Spreading Code Allocation for Downlink MC-CDMA

The paper illustrates that multiple access interference (MAI) can be reduced by re-ordering the spreading codes in multi-carrier code division multiple access (MC-CDMA) systems. An effective spreading code allocation procedure using simple least square (LS) channel estimation is presented to reduce the MAI in downlink MC-CDMA systems. Moreover, the spreading codes chosen by the method are in a consistent sequence. Using this code selection method, the system capacity of MC-CDMA can be effectively increased without increasing the system complexity. Simulation results show that the presented method can work well for both time-invariant and fading channels.