Bit error probability of linear multiuser detectors in the presence of unknown multiple access interference

We investigate the effect of unknown multiple access interference in the bit-error-rate (BER) achieved by linear multiuser detectors. This problem arises in several practical CDMA applications where the receiver may not have full knowledge of the number of active users and their signature sequences (e.g., intercell interference). We consider two linear detectors: the decorrelating and MMSE multiuser detectors. BER is computed for both the AWGN and frequency non-selective fading channels.