Date of Award

8-2009

Degree Name

Doctor of Philosophy

Department

Computer Science

First Advisor

Dr. Ala Al-Fuqaha

Second Advisor

Dr. Dionysios Kountanis

Third Advisor

Dr. Ajay Gupta

Fourth Advisor

Dr. Bilal Khan

Abstract

Most wireless networks are deployed strictly in the radio frequency (RF) domain, since RF channels provide natural support for radial broadcast operations. However, the downside of RF channels is that they introduce many limiting externalities that make providing scalable quality of service (QoS) support difficult, if not intractable. These well-known technical challenges include bandwidth scarcity, lack of security, high interference, and high bit error rates.

Faced with such daunting obstacles to QoS, the use of Free Space Optics (FSO) for wireless communications has been proposed in which it has the potential to support higher link data rates compared to present RF technology. Furthermore, because FSO uses directed optical transmissions in which channel beam-width is adjustable, inter-FSO communication interference can be limited. Finally, the avoidance of radial broadcasting also provides some degree of security against eavesdropping. The benefits of FSO do not come without a price, most notable of which is the need to maintain line of sight (LOS) between the transmitter and the receiver during the course of communication. Moreover, FSO link availability can be degraded by adverse weather conditions like fog, rain, snow, and haze. In this research work, we propose a topology control solution that meets QoS requirements in hybrid RF/FSO mesh networks using joint power and beam-width control. But deciding to use a hybrid model brings with it, its own set of unique problems, stemming in large part from the fact that nodes can choose between two different channels types-each with its own transmission characteristics. Given this, steps must be taken to prevent a relay node in a multi-hop connection from being tempted to behave selfishly by forwarding other nodes' packets using the less reliable channel type, thereby avoiding the individual opportunity cost that would be incurred by a "fairer" choice of allocating a high quality link. We address this problem of selfish behavior by formulating node decisions within a hybrid RF/FSO network in a Bayesian game-theoretic model that is designed specifically to guarantee optimal cooperativeness.

Access Setting

Dissertation-Open Access

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