Performance analysis of multi-branch switched diversity systems

We investigate the performance of both switch and stay combining (SSC) and switch and examine combining (SEC) multi-branch diversity schemes. We first derive generic formulas for the cumulative distribution function, probability density function, and moment generating function of the combiner output signal for both schemes. We then capitalize on these expressions to obtain closed-form expressions for the outage probability and average error rate for various communication scenarios of interest. As a byproduct of our analysis we prove that for SSC with identically distributed and uniformly correlated branches, increasing the number of branches to more than two does not improve the performance but the performance can be different in the case the branches are not identically distributed. We also show that, in general, the SEC performance improves with additional branches. The mathematical formalism is illustrated with a number of selected numerical examples.