Wavelength assignment to lightpaths for minimal wavelength conversions in multihop WDM networks

In multihop WDM (Wavelength division multiplexing) systems, a connection between two communication nodes consists of one or more lightpaths. A wavelength conversion is required at the joint of two lightpaths if they use different wavelengths. Wavelength conversion incurs significant delay in data transmission, and overhead in connection setup. This paper discusses the problem of assigning wavelengths to a set of lightpaths such that the overall number of wavelength conversions in the system is minimized. The problem is formulated as the maximum clique-partition problem and an approximation algorithm is proposed to solve it. We also quantatively analyze the relationship between the number of wavelengths and the number of conversions required in the system. Extensive simulations have been conducted to demonstrate the reduction of wavelength conversions by employing the proposed algorithm.