Network Performance of Transmit Diversity in WCDMA-FDD

The capacity improvement in the network by employing Space-Time Transmit Diversity (STTD) at a WCDMA base station is analysed in this project. STTD is an open loop antenna diversity scheme where channel information at the transmit antennas is not required. The STTD feature offers diversity gain in the system by introducing additional diversity in radio environments having less or no diversity, which can be exploited by the mobile. According to the 3GPP specifications STTD implementation is optional for the network and mandatory for the UE. The performance of the STTD feature is analysed in different channel profiles for different UE speeds. Standard Radio Resource Management (RRM) algorithms compliant with WCDMA-FDD standard are used in the analysis. The performance evaluation is based on equivalent carried cell capacity. The carried cell capacity is estimated at given outage probability, which in the analysis is defined as the call-blocking rate. Call blocking occurs when the air-interface is limited. This is typically the case when the total transmit power target set for the downlink is reached. Given this capacity definition, all users that are granted access to the network operate at the desired Quality-of-Service (QoS) criteria based on a target Block Error Rate (BLER) requirement. It is expected that the system performance in terms of cell capacity will be improved with the STTD feature. The impact of capacity enhancement on radio resources like channelisation codes, transmit power will be evaluated. (Mangesh Ingale, Preben E. Mogensen; Klaus I. Pedersen, Nokia)