The Study On The Optical Switching Technology And It's Resource Deployment Optimization Problems

Activity in the area of broadband networking has been expanding at a very rapid rate, it seems the Moore Laws's, which is used to forecast the development trend of semiconductor industry, can't catch the step of people's need in the network broardband field. Therefore, purely adding the hardware or increasly the investment in the infrastructure isn't an efficient way. Currently, it has two main research branches in optical communication field: photonic device and optical networking. Photonic technology mainly focus on the proble how to implement the pure optical packet switching (OPS), which involves the all-optical wavelength converter, optical buffer, optical logical switcher and optical singal processing etc. Optical networking technology mainly study the system architecture and protocols for the large-capacity and high-speed optical switch network. Above-mentioned research branches closely tie together, and continuously push the progress of optical communication field. Our work mainly study the resource optimization problems in the large-capacity and high-speed optical switch network, including RWA ((Routing and Wavelength Assignment) algorithm, contention avoidance mechanism, and novel optical switching network architecture, its objects are to balance the traffic load, decrease data loss rate, improve the network throughput and resource utilization, moreover, provide the good service quality for voice, data or multimedia businesses.Firstly, we take the routing and wavelength assignment (RWA) problem into account. Former works try to solve this problem via heuristic algorithm or graph theory. However, the complexity of the optimization problem grows exponentially as the the size of network grows. In particular for dynamic traffic model, the solution for RWA problem is not only more difficult, but also inexact. In view of these circumstances we propose a dynamic weight RWA algorithm which base on the principle of "Key Link" forecast. We consider the network performance deterioration very possibly derive from certain key links of network firstly, and these key links are related to static factor, such as particular network topology, or dynamic factors, such as wavelength exhausted rate as well as the number of free wavelength. One of most important idea in our proposal is that these "Key Links" should be avoided in advance as possible, then comprehensively takes the hops and free wavelengths into account in order to dynamically choose and assign the optimal route and wavelength for arrival connection requests. Comparing to conventional RWA algorithms, our algorithm can achieve better load balance and lower blocking probability with less computing complexity.Next, a novel optical switching technology called optical time-slot switching (OTS) is presented in charpter 3. Conventional Optical Burst Switching (OBS) network has inherited disadvantages in the aspect of resource reservation mechanism, QoS guarantee and burst contention is more likely to occur in the case of heavy load due to both burst size and assembled time are uncertain in it. With similar control plane mechanism in OBS network, OTS technology divides the wavelength resource into fixed size time-slots as the basic switching granularity of optical network. Also, we mathematically prove the time-slot switching has equivalent function to eliminate data conflict relative to wavelength converter. If the time-slot size and frame length can be set appropriately, as one of promising solution to decrease data contention, optical time-slot switching might reach even exceed the function of wavelength converter. Moreover, OTS technology is capable of providing the virtual connention service via periodically booking the certain time-slots in each frame. We also design a novel architecture for optical time-slot interchanger in this charpter, which can effectively decreae the realization complexity of optical time-slot interchanger.In charpter 4, the routing, wavelength and time-slot assignment problem is discussed. Several effective approaches for time-slot assignment and scheduling, such as Train approach,Wagon approach and p-distribution approach, are proposed in this charpter. Also, a novel adaptive weight factor is introduced into the routing and wavelength selection algorithm in order to dynamically choice the routing and wavelength according to the network resource usage status. Simulation results show our scheme can provide good Quality of Service (QoS) comparing to traditional OBS technology, and has great advantage in decreasing the network blocking probability.A novel proactive contention avoidance mechanism used in OBS network is considered in charpter 5. According to traffic status, one or more than one dedicated wavelength is assigned to each ingress node in OBS network, and bursts will transmit along the dedicated wavelength channel to the destination nodes, thus the potential contention at intermediated nodes can be eliminated partly without wavelength converter or optical delay lines (FDLs), the contention at ingress nodes can be solved via electronic buffer. Further, we construct a traffic load balance spanning tree for each ingress node, where input loads are appropriately balanced among sub-trees according to the degree number of ingress node. Within the spanning tree of identical node, bursts never meet contention, and the wavelength resource ultilization rate also maintains ast a high level. Experimental results show our scheme can improve the network performance of burst drop rate significantly.