Lightpath affiliation graph wavelength assignment approach for mesh WDM network planning

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Lightpath affiliation graph wavelength assignment approach for mesh WDM network planning


Author: Woo, Ka-chung Andrew
Title: Lightpath affiliation graph wavelength assignment approach for mesh WDM network planning
Degree: Eng.D.
Year: 2011
Subject: Light -- Wave length.
Wavelength division multiplexing.
Optical communications.
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Engineering
Pages: xvi, 161 p. : ill. ; 30 cm.
Language: English
InnoPac Record:
Abstract: Nowadays, telecommunications operators are expanding the coverage and capacity of their transport networks to cope with the proliferation of emerging telecommunications applications. During the last two decades, our technology choices for optical transport networks are limited to ring-based Synchronous Optical Network (SONET) and fixed Dense Wavelength Division Multiplexing (DWDM). Recently, the mesh-type wavelength routed networks are gaining practical acceptance with the commercial availability of reconfigurable DWDM systems that can steer lightpaths amongst multiple interface ports to enable direct point-to-point traffic routing. One of the critical tasks on designing wavelength-routed network is to optimize wavelength resource assignment. Even though network design engineers have acquired much experience in deploying ring-based networks, the computational complexity of wavelength resource assignment remains challenging for mesh optical network design. Efficient design tool is a must to fully exploit the benefits of mesh optical network. Besides, telecommunications operators are also exploring the feasibility of offering wavelength-leasing service to enterprise customers. From engineering perspective, the variety of customer-end optical interfaces could be minimized and fault identification could be expedited if wavelengths are assigned based on affiliated lightpaths. In view of these practical needs, an intuitive Lightpath Affiliation Graph (LAG) heuristic is proposed, developed and evaluated in this thesis.
Graph theory technique was adopted once I recognized the similarity between Wavelength Assignment Problem (WAP) and Maximum Clique Problem (MCP). I have implemented the heuristic LAG approach based on the exact solution to MCP presented in graph theory literature as well as Edge Disjoint Path (EDP) approach for performance benchmarking. Integer Linear Programming Approach (ILP) approach, which can give exact results but not practical for large problems, was also implemented to compare the accuracy of LAG and EDP approaches for small problems. Extensive simulations were performed with network models generated by Georgia Tech Internetwork Topology Generator (GT-ITM). I found that the computational performance could be improved using a simplified clique search approach, known as basic LAG approach, which makes use of the special property of triangulated graph to reduce the solution time. A modified version, known as enhanced LAG approach was also developed. Simulation results show that the enhanced LAG approach yields comparable performance to EDP approach for general applications. Simulation results also show that the performance of enhanced LAG algorithm improves as network density increases. I have also shown that it is possible to make use of the intuitive nature of LAG heuristic to solve practical provisioning problem. Through proper abstraction and formulation, this study fertilizes subject knowledge transfer from graph theory to practical engineering applications and introduced an intuitive LAG heuristic with performance on par with the fast and efficient EDP approach to exploit the benefits of mesh optical networks.

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