Research On Upstream Dynamic Bandwidth Assignment Algorithm Based On T-CONT Round Robin In GPON

With the popularity of Internet and broadband application development, user demand for bandwidth increases rapidly. Backbone network can provide a rapid growth of available bandwidth. Network capacity pressure began to turn to the access network. Thus, narrowband access devices become the bottleneck of network performance. Among kinds of broadband access techniques, Fiber to the Home is accepeted as a kind of excellent intergrated solutions for access network. GPON supports high speed rate, high efficiency, full service QoS and flexible service access method. Therefore, GPON is regarded as the key technology of the next generation FTTH system and one of the best choices for broadband aceess network in the future.GPON uses TDM broadcast mechanism to send data frames in downstream direction. While multiusers use TDMA method to share upstream bandwidth resource. Compared to static bandwidth assignment algorithm, a set of well-designed dynamic bandwidth assignment algorithm can ensure full service QoS and increase the system bandwidth utilization under the premise of service fairness. Thus, research on DBA technology is of great significance.Firstly, this paper discusses background of GPON and its development status. Then, it analyzes the working principle of GPON, the function of its parts and key technology from the point of GPON system structure view. Secondly, according to ITU-T G.984 standard, this paper gives a detailed study of GPON transmission convergence layer protocol stack, its structure and key techniques such as GEM encapsulation and T-CONT. Finally, referring to round robin DBA algorithm and a kind of relative QoS guarantee DBA algorithm applied in EPON, the paper presents a set of GPON upstream DBA algorithm based on T-CONT round robin. Upstream bandwidth resource is assigned according to different T-CONT priority in the algorithm. The simulation results prove that this algorithm can well support packet delay and delay variation specified in ITU-T standard. It is a highly efficient GPON DBA algorithm that can satisfy QoS requirement and guarantee multi-service fairness.