Joint Source-Channel Coding with Inner Irregular Codes

We address the optimization of joint source-channel coding schemes for iterative source-channel decoding of first-order Markov sources. Compared to the traditional design, we propose two novelties: (1) source encoders, providing code words with a minimum Hamming distance distance d(min) >= 2, realized by linear block codes, and (2) irregular channel encoders which are optimized for both the source characteristics and the conditions on the channel. Inner code rates Rc > 1 may be chosen in order to compensate for the additional source redundancy if required. Design examples for the AWGN channel and an overall code rate R=0.66 show that the proposed system is able to establish reliable communication within 0.3 dB of the capacity limit for an interleaver length of approximatively 200000 bits.