Joint source-channel coding in the presence of feedback

The effect of the presence of a feedback channel on the transmission of information was first considered by Shannon who showed that the capacity of a memory-less channel is not increased by feedback. Later it was shown that the information on a feedback channel can be used to improve the performance of channel coding. Here we show that by employing the feedback information in quantizer design for a noisy channel, one can achieve lower overall distortion compared to the case where feedback is not available or the quantizer is not matched to the channel. We consider an adaptive and a non-adaptive quantization scheme which show that especially for channels with high error rate, feedback information can lead to lower distortion compared to the case where no feedback information is available