Wavelength Assignment Algorithm in WDM Network

Abstract

Wavelength assignment is a unique feature in wavelength routed networks that distinguishes them from conventional networks. Wavelength assignment methods are classified into mostused, first-fit, random and wavelength conversion algorithm. In random algorithm a set of wavelengths that can be used to establish the connection is determined. After that wavelength is randomly select with uniform probability distribution from the set. In most-used algorithm selects the wavelength most often used in the network. The objective of this policy is to keep more wavelengths available for calls traveling over long paths. This algorithm requires communication overhead and storage requirements. Further in first fit algorithm numbers all wavelengths, so that when there is a demand for wavelengths available, those of a smaller number are considered first. The first available wavelength is then selected. This algorithm does not require global information system. Its computational cost is lower because no storage is needed to keep the network states and wavelength conversion wavelength assignment algorithm can assigned any incoming light-path to any wavelength on the output side. This eliminates wavelength-continuity constraints. We analyze the performance of First-fit, Random, Most-used and Wavelength conversion Algorithms for wavelength assignment in WDM unidirectional optical ring network. We compare the blocking probability of various algorithms with the variation in number of events. The performance of the wavelength conversion algorithms is best but there is a burden of using expensive hardware. But without the need of wavelength-convertor mostused algorithm performs better than random and first-fit algorithms. Further we examined the blocking probability of the network for different algorithm based on total number of wavelengths. We show that as we increases the number of available wavelength then blocking probability decreases. In the last, we analyze the blocking probability of the network for wavelength conversion algorithm based on route length in the eight nodes WDM unidirectional optical ring network. Fiber lengths at every link vary one by one and calculate the blocking probability. We show that as we increases the length of route then blocking probability increases