Efficient video transmission over correlated Nakagami fadingchannels for IS-95 CDMA systems

摘要

This paper deals with the problem of efficient transmission ofnvideo signals over generalized fading channels in direct sequence-spreadnspectrum (DS-SS) code division multiple access (CDMA) systems. We firstnpropose a modified version of the H.263 video codec incorporating anselective forward error correction (FEC) coding scheme combined with anforced intra-frame update mechanism. The modified codec results in thenimprovement of the average video and frame-to-frame performance. Wenfurther consider a coherent DS-CDMA system for the forward linkn(base-to-mobile) in both single-cell and multiple-cell environment. Wenprovide performance evaluation results by both analysis, employing thenGaussian approximation, and computer simulations, using Monte Carlonerror counting techniques. By integrating the proposed video codec withna coherent DS-CDMA system based upon the IS-95 standard, we investigatenthe performance of the video transmission over frequency-selective,ncorrelated Nakagami fading forward-link channels employing a RAKEnreceiver. To simulate the fading channel, we have implemented innsoftware a correlated Nakagami fading simulator based upon the principlenof superposition of complex partial waves, an approach which replicatesnthe wave propagation process in actual physical situations. A variety ofnperformance evaluation results, both in single-cell and multiple-cellnenvironment, are presented for a different number of resolving paths,ncell user capacity, signal propagation characteristics, as well as fornthe presence of channel estimation errors. Heuristic explanations andninterpretations of the trend of the obtained results are alsongiven