A new DBA algorithm for reducing delay and solving the over-granting problem of long reach PON

The main problem of the deployment of long reach passive optical network (LR-PON) is that it suffers from larger propagation delay. Multi-thread polling (MTP) based dynamic bandwidth allocation (DBA) algorithm is one of the solutions to mitigate the larger propagation delay in the LR-PON system. However, in the conventional online MTP based DBA scheme, over-granting problem is severe. In this paper, we propose a new online MTP based DBA algorithm namely slotted MTP (S-MTP) scheme, where each time cycle is divided into multiple grant scheduling slots and, in each slot, multiple request and grant messages are processed simultaneously including the use of frame by frame information in both the request and grant messages. The proposed S-MTP scheme effectively reduces the end-to-end packet delay and over-granting problem in the LR-PON system with lower computational complexity. We have evaluated the performances of the proposed scheme by numerical simulations. The simulation results show that the proposed scheme provides 45% and 20% lower end-to-end packet delay with 38% and 10% lower over-granting rate than the conventional online MTP and enhanced interleaved polling with adaptive cycle time schemes, respectively. The S-MTP scheme also provides higher throughput and bandwidth utilization than those of the existing schemes.