Unequal Error Protection Irregular Over-Complete Mapping for Wavelet Coded Wireless Video Telephony Using Iterative Source and Channel Decoding

Abstract—Since the different bits of the compressed video sequence produced by the BBC’s wavelet-based video codec exhibit different error sensitivity, efficient Unequal Error Protection (UEP) schemes have to be used to ensure that the perceptually more important bits benefit from more powerful protection. Furthermore, in the context of turbo detection the over-complete mapping aided soft videobit based source decoder should also match the characteristics of the channel codes for the sake of attaining a good iterative decoding performance. In this paper, we address this design dilemma by proposing a novel Irregular Over-complete Mapping (IrOM) scheme constituted by an appropriately weighted different-rate over-complete mapping. Our turbo detection scheme has attractive iterative decoding convergence properties, while maintaining unequal error protection capabilities matched to the requirements of the wavelet encoded video sequence. An EXIT chart based design guideline is presented and used in the context of protecting the different-sensitivity video bits of the BBC wavelet-based video codec. As a benefit, the unequal error protection scheme using rate 2/3 irregular over-complete mapping exhibits a transmit power advantage of about 0.7dB at an error probability of 0.016% over the equal-protection benchmarker scheme employing rate 2/3 over-complete mapping, when communicating over the uncorrelated Rayleigh-fading channel. This leads to an approximately 1dB signal-to-noise ratio gain, when considering the video PSNR performance of our UEP iterative source-channel decoding scheme using an overcomplete mapping having the same rate and I = 6 iterations. Index Terms—generalized low-density parity-check codes, iterative source-channel decoding, extrinsic information transfer charts, over-complete mapping, irregula