Performance analysis of a class of multistage DS-CDMA receivers for multipath channels

Performance of the output signal-to-interference-plus-noise ratios (SINRs) and bit error rates (BERs) of the maximum ratio combining (MRC) multistage minimum-mean squared error (MMSE), minimum output energy (MOE), best linear unbiased estimator (BLUE) and maximum likelihood (ML) receivers are analyzed for direct-sequence code-division multiple access (DS-CDMA) systems in multipath Rayleigh fading channels, based on the common multistage structure we proposed previously (Sau-Hsuan Wu et al., Proc. IEEE Globecom, 2002, 2003; Proc. IEEE ICC, 2003). The SINRs of these receivers are proved to be monotonically increasing with the number of applied stages. The upper bound of output SINRs and its achievability conditions are also provided, which are shown to form the condition for the occurrence of BER floors of the multistage MRC MMSE/MOE/BLUE/ML multiuser receivers. A rule for selecting the number of stages is thus provided to take full advantage of the multistage structure of these receivers.