Delay Constrained Multimedia Communications:Comparing Source-Channel Approaches for Quasi-Static Fading Channels

Real-time multimedia communication over a wireless link presents many challenges that require non-traditional methods to ensure good performance. A strict delay constraint prevents averaging over variations in the channel's fading coefficient, resulting in a channel with zero capacity in the Shannon sense. Without knowledge of the channel realization at the transmitter, separate source and channel coding is no longer optimal, and we must consider joint source-channel coding techniques. In this thesis we examine the performance of several schemes that attempt to mitigate the effects of non-ergodic fading on the end-to-end mean-square distortion. We derive an upper bound on the rate at which the expected distortion decays for high SNR, and the performance of each scheme is analytically characterized using this metric, the distortion exponent. Limitations of this distortion metric are also discussed and illustrated. We analyze the performance of uncoded and rate-optimized digital transmission over both a single channel and parallel channels. We consider successive refinement source coding utilizing superposition channel coding and show that in the high SNR limit it offers significantly improved performance relative to standard digital techniques. We present a hybrid digital-analog scheme as a simple form of multiple descriptions and show that it outperforms the other techniques considered for parallel channels.