The tradeoff between diversity gain and interference suppression via beamforming in a CDMA system

In this paper, the uplink of an asynchronous direct sequence code division multiple access (DS-CDMA) system with multiple antennas at both the transmitter and the receiver is considered. We analyze the system performance over a spatially correlated Rayleigh fading channel with multiple access interference (MAI). Assuming perfect channel knowledge available at the transmitter, maximal ratio transmission (MRT) is employed to weight the transmitted signal optimally in terms of combating signal fading. Further, adaptive beamforming reception is adopted to suppress MAI and also to combat the fading. We examine the effect of varying the number of transmit and receive antennas on the diversity gain and interference suppression.