Performance evaluations of adaptive modulation over composite Nakagami-lognormal fading channels

The closed form expression for the sum of composite Nakagami-lognormal distributions is hard to obtain. Numerical integration approximation to the sum distribution provides sufficient accuracy but is too complicated to apply into further analysis. In this paper we investigate a simple analysis approach based on the least square method, which achieves the accuracy of numerical integration and has a simple expression. The approximation formula is specified and optimal values of coefficients are tabulated for reference. We further use the proposed analysis approach in analyzing the performance of adaptive transmission systems over MRC combined Nakagami-lognormal channels. Simple and closed form expressions for throughput and outage probability are also derived. Impact of different parameters of Nakagami-lognormal channels on the adaptive transmission system is discussed at the end.