Acquisition performance in transmission diversity CDMA systems

Abstract

Two code acquisition schemes are studied for use in conjunction with transmit diversity direct sequence code division multiple access (DS-CDMA). One is a training based single user maximum likelihood (SUML) estimator, which can achieve code acquisition very fast at low computation complexity. The other is a blind estimator based on the multiple signal classification (MUSIC) algorithm. Two previously proposed transmit diversity schemes known as orthogonal transmit diversity simulcast (OTD-S) and space time selective transmit diversity (STSTD) are considered. While the advantages of transmit diversity from the detection standpoint are well known; less is known about how code acquisition performance is affected by the use of transmit diversity. Through the analysis, it is proven that the SUML estimator should give the same performance in both the OTD-S and STSTD schemes in a single user environment. In a multiple user environment, simulation results show that the STSTD system offers slightly better code acquisition performance. It is also seen that the SUML estimators provide significantly better code acquisition performance than the MUSIC estimators in either transmit diversity system.