Iterative Joint Source-channel Decoding Research Articles

On the Performance of Wireless Video Communication Using Iterative Joint Source Channel Decoding and Transmitter Diversity Gain Technique

In this research work, we have presented an iterative joint source channel decoding- (IJSCD-) based wireless video communication system. The anticipated transmission system is using the sphere packing (SP) modulation assisted differential space-time spreading (DSTS) multiple input-multiple output (MIMO) scheme. SP modulation-aided DSTS transmission mechanism results in achieving high diversity gain by keeping the maximum possible Euclidean distance between the modulated symbols. Furthermore, the proposed DSTS scheme results in a low-complexity MIMO scheme, due to nonemployment of any channel estimation mechanism. Various combinations of source bit coding- (SBC-) aided IJSCD error protection scheme has been used, while considering their identical overall bit rate budget. Artificial redundancy is incorporated in the source-coded stream for the proposed SBC scheme. The motive of adding artificial redundancy is to increase the iterative decoding performance. The performance of diverse SBC schemes is investigated for identical overall code rate. SBC schemes are employed with different combinations of inner recursive systematic convolutional (RSC) codes and outer SBC codes. Furthermore, the convergence behaviour of the employed error protection schemes is investigated using extrinsic information transfer (EXIT) charts. The results of experiments show that our proposed R a t e − 2 / 3 SBC-assisted error protection scheme with high redundancy incorporation and convergence capability gives better performance. The proposed R a t e − 2 / 3 SBC gives about 1.5 dB E b / N 0 gain at the PSNR degradation point of 1 dB as compared to R a t e − 6 / 7 SBC-assisted error protection scheme, while sustaining the overall bit rate budget. Furthermore, it is also concluded that the proposed R a t e − 2 / 3 SBC-assisted scheme results in E b / N 0 gain of 24 dB at the PSNR degradation point of 1 dB with reference to R a t e − 1 SBC benchmarker scheme.

EXIT Chart Analysis of Turbo Compressed Sensing Using Message Passing Dequantization

We propose an iterative decoding method, which we call turbo-CS, for the reception of concatenated source-channel encoded sparse signals transmitted over an AWGN channel. The turbo-CS encoder applies 1-bit compressed sensing as a source encoder concatenated serially with a convolutional channel encoder. At the turbo-CS decoder, an iterative joint source-channel decoding method is proposed for signal reconstruction. We analyze, for the first time, the convergence of turbo-CS decoder by determining an EXIT chart of the constituent decoders. We modify the soft-outputs of the decoder to improve the signal reconstruction performance of turbo-CS decoder. For a fixed signal reconstruction performance RSNR of 10 dB, we achieve more than 5 dB of improvement in the channel SNR after 6 iterations of the turbo-CS. Alternatively, for a fixed SNR of -1 dB, we achieve a 10 dB improvement in RSNR.

Spatio-Temporal Iterative Source–Channel Decoding Aided Video Transmission

Low-complexity uncompressed video transmission meets the requirements of home networking and quality/delay-sensitive medical applications. Hence, it has attracted research attention in recent years. The redundancy inherent in the uncompressed video signals may be exploited by joint source–channel decoding to improve the attainable error resilience. Hence, in this treatise, we study the application of iterative joint source–channel decoding aided uncompressed video transmission, where correlation inherent in the video signals is modeled by a first-order Markov process. First, we propose a spatiotemporal joint source–channel decoding system using a recursive systematic convolutional codec, where both the horizontal and vertical intraframe correlations, as well as the interframe correlations, are exploited by the receiver, hence relying on 3-D information exchange. This scheme may be combined with arbitrary channel codecs. Then, we analyze the three-stage decoder's convergence behavior using 3-D extrinsic information transfer (EXIT) charts. Finally, we benchmark the attainable system performance against a couple of video communication systems, including our previously proposed 2-D scheme, where only intraframe correlations were exploited without invoking a channel codec. Our simulation results show that substantial $E_{b}/N_{0}$ improvements are attainable by the proposed technique.

Robust Transmission of Compressed HTML Files over Wireless Channel using an Iterative Joint Source-Channel Decoding Receiver

This paper proposes an algorithm for the robust reception of compressed HTML files transmitted over a noisy mobile radio channel. Both source encoders and transmission systems are assumed to be standard compliant. The source encoder follows the HTTP1.1 protocol specifications, i.e. the HTML files are encoded by the deflate algorithm, a combination of Lempel-Ziv and Huffman algorithms. The transmission scheme follows IEEE 802.11a (and 802.11n) standard as an example. The proposed receiver is based on an iterative joint source-channel decoding approach. The Soft-Input Soft-Output outer source decoder is based on a sequential M-algorithm, which has been modified to improve the decoding performance by exploiting the specific grammatical and syntax rules of (i) Huffman codes; (ii) Lempel-Ziv codes; and (iii) HTML language. Simulation results following the IEEE 802.11a (and 802.11n) standard over additive white Gaussian noise and Rayleigh fading channels show that the proposed receiver drastically reduces the number of errors occurring in the received HTML files compared to the classical receivers. An EXIT chart analysis illustrates some properties of this combination of source and channel decoders.

Low-Complexity Soft Decoding of Huffman Codes and Iterative Joint Source Channel Decoding

Most source coding standards (voice, audio, image and video) use Variable-Length Codes (VLCs) for compression. However, the VLC decoder is very sensitive to transmission errors in the compressed bit-stream. Previous contributions, using a trellis description of the VLC codewords to perform soft decoding, have been proposed. Significant improvements are achieved by this approach when compared with prefix decoding. Nevertheless, for realistic VLCs, the complexity of the trellis technique becomes intractable. In this paper, we propose a soft-input VLC decoding method using an a priori knowledge of the lengths of the source-symbol sequence and the compressed bit-stream with Maximum A Posteriori (MAP) sequence estimation. Performance in the case of transmission over an Additive White Gaussian Noise (AWGN) channel is evaluated. Simulation results show that the proposed decoding algorithm leads to significant performance gain in comparison with the prefix VLC decoding besides exhibiting very low complexity. A new VLC decoding method generating additional information regarding the reliability of the bits of the compressed bit-stream is also proposed. We consider the serial concatenation of a VLC with two types of channel code and perform iterative decoding. Results show that, when concatenated with a recursive systematic convolutional code (RSCC), iterative decoding provides remarkable error correction performance. In fact, a gain of about 2.3 dB is achieved, in the case of transmission over an AWGN channel, with respect to tandem decoding. Second, we consider a concatenation with a low-density parity-check (LDPC) code and it is shown that iterative joint source/channel decoding outperforms tandem decoding and an additional coding gain of 0.25 dB is achieved.

Near-Capacity H.264 Multimedia Communications Using Iterative Joint Source-Channel Decoding

In this tutorial, a unified treatment of the topic of near capacity multimedia communication systems is offered, where we focus our attention not only on source and channel coding but also on their iterative decoding and transmission schemes. There is a paucity of up-to-date surveys and review articles on the unified treatment of the topic of near capacity multimedia communication systems using iterative detection aided joint source-channel decoding employing sophisticated transmission techniques - even though there is a plethora of papers on both iterative detection and video telephony. Hence this paper aims to fill the related gap in the literature.

Iterative joint source–channel decoding of H.264 compressed video

This paper proposes an Iterative Joint Source–Channel Decoding (IJSCD) scheme for error resilient transmission of H.264 compressed video over noisy channels by using the available H.264 compression, e.g., Context-based Adaptive Binary Arithmetic Coding (CABAC), and channel coding, i.e., rate-1/2 Recursive Systematic Convolutional (RSC) code, in transmission. At the receiver, the turbo decoding concept is explored to develop a joint source–channel decoding structure using a soft-in soft-out channel decoder in conjunction with the source decoding functions, e.g., CABAC-based H.264 semantic verification, in an iterative manner. Illustrative designs of the proposed IJSCD scheme for an Additive White Gaussian Noise (AWGN) channel, including the derivations of key parameters for soft information are discussed. The performance of the proposed IJSCD scheme is shown for several video sequences. In the examples, for the same desired Peak Signal-to-Noise Ratio (PSNR), the proposed IJSCD scheme offers a savings of up to 2.1 dB in required channel Signal-to-Noise Ratio (SNR) as compared to a system using the same RSC code alone. The complexity of the proposed scheme is also evaluated. As the number of iterations is controllable, a tradeoff can be made between performance improvement and the overall complexity.

Iterative joint source-channel decoding of VLC exploiting source semantics over realistic radio-mobile channels

Joint source-channel decoding of variable length codes (VLC) for image and video transmission over wireless links is a subject of increasing interest. This paper proposes an optimum decoder of VLC sequences which exploits inherent redundancy in source data, namely the VLC syntax and source constraints. The proposed decoder is able to deliver both Maximum Likelihood optimum hard-output and soft-output solutions. The complexity of the algorithm is analyzed and a reduced complexity version of this algorithm with a slightly sub-optimal performance is proposed. An iterative joint source-channel decoding system is designed for demonstrating the performance of the proposed soft-input soft-output (SISO) decoder. Realistic contexts have been used for simulations: typical video sequences and typical radiomobile channels.

LDPC-Based Iterative Joint Source-Channel Decoding for JPEG2000

A framework is proposed for iterative joint source-channel decoding of JPEG2000 codestreams. At the encoder, JPEG2000 is used to perform source coding with certain error-resilience (ER) modes, and LDPC codes are used to perform channel coding. During decoding, the source decoder uses the ER modes to identify corrupt sections of the codestream and provides this information to the channel decoder. Decoding is carried out jointly in an iterative fashion. Experimental results indicate that the proposed method requires fewer iterations and improves overall system performance.

A turbo-coded multiple-description system for multiple antennas

We propose a joint source-channel coding scheme for wireless communication systems with multiple transmit and receive antennas. The source coder is realized by a multiple description encoder that generates multiple bit streams. Each description is then separately turbo coded and transmitted using multiple antennas. For the receiver, we describe a suitable iterative joint source-channel decoding technique that exploits the correlations between the descriptions. We present several examples that illustrate the performance of the proposed system, and compare it with other approaches.

On the iterative approximation of optimal joint source-channel decoding

Joint source-channel decoding is formulated as an estimation problem. The optimal solution is stated and it is shown that it is not feasible in many practical systems due to its complexity. Therefore, a novel iterative procedure for the approximation of the optimal solution is introduced, which is based on the principle of iterative decoding of turbo codes. New analytical expressions for different types of information in the optimal algorithm are used to derive the iterative approximation. A direct comparison of the performance of the optimal algorithm and its iterative approximation is given for a simple transmission system with short channel codewords. Furthermore, the performance of iterative joint source-channel decoding is investigated for a more realistic system.