Theoretical Performance Analysis of Downlink Site Diversity in an MC-CDMA Cellular System

The downlink (base-to-mobile) bit error rate (BER) performance for a mobile user with relatively weak received signal in a multicarrier-CDMA (MC-CDMA) cellular system can be improved by utilizing the site diversity reception. With joint use of MMSE-based frequency domain equalization (FDE) and antenna diversity combining, the site diversity operation will increase the downlink capacity. In this paper, an expression for the theoretical conditional BER for the given set of channel gains is derived based on Gaussian approximation of the interference components. The local average BER is then obtained by averaging the conditional BER over the given set of channel gains using Monte-Carlo numerical method. The outage probability is measured from the numerically obtained cumulative distribution of the local average BER to determine the downlink capacity. Results from theoretical computation are compared to the results from computer simulation and discussed. key words: MC-CDMA, site diversity, downlink capacity, outage probability, MMSE-based FDE, antenna diversity