Joint design of progressive fixed-rate source-channel codes

Summary form only given. The combination of jointly optimized rate compatible punctured convolutional (RCPC) codes and channel-matched tree-structured vector quantizers (CM-TSVQ) is shown to provide improved performance, in some cases, compared to the use of CM-TSVQ. The embedded nature of the RCPC codes and CM-TSVQ is inherited by the jointly optimized combination so that the resulting coder is itself progressive. The joint design algorithm allows unequal error protection to be applied to each bit of the CM-TSVQ output. When refinement bits are sent they may be used either to: (1) provide new source coding bits; (2) provide protection to new source coding bias; or (3) provide further protection to previous source coding bits. Soft decoding is used for the RCPC codes and, to allow equitable comparisons to be made, q-bit soft-decision BPSK modulation is used for the baseline CM-TSVQ (to which we make comparisons). The codebook size of the q-bit soft-decision based CM-TSVQ is 2/sup qrk/ where r is the rate in bits per sample and k is the vector dimension. An illustration of the results obtained for a Gauss-Markov source with correlation coefficient /spl rho/=0.9 and a channel SNR=0 dB is shown below. In this case, k=4 and end-to-end distortion is given in dB. In the cases marked "x", the system complexity precluded calculation of reliable results. Each row of the table shows the performance of a single embedded quantizer, with incremental rates of 0.5 bits per sample provided at each refinement. Our results show that the joint combination of soft-decoded RCPC codes and CM-TCVQ provides little rate-distortion advantage over soft CM-TSVQ at the first step of refinement. The same conclusion may be made about the joint combination of soft-decoded RCPC codes and COVQ versus soft COVQ.