PHYSICAL TOPOLOGY DESIGN AND ROUTING ALGORITHMS FOR DEGREE-CONSTRAINED FSO MESH NETWORKS

Free-space optical (FSO) mesh networks are emerging as broadband communication networks because of their high bandwidth (up to Gbps), low cost, and easy installation. However, there are two existing problems in the deployment of FSO networks: the physical topology design problem, and the routing problem. This dissertation presents an algorithm for the physical topology design of FSO mesh networks in order to enhance network reliability under defined degree constraint of each FSO node. The methodology presented enlarges the minimum angle between adjacent links at each node. Simulation results show that, compared to other methods, the proposed algorithm not only provides higher connectivity and lower delay for FSO networks, but also makes the FSO networks so constructed more tolerant in a dynamically changing environment. Further, this algorithm is enhanced to include the 3-dimensional (3-D) space, where the heights of the FSO nodes are not identical. This enhancement will apply to FSO nodes in difficult terrains where it is not feasible or desirable to have the FSO transceivers on a plane.This dissertation also addresses the routing problem in degree-constrained free-space optical (FSO) mesh networks. To solve the routing problem, four different routing algorithms are proposed. Their performances are evaluated through extensive simulations for a number of FSO mesh networks with different topologies and nodal degrees. The performance parameter against which these algorithms are evaluated is the mean end-to-end delay. The proposed least cost path (LCP) routing algorithm, which is based on minimizing the end-to-end delay, is considered as the bench mark. The performance of each of the other three algorithms is evaluated against the bench mark. The proposed minimum hop count with load-balancing (MHLB) routing algorithm is based on the number of hops between the source and the destination node to route the traffic. Simulation shows that the MHLB routing algorithm performs best in most cases compared with the other two. It results in minimum average delay and least blocked traffic

Unified security frameworks for integrated WiMAX and optical broadband access networks

This dissertation proposes the integration of optical and Mobile Worldwide Interoperability for Microwave Access (WiMAX) broadband access networks in order to combine the strengths of optical and wireless technologies and converge them seamlessly. To protect the access network security, this dissertation has developed the design of unified security frameworks for the proposed integrated optical and WiMAX broadband access networks.Ethernet Passive Optical Networks (EPONs) offers a popular broadband access solution, providing high bandwidth and long transmission range to meet users' fast evolving needs. WiMAX provides a wireless broadband solution and it supports mobility. This dissertation proposes a WiMAX over EPON network architecture to provide optical bandwidth for the WiMAX base station (BS). The dissertation also presents a unified security framework for the proposed WiMAX over EPON architecture using public key infrastructure (PKI) and extensible authentication protocol (EAP). The security framework could achieve efficient system management, enhance the system security, and realize unified key management. Furthermore, the dissertation introduces three handover scenarios in the WiMAX over EPON network and describes the corresponding handover schemes based on a pre-authentication method and the communication framework of the ranging step. The proposed handover mechanisms can simplify and accelerate the handover process, compared to the standard WiMAX handover scheme, while keeping the handover procedure secure.Free Space Optics (FSO) provides a relatively flexible optical wireless solution to provide gigabit bandwidth to areas where fiber is costly or hard to deploy. This dissertation also proposes an integrated Mobile WiMAX and FSO broadband access network and presents a unified EAP-based security framework. The dissertation then evaluates and compares the performance of EAP-Transport Layer Security (EAP-TLS) and EAP-Tunneled Transport layer Security (EAP-TTLS) for the FSO-WiMAX network, and also evaluates the impact of the point-to-point FSO link. Measurements show that, compared to EAP-TLS, EAP-TTLS provides a more flexible, efficient, and secure way to protect the integrated FSO-WiMAX access network. Experiments conducted as part of investigation demonstrate that the point-to-point FSO link does not degrade the performance of EAP authentication in the integrated network