Channel decoding of block codes with a priori information

Author

El Baz, A. ; Aitsab, O. ; Pyndiah, R. ; Solaiman, B.

Author_Institution

Dept. Signal & Commun., ENST de Bretagne, Brest, France

Volume

6

fYear

1998

fDate

1998

Firstpage

3536

Abstract

We propose a complete transmission system for still images. This system comprises a VQ source encoder with a compression rate of 9 and the data is encoded using a BCH block code and mapped on a 16-QAM constellation. Two BCH codes are considered: BCH(29,24,3) and BCH(54,48,3). The parameters of the code book and channel encoder have been optimized for 16-QAM. We use a new joint source-channel decoding algorithm for a block code. As compared to classical channel decoding algorithms (hard decoding and soft decoding), we obtain an improvement of 1 dB over a Gaussian channel and 3 dB over a Rayleigh channel, in terms of coding gain for a BER of 10^-5. The PSNR of the received image exhibits an improvement of 3 dB as compared to a conventional system without joint source-channel decoding at low SNRs. The decoded image presents a good subjective quality even if the residual BER is high

Keywords

BCH codes; Gaussian channels; Rayleigh channels; block codes; combined source-channel coding; decoding; error statistics; image coding; quadrature amplitude modulation; vector quantisation; visual communication; 16-QAM constellation; BCH block code; Gaussian channel; PSNR; Rayleigh channel; VQ source encoder; a priori information; channel decoding; channel encoder; classical channel decoding algorithms; code book parameters; coding gain; compression rate; decoded image; hard decoding; joint source-channel decoding algorithm; low SNR; residual BER; soft decoding; still image transmission system; subjective quality; Bit error rate; Bit rate; Block codes; Books; Channel coding; Decoding; Error correction codes; Image coding; Source coding; Vector quantization;

fLanguage

English

Publisher

ieee

Conference_Titel

Global Telecommunications Conference, 1998. GLOBECOM 1998. The Bridge to Global Integration. IEEE

Conference_Location

Sydney,NSW

Print_ISBN

0-7803-4984-9

Type

conf

DOI

10.1109/GLOCOM.1998.775864

Filename

775864