An Efficient Multi-Thread Polling based DBA Algorithm for Solving the Over-Granting Problem of Long-Reach PON

The expansion of passive optical network (PON) system into long reach PON (LR-PON) introduced large propagation delay if conventional Report and Grant messages scheduling schemes are used. Without sophisticated arrangement of Report-Grant scheduling, the LR-PON system may suffer from the over-granting problem. Due to this over-granting problem, the overall performance of the LR-PON can affect by overlapping of time slots, requesting same data twice and unused time slots. In this paper, we propose a new Report and Grant scheduling scheme to reduce the over-granting problem with a delay reduction principle. In the existing multi-thread polling (MTP) based DBA algorithms, if the Reported bytes are not matched with the maximum granted window size then it transmits smaller data byte by lower rounding of queued frames and introduced over-granting problem. In the proposed DBA algorithm, all the queued frames information are reported by the ONUs and OLT Grants the number of frames with window size to avoid the over-granting problem. The proposed scheme also distributes the Granted window size among the ONUs based on the fair bandwidth demands. We compare the performance of the proposed scheme with the existing STP and MTP schemes. The comparative result shows that the proposed scheme reduces almost 45% of the average packet delay at maximum offered load 1.0 compared to the existing MTP scheme. The simulation results also show that the proposed scheme provides higher throughput and bandwidth utilization performance than the existing schemes.