Research On IA-RWA Algorithm Based On Flooding Mechanism With Segmentation In Optical Networks

With the evolution that optical networks turn to one with high data rates, dynamicand transparent structure, the devices in electric field, such as OEO and opticalregeneration equipments, gradually disappear. It makes the communication to be in halfor whole part of optical field in optical networks, which can improve the economicbenefits and effectively reduce energy consumption. However, it also makes the adverseeffect caused by the physical impairments in optical layer become more and moreserious. So far, there have been quite a lot of researches on the physical impairmentsproblem and its extensions and the most important one is the design ofimpairments-aware routing and wavelength assignment algorithm (IA-RWA). Comparedwith the traditional RWA algorithm, the IA-RWA algorithm will consider the effectcaused by physical impairments on optical signal in the communication path betweentwo nodes, and calculate the best or better path to ensure the transmission quality oflight path. With the intensive study, IA-RWA algorithm is being improved. How tomake the algorithm more accurate, fast running and how to be better adapted to thedemands in the networks have become a hotspot of current researches.Against this background, the paper has been in-depth study of the IA-RWAalgorithms in transparent optical networks, analyzed the working principle andimproved the algorithms. A new algorithm is proposed for transparent optical networks,which named directed flooding IA-RWA algorithm based on mechanism ofsegmentation monitoring-control. Main research results are as follows:(1) In this paper, the importance of establishing impairments models to considerthe combined effect of physical impairments for accurate routing has been analyzed. Ithas reviewed the existing physical impairments models and the routing algorithmmechanisms and pointed out the deficiencies of the existing model and algorithms.(2) A pulse width model based on their combined effects on signal distortion isproposed, and the results indicate that comprehensive consideration of the effectscaused by combined physical impairments is conductive to accurately avoid moreserious physical impairments during routing and reduces blocking rate.(3) The segmentation monitoring-control mechanism is proposed. The mechanismis to reduce the holding time of networks resources for the most effort. It disposes of the candidate path by segmenting the path suitably，and the transmission quality of the pathwould be monitored. It makes the networks control layer keep the transmission qualityof data in monitoring. The simulation results show that the mechanism can effectivelyreduce the blocking probability of networks connections. It brings a better solution tothe competition problem for resources between the probe flow and the main data to betransferred, and it is more suitable for scheduling control in large-scale networks.(4) To improve the performance of IA-RWA algorithm, this paper constructed asimplified model of impairments through analysis of the characteristics of variousphysical impairments and it could be an alternative to the classic model. With thesimplified model, this paper proposed a directed flooding IA-RWA algorithm. Thealgorithm allowed the source node to send PATH packets to the destination nodethrough different candidate paths. These PATH packets could collect path information ofvarious links in the selected path. The information converged at the destination nodeand would be calculated and compared. It avoided re-routing. The simulation resultsindicate that the new algorithm can effectively reduce the algorithm time, increase theprobability of success to establish connections and reduce networks blocking rate.Further, when the algorithm is working with the segmentation monitoring-controlmechanism for optical signal transmission quality monitoring, it is possible to makebetter networks performance.