On the Use of Clustering Algorithms for Message Scheduling in WDM Star Networks

Scheduling algorithms in wavelength division multiplexing (WDM) single-hop networks aim at producing an effective schedule in order to improve the networks´ performance. Apart from channel assignment, the message sequencing is an important issue that have to be addressed when designing media access control (MAC) protocols for WDM networks. Up until now, popular approaches have not extensively addressed the order in which the messages are scheduled even though the messages´ service order can considerably contribute to the advance of network performance. This paper introduces a new approach to the design of message scheduling algorithms for WDM star networks, which is based on the use of clustering techniques. The proposed clustering oriented-earliest available time scheduling (CO-EATS) creates groups of nodes whose messages are destined to common nodes. The goal of the proposed CO-EATS scheme is to decrease the probability of scheduling messages to the same destination at successive order. The simulation results have shown that the proposed scheme improves channel utilization and as a result it leads to higher network throughput while it keeps mean packet delay at low levels in comparison with conventional scheduling algorithms.