WDM/SCM multiple access protocol with high throughput and low packet delay for passive double star networks

This paper investigates a hybrid wavelength division multiplexing (WDM) multiple access protocol combining the advantages of preallocation and reservation-based schemes using a subcarrier multiplexing (SCM) technique for passive double star optical networks. We include a node-grouping scheme in the proposed protocol to increase channel utilization and to reduce sensitivity to queueing delay time and propagation delay time. All nodes in a network are connected through passive star sub-hub forming multiple groups, and the groups are then connected through a central passive star hub resulting in a passive double star network. Each group is pre-assigned a WDM channel as its home channel, and a specific SCM channel identifies each node. In the proposed protocol, the frame is divided into slots corresponding to the number of groups, not the number of nodes. The reduced number of slots results in reduction of queueing delay time. Furthermore, additional reduction in the propagation delay time of the control packets is achieved by limiting the propagation paths of the control packets to the roundtrip between source nodes and sub-hub in a double star network.