Performance of speech services in WCDMA using fixed-beams and transmit diversity systems

The system capacity of speech users in WCDMA system is investigated using a number of different downlink transmit modes. A single antenna sectorized system, a two fixed-beam antenna array, a closed-loop (mode I) and an open-loop space time transmit diversity methods are compared in a dynamic radio network simulator. Frequency selective and flat fading channels are considered. The results show that the diversity gain in flat fading channels is substantial. In frequency selective fading, the benefits of fixed-beam systems are encouraging, whereas the performance of transmit diversity methods (especially the open-loop scheme) are rather unsatisfactory.