Downlink performance and complexity evaluation of equalisation strategies for an MC-CDMA ‘4G’ physical layer candidate

This paper focuses on the performance of equalisation strategies for a downlink MC-CDMA (Multi Carrier-Code Division Multiple Access) based system. MC-CDMA is a leading candidate modulation/multiple access scheme for so called 4th Generation communications. Simulation results utilising Maximum Ratio Combining (MRC), Equal Gain Combining (EGC), Orthogonal Restoring Combining (ORC), and Minimum Mean-Squared Error Combining (MMSEC) for multi-user scenarios are presented. Performance is characterised by bit error rate (BER) for the downlink. A time domain least square channel estimator was implemented along with a frequency based pilot estimation scheme and comparisons made with perfect channel estimation. A complexity analysis of each equalisation scheme is also undertaken. Performance results show that MMSEC provides the best performance for the multi-user scenario as MRC and ultimately EGC both enter error floors as the number of users increase in a wideband channel thereby reducing their usefulness as multi user equalisation schemes