Impact of Nonidentical Branches on the Switching Rate of Generalized Selection Combining in Rayleigh Fading Channels

In this paper, we extend the switching rate analysis of M out of N generalized selection combining (GSC) in an earlier paper of Cavers and Ho to the case of nonidentical branches. Despite the fact that nonidentical branches introduce a correlation between the difference of the Mth and the M + 1th strongest signals u(t) and its derivative u acute(t), we were able to derive an analytical expression for the switching rate of the GSC receiver under this condition (independence between u(t) and u acute(t) is crucial in obtaining the simple results in Cavers and Ho). Our numerical results agree with the intuition that having nonidentical branches reduces the switching rate. The more dissimilar the branches are, the larger the reduction. While this lowering of the switching rate allows the GSC receiver more time to dwell on the selected signals, hence producing more accurate channel estimates for coherent combining, the bit-error rate of GSC, unfortunately, is higher when the branches are not identical.