Chapter 2 - Why Joint Source and Channel Decoding?

Abstract

This chapter introduces theoretical justifications for joint source-channel coding (JSCC) and identifies certain expectations that one may have regarding JSCC and joint source-channel decoding (JSCD). It provides the basic information theoretic tools that are needed to understand the Shannon bounds in their various incarnations. One can evaluate, for simple sources, the minimum rate that is required to communicate the given source over a particular channel with a specified maximum end-to-end distortion. It demonstrates the separation theorem to be strongly dependent on the assumption of point-to-point communication of stationary sources without constraints on encoder/decoder complexity. Furthermore, it argues that practical applications (with complexity constraints, one-to-many architectures, and nonstationary sources and channels) can be better served by joint source/channel decoders. It then explains that JSCD, compared to separate channel decoding and source decoding, is better able to exploit imperfections (i.e., redundancy) in the received bitstream, especially when side information introduced by network protocols are considered.