  This paper studies the ergodic mutual information of hybrid
selection/maximal-ratio combining (H-S/MRC) diversity system under BPSK/QPSK
modulations. We consider a simple single-input multiple-output (SIMO) channel,
where a subset of branches are selected and combined using maximal-ratio
combining (MRC) to maximize the instantaneous Signal to Noise Ratio (SNR) at
the receiver. For independent and identically distributed (i.i.d.) Rayleigh
flat fading, a general recursive expression is developed to estimate the
ergodic input-output mutual information of the whole system. Besides analytical
derivations, simulations are provided to demonstrate the feasibility and
validity of the derived results.
