Exploring the UMTS WCDMA-receiver design space using a semianalytical approach

A fast simulation technique for the analysis of the system performance of digital receivers is presented and applied to the UMTS terrestrial radio access (UTRA). This semianalytical method comprises the computation of receiver output statistics, conditioned on a static channel model, a given spreading sequence and a given transmitted symbol sequence. Averaging over the known channel tap probability density function and over all symbol sequences yields the system performance, conditioned on the selected spreading sequence. This method permits the qualitative classification and comparison of different detection algorithms for WCDMA in the performance-complexity design space. In the UTRA environment, the performance is shown to vary significantly with the choice of the OVSF spreading sequence. Simulation results for a RAKE receiver in indoor and outdoor scenarios are compared to lower and upper bounds of the probability of error of a maximum likelihood sequence estimation (MLSE) algorithm. It is shown that a RAKE receiver provides sufficient detection performance in medium-rate outdoor scenarios, whereas in high-rate indoor scenarios, especially in the uplink, alternative receiver structures must be considered.