Convergence Behaviour of Iteratively Decoded Short Block-Codes in H.264 Joint Source and Channel Decoding

We propose a novel class of short block codes (SBCs) designed for guaranteed convergence to an infinitesimally low bit error ratio (BER), which relies on the joint optimisation of soft-bit assisted iterative source and channel decoding. An iterative detection aided combination of SBC assisted soft-bit source decoding (SBSD) and a rate-1 precoder was used to evaluate the attainable performance of the proposed scheme for transmission of data-partitioned (DP) H.264 source coded video over correlated narrowband Rayleigh fading channels. Additionally, we demonstrated the effects of different SBCs having diverse minimum Hamming distances [d_H,min] but identical coding rates on both the overall BER performance as well as on the objective video quality expressed in terms of the Peak Signal-to-Noise Ratio (PSNR). The convergence behaviour of the iterative decoding scheme using SBCs as a function of d_H,min is analysed by utilising extrinsic information transfer (EXIT) charts. Explicitly, our experimental results show that the proposed error protection scheme using SBCs associated with d_H,min = 6 outperforms the identical-code-rate SBCs having d_H,min = 3 by about 3 dB at the PSNR degradation point of 1 dB. Additionally, an E_b/N_o gain of 27 dB is attained using iterative soft-bit source and channel decoding with the aid of rate-1/3 SBCs relative to the identical-rate benchmarker.