CAPACITY ENHANCEMENT OF CDMA SYSTEM USING ANTENNA ARRAY

Abstract

This thesis is concerned with the study of capacity enhancement for a multirate code-division multiple access (CDMA) system with uniform linear array (ULA) at the base station (BS) [1 - 3]. An overall system outage probability is proposed as a capacity performance measure for multirate CDMA system with different service requirements among users. In this thesis, the performance analysis of a CDMA system with voice/data users is presented using two multirate schemes, the multi-processing-gain scheme and the multi-channel scheme. It is also proved that the system capacities for the two schemes are equal given certain conditions. Furthermore, the study includes investigations of uplink and downlink capacities with shadowing and multipath effects. Moreover, the simulation results show that using antenna array together with RAKE receiver at the base station can greatly increase the system capacity and mitigate multipath effect. It is shown that the system parameters such as data bit rate, activity factor of users, array size, and voice-to-data users ratio may affect the system performance significantly. Finally, the derived trade-off in these parameters will also help assess the operational cost of such a voice/data CDMA system.