On the performance analysis of composite multipath/shadowing channels using the G-distribution

Composite multipath/shadowing fading environments are frequently encountered in different realistic scenarios. These channels are generally modeled as a mixture of Nakagamim multipath fading and log-normal shadowing. The resulting composite probability density function (pdf) is unfortunately not in closed-form, thereby making the performance evaluation of communication links in these channels cumbersome. In this paper, we propose to model composite channels by the very general G-distribution. This pdf arises when the log-normal shadowing is substituted by the Inverse-Gaussian one. This substitution will prove to be very accurate for several shadowing conditions. In this paper we conduct an exhaustive performance evaluation of communication systems operating in these channels. Our study starts by deriving a closed-form expression for the outage probability. Then, we derive the moment generating function of the G-distribution, hence facilitating the calculation of average bit error probabilities. We also derive closed-form expressions for the channel capacity for three adaptive transmission techniques, namely, i) optimal rate adaptation with constant power, ii) optimal power and rate adaptation, and iii) channel inversion with fixed rate. The different expressions that will be provided are of great importance in assessing the performance of communication systems in composite channels.