Maximal Ratio Combining in Cellular MIMO-CDMA Downlink Systems

In this paper, we first analyze the performance of maximal ratio combining (MRC) scheme for multiple input multiple output (MIMO) in an interference-limited CDMA cellular system. Different from the previous contributions, our work focuses on downlink for the following reasons: first, downlink has always been the bottleneck of capacity due to asymmetry in traffic loads between downlink and uplink; second, the simplicity of MRC MIMO present more attractiveness in downlink for the strict complexity restriction on mobile stations. We analyze the impact of intra-cell interference as well as inter-cell interference on system performance and derive the outage probability and capacity of the system in a closed-form. Then we compare the performance between MRC-MIMO-CDMA and single input single output (SISO) CDMA systems in respect of outage probability and capacity. The results indicate the efficiency predominance of MRC- MIMO-CDMA over SISO and show that employing more transmit antennas at the base station brings on better performance than using more receive antennas.