Effect of time-varying user population on the performance of the adaptive combined space-time receiver for DS-CDMA systems

An adaptive combined space-time detector for DS-CDMA system has been proposed by Legnain, Falconer and Sheikh (see IEEE GLOBECOM 98, Sydney, Australia, 1998) to combat cochannel interference and enhance the capacity of the adaptive MMSE multiuser detection. In this paper we study the effect of time varying user population (sudden death and birth) on the performance of the adaptive space-time multiuser detector proposed by Legnain et al. in frequency selective fading channels. Sudden birth of interferers degrades the performance of the adaptive MMSE detector, and the receiver needs to be readapted each time new interferers appear. We show that the adaptive space-time techniques alleviate the effect of sudden birth of interferers and there is no need to retrain the detector each time a new interferer appears or disappears