Low-delay communication for Rayleigh fading channels: an application of the multiple description quantizer

We show the multiple description scalar quantizer (MDSQ), when used over a slow fading Rayleigh channel, results in a smaller interleaving delay than traditional channel code-based approaches and substantially outperforms a system using a maximum ratio combiner. We consider a continuous alphabet source without memory over a slow Rayleigh fading channel. Specifically, it is initially assumed that the Rayleigh parameter remains constant over a specific time interval and the demodulator has available perfect estimates of the Rayleigh parameter. An analysis of the problem is presented and theoretical justification is provided for using the MDSQ. For a Gaussian source without memory, performance comparisons are presented against a traditional maximum ratio combiner (MRC)-based system as well as against channel code-based systems. It is shown that the performance of the MDSQ-based system dominates the MRC-based system at all channel signal-to-noise ratios and is superior to channel code-based systems when the interleaving delay is constrained. Simulation results for a mobile radio channel model at 15 m.p.h. indicate a reduction in the interleaving delay by at least a factor of three.