Performance of combined MMSE beamforming with parallel interference cancellation for overloaded OFDM-CDMA systems

We propose a signal extraction method that combines MMSE beamforming with parallel interference cancellation (PIC) for an overloaded airborne communication environment. By an overloaded array system, we mean that the number of desired signals exceeds the number of distinct antenna elements. We evaluate the performance of the proposed signal extraction method through the use of the bit error rate (BER) simulation. The simulation results show that the MMSE-PIC techniques can support the number of users that is greater than the number of antenna elements in an OFDM-CDMA based airborne communication systems. The results also shows that a 4-stage parallel interference cancellation is sufficient for effectively removing the interference in the system and provide a reliable estimation of a desire user. The effects of the channel estimation error on the PIC performance is also considered.