Optimal Unequal Channel Protection of Multiple-Description Product Codes for Multimedia Communications Over Fast Fading Channels

In recent literature a powerful multiple description product coding scheme for protection of progressively encoded source streams has been devised that disperses information evenly between all description packets. Also, techniques were proposed to protect these packets equally by an optimal channel coder (found by exhaustive search). The contribution of this paper is to show that equal protection of all descriptions is suboptimal when the channel varies with time despite the fact that all descriptions have equal importance. We propose a theoretical framework for computing the globally optimal channel protection assignment for a given set of available channel coders under some idealized assumptions. For more practical scenarios we propose an optimized uneven packet protection scheme that outperforms equal protection schemes in terms of the expected distortion of received sources. Simulations of an image transmission system that resembles a 3G high bitrate link is provided where our unequal protection scheme improves the average PSNR of the received images by more than 1.3dB.