Two-stage report generation in long-reach EPON for enhanced delay performance

Long-reach passive optical networks (LR-PONs), as a part of the next generation PON technologies, aim at combining the capacity of metro and access networks so that the telecommunication network topology is simplified and the operational cost is reduced. However, in order to eliminate the delay performance degradation introduced by long propagation distance, LR-PONs call for bandwidth distribution schemes that are different than the existing schemes for conventional PONs. In this paper, we propose a new bandwidth distribution approach which employs a two-stage buffering mechanism at the ONUs and adopts the reduced delay advantage of multi-thread polling. REPORT generator at an ONU generates the requests by using an adaptive burst assembly process. According to the proposed scheme, ONUs maintain time threshold and size threshold values for the upstream input queues. Upon receipt of a GATE message, each ONU runs an adaptive burst assembly procedure to set the appropriate time and size thresholds and determines the bandwidth request of the REPORT message. We evaluate our proposed bandwidth distribution scheme by simulations for the ONU-OLT distances of 20 km and 100 km. The simulation results confirm that consolidation of multi-thread polling and two-stage buffering enhances the delay performance of long-reach EPON (LR-EPON). Furthermore, under heavy loads, the proposed scheme leads to high utilization of the upstream channel.