Improving blocking probability in the optical WDM networks

Abstract

While a session request is assigned to a wavelength-routed optical WDM networks, which are circuit-switched in nature, the challenge of routing and wavelength assignment (RWA) is to calculate the optimal path between two nodes, and further is to assign an available set of wavelengths along this path. An algorithm called Total wavelengths and Expected available wavelengths (TEW) proposed by Pavarangkoon et. al. in order to achieve effective routing and wavelength assignment formulates a link weight function and considers this as the main factor for route selection. This function is calculated by using a determination factor of the number of wavelengths that are being used currently and are supposed to be available after a certain time. However, this algorithm tends to overload paths with smaller weights and higher utilization while lightly loaded paths with slightly lower capacities may remain unused. In this paper, propose an improvement to the TEW algorithm by incorporating the frequency of usage of the paths in the weight function and running Dijkstra's shortest path algorithm to choose paths that have more total and expected available wavelengths and less frequency of usage. The proposed algorithm is called as Countered Total wavelengths and Expected available wavelengths (CTEW) algorithm. The impact of the proposed algorithm on blocking probability is investigated by means of computer simulation and by comparing it with TEW algorithm. The results show that the proposed algorithm can achieve better performance in terms of blocking probability.