A new technique for analyzing asymptotic outage performance of diversity over lognormal fading channels

Existing asymptotic analysis techniques fail to provide closed-form asymptotic outage probability expressions for lognormal fading channels due to the fact that lognormal fading channel distributions have an infinite diversity order. In this work, we develop a new analytical technique to study the asymptotic outage probability of maximum-ratio combining and equalgain combining over independent lognormal fading channels. The derived closed-form asymptotic expressions, which can be expressed in terms of the well-known Marcum-Q function, are accurate in high signal-to-noise ratio (SNR) regimes. The results reveal insights into the long-standing problem of asymptotic analyses for diversity systems over lognormal fading channels, and can help circumvent the time-consuming Monte Carlo simulation and numerical integration in large SNR region.