Efficient Joint Scheduling and Sizing of Transmission Grants in Multichannel WDM PONs

Bandwidth allocation and transmission grant scheduling are problems of particular interests to multichannel Passive Optical Networks (PONs). While a number of studies have been carried out on each of these subproblems separately, to the best of our knowledge a study on the joint problem has been lacking. In this paper, we investigate the joint problem of bandwidth allocation and transmission grant scheduling in multichannel optical access networks using a scheduling theoretic approach. We formulate the problem as an ILP model and compare it with the sequential model presented in pervious work. Our experiments declare that the joint scheduling and sizing algorithm achieves a reduction of up to 28% in scheduling cycle length when compared to the non-joint models. Since the model has shown to be very hard to solve, except for small sized network instances, we introduce a Tabu search heuristic for the joint problem that provides near optimal solutions in significantly shorter times. We also illustrate that the choice of buffer size of ONUs has a critical rule in the performance of our joint scheduling and bandwidth allocation solutions.