Çok kullanıcılı optik kablosuz haberleşme sistemlerinin başarım analizi

Terrestrial Free Space Optical (FSO) communications involve using optical beams to carry information through atmospheric channels between two points. Unlike radio frequency (RF) communications, FSO systems are not burdened by spectrum licensing or interference to/from other systems. These systems are also easy-to-install and redeployable, therefore considered a powerful alternative to fiber optic or RF systems, particularly, for the purpose of "last mile" problem. In addition, the nature of point to point transmission by means of laser beam provides high immunity to interference and jamming from external sources. In the first chapter of the thesis, we provide an overview of FSO technology discussing the advantages and bottlenecks as well as mitigation techniques in FSO systems to overcome atmospheric turbulence induced fading problem. In the second chapter, we consider a multiuser FSO system over log-normal atmospheric turbulence channels. We investigate the outage probability of proposed system with various scheduling techniques including Round Robin, Opportunistic Round Robin, Select-Max and mth Best User Selection. We also verify the validity of the obtained closed-form expressions for outage probabilities through Monte Carlo simulations. In the third chapter, we extend the multiuser scenario to a parallel multihop (cooperative) FSO system and study its outage probability with the so-called mth Best Path Selection (m-BPS) protocol. Specifically, we consider an FSO communication system which employs M parallel relaying paths each of which consists of N decode-and-forward relays. In this protocol, data is transmitted through the mth (m ≥2) best path towards the destination since the best path (i.e., m=1) might not be available due to scheduling or load balancing issues. After expressing closed-form of outage capacity, we derive the diversity order of proposed system. In the last chapter, we derive outage capacity and throughput expressions for the multiuser FSO system under consideration. These expressions are obtained under the assumption of both independent identical and non-identical distributions assuming log-normal channel model and then confirmed through simulation results.