Constrained MMSE-RAKE receivers for DS/CDMA systems in multipath fading channels

The constrained minimum mean square error (CMMSE)-RAKE receivers for multipath fading channels are analyzed. In particular, it is shown that for known channels the output signal-to-interference and noise ratio (SINR) of the CMMSE-RAKE receiver with a single constraint(Type 1) is greater than or equal to that of the CMMSE-RAKE with multiple constraints(Type 2). For Type 1 CMMSE-RAKE receiver, a maximum likelihood (NIL) channel estimate is derived. Computer simulation results indicate that CMMSE receivers improve the bit error rate (BER) as compared with the conventional RAKE and currently available adaptive MMSE receivers, and that Type 1 performs the best.