A new analog-digital hybrid coding architecture for joint source-channelcoding is proposed. The encoder generates a channel input by a symbol-by-symbol mapping of the observed (analog) source and its (digital) compre...
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ISBN:
(纸本)9781457705953
A new analog-digital hybrid coding architecture for joint source-channelcoding is proposed. The encoder generates a channel input by a symbol-by-symbol mapping of the observed (analog) source and its (digital) compression codeword, while the decoder reconstructs the source by a symbol-by-symbol mapping of the (analog) channel output and the decoded (digital) compression codeword from it. When applied to the problem of lossy communication of sources over the two-user discrete memoryless interference channel, this hybrid coding scheme achieves the best known performance and recovers as special cases several previous results on lossless and lossy communication over single hop networks.
Imperfect secrecy in communication systems is investigated. Instead of using equivocation as a measure of secrecy, the distortion that an eavesdropper incurs in producing an estimate of the source sequence is examined...
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ISBN:
(纸本)9781467345392;9781467345378
Imperfect secrecy in communication systems is investigated. Instead of using equivocation as a measure of secrecy, the distortion that an eavesdropper incurs in producing an estimate of the source sequence is examined. The communication system consists of a source and a broadcast (wiretap) channel, and lossless reproduction of the source sequence at the legitimate receiver is required. A key aspect of this model is that the eavesdropper's actions are allowed to depend on the past behavior of the system. Achievability results are obtained by studying the performance of source and channelcoding operations separately, and then linking them together digitally. Although the problem addressed here has been solved when the secrecy resource is shared secret key, it is found that substituting secret key for a wiretap channel brings new insights and challenges: the notion of weak secrecy provides just as much distortion at the eavesdropper as strong secrecy, and revealing public messages freely is detrimental.
We investigate whether uncoded schemes are optimal for Gaussian sources on multiuser Gaussian channels. Particularly, we consider two problems: the first is to send correlated Gaussian sources on a Gaussian broadcast ...
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ISBN:
(纸本)9781467377041
We investigate whether uncoded schemes are optimal for Gaussian sources on multiuser Gaussian channels. Particularly, we consider two problems: the first is to send correlated Gaussian sources on a Gaussian broadcast channel where each receiver is interested in reconstructing only one source component (or one specific linear function of the sources) under the mean squared error distortion measure;the second is to send correlated Gaussian sources on a Gaussian multiple-access channel, where each transmitter observes a noisy combination of the sources, and the receiver wishes to reconstruct the individual source components (or individual linear functions) under the mean squared error distortion measure. It is shown that when the channel parameters satisfy certain general conditions, the induced distortion tuples are on the boundary of the achievable distortion region, and thus optimal. Instead of following the conventional approach of attempting to characterize the achievable distortion region, we ask the question whether and how a match can be effectively determined. This decision problem formulation helps to circumvent the difficult optimization problem often embedded in region characterization problems, and it also leads us to focus on the critical conditions in the outer bounds that make the inequalities become equalities, which effectively decouple the overall problem into several simpler sub-problems. Optimality results previously unknown in the literature are obtained using this novel approach. Explicit and novel outer bounds are derived for the two problems as the byproducts of our investigation.
In this paper we propose an energy-aware scheme using joint source-channelcoding (JSCC) with unequal error protection (UEP) for scalable video delivery over packet-lossy networks. The proposed cross-layer approach jo...
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ISBN:
(纸本)9781479903085
In this paper we propose an energy-aware scheme using joint source-channelcoding (JSCC) with unequal error protection (UEP) for scalable video delivery over packet-lossy networks. The proposed cross-layer approach jointly consider the error protection at the physical layer, the energy consumption at the MAC layer, and the quality of service (QoS) at the application layer. Bits are optimally allocated based on the source compression and the channel correction coding, in accordance to both the wireless channel conditions and the energy constraints. For a certain intra refreshing rate of sourcecoding, the UEP scheme is capable of optimally allocating the channel redundancy among frames, with the lowest video distortion and energy consumption in wireless transmission. Simulations demonstrate that the proposed energy-aware JSCC scheme can significantly improve the video QoS, while the energy constraint is satisfied and the complexity associated with performing the cross-layer JSCC grouping algorithm is acceptable.
We investigate the performance of bandwidth expansion analog joint source-channelcoding (JSCC) over fading channels. Non-linear spiral-like curves and maximum likelihood detector with linear minimum mean square error...
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ISBN:
(纸本)9781479914814
We investigate the performance of bandwidth expansion analog joint source-channelcoding (JSCC) over fading channels. Non-linear spiral-like curves and maximum likelihood detector with linear minimum mean square error estimator are considered. Under Rayleigh fading this scheme presents a gap to the theoretical limit which increases with the channel signal to noise ratio (CSNR), while the same scheme on additive white Gaussian noise (AWGN) channel presents much smaller gap. This is completely different from bandwidth compression, where the performance in both fading and AWGN channels is close to optimal. We present two strategies that can make bandwidth expansion analog JSCC more feasible: channel inversion and receive diversity. The first requires channel state information at the transmitter, while the second does not. Both strategies are shown to considerably reduce the gap to the theoretical limit.
The problem of secure lossy source-channel wiretapping with arbitrarily correlated side informations at both receivers is investigated. This scenario consists of an encoder (referred to as Alice) that wishes to compre...
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ISBN:
(纸本)9781457705953
The problem of secure lossy source-channel wiretapping with arbitrarily correlated side informations at both receivers is investigated. This scenario consists of an encoder (referred to as Alice) that wishes to compress a source and send it through a noisy channel to a legitimate receiver (referred to as Bob). In this context, Alice must simultaneously satisfy the desired requirements on the distortion level at Bob, and the equivocation rate at the eavesdropper (referred to as Eve). This setting can be seen as a generalization of the conventional problems of secure sourcecoding with side information at the decoders, and the wiretap channel. Inner and outer bounds on the rate-distortion-equivocation region for the case of arbitrary channels and side informations are derived. In some special cases of interest, it is shown that separation holds. By means of an appropriate coding, the presence of any statistical difference among the side informations, the channel noises, and the distortion at Bob can be fully exploited in terms of secrecy.
Shannon's capacity and rate-distortion function, combined with the separation principle, provide tight bounds for the minimum possible distortion in joint source-channelcoding. These bounds, however, are usually ...
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ISBN:
(纸本)9781457705953
Shannon's capacity and rate-distortion function, combined with the separation principle, provide tight bounds for the minimum possible distortion in joint source-channelcoding. These bounds, however, are usually achievable only in the limit of large block length. In their 1973 paper, Ziv and Zakai provide a family of alternative capacity and rate-distortion functions, based on functionals satisfying the data-processing inequality, which potentially give tighter bounds for systems with a small block length, e.g., for scalar modulation. We examine a recently proposed approximation for the Ziv-Zakai bounds based on the Renyi-divergence functional. For the specific case of a uniform source, we derive explicit bounds on the Ziv-Zakai-Renyi rate-distortion function, which prove this approximation in the limit of small distortion. Our results can be extended, using the same technique, to more general sources.
A new distributed joint source-channel code (DJSCC) is proposed for a communication network with spatial-temporally correlated Markov sources. The DJSCC is performed by puncturing the information bits of a systematic ...
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ISBN:
(纸本)9781467331227
A new distributed joint source-channel code (DJSCC) is proposed for a communication network with spatial-temporally correlated Markov sources. The DJSCC is performed by puncturing the information bits of a systematic linear block code but leaving the parity bits intact, and transmitting the information and parity bits with unequal energy allocations. At the receiver, the spatial data correlation is exploited with a new multi-codeword message passing (MCMP) decoding algorithm. The MCMP decoder performs decoding by exchanging information between codewords from correlated sources, whereas conventional message passing (MP) algorithms exchanges soft information only inside a codeword. The inter-codeword soft information exchange of MCMP yields additional performance gains over the MP algorithm. In recognition that the signals at the receiver arc distorted observations of the Markov source and thus can be modeled by a hidden Markov model (HMM), we propose to exploit the temporal data correlation by adding a HMM decoding module to the MCMP decoder. The HMM decoder iteratively exchanges soft information with the MCMP decoder, and this results in significant performance gains over conventional systems.
In this paper, we develop a new technique for partitioning of source and channelcoding bits for packet-based scalable streams and a general unequal error protection channelcoding scheme. Unlike the previous algorith...
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ISBN:
(纸本)9781424488650
In this paper, we develop a new technique for partitioning of source and channelcoding bits for packet-based scalable streams and a general unequal error protection channelcoding scheme. Unlike the previous algorithms, we regard coded source streams as a collection of different subsets with different importance and adaptively select some of them to transmit with optimal channelcoding subject to channel status. Both packets extraction strategy and forward error correction coding(FEC) assignment are considered in the joint sourcechannelcoding problem. We propose a double hill climbing method and two simplified algorithms to solve the mixed optimization problem. To validate the algorithms, we exploit the scalability of H.264 scalable video coding (SVC) and derive a simple yet accurate loss distortion model for simulation. The results show that the new algorithms with extraction strategy result in less expected distortion than others with all source packets transmitted. It is also shown that the simplified algorithms with very low complexity are also appealing and can achieve near-optimal performance.
In this paper, we present a packet-loss resilient 3-D graphics transmission system that is scalable with respect to both channel bandwidth and channel error characteristics. The algorithm trades off sourcecoding effi...
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ISBN:
(纸本)0780374029
In this paper, we present a packet-loss resilient 3-D graphics transmission system that is scalable with respect to both channel bandwidth and channel error characteristics. The algorithm trades off sourcecoding efficiency for increased bit-stream error resilience to optimize the decoded mesh quality on the client side. It uses the Compressed Progressive Mesh (CPM) algorithm to generate a hierarchical bit-stream representing different levels of details (LODs). We assign optimal for-ward error correction (FEC) code rates to protect different parts of the bit-stream differently. These optimal FEC code rates are determined theoretically via a distortion function that accounts for: the channel packet loss rate, the nature of the encoded 3-D mesh and the error protection bit-budget. We present experimental results, which show that with our unequal error protection (UEP) optimal approach, the decoded mesh quality degrades more gracefully (compared to either no error protection (NEP) or equal error protection (EEP) methods) as the packet loss rate increases.
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