Adaptive routing and wavelength assignment using ant-based algorithm

We propose a new ant-based algorithm for solving the dynamic routing and wavelength assignment (RWA) problem in WDM optical networks under the wavelength continuity constraint. To facilitate the ants´ foraging task, we adopt in our algorithm a routing table with the probability for route selection. The new algorithm is highly adaptive in the sense it always keeps a suitable number of ants in the network to cooperatively explore the network states and continuously update the routing tables such that the route for a connection request can be determined promptly by the current states of routing tables with a small setup delay. Some schemes for path scoring and path searching are also proposed to enhance the performance of our ant-based algorithm. Simulation results on ns-2 simulator indicate that the proposed algorithm can adapt well to the traffic variations and it is much better than the fixed routing algorithm and also outperforms the fixed-alternate routing algorithm in terms of blocking probability.