Multi group dynamic bandwidth allocation scheme in long reach PONs

With the progress in optical technology, the span of the Passive Optical Network (PONs) grows from 20 km to 100 km or even larger, known as super PONs or Long Reach PONs (LR-PONs). Because of the long span, an LR-PON can server many Optical Network Units (ONUs). In addition, since Optical Line Terminal (OLT) and ONUs are placed at a long distance from each others, the propagation delay of data and control signals between OLT and ONUs is long compared with traditional PONs. Since this long propagation delay increases packet delay and decreases channel utilization, it is an important challenge in an LR-PON. In this paper, we propose a new Dynamic Bandwidth Allocation (BDA) scheme called Multi Group DBA (MG-DBA) to improve utilization and to decrease packet delay. In MG-DBA, ONUs are classified into several groups. Therefore, when one group is sending its data to the OLT, the bandwidth for another group is simultaneously calculated. In addition, the OLT uses the Smallest Available Report First (SARF) for bandwidth calculation for each group to minimize packet delay. Simulation results show that the proposed MG-DBA algorithm can significantly reduce packet delay and improve channel utilization.