The issue of burst losses imposes a constraint on the development of Optical Burst Switching （OBS） networks. Heavy burst losses strongly affect the Quality of Service （QoS） intended by end users. This article pres...The issue of burst losses imposes a constraint on the development of Optical Burst Switching （OBS） networks. Heavy burst losses strongly affect the Quality of Service （QoS） intended by end users. This article presents a QoS aware Routing and Wavelength Allocation （RWA） technique for burst switching in OBS networks. The RWA problem is modeled as a bi-objective Integer Linear Programming （ILP） problem, where objective functions are based on minimizing the number of wavelengths used and the number of hops traversed to fulfill the burst transmission requests for a given set of node pairs. The ILP model is solved using a novel approach based on a Differential Evolution （DE） algorithm. Analytical results show that the DE algorithm provides a better performance compared to shortest path routing, which is a widely accepted routing strategy for OBS networks.展开更多
A layered algorithm by bidirectional searching is proposed in this paper to solve the problem that it is difficult and time consuming to reach an optimal solution of the route search with multiple parameter restrictio...A layered algorithm by bidirectional searching is proposed in this paper to solve the problem that it is difficult and time consuming to reach an optimal solution of the route search with multiple parameter restrictions for good quality of service. Firstly, a set of reachable paths to each intermediate node from the source node and the sink node based on adjacent matrix transformation are calculated respectively. Then a temporal optimal path is selected by adopting the proposed heuristic method according to a non-linear cost function. When the total number of the accumulated nodes by bidirectional searching reaches n-2, the paths from two directions to an intermediate node should be combined and several paths via different nodes from the source node to the sink node can be obtained, then an optimal path in the whole set of paths can be taken as the output route. Some simulation examples are included to show the effectiveness and efficiency of the proposed method. In addition, the proposed algorithm can be implemented with parallel computation and thus, the new algorithm has better performance in time complexity than other algorithms. Mathematical analysis indicates that the maximum complexity in time, based on parallel computation, is the same as the polynomial complexity of O(kn2-3kn+k), and some simulation results are shown to support this analysis.展开更多
文摘The issue of burst losses imposes a constraint on the development of Optical Burst Switching （OBS） networks. Heavy burst losses strongly affect the Quality of Service （QoS） intended by end users. This article presents a QoS aware Routing and Wavelength Allocation （RWA） technique for burst switching in OBS networks. The RWA problem is modeled as a bi-objective Integer Linear Programming （ILP） problem, where objective functions are based on minimizing the number of wavelengths used and the number of hops traversed to fulfill the burst transmission requests for a given set of node pairs. The ILP model is solved using a novel approach based on a Differential Evolution （DE） algorithm. Analytical results show that the DE algorithm provides a better performance compared to shortest path routing, which is a widely accepted routing strategy for OBS networks.
文摘A layered algorithm by bidirectional searching is proposed in this paper to solve the problem that it is difficult and time consuming to reach an optimal solution of the route search with multiple parameter restrictions for good quality of service. Firstly, a set of reachable paths to each intermediate node from the source node and the sink node based on adjacent matrix transformation are calculated respectively. Then a temporal optimal path is selected by adopting the proposed heuristic method according to a non-linear cost function. When the total number of the accumulated nodes by bidirectional searching reaches n-2, the paths from two directions to an intermediate node should be combined and several paths via different nodes from the source node to the sink node can be obtained, then an optimal path in the whole set of paths can be taken as the output route. Some simulation examples are included to show the effectiveness and efficiency of the proposed method. In addition, the proposed algorithm can be implemented with parallel computation and thus, the new algorithm has better performance in time complexity than other algorithms. Mathematical analysis indicates that the maximum complexity in time, based on parallel computation, is the same as the polynomial complexity of O(kn2-3kn+k), and some simulation results are shown to support this analysis.
