EXIT-Chart Optimized Short Block Codes for Iterative Joint Source and Channel Decoding in H.264 Video Telephony

In this paper, we propose a family of short block codes (SBCs) designed for guaranteed convergence in soft-bit-assisted iterative joint source and channel decoding, which facilitate improved iterative soft-bit source decoding (SBSD) and channel decoding. Data-partitioned (DP) H.264 source-coded video is used to evaluate the performance of our system using SBC-assisted SBSD, in conjunction with recursive systematic convolution (RSC) codes for transmission over correlated narrow-band Rayleigh fading channels. The effect of different SBC schemes having diverse minimum Hamming distances d _H,min and code rates on the attainable system performance is demonstrated, when using iterative SBSD and channel decoding, while keeping the overall bit rate budget constant by appropriately partitioning the total available bit rate budget between the source and channel codecs to improve the overall bit error rate (BER) performance and to enhance the objective video quality expressed in terms of peak signal-to-noise ratio (PSNR). EXtrinsic Information Transfer (EXIT) charts were used to analyze the attainable system performance. Explicitly, our experimental results show that the proposed error protection scheme using rate-1/3 SBCs having d _H,min = 6 outperforms the identical-rate SBCs having d _H,min = 3 by about 2.25 dB at the PSNR degradation point of 1 dB. Additionally, an Eb/N ₀ gain of 9 dB was achieved, compared with the rate-5/6 SBC having d _H,min = 2 and an identical overall code rate. Furthermore, an Eb/N ₀ gain of 25 dB is attained at the PSNR degradation point of 1 dB while using iterative soft-bit source and channel decoding with the aid of rate-1/3 SBCs relative to the identical-rate benchmarker.