Asymptotic Performance Analysis of Multiuser Diversity in Free Space Optical Communication Systems

摘要

We analyze the asymptotic average throughput of a multiuser diversity (MD) scheme, in the limit of large number of users, for free space optical (FSO) communication systems over a gamma-gamma fading channel. It is assumed that the FSO system consists of an optical transmitter (central node) equipped with K transmit apertures to serve K users (one transmit aperture for each user). It is also assumed that each user is equipped with N receive apertures and equal gain combining (EGC) is employed at the user's receiver. In MD, the central node serves only one user which has the largest channel gain among the K users, while other users remain silent. Using extreme value theory (EVT), we derive a simple and tight upper bound on the asymptotic average throughput of the considered FSO system. Moreover, the asymptotic average bit error rate (BER) is investigated and a closed form approximation for the average BER of the FSO system with MD#x002F;EGC scheme is obtained.