Circular arc graph based algorithms for routing scheduled lightpath demands in WDM optical networks

In WDM optical networks, depending on the offered services the service provider will have precise information for some traffic demands such as the number of required lightpaths and the instants at which these lightpaths must be set-up and torn-down, known as scheduled lightpath demands (SLDs). It may so happen that in a given set of SLDs, some of the demands are not simultaneous in time, and hence the same network resource could be used to satisfy several demands at different times. In this paper we develop two complementary algorithms-independent sets algorithm (ISA) and time window algorithm (TWA), based on circular arc graph theory, which respectively capture time-disjointness or time-overlap that could exist among SLDs. We compare and evaluate the algorithms based on the number of wavelengths required, number of reused wavelengths, average call acceptance ratio, and the reuse factor. The numerical results obtained from simulation experiments indicate that TWA reuses significant number of wavelengths (reuse factor up to 53%) followed by ISA (reuse factor up to 14%).