-capacity within a constant gap (independent of SNR), which approaches half a bit as the number of users grows. It also achieves the capacity region within a constant gap. At low SNR, it is shown that on-off keying (OOK) with time-division multipleaccess (TDMA) is optimal. This is interesting in practice since both OOK and TDMA have low complexity. At moderate SNR (typically [0,8] dB), a discrete distribution with a small alphabet size achieves fairly good performance.

  4. On the Capacity Region of the Intensity-Modulation Direct-Detection Optical Broadcast Channel

    KAUST Repository

    Chaaban, Anas

    2015-08-11

    The capacity of the intensity-modulation direct-detection free-space optical broadcast channel (OBC) is investigated. The Gaussian model with input-independent Gaussian noise is used, with both average and peak intensity constraints. An outer bound on the capacity region is derived by adapting Bergmans\\' approach to the OBC. Inner bounds are derived by using superposition coding with either truncated-Gaussian distributions or discrete distributions. While the discrete input distribution achieves higher rates than the truncated-Gaussian distribution, the latter allows expressing the achievable rate region in a closed form. At high signal-to-noise ratio (SNR), it is shown that the truncated-Gaussian distribution is nearly optimal. It achieves the symmetric-capacity within a constant gap (independent of SNR), which approaches half a bit as the number of users grows large. It also achieves the capacity region within a constant gap, which depends on the number of users. At low SNR, it is shown that on-off keying with time-division multiple-access (TDMA) is optimal, as it achieves any point on the boundary of the developed outer bound. This is interesting in practice since both OOK and TDMA have low complexity. At moderate SNR (typically [0,8] dB), a discrete distribution with a small alphabet size achieves a fairly good performance in terms of symmetric rate.

  5. List-Message Passing Achieves Capacity on the q-ary Symmetric Channel for Large q

    CERN Document Server

    Zhang, Fan

    2008-01-01

    We discuss and analyze a list-message-passing decoder with verification for low-density parity-check (LDPC) codes on the q-ary symmetric channel (q-SC). Rather than passing messages consisting of symbol probabilities, we pass lists of possible symbols and mark very likely symbols as verified. The density evolution (DE) equations for this decoder are derived and used to compute decoding thresholds. If the maximum list-size is unbounded, then we find that any capacity-achieving LDPC code for the binary erasure channel can be used to achieve capacity on the q-SC for large q. The decoding thresholds are also computed via DE for the case where each list is truncated to satisfy a maximum list-size constraint. We observe that one of the algorithms proposed in [7] is analyzed incorrectly and derive the correct analysis. The probability of false verification (FV) is also considered and techniques are discussed to mitigate the FV. Optimization of the degree distribution is also used to improve the threshold for a fixed...

  6. On the Capacity of the 2-User IM-DD Optical Broadcast Channel

    KAUST Repository

    Chaaban, Anas

    2016-02-26

    The capacity of the intensity-modulation directdetection (IM-DD) optical broadcast channel (OBC) is investigated. The OBC is modeled as a Gaussian channel with input-independent noise and both average and peak input constraints. Outer and inner bounds on the capacity region are derived. The outer bounds are based on Bergmans\\' approach. The inner bounds are based on superposition coding with either truncated-Gaussian or discrete input distributions. By comparing the bounds, we observe that the truncated- Gaussian distribution is nearly optimal at high signal-to-noise ratio (SNR). At low SNR on the other hand, on-off keying (OOK) combined with time-division multiple-access (TDMA) is optimal; it achieves any point on the boundary of the developed outer bound. This is interesting in practice since both OOK and TDMA have low complexity. At moderate SNR (typically [0; 8] dB), a discrete input distribution with a small alphabet size achieves a fairly good performance. © 2015 IEEE.

  7. Mathematical expression of discharge capacity of compound open channels using MARS technique

    Indian Academy of Sciences (India)

    Abbas Parsaie; Amir Hamzeh Haghiabi

    2017-03-01

    In this paper, analytical methods, artificial neural network (ANN) and multivariate adaptive regression splines (MARS) techniques were utilised to estimate the discharge capacity of compound open channels (COC). To this end, related datasets were collected from literature. The results showed that the dividedchannel method with a coefficient of determination (R2) value of 0.76 and root mean square error (RMSE) value of 0.162 has the best performance, among the various analytical methods tested. The performance of applied soft computing models with R2 = 0.97 and RMSE = 0.03 was found to be more accurate than analytical approaches. Comparison of MARS with the ANN model, in terms of developed discrepancy ratio (DDR) index, showed that the accuracy of MARS model was better than that of MLP model. Reviewing the structure of the derived MARS model showed that the longitudinal slope of the channel (S), relative flow depth (Hr) and relative area (Ar) have a high impact on modelling and forecasting the discharge capacity of COCs.

  8. High-capacity, low-tortuosity, and channel-guided lithium metal anode

    Science.gov (United States)

    Zhang, Ying; Luo, Wei; Wang, Chengwei; Li, Yiju; Chen, Chaoji; Song, Jianwei; Dai, Jiaqi; Hitz, Emily M.; Xu, Shaomao; Yang, Chunpeng; Wang, Yanbin; Hu, Liangbing

    2017-04-01

    Lithium metal anode with the highest capacity and lowest anode potential is extremely attractive to battery technologies, but infinite volume change during the Li stripping/plating process results in cracks and fractures of the solid electrolyte interphase, low Coulombic efficiency, and dendritic growth of Li. Here, we use a carbonized wood (C-wood) as a 3D, highly porous (73% porosity) conductive framework with well-aligned channels as Li host material. We discovered that molten Li metal can infuse into the straight channels of C-wood to form a Li/C-wood electrode after surface treatment. The C-wood channels function as excellent guides in which the Li stripping/plating process can take place and effectively confine the volume change that occurs. Moreover, the local current density can be minimized due to the 3D C-wood framework. Therefore, in symmetric cells, the as-prepared Li/C-wood electrode presents a lower overpotential (90 mV at 3 mAṡcm-2), more-stable stripping/plating profiles, and better cycling performance (˜150 h at 3 mAṡcm-2) compared with bare Li metal electrode. Our findings may open up a solution for fabricating stable Li metal anode, which further facilitates future application of high-energy-density Li metal batteries.

  9. Approaching the MIMO Capacity with a Low-Rate Feedback Channel in V-BLAST

    Directory of Open Access Journals (Sweden)

    Lozano Angel

    2004-01-01

    Full Text Available This paper presents an extension of the vertical Bell Laboratories Layered Space-Time (V-BLAST architecture in which the closed-loop multiple-input multiple-output (MIMO capacity can be approached with conventional scalar coding, optimum successive decoding (OSD, and independent rate assignments for each transmit antenna. This theoretical framework is used as a basis for the proposed algorithms whereby rate and power information for each transmit antenna is acquired via a low-rate feedback channel. We propose the successive quantization with power control (SQPC and successive rate and power quantization (SRPQ algorithms. In SQPC, rate quantization is performed with continuous power control. This performs better than simply quantizing the rates without power control. A more practical implementation of SQPC is SRPQ, in which both rate and power levels are quantized. The performance loss due to power quantization is insignificant when 4–5 bits are used per antenna. Both SQPC and SRPQ show an average total rate close to the closed-loop MIMO capacity if a capacity-approaching scalar code is used per antenna.

  10. On the Capacity of a General Multiple-Access Channel and of a Cognitive Network in the Very Strong Interference Regime

    CERN Document Server

    Rini, Stefano

    2012-01-01

    The capacity of the multiple-access channel with any distribution of messages among the transmitting nodes was determined by Han in 1979 and the expression of the capacity region contains a number of rate bounds and that grows exponentially with the number of messages. We derive a more compact expression for the capacity region of this channel in which the number of rate bounds depends on the distribution of the messages at the encoders. Using this expression we prove capacity for a class of general cognitive network that we denote as "very strong interference" regime. In this regime there is no rate loss in having all the receivers decode all the messages and the capacity region reduces to the capacity of the compound multiple-access channel. This result generalizes the "very strong interference" capacity results for the interference channel, the cognitive interference channel, the interference channel with a cognitive relay and many others.

  11. A Methodology for Measuring Voice Quality Using PESQ and Interactive Voice Response in the GSM Channel Designed by OpenBTS

    Directory of Open Access Journals (Sweden)

    Pavol Partila

    2013-01-01

    Full Text Available This article discusses a methodology for rating the quality of mobile calls. Majority telecommunications service from the perspective of the whole world is using mobile telephony networks. One of the problems affecting this service and its quality are landscape barriers, which prevent the spread signal. Price and complex construction of classic BTS does not allow their dense distribution. In such cases, one solution is to use OpenBTS technology. Design of OpenBTS is more available, so it can be applied to much more places and more complex points. Purpose of this measurement is a model for effective stations deployment, due to shape and distribution of local barriers that reduce signal power, and thus the quality of speech. GSM access point for our mobile terminals is OpenBTS USRP N210 station. The PESQ method for evaluating of speech quality is compared with the subjective evaluation, which provides Asterisk PBX with IVR call back. Measurement method was taken into account the call quality depending on terminal position. The measured results and its processing bring knowledge to use this technology for more complicated locations with degraded signal level and increases the quality of voice services in telecommunications.

  12. Transmitter Optimization for Achieving Secrecy Capacity in Gaussian MIMO Wiretap Channels

    CERN Document Server

    Li, Jiangyuan

    2009-01-01

    We consider a Gaussian multiple-input multiple-output (MIMO) wiretap channel model, where there exists a transmitter, a legitimate receiver and an eavesdropper, each node equipped with multiple antennas. We study the problem of finding the optimal input covariance matrix that achieves secrecy capacity subject to a power constraint, which leads to a non-convex optimization problem that is in general difficult to solve. Existing results for this problem address the case in which the transmitter and the legitimate receiver have two antennas each and the eavesdropper has one antenna. For the general cases, it has been shown that the optimal input covariance matrix has low rank when the difference between the Grams of the eavesdropper and the legitimate receiver channel matrices is indefinite or semi-definite, while it may have low rank or full rank when the difference is positive definite. In this paper, the aforementioned non-convex optimization problem is investigated. In particular, for the multiple-input sing...

  13. Broadcast classical-quantum capacity region of two-phase bidirectional relaying channels

    Energy Technology Data Exchange (ETDEWEB)

    Boche, Holger; Cai, Minglai; Deppe, Christian [Technische Universitaet Muenchen, Fakultaet fuer Elektrotechnik und Informationstechnik, Lehrstuhl fuer Theoretische Informationstechnik (Germany)

    2014-07-01

    The transmission of quantum states over long distances is essential for future applications such as quantum networks. The direct transmission is limited by unavoidable losses of the channel. A promising alternative for long distance quantum states distribution is the use of quantum repeaters. We analyze a quantum repeater protocol which takes advantage of bidirectional communication. We consider a three-node quantum network which enables bidirectional communication between two nodes with a half-duplex relay node. The message m{sub 2} element of M{sub 2} is located at node 1 and the message m{sub 1} element of M{sub 1} is located at node 2, respectively. Our goal is that the message m{sub 2} element of M{sub 2} is known at node 2 and the message m{sub 1} element of M{sub 1} is known at node 1, respectively. We simplify the problem by assuming an a priori separation of the communication into two phases. The capacity of the first phase (MAC) is known. We determine the capacity region of the second phase (broadcast).

  14. Shannon information capacity of time reversal wideband multiple-input multiple-output system based on correlated statistical channels

    Science.gov (United States)

    Yu, Yang; Bing-Zhong, Wang; Shuai, Ding

    2016-05-01

    Utilizing channel reciprocity, time reversal (TR) technique increases the signal-to-noise ratio (SNR) at the receiver with very low transmitter complexity in complex multipath environment. Present research works about TR multiple-input multiple-output (MIMO) communication all focus on the system implementation and network building. The aim of this work is to analyze the influence of antenna coupling on the capacity of wideband TR MIMO system, which is a realistic question in designing a practical communication system. It turns out that antenna coupling stabilizes the capacity in a small variation range with statistical wideband channel response. Meanwhile, antenna coupling only causes a slight detriment to the channel capacity in a wideband TR MIMO system. Comparatively, uncorrelated stochastic channels without coupling exhibit a wider range of random capacity distribution which greatly depends on the statistical channel. The conclusions drawn from information difference entropy theory provide a guideline for designing better high-performance wideband TR MIMO communication systems. Project supported by the National Natural Science Foundation of China (Grant Nos. 61331007, 61361166008, and 61401065) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120185130001).

  15. [The Emerging Voices for Global Health Initiative: an intensive capacity-building effort for young researchers from the South].

    Science.gov (United States)

    Hercot, D; Keugoung, B; Zerbo, A; Appelmans, A; Van Damme, W

    2012-01-01

    Researchers from developing countries, French-speaking nations in particular, are underrepresented in the international biomedical and health literature. Various initiatives seek to address this problem. This article presents the experience of the Emerging Voices for Global Health (EV4GH) program. This initiative provided 52 young researchers from developing countries with intensive skills and content training, with an assortment of complementary components: training in scientific writing and presenting skills, immersion in global health and health systems research, an innovative presentation of their work at the 52nd colloquium of the Institute of Tropical Medicine in Antwerp, and an active role in the first Global Symposium on Health Systems Research, supervised by a team of experienced researchers/coaches who supported them in the publication of a scientific essay. This approach targeting researchers in developing countries and combining the development of skills and knowledge through the publication process, merits reproduction and encouragement. Young researchers from developing countries should not miss out on the second version of this program in October 2012 in Beijing, China.

  16. Vegetative impacts upon bedload transport capacity and channel stability for differing alluvial planforms in the Yellow River source zone

    Science.gov (United States)

    Li, Zhi Wei; Yu, Guo An; Brierley, Gary; Wang, Zhao Yin

    2016-07-01

    The influence of vegetation upon bedload transport and channel morphodynamics is examined along a channel stability gradient ranging from meandering to anabranching to anabranching-braided to fully braided planform conditions along trunk and tributary reaches of the Upper Yellow River in western China. Although the regional geology and climate are relatively consistent across the study area, there is a distinct gradient in the presence and abundance of riparian vegetation for these reaches atop the Qinghai-Tibet Plateau (elevations in the study area range from 2800 to 3400 m a.s.l.). To date, the influence of vegetative impacts upon channel planform and bedload transport capacity of alluvial reaches of the Upper Yellow River remains unclear because of a lack of hydrological and field data. In this region, the types and pattern of riparian vegetation vary with planform type as follows: trees exert the strongest influence in the anabranching reach, the meandering reach flows through meadow vegetation, the anabranching-braided reach has a grass, herb, and sparse shrub cover, and the braided reach has no riparian vegetation. A non-linear relation between vegetative cover on the valley floor and bedload transport capacity is evident, wherein bedload transport capacity is the highest for the anabranching reach, roughly followed by the anabranching-braided, braided, and meandering reaches. The relationship between the bedload transport capacity of a reach and sediment supply from upstream exerts a significant influence upon channel stability. Bedload transport capacity during the flood season (June-September) in the braided reach is much less than the rate of sediment supply, inducing bed aggradation and dynamic channel adjustments. Rates of channel adjustment are less pronounced for the anabranching-braided and anabranching reaches, while the meandering reach is relatively stable (i.e., this is a passive meandering reach).

  17. Unified Importance Sampling Schemes for Efficient Simulation of Outage Capacity over Generalized Fading Channels

    KAUST Repository

    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.

  18. A novel ergodic capacity analysis of diversity combining and multihop transmission systems over generalized composite fading channels

    KAUST Repository

    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.

  19. On the computation of the higher order statistics of the channel capacity for amplify-and-forward multihop transmission

    KAUST Repository

    Yilmaz, Ferkan

    2014-01-01

    Higher order statistics (HOS) of the channel capacity provide useful information regarding the level of reliability of signal transmission at a particular rate. In this paper, we propose a novel and unified analysis, which is based on the moment-generating function (MGF) approach, to efficiently and accurately compute the HOS of the channel capacity for amplify-and-forward (AF) multihop transmission over generalized fading channels. More precisely, our easy-to-use and tractable mathematical formalism requires only the reciprocal MGFs of the transmission hop signal-to-noise ratio (SNR). Numerical and simulation results, which are performed to exemplify the usefulness of the proposed MGF-based analysis, are shown to be in perfect agreement. © 2013 IEEE.

  20. Upper Bounds on the Capacity of Binary Channels with Causal Adversaries

    CERN Document Server

    Dey, Bikash Kumar; Langberg, Michael; Sarwate, Anand D

    2012-01-01

    In this work we consider the communication of information in the presence of a causal adversarial jammer. In the setting under study, a sender wishes to communicate a message to a receiver by transmitting a codeword $\\mathbf{x}=(x_1,...,x_n)$ bit-by-bit over a communication channel. The sender and receiver do not share common randomness. The adversarial jammer can view the transmitted bits $x_i$ one at a time, and can change up to a $p$-fraction of them. However, the decisions of the jammer must be made in a causal manner. Namely, for each bit $x_i$ the jammer's decision on whether to corrupt it or not (and on how to change it) must depend only on $x_j$ for $j \\leq i$. This is in contrast to the "classical" adversarial jamming situations in which the jammer has no knowledge of $\\mathbf{x}$ or complete knowledge of $\\mathbf{x}$. In this work, we present upper bounds on the capacity which hold for both deterministic and stochastic encoding schemes.

  1. An Orbital Angular Momentum (OAM) Mode Reconfigurable Antenna for Channel Capacity Improvement and Digital Data Encoding.

    Science.gov (United States)

    Liu, Baiyang; Lin, Guoying; Cui, Yuehui; Li, RongLin

    2017-08-29

    For purpose of utilizing orbital angular momentum (OAM) mode diversity, multiple OAM beams should be generated preferably by a single antenna. In this paper, an OAM mode reconfigurable antenna is proposed. Different from the existed OAM antennas with multiple ports for multiple OAM modes transmitting, the proposed antenna with only a single port, but it can be used to transmit mode 1 or mode -1 OAM beams arbitrary by controlling the PIN diodes on the feeding network through a programmable microcontroller which control by a remote controller. Simulation and measurement results such as return loss, near-field and far-field radiation patterns of two operating states for mode 1 and mode -1, and OAM mode orthogonality are given. The proposed antenna can serve as a candidate for utilizing OAM diversity, namely phase diversity to increase channel capacity at 2.4 GHz. Moreover, an OAM-mode based encoding method is experimentally carried out by the proposed OAM mode reconfigurable antenna, the digital data are encoded and decoded by different OAM modes. At the transmitter, the proposed OAM mode reconfigurable antenna is used to encode the digital data, data symbol 0 and 1 are mapped to OAM mode 1 and mode -1, respectively. At the receiver, the data symbols are decoded by phase gradient method.

  2. From Multi-Keyholes to Measure of Correlation and Power Imbalance in MIMO Channels: Outage Capacity Analysis

    CERN Document Server

    Levin, George

    2008-01-01

    An information-theoretic analysis of a multi-keyhole channel, which includes a number of statistically independent keyholes with possibly different correlation matrices, is given. When the number of keyholes or/and the number of Tx/Rx antennas is large, there is an equivalent Rayleigh-fading channel such that the outage capacities of both channels are asymptotically equal. In the case of a large number of antennas and for a broad class of fading distributions, the outage capacity is shown to be asymptotically Gaussian in distribution, and compact, closed-form expressions for the mean and variance are given. Motivated by the asymptotic analysis, a simple, full-ordering scalar measure of spatial correlation and power imbalance in MIMO channels is introduced, which quantifies the negative impact of these two factors on the outage capacity in a simple and well-tractable way. It does not require the eigenvalue decomposition, and has the full-ordering property. The size-asymptotic results are used to prove Telatar'...

  3. Voice Disorders

    Science.gov (United States)

    Voice is the sound made by air passing from your lungs through your larynx, or voice box. In your larynx are your vocal cords, ... to make sound. For most of us, our voices play a big part in who we are, ...

  4. Every Voice

    Science.gov (United States)

    Patrick, Penny

    2008-01-01

    This article discusses how the author develops an approach that allows her students, who are part of the marginalized population, to learn the power of their own voices--not just their writing voices, but their oral voices as well. The author calls it "TWIST": Thoughts, Writing folder, Inquiring mind, Supplies, and Teamwork. It is where…

  5. Every Voice

    Science.gov (United States)

    Patrick, Penny

    2008-01-01

    This article discusses how the author develops an approach that allows her students, who are part of the marginalized population, to learn the power of their own voices--not just their writing voices, but their oral voices as well. The author calls it "TWIST": Thoughts, Writing folder, Inquiring mind, Supplies, and Teamwork. It is where…

  6. Voice restoration

    NARCIS (Netherlands)

    Hilgers, F.J.M.; Balm, A.J.M.; van den Brekel, M.W.M.; Tan, I.B.; Remacle, M.; Eckel, H.E.

    2010-01-01

    Surgical prosthetic voice restoration is the best possible option for patients to regain oral communication after total laryngectomy. It is considered to be the present "gold standard" for voice rehabilitation of laryngectomized individuals. Surgical prosthetic voice restoration, in essence, is alwa

  7. Channel capacity of TDD-OFDM-MIMO for multiple access points in a wireless single-frequency-network

    DEFF Research Database (Denmark)

    Takatori, Y.; Fitzek, Frank; Tsunekawa, K.

    2005-01-01

    The multiple-input-multiple-output (MIMO) technique is the most attractive candidate to improve the spectrum efficiency in the next generation wireless communication systems. However, the efficiency of MIMO techniques reduces in the line of sight (LOS) environments. In this paper, we propose a new...... MIMO data transmission scheme, which combines Single-Frequency-Network (SFN) with TDD-OFDM-MIMO applied for wireless LAN networks. In our proposal, we advocate to use SFN for multiple access points (MAP) MIMO data transmission. The goal of this approach is to achieve very high channel capacity in both...... LOS and non line of sight (NLOS) environments. The channel capacity of the proposed method is derived for the direct path environments and it confirms the effectiveness of the proposed scheme in the LOS scenario. Moreover, solid computer simulation results confirm the effectiveness of the proposed...

  8. A Lower Bound on the Capacity of the Noncentral Chi Channel with Applications to Soliton Amplitude Modulation

    CERN Document Server

    Shevchenko, Nikita A; Prilepsky, Jaroslaw E; Alvarado, Alex; Bayvel, Polina; Turitsyn, Sergei K

    2016-01-01

    The channel law for amplitude-modulated solitons transmitted through a nonlinear optical fibre with ideal distributed amplification and a receiver based on the nonlinear Fourier transform is a noncentral chi distribution with $2n$ degrees of freedom, where $n=2$ and $n=3$ correspond to the single- and dual-polarisation cases, respectively. In this paper, we study the capacity of this channel in bits per channel use, and develop a semi-analytic capacity lower bound for arbitrary $n$ and a Rayleigh input distribution. An asymptotic analysis of the bound is also presented, which shows that this lower bound grows logarithmically with signal-to-noise ratio (SNR), independently of the value of $n$. Numerical results for other input distributions are also provided. A half-Gaussian input distribution is shown to give larger rates than a Rayleigh input distribution for $n=1,2,3$. At an effective SNR of 30~dB, the obtained lower bounds are approximately 4 bit per channel use.

  9. Above the threshold for motion: erosion rates recorded in the bedload transport capacity of West Coast channels?

    Science.gov (United States)

    Pfeiffer, A.; Finnegan, N. J.; Willenbring, J. K.

    2015-12-01

    Gravel-bedded river channels commonly evolve so that median sized grains on the bed surface are at, or near, the threshold for motion when the flow reaches bankfull stage. In addition, theory predicts the near- equivalence of the bankfull (bf) and critical (c) non-dimensional shear stresses (τ*bf ~= τ*c) for straight, cohesionless gravel channels. However, not all natural gravel channels conform to this simple relationship. To understand why some channels maintain bankfull stresses far in excess of what is needed to initiate sediment motion, we compile a dataset of the hydraulic geometry and median grain sizes of ~300 reaches from gravel-bedded rivers in North America. Notably, we find that the ratio of bankfull to critical Shields stresses is significantly higher in West Coast river reaches (2.6, n=77) than in river reaches in the rest of the continent (1.0, n=216). We explore the hypothesis that these reaches have adjusted to maintain a high excess shear stress at bankfull flows to accommodate elevated sediment supplies resulting from rapid erosion along the tectonically active margin of western North America. As a test of this hypothesis, we explore spatial patterns in calculated transport capacity and 10Be-derived erosion rates across North America. We find that an order of magnitude decrease in sediment transport capacity away from the Pacific plate boundary parallels an order of magnitude decrease in 10Be-derived erosion rates. These findings suggest that tectonically sustained high erosion rates on the West Coast may be recorded in the channel geometry and bed surface grain size of gravel-bedded channels.

  10. Ergodic capacity of switch-and-examine combining under flat Rayleigh fading channels

    Institute of Scientific and Technical Information of China (English)

    ZHAO Shuang; YAO Wen-bin; YANG Hong-wen; WANG Ya-feng

    2009-01-01

    Switch-and-examine combining (SEC) is an interesting diversity technique that is simpler than selection combining (SC), whereas its performances is similar in terms of bit error rate (BER) and diversity order. As ergodic capacity is also a key performance index in modern wireless systems, this article analyzes the ergodic capacity of the SEC system. The numerical results show that the ergodic capacity of SEC with optimal threshold is similar to that of SC for arbitrary number of diversity branches.

  11. Discharge capacity of sluiceway channel of water intake structure for diversion power plant in winter

    Directory of Open Access Journals (Sweden)

    N.P. Lavrov

    2013-06-01

    Full Text Available The paper presents results of research hydraulic processes at the intake structures of diversion power plants in winter. On the basis of the physical modeling results the flow characteristics of sluiceway channel of water intake on the river Issyk-Ata, Kyrgyzstan were determined. Statistical models of discharges of elements of sluiceway channel with their mutual influence were obtained, using the methods of experimental design and data analysis. The influence of the concentration of brash ice on the sluiceway channel and its elements is described. The comparison of experimental data with data obtained by other authors before is made by comparing flow coefficients. Recommendations for normal operation of ice pass at sluiceway track channel of water intake structure for diversion power plant are given.

  12. On the Capacity of Interference Channel with Causal and Non-causal Generalized Feedback at the Cognitive Transmitter

    CERN Document Server

    Mirmohseni, Mahtab; Aref, Mohammad Reza

    2012-01-01

    In this paper, taking into account the effect of link delays, we investigate the capacity region of the Cognitive Interference Channel (C-IFC), where cognition can be obtained from either causal or non-causal generalized feedback. For this purpose, we introduce the Causal Cognitive Interference Channel With Delay (CC-IFC-WD) in which the cognitive user's transmission can depend on $L$ future received symbols as well as the past ones. We show that the CC-IFC-WD model is equivalent to a classical Causal C-IFC (CC-IFC) with link delays. Moreover, CC-IFC-WD extends both genie-aided and causal cognitive radio channels and bridges the gap between them. First, we derive an outer bound on the capacity region for the arbitrary value of $L$ and specialize this general outer bound to the strong interference case. Then, under strong interference conditions, we tighten the outer bound. To derive the achievable rate regions, we concentrate on three special cases: 1) Classical CC-IFC (L=0), 2) CC-IFC without delay (L=1), an...

  13. Evaluation of PLC Channel Capacity and ABER Performances for OFDM-Based Two-Hop Relaying Transmission

    Directory of Open Access Journals (Sweden)

    Sana Ezzine

    2017-01-01

    Full Text Available Powerline network is recognized as a favorable infrastructure for Smart Grid to transmit information in the network thanks to its broad coverage and low cost deployment. The existing works are trying to improve and adapt transmission techniques to reduce Powerline Communication (PLC channel attenuation and exploit the limited bandwidth to support high data rate over long distances. Two-hop relaying BroadBand PLC (BB-PLC system, in which Orthogonal Frequency Division Multiplexing (OFDM is used, is considered in this paper. We derive and compare the PLC channel capacity and the end-to-end Average BER (ABER for OFDM-based direct link (DL BB-PLC system and for OFDM-based two-hop relaying BB-PLC system for Amplify and Forward (AF and Decode and Forward (DF protocols. We analyze the improvements when we consider the direct link in a cooperative communication when the relay node only transmits the correctly decoded signal. Maximum ratio combining is employed at the destination node to detect the transmitted signal. In addition, in this paper, we highlight the impact of the relay location on the channel capacity and ABER for AF and DF transmission protocols. Moreover, an efficient use of the direct link was also investigated in this paper.

  14. PKC enhances the capacity for secretion by rapidly recruiting covert voltage-gated Ca2+ channels to the membrane.

    Science.gov (United States)

    Groten, Christopher J; Magoski, Neil S

    2015-02-11

    It is unknown whether neurons can dynamically control the capacity for secretion by promptly changing the number of plasma membrane voltage-gated Ca(2+) channels. To address this, we studied peptide release from the bag cell neurons of Aplysia californica, which initiate reproduction by secreting hormone during an afterdischarge. This burst engages protein kinase C (PKC) to trigger the insertion of a covert Ca(2+) channel, Apl Cav2, alongside a basal channel, Apl Cav1. The significance of Apl Cav2 recruitment to secretion remains undetermined; therefore, we used capacitance tracking to assay secretion, along with Ca(2+) imaging and Ca(2+) current measurements, from cultured bag cell neurons under whole-cell voltage-clamp. Activating PKC with the phorbol ester, PMA, enhanced Ca(2+) entry, and potentiated stimulus-evoked secretion. This relied on channel insertion, as it was occluded by preventing Apl Cav2 engagement with prior whole-cell dialysis or the cytoskeletal toxin, latrunculin B. Channel insertion reduced the stimulus duration and/or frequency required to initiate secretion and strengthened excitation-secretion coupling, indicating that Apl Cav2 accesses peptide release more readily than Apl Cav1. The coupling of Apl Cav2 to secretion also changed with behavioral state, as Apl Cav2 failed to evoke secretion in silent neurons from reproductively inactive animals. Finally, PKC also acted secondarily to enhance prolonged exocytosis triggered by mitochondrial Ca(2+) release. Collectively, our results suggest that bag cell neurons dynamically elevate Ca(2+) channel abundance in the membrane to ensure adequate secretion during the afterdischarge.

  15. A Capacity Improvement Method for CDMA based Mesh Networks in SUI Multipath Fading Channels

    CERN Document Server

    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.

  16. MIMO channel capacity versus mutual coupling in multi antenna element system

    DEFF Research Database (Denmark)

    Thaysen, Jesper; Jakobsen, Kaj Bjarne

    2004-01-01

    capacity, configurations with the lowest envelope correlations are not necessarily the most suitable for a MIMO system. A certain bandwidth is required as well. Three planar inverted F-antennas (PIFA) located on the same 40 mm x 100 mm ground plane. The antennas that haves a resonant frequency of 1.8 GHz......In this paper the influence of mutual coupling on the capacity of a multiple-input multiple-output (MIMO) antenna system is demonstrated. No direct relation between the envelope correlation and the actual location and orientation of the antennas is found. Even though being essential for high MIMO...

  17. BER Analysis to Increase Capacity of A Cellular System Using SDMA Over a Multipath Rayleigh Fading Channel

    Directory of Open Access Journals (Sweden)

    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.

  18. Extending MIL-STD-1553 bandwidth: a study of impairments, EMI, and channel capacity

    Science.gov (United States)

    Hegarty, Michael G.

    2004-09-01

    This paper explores the possibility of increasing the data rates on existing MIL-STD-1553 networks beyond its current one megabit per second rate. A combination of empirical and theoretical methods is used in predicting the capacity of a MIL-STD-1553 network. The analysis begins with an assessment of the usable bandwidth in a 1553 network followed by the development of models to predict signal-to-noise ratios based on a transmit signal level that meets the emissions limits of MIL-STD-461 and a noise level that is representative of a real 1553 system. This paper presents the theoretical capacity limits for several 1553 network configurations. The results of the analysis predict that the theoretical capacity within a legacy MIL-STD-1553 system is expected to be several hundred megabits per second. The achievable rate depends on network configuration and usable bandwidth. Methods of approaching these theoretical capacity limits is not discussed in this paper, rather, this paper provides a framework and a baseline for the analysis of higher data rates over legacy MIL-STD-1553 networks.

  19. Rock Island Arsenal Power Dam: Numerical Hydraulic Model Investigation of Channel Capacity for Power Generation

    Science.gov (United States)

    2016-06-01

    behavior. The work was performed by the River Engineering Branch (CEERD-HFR) of the Flood and Storm Protection Division (CEERD-HF), U.S. Army...channels of the two powerhouse structures and define the effects increased hydropower releases might have on stages and flow distribution within the...junctions and changes in flow distribution around islands and structures induced by varying prescribed hydropower releases. The primary limitation

  20. Through the looking glass: self-reassuring meta-cognitive capacityand its relationship with the thematic content of voicesand nature of the voice/voice-hearer relationship

    Directory of Open Access Journals (Sweden)

    Charlotte eConnor

    2013-05-01

    Full Text Available AbstractAimsTo examine the self-critical thoughts and self-reassuring meta-cognitive capacity of those who hear voices and explore whether they are associated with the theme of voice content and appraisals of voice power and voice expressed emotion. MethodA cross-sectional design was used, combining semi-structured interviews and self-report measures. Data on symptomatology, self-critical thoughts and self-reassuring meta-cognitive capacity, thematic voice content and appraisals of voice power and expressed emotion were collected from 74 voice-hearers in Birmingham, UK. Results Common themes of voice content reflected issues of shame, control and affiliation. Controlling content was the most prevalent theme, however, no significant predictor of this theme was found; shaming thematic voice content linked with reduced capacity to self-reassure following self-critical thoughts. Voice-hearers with the greatest level of self-critical thoughts appraised their voices as powerful and high in voice expressed emotion ConclusionsFindings suggest that voice-hearers self-critical thoughts are reflected in the type of relationship they have with their voice. However, access to self-reassuring meta-cognitive capacity may serve as a protective factor for those who hear voices, resulting in more benign voice content. These findings highlight the importance of this specific meta-cognitive capacity and will inform future therapeutic interventions for the management of voices in this vulnerable group.

  1. Optical Channel Capacity Upgrade Based on Multiwavelength Conversion XGM Using Semiconductor Optical Amplifier for Access Networks

    Directory of Open Access Journals (Sweden)

    Mohammad Syuhaimi Ab-rahman

    2017-01-01

    Full Text Available This paper demonstrates a 10 Gb/s one-to-two-wavelength conversion configuration based on cross-gain modulation for optical access networks using a single TW-SOA. The method is capable of converting a signal data of specific wavelength 1541 nm to certain wavelengths of CW’s laser 1554 nm and 1558 nm with 4 nm spacing. The pump power level was classified due to channel response. A result obtained was the best power level offering wavelength converter between −6 and 3 dBm. The conversion efficiency achievement provided an acceptable result for probe signals. The findings of Q-factor performance were investigated. The Q values were found to be more than 9 for point to point transmission and 20 km fiber configurations for the original and converted signal. The technique implemented at 20 km and the power of all channels were adequate to provide a splitting ratio of 1/64 for the launched pump power 3 dBm.

  2. Sum-capacity of Interference Channels with a Local View: Impact of Distributed Decisions

    CERN Document Server

    Aggarwal, Vaneet; Sabharwal, Ashutosh

    2009-01-01

    Due to the large size of wireless networks, it is often impractical for nodes to track changes in the complete network state. As a result, nodes have to make distributed decisions about their transmission and reception parameters based on their local view of the network. In this paper, we characterize the impact of distributed decisions on the global network performance in terms of achievable sum-rates. We first formalize the concept of local view by proposing a protocol abstraction using the concept of local message passing. In the proposed protocol, nodes forward information about the network state to other neighboring nodes, thereby allowing network state information to trickle to all the nodes. The protocol proceeds in rounds, where all transmitters send a message followed by a message by all receivers. The number of rounds then provides a natural metric to quantify the extent of local information at each node. We next study three network connectivities, Z-channel, a three-user double Z-channel and a redu...

  3. Demonstration of 5.1 Tbit/s data capacity on a single-wavelength channel

    OpenAIRE

    Mulvad, Hans Christian Hansen; Galili, Michael; Oxenløwe, Leif Katsuo; Hu, Hao; Clausen, Anders; Jensen, Jesper Bevensee; Peucheret, Christophe; Jeppesen, Palle

    2010-01-01

    We have generated a single-wavelength data signal with a data capacity of 5.1 Tbit/s. The enabling techniques to generate the data signal are optical time-division multiplexing up to a symbol rate of 1.28 Tbaud, differential quadrature phase shift keying as data format, and polarisation-multiplexing. For the first time, error-free performance with a bit error rate less than 1e-9 is demonstrated for the 5.1 Tbit/s data signal. This is achieved in a back-to-back configuration using a direct det...

  4. High Capacity Phase/Amplitude Modulated Optical Communication Systems and Nonlinear Inter-Channel Impairments

    Science.gov (United States)

    Tavassoli, Vahid

    This thesis studies and mathematically models nonlinear interactions among channels of modern high bit rate (amplitude/) phase modulated optical systems. First, phase modulated analogue systems are studied and a differential receiving method is suggested with experimental validation. The main focus of the rest of the thesis is on digital advanced modulation format systems. Cross-talk due to fiber Kerr nonlinearity in two-format hybrid systems as well as 16-QAM systems is mathematically modelled and verified by simulation for different system parameters. A comparative study of differential receivers and coherent receivers is also given for hybrid systems. The model is based on mathematically proven assumptions and provides an intuitive analytical understanding of nonlinear cross-talk in such systems.

  5. On the outage capacity of the block fading channel at low-power regime

    KAUST Repository

    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.

  6. Communication in a Poisson Field of Interferers -- Part II: Channel Capacity and Interference Spectrum

    CERN Document Server

    Pinto, Pedro C

    2010-01-01

    In Part I of this paper, we presented a mathematical model for communication subject to both network interference and noise, where the interferers are scattered according to a spatial Poisson process, and are operating asynchronously in a wireless environment subject to path loss, shadowing, and multipath fading. We determined the distribution of the aggregate interference and the error performance of the link. In this second part, we characterize the capacity of the link subject to both network interference and noise. Then, we put forth the concept of spectral outage probability (SOP), a new characterization of the aggregate radio-frequency emission generated by communicating nodes in a wireless network. We present some applications of the SOP, namely the establishment of spectral regulations and the design of covert military networks. The proposed framework captures all the essential physical parameters that affect the aggregate network emission, yet is simple enough to provide insights that may be of value...

  7. Channel Models for Capacity Evaluation of MIMO Handsets in Data Mode

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ødum; Yanakiev, Boyan; Barrio, Samantha Caporal Del;

    2017-01-01

    This work investigates different correlation based models useful for evaluation of outage capacity (OC) of mobile multiple-input multiple-output (MIMO) handsets. The work is based on a large measurement campaign in a micro-cellular setup involving two dual-band base stations, 10 different handsets...... in an indoor environment for different use cases and test users. Several models are evaluated statistically, comparing the OC values estimated from the model and measurement data, respectively, for about 2,700 measurement routes. The models are based on either estimates of the full correlation matrices...... or simplifications. Among other results, it is shown that the OC can be predicted accurately (median error typically within 2.6%) with a model assuming knowledge only of the Tx-correlation coefficient and the mean power gain....

  8. Demonstration of 5.1 Tbit/s data capacity on a single-wavelength channel.

    Science.gov (United States)

    Hansen Mulvad, Hans Christian; Galili, Michael; Oxenløwe, Leif K; Hu, Hao; Clausen, Anders T; Jensen, Jesper B; Peucheret, Christophe; Jeppesen, Palle

    2010-01-18

    We have generated a single-wavelength data signal with a data capacity of 5.1 Tbit/s. The enabling techniques to generate the data signal are optical time-division multiplexing up to a symbol rate of 1.28 Tbaud, differential quadrature phase shift keying as data format, and polarisation-multiplexing. For the first time, error-free performance with a bit error rate less than 10(-9) is demonstrated for the 5.1 Tbit/s data signal. This is achieved in a back-to-back configuration using a direct detection receiver based on polarisation- and time-demultiplexing, delay-demodulation and balanced photo-detection.

  9. A novel unified expression for the capacity and bit error probability of wireless communication systems over generalized fading channels

    KAUST Repository

    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.

  10. Estimation of Outage Capacity for Free Space Optical Links Over I-K and K Turbulent Channels

    Directory of Open Access Journals (Sweden)

    D. Marinos

    2011-06-01

    Full Text Available The free space optical communication systems are attracting great research and commercial interest due to their capability of transferring data, over short distances, with high rate and security, low cost demands and without licensing fees. However, their performance depends strongly on the atmospheric conditions in the link’s area. In this work, we investigate the influence of the turbulence on the outage capacity of such a system for weak to strong turbulence channels modeled by the I-K and the K-distribution and we derive closed-form expressions for its estimation. Finally, using these expressions we present numerical results for various link cases with different turbulence conditions.

  11. Research and Implement on the Driver of Multi-channel Voice Device under Linux%Linux下多通道话音采集压缩卡的驱动研究与实现

    Institute of Scientific and Technical Information of China (English)

    翟永久

    2011-01-01

    Device driver in the Linux kernel plays an important role,which is responsible for the mapped of the actual hardware-specific operations.To achieve the real-time multi-channel voice data collection in Linux of simultaneous multi-channel digital recorder, we proposed multi-channel voice capture and compression card driver design,described the initialization of the device driver, Finally we analyzed the stability and real-time of the driver in Linux.%设备驱动程序在Linux内核中占有重要的地位,它是负责实际硬件设备的特定操作的映射。为了实现多通道同步数字记录仪在Linux下对多通道话音数据的实时采集,给出了多通道话音采集压缩卡的驱动程序的设计,描述了驱动程序的初始化过程,提高了系统的可靠性。最后分析了驱动程序的稳定性与实时性。

  12. Keeping Your Voice Healthy

    Science.gov (United States)

    ... Find an ENT Doctor Near You Keeping Your Voice Healthy Keeping Your Voice Healthy Patient Health Information ... heavily voice-related. Key Steps for Keeping Your Voice Healthy Drink plenty of water. Moisture is good ...

  13. Ergodic channel capacity of spatial correlated multiple-input multiple-output free space optical links using multipulse pulse-position modulation

    Science.gov (United States)

    Wang, Huiqin; Wang, Xue; Cao, Minghua

    2017-02-01

    The spatial correlation extensively exists in the multiple-input multiple-output (MIMO) free space optical (FSO) communication systems due to the channel fading and the antenna space limitation. Wilkinson's method was utilized to investigate the impact of spatial correlation on the MIMO FSO communication system employing multipulse pulse-position modulation. Simulation results show that the existence of spatial correlation reduces the ergodic channel capacity, and the reception diversity is more competent to resist this kind of performance degradation.

  14. Voice communications over packet radio networks

    Science.gov (United States)

    Seah, M. M.

    1985-03-01

    The use of packet virtual circuit technique for voice communications in military radio networks was investigated. The work was concerned with various aspects of networking which include network modeling, communications techniques, traffic analysis and network control. An attempt has been made to develop a simple yet efficient time slot assignment algorithm . This was analyzed under a variety of slot depths and networks topologies using computer simulation. The Erlang' B results were used to provide more insight into the channel characteristics of the packet radio networks. The capabilities of implementing TDMA/CDMA hybrid schemes in the system were scrutinized. A method to estimate the transmission capacity of the inter-node links was found. We demonstrate its effectiveness in controlling local congestion by computer simulation. Graphical results were presented to highlight the behavior of the proposed packet radio networks. We concluded that an appropriate link weight function would provide efficient and reliable network services.

  15. 分布式MIMO系统的复合信道容量分析%Capacity analysis of compound channel for distributed MIMO system

    Institute of Scientific and Technical Information of China (English)

    刘伟; 汪清

    2013-01-01

    Distributed MIMO system combines the characteristics of MIMO channel and distributed antenna system, which is believed a very promising technology in the future of 4G, because of its large capacity, large coverage and less power loss from shadow and distance. A compound channel model considering path loss, lognormal shadow fading and small scale fading for distributed MIMO system model is adopted, the capacity of which is analyzed. Besides channel capacity between distributed MIMO system and centralized MIMO system is compared by Monte Carlo simulations. At the same time, the impact of spatial fading correlation and path loss on the capacity is also investigated. The simulation results prove that distributed MIMO system can effectually reduce the impact of small scale fading, and achieve a better channel capacity.%分布式MIMO系统结合了MIMO技术和分布式天线系统两者的特点,具有高容量、大覆盖范围、低损耗的优势,在未来4G通信中具有很好的应用前景.基于包含了路径损耗、阴影衰落和相关小尺度衰落的分布式MIMO信道模型,通过Monte Carlo仿真比较分析了分布式MIMO系统和集中式MIMO系统的信道容量,研究了空间相关性和路径损耗对信道容量的影响.仿真实验结果表明,分布式MIMO系统能有效降低小尺度衰落相关性的影响,可以获得更好的平均信道容量.

  16. The Praxis of Building Capacity in Mathematics and Science in a Rural, Non-Government Systems of Schools: Voices of Teacher Leaders

    Science.gov (United States)

    Connor, Vince; Auld, Billinda; Eakin, Patricia; Morris, Kerry; Tilston, Michael

    2010-01-01

    Much is written about teacher leaders and the impact they have in promoting and influencing change. This is a reflection from four teacher leaders from four secondary high schools of a rural, non-government system of schools as they seek to build a capacity in the learning and teaching of mathematics and science within their schools. The original…

  17. LabVIEW in Design of a Two-channel Voice Recording System%基于LabVIEW的双声道语音录制系统的设计

    Institute of Scientific and Technical Information of China (English)

    智耕

    2012-01-01

    本文论述了一款双声道语音录制系统的组成及开发过程,该系统利用LabVIEW进行设计,采用计算机声卡代替专用数据采集卡,实现语音信号的录制、显示、存储等功能,具有广阔的应用前景。%This paper discusses components and development process of a two-channel voice recording system, using LabVIEW and computer's sound card instead of a special DAC. This method could achieve functions of recording, displaying and saving signal data, enjoying broad application prospects.

  18. LabVIEW in Design of a Two-channel Voice Recording System%基于LabVIEW的双声道语音录制系统的设计

    Institute of Scientific and Technical Information of China (English)

    智耕

    2012-01-01

    本文论述了一款双声道语音录制系统的组成及开发过程,该系统利用LabVIEW进行设计,采用计算机声卡代替专用数据采集卡,实现语音信号的录制、显示、存储等功能,具有广阔的应用前景。%This paper discusses components and development process of a two-channel voice recording system,using LabVIEW and computer's sound card instead of a special DAC.This method could achieve functions of recording,displaying and saving signal data,enjoying broad application prospects.

  19. Modelling the flooding capacity of a Polish Carpathian river: A comparison of constrained and free channel conditions

    Science.gov (United States)

    Czech, Wiktoria; Radecki-Pawlik, Artur; Wyżga, Bartłomiej; Hajdukiewicz, Hanna

    2016-11-01

    The gravel-bed Biała River, Polish Carpathians, was heavily affected by channelization and channel incision in the twentieth century. Not only were these impacts detrimental to the ecological state of the river, but they also adversely modified the conditions of floodwater retention and flood wave passage. Therefore, a few years ago an erodible corridor was delimited in two sections of the Biała to enable restoration of the river. In these sections, short, channelized reaches located in the vicinity of bridges alternate with longer, unmanaged channel reaches, which either avoided channelization or in which the channel has widened after the channelization scheme ceased to be maintained. Effects of these alternating channel morphologies on the conditions for flood flows were investigated in a study of 10 pairs of neighbouring river cross sections with constrained and freely developed morphology. Discharges of particular recurrence intervals were determined for each cross section using an empirical formula. The morphology of the cross sections together with data about channel slope and roughness of particular parts of the cross sections were used as input data to the hydraulic modelling performed with the one-dimensional steady-flow HEC-RAS software. The results indicated that freely developed cross sections, usually with multithread morphology, are typified by significantly lower water depth but larger width and cross-sectional flow area at particular discharges than single-thread, channelized cross sections. They also exhibit significantly lower average flow velocity, unit stream power, and bed shear stress. The pattern of differences in the hydraulic parameters of flood flows apparent between the two types of river cross sections varies with the discharges of different frequency, and the contrasts in hydraulic parameters between unmanaged and channelized cross sections are most pronounced at low-frequency, high-magnitude floods. However, because of the deep

  20. On the Model and Capacity of MIMO Underwater Acoustic Channels (UWACs)%水声MIMO信道模型和容量分析

    Institute of Scientific and Technical Information of China (English)

    张歆; 张小蓟; 乔宏乐

    2011-01-01

    水声通信系统对数据率的更高要求提出了水声信道容量限的问题.信息理论的研究表明,采用多输入多输出(MIMO)结构具有改善信道容量的潜力.文章对MIMO水声信道模型及信道容量进行了研究.借助于瑞利衰落统计模型和射线模型,建立了时变的MIMO水声信道模型,分析了多径时延以及发射、接收阵元数对时变水声信道容量的影响.文中还基于湖试信道测量数据,给出了信道的功率延迟线和不同信道的中断容量结果.仿真和测量的结果表明,相比单输入单输出(SISO)信道,MIMO水声信道可以获得明显的容量改善;而且相比平坦衰落信道,多径MIMO水声信道可以获得更大的容量增益.%The growing need for higher data rates poses the problem of capacity limit of UWACs.Past research has demonstrated a potentially huge gain of capacity in multiple input multiple output (MIMO) systems.In order to realize a part of this huge gain, we deal with the model of MIMO UWACs and the capacity of MIMO UWACs; sections 1,2, and 3 explain our method for realizing an obvious gain.Sections 1 and 2 brief respectively the model and capacity of MIMO channel.The core of section 3 is that, introducing a physically motivated Rayleigh fading MIMO UWAC model, it gives Tables 1 and 2 that give the values of the channel parameters needed in numerical simulation.Section 4 applies our method to the numerical simulation of the capacities respectively of two specific channels; it studies the influence of physical parameters such as multipath spread and system parameters such as the number of sensors for both ergodic capacity and outage capacity; Figs.1 and 2 give the results of numerical simulation.Section 5 describes the lake channel measurements; the power delay curves are given in Fig.3 and outage capacity results in Fig.4 from these measurements are discussed for different channels.Numerical and lake measurement results demonstrate preliminarily that

  1. Covert channel capacity analysis based on information entropy%基于信息熵的隐通道能力分析

    Institute of Scientific and Technical Information of China (English)

    陈立; 鞠时光; 周从华; 房芳; 张翼

    2009-01-01

    This paper presented a method based on information entropy to analyze the capacity of covert channels. Built upon noninterference, the method was firstly used to calculate the covert channel capacity, then to analyze the factors that had an impact on this quantity. Finally gave an example of the capacity calculation for covert channels in a multilevel secure database.%给出了一种基于信息熵的隐通道能力分析方法.该方法首先利用无干扰分析法分析隐通道,得到系统状态转换分布特性,然后引入信息熵,进而推导出隐通道能力表达公式.该方法能较好地对隐通道能力进行定量分析,不仅可以对隐通道能力的大小进行计算,还可以分析隐通道能力的影响因素.最后,给出了存在于多级安全数据库中的一种隐通道,并用该方法分析计算了该隐通道的能力.

  2. 姿态变化对无人机MIMO信道容量的影响%Effect of Attitude Change on Unmanned Aerial Vehicle MIMO Channel Capacity

    Institute of Scientific and Technical Information of China (English)

    陈登伟; 高喜俊; 许鑫; 齐伟伟

    2015-01-01

    考虑无人机多天线通信需求,在无人机上以圆阵方式布置4元天线。为分析无人机多入多出( Multi⁃Input Multi⁃Output, MIMO)通信系统,建立了统一的坐标系,并构建了基于四发两收的无人机MIMO三维GBSBCM信道模型,采用信道矩阵分解、信道系数归一化的方法,推导了无人机的MIMO平均信道相关矩阵。仿真分析了无人机姿态变化参数对无人机MIMO信道容量的影响,对合理调整无人机姿态参数来提高无人机MIMO通信容量提供理论参考。%Aiming at the demand of Unmanned Aerial Vehicle for Multi⁃Input Multi⁃Output ( UAV⁃MIMO) communication,four antennas are laid as circular array in UAV.To analyze UAV⁃MIMO communication system,the uniform coordinate is built,and also the 3D⁃GBSBCM ( Geometrically Based Single Bounce Cylinder Model) channel model of UAV⁃MIMO based on four transmitters and two receivers is constructed.The method of channel matrix factorization and channel coefficient normalization are put forward to deduce the average channel correlation matrix of UAV MIMO.At last,the effect of UAV attitude change parameters on UAV MIMO channel capacity is simulated and analyzed.The simulation results provides theory reference for improving UAV⁃MIMO system capacity by changing the attitude parameters.

  3. Speaking and Nonspeaking Voice Professionals: Who Has the Better Voice?

    Science.gov (United States)

    Chitguppi, Chandala; Raj, Anoop; Meher, Ravi; Rathore, P K

    2017-04-18

    Voice professionals can be classified into two major subgroups: the primarily speaking and the primarily nonspeaking voice professionals. Nonspeaking voice professionals mainly include singers, whereas speaking voice professionals include the rest of the voice professionals. Although both of these groups have high vocal demands, it is currently unknown whether both groups show similar voice changes after their daily voice use. Comparison of these two subgroups of voice professionals has never been done before. This study aimed to compare the speaking voice of speaking and nonspeaking voice professionals with no obvious vocal fold pathology or voice-related complaints on the day of assessment. After obtaining relevant voice-related history, voice analysis and videostroboscopy were performed in 50 speaking and 50 nonspeaking voice professionals. Speaking voice professionals showed significantly higher incidence of voice-related complaints as compared with nonspeaking voice professionals. Voice analysis revealed that most acoustic parameters including fundamental frequency, jitter percent, and harmonic-to-noise ratio were significantly higher in speaking voice professionals, whereas videostroboscopy did not show any significant difference between the two groups. This is the first study of its kind to analyze the effect of daily voice use in the two subgroups of voice professionals with no obvious vocal fold pathology. We conclude that voice professionals should not be considered as a homogeneous group. The detrimental effects of excessive voice use were observed to occur more significantly in speaking voice professionals than in nonspeaking voice professionals. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  4. Leveraging voice

    DEFF Research Database (Denmark)

    Frølunde, Lisbeth

    2017-01-01

    researchers improve our practices and how could digital online video help offer more positive stories about research and higher education? How can academics in higher education be better to tell about our research, thereby reclaiming and leveraging our voice in a post-factual era? As higher education......This paper speculates on how researchers share research without diluting our credibility and how to make strategies for the future. It also calls for consideration of new traditions and practices for communicating knowledge to a wider audience across multiple media platforms. How might we...... continues to engage with digital and networked technologies it becomes increasingly relevant to question why and how academics could (re) position research knowledge in the digital and online media landscape of today and the future. The paper highlights methodological issues that arise in relation...

  5. Feeling voices.

    Directory of Open Access Journals (Sweden)

    Paolo Ammirante

    Full Text Available Two experiments investigated deaf individuals' ability to discriminate between same-sex talkers based on vibrotactile stimulation alone. Nineteen participants made same/different judgments on pairs of utterances presented to the lower back through voice coils embedded in a conforming chair. Discrimination of stimuli matched for F0, duration, and perceived magnitude was successful for pairs of spoken sentences in Experiment 1 (median percent correct = 83% and pairs of vowel utterances in Experiment 2 (median percent correct = 75%. Greater difference in spectral tilt between "different" pairs strongly predicted their discriminability in both experiments. The current findings support the hypothesis that discrimination of complex vibrotactile stimuli involves the cortical integration of spectral information filtered through frequency-tuned skin receptors.

  6. MIMO Channel Modeling and Capacity Analysis in Terahertz Communication%太赫兹通信中MIMO信道建模与容量分析

    Institute of Scientific and Technical Information of China (English)

    李伟琨; 姚信威; 王万良; 吴腾超

    2015-01-01

    With the development of nanotechnology and the graphene-based nano materials,terahertz communication, the preferred communication technology of nano network is becoming the new hotspot for wireless communication. However,the performance of Multiple Input Multiple Output( MIMO) channel in terahertz band is still unknown. A novel MIMO channel model in terahertz communications is proposed by using a discrete mathematical method. Combining the molecular absorption and the path loss in terahertz band,a model of channel capacity is presented based on the channel state information at the receiver. MIMO channel model in terahertz communications is verified in the simulation. Result shows that the MIMO channel in terahertz communication can support higher capacity and transmission bit-rates than the single terahertz channel.%随着纳米技术的不断发展与新型纳米材料石墨烯研究的不断深入,作为纳米网络通信技术的太赫兹通信成为无线通信的研究热点,然而现阶段对太赫兹通信中多输入多输出( MIMO)机制的研究较少。为此,采用离散化的数学方法,以接收端获取信道信息的遍历容量模型为基础,结合太赫兹信道的分子吸收噪声与传输路径损失,提出一种适用于太赫兹通信的MIMO信道模型。对建立的MIMO信道模型进行仿真与分析,结果表明,与单一太赫兹信道相比,太赫兹通信中的MIMO信道具有更高的信道容量与传输比特率。

  7. A pharmacologically validated, high-capacity, functional thallium flux assay for the human Ether-à-go-go related gene potassium channel.

    Science.gov (United States)

    Schmalhofer, William A; Swensen, Andrew M; Thomas, Brande S; Felix, John P; Haedo, Rodolfo J; Solly, Kelli; Kiss, Laszlo; Kaczorowski, Gregory J; Garcia, Maria L

    2010-12-01

    The voltage-gated potassium channel, human Ether-à-go-go related gene (hERG), represents the molecular component of IKr, one of the potassium currents involved in cardiac action potential repolarization. Inhibition of IKr increases the duration of the ventricular action potential, reflected as a prolongation of the QT interval in the electrocardiogram, and increases the risk for potentially fatal ventricular arrhythmias. Because hERG is an appropriate surrogate for IKr, hERG assays that can identify potential safety liabilities of compounds during lead identification and optimization have been implemented. Although the gold standard for hERG evaluation is electrophysiology, this technique, even with the medium capacity, automated instruments that are currently available, does not meet the throughput demands for supporting typical medicinal chemistry efforts in the pharmaceutical environment. Assays that could provide reliable molecular pharmacology data, while operating in high capacity mode, are therefore desirable. In the present study, we describe a high-capacity, 384- and 1,536-well plate, functional thallium flux assay for the hERG channel that fulfills these criteria. This assay was optimized and validated using different structural classes of hERG inhibitors. An excellent correlation was found between the potency of these agents in the thallium flux assay and in electrophysiological recordings of channel activity using the QPatch automated patch platform. Extension of this study to include 991 medicinal chemistry compounds from different internal drug development programs indicated that the thallium flux assay was a good predictor of in vitro hERG activity. These data suggest that the hERG thallium flux assay can play an important role in supporting drug development efforts.

  8. Dimensionality in voice quality.

    Science.gov (United States)

    Bele, Irene Velsvik

    2007-05-01

    This study concerns speaking voice quality in a group of male teachers (n = 35) and male actors (n = 36), as the purpose was to investigate normal and supranormal voices. The goal was the development of a method of valid perceptual evaluation for normal to supranormal and resonant voices. The voices (text reading at two loudness levels) had been evaluated by 10 listeners, for 15 vocal characteristics using VA scales. In this investigation, the results of an exploratory factor analysis of the vocal characteristics used in this method are presented, reflecting four dimensions of major importance for normal and supranormal voices. Special emphasis is placed on the effects on voice quality of a change in the loudness variable, as two loudness levels are studied. Furthermore, the vocal characteristics Sonority and Ringing voice quality are paid special attention, as the essence of the term "resonant voice" was a basic issue throughout a doctoral dissertation where this study was included.

  9. Voice box (image)

    Science.gov (United States)

    The larynx, or voice box, is located in the neck and performs several important functions in the body. The larynx is involved in swallowing, breathing, and voice production. Sound is produced when the air which ...

  10. Voice and Aging

    Science.gov (United States)

    ... dramatic voice changes are those during childhood and adolescence. The larynx (or voice box) and vocal cord tissues do not fully mature until late teenage years. Hormone-related changes during adolescence are ...

  11. Voice and endocrinology

    OpenAIRE

    KVS Hari Kumar; Anurag Garg; Ajai Chandra, N. S.; Singh, S. P.; Rakesh Datta

    2016-01-01

    Voice is one of the advanced features of natural evolution that differentiates human beings from other primates. The human voice is capable of conveying the thoughts into spoken words along with a subtle emotion to the tone. This extraordinary character of the voice in expressing multiple emotions is the gift of God to the human beings and helps in effective interpersonal communication. Voice generation involves close interaction between cerebral signals and the peripheral apparatus consistin...

  12. DLMS Voice Data Entry.

    Science.gov (United States)

    1980-06-01

    between operator and computer displayed on ADM-3A 20c A-I Possible Hardware Configuration for a Multistation Cartographic VDES ...this program a Voice Recognition System (VRS) which can be used to explore the use of voice data entry ( VDE ) in the DIMS or other cartographic data...Multi-Station Cartographic Voice Data Entry System An engineering development model voice data entry system ( VDES ) could be most efficiently

  13. Writing with Voice

    Science.gov (United States)

    Kesler, Ted

    2012-01-01

    In this Teaching Tips article, the author argues for a dialogic conception of voice, based in the work of Mikhail Bakhtin. He demonstrates a dialogic view of voice in action, using two writing examples about the same topic from his daughter, a fifth-grade student. He then provides five practical tips for teaching a dialogic conception of voice in…

  14. Tips for Healthy Voices

    Science.gov (United States)

    ... social interaction as well as for most people’s occupation. Proper care and use of your voice will give you the best chance for having a healthy voice for your entire lifetime. Hoarseness or roughness in your voice is often ...

  15. LMSS - From low data rate to voice services

    Science.gov (United States)

    Rogard, R.

    1992-03-01

    An overview of ESA's approach towards the introduction of Land Mobile Communications in Europe is presented. Emphasis is placed on a description of the payload called EMS to be launched on a host satellite, the Italsat-F2 spacecraft, and the definition of services which are most appropriate for a first-generation-operating Land Mobile Satellite System, namely, PRODAT, a message-handling system, and Europhone, an original approach to 'voice' systems. Attention is given to the EMS payload, characteristics, and capacity, the IF processor and channelization, and market considerations. It is shown that the optimization of the satellite characteristics and the mix of services to be provided are the key elements of a successful entry into the market.

  16. The membrane lateral pressure-perturbing capacity of parabens and their effects on the mechanosensitive channel directly correlate with hydrophobicity.

    Science.gov (United States)

    Kamaraju, Kishore; Sukharev, Sergei

    2008-10-07

    Lipid bilayers provide a natural anisotropic environment for membrane proteins and can serve as apolar reservoirs for lipid-derived second messengers or lipophilic drugs. Partitioning of lipophilic agents changes the lateral pressure distribution in the bilayer, affecting integral proteins. p-Hydroxybenzoic acid esters (parabens) are amphipathic compounds widely used as food and cosmetics preservatives, but the mechanisms of their broad antibacterial action are unknown. Here we describe effects of ethyl, propyl, and butyl parabens on the gating of the bacterial mechanosensitive channel of small conductance (MscS) and compare them with the surface activity and lateral pressure changes measured in lipid monolayers in the presence of these substances. Near the bilayer-monolayer equivalence pressure of 35 mN/m, ethyl, propyl, or butyl paraben present in the subphase at 1 mM increased the surface pressure of the monolayer by 5, 12.5, or 20%, respectively. No spontaneous activation of MscS channels was observed in patch-clamp experiments with parabens added from either the cytoplasmic or periplasmic side. Increasing concentrations of parabens on the cytoplasmic side of excised patches shifted activation curves of MscS toward higher tensions. A good correlation between the pressure increases in monolayers and shifts in activation midpoints in patch-clamp experiments suggested that the more hydrophobic parabens partition more strongly into the lipid and exert larger effects on channel gating through changes in lateral pressure. We show that cytoplasmically presented ethyl or butyl parabens both hasten the process of desensitization of MscS and influence inactivation differently. The higher rate of desensitization is likely due to increased lateral pressure in the cytoplasmic leaflet surrounding the gate. Neither of the parabens strongly affects the rate of recovery and does not seem to penetrate the TM2-TM3 interhelical clefts in MscS. We conclude that the bacterial

  17. Voice handicap in singers.

    Science.gov (United States)

    Murry, Thomas; Zschommler, Anne; Prokop, Jan

    2009-05-01

    The study aimed to determine the differences in responses to the Voice Handicap Index (VHI-10) between singers and nonsingers and to evaluate the ranked order differences of the VHI-10 statements for both groups. The VHI-10 was modified to include statements related to the singing voice for comparison to the original VHI-10. Thirty-five nonsingers with documented voice disorders responded to the VHI-10. A second group, consisting of 35 singers with voice complaints, responded to the VHI-10 with three statements added specifically addressing the singing voice. Data from both groups were analyzed in terms of overall subject self-rating of voice handicap and the rank order of statements from least to most important. The difference between the mean VHI-10 for the singers and nonsingers was not statistically significant, thus, supporting the validity of the VHI-10. However, the 10 statements were ranked differently in terms of their importance by both groups. In addition, when three statements related specifically to the singing voice were substituted in the original VHI-10, the singers judged their voice problem to be more severe than when using the original VHI-10. The type of statements used to assess self-perception of voice handicap may be related to the subject population. Singers with voice problems do not rate their voices to be more handicapped than nonsingers unless statements related specifically to singing are included.

  18. Overexpression of NaV 1.6 channels is associated with the invasion capacity of human cervical cancer.

    Science.gov (United States)

    Hernandez-Plata, Everardo; Ortiz, Cindy S; Marquina-Castillo, Brenda; Medina-Martinez, Ingrid; Alfaro, Ana; Berumen, Jaime; Rivera, Manuel; Gomora, Juan C

    2012-05-01

    Functional activity of voltage-gated sodium channels (VGSC) has been associated to the invasion and metastasis behaviors of prostate, breast and some other types of cancer. We previously reported the functional expression of VGSC in primary cultures and biopsies derived from cervical cancer (CaC). Here, we investigate the relative expression levels of VGSC subunits and its possible role in CaC. Quantitative real-time PCR revealed that mRNA levels of Na(V) 1.6 α-subunit in CaC samples were ∼40-fold higher than in noncancerous cervical (NCC) biopsies. A Na(V) 1.7 α-subunit variant also showed increased mRNA levels in CaC (∼20-fold). All four Na(V) β subunits were also detected in CaC samples, being Na(V) β1 the most abundant. Proteins of Na(V) 1.6 and Na(V) 1.7 α-subunits were immunolocalized in both NCC and CaC biopsies and in CaC primary cultures as well; however, although in NCC sections proteins were mainly relegated to the plasma membrane, in CaC biopsies and primary cultures the respective signal was stronger and widely distributed in both cytoplasm and plasma membrane. Functional activity of Na(V) 1.6 channels in the plasma membrane of CaC cells was confirmed by whole-cell patch-clamp experiments using Cn2, a Na(V) 1.6-specific toxin, which blocked ∼30% of the total sodium current. Blocking of sodium channels VGSC with tetrodotoxin and Cn2 did not affect proliferation neither migration, but reduced by ∼20% the invasiveness of CaC primary culture cells in vitro assays. We conclude that Na(V) 1.6 is upregulated in CaC and could serve as a novel molecular marker for the metastatic behavior of this carcinoma.

  19. Remarks on entanglement assisted classical capacity

    Science.gov (United States)

    Fan, Heng

    2003-06-01

    The property of the optimal signal ensembles of entanglement assisted channel capacity is studied. A relationship between entanglement assisted channel capacity and one-shot capacity of unassisted channel is obtained. The data processing inequalities, convexity and additivity of the entanglement assisted channel capacity are reformulated by simple methods.

  20. Remarks on entanglement assisted classical capacity

    OpenAIRE

    Fan, Heng

    2003-01-01

    The property of the optimal signal ensembles of entanglement assisted channel capacity is studied. A relationship between entanglement assisted channel capacity and one-shot capacity of unassisted channel is obtained. The data processing inequalities, convexity and additivity of the entanglement assisted channel capacity are reformulated by simple methods.

  1. Remarks on entanglement assisted classical capacity

    CERN Document Server

    Fan, H

    2003-01-01

    The property of the optimal signal ensembles of entanglement assisted channel capacity is studied. A relationship between entanglement assisted channel capacity and capacities of unassisted and enviornment channels is obtained. The data processing inequalities, convexity and additivity of the entanglement assisted channel capacity are reformulated by simple methods.

  2. Denitrification capacity and greenhouse gas emissions of soils in channelized and restored reaches along an Alpine river corridor

    Science.gov (United States)

    Shrestha, Juna; Niklaus, Pascal; Samaritani, Emanuela; Frossard, Emmanuel; Tockner, Klement; Luster, Jörg

    2010-05-01

    In order to assess the effects of river restoration on water and air quality, the biogeochemical functions of channelized and restored river reaches have to be quantified. The objective of this study was to compare denitrification potential and greenhouse gas emissions of functional processing zones (FPZ) in a channelized and a recently restored reach of the alpine river Thur in north-eastern Switzerland. The study was part of the project cluster RECORD of the ETH domain, Switzerland, which was initiated to increase the mechanistic understanding of coupled hydrological and ecological processes in river corridors. The denitrification potential represents an important aspect of the soil filter function related to water quality. Besides, it also contributes to the emission of greenhouse gases. Extensively used pasture growing on a sandy loam is the characteristic FPZ of the channelized section. The restored section encompasses five FPZ: (i) bare gravel bars sparsely colonized by plants, (ii) gravel bars densely colonized by grass (mainly canary reed grass with up to 80 cm sandy deposits), (iii) mixed forest dominated by ash and maple, (iv) riparian forest dominated by willow (Salix alba), (v) older overbank sediments stabilized during restoration with young willows separating the forests from the river-gravel bar system (willow bush). The FPZ were sampled in January, April, August and October 2009. In addition, in June and July 2009 two flood events were monitored in the restored section with more frequent samplings. At each date, topsoil samples were collected in each FPZ (four replicates per samples) and analyzed for denitrifier enzyme activity (DEA). In addition, gas samples were taken in-situ using the closed chamber technique to measure soil respiration as well as N2O and CH4 fluxes. In all FPZ, the denitrification potential was mainly governed by soil moisture. It was highest in the willow forest exhibiting low spatial variability. The DEA in pasture, grass zone

  3. Capacity of optical communications over a lossy bosonic channel with a receiver employing the most general coherent electro-optic feedback control

    Science.gov (United States)

    Chung, Hye Won; Guha, Saikat; Zheng, Lizhong

    2017-07-01

    We study the problem of designing optical receivers to discriminate between multiple coherent states using coherent processing receivers—i.e., one that uses arbitrary coherent feedback control and quantum-noise-limited direct detection—which was shown by Dolinar to achieve the minimum error probability in discriminating any two coherent states. We first derive and reinterpret Dolinar's binary-hypothesis minimum-probability-of-error receiver as the one that optimizes the information efficiency at each time instant, based on recursive Bayesian updates within the receiver. Using this viewpoint, we propose a natural generalization of Dolinar's receiver design to discriminate M coherent states, each of which could now be a codeword, i.e., a sequence of N coherent states, each drawn from a modulation alphabet. We analyze the channel capacity of the pure-loss optical channel with a general coherent-processing receiver in the low-photon number regime and compare it with the capacity achievable with direct detection and the Holevo limit (achieving the latter would require a quantum joint-detection receiver). We show compelling evidence that despite the optimal performance of Dolinar's receiver for the binary coherent-state hypothesis test (either in error probability or mutual information), the asymptotic communication rate achievable by such a coherent-processing receiver is only as good as direct detection. This suggests that in the infinitely long codeword limit, all potential benefits of coherent processing at the receiver can be obtained by designing a good code and direct detection, with no feedback within the receiver.

  4. Singing voice outcomes following singing voice therapy.

    Science.gov (United States)

    Dastolfo-Hromack, Christina; Thomas, Tracey L; Rosen, Clark A; Gartner-Schmidt, Jackie

    2016-11-01

    The objectives of this study were to describe singing voice therapy (SVT), describe referred patient characteristics, and document the outcomes of SVT. Retrospective. Records of patients receiving SVT between June 2008 and June 2013 were reviewed (n = 51). All diagnoses were included. Demographic information, number of SVT sessions, and symptom severity were retrieved from the medical record. Symptom severity was measured via the 10-item Singing Voice Handicap Index (SVHI-10). Treatment outcome was analyzed by diagnosis, history of previous training, and SVHI-10. SVHI-10 scores decreased following SVT (mean change = 11, 40% decrease) (P singing lessons (n = 10) also completed an average of three SVT sessions. Primary muscle tension dysphonia (MTD1) and benign vocal fold lesion (lesion) were the most common diagnoses. Most patients (60%) had previous vocal training. SVHI-10 decrease was not significantly different between MTD and lesion. This is the first outcome-based study of SVT in a disordered population. Diagnosis of MTD or lesion did not influence treatment outcomes. Duration of SVT was short (approximately three sessions). Voice care providers are encouraged to partner with a singing voice therapist to provide optimal care for the singing voice. This study supports the use of SVT as a tool for the treatment of singing voice disorders. 4 Laryngoscope, 126:2546-2551, 2016. © 2016 The American Laryngological, Rhinological and Otological Society, Inc.

  5. METHODS FOR QUALITY ENHANCEMENT OF USER VOICE SIGNAL IN VOICE AUTHENTICATION SYSTEMS

    Directory of Open Access Journals (Sweden)

    O. N. Faizulaieva

    2014-03-01

    Full Text Available The reasonability for the usage of computer systems user voice in the authentication process is proved. The scientific task for improving the signal/noise ratio of the user voice signal in the authentication system is considered. The object of study is the process of input and output of the voice signal of authentication system user in computer systems and networks. Methods and means for input and extraction of voice signal against external interference signals are researched. Methods for quality enhancement of user voice signal in voice authentication systems are suggested. As modern computer facilities, including mobile ones, have two-channel audio card, the usage of two microphones is proposed in the voice signal input system of authentication system. Meanwhile, the task of forming a lobe of microphone array in a desired area of voice signal registration (100 Hz to 8 kHz is solved. The usage of directional properties of the proposed microphone array gives the possibility to have the influence of external interference signals two or three times less in the frequency range from 4 to 8 kHz. The possibilities for implementation of space-time processing of the recorded signals using constant and adaptive weighting factors are investigated. The simulation results of the proposed system for input and extraction of signals during digital processing of narrowband signals are presented. The proposed solutions make it possible to improve the value of the signal/noise ratio of the useful signals recorded up to 10, ..., 20 dB under the influence of external interference signals in the frequency range from 4 to 8 kHz. The results may be useful to specialists working in the field of voice recognition and speaker’s discrimination.

  6. Clinical Voices - an update

    DEFF Research Database (Denmark)

    Fusaroli, Riccardo; Weed, Ethan

    Anomalous aspects of speech and voice, including pitch, fluency, and voice quality, are reported to characterise many mental disorders. However, it has proven difficult to quantify and explain this oddness of speech by employing traditional statistical methods. In this talk we will show how the t...... the temporal dynamics of the voice in Asperger's patients enable us to automatically reconstruct the diagnosis, and assess the Autism quotient score. We then generalise the findings to Danish and American children with autism....

  7. Effects of Medications on Voice

    Science.gov (United States)

    ... ENT Doctor Near You Effects of Medications on Voice Effects of Medications on Voice Patient Health Information ... entnet.org . Could Your Medication Be Affecting Your Voice? Some medications including prescription, over-the-counter, and ...

  8. Voiced Reading and Rhythm

    Institute of Scientific and Technical Information of China (English)

    詹艳萍

    2007-01-01

    Since voiced reading is an important way in learning English,rhythm is the most critical factor that enables to read beautifully.This article illustrates the relationship between rhythm and voiced reading,the importance of rhythm,and the methods to develop the sense of rhythm.

  9. Clinical Voices - an update

    DEFF Research Database (Denmark)

    Fusaroli, Riccardo; Weed, Ethan

    Anomalous aspects of speech and voice, including pitch, fluency, and voice quality, are reported to characterise many mental disorders. However, it has proven difficult to quantify and explain this oddness of speech by employing traditional statistical methods. In this talk we will show how...

  10. Borderline Space for Voice

    Science.gov (United States)

    Batchelor, Denise

    2012-01-01

    Being on the borderline as a student in higher education is not always negative, to do with marginalisation, exclusion and having a voice that is vulnerable. Paradoxically, being on the edge also has positive connections with integration, inclusion and having a voice that is strong. Alternative understandings of the concept of borderline space can…

  11. Voice and endocrinology

    Directory of Open Access Journals (Sweden)

    KVS Hari Kumar

    2016-01-01

    Full Text Available Voice is one of the advanced features of natural evolution that differentiates human beings from other primates. The human voice is capable of conveying the thoughts into spoken words along with a subtle emotion to the tone. This extraordinary character of the voice in expressing multiple emotions is the gift of God to the human beings and helps in effective interpersonal communication. Voice generation involves close interaction between cerebral signals and the peripheral apparatus consisting of the larynx, vocal cords, and trachea. The human voice is susceptible to the hormonal changes throughout life right from the puberty until senescence. Thyroid, gonadal and growth hormones have tremendous impact on the structure and function of the vocal apparatus. The alteration of voice is observed even in physiological states such as puberty and menstruation. Astute clinical observers make out the changes in the voice and refer the patients for endocrine evaluation. In this review, we shall discuss the hormonal influence on the voice apparatus in normal and endocrine disorders.

  12. Face the voice

    DEFF Research Database (Denmark)

    Lønstrup, Ansa

    2014-01-01

    will be based on a reception aesthetic and phenomenological approach, the latter as presented by Don Ihde in his book Listening and Voice. Phenomenologies of Sound , and my analytical sketches will be related to theoretical statements concerning the understanding of voice and media (Cavarero, Dolar, La...

  13. Voice integrated systems

    Science.gov (United States)

    Curran, P. Mike

    1977-01-01

    The program at Naval Air Development Center was initiated to determine the desirability of interactive voice systems for use in airborne weapon systems crew stations. A voice recognition and synthesis system (VRAS) was developed and incorporated into a human centrifuge. The speech recognition aspect of VRAS was developed using a voice command system (VCS) developed by Scope Electronics. The speech synthesis capability was supplied by a Votrax, VS-5, speech synthesis unit built by Vocal Interface. The effects of simulated flight on automatic speech recognition were determined by repeated trials in the VRAS-equipped centrifuge. The relationship of vibration, G, O2 mask, mission duration, and cockpit temperature and voice quality was determined. The results showed that: (1) voice quality degrades after 0.5 hours with an O2 mask; (2) voice quality degrades under high vibration; and (3) voice quality degrades under high levels of G. The voice quality studies are summarized. These results were obtained with a baseline of 80 percent recognition accuracy with VCS.

  14. Ontario's Student Voice Initiative

    Science.gov (United States)

    Courtney, Jean

    2014-01-01

    This article describes in some detail aspects of the Student Voice initiative funded and championed by Ontario's Ministry of Education since 2008. The project enables thousands of students to make their voices heard in meaningful ways and to participate in student-led research. Some students from grades 7 to 12 become members of the Student…

  15. Messaging and Voice Conferencing through Wi-Fi Network

    OpenAIRE

    Miss. Nayana H S,; Dr. M C Padma

    2014-01-01

    The use of Wi-Fi enabled android phones as IP phones, and their communication within a local wireless LAN is discussed in this paper. This proposed model is a form of telecommunication that allows exchange of data and voice via Wi-Fi network. The phones, which are Wi-Fi enabled and have android operating system, can be used to communicate with each other through the Wi-Fi communication channel. Proposed system incorporates messaging (Text and voice), conferencing (group conver...

  16. EasyVoice: Integrating voice synthesis with Skype

    CERN Document Server

    Condado, Paulo A

    2007-01-01

    This paper presents EasyVoice, a system that integrates voice synthesis with Skype. EasyVoice allows a person with voice disabilities to talk with another person located anywhere in the world, removing an important obstacle that affect these people during a phone or VoIP-based conversation.

  17. Effects of mutual coupling on the channel capacity of MIMO/SA multi-antenna system%互耦效应对MIMO/SA多天线系统信道容量的影响

    Institute of Scientific and Technical Information of China (English)

    郭爱煌; 肖法; 黄宇胜; 尚秀辉

    2011-01-01

    多输入多输出/智能天线(multiple input multiple output/smart antenna,MIMO/SA)系统是4G的关键技术之一,多天线的互耦效应是影响MIMO/SA多天线系统性能的主要问题.建立了MIMO与SA相结合的多天线系统模型,推导了互耦效应影响下空间相关系数和信道容量的表达式;通过电磁场数值计算和蒙特卡罗方法仿真MIMO/SA多天线系统的各态历经信道容量.结果表明:在典型的角度谱分布下改变天线间距,考虑互耦效应的信道容量围绕无互耦效应时的信道容量上下振荡;基站天线阵列间距增大信道容量持续增大,移动台天线阵列间距增大到0.5倍波长后信道容量基本保持不变;互耦效应增大信道的空域相关性,从而降低信道容量.%Multiple input multiple output and smart antenna (MIMO/SA) system is one of the key technologies for the fourth generation mobile communications system, mutual coupling is the main factor which affects the performance of MIMO/SA multi-antenna systems. A combination model of M1MO and SA is presented. With the existing of mutual coupling effects the expressions of spatial correlation and channel capacity are derived. The ergodic capacity of MIMO/SA multi-antenna systems is simulated using electromagnetic numeric method and Monte Carlo method. The results show that in the typical power azimuth spectrum distribution, the channel capacity which takes mutual coupling into account oscillates up and down around the channel capacity without mutual coupling while changing the distance of the antennas; the channel capacity increases continually while increasing the distance of base station antenna array; when antennas distance of the mobile station is farther than 0. 5 wavelength the channel capacity remains almost the same even though the antenna array distance increases; and mutual coupling increases the channel spatial correlation of MIMO/SA multi-antenna systems and thus reduces the channel capacity.

  18. EXPERIMENTAL STUDY OF FIRMWARE FOR INPUT AND EXTRACTION OF USER’S VOICE SIGNAL IN VOICE AUTHENTICATION SYSTEMS

    Directory of Open Access Journals (Sweden)

    O. N. Faizulaieva

    2014-09-01

    Full Text Available Scientific task for improving the signal-to-noise ratio for user’s voice signal in computer systems and networks during the process of user’s voice authentication is considered. The object of study is the process of input and extraction of the voice signal of authentication system user in computer systems and networks. Methods and means for input and extraction of the voice signal on the background of external interference signals are investigated. Ways for quality improving of the user’s voice signal in systems of voice authentication are investigated experimentally. Firmware means for experimental unit of input and extraction of the user’s voice signal against external interference influence are considered. As modern computer means, including mobile, have two-channel audio card, two microphones are used in the voice signal input. The distance between sonic-wave sensors is 20 mm and it provides forming one direction pattern lobe of microphone array in a desired area of voice signal registration (from 100 Hz to 8 kHz. According to the results of experimental studies, the usage of directional properties of the proposed microphone array and space-time processing of the recorded signals with implementation of constant and adaptive weighting factors has made it possible to reduce considerably the influence of interference signals. The results of firmware experimental studies for input and extraction of the user’s voice signal against external interference influence are shown. The proposed solutions will give the possibility to improve the value of the signal/noise ratio of the useful signals recorded up to 20 dB under the influence of external interference signals in the frequency range from 4 to 8 kHz. The results may be useful to specialists working in the field of voice recognition and speaker discrimination.

  19. Voice Savers for Music Teachers

    Science.gov (United States)

    Cookman, Starr

    2012-01-01

    Music teachers are in a class all their own when it comes to voice use. These elite vocal athletes require stamina, strength, and flexibility from their voices day in, day out for hours at a time. Voice rehabilitation clinics and research show that music education ranks high among the professionals most commonly affected by voice problems.…

  20. Neural mechanisms for voice recognition

    NARCIS (Netherlands)

    Andics, A.V.; McQueen, J.M.; Petersson, K.M.; Gal, V.; Rudas, G.; Vidnyanszky, Z.

    2010-01-01

    We investigated neural mechanisms that support voice recognition in a training paradigm with fMRI. The same listeners were trained on different weeks to categorize the mid-regions of voice-morph continua as an individual's voice. Stimuli implicitly defined a voice-acoustics space, and training expli

  1. Distributed reservation control protocols for random access broadcasting channels

    Science.gov (United States)

    Greene, E. P.; Ephremides, A.

    1981-05-01

    Attention is given to a communication network consisting of an arbitrary number of nodes which can communicate with each other via a time-division multiple access (TDMA) broadcast channel. The reported investigation is concerned with the development of efficient distributed multiple access protocols for traffic consisting primarily of single packet messages in a datagram mode of operation. The motivation for the design of the protocols came from the consideration of efficient multiple access utilization of moderate to high bandwidth (4-40 Mbit/s capacity) communication satellite channels used for the transmission of short (1000-10,000 bits) fixed length packets. Under these circumstances, the ratio of roundtrip propagation time to packet transmission time is between 100 to 10,000. It is shown how a TDMA channel can be adaptively shared by datagram traffic and constant bandwidth users such as in digital voice applications. The distributed reservation control protocols described are a hybrid between contention and reservation protocols.

  2. Accuracy of pitch matching significantly improved by live voice model.

    Science.gov (United States)

    Granot, Roni Y; Israel-Kolatt, Rona; Gilboa, Avi; Kolatt, Tsafrir

    2013-05-01

    Singing is, undoubtedly, the most fundamental expression of our musical capacity, yet an estimated 10-15% of Western population sings "out-of-tune (OOT)." Previous research in children and adults suggests, albeit inconsistently, that imitating a human voice can improve pitch matching. In the present study, we focus on the potentially beneficial effects of the human voice and especially the live human voice. Eighteen participants varying in their singing abilities were required to imitate in singing a set of nine ascending and descending intervals presented to them in five different randomized blocked conditions: live piano, recorded piano, live voice using optimal voice production, recorded voice using optimal voice production, and recorded voice using artificial forced voice production. Pitch and interval matching in singing were much more accurate when participants repeated sung intervals as compared with intervals played to them on the piano. The advantage of the vocal over the piano stimuli was robust and emerged clearly regardless of whether piano tones were played live and in full view or were presented via recording. Live vocal stimuli elicited higher accuracy than recorded vocal stimuli, especially when the recorded vocal stimuli were produced in a forced vocal production. Remarkably, even those who would be considered OOT singers on the basis of their performance when repeating piano tones were able to pitch match live vocal sounds, with deviations well within the range of what is considered accurate singing (M=46.0, standard deviation=39.2 cents). In fact, those participants who were most OOT gained the most from the live voice model. Results are discussed in light of the dual auditory-motor encoding of pitch analogous to that found in speech. Copyright © 2013 The Voice Foundation. Published by Mosby, Inc. All rights reserved.

  3. Quantum Multiple Access Channel

    Institute of Scientific and Technical Information of China (English)

    侯广; 黄民信; 张永德

    2002-01-01

    We consider the transmission of classical information over a quantum channel by many senders, which is a generalization of the two-sender case. The channel capacity region is shown to be a convex hull bound by the yon Neumann entropy and the conditional yon Neumann entropies. The result allows a reasonable distribution of channel capacity over the senders.

  4. Dominant Voice in Hamlet

    Institute of Scientific and Technical Information of China (English)

    李丹

    2015-01-01

    <正>The Tragedy of Hamlet dramatizes the revenge Prince Hamlet exacts on his uncle Claudius for murdering King Hamlet,Claudius’s brother and Prince Hamlet’s father,and then succeeding to the throne and taking as his wife Gertrude,the old king’s widow and Prince Hamlet’s mother.This paper will discuss something about dominant voice in the play.Dominant voice is the major voice in the country,the society,or the whole world.Those people who have the power or

  5. Ethnographic Voice Memo Narratives

    DEFF Research Database (Denmark)

    Rasmussen, Mette Apollo; Conradsen, Maria Bosse

    1800-01-01

    -based technique which actively involves actors in producing ethnography-based data concerning their everyday practice. With the help from smartphone technology it is possible to complement ethnography-based research methods when involving the actors and having them create small voice memo narratives. The voice...... memos create insights of actors‟ everyday practice, without the direct presence of a researcher and could be considered a step towards meeting the dilemmas of research in complex fieldwork settings....

  6. Analysis of Information Hiding Capacity in the Multiple Antennas Coding Channel System%多天线编码信道系统中的信息隐藏容量分析

    Institute of Scientific and Technical Information of China (English)

    卢苗; 陈立全

    2012-01-01

    在分析信道编码和信息隐藏技术相结合的基础上,提出了Alamouti编码多天线系统中的基于LDPC码的信息隐藏方案,理论推导了单天线编码信道及多天线编码信道系统中的信息隐藏容量上限,并进行数值验算和MATLAB仿真验证.实验结果表明,较之单天线编码信道,基于多天线编码信道的信息隐藏容量有明显的提高.%Based on analysis of the combination between channel coding technologies and information hiding technologies, an information hiding scheme based on LDPC codes is proposed, which is implemented in Alamouti coding MIMO system. A theoretical analysis about information hiding capacities of the coding channel system and multi-antennas coding channel system is presented. Then,it evaluates the proposed scheme by numerical analyses and MATLAB simulations. Compared with the single antenna channel coding system experimental results show that the information hiding capacity based on multiple antenna channel coding system is improved significant.

  7. An RFID-Based Smart Structure for the Supply Chain: Resilient Scanning Proofs and Ownership Transfer with Positive Secrecy Capacity Channels.

    Science.gov (United States)

    Burmester, Mike; Munilla, Jorge; Ortiz, Andrés; Caballero-Gil, Pino

    2017-07-04

    The National Strategy for Global Supply Chain Security published in 2012 by the White House identifies two primary goals for strengthening global supply chains: first, to promote the efficient and secure movement of goods, and second to foster a resilient supply chain. The Internet of Things (IoT), and in particular Radio Frequency Identification (RFID) technology, can be used to realize these goals. For product identification, tracking and real-time awareness, RFID tags are attached to goods. As tagged goods move along the supply chain from the suppliers to the manufacturers, and then on to the retailers until eventually they reach the customers, two major security challenges can be identified: (I) to protect the shipment of goods that are controlled by potentially untrusted carriers; and (II) to secure the transfer of ownership at each stage of the chain. For the former, grouping proofs in which the tags of the scanned goods generate a proof of "simulatenous" presence can be employed, while for the latter, ownership transfer protocols (OTP) are used. This paper describes enhanced security solutions for both challenges. We first extend earlier work on grouping proofs and group codes to capture resilient group scanning with untrusted readers; then, we describe a modified version of a recently published OTP based on channels with positive secrecy capacity adapted to be implemented on common RFID systems in the supply chain. The proposed solutions take into account the limitations of low cost tags employed in the supply chain, which are only required to generate pseudorandom numbers and compute one-way hash functions.

  8. Speaking in Character: Voice Communication in Virtual Worlds

    Science.gov (United States)

    Wadley, Greg; Gibbs, Martin R.

    This chapter summarizes 5 years of research on the implications of introducing voice communication systems to virtual worlds. Voice introduces both benefits and problems for players of fast-paced team games, from better coordination of groups and greater social presence of fellow players on the positive side, to negative features such as channel congestion, transmission of noise, and an unwillingness by some to use voice with strangers online. Similarly, in non-game worlds like Second Life, issues related to identity and impression management play important roles, as voice may build greater trust that is especially important for business users, yet it erodes the anonymity and ability to conceal social attributes like gender that are important for other users. A very different mixture of problems and opportunities exists when users conduct several simultaneous conversations in multiple text and voice channels. Technical difficulties still exist with current systems, including the challenge of debugging and harmonizing all the participants' voice setups. Different groups use virtual worlds for very different purposes, so a single modality may not suit all.

  9. Quantum feedback channels

    CERN Document Server

    Bowen, G

    2002-01-01

    In classical information theory the capacity of a noisy communication channel cannot be increased by the use of feedback. In quantum information theory the no-cloning theorem means that noiseless copying and feedback of quantum information cannot be achieved. In this paper, quantum feedback is defined as the unlimited use of a noiseless quantum channel from receiver to sender. Given such quantum feedback, it is shown to provide no increase in the entanglement-assisted capacities of a noisy quantum channel, in direct analogy to the classical case. It is also shown that in various cases of non-assisted capacities, feedback can increase the capacity of many quantum channels.

  10. Voice Matching Using Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Abhishek Bal

    2014-03-01

    Full Text Available In this paper, the use of Genetic Algorithm (GA for voice recognition is described. The practical application of Genetic Algorithm (GA to the solution of engineering problem is a rapidly emerging approach in the field of control engineering and signal processing. Genetic algorithms are useful for searching a space in multi-directional way from large spaces and poorly defined space. Voice is a signal of infinite information. Digital processing of voice signal is very important for automatic voice recognition technology. Nowadays, voice processing is very much important in security mechanism due to mimicry characteristic. So studying the voice feature extraction in voice processing is very necessary in military, hospital, telephone system, investigation bureau and etc. In order to extract valuable information from the voice signal, make decisions on the process, and obtain results, the data needs to be manipulated and analyzed. In this paper, if the instant voice is not matched with same person’s reference voices in the database, then Genetic Algorithm (GA is applied between two randomly chosen reference voices. Again the instant voice is compared with the result of Genetic Algorithm (GA which is used, including its three main steps: selection, crossover and mutation. We illustrate our approach with different sample of voices from human in our institution.

  11. Voice Therapy Practices and Techniques: A Survey of Voice Clinicians.

    Science.gov (United States)

    Mueller, Peter B.; Larson, George W.

    1992-01-01

    Eighty-three voice disorder therapists' ratings of statements regarding voice therapy practices indicated that vocal nodules are the most frequent disorder treated; vocal abuse and hard glottal attack elimination, counseling, and relaxation were preferred treatment approaches; and voice therapy is more effective with adults than with children.…

  12. Voice in early glottic cancer compared to benign voice pathology

    NARCIS (Netherlands)

    Van Gogh, C. D. L.; Mahieu, H. F.; Kuik, D. J.; Rinkel, R. N. P. M.; Langendijk, J. A.; Verdonck-de Leeuw, I. M.

    2007-01-01

    The purpose of this study is to compare (Dutch) Voice Handicap Index (VHIvumc) scores from a selected group of patients with voice problems after treatment for early glottic cancer with patients with benign voice disorders and subjects from the normal population. The study included a group of 35 pat

  13. The inner voice

    Directory of Open Access Journals (Sweden)

    Anthony James Ridgway

    2009-12-01

    Full Text Available The inner voice- we all know what it is because we all have it and use it when we are thinking or reading, for example. Little work has been done on it in our field, with the notable exception of Brian Tomlinson, but presumably it must be a cognitive phenomenon which is of great importance in thinking, language learning, and reading in a foreign language. The inner voice will be discussed as a cognitive psychological phenomenon associated with short-term memory, and distinguished from the inner ear. The process of speech recoding will be examined (the process of converting written language into the inner voice and the importance of developing the inner voice, as a means of both facilitating the production of a new language and enhancing the comprehension of a text in a foreign language, will be emphasized. Finally, ways of developing the inner voice in beginning and intermediate readers of a foreign language will be explored and recommended.

  14. Smartphone App for Voice Disorders

    Science.gov (United States)

    ... on. Feature: Taste, Smell, Hearing, Language, Voice, Balance Smartphone App for Voice Disorders Past Issues / Fall 2013 ... developed a mobile monitoring device that relies on smartphone technology to gather a week's worth of talking, ...

  15. Liquid heat capacity lasers

    Science.gov (United States)

    Comaskey, Brian J.; Scheibner, Karl F.; Ault, Earl R.

    2007-05-01

    The heat capacity laser concept is extended to systems in which the heat capacity lasing media is a liquid. The laser active liquid is circulated from a reservoir (where the bulk of the media and hence waste heat resides) through a channel so configured for both optical pumping of the media for gain and for light amplification from the resulting gain.

  16. Sustainable Consumer Voices

    DEFF Research Database (Denmark)

    Klitmøller, Anders; Rask, Morten; Jensen, Nevena

    2011-01-01

    Aiming to explore how user driven innovation can inform high level design strategies, an in-depth empirical study was carried out, based on data from 50 observations of private vehicle users. This paper reports the resulting 5 consumer voices: Technology Enthusiast, Environmentalist, Design Lover......, Pragmatist and Status Seeker. Expedient use of the voices in creating design strategies is discussed, thus contributing directly to the practice of high level design managers. The main academic contribution of this paper is demonstrating how applied anthropology can be used to generate insights...... into disruptive emergence of product service systems, where quantitative user analyses rely on historical continuation....

  17. VoiceRelay: voice key operation using visual basic.

    Science.gov (United States)

    Abrams, Lise; Jennings, David T

    2004-11-01

    Using a voice key is a popular method for recording vocal response times in a variety of language production tasks. This article describes a class module called VoiceRelay that can be easily utilized in Visual Basic programs for voice key operation. This software-based voice key offers the precision of traditional voice keys (although accuracy is system dependent), as well as the flexibility of volume and sensitivity control. However, VoiceRelay is a considerably less expensive alternative for recording vocal response times because it operates with existing PC hardware and does not require the purchase of external response boxes or additional experiment-generation software. A sample project demonstrating implementation of the VoiceRelay class module may be downloaded from the Psychonomic Society Web archive, www.psychonomic.org/archive.

  18. New Compensation Technique for Fiber Impairments in Ultra High Capacity Super channel Based on (QDPASK Dense wavelength division multiplex (DWDM systems

    Directory of Open Access Journals (Sweden)

    Ibrahim A.Murdas

    2017-07-01

    Full Text Available In this paper we want to increase the data rate and to get larger transmission distance, therefore we use the Advanced modulation technique QDPASK in DWDM system with low channels space. In case of long transmission distance and multi channels system both giving rise to inter channel crosstalk induced by fiber nonlinearities as a result the use of advanced modulation technique becomes difficult. In this paper Quaternary differential phase amplitude shift keying (QDPASK is designed for 32 dense wavelength division multiplexing (DWDM channels, therefore we proposed a new cascade compensation system consist of optical and digital back propagation techniques (ODBP for compensate the linear and nonlinear effects . A performance of the system was reported using QDPASK DWDM fiber-optic system for various system parameters. The research is tested in VPI maker environment.

  19. Voice application development for Android

    CERN Document Server

    McTear, Michael

    2013-01-01

    This book will give beginners an introduction to building voice-based applications on Android. It will begin by covering the basic concepts and will build up to creating a voice-based personal assistant. By the end of this book, you should be in a position to create your own voice-based applications on Android from scratch in next to no time.Voice Application Development for Android is for all those who are interested in speech technology and for those who, as owners of Android devices, are keen to experiment with developing voice apps for their devices. It will also be useful as a starting po

  20. Sustainable Consumer Voices

    DEFF Research Database (Denmark)

    Klitmøller, Anders; Rask, Morten; Jensen, Nevena

    2011-01-01

    Aiming to explore how user driven innovation can inform high level design strategies, an in-depth empirical study was carried out, based on data from 50 observations of private vehicle users. This paper reports the resulting 5 consumer voices: Technology Enthusiast, Environmentalist, Design Lover...

  1. Voices of courage

    Directory of Open Access Journals (Sweden)

    Noraida Abdullah Karim

    2007-07-01

    Full Text Available In May 2007 the Women’s Commission for Refugee Women and Children1 presented its annual Voices of Courage awards to three displaced people who have dedicated their lives to promoting economic opportunities for refugee and displaced women and youth. These are their (edited testimonies.

  2. Listen to a voice

    DEFF Research Database (Denmark)

    Hølge-Hazelton, Bibi

    2001-01-01

    Listen to the voice of a young girl Lonnie, who was diagnosed with Type 1 diabetes at 16. Imagine that she is deeply involved in the social security system. She lives with her mother and two siblings in a working class part of a small town. She is at a special school for problematic youth, and he...

  3. Political animal voices

    NARCIS (Netherlands)

    Meijer, E.R.

    2017-01-01

    In this thesis, I develop a theory of political animal voices. The first part of the thesis focuses on non-human animal languages and forming interspecies worlds. I first investigate the relation between viewing language as exclusively human and seeing humans as categorically different from other

  4. Finding a Voice

    Science.gov (United States)

    Stuart, Shannon

    2012-01-01

    Schools have struggled for decades to provide expensive augmentative and alternative communication (AAC) resources for autistic students with communication challenges. Clunky voice output devices, often included in students' individualized education plans, cost about $8,000, a difficult expense to cover in hard times. However, mobile technology is…

  5. the Voice of Tomorrow

    Institute of Scientific and Technical Information of China (English)

    AlanBurdick

    2003-01-01

    Have you heard Mide? Coule be.Mike is a professional reader,and he's everywhere these days. On MapQuest, the Web-based map service,he'll read aloud whatever directions you ask for. If you like to have AOL or Yahoo! e-mail read aloud to you over the phone, that's Mike's voice you 're hearing. Soon

  6. What the voice reveals.

    NARCIS (Netherlands)

    Ko, Sei Jin

    2007-01-01

    Given that the voice is our main form of communication, we know surprisingly little about how it impacts judgment and behavior. Furthermore, the modern advancement in telecommunication systems, such as cellular phones, has meant that a large proportion of our everyday interactions are conducted voca

  7. The Inner Voice

    Science.gov (United States)

    Ridgway, Anthony James

    2009-01-01

    The inner voice- we all know what it is because we all have it and use it when we are thinking or reading, for example. Little work has been done on it in our field, with the notable exception of Brian Tomlinson, but presumably it must be a cognitive phenomenon which is of great importance in thinking, language learning, and reading in a foreign…

  8. Moving beyond Youth Voice

    Science.gov (United States)

    Serido, Joyce; Borden, Lynne M.; Perkins, Daniel F.

    2011-01-01

    This study combines research documenting the benefits of positive relationships between youth and caring adults on a young person's positive development with studies on youth voice to examine the mechanisms through which participation in youth programs contributes to positive developmental outcomes. Specifically, the study explores whether youth's…

  9. Bodies and Voices

    DEFF Research Database (Denmark)

    A wide-ranging collection of essays centred on readings of the body in contemporary literary and socio-anthropological discourse, from slavery and rape to female genital mutilation, from clothing, ocular pornography, voice, deformation and transmutation to the imprisoned, dismembered, remembered...

  10. Voices for Careers.

    Science.gov (United States)

    York, Edwin G.; Kapadia, Madhu

    Listed in this annotated bibliography are 502 cassette tapes of value to career exploration for Grade 7 through the adult level, whether as individualized instruction, small group study, or total class activity. Available to New Jersey educators at no charge, this Voices for Careers System is also available for duplication on request from the New…

  11. What the voice reveals

    NARCIS (Netherlands)

    Ko, Sei Jin

    2007-01-01

    Given that the voice is our main form of communication, we know surprisingly little about how it impacts judgment and behavior. Furthermore, the modern advancement in telecommunication systems, such as cellular phones, has meant that a large proportion of our everyday interactions are conducted voca

  12. Bodies and Voices

    DEFF Research Database (Denmark)

    A wide-ranging collection of essays centred on readings of the body in contemporary literary and socio-anthropological discourse, from slavery and rape to female genital mutilation, from clothing, ocular pornography, voice, deformation and transmutation to the imprisoned, dismembered, remembered...

  13. Information capacity of quantum observable

    CERN Document Server

    Holevo, A S

    2011-01-01

    In this paper we consider the classical capacities of quantum-classical channels corresponding to measurement of observables. Special attention is paid to the case of continuous observables. We give the formulas for unassisted and entanglement-assisted classical capacities $C,C_{ea}$ and consider some explicitly solvable cases which give new examples of entanglement-breaking channels with $C_{ea}>C.$

  14. Voice over IP in Wireless Heterogeneous Networks

    DEFF Research Database (Denmark)

    Fathi, Hanane; Chakraborty, Shyam; Prasad, Ramjee

    The convergence of different types of traffic has preceded the convergence of systems and services in a wireless heterogeneous network. Voice and data traffic are usually treated separate in both 2G and 2.5G wireless networks. With advances in packet switching technology and especially......IP communications are difficult to achieve in a time-varying environment due to channel errors and traffic congestion and across different systems. The provision of VoIP in wireless heterogeneous networks requires a set of time-efficient control mechanisms to support a VoIP session with acceptable quality...

  15. Queueing analysis of a shared voice-data link

    Science.gov (United States)

    Friedman, D. U.

    1981-11-01

    We consider a link shared by some number of off-hook phone callers and a data queue. The allocation of capacity to voice and data depends on the level of speaker activity (number of talkspurt). A Markov chain model is adopted for this activity, and the resulting data queue performance is analyzed.

  16. DMT of weighted Parallel Channels: Application to Broadcast Channel

    CERN Document Server

    Mroueh, Lina; Othman, Ghaya Rekaya-Ben; Belfiore, Jean-Claude

    2008-01-01

    In a broadcast channel with random packet arrival and transmission queues, the stability of the system is achieved by maximizing a weighted sum rate capacity with suitable weights that depend on the queue size. The weighted sum rate capacity using Dirty Paper Coding (DPC) and Zero Forcing (ZF) is asymptotically equivalent to the weighted sum capacity over parallel single-channels. In this paper, we study the Diversity Multiplexing Tradeoff (DMT) of the fading broadcast channel under a fixed weighted sum rate capacity constraint. The DMT of both identical and different parallel weighted MISO channels is first derived. Finally, we deduce the DMT of a broadcast channel using DPC and ZF precoders.

  17. April 16th : The World Voice Day

    NARCIS (Netherlands)

    Svec, Jan G.; Behlau, Mara

    2007-01-01

    Although the voice is used as an everyday basis of speech, most people realize its importance only when a voice problem arises. Increasing public awareness of the importance of the voice and alertness to voice problems are the main goals of the World Voice Day, which is celebrated yearly on April 16

  18. Risk factors for voice problems in teachers

    NARCIS (Netherlands)

    Kooijman, P. G. C.; de Jong, F. I. C. R. S.; Thomas, G.; Huinck, W.; Donders, R.; Graamans, K.; Schutte, H. K.

    2006-01-01

    In order to identify factors that are associated with voice problems and voice-related absenteeism in teachers, 1,878 questionnaires were analysed. The questionnaires inquired about personal data, voice complaints, voice-related absenteeism from work and conditions that may lead to voice complaints

  19. You're a What? Voice Actor

    Science.gov (United States)

    Liming, Drew

    2009-01-01

    This article talks about voice actors and features Tony Oliver, a professional voice actor. Voice actors help to bring one's favorite cartoon and video game characters to life. They also do voice-overs for radio and television commercials and movie trailers. These actors use the sound of their voice to sell a character's emotions--or an advertised…

  20. Risk factors for voice problems in teachers

    NARCIS (Netherlands)

    Kooijman, P. G. C.; de Jong, F. I. C. R. S.; Thomas, G.; Huinck, W.; Donders, R.; Graamans, K.; Schutte, H. K.

    2006-01-01

    In order to identify factors that are associated with voice problems and voice-related absenteeism in teachers, 1,878 questionnaires were analysed. The questionnaires inquired about personal data, voice complaints, voice-related absenteeism from work and conditions that may lead to voice complaints

  1. Risk factors for voice problems in teachers.

    NARCIS (Netherlands)

    Kooijman, P.G.C.; Jong, F.I.C.R.S. de; Thomas, G.; Huinck, W.J.; Donders, A.R.T.; Graamans, K.; Schutte, H.K.

    2006-01-01

    In order to identify factors that are associated with voice problems and voice-related absenteeism in teachers, 1,878 questionnaires were analysed. The questionnaires inquired about personal data, voice complaints, voice-related absenteeism from work and conditions that may lead to voice complaints

  2. Keyboard With Voice Output

    Science.gov (United States)

    Huber, W. C.

    1986-01-01

    Voice synthesizer tells what key is about to be depressed. Verbal feedback useful for blind operators or where dim light prevents sighted operator from seeing keyboard. Also used where operator is busy observing other things while keying data into control system. Used as training aid for touch typing, and to train blind operators to use both standard and braille keyboards. Concept adapted to such equipment as typewriters, computers, calculators, telephones, cash registers, and on/off controls.

  3. 采用蛇形通道制备较大容量A356铝合金半固态浆料%Preparation of semisolid A356 alloy slurry with larger capacity cast by serpentine channel

    Institute of Scientific and Technical Information of China (English)

    杨小容; 毛卫民; 孙斌煜

    2011-01-01

    采用蛇形通道制备较大容量的A356铝合金半固态浆料,对制备的半固态浆料的整体组织和管道冷却能力对组织的影响进行研究.结果表明,采用冷却能力良好的蛇形通道可制备出理想的较大容量半固态A356铝合金浆料.蛇形通道连续通冷却水时,较大容量半固态A356铝合金浆料轴向和径向的组织均由颗粒状的初生相组成,浆料的整体均匀性良好;而未通冷却水的蛇形通道只能在较大容量浆料的心、中部获得颗粒状初生相,靠近浆料的边部区域则主要为树枝状初生相,整个浆料径向的组织不均匀.浇注温度达到680℃,可以解决合金熔体在浇注过程中容易堵塞的问题.%The integral microstructure of semisolid A356 alloy slurry with larger capacity cast by serpentine channel was studied and the influence of cooling ability of serpentine channel on the microstructure was investigated. The results indicate that ideal slurry with larger capacity can be prepared through serpentine channel with good cooling ability. When the serpentine channel was continuously cooled,both the longitudinal and the radial microstructure of the slurry was composed of granular primary phase and the integral microstructure uniformity of the slurry was good. However,uncooled serpentine channel can only produce larger slurry with fine grains in positions adjacent to its centre and with a large number of dendrites in positions close to its edge,thus,the radial microstructure of larger slurry is nonuniform. The pouring temperature is set up to 680 ℃ and the solid shell inside the channel can be avoided at this pouring temperature.

  4. Why Is My Voice Changing? (For Teens)

    Science.gov (United States)

    ... Week of Healthy Breakfasts Shyness Why Is My Voice Changing? KidsHealth > For Teens > Why Is My Voice ... deeper than a girl's, though. What Causes My Voice to Change? At puberty, guys' bodies begin producing ...

  5. Common Problems That Can Affect Your Voice

    Science.gov (United States)

    ... near you Common Problems That Can Affect Your Voice Common Problems That Can Affect Your Voice Patient ... that traditionally accompany gastro esophageal reflux disease (GERD). Voice Misuse and Overuse Speaking is a physical task ...

  6. Voice and silence in organizations

    Directory of Open Access Journals (Sweden)

    Moaşa, H.

    2011-01-01

    Full Text Available Unlike previous research on voice and silence, this article breaksthe distance between the two and declines to treat them as opposites. Voice and silence are interrelated and intertwined strategic forms ofcommunication which presuppose each other in such a way that the absence of one would minimize completely the other’s presence. Social actors are not voice, or silence. Social actors can have voice or silence, they can do both because they operate at multiple levels and deal with multiple issues at different moments in time.

  7. VOICE REHABILITATION FOLLOWING TOTAL LARYNGECTOMY

    Directory of Open Access Journals (Sweden)

    Balasubramanian Thiagarajan

    2015-03-01

    Full Text Available Despite continuing advances in surgical management of laryngeal malignancy, total laryngectomy is still the treatment of choice in advanced laryngeal malignancies. Considering the longevity of the patient following total laryngectomy, various measures have been adopted in order to provide voice function to the patient. Significant advancements have taken place in voice rehabilitation of post laryngectomy patients. Advancements in oncological surgical techniques and irradiation techniques have literally cured laryngeal malignancies. Among the various voice rehabilitation techniques available TEP (Tracheo oesophageal puncture is considered to be the gold standard. This article attempts to explore the various voice rehabilitation technique available with primary focus on TEP.

  8. Preference for leaders with masculine voices holds in the case of feminine leadership roles.

    Directory of Open Access Journals (Sweden)

    Rindy C Anderson

    Full Text Available Human voice pitch research has focused on perceptions of attractiveness, strength, and social dominance. Here we examine the influence of pitch on selection of leaders, and whether this influence varies by leadership role. Male and female leaders with lower-pitched (i.e., masculine voices are generally preferred by both men and women. We asked whether this preference shifts to favor higher-pitch (i.e., feminine voices within the specific context of leadership positions that are typically held by women (i.e., feminine leadership roles. In hypothetical elections for two such positions, men and women listened to pairs of male and female voices that differed only in pitch, and were asked which of each pair they would vote for. As in previous studies, men and women preferred female candidates with masculine voices. Likewise, men preferred men with masculine voices. Women, however, did not discriminate between male voices. Overall, contrary to research showing that perceptions of voice pitch can be influenced by social context, these results suggest that the influence of voice pitch on perceptions of leadership capacity is largely consistent across different domains of leadership.

  9. The impact of voice on speech realization

    OpenAIRE

    Jelka Breznik

    2014-01-01

    The study discusses spoken literary language and the impact of voice on speech realization. The voice consists of a sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming… The human voice is specifically the part of human sound production in which the vocal folds (vocal cords) are the primary sound source. Our voice is our instrument and identity card. How does the voice (voice tone) affect others and how do they respond, positively or negatively? ...

  10. The Voice Handicap Index with Post-Laryngectomy Male Voices

    Science.gov (United States)

    Evans, Eryl; Carding, Paul; Drinnan, Michael

    2009-01-01

    Background: Surgical treatment for advanced laryngeal cancer involves complete removal of the larynx ("laryngectomy") and initial total loss of voice. Post-laryngectomy rehabilitation involves implementation of different means of "voicing" for these patients wherever possible. There is little information about laryngectomees'…

  11. Pedagogic Voice: Student Voice in Teaching and Engagement Pedagogies

    Science.gov (United States)

    Baroutsis, Aspa; McGregor, Glenda; Mills, Martin

    2016-01-01

    In this paper, we are concerned with the notion of "pedagogic voice" as it relates to the presence of student "voice" in teaching, learning and curriculum matters at an alternative, or second chance, school in Australia. This school draws upon many of the principles of democratic schooling via its utilisation of student voice…

  12. Controlling An Electric Car Starter System Through Voice

    Directory of Open Access Journals (Sweden)

    A.B. Muhammad Firdaus

    2015-04-01

    Full Text Available Abstract These days automotive has turned into a stand out amongst the most well-known modes of transportation on the grounds that a large number of Malaysians could bear to have an auto. There are numerous decisions of innovations in auto that have in the market. One of the engineering is voice controlled framework. Voice Recognition is the procedure of consequently perceiving a certain statement talked by a specific speaker focused around individual data included in discourse waves. This paper is to make an car controlled by voice of human. An essential pre-processing venture in Voice Recognition systems is to recognize the vicinity of noise. Sensitivity to speech variability lacking recognition precision and helplessness to mimic are among the principle specialized obstacles that keep the far reaching selection of speech-based recognition systems. Voice recognition systems work sensibly well with a quiet conditions however inadequately under loud conditions or in twisted channels. The key focus of the project is to control an electric car starter system.

  13. Voice and Speech after Laryngectomy

    Science.gov (United States)

    Stajner-Katusic, Smiljka; Horga, Damir; Musura, Maja; Globlek, Dubravka

    2006-01-01

    The aim of the investigation is to compare voice and speech quality in alaryngeal patients using esophageal speech (ESOP, eight subjects), electroacoustical speech aid (EACA, six subjects) and tracheoesophageal voice prosthesis (TEVP, three subjects). The subjects reading a short story were recorded in the sound-proof booth and the speech samples…

  14. Voice Quality of Psychological Origin

    Science.gov (United States)

    Teixeira, Antonio; Nunes, Ana; Coimbra, Rosa Lidia; Lima, Rosa; Moutinho, Lurdes

    2008-01-01

    Variations in voice quality are essentially related to modifications of the glottal source parameters, such as: F[subscript 0], jitter, and shimmer. Voice quality is affected by prosody, emotional state, and vocal pathologies. Psychogenic vocal pathology is particularly interesting. In the present case study, the speaker naturally presented a…

  15. Voice handicap index in Swedish.

    Science.gov (United States)

    Ohlsson, Ann-Christine; Dotevall, Hans

    2009-01-01

    The objective of this study was to evaluate a Swedish version of the voice handicap index questionnaire (Sw-VHI). A total of 57 adult, dysphonic patients and 15 healthy controls completed the Sw-VHI and rated the degree of vocal fatigue and hoarseness on visual analogue scales. A perceptual voice evaluation was also performed. Test-retest reliability was analyzed in 38 subjects without voice complaints. Sw-VHI distinguished between dysphonic subjects and controls (P 0.84) and test-retest reliability (intraclass correlation coefficient >0.75) were good. Only moderate or weak correlations were found between Sw-VHI and the subjective and perceptual voice ratings. The data indicate that a difference above 13 points for the total Sw-VHI score and above 6 points for the Sw-VHI subscales is significant for an individual when comparing two different occasions. In conclusion, the Sw-VHI appears to be a robust instrument for assessment of the psycho-social impact of a voice disorder. However, Sw-VHI seems to, at least partly, capture different aspects of voice function to the subjective voice ratings and the perceptual voice evaluation.

  16. Enhancing Author's Voice through Scripting

    Science.gov (United States)

    Young, Chase J.; Rasinski, Timothy V.

    2011-01-01

    The authors suggest using scripting as a strategy to mentor and enhance author's voice in writing. Through gradual release, students use authentic literature as a model for writing with voice. The authors also propose possible extensions for independent practice, integration across content areas, and tips for evaluation.

  17. Voice, Schooling, Inequality, and Scale

    Science.gov (United States)

    Collins, James

    2013-01-01

    The rich studies in this collection show that the investigation of voice requires analysis of "recognition" across layered spatial-temporal and sociolinguistic scales. I argue that the concepts of voice, recognition, and scale provide insight into contemporary educational inequality and that their study benefits, in turn, from paying attention to…

  18. Voices in History

    Directory of Open Access Journals (Sweden)

    Ivan Leudar

    2001-06-01

    Full Text Available Experiences of “hearing voices” nowadays usually count as verbal hallucinations and they indicate serious mental illness. Some are first rank symptoms of schizophrenia, and the mass media, at least in Britain, tend to present them as antecedents of impulsive violence. They are, however, also found in other psychiatric conditions and epidemiological surveys reveal that even individuals with no need of psychiatric help can hear voices, sometimes following bereavement or abuse, but sometimes for no discernible reason. So do these experiences necessarily mean insanity and violence, and must they be thought of as pathogenic hallucinations; or are there other ways to understand them and live with them, and with what consequences?One way to make our thinking more flexible is to turn to history. We find that hearing voices was always an enigmatic experience, and the people who had it were rare. The gallery of voice hearers is, though, distinguished and it includes Galilei, Bunyan and St Teresa. Socrates heard a daemon who guided his actions, but in his time this did not signify madness, nor was it described as a hallucination. Yet in 19th century French psychological medicine the daemon became a hallucination and Socrates was retrospectively diagnosed as mentally ill. This paper examines the controversies which surrounded the experience at different points in history as well as the practice of retrospective psychiatry. The conclusion reached on the basis of the historical materials is that the experience and the ontological status it is ascribed are not trans-cultural or trans-historic but situated both in history and in the contemporary conflicts.

  19. Hadamard quantum broadcast channels

    Science.gov (United States)

    Wang, Qingle; Das, Siddhartha; Wilde, Mark M.

    2017-10-01

    We consider three different communication tasks for quantum broadcast channels, and we determine the capacity region of a Hadamard broadcast channel for these various tasks. We define a Hadamard broadcast channel to be such that the channel from the sender to one of the receivers is entanglement-breaking and the channel from the sender to the other receiver is complementary to this one. As such, this channel is a quantum generalization of a degraded broadcast channel, which is well known in classical information theory. The first communication task we consider is classical communication to both receivers, the second is quantum communication to the stronger receiver and classical communication to other, and the third is entanglement-assisted classical communication to the stronger receiver and unassisted classical communication to the other. The structure of a Hadamard broadcast channel plays a critical role in our analysis: The channel to the weaker receiver can be simulated by performing a measurement channel on the stronger receiver's system, followed by a preparation channel. As such, we can incorporate the classical output of the measurement channel as an auxiliary variable and solve all three of the above capacities for Hadamard broadcast channels, in this way avoiding known difficulties associated with quantum auxiliary variables.

  20. Facing Sound - Voicing Art

    DEFF Research Database (Denmark)

    Lønstrup, Ansa

    2013-01-01

    This article is based on examples of contemporary audiovisual art, with a special focus on the Tony Oursler exhibition Face to Face at Aarhus Art Museum ARoS in Denmark in March-July 2012. My investigation involves a combination of qualitative interviews with visitors, observations of the audienc......´s interactions with the exhibition and the artwork in the museum space and short analyses of individual works of art based on reception aesthetics and phenomenology and inspired by newer writings on sound, voice and listening....

  1. Voice over IP Security

    CERN Document Server

    Keromytis, Angelos D

    2011-01-01

    Voice over IP (VoIP) and Internet Multimedia Subsystem technologies (IMS) are rapidly being adopted by consumers, enterprises, governments and militaries. These technologies offer higher flexibility and more features than traditional telephony (PSTN) infrastructures, as well as the potential for lower cost through equipment consolidation and, for the consumer market, new business models. However, VoIP systems also represent a higher complexity in terms of architecture, protocols and implementation, with a corresponding increase in the potential for misuse. In this book, the authors examine the

  2. Effects on vocal range and voice quality of singing voice training: the classically trained female voice.

    Science.gov (United States)

    Pabon, Peter; Stallinga, Rob; Södersten, Maria; Ternström, Sten

    2014-01-01

    A longitudinal study was performed on the acoustical effects of singing voice training under a given study program, using the voice range profile (VRP). Pretraining and posttraining recordings were made of students who participated in a 3-year bachelor singing study program. A questionnaire that included questions on optimal range, register use, classification, vocal health and hygiene, mixing technique, and training goals was used to rate and categorize self-assessed voice changes. Based on the responses, a subgroup of 10 classically trained female voices was selected, which was homogeneous enough for effects of training to be identified. The VRP perimeter contour was analyzed for effects of voice training. Also, a mapping within the VRP of voice quality, as expressed by the crest factor, was used to indicate the register boundaries and to monitor the acoustical consequences of the newly learned vocal technique of "mixed voice." VRPs were averaged across subjects. Findings were compared with the self-assessed vocal changes. Pre/post comparison of the average VRPs showed, in the midrange, (1) a decrease in the VRP area that was associated with the loud chest voice, (2) a reduction of the crest factor values, and (3) a reduction of maximum sound pressure level values. The students' self-evaluations of the voice changes appeared in some cases to contradict the VRP findings. VRPs of individual voices were seen to change over the course of a singing education. These changes were manifest also in the average group. High-resolution computerized recording, complemented with an acoustic register marker, allows a meaningful assessment of some effects of training, on an individual basis and for groups that comprise singers of a specific genre. It is argued that this kind of investigation is possible only within a focused training program, given by a faculty who has agreed on the goals. Copyright © 2014 The Voice Foundation. Published by Mosby, Inc. All rights reserved.

  3. The voices and protests of China's labour NGOs and their effort to promote migrant worker rights

    OpenAIRE

    Yamaguchi, Mami

    2015-01-01

    Labour NGOs in China are relatively new organizations that emerged in the 1990s and have spread during the 2000s. Migrant workers in China are weak both socially and economically and have been lacking ways of voicing grievances and protesting. Grassroots labour NGOs for migrant workers seem to be an efficient channel for their voices. This paper examines how labour NGOs emerged and how they function in the context of current Chinese society. This paper adopts the case study method to describe...

  4. Questioning Photovoice Research: Whose Voice?

    Science.gov (United States)

    Evans-Agnew, Robin A; Rosemberg, Marie-Anne S

    2016-07-01

    Photovoice is an important participatory research tool for advancing health equity. Our purpose is to critically review how participant voice is promoted through the photovoice process of taking and discussing photos and adding text/captions. PubMed, Scopus, PsycINFO, and Web of Science databases were searched from the years 2008 to 2014 using the keywords photovoice, photonovella, photovoice and social justice, and photovoice and participatory action research. Research articles were reviewed for how participant voice was (a) analyzed, (b) exhibited in community forums, and (c) disseminated through published manuscripts. Of 21 studies, 13 described participant voice in the data analysis, 14 described participants' control over exhibiting photo-texts, seven manuscripts included a comprehensive set of photo-texts, and none described participant input on choice of manuscript photo-texts. Photovoice designs vary in the advancement of participant voice, with the least advancement occurring in manuscript publication. Future photovoice researchers should expand approaches to advancing participant voice.

  5. Voice quality of psychological origin.

    Science.gov (United States)

    Teixeira, Antonio; Nunes, Ana; Coimbra, Rosa Lídia; Lima, Rosa; Moutinho, Lurdes

    2008-01-01

    Variations in voice quality are essentially related to modifications of the glottal source parameters, such as: F0, jitter, and shimmer. Voice quality is affected by prosody, emotional state, and vocal pathologies. Psychogenic vocal pathology is particularly interesting. In the present case study, the speaker naturally presented a ventricular band voice whereas in a controlled production he was able to use a more normal phonation process. A small corpus was recorded which included sustained vowels and short sentences in both registers. A normal speaker was also recorded in similar tasks. Annotation and extraction of parameters were made using Praat's voice report function. Application of the Hoarseness Diagram to sustained productions situates this case in the pseudo-glottic phonation region. Analysis of several different parameters related to F0, jitter, shimmer, and harmonicity revealed that the speaker with psychogenic voice was capable of controlling certain parameters (e.g. F0 maximum) but was unable to correct others such as shimmer.

  6. Muscular tension and body posture in relation to voice handicap and voice quality in teachers with persistent voice complaints.

    NARCIS (Netherlands)

    Kooijman, P.G.C.; Jong, F.I.C.R.S. de; Oudes, M.J.; Huinck, W.J.; Acht, H. van; Graamans, K.

    2005-01-01

    The aim of this study was to investigate the relationship between extrinsic laryngeal muscular hypertonicity and deviant body posture on the one hand and voice handicap and voice quality on the other hand in teachers with persistent voice complaints and a history of voice-related absenteeism. The st

  7. Bodies, Spaces, Voices, Silences

    Directory of Open Access Journals (Sweden)

    Donatella Mazzoleni

    2013-07-01

    Full Text Available A good architecture should not only allow functional, formal and technical quality for urban spaces, but also let the voice of the city be perceived, listened, enjoyed. Every city has got its specific sound identity, or “ISO” (R. O. Benenzon, made up of a complex texture of background noises and fluctuation of sound figures emerging and disappearing in a game of continuous fadings. For instance, the ISO of Naples is characterized by a spread need of hearing the sound return of one’s/others voices, by a hate of silence. Cities may fall ill: illness from noise, within super-crowded neighbourhoods, or illness from silence, in the forced isolation of peripheries. The proposal of an urban music therapy denotes an unpublished and innovative enlarged interdisciplinary research path, where architecture, music, medicine, psychology, communication science may converge, in order to work for rebalancing spaces and relation life of the urban collectivity, through the care of body and sound dimensions.

  8. Infinitely many kinds of quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Hastings, Matthew B [Los Alamos National Laboratory

    2008-01-01

    We define the ability of a quantum channel to simulate another by means of suitable encoding and decoding operations. While classical channels have only two equivalence classes under simulation (channels with non-vanishing capacity and those with vanishing capacity), we show that there are an uncountable infinity of different equivalence classes of quantum channels using the example of the quantum erasure channel. Our results also imply a kind of 'Matthew principle' for error correction on certain channels.

  9. 设置导流岛的信号交叉口右转通行能力模型%Capacity Model of the Right-turn Lane at Signalized Intersection With Channelized Islands

    Institute of Scientific and Technical Information of China (English)

    赖元文; 荣建; 刘小明

    2012-01-01

    In order to estimate the capacity of right-turn lane at signalized intersections with channelized islands. Based on the gap acceptance model, this paper proposes a new approach to calculating the capacity of right-turn lane at signalized intersections with channelized islands. This model takes into account the interference of non-motorized traffic enter channelized islands. The non-motorized traffic is treated as the traffic on the major road-a crosswalk, which has great impacts on right-turn vehicles on the minor road-an exclusive right-turn lane. The basic model is modified by introducing the red light effect adjustment coefficient. The new model is calibrated and tested using the field data collected at 6 signalized intersections with ehannelized islands in 4 cities. The average relative error between the calculated value and the observed is 9.28% , which means the proposed method in this paper can better estimate the capacity of an exclusive free right-turn lane under the interference of non-motorized traffic.%为了计算在信号交叉口设置导流岛后右转车道的通行能力,以接受间隙理论模型为基础,给出了针对设置导流岛的信号交叉口右转车道通行能力计算方法.考虑到非机动车进入导流岛对右转车辆产生较大影响,确定以非机动车流为主路,提出红灯效应修正系数,对基础模型进行修正.通过4个城市6个设置导流岛的信号交叉口实测数据进行模型标定和检验.比较模型计算值与实际观测值发现,平均相对误差为9.28%,表明本文所提计算方法能较好地反映非机动车对右转车道通行能力影响的实际情况.

  10. EVALUACIÓN EXPERIMENTAL DE CAPACIDAD MIMO DE ARREGLOS DE ANTENAS PIFA COMPACTOS EN BANDA DE 2.45 GHz EXPERIMENTAL EVALUATION OF MIMO CHANNEL CAPACITY FOR COMPACT ARRAYS OF PIFA ANTENNAS AT 2.45 GHz BAND

    Directory of Open Access Journals (Sweden)

    Héctor Carrasco E

    2007-12-01

    Full Text Available En este trabajo se presentan resultados experimentales de medición de canal y evaluación de capacidad MIMO (Multiple Input Multiple Output de arrays de antenas PIFA (Planar Inverted "F" Antenna compactos en la banda de frecuencia de 2.45 GHz, en entornos interiores ricos en multitrayecto. Se evalúan dos configuraciones básicas de arrays, Lineal y Cuadrada de cuatro antenas PIFA, cuyas características de bajo perfil y grados de libertad de construcción y configuración constituyen ventajas comparativas para aplicaciones con terminales compactos potables. Las mediciones de la matriz de canal MIMO se hacen utilizando un VNA (Vector Network Analyzer controlado vía estándar GPIB (General Purpose Interface Bus. La capacidad MIMO se evalúa estadísticamente para un gran número de medidas del canal, en espacio y frecuencia, con separación de antenas en cada array de 0,1 a 0,8 longitudes de onda, con el objetivo principal de estudiar el efecto del acoplamiento mutuo en la capacidad MIMO. Los resultados de capacidad medida muestran que las configuraciones propuestas más eficientes pueden operar como mínimo hasta separaciones de antenas en el rango de 0,3 a 0,4 longitudes de onda, sin producir gran degradación de capacidad debido al acoplamiento y bloqueo de señal. Este resultado implica separaciones cercanas a 4 cm y, en consecuencia, arrays significativamente compactosThis paper presents experimental results of indoor MIMO wireless channel and channel capacity evaluation for compact PIFA (Planar Inverted "F" Antenna antenna arrays at the 2.45 GHz frequency band. Linear and square array configurations are evaluated using PIFA antenna elements because of its advantages of low profile and flexible configuration design for compact and portable mobile terminals. Measurements are performed using a VNA with GPIB standard for automatic data acquisition. MIMO channel capacity results are calculated from a large amount of data combining uncorrelated

  11. 80-Channel Multiplexer-Demultiplexer Module for DWDM Communications using Hybrid AWG -- Interleaver Technology

    Science.gov (United States)

    Rablau, Corneliu; Bredthauer, Lance

    2007-10-01

    Aside from the more traditional data, voice and e-mail communications, new bandwidth intensive applications in the larger consumer markets, such as music, digital pictures and movies, have led to an explosive increase in the demand for transmission capacity for optical communications networks. This has resulted in a widespread deployment of Dense Wavelength Division Multiplexing (DWDM) as a means of increasing the communications capacity by multiplexing and transmitting signals of different wavelengths (establishing multiple communication channels) through a single strand of fiber. We report on the design, assembly and characterization of a 50-GHz, 80-channel Mux-Demux module for DWDM systems. The module has been assembled from two commercially available 100 GHz, 40-channel Array Waveguide Grating (AWG) modules and a 50-GHz to 100-GHz interleaver. Relevant performance parameters such as insertion loss, channel uniformity, next-channel isolation (crosstalk) and integrated cross-talk are presented and discussed in contrast with the performance of other competing technologies such as Thin-Film-Filter-based Mux-Demux devices.

  12. Crossing Cultures with Multi-Voiced Journals

    Science.gov (United States)

    Styslinger, Mary E.; Whisenant, Alison

    2004-01-01

    In this article, the authors discuss the benefits of using multi-voiced journals as a teaching strategy in reading instruction. Multi-voiced journals, an adaptation of dual-voiced journals, encourage responses to reading in varied, cultured voices of characters. It is similar to reading journals in that they prod students to connect to the lives…

  13. Lexical frequency and voice assimilation.

    Science.gov (United States)

    Ernestus, Mirjam; Lahey, Mybeth; Verhees, Femke; Baayen, R Harald

    2006-08-01

    Acoustic duration and degree of vowel reduction are known to correlate with a word's frequency of occurrence. The present study broadens the research on the role of frequency in speech production to voice assimilation. The test case was regressive voice assimilation in Dutch. Clusters from a corpus of read speech were more often perceived as unassimilated in lower-frequency words and as either completely voiced (regressive assimilation) or, unexpectedly, as completely voiceless (progressive assimilation) in higher-frequency words. Frequency did not predict the voice classifications over and above important acoustic cues to voicing, suggesting that the frequency effects on the classifications were carried exclusively by the acoustic signal. The duration of the cluster and the period of glottal vibration during the cluster decreased while the duration of the release noises increased with frequency. This indicates that speakers reduce articulatory effort for higher-frequency words, with some acoustic cues signaling more voicing and others less voicing. A higher frequency leads not only to acoustic reduction but also to more assimilation.

  14. Modeling and analysis of voice and data in cognitive radio networks

    CERN Document Server

    Gunawardena, Subodha

    2014-01-01

    This Springer Brief investigates the voice and elastic/interactive data service support over cognitive radio networks (CRNs), in terms of their delay requirements. The increased demand for wireless communication conflicts with the scarcity of the radio spectrum, but CRNS allow for more efficient use of the networks. The authors review packet level delay requirements of the voice service and session level delay requirements of the elastic/interactive data services, particularly constant-rate and on-o? voice tra?c capacities in CRNs with centralized and distributed network coordination. Some gen

  15. Resource Planning for Voice over Wireless Both-Way Transmission Media

    Directory of Open Access Journals (Sweden)

    B. Tsankov

    2008-04-01

    Full Text Available The medium in IEEE 802.11- and IEEE 802.16-based networks for voice communications can be considered "both-way" - for transmission and reception. Therefore, the packet arrivals for voice dialogue services in such networks are not strictly independent. In this paper, we discuss the traffic capacity in the call (network layer and suggest accounting for the impact of the correlated nature of two-way voice conversations on performance estimation. We present analytical results and numerical examples.

  16. Capacity Maximizing Constellations

    Science.gov (United States)

    Barsoum, Maged; Jones, Christopher

    2010-01-01

    Some non-traditional signal constellations have been proposed for transmission of data over the Additive White Gaussian Noise (AWGN) channel using such channel-capacity-approaching codes as low-density parity-check (LDPC) or turbo codes. Computational simulations have shown performance gains of more than 1 dB over traditional constellations. These gains could be translated to bandwidth- efficient communications, variously, over longer distances, using less power, or using smaller antennas. The proposed constellations have been used in a bit-interleaved coded modulation system employing state-ofthe-art LDPC codes. In computational simulations, these constellations were shown to afford performance gains over traditional constellations as predicted by the gap between the parallel decoding capacity of the constellations and the Gaussian capacity

  17. Voice Habits and Behaviors: Voice Care Among Flamenco Singers.

    Science.gov (United States)

    Garzón García, Marina; Muñoz López, Juana; Y Mendoza Lara, Elvira

    2017-03-01

    The purpose of this study is to analyze the vocal behavior of flamenco singers, as compared with classical music singers, to establish a differential vocal profile of voice habits and behaviors in flamenco music. Bibliographic review was conducted, and the Singer's Vocal Habits Questionnaire, an experimental tool designed by the authors to gather data regarding hygiene behavior, drinking and smoking habits, type of practice, voice care, and symptomatology perceived in both the singing and the speaking voice, was administered. We interviewed 94 singers, divided into two groups: the flamenco experimental group (FEG, n = 48) and the classical control group (CCG, n = 46). Frequency analysis, a Likert scale, and discriminant and exploratory factor analysis were used to obtain a differential profile for each group. The FEG scored higher than the CCG in speaking voice symptomatology. The FEG scored significantly higher than the CCG in use of "inadequate vocal technique" when singing. Regarding voice habits, the FEG scored higher in "lack of practice and warm-up" and "environmental habits." A total of 92.6% of the subjects classified themselves correctly in each group. The Singer's Vocal Habits Questionnaire has proven effective in differentiating flamenco and classical singers. Flamenco singers are exposed to numerous vocal risk factors that make them more prone to vocal fatigue, mucosa dehydration, phonotrauma, and muscle stiffness than classical singers. Further research is needed in voice training in flamenco music, as a means to strengthen the voice and enable it to meet the requirements of this musical genre. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  18. 线性不确定系统信息受限下的远程跟踪%Remote Output Regulation for Linear Uncertain Systems via a Limited Capacity Communication Channel

    Institute of Scientific and Technical Information of China (English)

    王隔霞

    2012-01-01

    This note considers the output regulation problem for linear uncertainty systems via a limited capacity channel. The object is to control an uncertain system so as to reject the disturbances and have its output tracking reference commands generated at a remote location and transmitted through the communication channel. A controller is designed to achieve the control goal using the reconstructed commands. Finally, one simulation example is given to illustrate the validity of our proposed approach.%研究了信息受限下一类线性不确定系统的跟踪调节问题.假定由高阶微分方程产生的参考信号与受控系统(不确定线性系统)通过有限容量信道相连.针对该信号设计了具体的编码方式,并在受控系统端重构了该参考信号,进而依据此重构信号设计了跟踪控制器,最终到达了跟踪目标.最后数值例子验证了本文结论的有效性.

  19. Voices of the Unheard

    DEFF Research Database (Denmark)

    Matthiesen, Noomi Christine Linde

    2014-01-01

    . They were in two different classes at both schools, i.e. four classes in total. The families were followed for 18 months. Formal interviews were conducted with mothers and teachers, parent-teacher conferences were recorded, participant observations were conducted in classrooms and playgrounds, afterschool...... is that Somali diaspora parents (and with special focus on mothers as these where the parents who took most responsibility in the four cases of this research) have difficulty expressing their opinions as there are structural, historical and social dynamics that create conditions in which their voices...... are silenced, or at least restricted significantly, resulting in marginalizing consequences. The focus in each article is on here-and-now interactional dynamics but in order to understand these constitutive negotiations, it is argued that the analysis must be situated in a description of the constituted...

  20. Passing on power & voice

    DEFF Research Database (Denmark)

    Noer, Vibeke Røn; Nielsen, Cathrine Sand

    2014-01-01

    . The education lasts for 3,5 years and the landmark of the educational model is the continuously shifts between teaching in classroom and teaching in clinical practice. Clinical teaching takes place at approved clinical placement institutions in hospitals and in the social and health care services outside...... intention of gaining knowledge about other possible ways to perform the education. The class, named the E-class, followed what in the field was named ‘an experimental educational model based on experienced-based learning’ (Nielsen et al. 2011). The experiential educational model is argued as an experiment.......aspx Higher degree of student involvement in planning as well as teaching was in the field presented as a part of ‘the overall educational approach’. In the course ‘Acute, Critical Nursing & Terminal, Palliative Care’ this was transferred into an innovative pedagogy with intend to pass on power and voice...

  1. Voice stress analysis

    Science.gov (United States)

    Brenner, Malcolm; Shipp, Thomas

    1988-01-01

    In a study of the validity of eight candidate voice measures (fundamental frequency, amplitude, speech rate, frequency jitter, amplitude shimmer, Psychological Stress Evaluator scores, energy distribution, and the derived measure of the above measures) for determining psychological stress, 17 males age 21 to 35 were subjected to a tracking task on a microcomputer CRT while parameters of vocal production as well as heart rate were measured. Findings confirm those of earlier studies that increases in fundamental frequency, amplitude, and speech rate are found in speakers involved in extreme levels of stress. In addition, it was found that the same changes appear to occur in a regular fashion within a more subtle level of stress that may be characteristic, for example, of routine flying situations. None of the individual speech measures performed as robustly as did heart rate.

  2. Voice over IP

    OpenAIRE

    Mantula, Juha

    2006-01-01

    Tämä opinnäytetyö käsittelee Voice over Internet Protocol -tekniikkaa ja sen tuomia mahdollisuuksia yrityselämässä. Teoriaosa käsittelee VoIP:n kannalta tärkeitä pro-tokollia ja standardeja, VoIP:n ominaisuuksia sekä esittelee erilaisia puheohjelmia, jotka käyttävät VoIP-tekniikkaa hyväkseen. Empiirinen osuus tutkii Viestintä Ky Pitkärannan Skype-ohjelman käyttöä. Työn tarkoituksena on selvittää VoIP:n hyviä ja huonoja puolia ja sitä kuinka tek-niikkaa voidaan käyttää hyväksi päivittäisessä ...

  3. Quantum reading capacity

    Science.gov (United States)

    Pirandola, Stefano; Lupo, Cosmo; Giovannetti, Vittorio; Mancini, Stefano; Braunstein, Samuel L.

    2011-11-01

    The readout of a classical memory can be modelled as a problem of quantum channel discrimination, where a decoder retrieves information by distinguishing the different quantum channels encoded in each cell of the memory (Pirandola 2011 Phys. Rev. Lett. 106 090504). In the case of optical memories, such as CDs and DVDs, this discrimination involves lossy bosonic channels and can be remarkably boosted by the use of nonclassical light (quantum reading). Here we generalize these concepts by extending the model of memory from single-cell to multi-cell encoding. In general, information is stored in a block of cells by using a channel-codeword, i.e. a sequence of channels chosen according to a classical code. Correspondingly, the readout of data is realized by a process of ‘parallel’ channel discrimination, where the entire block of cells is probed simultaneously and decoded via an optimal collective measurement. In the limit of a large block we define the quantum reading capacity of the memory, quantifying the maximum number of readable bits per cell. This notion of capacity is nontrivial when we suitably constrain the physical resources of the decoder. For optical memories (encoding bosonic channels), such a constraint is energetic and corresponds to fixing the mean total number of photons per cell. In this case, we are able to prove a separation between the quantum reading capacity and the maximum information rate achievable by classical transmitters, i.e. arbitrary classical mixtures of coherent states. In fact, we can easily construct nonclassical transmitters that are able to outperform any classical transmitter, thus showing that the advantages of quantum reading persist in the optimal multi-cell scenario.

  4. Voice and choice by delegation.

    Science.gov (United States)

    van de Bovenkamp, Hester; Vollaard, Hans; Trappenburg, Margo; Grit, Kor

    2013-02-01

    In many Western countries, options for citizens to influence public services are increased to improve the quality of services and democratize decision making. Possibilities to influence are often cast into Albert Hirschman's taxonomy of exit (choice), voice, and loyalty. In this article we identify delegation as an important addition to this framework. Delegation gives individuals the chance to practice exit/choice or voice without all the hard work that is usually involved in these options. Empirical research shows that not many people use their individual options of exit and voice, which could lead to inequality between users and nonusers. We identify delegation as a possible solution to this problem, using Dutch health care as a case study to explore this option. Notwithstanding various advantages, we show that voice and choice by delegation also entail problems of inequality and representativeness.

  5. The Christian voice in philosophy

    Directory of Open Access Journals (Sweden)

    Stuart Fowler

    1982-03-01

    Full Text Available In this paper the Rev. Stuart Fowler outlines a Christian voice in Philosophy and urges the Christian philosopher to investigate his position and his stance with integrity and honesty.

  6. Voice Force tulekul / Tõnu Ojala

    Index Scriptorium Estoniae

    Ojala, Tõnu, 1969-

    2005-01-01

    60. sünnipäeva tähistava Tallinna Tehnikaülikooli Akadeemilise Meeskoori juubelihooaja üritusest - a capella pop-gruppide festivalist Voice Force (kontserdid 12. nov. klubis Parlament ja 3. dets. Vene Kultuurikeskuses)

  7. Voice Force tulekul / Tõnu Ojala

    Index Scriptorium Estoniae

    Ojala, Tõnu, 1969-

    2005-01-01

    60. sünnipäeva tähistava Tallinna Tehnikaülikooli Akadeemilise Meeskoori juubelihooaja üritusest - a capella pop-gruppide festivalist Voice Force (kontserdid 12. nov. klubis Parlament ja 3. dets. Vene Kultuurikeskuses)

  8. Feature Extraction of Voice Segments Using Cepstral Analysis for Voice Regeneration

    OpenAIRE

    Banerjee, P. S.; Baisakhi Chakraborty; Jaya Banerjee

    2015-01-01

    Even though a lot of work has been done on areas of speech to text and vice versa or voice detection or similarity analysis of two voice samples but very less emphasis has be given to voice regeneration. General algorithms for distinct voice checking for two voice sources paved way for our endeavor in reconstructing the voice from the source voice samples provided. By utilizing these algorithms and putting further stress on the feature extraction part we tried to fabricate the source voice wi...

  9. Voice Simulation in Nursing Education.

    Science.gov (United States)

    Kepler, Britney B; Lee, Heeyoung; Kane, Irene; Mitchell, Ann M

    2016-01-01

    The goal of this study was to improve prelicensure nursing students' attitudes toward and self-efficacy related to delivering nursing care to patients with auditory hallucinations. Based on the Hearing Voices That Are Distressing curriculum, 87 participants were instructed to complete 3 tasks while wearing headphones delivering distressing voices. Comparing presimulation and postsimulation results, this study suggests that the simulation significantly improved attitudes toward patients with auditory hallucinations; however, self-efficacy related to caring for these patients remained largely unchanged.

  10. Work-related voice disorder

    OpenAIRE

    Paulo Eduardo Przysiezny; Luciana Tironi Sanson Przysiezny

    2015-01-01

    INTRODUCTION: Dysphonia is the main symptom of the disorders of oral communication. However, voice disorders also present with other symptoms such as difficulty in maintaining the voice (asthenia), vocal fatigue, variation in habitual vocal fundamental frequency, hoarseness, lack of vocal volume and projection, loss of vocal efficiency, and weakness when speaking. There are several proposals for the etiologic classification of dysphonia: functional, organofunctional, organic, and work-related...

  11. Tracheostomy cannulas and voice prosthesis.

    Science.gov (United States)

    Kramp, Burkhard; Dommerich, Steffen

    2009-01-01

    Cannulas and voice prostheses are mechanical aids for patients who had to undergo tracheotomy or laryngectomy for different reasons. For better understanding of the function of those artificial devices, first the indications and particularities of the previous surgical intervention are described in the context of this review. Despite the established procedure of percutaneous dilatation tracheotomy e.g. in intensive care units, the application of epithelised tracheostomas has its own position, especially when airway obstruction is persistent (e.g. caused by traumata, inflammations, or tumors) and a longer artificial ventilation or special care of the patient are required. In order to keep the airways open after tracheotomy, tracheostomy cannulas of different materials with different functions are available. For each patient the most appropriate type of cannula must be found. Voice prostheses are meanwhile the device of choice for rapid and efficient voice rehabilitation after laryngectomy. Individual sizes and materials allow adaptation of the voice prostheses to the individual anatomical situation of the patients. The combined application of voice prostheses with HME (Head and Moisture Exchanger) allows a good vocal as well as pulmonary rehabilitation. Precondition for efficient voice prosthesis is the observation of certain surgical principles during laryngectomy. The duration of the prosthesis mainly depends on material properties and biofilms, mostly consisting of funguses and bacteries. The quality of voice with valve prosthesis is clearly superior to esophagus prosthesis or electro-laryngeal voice. Whenever possible, tracheostoma valves for free-hand speech should be applied. Physicians taking care of patients with speech prostheses after laryngectomy should know exactly what to do in case the device fails or gets lost.

  12. Voice Collection under Different Spectrum

    Directory of Open Access Journals (Sweden)

    Min Li

    2013-05-01

    Full Text Available According to the short-time Fourier transform theory and principle of digital filtering, this paper established a mathematical model called collection of voice signal collection at different spectrum. The voice signal was a non-stationary process, while the standard Fourier transform only applied to the periodic signal, transient signals or stationary random signal. Therefore, the standard Fourier transform could not be directly used for the speech signal. By controlling the input different types and parameters, this paper analyzed the collected original voice signal spectrum with the use of MATLAB software platform. At the same time, it realized the extraction, recording and playback of the speech signal at different frequencies. Therefore, the waveforms could be displayed obviously on the graphic user interface and voice effect could be more clearly. Meanwhile, the result was verified by the hardware platforms, which consisted of TMS320VC5509A [1] chip and TLV320AIC23 voice chip. The results showed that the extraction of voice signal under different spectrum model was scientific, rational and effective.

  13. The impact of voice on speech realization

    Directory of Open Access Journals (Sweden)

    Jelka Breznik

    2014-12-01

    Full Text Available The study discusses spoken literary language and the impact of voice on speech realization. The voice consists of a sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming… The human voice is specifically the part of human sound production in which the vocal folds (vocal cords are the primary sound source. Our voice is our instrument and identity card. How does the voice (voice tone affect others and how do they respond, positively or negatively? How important is voice (voice tone in communication process? The study presents how certain individuals perceive voice. The results of the research on the relationships between the spoken word, excellent speaker, voice and description / definition / identification of specific voices done by experts in the field of speech and voice as well as non-professionals are presented. The study encompasses two focus groups. One consists of amateurs (non-specialists in the field of speech or voice who have no knowledge in this field and the other consists of professionals who work with speech or language or voice. The questions were intensified from general to specific, directly related to the topic. The purpose of such a method of questioning was to create relaxed atmosphere, promote discussion, allow participants to interact, complement, and to set up self-listening and additional comments.

  14. Optimal superdense coding over memory channels

    Energy Technology Data Exchange (ETDEWEB)

    Shadman, Z.; Kampermann, H.; Bruss, D.; Macchiavello, C. [Institute fuer Theoretische Physik III, Heinrich-Heine-Universitaet Duesseldorf, DE-40225 Duesseldorf (Germany); Dipartimento di Fisica ' ' A. Volta' ' and INFM-Unita di Pavia, Via Bassi 6, IT-27100 Pavia (Italy)

    2011-10-15

    We study the superdense coding capacity in the presence of quantum channels with correlated noise. We investigate both the cases of unitary and nonunitary encoding. Pauli channels for arbitrary dimensions are treated explicitly. The superdense coding capacity for some special channels and resource states is derived for unitary encoding. We also provide an example of a memory channel where nonunitary encoding leads to an improvement in the superdense coding capacity.

  15. Station Capacity

    DEFF Research Database (Denmark)

    Landex, Alex

    2011-01-01

    Stations are often limiting the capacity of railway networks. This is due to extra need of tracks when trains stand still, trains turning around, and conflicting train routes. Although stations are often the capacity bottlenecks, most capacity analysis methods focus on open line capacity. Therefore......, this paper presents methods to analyze station capacity. Four methods to analyze station capacity are developed. The first method is an adapted UIC 406 capacity method that can be used to analyze switch zones and platform tracks at stations that are not too complex. The second method examines the need...... the probability of conflicts and the minimum headway times into account. The last method analyzes how optimal platform tracks are used by examining the arrival and departure pattern of the trains. The developed methods can either be used separately to analyze specific characteristics of the capacity of a station...

  16. Giving Voice to Values: an undergraduate nursing curriculum project.

    Science.gov (United States)

    Lynch, Sandra; Hart, Bethne; Costa, Catherine M

    2014-01-01

    Among the competency standards stipulated by the Australian Nursing and Midwifery Council for graduating students are competencies in moral and ethical decision making and ethics education within professions such as nursing has traditionally focussed on these competencies, on raising ethical awareness and developing skills of analysis and reasoning. However, ethics education in tertiary settings places less emphasis on developing students' capacities to act on their values. This paper explains and explores the adoption of Dr. Mary Gentile's curriculum (the Giving Voice to Values curriculum).which specifically focuses on developing students' capacities to act on their values. The curriculum (Gentile, 2010) assists students and professionals to explore, script and rehearse responses which build upon their capacity to respond in accordance with their own values in complex workplace settings in which they face conflicts of value and belief. The paper firstly examines the theoretical underpinnings of the Giving Voice to Values (GVV) curriculum. It then presents the integration and evaluation phase of a Project inspired by the GVV methodology, using a case study approach within two areas of an undergraduate nursing curriculum. As a pilot project, this initiative has provided signposts to further curriculum development and to research pathways within the UNDA School of Nursing, by highlighting students' uncertainties regarding their own professional values, and their intense struggles to voice their values within health care contexts.

  17. The Study of MSADQ/CDMA Protocol in Voice/Data Integration Packet Networks

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new packet medium access protocol, namely, minislot signalingaccess based on distributed queues(MSADQ/CDMA), is proposed in voice and data intergration CDMA networks. The MSADQ protocol is based on distributed queues and collision resolution algorithm. Through proper management of the PN codes, the number of random competition collision reduces greatly, the multiple access interference (MAI) decreases. It has several special access signaling channels to carry the voice and data access request. Each slot is devided into several control minislots (CMSs), in which the Data Terminals (DT) or Voice Terminals (VT) transmit their request. According to the voice and data traffic character, the signaling access structure is proposed. The code assign rules and queue managing rules are also proposed to ensure the QoS requirement of each traffic. Comparisions with other three protocol are developed by simulation, which shows that MSADQ/CDMA protocol occupies less PN codes, but still has very good performance.

  18. Station Capacity

    DEFF Research Database (Denmark)

    Landex, Alex

    2011-01-01

    Stations are often limiting the capacity of railway networks. This is due to extra need of tracks when trains stand still, trains turning around, and conflicting train routes. Although stations are often the capacity bottlenecks, most capacity analysis methods focus on open line capacity. Therefore......, this paper presents methods to analyze station capacity. Four methods to analyze station capacity are developed. The first method is an adapted UIC 406 capacity method that can be used to analyze switch zones and platform tracks at stations that are not too complex. The second method examines the need...... for platform tracks and the probability that arriving trains will not get a platform track immediately at arrival. The third method is a scalable method that analyzes the conflicts in the switch zone(s). In its simplest stage, the method just analyzes the track layout while the more advanced stages also take...

  19. Mechanics of human voice production and control

    Science.gov (United States)

    Zhang, Zhaoyan

    2016-01-01

    As the primary means of communication, voice plays an important role in daily life. Voice also conveys personal information such as social status, personal traits, and the emotional state of the speaker. Mechanically, voice production involves complex fluid-structure interaction within the glottis and its control by laryngeal muscle activation. An important goal of voice research is to establish a causal theory linking voice physiology and biomechanics to how speakers use and control voice to communicate meaning and personal information. Establishing such a causal theory has important implications for clinical voice management, voice training, and many speech technology applications. This paper provides a review of voice physiology and biomechanics, the physics of vocal fold vibration and sound production, and laryngeal muscular control of the fundamental frequency of voice, vocal intensity, and voice quality. Current efforts to develop mechanical and computational models of voice production are also critically reviewed. Finally, issues and future challenges in developing a causal theory of voice production and perception are discussed. PMID:27794319

  20. Does the speaker's voice quality influence children's performance on a language comprehension test?

    Science.gov (United States)

    Lyberg-Åhlander, Viveka; Haake, Magnus; Brännström, Jonas; Schötz, Susanne; Sahlén, Birgitta

    2015-02-01

    A small number of studies have explored children's perception of speakers' voice quality and its possible influence on language comprehension. The aim of this explorative study was to investigate the relationship between the examiner's voice quality, the child's performance on a digital version of a language comprehension test, the Test for Reception of Grammar (TROG-2), and two measures of cognitive functioning. The participants were (n = 86) mainstreamed 8-year old children with typical language development. Two groups of children (n = 41/45) were presented with the TROG-2 through recordings of one female speaker: one group was presented with a typical voice and the other with a simulated dysphonic voice. Significant associations were found between executive functioning and language comprehension. The results also showed that children listening to the dysphonic voice achieved significantly lower scores for more difficult sentences ("the man but not the horse jumps") and used more self-corrections on simpler sentences ("the girl is sitting"). Findings suggest that a dysphonic speaker's voice may force the child to allocate capacity to the processing of the voice signal at the expense of comprehension. The findings have implications for clinical and research settings where standardized language tests are used.

  1. Capacity Expansion and Allocation of Logistics System in a Multi-channel Supply Chain%多渠道供应链中物流系统的容量扩充与分配模型

    Institute of Scientific and Technical Information of China (English)

    刘开军; 张子刚

    2009-01-01

    When a traditional supplier extends her business from the single channel of in-store retailers to the multi-channel of in-store retailers and e-retailers, she needs to expand her logistics system to supply the new demands from online customers. This paper considers a two-echelon logistics system consisting of a center warehouse and several district warehouses. A capacity expansion and allocation model (CEAM) is developed with the structure of current logistics system unchanged. And a Lagrangian relaxation algorithm is designed to solve CEAM. Numerical experiments show the efficiency of the algorithm and illustrate the trade off between transportation cost and inventory pooling effect when searching for the optimal solution.%考虑一个传统供应链将市场由单一的实体商店零售扩大到互联网上的在线零售,为满足新增的在线零售需求,供应商需要扩充物流系统的供应容量,并设计新增容量的分配方案.本文针对由一个中心仓库和多个地区仓库组成的二级物流系统,在保留现有配送网络结构的基础上,构建了物流系统的容量扩充与分配模型,并提出一种基于拉格朗日松弛法的求解算法.我们通过数值实验表明了算法的有效性,并通过数值算例说明了运输成本与库存汇聚效应对最优容量扩充与分配方案的影响.

  2. Native voice, self-concept and the moral case for personalized voice technology.

    Science.gov (United States)

    Nathanson, Esther

    2017-01-01

    Purpose (1) To explore the role of native voice and effects of voice loss on self-concept and identity, and survey the state of assistive voice technology; (2) to establish the moral case for developing personalized voice technology. Methods This narrative review examines published literature on the human significance of voice, the impact of voice loss on self-concept and identity, and the strengths and limitations of current voice technology. Based on the impact of voice loss on self and identity, and voice technology limitations, the moral case for personalized voice technology is developed. Results Given the richness of information conveyed by voice, loss of voice constrains expression of the self, but the full impact is poorly understood. Augmentative and alternative communication (AAC) devices facilitate communication but, despite advances in this field, voice output cannot yet express the unique nuances of individual voice. The ethical principles of autonomy, beneficence and equality of opportunity establish the moral responsibility to invest in accessible, cost-effective, personalized voice technology. Conclusions Although further research is needed to elucidate the full effects of voice loss on self-concept, identity and social functioning, current understanding of the profoundly negative impact of voice loss establishes the moral case for developing personalized voice technology. Implications for Rehabilitation Rehabilitation of voice-disordered patients should facilitate self-expression, interpersonal connectedness and social/occupational participation. Proactive questioning about the psychological and social experiences of patients with voice loss is a valuable entry point for rehabilitation planning. Personalized voice technology would enhance sense of self, communicative participation and autonomy and promote shared healthcare decision-making. Further research is needed to identify the best strategies to preserve and strengthen identity and sense of

  3. Children's Voice or Children's Voices? How Educational Research Can Be at the Heart of Schooling

    Science.gov (United States)

    Stern, Julian

    2015-01-01

    There are problems with considering children and young people in schools as quite separate individuals, and with considering them as members of a single collectivity. The tension is represented in the use of "voice" and "voices" in educational debates. Voices in dialogue, in contrast to "children's voice", are…

  4. Voice complaints, risk factors for voice problems and history of voice problems in relation to puberty in female student teachers.

    NARCIS (Netherlands)

    Thomas, G.; Jong, F.I.C.R.S. de; Kooijman, P.G.C.; Donders, A.R.T.; Cremers, C.W.R.J.

    2006-01-01

    The aim of the study was to estimate voice complaints, risk factors for voice complaints and history of voice problems in student teachers before they embarked on their professional teaching career. A cross-sectional questionnaire survey was performed among female student teachers. The response rate

  5. Voice complaints, risk factors for voice problems and history of voice problems in relation to puberty in female student teachers.

    NARCIS (Netherlands)

    Thomas, G.; Jong, F.I.C.R.S. de; Kooijman, P.G.C.; Donders, A.R.T.; Cremers, C.W.R.J.

    2006-01-01

    The aim of the study was to estimate voice complaints, risk factors for voice complaints and history of voice problems in student teachers before they embarked on their professional teaching career. A cross-sectional questionnaire survey was performed among female student teachers. The response rate

  6. Human voice recognition depends on language ability.

    Science.gov (United States)

    Perrachione, Tyler K; Del Tufo, Stephanie N; Gabrieli, John D E

    2011-07-29

    The ability to recognize people by their voice is an important social behavior. Individuals differ in how they pronounce words, and listeners may take advantage of language-specific knowledge of speech phonology to facilitate recognizing voices. Impaired phonological processing is characteristic of dyslexia and thought to be a basis for difficulty in learning to read. We tested voice-recognition abilities of dyslexic and control listeners for voices speaking listeners' native language or an unfamiliar language. Individuals with dyslexia exhibited impaired voice-recognition abilities compared with controls only for voices speaking their native language. These results demonstrate the importance of linguistic representations for voice recognition. Humans appear to identify voices by making comparisons between talkers' pronunciations of words and listeners' stored abstract representations of the sounds in those words.

  7. Quick Statistics about Voice, Speech, and Language

    Science.gov (United States)

    ... here Home » Health Info » Statistics and Epidemiology Quick Statistics About Voice, Speech, Language Voice, Speech, Language, and ... no 205. Hyattsville, MD: National Center for Health Statistics. 2015. Hoffman HJ, Li C-M, Losonczy K, ...

  8. Introduction: Textual and contextual voices of translation

    DEFF Research Database (Denmark)

    2017-01-01

    Voices – marks of the tangle of subjectivities involved in textual processes – constitute the very fabric of texts in general and translations in particular. The title of this book, Textual and Contextual Voices of Translation, refers both to textual voices, that is, the voices found within...... the translated texts, and to contextual voices, that is, the voices of those involved in shaping, commenting, or otherwise influencing the textual voices. The latter appear in prefaces, reviews, and other texts that surround the translated texts and provide them with a context. Our main claim is that studying...... both the textual and contextual voices helps us better understand and explain the complexity of both the translation process and the translation product. The dovetailed approach to translation research that is advocated in this book aims at highlighting the diversity of participants, power positions...

  9. Quantum Reading Capacity

    CERN Document Server

    Pirandola, Stefano; Giovannetti, Vittorio; Mancini, Stefano; Braunstein, Samuel L

    2011-01-01

    The readout of a classical memory can be modelled as a problem of quantum channel discrimination, where a decoder retrieves information by distinguishing the different quantum channels encoded in each cell of the memory [S. Pirandola, Phys. Rev. Lett. 106, 090504 (2011)]. In the case of optical memories, such as CDs and DVDs, this discrimination involves lossy bosonic channels and can be remarkably boosted by the use of nonclassical light (quantum reading). Here we generalize these concepts by extending the model of memory from single-cell to multi-cell encoding. In general, information is stored in a block of cells by using a channel-codeword, i.e., a sequence of channels chosen according to a classical code. Correspondingly, the readout of data is realized by a process of "parallel" channel discrimination, where the entire block of cells is probed simultaneously and decoded via an optimal collective measurement. In the limit of an infinite block we define the quantum reading capacity of the memory, quantify...

  10. Multimodal processing of emotional information in 9-month-old infants I: emotional faces and voices.

    Science.gov (United States)

    Otte, R A; Donkers, F C L; Braeken, M A K A; Van den Bergh, B R H

    2015-04-01

    Making sense of emotions manifesting in human voice is an important social skill which is influenced by emotions in other modalities, such as that of the corresponding face. Although processing emotional information from voices and faces simultaneously has been studied in adults, little is known about the neural mechanisms underlying the development of this ability in infancy. Here we investigated multimodal processing of fearful and happy face/voice pairs using event-related potential (ERP) measures in a group of 84 9-month-olds. Infants were presented with emotional vocalisations (fearful/happy) preceded by the same or a different facial expression (fearful/happy). The ERP data revealed that the processing of emotional information appearing in human voice was modulated by the emotional expression appearing on the corresponding face: Infants responded with larger auditory ERPs after fearful compared to happy facial primes. This finding suggests that infants dedicate more processing capacities to potentially threatening than to non-threatening stimuli.

  11. Design, modeling, and analysis of multi-channel demultiplexer/demodulator

    Science.gov (United States)

    Lee, David D.; Woo, K. T.

    1991-01-01

    Traditionally, satellites have performed the function of a simple repeater. Newer data distribution satellite architectures, however, require demodulation of many frequency division multiplexed uplink channels by a single demultiplexer/demodulator unit, baseband processing and routing of individual voice/data circuits, and remodulation into time division multiplexed (TDM) downlink carriers. The TRW MCDD (Multichannel Demultiplexer/Multirate Demodulator) operates on a 37.4 MHz composite input signal. Individual channel data rates are either 64 Kbps or 2.048 Mbps. The wideband demultiplexer divides the input signal into 1.44 MHz segments containing either a single 2.048 Mbps channel or thirty two 64 Kbps channels. In the latter case, the narrowband demultiplexer further divides the single 1.44 MHz wideband channel into thirty two 45 KHz narrowband channels. With this approach the time domain Fast Fourier Transformation (FFT) channelizer processing capacity is matched well to the bandwidth and number of channels to be demultiplexed. By using a multirate demodulator fewer demodulators are required while achieving greater flexibility. Each demodulator can process a wideband channel or thirty two narrowband channels. Either all wideband channels, a mixture of wideband and narrowband channels, or all narrowband channels can be demodulated. The multirate demodulator approach also has lower nonrecurring costs since only one design and development effort is needed. TRW has developed a proof of concept (POC) model which fully demonstrates the signal processing fuctions of MCDD. It is capable of processing either three 2.048 Mbps channels or two 2.048 Mbps channels and thirty two 64 Kbps channels. An overview of important MCDD system engineering issues is presented as well as discussion on some of the Block Oriented System Simulation analyses performed for design verification and selection of operational parameters of the POC model. Systems engineering analysis of the POC

  12. NASA balloon: Aircraft ranging, data and voice experiment

    Science.gov (United States)

    Wishna, S.; Hamby, C.; Reed, D.

    1972-01-01

    A series of tests to evaluate, at L-band, the ranging, voice, and data communications concepts proposed for the air traffic control experiment of the Applications Technology Satellite-F are described. The ground station facilities, balloon platforms and the aircraft were supplied by the European Space Research Organization. One ground simulation and two aircraft flights at low elevation angles were conducted. Even under high interference conditions good performance was obtained for both voice communications and side tone ranging. High bit errors occurred in the data channels resulting in false commands. As a result of the experience gained in operating the equipment in an aircraft environment several recommendations were made for improving the equipment performance.

  13. Speaker's voice as a memory cue.

    Science.gov (United States)

    Campeanu, Sandra; Craik, Fergus I M; Alain, Claude

    2015-02-01

    Speaker's voice occupies a central role as the cornerstone of auditory social interaction. Here, we review the evidence suggesting that speaker's voice constitutes an integral context cue in auditory memory. Investigation into the nature of voice representation as a memory cue is essential to understanding auditory memory and the neural correlates which underlie it. Evidence from behavioral and electrophysiological studies suggest that while specific voice reinstatement (i.e., same speaker) often appears to facilitate word memory even without attention to voice at study, the presence of a partial benefit of similar voices between study and test is less clear. In terms of explicit memory experiments utilizing unfamiliar voices, encoding methods appear to play a pivotal role. Voice congruency effects have been found when voice is specifically attended at study (i.e., when relatively shallow, perceptual encoding takes place). These behavioral findings coincide with neural indices of memory performance such as the parietal old/new recollection effect and the late right frontal effect. The former distinguishes between correctly identified old words and correctly identified new words, and reflects voice congruency only when voice is attended at study. Characterization of the latter likely depends upon voice memory, rather than word memory. There is also evidence to suggest that voice effects can be found in implicit memory paradigms. However, the presence of voice effects appears to depend greatly on the task employed. Using a word identification task, perceptual similarity between study and test conditions is, like for explicit memory tests, crucial. In addition, the type of noise employed appears to have a differential effect. While voice effects have been observed when white noise is used at both study and test, using multi-talker babble does not confer the same results. In terms of neuroimaging research modulations, characterization of an implicit memory effect

  14. Voicing Consciousness: The Mind in Writing

    Science.gov (United States)

    Luce-Kapler, Rebecca; Catlin, Susan; Sumara, Dennis; Kocher, Philomene

    2011-01-01

    In this paper, the authors investigate the enduring power of voice as a concept in writing pedagogy. They argue that one can benefit from considering Elbow's assertion that both text and voice be considered as important aspects of written discourse. In particular, voice is a powerful metaphor for the material, social and historical nature of…

  15. Understanding the 'Anorexic Voice' in Anorexia Nervosa.

    Science.gov (United States)

    Pugh, Matthew; Waller, Glenn

    2016-07-20

    In common with individuals experiencing a number of disorders, people with anorexia nervosa report experiencing an internal 'voice'. The anorexic voice comments on the individual's eating, weight and shape and instructs the individual to restrict or compensate. However, the core characteristics of the anorexic voice are not known. This study aimed to develop a parsimonious model of the voice characteristics that are related to key features of eating disorder pathology and to determine whether patients with anorexia nervosa fall into groups with different voice experiences. The participants were 49 women with full diagnoses of anorexia nervosa. Each completed validated measures of the power and nature of their voice experience and of their responses to the voice. Different voice characteristics were associated with current body mass index, duration of disorder and eating cognitions. Two subgroups emerged, with 'weaker' and 'stronger' voice experiences. Those with stronger voices were characterized by having more negative eating attitudes, more severe compensatory behaviours, a longer duration of illness and a greater likelihood of having the binge-purge subtype of anorexia nervosa. The findings indicate that the anorexic voice is an important element of the psychopathology of anorexia nervosa. Addressing the anorexic voice might be helpful in enhancing outcomes of treatments for anorexia nervosa, but that conclusion might apply only to patients with more severe eating psychopathology. Copyright © 2016 John Wiley & Sons, Ltd.

  16. Voice and culture: A prospect theory approach

    NARCIS (Netherlands)

    Paddock, E.L.; Ko, Junsu; Cropanzano, R.; Bagger, J.; El Akremi, A.; Camerman, A.; Greguras, G. J.; Mladinic, A.; Moliner, C.; Nam, K.; Törnblom, K.; Van den Bos, Kees

    2015-01-01

    The present study examines the congruence of individuals' minimum preferred amounts of voice with the prospect theory value function across nine countries. Accounting for previously ignored minimum preferred amounts of voice and actual voice amounts integral to testing the steepness of gain and loss

  17. Finding Voice: Learning about Language and Power

    Science.gov (United States)

    Christensen, Linda

    2011-01-01

    Christensen discusses why teachers need to teach students "voice" in its social and political context, to show the intersection of voice and power, to encourage students to ask, "Whose voices get heard? Whose are marginalized?" As Christensen writes, "Once students begin to understand that Standard English is one language among many, we can help…

  18. Analyzing the mediated voice - a datasession

    DEFF Research Database (Denmark)

    Lawaetz, Anna

    Broadcasted voices are technologically manipulated. In order to achieve a certain autencity or sound of “reality” paradoxically the voices are filtered and trained in order to reach the listeners. This “mis-en-scene” is important knowledge when it comes to the development of a consistent method o...... of analysis of the mediated voice...

  19. Analyzing the mediated voice - a datasession

    DEFF Research Database (Denmark)

    Lawaetz, Anna

    Broadcasted voices are technologically manipulated. In order to achieve a certain autencity or sound of “reality” paradoxically the voices are filtered and trained in order to reach the listeners. This “mis-en-scene” is important knowledge when it comes to the development of a consistent method...... of analysis of the mediated voice...

  20. Voice and culture: A prospect theory approach

    NARCIS (Netherlands)

    Paddock, E.L.; Ko, Junsu; Cropanzano, R.; Bagger, J.; El Akremi, A.; Camerman, A.; Greguras, G. J.; Mladinic, A.; Moliner, C.; Nam, K.; Törnblom, K.; Van den Bos, Kees

    2015-01-01

    The present study examines the congruence of individuals' minimum preferred amounts of voice with the prospect theory value function across nine countries. Accounting for previously ignored minimum preferred amounts of voice and actual voice amounts integral to testing the steepness of gain and loss

  1. "Voice Forum" The Human Voice as Primary Instrument in Music Therapy

    DEFF Research Database (Denmark)

    Pedersen, Inge Nygaard; Storm, Sanne

    2009-01-01

    Aspects will be drawn on the human voice as tool for embodying our psychological and physiological state, and attempting integration of feelings. Presentations and dialogues on different methods and techniques in "Therapy related body-and voice work.", as well as the human voice as a tool for non...... for nonverbal orientation and information both to our selves and others. Focus on training on the voice instrument, the effect and impact of the human voice, and listening perspectives...

  2. Voice-Specialized Speech-Language Pathologist's Criteria for Discharge from Voice Therapy.

    Science.gov (United States)

    Gillespie, Amanda I; Gartner-Schmidt, Jackie

    2017-08-07

    No standard protocol exists to determine when a patient is ready and able to be discharged from voice therapy. The aim of the present study was to determine what factors speech-language pathologists (SLPs) deem most important when discharging a patient from voice therapy. A second aim was to determine if responses differed based on years of voice experience. Step 1: Seven voice-specialized SLPs generated a list of items thought to be relevant to voice therapy discharge. Step 2: Fifty voice-specialized SLPs rated each item on the list in terms of importance in determining discharge from voice therapy. Step 1: Four themes emerged-outcome measures, laryngeal appearance, SLP perceptions, and patient factors-as important items when determining discharge from voice therapy. Step 2: The top five most important criteria for discharge readiness were that the patient had to be able to (1) independently use a better voice (transfer), (2) function with his or her new voice production in activities of daily living (transfer), (3) differentiate between good and bad voice, (4) take responsibility for voice, and (5) sound better from baseline. Novice and experienced clinicians agreed between 94% and 97% concerning what was deemed "very important." SLPs agree that a patient's ability to use voice techniques in conversation and real-life situations outside of the therapy room are the most important determinants for voice therapy discharge. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  3. Carrying Capacity

    DEFF Research Database (Denmark)

    Schroll, Henning; Andersen, Jan; Kjærgård, Bente

    2012-01-01

    A spatial planning act was introduced inIndonesia 1992 and renewed in 2008. It emphasised the planning role of decentralised authorities. The spatial planning act covers both spatial and environmental issues. It defines the concept of carrying capacity and includes definitions of supportive...... carrying capacity (SCC) and assimilative carrying capacity (ACC). The act mandates that the latter two aspects must be taken into consideration in the local spatial plans. The present study aimed at developing a background for a national guideline for carrying capacity in Indonesian provinces and districts...... standard or governmental political objective exists. In most cases it was possible to select a set of indicators, including thresholds that are workable in a carrying capacity planning at the local administrative levels. Not all relevant sectors at the decentralized level were included. Indicators of SCC...

  4. Capacity of the Stationary Gaussian Channel

    Science.gov (United States)

    1988-03-01

    defined by a covariance function rW - 1 - corresponding to a rational spectral density function 4w. Hw will denote the REHS of rw with parameter set tO,m...wide sense (w.s.) stationary processes X with a SDF ( spectral density function ), denoted by tx, such that I/Ow is bounded and f A -{X)d& 2rP. The

  5. Quantum channels with a finite memory

    CERN Document Server

    Bowen, G; Bowen, Garry; Mancini, Stefano

    2004-01-01

    In this paper we study quantum communication channels with correlated noise effects, i.e., quantum channels with memory. We derive a model for correlated noise channels that includes a channel memory state. We examine the case where the memory is finite, and derive bounds on the classical and quantum capacities. For the entanglement-assisted and unassisted classical capacities it is shown that these bounds are attainable for certain classes of channel. Also, we show that the structure of any finite memory state is unimportant in the asymptotic limit, and specifically, for a perfect finite-memory channel where no information is lost to the environment, the channel is asymptotically noiseless.

  6. The development of the Spanish verb ir into auxiliary of voice

    DEFF Research Database (Denmark)

    Vinther, Thora

    2005-01-01

    spanish, syntax, grammaticalisation, past participle, passive voice, middle voice, language development......spanish, syntax, grammaticalisation, past participle, passive voice, middle voice, language development...

  7. Objective Voice Parameters in Colombian School Workers with Healthy Voices

    Directory of Open Access Journals (Sweden)

    Lady Catherine Cantor Cutiva

    2015-09-01

    Full Text Available Objectives: To characterize the objective voice parameters among school workers, and to identi­fy associated factors of three objective voice parameters, namely fundamental frequency, sound pressure level and maximum phonation time. Materials and methods: We conducted a cross-sectional study among 116 Colombian teachers and 20 Colombian non-teachers. After signing the informed consent form, participants filled out a questionnaire. Then, a voice sample was recorded and evaluated perceptually by a speech therapist and by objective voice analysis with praat software. Short-term environmental measurements of sound level, temperature, humi­dity, and reverberation time were conducted during visits at the workplaces, such as classrooms and offices. Linear regression analysis was used to determine associations between individual and work-related factors and objective voice parameters. Results: Compared with men, women had higher fundamental frequency (201 Hz for teachers and 209 for non-teachers vs. 120 Hz for teachers and 127 for non-teachers and sound pressure level (82 dB vs. 80 dB, and shorter maximum phonation time (around 14 seconds vs. around 16 seconds. Female teachers younger than 50 years of age evidenced a significant tendency to speak with lower fundamental frequen­cy and shorter mpt compared with female teachers older than 50 years of age. Female teachers had significantly higher fundamental frequency (66 Hz, higher sound pressure level (2 dB and short phonation time (2 seconds than male teachers. Conclusion: Female teachers younger than 50 years of age had significantly lower F0 and shorter mpt compared with those older than 50 years of age. The multivariate analysis showed that gender was a much more important determinant of variations in F0, spl and mpt than age and teaching occupation. Objectively measured temperature also contributed to the changes on spl among school workers.

  8. Playful Interaction with Voice Sensing Modular Robots

    DEFF Research Database (Denmark)

    Heesche, Bjarke; MacDonald, Ewen; Fogh, Rune

    2013-01-01

    This paper describes a voice sensor, suitable for modular robotic systems, which estimates the energy and fundamental frequency, F0, of the user’s voice. Through a number of example applications and tests with children, we observe how the voice sensor facilitates playful interaction between...... children and two different robot configurations. In future work, we will investigate if such a system can motivate children to improve voice control and explore how to extend the sensor to detect emotions in the user’s voice....

  9. VOICE QUALITY BEFORE AND AFTER THYROIDECTOMY

    Directory of Open Access Journals (Sweden)

    Dora CVELBAR

    2016-04-01

    Full Text Available Introduction: Voice disorders are a well-known complication which is often associated with thyroid gland diseases and because voice is still the basic mean of communication it is very important to maintain its quality healthy. Objectives: The aim of this study referred to questions whether there is a statistically significant difference between results of voice self-assessment, perceptual voice assessment and acoustic voice analysis before and after thyroidectomy and whether there are statistically significant correlations between variables of voice self-assessment, perceptual assessment and acoustic analysis before and after thyroidectomy. Methods: This scientific research included 12 participants aged between 41 and 76. Voice self-assessment was conducted with the help of Croatian version of Voice Handicap Index (VHI. Recorded reading samples were used for perceptual assessment and later evaluated by two clinical speech and language therapists. Recorded samples of phonation were used for acoustic analysis which was conducted with the help of acoustic program Praat. All of the data was processed through descriptive statistics and nonparametric statistical methods. Results: Results showed that there are statistically significant differences between results of voice self-assessments and results of acoustic analysis before and after thyroidectomy. Statistically significant correlations were found between variables of perceptual assessment and acoustic analysis. Conclusion: Obtained results indicate the importance of multidimensional, preoperative and postoperative assessment. This kind of assessment allows the clinician to describe all of the voice features and provides appropriate recommendation for further rehabilitation to the patient in order to optimize voice outcomes.

  10. Beyond Insularity: Releasing the Voices.

    Science.gov (United States)

    Greene, Maxine

    1993-01-01

    Aspects of English-as-a-Second-Language are discussed from the standpoint of a teacher-educator with a particular interest in philosophy, the arts, and humanities and what they signify for the schools. The idea of giving voice to all viewpoints and sociocultural circumstances is considered for content learning and heterogeneous grouping. (Contains…

  11. A voice and nothing more

    DEFF Research Database (Denmark)

    Mebus, Andreas Nozic Lindgren

    2012-01-01

    Andreas Mebus fokuserer herefter på et helt konkret aspekt af talen, nemlig ”stemmen” i sin artikel ”A voice and nothing more – en filosofisk udredning af stemmen”. Gennem Mladen Dolars teori om stemmen, redegør Mebus for de forskellige aspekter ved stemmen; som bærer af mening, som æstetisk...

  12. Voice, Citizenship, and Civic Action

    DEFF Research Database (Denmark)

    Tufte, Thomas

    2014-01-01

    In recent years the world has experienced a resurgence in practices of bottom-up communication for social change, a plethora of agency in which claims for voice and citizenship through massive civic action have conquered center stage in the public debate. This resurgence has sparked a series...

  13. FILTWAM and Voice Emotion Recognition

    NARCIS (Netherlands)

    Bahreini, Kiavash; Nadolski, Rob; Westera, Wim

    2014-01-01

    This paper introduces the voice emotion recognition part of our framework for improving learning through webcams and microphones (FILTWAM). This framework enables multimodal emotion recognition of learners during game-based learning. The main goal of this study is to validate the use of microphone d

  14. The Performing Voice of Radio

    DEFF Research Database (Denmark)

    Lawaetz, Anna

    The ongoing international development of opening media archives for researchers as well as for broader audiences calls for a closer discussion of the mediated voice and how to analyse it. Which parameters can be analysed and which parameters are not covered by the analysis? Furthermore, how do we...

  15. Voice and choice by delegation

    NARCIS (Netherlands)

    van de Bovenkamp, H.; Vollaard, H.; Trappenburg, M.; Grit, K

    2013-01-01

    In many Western countries, options for citizens to influence public services are increased to improve the quality of services and democratize decision making. Possibilities to influence are often cast into Albert Hirschman's taxonomy of exit (choice), voice, and loyalty. In this article we identify

  16. Work-related voice disorder

    Directory of Open Access Journals (Sweden)

    Paulo Eduardo Przysiezny

    2015-04-01

    Full Text Available INTRODUCTION: Dysphonia is the main symptom of the disorders of oral communication. However, voice disorders also present with other symptoms such as difficulty in maintaining the voice (asthenia, vocal fatigue, variation in habitual vocal fundamental frequency, hoarseness, lack of vocal volume and projection, loss of vocal efficiency, and weakness when speaking. There are several proposals for the etiologic classification of dysphonia: functional, organofunctional, organic, and work-related voice disorder (WRVD.OBJECTIVE: To conduct a literature review on WRVD and on the current Brazilian labor legislation.METHODS: This was a review article with bibliographical research conducted on the PubMed and Bireme databases, using the terms "work-related voice disorder", "occupational dysphonia", "dysphonia and labor legislation", and a review of labor and social security relevant laws.CONCLUSION: WRVD is a situation that frequently is listed as a reason for work absenteeism, functional rehabilitation, or for prolonged absence from work. Currently, forensic physicians have no comparative parameters to help with the analysis of vocal disorders. In certain situations WRVD may cause, work disability. This disorder may be labor-related, or be an adjuvant factor to work-related diseases.

  17. The Performing Voice of Radio

    DEFF Research Database (Denmark)

    Lawaetz, Anna

    The ongoing international development of opening media archives for researchers as well as for broader audiences calls for a closer discussion of the mediated voice and how to analyse it. Which parameters can be analysed and which parameters are not covered by the analysis? Furthermore, how do we...

  18. Adolescent Leadership: The Female Voice

    Science.gov (United States)

    Archard, Nicole

    2013-01-01

    This research investigated the female adolescent view of leadership by giving voice to student leaders through focus group discussions. The questions: What is leadership? Where/how was leadership taught?, and How was leadership practised? were explored within the context of girls' schools located in Australia, with one school located in South…

  19. FILTWAM and Voice Emotion Recognition

    NARCIS (Netherlands)

    Bahreini, Kiavash; Nadolski, Rob; Westera, Wim

    2014-01-01

    This paper introduces the voice emotion recognition part of our framework for improving learning through webcams and microphones (FILTWAM). This framework enables multimodal emotion recognition of learners during game-based learning. The main goal of this study is to validate the use of microphone

  20. Voicing children's critique and utopias

    DEFF Research Database (Denmark)

    Husted, Mia; Lind, Unni

    2016-01-01

    , designed to accommodate children's participation through graphic illustrations of young children's critique and utopias. The study is informed by a commitment to democratic participation and processes (Reason and Bradbury 2001, Gunnarsson et al. 2016). Ethical guidelines implied dialogues and discussions......, children's voice, critique and utopias, pedagogical work...

  1. Women's Voices in Experiential Education.

    Science.gov (United States)

    Warren, Karen, Ed.

    This book is a collection of feminist analyses of various topics in experiential education, particularly as it applies to outdoors and adventure education, as well as practical examples of how women's experiences can contribute to the field as a whole. Following an introduction, "The Quilt of Women's Voices" (Maya Angelou), the 25…

  2. Minimum output entropy of Gaussian channels

    CERN Document Server

    Lloyd, S; Maccone, L; Pirandola, S; Garcia-Patron, R

    2009-01-01

    We show that the minimum output entropy for all single-mode Gaussian channels is additive and is attained for Gaussian inputs. This allows the derivation of the channel capacity for a number of Gaussian channels, including that of the channel with linear loss, thermal noise, and linear amplification.

  3. Temporal voice areas exist in autism spectrum disorder but are dysfunctional for voice identity recognition

    Science.gov (United States)

    Borowiak, Kamila; von Kriegstein, Katharina

    2016-01-01

    The ability to recognise the identity of others is a key requirement for successful communication. Brain regions that respond selectively to voices exist in humans from early infancy on. Currently, it is unclear whether dysfunction of these voice-sensitive regions can explain voice identity recognition impairments. Here, we used two independent functional magnetic resonance imaging studies to investigate voice processing in a population that has been reported to have no voice-sensitive regions: autism spectrum disorder (ASD). Our results refute the earlier report that individuals with ASD have no responses in voice-sensitive regions: Passive listening to vocal, compared to non-vocal, sounds elicited typical responses in voice-sensitive regions in the high-functioning ASD group and controls. In contrast, the ASD group had a dysfunction in voice-sensitive regions during voice identity but not speech recognition in the right posterior superior temporal sulcus/gyrus (STS/STG)—a region implicated in processing complex spectrotemporal voice features and unfamiliar voices. The right anterior STS/STG correlated with voice identity recognition performance in controls but not in the ASD group. The findings suggest that right STS/STG dysfunction is critical for explaining voice recognition impairments in high-functioning ASD and show that ASD is not characterised by a general lack of voice-sensitive responses. PMID:27369067

  4. Frame-bitrate-change based steganography for voice-over-IP

    Institute of Scientific and Technical Information of China (English)

    刘进; 田晖; 周可

    2014-01-01

    Steganography based on bits-modification of speech frames is a kind of commonly used method, which targets at RTP payloads and offers covert communications over voice-over-IP (VoIP). However, direct modification on frames is often independent of the inherent speech features, which may lead to great degradation of speech quality. A novel frame-bitrate-change based steganography is proposed in this work, which discovers a novel covert channel for VoIP and introduces less distortion. This method exploits the feature of multi-rate speech codecs that the practical bitrate of speech frame is identified only by speech decoder at receiving end. Based on this characteristic, two steganography strategies called bitrate downgrading (BD) and bitrate switching (BS) are provided. The first strategy substitutes high bit-rate speech frames with lower ones to embed secret message, which introduces very low distortion in practice, and much less than other bits-modification based methods with the same embedding capacity. The second one encodes secret message bits into different types of speech frames, which is an alternative choice for supplement. The two strategies are implemented and tested on our covert communication system StegVoIP. The experiment results show that our proposed method is effective and fulfills the real-time requirement of VoIP communication.

  5. Carrying Capacity

    DEFF Research Database (Denmark)

    Schroll, Henning; Andersen, Jan; Kjærgård, Bente

    2012-01-01

    A spatial planning act was introduced inIndonesia 1992 and renewed in 2008. It emphasised the planning role of decentralised authorities. The spatial planning act covers both spatial and environmental issues. It defines the concept of carrying capacity and includes definitions of supportive...... and ACC may increase the political focus on resources and environmental issues and may help to move local authorities towards a more holistic spatial planning approach. A carrying capacity approach could be an inspiration for local spatial planning in developing countries. A spatial planning act...... was introduced inIndonesia 1992 and renewed in 2008. It emphasised the planning role of decentralised authorities. The spatial planning act covers both spatial and environmental issues. It defines the concept of carrying capacity and includes definitions of supportive carrying capacity (SCC) and assimilative...

  6. Covert channel detection using Information Theory

    CERN Document Server

    Hélouët, Loïc; 10.4204/EPTCS.51.3

    2011-01-01

    This paper presents an information theory based detection framework for covert channels. We first show that the usual notion of interference does not characterize the notion of deliberate information flow of covert channels. We then show that even an enhanced notion of "iterated multivalued interference" can not capture flows with capacity lower than one bit of information per channel use. We then characterize and compute the capacity of covert channels that use control flows for a class of systems.

  7. Covert channel detection using Information Theory

    Directory of Open Access Journals (Sweden)

    Loïc Hélouët

    2011-02-01

    Full Text Available This paper presents an information theory based detection framework for covert channels. We first show that the usual notion of interference does not characterize the notion of deliberate information flow of covert channels. We then show that even an enhanced notion of "iterated multivalued interference" can not capture flows with capacity lower than one bit of information per channel use. We then characterize and compute the capacity of covert channels that use control flows for a class of systems.

  8. Sparking Passion: Engaging Student Voice through Project-Based Learning in Learning Communities

    Science.gov (United States)

    Ball, Christy L.

    2016-01-01

    How do we confront entrenched educational practices in higher education that lead to student demotivation, poor retention, and low persistence? This article argues that project-based learning that situates student voice and capacity at the center of culturally-responsive curriculum has the potential to spark student passion for problem-solving…

  9. Comparing acoustic and perceptual voice parameters in female teachers based on voice complaints

    Directory of Open Access Journals (Sweden)

    Maryam Faghani Abukeili

    2014-04-01

    Full Text Available Background and Aim: Teachers are a large group of professional voice users that several risk factors and voice demands causes various voice complaints among them. As the voice is multidimensional, the aim of this study was acoustic and perceptual measurement of teachers’ voice and comparing the findings between two groups with many and few voice complaints.Methods: Sixty female teachers of high school in Sari, north of Iran, were chosen by available sampling to participate in this cross-sectional study. According to a voice complaints questionnaire, 21 subjects located in few voice complaints and 31 in many voice complaints group. After a working day, subjects completed a voice self-assessment questionnaire. Also, teachers’voice were recorded during three tasks including sustained vowels /a/ and /i/, text reading and conversational speech. Acoustic parameters were analyzed by Praat software and 2 speech-language pathalogists performed auditory-perceptual assessment by GRBAS ( Grade, Roughness, Breathiness, Asthenia, Strain scale. Results: Comparing of the voice self-assessment between the two groups demonstrated statistically significant difference (p<0.05; however results of the acoustic and auditory-perceptual measurement did not show significant diffrence.Conclusion: Despite prevalent voice problems in teachers, there are various conditions in terms of complaints and assessments methods. In this study, only a remarkable deviation documented in the client-based assessments in many voice compliants group in comparison with few voice compliants, which would be probably related to different individual’s perception of voice problem between two groups. These results support paying attention to self-assessments in clinical process of voice problems.

  10. The Role of Occupational Voice Demand and Patient-Rated Impairment in Predicting Voice Therapy Adherence.

    Science.gov (United States)

    Ebersole, Barbara; Soni, Resha S; Moran, Kathleen; Lango, Miriam; Devarajan, Karthik; Jamal, Nausheen

    2017-07-11

    Examine the relationship among the severity of patient-perceived voice impairment, perceptual dysphonia severity, occupational voice demand, and voice therapy adherence. Identify clinical predictors of increased risk for therapy nonadherence. A retrospective cohort study of patients presenting with a chief complaint of persistent dysphonia at an interdisciplinary voice center was done. The Voice Handicap Index-10 (VHI-10) and the Voice-Related Quality of Life (V-RQOL) survey scores, clinician rating of dysphonia severity using the Grade score from the Grade, Roughness Breathiness, Asthenia, and Strain scale, occupational voice demand, and patient demographics were tested for associations with therapy adherence, defined as completion of the treatment plan. Classification and Regression Tree (CART) analysis was performed to establish thresholds for nonadherence risk. Of 166 patients evaluated, 111 were recommended for voice therapy. The therapy nonadherence rate was 56%. Occupational voice demand category, VHI-10, and V-RQOL scores were the only factors significantly correlated with therapy adherence (P occupational voice demand are significantly more likely to be nonadherent with therapy than those with high occupational voice demand (P 40 is a significant cutoff point for predicting therapy nonadherence (P Occupational voice demand and patient perception of impairment are significantly and independently correlated with therapy adherence. A VHI-10 score of ≤9 or a V-RQOL score of >40 is a significant cutoff point for predicting nonadherence risk. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  11. Limited feedback achieves the empirical capacity

    CERN Document Server

    Eswaran, Krishnan; Sahai, Anant; Gastpar, Michael

    2007-01-01

    The utility of limited feedback for coding over an individual sequence of DMCs is investigated. This study complements recent results showing how limited or noisy feedback can boost the reliability of communication. A strategy with fixed input distribution $P$ is given that asymptotically achieves rates arbitrarily close to the mutual information induced by $P$ and the state-averaged channel. When the capacity achieving input distribution is the same over all channel states, this achieves rates at least as large as the capacity of the state averaged channel, sometimes called the empirical capacity.

  12. Perturbation Measures of Voice: A Comparative Study between Multi-Dimensional Voice Program and Praat

    National Research Council Canada - National Science Library

    Maryn, Youri; Corthals, Paul; De Bodt, Marc; Van Cauwenberge, Paul; Deliyski, Dimitar

    2009-01-01

    .... In the present study, perturbation measures provided by two computer systems (a purpose-built professional voice analysis apparatus and a personal computer-based system for acoustic voice assessment...

  13. [The smokers voice self assessment based on Voice Handicap Index (VHI)].

    Science.gov (United States)

    Wiskirska-Woźnica, Bozena; Wojnowski, Waldemar

    2009-01-01

    Complex voice assessment due to European Laryngeal Society proposals (2000) contains voice self estimation based on the Polish version of the Voice Handicap Index (VHI). This study focuses on the relation between voice handicap and smoking in dysphonic patients, who are using voice professionally. Thirty outpatient (25 female and 5 male, aged 40 to 55 years) voice department attendees suffering from professional dysphonia took part in this study. All patients after phoniatric examination completed the Polish version of the Voice Handicap Index (VHI). The questions concern functional, emotional and physical complains due to dysphonia. Most of smokers did not complain of dysphonia related problems comparing to non smokers. Even the scores of functional and emotional scales of VHI in smokers shown better results (less handicap) than in nonsmokers. Smoking does not affect patients handicap due to dysphonia measured in the Voice Handicap Index.

  14. Qos and Voice Over IP

    Directory of Open Access Journals (Sweden)

    Adrian GHENCEA

    Full Text Available As Voice over Internet Protocol (VoIP technology matures, companies are increasingly adopting it to cut costs, improve efficiency and enhance customer service. Using the Internet as an existing network for integrating data and telecom systems through intelligent VoIP, a range of benefits results: lower long distance costs, cost cuts in cabling processes and more flexible telephony management. However, as voice over IP services grow in popularity, major threats arise: this rapid growth leads to traffic congestion, security is jeopardizedand the poor quality of calls affects communication. The objective of this article is to present all the elements that can affect voicequality in a VoIP network and to provide methods for solving them. A detailed analysis to minimize the impact of implementation of QoS will be made, and at the end solutions to management strategies will be proposed.

  15. Effect of Religiosity on Voice.

    Science.gov (United States)

    Hamdan, Abdul-Latif; Khneisser, Gebran; Dowli, Alex; Ziade, Georges; Tamim, Hani

    2017-04-01

    The aim of this study was to examine the relationship between religiosity and phonatory behavior. A total of 186 participants participated in a survey that included four sections: demographic data, extent of religiosity, history of dysphonia, phonatory behavior and laryngeal manipulation, in addition to the Voice Handicap Index (VHI-10). There was no significant association between the prevalence of phonatory symptoms and any of the religiosity questions. There was no significant association between phonatory behavior, history of laryngeal manipulation and any of the religiosity questions. There was also no significant association between the score of the Voice Handicap Index and any of the five religiosity questions. There is no association between religiosity and prevalence of phonatory disturbances, phonotraumatic behavior and/or history of laryngeal manipulation.

  16. Voice disorders in mucosal leishmaniasis.

    Directory of Open Access Journals (Sweden)

    Ana Cristina Nunes Ruas

    Full Text Available INTRODUCTION: Leishmaniasis is considered as one of the six most important infectious diseases because of its high detection coefficient and ability to produce deformities. In most cases, mucosal leishmaniasis (ML occurs as a consequence of cutaneous leishmaniasis. If left untreated, mucosal lesions can leave sequelae, interfering in the swallowing, breathing, voice and speech processes and requiring rehabilitation. OBJECTIVE: To describe the anatomical characteristics and voice quality of ML patients. MATERIALS AND METHODS: A descriptive transversal study was conducted in a cohort of ML patients treated at the Laboratory for Leishmaniasis Surveillance of the Evandro Chagas National Institute of Infectious Diseases-Fiocruz, between 2010 and 2013. The patients were submitted to otorhinolaryngologic clinical examination by endoscopy of the upper airways and digestive tract and to speech-language assessment through directed anamnesis, auditory perception, phonation times and vocal acoustic analysis. The variables of interest were epidemiologic (sex and age and clinic (lesion location, associated symptoms and voice quality. RESULTS: 26 patients under ML treatment and monitored by speech therapists were studied. 21 (81% were male and five (19% female, with ages ranging from 15 to 78 years (54.5+15.0 years. The lesions were distributed in the following structures 88.5% nasal, 38.5% oral, 34.6% pharyngeal and 19.2% laryngeal, with some patients presenting lesions in more than one anatomic site. The main complaint was nasal obstruction (73.1%, followed by dysphonia (38.5%, odynophagia (30.8% and dysphagia (26.9%. 23 patients (84.6% presented voice quality perturbations. Dysphonia was significantly associated to lesions in the larynx, pharynx and oral cavity. CONCLUSION: We observed that vocal quality perturbations are frequent in patients with mucosal leishmaniasis, even without laryngeal lesions; they are probably associated to disorders of some

  17. WHEEL CHAIR USING VOICE RECOGNITION

    OpenAIRE

    Manish Kumar Yadav*; Rajat Kumar; Santosh Yadav; Ravindra Prajapati; Prof. Kshirsagar

    2016-01-01

    The wide spread prevalence of lost limbs and sensing system is of major concern in present day due to wars, accident, age and health problems. This Omni-directional wheelchair was designed for the less able elderly to move more flexibly in narrow spaces, such as elevators or small aisle. The wheelchair is developed to help disabled patients by using speech recognition system to control the movement of wheelchair in different directions by using voice commands and also the simple movement of t...

  18. English Spoken Language & Voice Quality

    OpenAIRE

    Folsberg, Jens; Nielsen, Charlotte; Brusokaite, Giedre; Beinkamp, Line; Bach Jensen, Niels; Aalbæk Jensen, Sandra

    2013-01-01

    This project investigates the way language and accents are depicted in animated features and how linguistic stereotypes can be used in the process of character construction. In order to look into that, examples from four movies, produced by two studios, have been selected; the American Disney studios being represented by The Lion King (1994) and Up (2009), and the Japanese Studio Ghibli being represented by Ponyo (2008) and Howl's Moving Castle (2004). Voice qualities and specific accents ...

  19. Tracheostomy cannulas and voice prosthesis

    OpenAIRE

    2011-01-01

    Cannulas and voice prostheses are mechanical aids for patients who had to undergo tracheotomy or laryngectomy for different reasons. For better understanding of the function of those artificial devices, first the indications and particularities of the previous surgical intervention are described in the context of this review. Despite the established procedure of percutaneous dilatation tracheotomy e.g. in intensive care units, the application of epithelised tracheostomas has its own position,...

  20. The voice of the voiceless

    Directory of Open Access Journals (Sweden)

    Carlos Morales

    2014-12-01

    Full Text Available Women’s voice, these are stories of a group of women and their partners who lived part of a particular historical period agriculture during the twentieth century, the hacienda. The present work attempts to reflect their everyday life, reinterpreted from nowadays as a reflection of collective memory, in the big farms where they grew by putting in scene their roles in juxtaposition to the roles of male tradition.