Article de revue avec comité de lecture
IEEE transactions on communications, june 2012, vol. 60, n° 6, pp. 1669-1680
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 sourcesymbol
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.
1 : SC - Dépt. Signal et Communications (Institut Mines-Télécom-Télécom Bretagne-UEB)
2 : ENIT - Ecole nationale d'ingénieurs de Tunis (.)
3 : Lab-STICC - Laboratoire en sciences et technologies de l'information, de la communication et de la connaissance (UMR CNRS 6285 - Télécom Bretagne - Université de Bretagne Occidentale - Université de Bretagne Sud)
Communication system performance, Source coding, Variable-length codes, Error correction coding, Iterative methods