An adaptive subcarrier allocation scheme for MC-DS-CDMA systems in the presence of multiple access interference

We propose a subcarrier allocation scheme for multiple access MC-DS-CDMA systems, where random signature sequences are used to identify the users. The optimal solution to such a subcarrier allocation problem has its complexity grows exponentially as the number of users and subcarriers grow. We proposed a sub-optimal method. In our proposal, each user performs channel measurement, orders the subcarrier channel gains and feedback the information in the order of the subcarriers channel gains to the base station. The base station uses these information from all users, together with the previous subcarrier assignment matrix, adaptively generates the next subcarrier assignment matrix for forward link transmission, with the objective to minimize the overall system BER performance. While selecting the subcarriers, we take into consideration the multiple access interference.