A Study Of Routing And Spectrum Allocation Strategies In Mixed Networks With Fixed-grid And Flex-grid

In recent years, the network total traffic has an explosive growth because of the development of bandwidth-intensive services such as video on demand and cloud computing. The traditional WDM networks allocate the spectrum resource according to a fixed grid standardized by ITU-T, which lacks of flexibility and causes a huge waste of spectrum, so it cannot meet the requirement of future optical transport network. The flex-grid technology slices the spectrum with a smaller granularity, it can supportGbps sub-wavelength service and high rate super-wavelength service beyond 100 Gbps by spectrum slice combination, which makes it the most promising technology for future optical transmission network. The strategy of upgrading fixed-grid network to flex-grid network is now drawing more and more attention.The paper focuses on the strategy of upgrading the fixed-grid to flex-grid network gradually and the Routing and Spectrum Allocation(RSA) algorithm of the mixed network. Firstly, a new network node architecture called mixed node is proposed, which has a colorless, directionless and contentionless feature. Then, two gradual migration strategy was proposed: the strategy based on bottleneck link and the strategy based on network node. The first upgrading strategy includes the link density strategy and the congestion link strategy, and the second strategy includes the node degree strategy and the node total traffic strategy, their routing and spectrum allocation algorithm is also presented separately. Finally, the paper uses the C language to simulate the migration strategies and RSA algorithm, the result shows that all the strategies made a good performance on network bandwidth blocking rate(BBR) reduction. In the strategy based on bottleneck link, the congestion link strategy has a better BBR performance than the link density strategy in most senarios, but as the link density threshold becomes smaller, the BBR performance of link density strategy is more and more close to the congestion link strategy. In the strategy based on network node, the node degree strategy is a static strategy, and the node total traffic strategy is a dynamic strategy, which has different BBR reduction based on the upgrading node number. When two network nodes are upgraded, they have similar BBR performance.