Unscheduled multicasts in WDM broadcast-and-select networks

This paper considers the problem of scheduling multicast transmissions in a WDM broadcast based local area network. In very high speed networks optimal scheduling may be too time consuming and complex to be executed in real time, thus we are led to consider unscheduled (random) multicast transmissions. We consider two random scheduling schemes: in the first, a message is continuously retransmitted until it is received by all of its intended recipients; and in the second, a random delay is introduced between retransmissions of the same message. We develop an exact throughput analysis for both schemes using methods from discrete-time queueing systems and show that the algorithm with random delays between retransmissions results in higher throughput. Finally, we consider a number of receiver algorithms for selecting among multiple simultaneous transmissions and show that an algorithm where the receiver selects the message with the least number of intended recipients performs better than a random selection algorithm.