Optimal bit allocation for source/channel coding in joint trellis coded quantization/modulation

Shannon (1948) showed that the problems of source and channel coding could be considered separately, without loss of performance, if complexity is not an issue. Previous investigations have shown a performance gain for more practical problems where channel and source coding have been jointly designed. This paper investigates the joint source/channel coding problem when using trellis coded quantization (TCQ). TCQ has shown to offer improved source coding performance (when compared to Lloyd-Max quantization) while additionally offering some error immunity. When using TCQ in practical transmission systems, the question arises as to the number of bits that should be allocated to source and channel coding for overall best performance. Results here show that for binary symmetric channels with medium SNRs, better overall mean square error (MSE) performance results from taking bits from the source coder and allocating them to the channel coder. However, for high and low SNRs better MSE results from allocating all bits to source coder.