Synergized-adaptive multi-GATE polling with void filling: Overcoming performance degradation in LR-PONs

Several dynamic bandwidth allocation (DBA) algorithms have been proposed for long-reach passive optical networks (LR-PONs). The gains in the current protocols, however, are incremental and limited to a specific range of loads. Using an analytical framework, we first examine the main sources of performance degradation specific to LR-PONs. From this, we conclude that there is a large scope for improvement in the performance by using an optimal cycle length, which is not influenced by reach, and which polls users according to their reported load while providing opportunities for pre-granting bandwidth at the optical network units. The fraction of bandwidth that is pre-granted should be decreased with load. To tailor these optimal design concepts in a DBA algorithm, we propose Synergized-Adaptive Multi-GATE polling with Void-filling (S-AMGAV), which reduces both the delay bound and packet loss rate by at least 50% when compared to the state-of-the-art DBAs like interleaved polling with adaptive cycle time (IPACT), IPACT with grant estimation (IPACT-GE), multi-thread polling (MTP), double phase polling (DPP), gate driven (GD), and AMGAV. S-AMGAV also maintains simplicity of the protocol while removing bandwidth inefficiencies prevailing in the existing protocols. We verify the usefulness of the algorithm through both analytical modeling and simulations.