Performance of cooperative CDMA with successive interference cancellation

We investigate the BER and achievable rate of user cooperation schemes in practical uplink CDMA channels with multiple access interference (MAI). It is shown that when the system loading increases, cooperation alone becomes less effective if simple matched filters (MF) followed by combining from each partners' signals are employed for obtaining decision variables. By performing successive interference cancellation (SIC) for each received signals from the partners and then using the maximum ratio combining technique, the diversity gain and hence the uplink capacity is enhanced. We further analyse the output decision variable signals and also provide a simplified bound on achievable rate based on Gaussian Approximation of MAI signals. Illustrative simulation results are given, which confirm that the proposed scheme using SIC achieves much improved diversity and error performance under high system loading and nearfar conditions.