Periodic GATE Optimization with QoS-awareness for Long-Reach Passive Optical Networks

In this paper, we propose a bandwidth allocation scheme working with differentiated services for the Multi-Point Control Protocol (MPCP) in Long-Reach Passive Optical Networks. The proposed scheme is an enhancement to our recently proposed bandwidth allocation scheme Periodic Gate Optimization (PGO), and it is called Periodic Gate Optimization with Quality of Service Awareness (PGO-QoS). Long-Reach PON introduces a challenge by the deployment of passive elements in a long distance up to 100km between the OLT and the ONUs. It becomes more challenging when the subscribers have different Service Level Agreements (SLAs) with specific performance requirements such as delay bounds and/or packet drop probabilities. PGO-QoS consists of two independent modules; intra-ONU scheduling and dynamic bandwidth allocation. Intra-ONU scheduling stands for the burstification of the buffered packets at the ONUs, and it determines the proportion of the packets to be dequeued from the buffer of each SLA class. These proportions are also appended to the REPORT message to be used by the OLT in the dynamic bandwidth allocation module. The bandwidth allocation module runs at the OLT. This module is mostly inherited from recently proposed PGO. Based on the collected REPORT messages, the OLT periodically builds an ILP model to estimate the appropriate GATE credits of the overloaded ONUs until the next optimization period. The ILP model sets the appropriate constraints so that the OLT tends to prioritize the ONUs where dequeuing proportions of the high priority queues are greater. The simulation results show that PGO-QoS leads to a lower average delay and shorter queue length and less packet delay. Moreover, the proposed scheme also introduces decreased delay and low packet loss for the higher priority SLA classes which are class-3 and class-2.