| Summary: | 碩士 === 淡江大學 === 電機工程學系 === 88 === Recently, optical communication was widely deployed in the backbone network due to the higher transmission rate and lower bit error rate. In the optical communication, one of the important techniques is wavelength division multiplexing (WDM) technique. The WDM is an effective way of utilizing the large bandwidth of an optical fiber. It allows multiple messages to be transmitted in parallel. In a number of channels, the technique has the potential to significantly improve the performance of optical networks.The asynchronous transfer mode (ATM) has been selected as the switching technique for use in the public broadband ISDN (B-ISDN). In the viewpoint, a good hardware design constructs a practical ATM-based switching system. The complexity of the edge router for supporting the fixed length (53 bytes) cells and translation the different format of packets in the TDM switching technique, they will become the bottlenecks of the backbone network.In this paper, we present two kinds of sequencing strategies for variable-length packets in WDM networks. First, we will propose a novel Optical IP Router (OIR) architecture and a fast processing concept to transmit IP packets between LAN and backbone network. The non-TDM based OIR architecture with a Multiple Packets Scheduling Algorithm has the ability to support the switching of variable-length IP packets. Based on the concept, the switching processing time will be reduced due to without the segmentation procedure and the format translation. Besides, the utilization of bandwidth will also be increased by deleting the overhead of header of ATM cells.Second, we will propose sequencing techniques for variable length packets by using Genetic algorithm. Packets sequencing and channel assignment are two important issues that need to be addressed when scheduling variable length packets in WDM network. Channel assignment addresses the problem of choosing an appropriate data channel via which a packet is transmitted to a node. On the other hands, packet sequencing which addresses the order in which packets are sent. In order to unleash single-hop WDM passive star network, efficient scheduling algorithm are needed to allocate and coordinate system resources optimally, while satisfying packets and system constraint. Genetic algorithms have recently received much attention as stochastic search algorithms for various optimization problems. This class of methods is based on the principles of natural selection and natural genetics that combine the notion of survival of the fittest, random and yet structured search, and parallel evaluation of nodes in the search space. Base on the concepts, The sequencing strategy that use Genetic algorithm can address both packet sequencing and channel assignment aspects of the scheduling problems simultaneously.The first proposed OIR architecture we proposed in this paper can improve the switch utilization, the throughput, processing delay and the packet loss ratio. In addition, we will use the OIR as a switch element (OIRSE) to construct a scalable optical router based on the MIN architecture to increase the service capacity. The second packets sequencing strategy can improve the performance significantly since the scheduling algorithm which using genetic algorithm can optimize the consideration of packets sequencing and channel assignment simultaneously.
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