A Collision-Free MAC Protocol for Optical Star LANs

A new multiple access protocol is developed for optical local area networks based on a passive star topology. The protocol uses wavelength division multiplexing (WDM), and combines the advantages of both random-access and scheduled-access sharing schemes, e.g., fixed pre-assigned TDMA and WDM, into a protocol that is highly bandwidth-efficient. No central control is required among users, and the amount of processing required by each station is small. Time is divided in fixed-sized slots. Before transmitting its data, a station must compete with others for the right to use a slot in a pre-assigned wavelength, using a collision-free procedure. This results in a protocol that is suitable for networks where the number of users is larger than the number of available channels. The scheme can operate with at least a single tunable transmitter/receiver pair in each station. The paper includes an analysis of the maximum throughput and delay characteristics of the presented scheme. Several models are also developed and compared to the results obtained from numerous simulations. Kcy~cords: Optical LANs; Multiaccess protocols; Wavelength division multiplexing