Research And Simulation Of DBA Algorithm In GPON System

With the rapid development of Internet technology, the rise of a large number of data,voice and video business, the necessary of user for bandwidth is becoming higher and higher,the total capacity of the entire Internet consumption also has reached an unprecedented height.In order to meet the bandwidth requirements of the users, GPON(Gigabit Passive Optical Network) came into being, and it has become the mainstream of access network technology.GPON successfully become the first choice of some mainstream operators because of its further transmission, higher bandwidth, faster speeds and greater coverage of technology.The DBA(Dynamic Bandwidth Allocation,) algorithm as the core technology of GPON,has become a hot topic in the field. Through analysis of existing DBA algorithm we found two main types: state report DAB and predictive DBA. Although the Status report DAB can be more accurate allocation of network bandwidth, but there is often tend to high cost and high network delay. Predictive DBA algorithm use the corresponding prediction mechanism,while overcome the network delay and high cost problems, but the prediction data and the actual data tend to have some errors, can not guarantee the accuracy of bandwidth allocation.To sum up, we can see that the existing algorithms is difficult to take into account network latency, network overhead and bandwidth allocation accuracy problems, often leads to low bandwidth utilization, network delay and cannot guarantee the QoS of the business. Therefore,we need to design an algorithm which can guarantee the bandwidth utilization of the system in the case of reducing the network delay.Through the necessity description of GPON key technology, highlighting the importance of dynamic bandwidth allocation algorithm in GPON system. In this thesis, aiming at the shortcomings of the existing DBA algorithm, to design and implement a efficient DBA algorithm which can achieve a balanced system of network delay and bandwidth utilization.Based on the analysis of the network structure and the key technologies of GPON system, we have combined the existing DBA algorithm, proposed a Dynamic Bandwidth Allocation algorithm which is a hierarchical polling strategies based on the forecasting mechanism. The algorithm uses the idea of prediction and hierarchical polling strategies to achieve dynamic bandwidth allocation in the GPON system. this paper presents the principle and detailed step of the algorithm. Finally simulation model was established based on OPNET network simulation tools, The average delay of high and low load two scenarios of the system through the simulation experiment, and two kinds of dynamic bandwidth allocation algorithm with the experimental results(C-DBA algorithm and AR-DBA algorithm) are compared. The final experimental results show that: compared with C-DBA algorithm and AR-DBA algorithm,this algorithm guarantees the QoS business, at the same time, also reduces the system timedelay and it has the advantages in the respect of system bandwidth usage rate and bandwidth distribution efficiency etc.