MAP decoding of variable length codes over noisy channels

Lei Yao; Lei Cao; Chang Wen Chen

doi:10.1117/12.630926

Abstract

In this paper, we discuss the maximum a-posteriori probability (MAP) decoding of variable length codes(VLCs) and propose a novel decoding scheme for the Huffman VLC coded data in the presence of noise. First, we provide some simulation results of VLC MAP decoding and highlight some features that have not been discussed yet in existing work. We will show that the improvement of MAP decoding over the conventional VLC decoding comes mostly from the memory information in the source and give some observations regarding the advantage of soft VLC MAP decoding over hard VLC MAP decoding when AWGN channel is considered. Second, with the recognition that the difficulty in VLC MAP decoding is the lack of synchronization between the symbol sequence and the coded bit sequence, which makes the parsing from the latter to the former extremely complex, we propose a new MAP decoding algorithm by integrating the information of self-synchronization strings (SSSs), one important feature of the codeword structure, into the conventional MAP decoding. A consistent performance improvement and decoding complexity reduction over the conventional VLC MAP decoding can be achieved with the new scheme.

Citation Download Citation

Lei Yao, Lei Cao, Chang Wen Chen, "MAP decoding of variable length codes over noisy channels", Proc. SPIE 6015, Multimedia Systems and Applications VIII, 60150L (24 October 2005); doi: 10.1117/12.630926; https://doi.org/10.1117/12.630926

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