Flexible-queue-management-based bandwidth allocation in higher-speed PONs

Higher-speed passive optical networks (i.e., ITU-T 50G PONs) are envisioned to support various time-sensitive services with diverse quality of service (QoS) requirements (e.g., latency and jitter). To achieve this goal, higher-speed PON introduces multiple queues in each transmission container (T-CONT) so that each queue can carry a type of time-sensitive traffic. However, in the existing dynamic bandwidth allocation (DBA) schemes, the DBA engine in the optical line terminal (OLT) allocates bandwidth to four types of T-CONTs based on their buffer occupancies and priorities without considering queue status (e.g., the amount of data frames in queues) and services' QoS requirements. To support multiple services belonging to the same T-CONT, the traffic scheduler in each optical network unit (ONU) further assigns the bandwidth of T-CONTs to their associated queues by using priority-based scheduling strategies. In this way, the bandwidth is allocated to queues by the DBA engine and traffic scheduler independently, which cannot guarantee network performance and meet the stringent QoS requirements of time-sensitive services. To solve this problem, we propose a DBA mechanism based on flexible queue management (FQM) to enable direct allocation of bandwidth to the queues under their QoS requirements. The proposed FQM mechanism enables the DBA engine to obtain the arrival time and QoS requirements of data frames in different queues as well as queue status based on the existing report/grant mechanism. By using these parameters, the required bandwidth for each queue in the next polling cycle can be calculated. Then, the DBA engine allocates bandwidth to these queues according to their bandwidth requests and priorities periodically. Simulation results show that the proposed scheme outperforms two benchmarks in the aspects of meeting time-sensitive services' diverse QoS requirements, even when the traffic load is high.