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source-channel-cooperation tradeoffs for adaptive coded communications

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第9期7卷 3347-3358页

作者： Kwasinski, Andres Liu, K. J. Ray Rochester Inst Technol Rochester NY 14623 USA Univ Maryland College Pk MD 20742 USA

Transmit power limitations and quality-impairing channels present key challenges to wireless communications. A possible solution to these problems is the application of user-cooperation techniques so as to improve link quality. This paper studies the tradeoffs involved in combining user cooperation with practical source and channel coding in systems featuring rate-adaptive source and channel coding of conversational traffic. Performance is measured through the D-SNR curve, which measures the relation between end-to-end distortion and channel Signal-to-Noise Ratio (SNR). The D-SNR curve is accurately characterized as a linear function in log-log scales. Also, it is shown that the tradeoffs;involved in combining amplify-and-forward or decode-and-forward cooperation with source and channel coding translates into cooperative schemes showing a decrease in distortion at approximately half the rate as noncooperative schemes but with larger coding gain. Because of this, the studied non-cooperative schemes show better performance only at high SNR. In addition, the D-SNR characterization is used to compare amplify-and-forward and decode-and-forward cooperation for channel codes of different strength and to study the effects of source codec efficiency, where it is shown that diversity gain is reduced proportionally to the source codec loss of efficiency.

关键词： cooperative communications source coding channel coding joint source-channel coding

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Minimum Distortion Network Code Design for source coding Over Noisy channels

Minimum Distortion Network Code Design for Source Coding Ove...

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19th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications

作者： Park, Moonseo Kim, Seong-Lyun Yonsei Univ Sch Elect & Elect Engn Radio Resource Management & Optimizat Lab Seoul 120749 South Korea

ISBN: (纸本)9781424426430

The XOR network code is widely used in the conventional network coding. However, when the channel is noisy, the XOR code is suboptimal in terms of minimizing distortion in the source signal. We propose to use a new network code for the two-way relay channel, designed to minimize signal distortion due to the channel noise. We assume the source signal X is encoded by a source encoder and the sequence of symbols is transmitted over the two-way relay channel with noise. The received sequence of symbols may be corrupted by the channel noise, and X, the estimation of X, may be different from X. We design a new network code which minimizes the distortion between X and X. To provide an algorithm to obtain a network code with minimum distortion, we define the expected distortion associated with a network code. Starting with the XOR network code, we iteratively optimize the network code to obtain smaller expected distortion, while maintaining the Latin square constraint of the network code. New network code achieves substantial performance gain over the XOR network code.

关键词： Index assignment joint source-channel coding Latin square network coding

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Successive refinement via broadcast: Optimizing expected distortion of a Gaussian source over a Gaussian fading channel

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IEEE TRANSACTIONS ON INFORMATION THEORY 2008年第7期54卷 2903-2918页

作者： Tian, Chao Steiner, Avi Shamai (Shitz), Shlomo Diggavi, Suhas N. Ecole Polytech Fed Lausanne Sch Comp & Commun Sci CH-1015 Lausanne Switzerland Technion Israel Inst Technol Dept Elect Engn IL-32000 Haifa Israel

We consider the problem of transmitting a Gaussian source on a slowly fading Gaussian channel, subject to the mean-squared error distortion measure. The channel state information is known only at the receiver but not at the transmitter. The source is assumed to be encoded in a successive refinement (SR) manner, and then transmitted over the channel using the broadcast strategy. In order to minimize the expected distortion at the receiver, optimal power allocation is essential. We propose an efficient algorithm to compute the optimal solution in linear time O (M), when the total number of possible discrete fading states is M. Moreover, we provide a derivation of the optimal power allocation when the fading state is a continuum, using the classical variational method. The proposed algorithm as well as the continuous solution is based on an alternative representation of the capacity region of the Gaussian broadcast channel.

关键词： broadcast strategy joint source-channel coding power allocation successive refinement (SR)

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State amplification

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IEEE TRANSACTIONS ON INFORMATION THEORY 2008年第5期54卷 1850-1859页

作者： Kim, Young-Han Sutivong, Arak Cover, Thomas M. Stanford Univ Dept Elect Engn Stanford CA 94305 USA Stanford Univ Dept Stat Stanford CA 94305 USA

We consider the problem of transmitting data at rate R over a state-dependent channel p (y vertical bar x, s) with state information available at the sender and at the same time conveying the information about the channel state itself to the receiver. The amount of state information that can be learned at the receiver is captured by the mutual information I(S-n;Y-n) between the state sequence S-n and the channel output Y-n. The optimal tradeoff is characterized between the information transmission rate R and the state uncertainty reduction rate Delta, when the state information is either causally or noncausally available at the sender. In particular, when state transmission is the only goal, the maximum uncertainty reduction rate is given by Delta* = max(p(x vertical bar s)) I(X S;Y). This result is closely related and in a sense dual to a recent study by Merhav and Shamai, which solves the problem of masking the state information from the receiver rather than conveying it.

关键词： capacity causal state information channels with state information joint source-channel coding noncausal state information state amplification state uncertainty reduction writing on dirty paper

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On successive refinement with causal side information at the decoders

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IEEE TRANSACTIONS ON INFORMATION THEORY 2008年第1期54卷 332-343页

作者： Maor, Alina Merhav, Neri Technion Israel Inst Technol Dept Elect Engn IL-32000 Haifa Israel

Consider a process, {X-i, Y-i, Z(i)}(i=1)(infinity) producing independent copies of a triplet of jointly distributed random variables (RVs). The {X-i} I part of the process-the source-is observed at the encoder, and is supposed to be reproduced at two decoders, decoder 1 and decoder 2, where the {Z(i)} and the {Y-i} parts of the process are observed, respectively, in a causal manner. The communication between the encoder and the decoders is carried out across two memoryless channels in two successive communication stages. In the first stage, the compressed transmission is available to both decoders, but only decoder 1 reconstructs the source (according to the received data stream and its causal side information (SI){Z(i)}). In the second stage, the second decoder reconstructs the source according to {Y-i} and the transmissions of the encoder at both stages. It is desired to find necessary and sufficient conditions such that the distortions incurred (in each stage) will not exceed given thresholds. First, a single-letter characterization of achievable rates is derived for a pure source-coding problem with successive refinement and causal SI at the decoders. Then, for a joint source-channel coding setting, a separation theorem is proved, asserting that in the limit of long blocks, no optimality is lost by first applying lossy successive-refinement source coding, regardless of the channels, and then applying good channel codes to each one of the resulting bit streams, regardless of the source. Next, conditions for a source to be successively refinable in two different senses are established, and finally, it is shown that the binary-symmetric source is successively refinable.

关键词： causal rate distortion function channel capacity joint source-channel coding side information (SI) source-channel separation source coding successive refinement

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joint source-channel codes for MIMO block-fading channels

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IEEE TRANSACTIONS ON INFORMATION THEORY 2008年第1期54卷 116-134页

作者： Gunduz, Deniz Erkip, Elza Polytech Univ Dept Elect & Comp Engn Brooklyn NY 11201 USA Stanford Univ Dept Elect Engn Stanford CA 94305 USA

We consider transmission of a continuous amplitude source over an L-block Rayleigh-fading M-t x M-r, multiple-input multiple-output (MIMO) channel when the channel state information is only available at the receiver. Since the channel is not ergodic, Shannon's source-channel separation theorem becomes obsolete and the optimal performance requires a joint source-channel approach. Our goal is to minimize the expected end-to-end distortion, particularly in the high signal-to-noise ratio (SNR) regime. The figure of merit is the distortion exponent, defined as the exponential decay rate of the expected distortion with increasing SNR. We provide an upper bound and lower bounds for the distortion exponent with respect to the bandwidth ratio among the channel and source bandwidths. For the lower bounds, we analyze three different strategies based on layered source coding concatenated with progressive superposition or hybrid digital/analog transmission. In each case, by adjusting the system parameters we optimize the distortion exponent as a function of the bandwidth ratio. We prove that the distortion exponent upper bound can be achieved when the channel has only one degree of freedom, that is L = 1, and min {M-t, M-r} = 1. When we have more degrees of freedom, our achievable distortion exponents meet the upper bound for only certain ranges of the bandwidth ratio. We demonstrate that our results, which were derived for a complex Gaussian source, can be extended to more general source distributions as well.

关键词： broadcast codes distortion exponent diversity-multiplexing gain tradeoff hybrid digital/analog coding joint source-channel coding multiple-input multiple-output (MIMO) successive refinement

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Parity-check matrix calculation for paraunitary oversampled DFT filter banks

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2008年第10期56卷 5277-5283页

作者： Karp, Tanja Kieffer, Michel Duhamel, Pierre Texas Tech Univ Dept Elect & Comp Engn Lubbock TX 79409 USA Univ Paris 11 CNRS SUPELEC Lab Signaux & Syst F-91192 Gif Sur Yvette France

joint source-channel coding schemes based on oversampled filter banks were recently proposed. Oversampled filter banks are considered as error-correcting codes, extending the notion of code subspace, parity-check matrix, and syndrome to the domain of real and complex numbers. We here present an efficient calculation and implementation of the parity-check polynomial matrices for oversampled discrete Fourier transform (DFT) filter banks. If desired, the calculation of the parity-check polynomials can be performed as part of the prototype filter design procedure. We compare our method to those previously presented in the literature.

关键词： joint source-channel coding oversampled discrete Fourier transform (DFT) filter banks parity-check matrix

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A unified framework for layered transmission over fading and packet erasure channels

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IEEE TRANSACTIONS ON COMMUNICATIONS 2008年第4期56卷 565-573页

作者： Etemadi, Farzad Jafarkhani, Hamid Univ Calif Irvine Dept EECS Irvine CA 92717 USA

We consider layered transmission of a successively refinable source over a quasi-static fading channel. We establish a duality relationship between this problem and that of packet transmission over erasure channels and use it to share solution techniques in both domains. For a Gaussian source and the fading channel, a low-complexity, optimal algorithm is proposed, and it is shown that the corresponding dual for packet erasure channels has linear complexity as opposed to the quadratic complexity of the best known optimal algorithms in the literature. For non-Gaussian sources, the optimal rate allocation problem for fading channels is solved using the dual solution for erasure channels. It is also shown that a single-layer system is optimal for fading channels if the goal is to maximize the rate. Numerical results for multiple antenna Rayleigh fading channels are presented for Gaussian sources and practical image coders. It is shown that a few number of layers significantly improves the performance. Finally, we numerically show that for practical operating conditions, optimizing the asymptotic measure of distortion exponent is not enough when there are more than one transmit or receive antennas.

关键词： joint source-channel coding MIMO fading channels successive refinement packet erasure channels outage capacity

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Error-resilient video encoding and transmission in multirate wireless LANs

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IEEE TRANSACTIONS ON MULTIMEDIA 2008年第5期10卷 691-700页

作者： Argyriou, Antonios Philips Res Labs NL-5656 AE Eindhoven Netherlands

In this paper, we present a cross-layer approach for video transmission in wireless LANs that employs joint source and application-layer channel coding, together with rate adaptation at the wireless physical layer (PHY). While the purpose of adopting PHY rate adaptation in modern wireless LANs like the IEEE 802.11a/b is to maximize the throughput, in this paper we exploit this feature to increase the robustness of wireless video. More specifically, we investigate the impact of adapting the PHY transmission rate, thus changing the throughput and packet loss channel characteristics, on the rate-distortion performance of a transmitted video sequence. To evaluate the video quality at the decoder, we develop a cross-layer modeling framework that considers jointly the effect of application-layer joint source-channel coding (JSCC), error concealment, and the PHY transmission rate. The resulting models are used by an optimization algorithm that calculates the optimal JSCC allocation for each video frame, and PHY transmission rate for each outgoing transport packet. The comprehensive simulation results obtained with the H.264/AVC codec demonstrate considerable increase in the PSNR of the decoded video when compared with a system that employs separately JSCC and PHY rate adaptation. Furthermore, our performance analysis indicates that the optimal PHY transmission rate calculated by the proposed algorithm, can be significantly different when compared with rate adaptation algorithms that target throughput improvement.

关键词： cross-layer design joint source-channel coding rate-adaptive PHY real-time video encoding video streaming wireless LAN

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Uncoded Transmission Is Exactly Optimal for a Simple Gaussian "Sensor" Network

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IEEE TRANSACTIONS ON INFORMATION THEORY 2008年第11期54卷 5247-5251页

作者： Gastpar, Michael Univ Calif Berkeley Dept Elect Engn & Comp Sci Berkeley CA 94720 USA

A single memoryless Gaussian source is observed by many terminals, subject to independent Gaussian observation noises. The terminals are linked to a fusion center via a standard Gaussian multiple-access channel. The fusion center needs to recover the underlying Gaussian source with respect to mean-squared error. In this correspondence, a theorem of Witsenhausen is shown to imply that an optimal communication strategy is uncoded transmission, i.e., each terminal's channel input is merely a scaled version of its noisy observation.

关键词： Cut-set bound joint source-channel coding maximum correlation coefficient source-channel separation theorem

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