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On the performance of spread-spectrum multiple-access communications in multipath fading channels

In this paper, we consider the error rate performance of asynchronous direct-sequence CDMA in a mobile radio communications environment that is characterized by Rayleigh multipath fading channels. Because of the system complexity, the performance of CDMA systems in such an environment is difficult to assess analytically without making restrictive assumptions. Monte Carlo simulations can offer an alternative performance evaluation tool. Unfortunately, in practice such an alternative is often limited by an excessive computational burden. Importance sampling is a variance reduction technique which can significantly reduce the computational cost required by Monte Carlo simulations. This paper will describe the basic principles behind this powerful technique. In particular, it will illustrate its use as a computationally efficient and accurate tool for computer-aided design and analysis of CDMA in wireless communications.