Random algorithms for scheduling multicast traffic in WDM broadcast-and-select networks

We develop and analyze simple algorithms for scheduling multicast traffic in wavelength division multiplexing (WDM) broadcast-and-select networks with N nodes, W wavelengths, and a single receiver per node that can be tuned to any of the W wavelengths. Each message is addressed to k randomly chosen nodes. Since optimal message scheduling in a WDM network is known to be very difficult, we study two simple 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 a 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. We also consider a number of receiver algorithms for selecting among multiple simultaneous transmissions and show, through simulation, that an algorithm where the receiver selects the message with the least number of intended recipients performs better than a random selection algorithm. Finally, we show that channel utilization can be significantly increased with multiple receivers/node.