It is well known that Shannon's separation result does not hold under finite computation or finite delay constraints, thus joint source-channel coding is of great interest for practical reasons. For progressive source-channel coding systems, efficient codes have been proposed for feed forward channels [1] and the important problem of rate allocation between the source and channel codes has been solved [2]. For memoryless channels with feedback, the rate allocation problem was studied in [3]. In this paper, we consider the case of the fading channels with feedback. Feedback routes are provided in many existing standard wireless channels, making rate allocation with feedback a problem of considerable practical importance. We address the question of rate allocation between the source and channel codes in the forward channel, in the presence of feedback information and under a distortion cost function. We show that the presence of feedback shifts the optimal rate allocation point, resulting higher rates for error-correcting codes and smaller overall distortion. Simulations on both memoryless and fading channels show that the presence of feedback allows up to 1 dB improvement in PSNR compared to the similarly optimized feed forward scheme.
Citation:
Jin Lu, Aria Nosratinia, Behnaam Aazhang, "Progressive Joint Source-Channel Coding in Feedback Channels," dcc, pp.140, Data Compression Conference (DCC '99), 1999