Performance evaluation of transmit diversity techniques in the CDMA 2000 standard

Abstract

This thesis evaluates the performance of two forward-link transmit diversity techniques in the CDMA2000 standard: Space-Time Spreading (STS) and Phase-Sweep Transmit Diversity (PSTD). For each technique, the evaluation consists of conducting 9.6 kbps Markov calls in the field and measuring the mean forward-link fundamental-channel (F-FCH) transmit power required to achieve a 1% frame error-rate (FER) at the mobile receiver. The required transmit power is used to compute an estimate of cell capacity as measured by the number of supported users, assuming a fixed total transmit power at the base station. It is observed that enabling STS increases capacity by up to 80% if all mobiles support STS, but capacity is reduced by up to 20% when fewer than 35% of the mobiles support the technique. The capacity loss results from interference of the diversity-antenna signal on mobiles that do not support STS; such interference causes an F-FCH transmit power increase of up to 1.5 dB in multipath Rayleigh-faded channels, as observed in lab experiments. PSTD, which does not require mobile-specific support, was found to improve cell capacity by 12% according to the field experiments.