Research Of Routing And Wavelength Assignment Algorithm In WDM Optical Networks

With the development of networking technologies and new services of internet, there is an explosive growth trend in internet traffic, which is promoting the construction of broadband backbone network. Wavelength Division Multiplexing (WDM) is a promising approach that can use the enormous bandwidth of the optical fiber. A single fiber can be employed for multiple data streams simultaneously. All-optical networks employing the concept of WDM are considered as the transport networks for the future.A key issue in networks design is to optimize Routing and Wavelength Assignment (RWA) for lightpaths. RWA solves how to find out an appropriate lightpath and assign a wavelength reasonably in order to make full use of the limited resource and provide communication capability as large as possible. In this thesis, firstly, the basic conceptions and existing algorithms for RWA problem are introduced. Secondly, by comparing and analysising the expression of optimizing object of several classical wavelength assignment algorithms, improved the relative capacity influence algorithm which is the best on blocking probability performance now under the condition of no wavelength converters . A new link cost definition strategy is also be proposed and the effect of routing selection algorithm according to the new link cost definition strategy and the improved wavelength assignment algorithm are evalued jointly by simulation. Thirdly, traffic priority and fairness of network are studied , a priority-based wavelength assignment algorithm and other algorithm in which priority and fairness are considered integretily are proposed. These two algorithm improved the dynamic threshold algorithm from different angles. So they can decrease the blocking probability and fit the QoS constraints.The proposed RWA algorithms in this thesis can achieve lower blocking probability than some algorithms existed in literatures and support priorities of traffic. The algorithm can improve the fairness of networks by increasing the blocking probability of shorter hop lightpaths and decreasing the blocking probability of longer hop lightpaths.