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iterative source-channel decoding: Improved system design using EXIT charts

EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING 2005年第6期2005卷 928-941页

作者： Adrat, M Vary, P Rhein Westfal TH Aachen Inst Commun Syst & Data Proc D-52056 Aachen Germany

The error robustness of digital communication systems using source and channel coding can be improved by iterative source-channel decoding (ISCD). The turbo-like evaluation of natural residual source redundancy and of artificial channel coding redundancy makes step-wise quality gains possible by several iterations. The maximum number of profitable iterations is predictable by an EXIT chart analysis. In this contribution, we exploit the EXIT chart representation to improve the error correcting/concealing capabilities of ISCD schemes. We propose new design guidelines to select appropriate bit mappings and to design the channel coding component. A parametric source coding scheme with some residual redundancy is assumed. Applying both innovations, the new EXIT-optimized index assignment as well as the appropriately designed recursive nonsystematic convolutional (RNSC) code allow to outperform known approaches to ISCD by far in the most relevant channel conditions.

关键词： iterative source-channel decoding turbo principle soft-input/soft-output decoding softbit source decoding extrinsic information EXIT charts

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iterative source-channel decoding with Markov random field source models

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2006年第10期54卷 3688-3701页

作者： Kliewer, Jorg Goertz, Norbert Mertins, Alfred Univ Notre Dame Dept Elect Engn Notre Dame IN 46556 USA Univ Edinburgh Inst Digital Commun Joint Res Inst Signal & Image Proc Edinburgh EH9 3JL Midlothian Scotland Carl von Ossietzky Univ Oldenburg Dept Phys D-26111 Oldenburg Germany

We propose a joint source-channel decoding approach for multidimensional correlated source signals. A Markov random field (MRF) source model is used which exemplarily considers the residual spatial correlations in an image signal after source encoding. Furthermore, the MRF parameters are selected via an analysis based on extrinsic information transfer charts. Due to the link between MPFs and the Gibbs distribution, the resulting soft-input soft-output (SISO) source decoder can be implemented with very low complexity. We prove that the inclusion of a high-rate block code after the quantization stage allows the MRF-based decoder to yield the maximum average extrinsic information. When channel codes are used for additional error protection the MRF-based SISO source decoder can be used as the outer constituent decoder in an iterative source-channel decoding scheme. Considering an example of a simple image transmission system we show that iterative decoding can be successfully employed for recovering the image data, especially when the channel is heavily corrupted.

关键词： EXIT charts iterative source-channel decoding joint source-channel coding Markov random fields

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iterative source-channel decoding Design using Distortion based Index Assignment and Joint Redundant Information

Iterative Source-Channel Decoding Design using Distortion ba...

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IEEE Workshop on Signal Processing Systems (SiPS)

作者： Wu, Chun-Feng Chung, Wei-Ho Acad Sinica Res Ctr Informat Technol Innovat Taipei Taiwan

ISBN: (纸本)9781467362382

This work presents a convolutional coded iterative source-channel decoding (ISCD) to improve the fidelity of joint source-channel coded systems through designing index assignment (IA). A proposed end-to-end distortion based IA generates the joint redundant bits to provide more useful information for source and channel decoders. Specifically, such joint redundant bit not only enhances the error-correcting capacity of source codes but also provides the self-concatenated convolutional codes instead of convolutional codes for ISCD. In contrast to the conventional ISCD, our proposed ISCD employs the self-iterative channel decoding algorithm, and the extrinsic information exchange can be further enhanced through joint redundant bits. With considering joint redundant bits, we propose a modified source decoder with the goal to extract the extrinsic information for the self-iterative channel decoder. Simulation results show the proposed ISCD with our designed IA can further improve the Parameter Signal-to-Noise ratio performance.

关键词： source decoding index assignment iterative source-channel decoding

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Two-Dimensional iterative source-channel decoding for Distributed Video Coding

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IEEE COMMUNICATIONS LETTERS 2014年第1期18卷 90-93页

作者： Huo, Yongkai Wang, Tao Maunder, Rob Hanzo, Lajos Univ Southampton Southampton SO9 5NH Hants England

Motivated by the Joint source-channel decoding (JSCD) principle of exploiting the source redundancy, in this treatise we study the application of iterative source-channel decoding (ISCD) conceived for distributed video coding (DVC), where the video signal is modelled by our iterative Horizontal-Vertical Scanline Model (IHVSM) relying on a first-order Markov process. The IHVSM technique is combined with the classic forward error correction (FEC) codecs employed in the state-of-the-art DVC systems for the sake of reducing the bitrate. Our simulation results show that up to 21.5% bitrate reductions are achieved by employing the proposed ISCD technique in a DVC scheme. Alternatively, a peak signal-to-noise ratio (PSNR) gain of 2.2 dB is achieved at a bitrate of 4.5 Mbps when considering the Foreman sequence.

关键词： iterative source-channel decoding distributed video coding

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Progressive Coding and iterative source-channel decoding in Wireless Data Gathering Networks

Progressive Coding and Iterative Source-Channel Decoding in ...

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54th Annual IEEE Global Telecommunications Conference (GLOBECOM)

作者： Li, Congduan Flikkema, Paul G. Howard, Sheryl L. No Arizona Univ Dept EECS Flagstaff AZ 86001 USA

ISBN: (纸本)9781424492688

Wireless data gathering networks are often tasked to gather correlated data under severe energy constraints. The use of simple channel codes with source-channel decoding can potentially provide good performance with low energy consumption. Here we consider progressive coding in multi-hop networks, where an intermediate node decodes its received noisy codewords. The estimated information is concatenated with the node's own information word and encoded;the resulting progressively-encoded codeword is then transmitted to the next node. In non-progressive coding, the node simply forwards the received noisy codewords along with its own encoded data. Here we compare the performance of two codes with low decoding complexity, Repeat-Accumulate (RA) and Low-Density Parity-Check (LDPC) codes, in combination with two progressive coding schemes. Progressive channel coding uses only channel decoding at the intermediate node, while progressive source-channel coding uses source-channel decoding, exploiting the probabilistic dependency of the information words (caused by the correlation structure of the data) jointly with the deterministic dependency induced by channel coding. Two decoding schemes are considered at the data center: channel decoding only and iterative source-channel decoding. In simulation experiments, we consider a line network topology with systematic RA and LDPC coding. Results show that progressive coding performs better than non-progressive coding, and RA codes perform better with lower computational complexity than LDPC codes, both for channel-decoding-only and iterative source-channel decoding.

关键词： Complexity theory decoding Encoding iterative decoding LDPC codes Peer to peer computing Wireless sensor networks combined source-channel coding computational complexity computational complexity deterministic dependency energy constraints intermediate node iterative decoding iterative source-channel decoding line network topology low energy consumption low-density parity-check codes multihop networks parity check codes progressive coding progressively-encoded codeword received noisy codewords repeat-accumulate codes simple channel codes telecommunication network topology wireless data gathering networks

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Unequal error protection irregular over-complete mapping for wavelet coded wireless video telephony using iterative source and channel decoding

Unequal error protection irregular over-complete mapping for...

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IEEE Wireless Communications and Networking Conference

作者： Pham, A. Q. Yang, L. L. Hanzo, L. Univ Southampton Sch ECS Southampton SO17 1BJ Hants England

ISBN: (纸本)9781424419968

Since the different bits of the compressed video sequence produced by the BBC's wavelet-based video codec exhibit different error sensitivity, efficient Unequal Error Protection (UEP) schemes have to be used to ensure that the perceptually more important bits benefit from more powerful protection. Furthermore, in the context of turbo detection the over-complete mapping aided soft videobit based source decoder should also match the characteristics of the channel codes for the sake of attaining a good iterative decoding performance. In this paper, we address this design dilemma by proposing a novel Irregular Over-complete Mapping (IrOM) scheme constituted by an appropriately weighted different-rate over-complete mapping. Our turbo detection scheme has attractive iterative decoding convergence properties, while maintaining unequal error protection capabilities matched to the requirements of the wavelet encoded video sequence. An EXIT chart based design guideline is presented and used in the context of protecting the different-sensitivity video bits of the BBC wavelet-based video codec. As a benefit, the unequal error protection scheme using rate 2/3 irregular over-complete mapping exhibits a transmit power advantage of about 0.7dB at an error probability of 0.016% over the equal-protection benchmarker scheme employing rate 2/3 over-complete mapping, when communicating over the uncorrelated Rayleigh-fading channel. This leads to an approximately 1dB signal-to-noise ratio gain, when considering the video PSNR performance of our UEP iterative source-channel decoding scheme using an over-complete mapping having the same rate and I = 6 iterations.

关键词： generalized low-density parity-check codes iterative source-channel decoding extrinsic information transfer charts over-complete mapping irregular

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Joint optimization of iterative source and channel decoding using over-complete source-mapping

Joint optimization of Iterative Source and Channel Decoding ...

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66th IEEE Vehicular Technology Conference

作者： Pham, A. Q. Yang, L. L. Hanzo, L. Univ Southampton Sch ECS Southampton SO17 1BJ Hants England

ISBN: (纸本)9781424402632

The intentionally imposed or inherent unintentional residual redundancy found in source encoded bitstreams can be exploited for supporting joint SoftBit-source decoding and channel decoding, which has the potential of improving both error correcting capability as well as the subjective audio or video quality of communication systems. As a potent error concealment technique, the softbit-based source decoding, proposed by Adrat, Vary and Spittka exploits the residual redundancy or correlation inherent in the source codec parameters for mitigating the effects of transmission errors. However, when using efficient source encoders, limited source redundancy is left in the source-encoded bitstream. In this scenario the SoftBit-source Decoder (SBSD) may have a limited extrinsic information contribution which results in no system performance improvements beyond two decoding iterations. In our novel approach, we partition the total available bit budget between the source and channel coders in order to improve the attainable error correcting capability and hence to maximize the overall system's performance. More explicitly, the inherent redundancy in the encoded bitstream is intentionally increased with the aid of over-complete mapping, and EXtrinsic Information Transfer (EXIT) charts are used for designing a suitable mapping of the source-coded bits to the modulated symbols, leading to an approximately 2dB signal-to-noise gain.

关键词： generalized low-density parity-check codes iterative source-channel decoding extrinsic information transfer charts over-complete mapping

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Irregular 8PSK mapping for variable length codes with small blocks in a BICM-ID system

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EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING 2015年第1期2015卷 1页

作者： Dai, Jing Zhang, Can Gao, Shaoshuai Hou, Lei Univ Chinese Acad Sci Sch Elect Elect & Commun Engn Beijing 100049 Peoples R China

iterative decoding is an effective technique to approach the channel capacity for very large block sizes with enough iterations. However, due to the limitation of bandwidth and delay, small blocks of data are much more commonly applied in practical communications, and low iteration counts are usually preferred for both decoding complexity and delay consideration. In such cases, the design rules of near capacity decoding-which is generally asymptotic with respect to the block size-may cause inferior performance. To overcome this problem for 8-phase shift keying (8PSK) modulated variable length codes (VLCs), an irregular mapping scheme for the transmission system of bit-interleaved coded modulation with iterative decoding (BICM-ID) is studied in this paper. A submapping searching algorithm and an irregular mapping optimization algorithm are proposed aiming at maximizing the extrinsic mutual information after a target number of iterations. Simulation results show that for small data block size with a low iteration count, our scheme has advantages with respect to the existing near capacity systems optimized by the asymptotic tools.

关键词： Bit-interleaved coded modulation Irregular codes Variable length codes iterative source-channel decoding

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NEAR-LOSSLESS COMPRESSION AND PROTECTION BY TURBO source-channel (DE-)CODING USING IRREGULAR INDEX ASSIGNMENTS

NEAR-LOSSLESS COMPRESSION AND PROTECTION BY TURBO SOURCE-CHA...

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IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Schmalen, Laurent Vary, Peter Rhein Westfal TH Aachen Inst Commun Syst & Data Proc Aachen Germany

ISBN: (纸本)9781424423538

In this paper, we present a novel near-lossless compression scheme for scalar-quantized source codec parameters. The scheme is comparable to a Turbo source coding approach and can inherently incorporate protection against transmission errors. We show that using the concept of EXIT charts and irregular codes, a linear programming optimization problem can be formulated and the solution of this problem leads to an irregular index assignment offering the best possible compression given the considered system model and a fixed channel quality. The performance of the compression scheme is demonstrated by a simulation example.

关键词： iterative source-channel decoding Irregular Codes Near-Lossless source Coding Turbo source Coding

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Joint source and channel decoding of Variable Length Codes Based on Pruned VLC-Block Trellis

Joint Source and Channel Decoding of Variable Length Codes B...

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20th IEEE Symposium on Communications and Vehicular Technology in the Benelux (SCVT)

作者： Tu, Guofang Dai, Jing Univ Chinese Acad Sci Sch Elect Elect & Commun Engn Beijing 100049 Peoples R China

ISBN: (纸本)9781479932061

Joint source and channel decoding (JSCD) of variable length codes (VLCs) has been attracting considerable attention in recent years. It is a capacity-approaching technique to decode in an iterative way, or known as iterative source-channel decoding (ISCD) of VLCs. When the side information of both bit length and symbol length of the VLC sequence are available, VLC-block trellis can be constructed, which exploits the knowledge of both lengths. The ISCD based on VLC-block trellis generally performs better than that based on the more widely used Balakirsky trellis. However, the complexity of VLC-block trellis is much higher, and grows exponentially with the sequence size. In this paper we study a sub-optimal solution by pruning some states and branches of the trellis. Simulation results show that this method can adjustably reduce complexity with acceptable performance loss.

关键词： Joint source and channel decoding iterative source-channel decoding variable length code VLC-block trellis BCJR

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