A Collisionless Multiple Access Protocol for a Wavelength Division Multiplexed Star-Coupled Configuration: Architecture and Performance Analysis

This paper introduces a collisionless wavelength division multiple access protocol for a passive star-coupled photonic network and shows that it possesses significant performance and flexibility advantages over alternative approaches. A performance modeling technique is introduced, basedon a semi-markov analytic model, that eliminates many of the unrealistic assumptions of past approaches to analytical modeling. The performance of the protocol is analyzed using this analytical model and discrete-event simulation. The proposed protocol is control channel based: one WDM channel is used to reserve access for data packet transmission on the remaining data channels. Control channel access arbitration is achieved through time-division multiplexing, enabling all active nodes the opportunity to transmit once every control cycle. This approach significantly reduces the long synchronization delays typical of time-division multiplexing systems: the control cycle length is proportional to the control packet size rather than the data packet size. Every node in this system has one tunable transmitter and two receivers. One receiver continuously monitors the control channel to receive all control packets. The other receiver is tunable, and is used to receive data packets on any data channel. This protocol eliminates packet collisions since the control channel receiver tracks busy data channels and destinations. The proposed approach has the advantage that variable sized data packets in a collisionless environment are supported without utilization degradation. Furthermore, a mechanism is introduced that relaxes the constraints on the switching times of the optical components by decreasing the performance sensitivity. The performance is evaluated in terms of network throughput, packet delay, and control and data channel utilization. In particular, this paper examines the performance impact with variations in the number of nodes and data channels, packet generation rate, data packet length, and the optical device switching latencies. The performance of the proposed protocol is compared to the DT-WDMA protocol proposed in [1].