On the wavelength assignment problem of multi-channel photonic dual bus networks

In a multi-channel photonic dual bus network, each unidirectional bus contains a control channel and several data channels (wavelengths), and each station has n tunable transmitters and m tunable receivers. Given a set of serving traffic and a set of new traffic requests, the wavelength assignment problem ((n,m)-WAP) is to assign the transmission wavelengths and receiving wavelengths of each station so that all the traffic requests can be served simultaneously and the number of assigned wavelengths is minimized. In this paper, we prove that the (n,m)-WAP is NP-complete by showing that the simplified version of the (n,m)-WAP (SWAP, or (1,1)-WAP), in which each station has only one tunable transmitter and one tunable receiver, is NP-complete. An efficient distributed wavelength assignment algorithm (DWAA) is proposed for the (1,m)-WAP. The throughput and delay characteristics of the DWAA is evaluated by simulation. Simulation results show that for a limited number of available wavelengths, the solutions obtained by the DWAA is attractive in terms of throughput, access delay, as well as fairness, under general traffic demands.