A hybrid dynamic reservation protocol for an optical star network

We consider a passive star coupler network, employing wavelength division multiplexing (WDM), where stations are equipped with fixed transmitters and tunable receivers. In such networks, the efficiency of the protocol for coordinating the data transmission between the transmitter and receivers is of critical importance. In this paper, we address this issue and propose a novel hybrid dynamic reservation protocol (HDRP) which combines the attractive features of the Aloha and reservation protocols. At low load, HDRP follows the Aloha protocol, thus eliminating the unnecessary delay caused by the signaling that is required in reservation schemes. At high load, when the performance of the Aloha protocol begins to decline, HDRP automatically switches over to reservation mode where slots may be reserved in advanced. The protocol displays intriguing behavior during the transition phase, as demonstrated by simulation studies. It is also shown that the protocol can attain a throughput of 1 for uniform traffic, as desired. Furthermore, as bandwidth is reserved based on demand, HDRP exhibits far superior performance than pre-assigned TDM schemes. This is particularly true for non-uniform traffic. Additionally, the simplicity of the protocol, as no state information needs to be stored, makes it highly feasible for implementation