Efficient Scheduling and Grant Sizing Methods for WDM PONs

Bandwidth allocation and transmission grant scheduling are problems of particular interest to multichannel passive optical networks (PONs). While prior studies have addressed each of these subproblems separately, to the best of our knowledge, a study on the joint problem has been lacking. In this paper, we first revisit the sequential model and derive a more efficient Integer Linear Program (ILP) for the nonjoint problem that yields up to nearly 12% reduction in makespan and 11% increase in average channel utilization. Then, we investigate the joint problem of bandwidth allocation and transmission grant scheduling in multichannel optical access networks using a scheduling theoretic approach. We derive two ILP models and compare them with the sequential model. Results show that joint scheduling and sizing algorithm achieves significant improvement in terms of scheduling cycle length when compared to the nonjoint models. Since the models for the joint problem was shown to be very hard to solve, except for small-sized networks, we introduce a Tabu search heuristic that provides near-optimal solutions in significantly shorter times. We further perform a packet-level simulation to study the benefit of our new methods.