Channel capacity of distributed antenna systems downlink over composite Nakagami fading channel

Abstract

In this paper, the downlink capacity performance of distributed antenna systems (DAS) with antenna selection are investigated in composite Nakagami channel which take path loss, shadow fading and Nakagami fading into account. According to the performance analysis and using numerical integrations, the probability density function (PDF) and cumulative distribution function (CDF) of the effective output SNR of DAS are derived, respectively. Based on these results, tightly-approximate closed-form expressions of channel capacity and outage probability of DAS in composite Nakagami channel are further derived. These expressions include the ones under composite Rayleigh channel as special cases. Conditioned on the outage probability, a practical iterative algorithm based on Newton's method for finding the outage capacity is proposed. To avoid iterative calculation, another approximate closed-form expression of outage capacity is also derived by utilizing the Gaussian distribution approximation. Simulation results show that the derived expressions have more accuracy than the existing ones, and can match the corresponding simulation well. Thus, the capacity performance of DAS in composite Nakagami channel can be evaluated effectively.