Dynamic Bandwidth Allocation Algorithm For XG-PON

With the increasing trend of optical fiber cables in broadband, PON has been one of the key technologies attracting attention of various telecommunication operators in the world. It is also the basic technology for "Wide-band Speed Acceleration","replacement of copper cables with optical fiber cables" project. XG-PON is a mid-term Evolution scheme for PON, which can expand GPON standard because its being compatible of present GPON ODN.The dissertation discusses the research background, development status, technical advantage, relevant protocol, global structure, key technologies, and information security, and analyzes impact of dynamic bandwidth allocation (DBA) to XG-PON. It describes TC hierarchy, studies its upstream and downstream frame, explains the meaning and effect of some fields in the frame, which lays basis for further algorithm development. It also analyzes relevant key definitions and working principle of XG-PON DBA.Based on the above analysis and research, the dissertation discusses present DBA algorithms, makes inductive analysis for representative DBA algorithms according to T-CONT allocation and service allocation, describes their advantages and shortcomings, then presents a new XG-PON DBA algorithm combining variable cycle and flow prediction after performance analysis and consideration of current conditions of technical implementation. The algorithm abandons the classification of T-CONT in GPON DBA algorithm, and introduces transfer descriptors for T-CONT based on four different kinds of bandwidth according to its priority to make bandwidth allocation more flexible. The flow prediction in the algorithm makes OLT to calculate bandwidth requirement of T-CONTs more accurately, meanwhile the variable polling cycle combined in the algorithm makes the algorithm to handle sudden businesses better.A XG-PON simulation model is established in network simulation software OPNET Modeler, and our DBA algorithm’s performance is simulated on this model. Simulation results shows that our DBA algorithm works well in utilization ratio of bandwidth, guaranteeing capability for the drop and delay, and service quality, and complies with protocol standards. It is a dynamical bandwidth allocation algorithm which can meet the requirements of full grades of service and achieve high service quality.