Two-Phase Minislot Scheduling Algorithm for HFC QoS Services Provisioning

Data-over-cable service interface specifications v1.1 (DOCSIS v1.1) defines five upstream services for supporting per-flow quality of service (QoS). The cable modem termination system (CMTS) must periodically grant upstream transmission opportunities to the QoS flows based on their QoS parameters. This study proposes a two-phase minislot scheduling algorithm to reduce the QoS violation rate. In the scheduling sequence determination phase, the flow whose packets are most unlikely to violate QoS is scheduled first. In the minislot assignment phase, the scheduler allocates to a flow the available interval where the likelihood of packet violation is minimum. Simulation results demonstrate that our scheduling algorithm can reduce the QoS violation rate by 80% - 35% over that of the first-come-first-serve-random-selection algorithm and increase the utilization by 25% as well.