Dual diversity over log-normal fading channels

A great deal of attention has been devoted in the literature to studying the bit error rate (BER) performance of diversity combining systems in the presence of Rayleigh, Rice, and Nakagami-m fading. By comparison the literature is relatively sparse in comparable analyses over log-normal channels which typically characterize shadowing from indoor obstacles and moving human bodies. One reason for this disparity stems from the difficulty in evaluating the exact average BER when log-normal variates are involved using, for example, the moment generating function (MGF) approach due to the inability of expressing the MGF itself in a simple closed form. Since however, it is possible to evaluate the marginal and joint statistical moments of a log-normal distribution in closed form, we rather focus here on two other performance measures, namely, average combined output signal-to-noise ratio and amount of fading both of which depend only on these moments. Closed-form expressions are obtained for these two measures corresponding to maximal-ratio combining (MRC), selection combining (SC), and switch and stay combining (SSC) schemes allowing for the possibility of correlation between the two branches.