Scheduling on All-Optical Broadcast-Star WDM Networks with Restricted Tunable Wavelengths

Abstract

In this paper we consider the scheduling problem on all-optical broadcast-starWDM networks with W wavelengths and N nodes. Each node is equipped with one tunable transmitter and one fixed receiver and the tuning time of each tunable transmitter is not negligible. Furthermore, we assume that the amount of available tunable wavelengths in each node is restricted to a fixed value γ which is less than W. Given an off-line uniform traffic matrix, the objective is to design a multi-hop scheduling algorithm to minimize the total transmission time slots. We first present an approach to partition the original star architectures into several rings for efficient packet transmission in later stage. Our algorithm is to construct the minimum number of rings to connect all nodes, the problem can be reduced to a special case of the set cover problem. As γ = (W − 1)/2, we can find an optimal set cover if it exists. For the general case, we design a factor of 2 approximation algorithm to choose suitable rings. When the packets are transmitting in logical topology ring obtained by our algorithms, the tuning time can be overlapped with packet transmission time in our scheduling. Thus, Our scheduling strategy has less propagation delay and total scheduling period than other multi-hop scheduling.