ADAPTIVE DETECTION OF DS CDMA SIGNALS IN FADING CHANNELS/

This paper examines the behavior of the minimum mean-squared error (MM SE) receiver in frequency-nonselective-fading channels, It is noted th at the MMSE receiver will often lose phase lock on the desired signal when the desired signal dips into a deep fade, A modification to the M MSE receiver is presented which is demonstrated to function quite nice ly in flat-fading channels, Analytical results for the modified MMSE r eceiver are presented and found to agree very well with simulation res ults, These analytical results are then compared to the theoretical pe rformance of the conventional (i.e., correlator) receiver in terms of both bit-error rate (BER) and capacity, As expected, the modified MMSE receiver was found to offer a substantial improvement in both BER and capacity, Finally, a simple empirically derived formula is given whic h will give a good approximation to the BER of the modified MMSE recei ver in a Rayleigh-fading environment, This formula can also be used to determine the number of users a given system can support, It is noted that as E-b/N-o grows, if is quite feasible to approach 100% channel utilization with the MMSE receiver, whereas a conventional receiver is typically limited to a utilization of 10%-20%.