Browsing by Author "Zhalehpour, Sasan"

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Outage capacity and throughput analysis of multiuser FSO systems
(IEEE, 2015) Zhalehpour, Sasan; Uysal, Murat; Dobre, O. A.; Ngatched, T.; Electrical & Electronics Engineering; UYSAL, Murat; Zhalehpour, Sasan
In this paper, we investigate the performance of free space optical (FSO) systems with a multiuser scheme employing select-max scheduling technique. Specifically, we consider an FSO communication system which employs a central node equipped with N transmit apertures, each of which aimed to any of the users. Under the assumption of log-normal turbulence channels, we derive closed-form outage capacity and outage throughput expressions for the FSO communication system and demonstrate the effect of the outage probability, number of users and average signal-to-noise ratio on the system performance.
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Outage performance analysis of mth best path selection protocol in FSO communications
(IEEE, 2014) Zhalehpour, Sasan; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Zhalehpour, Sasan
In this paper, we investigate the performance of free space optical (FSO) systems with parallel multihop relaying and path selection. Specifically, we consider an FSO communication system which employs M parallel relaying paths each of which consists of N decode-and-forward relays. We assume the deployment of the so-called mth best path selection (m-BPS) protocol. 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. Under the assumption of log-normal turbulence channels, we derive a closed form outage probability expression for the FSO communication system with m-BPS protocol and further confirm the accuracy of derived expression through Monte Carlo simulations.
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Performance analysis of multiuser free space optical communications
(2014-08) Zhalehpour, Sasan; Uysal, Murat; Uysal, Murat; Demiroğlu, Cenk; Aldırmaz, S.; Department of Electrical and Electronics Engineering; Zhalehpour, Sasan
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.
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Performance of multiuser scheduling in free space optical systems over atmospheric turbulence channels
(IEEE, 2015-10) Zhalehpour, Sasan; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Zhalehpour, Sasan
In this study, the authors consider a multiuser multiple-input multiple-output (MU-MIMO) free space optical (FSO) communication system and investigate the performance of various scheduling protocols which provide different degrees of tradeoff between throughput and fairness. In the MU-MIMO FSO system under consideration, the central node and each user node are equipped with multiple transmit and receive apertures and equal gain combining is employed at the receiver side. Round robin, opportunistic round Robin, select-max and mth best user selection scheduling protocols are employed. The authors derive closed-form outage probability expressions for each scheduling protocol over log-normal turbulence channels assuming non-equidistant placement of users. The authors further present Monte Carlo simulations to confirm the accuracy of derived expressions.