Performance evaluation in multimedia CDMA wireless transmission

Investigates the behavior of block errors in multimedia direct-sequence (DS) CDMA transmission systems operating over slow fading channels. We show that block errors can be accurately modeled by a first-order Markov process. Although Markov models have been used before to analyze packet transmission over radio channels, they have not been applied to CDMA systems that incorporate convolutional codes (CC) with soft-decision decoding. A major contribution of this work is to include in the new Markov model the effects of the CC, soft-decision decoding, and the RAKE diversity fingers with maximal ratio combining. The validity and accuracy of the model are established based on information-theoretic arguments and confirmed by computer simulation. A method to estimate the Markov process parameters is also presented. Another major contribution of this paper is the analysis of the throughput of the go-back-N and selective-repeat automatic repeat request (ARQ) protocols over DS-CDMA systems using the proposed Markov model. Several cases involving different numbers of RAKE fingers and various values of round-trip delays are analyzed. Our approximation is found to be excellent in all cases. The study of multimedia transmission, especially video, over DS-CDMA channels is greatly simplified using the model introduced in this work