We analyze the error performance of an improved hybrid selection/maximal-ratio combining (H-S/MRC) technique called minimum selection H-S/MRC in flat Rayleigh fading for coherent digital modulation schemes. Here the minimum number of diversity branches are selected such that their combined signal-to-noise ratio is above a given threshold. We derive a closed-form expression for the distribution of the number of selected branches. This distribution is used to obtain the symbol error probability.

This paper analyzes the error performance of an improved generalized selection combining (GSC) technique called minimum selection GSC (MS-GSC) in flat Rayleigh fading for coherent digital modulation schemes. Here the minimum number of diversity branches is selected such that their combined signal-to-noise ratio (SNR) is above a given threshold. The threshold chosen here is determined by the combiner output SNR rather than individual branch SNRs as done in absolute threshold GSC (AT-GSC) and normalized threshold GSC (NT-GSC). As a result, MS-GSC uses less resource than AT-GSC or NT-GSC to give the same performance. We obtain a closed-form expression for the distribution of the number of selected branches followed by a closed-form expression for the characteristic function (c.f.) of the combiner output SNR. This c.f. is used to obtain the symbol error probability for different digital modulation schemes. Numerical results for M-ary phase-shift keying are presented as an example.