Equalized parallel interference cancellation for MIMO MC-CDMA downlink transmissions

The system performance can he improved by interference cancellation and transmit diversity. Due to the flat fading at each narrow band subcarrier and the inter-symbol interference resistance in MC-CDMA, the interference cancellation can be much simpler than that in WCDMA. It is ideally suited to the application of transmit diversify with a very simple linear combination on a sub-carrier basis. In MC-CDMA multicode downlink transmissions, the user equipment has the knowledge of all the assigned spreading codes and it makes interference cancellation more feasible. In this paper an advanced equalized parallel interference cancellation (EPIC) receiver that equalizes the data estimates of previous two stages is proposed for MIMO MC-CDMA systems using space time transmit diversity. By predefining the weights on power of two, the scaling and soft combination required by the proposed EPIC can be implemented by two summations and one bit-shift operation at each stage instead of one summation and two multiplications. The additional required complexity can be reduced into negligible and the proposed EPIC has approximately same complexity as the conventional PIC. The numerical results proved that the proposed receiver could significantly improve the system performance.