Performance trade-offs of different RAKE receivers

We determine the effects of different diversity schemes on the behavior of a direct-sequence spread spectrum RAKE receiver which operates with random spreading sequences, in a multipath channel with arbitrary power delay profile. Two different receiver architectures, the former employing the L instantaneously strongest paths out of the N_r resolved ones, and the latter simply the L first paths out of the received N_r, are confronted in terms of symbol error probability, when an M-level PSK system is assumed. The analytical approach devised for assessing such comparison gives the symbol error probability in terms of simple elementary integrals, and immediately evidences the influence on system behavior of the number of resolved paths, bandwidth occupancy of the signal and power delay profile, with a remarkably moderate computational effort.