Efficient DBA Algorithms for Delay Reduction and Solving the Over-granting Problem of Long Reach PON

Abstract

The conventional open access optical network (OAN) with point to multipoint structure needs active components to cover large number of users in a wide area. Requirement of more active components significantly increase the network deployment costs. Cover large range congregation of point to multipoint networks is one of the effective solutions to reduce the network deployment costs. This idea offers the long-reach passive optical network (LR-PON) concept with 100 Km spanning the conventional OAN without any active components between sources to destination. However, the LR-PON involves larger propagation delay as well as end-to-end packet delay compared to the conventional PON system, i.e., spanning distance of 20 km. These delays significantly degrade the performances of the LR-PON with the existing centralized dynamic bandwidth allocation (DBA) algorithms. That is why advanced DBA schemes compatible to the LR-PON are required to reduce its longer propagation as well as end-to-end delays. Proper scheduling of the Report and Gate messages is one of the main challenges to design a new DBA algorithm for the LR-PON. Without proper scheduling of the Report and Gate messages, the LR-PON system suffers from over-granting problem. In this thesis, we propose two DBA schemes, i.e., scheme1 and scheme2, for the LR-PON system. The scheme1 is used to reduce the end-to-end packet delay while the scheme2 is used to mitigate the over-granting problem. In the scheme1, the maximum length of a time cycle is subdivided into multiple units called grant processing units and rapidly grants the window size to each optical network unit (ONU). In the scheme2, in the Report message, each ONU sends the frame information instead of total buffer occupancy to avoid the over-granting problem. The combined effect of the scheme1 and scheme2 effectively improves the overall quality of services (QoSs) of the LR-PON system. The performances of the proposed schemes have been evaluated by numerical simulations. The simulation results also have compared with the three existing DBA schemes, i.e., enhance interleaved polling with adaptive cycle time (E-IPACT), multi-thread polling (MTP), and conventional single thread poling (STP), in terms of end-to-end packet delay, bandwidth utilization, over-granting rate, computational vi complexity, and throughput. It shows that the proposed schemes can ensure the enlargement of the LR-PON system with better QoSs.