On the design of optimal TDM schedules for broadcast WDM networks with arbitrary transceiver tuning latencies

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Abstract
We consider the problem of scheduling packet transmissions in a broadcast, single-hop WDM network. Tunability is provided only at one end, namely, at the transmitters. Our objective is to design schedules of minimum length to satisfy a set of traffic requirements given in the form of a demand matrix. We address a fairly general version of the problem as we allow arbitrary traffic demands and arbitrary transmitter tuning latencies. The contribution of our work is twofold. First we define a special class of schedules which permit an intuitive formulation of the scheduling problem. Based on this formulation we present algorithms which construct schedules of length equal to the lower bound provided that the traffic requirements satisfy certain optimality conditions. We also develop heuristics which, in the general case, give schedules of length equal or very close to the lower bound. Secondly, we identify two distinct regions of network operation. The first region is such that the schedule length is determined by the tuning requirements of transmitters; when the network operates within the second region however, the length of the schedule is determined by the traffic demands, not the tuning latency. The point at which the network switches between the two regions is identified in terms of system parameters such as the number of nodes and channels, and the tuning latency. Accordingly, we show that it is possible to appropriately dimension the network to offset the effects of even large values of the tuning latency.

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