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

This paper deals with the problem of efficient transmission of video signal s over generalized fading channels in direct sequence-spread spectrum (DS-S S) code division multiple access (CDMA) systems. We first propose a modifie d version of the H.263 video codec incorporating a selective forward error correction (FEC) coding scheme combined with a forced intra-frame update me chanism. The modified codec results in the improvement of the average video and frame-to-frame performance, We further consider a coherent DS-CDMA sys tem for the forward link (base-to-mobile) in both single-cell and multiple- cell environment. We provide performance evaluation results by both analysi s, employing the Gaussian approximation, and computer simulations, using Mo nte Carlo error counting techniques. By integrating the proposed,ideo codec with a coherent DS-CDMA system based upon the IS-95 standard, we investiga te the performance of the video transmission over frequency-selective, corr elated Nakagami fading forward-link channels employing a RAKE receiver. To simulate the fading channel, we have implemented in software a correlated N akagami fading simulator based upon the principle of superposition of compl ex partial waves, an approach which replicates the wave propagation process in actual physical situation. A variety of performance evaluation results, both in single-cell and multiple-cell environment, are presented for a dif ferent number of resolving paths, cell user capacity, signal propagation ch aracteristics, as well as for the presence of channel estimation errors. In all cases, heuristic explanations and interpretations of the trend of the obtained results are also given.