Performance of an adaptive space-time processing receiver for the user terminal of 3G WCDMA systems under COST 259 channel models

This paper presents an adaptive multi-target space-time architecture for downlink receivers in the user terminal of WCDMA systems under soft handoff. The receiver consists of M antennas and K array processors, each one followed by a chip-rate equalizer and a despreader. The resulting signals from these K branches are combined in an adaptive ratio combiner which is updated by the common channel information in UTRA FDD systems. When a large number of antennas is used each array processor is able to collect a given target ray and filter out all the others. On the other hand, when only a small number of antennas is used, due to cost or physical limitation, the chip-rate equalizers try to eliminate the residual interchip interference that strongly affects receiver performance. In both cases an efficient coherent receiver is obtained that exploits the space and time diversity in the incoming signal at the user terminal. All the signal structure of the FDD WCDMA downlink signal is exploited for improved performance. Simulation results using COST-259 channel models for vehicle speed of 50 km/h are compared with results obtained for a difficult hypothetical fixed channel condition.