| Summary: | 碩士 === 國立彰化師範大學 === 資訊工程學系 === 95 === Wavelength Division Multiplexing (WDM) network is composed of physical topology and virtual topology. Each link in the physical topology represents a fiber in the WDM network and each link in the virtual topology represents a lightpath. Communication requests are transmitted by sending packets on a dedicated wavelength of the lightpath between the source node’s transmitter and the destination node’s receiver. Following the development of virtual topology design technique is more mature, the consideration of survivability of WDM network is more important. Since huge data packet is transmitted in one connection. In order to avoid the data loss owing to fiber failure, protection scheme should be developed to tackle this problem. Another significant topic is virtual topology reconfiguration except survivability. For the reconfiguration, it can adjust parts of link in virtual topology so that upgrade the performance of virtual topology when the virtual topology isn’t suitable. To compare with virtual topology design again, reconfiguration could upgrade entire network performance effectively.
this thesis is studied the virtual topology reconfiguration problem of WDM network with survivability and reconfiguration constraints. Given the physical topology, virtual topology and traffic demand matrix, the goal is to reconfigure virtual topology under the reconfiguration constraint r so as to minimize the objective value. The objective value is the average weighted propagation delay. Since finding a polynomial time algorithm to solve it is impractical when the reconfiguration constraint r is larger, two heuristic algorithms are proposed to solve it: positive reconfiguration heuristic algorithm (PRHA) and conservative reconfiguration heuristic algorithm (CRHA). Since the heuristic algorithm may trap into local optimal, in this thesis, a genetic algorithm (GA) is also proposed to search near optimal solution.
Experiment results reveal that the objective value can be decreased effectively by using proposed heuristic algorithms and genetic algorithm. The difference in improvement ratio between optimal solution and the result found by proposed algorithm is acceptive. From the observate of experiment results, the CRHA is better than PRHA when the spare resource is poor, otherwise the performance of PRHA is better than CRHA. Furthermore, GA outperforms two heuristic algorithms and can get better solution.
Keywords：WDM、survivability、reconfiguration、genetic algorithm、dedicated protection
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