Acknowledgement techniques of random access based media access protocols for a WDM photonic environment

Abstract

This paper evaluates acknowledgement schemes for random access based media access protocols for star-coupled WDM networks. Each node requires a fast wavelength tunable transmitter and a slow/fixed receiver. The multiple, multi-access channels are pre-allocated to the nodes for data reception. Each data packet has to be acknowledged by the destination node to indicate successful transmission since the channel cannot be sensed. One solution to providing acknowledgements is to extend the transmission slot: each transmission consists of a data transmission phase and an acknowledgement phase. At the end of the slot, the source node would know if transmission was successful if collisionless acknowledgement transmission is ensured. However, this approach degrades with increased propagation delay and processing latency. An alternative technique eliminates the acknowledgement phase by requiring explicit acknowledgements from the destination node. The relative advantages and drawbacks of the two schemes are studied, and the impact of the acknowledgement scheme on protocol performance is examined. Protocol performance, measured in terms of average packet delay and network throughput, is studied with respect to system scalability, sensitivity to propagation delay, packet processing latency and transmitter tuning latency.