Reporting in ONUs with reduced buffers

In this work, we consider a passive optical network (PON) with reduced buffer capacity at the Optical Network Unit (ONU). The objective is to reduce the ONU power consumption by having smaller buffers. This requires that some of the end-nodes packets be buffered at the end-node itself (EN) and some buffered at the ONU. These packets will be used to fill the upstream transmission time slot allotted to the ONU by the optical line terminal (OLT). Thus, the REPORT duration intimated by the ONU to the OLT should consider the EN buffer backlogs. This problem is similar to Minimum Makespan scheduling (MMS) with multiple processors. Since this problem is NP-Hard, we have considered three heuristics for computing the transit queue lengths and three sequencing strategies for filling the buffers at the ONU. With the help of simulation based performance studied, it is observed that the choice of sequencing strategy dominates the network performance followed by the choice of heuristics. The sequencing strategies that aggressively buffer packets at the ONU result in higher packet delay.