Research On Bandwidth Allocation And Congestion Control In Optical Fiber Access Networks

It is widely believed that media service will be one of the major applications in future IP networks, and IP over optical networks will be a major component of the next generation IP network because optical fiber access networks can provide high-speed and large-capacity transmission. But media service have their own characteristic, they need quality of service(QoS) in transmission. Media data may be introduced into network by optical access devices, then be transmitted in network. So it need to support quality of service in these devices according to media service characteristic.The QoS is stille an hot topic with great challenge in optical fiber access networks. In order to guarantee the transmission quality of medium traffic in optical fiber access networks, our thesis focus on the key technologies of the researches on bandwidth allocation and congestion control. The major contributions of this thesis are as follows:(1)This paper proposes a novel dynamic threshold algorithm at media traffic level for shared buffer packet switches, known as Dual-dynamic Threshold Algorithm based on E-Model(EDTA). The EDTA strategies for buffer management and congestion control strategy are applied in exchanging devices for flow medium in optical fiber access networks, such as switches and routers. EDTA divides buffer management of switch into two parts:the global threshold strategy and the queue threshold strategy. The global threshold strategy controls the shared buffer by a whole threshold through judging different traffic scenarios to ensure good transmission performance in all situations. The queue threshold strategy decides and adjusts output queue threshold based on E-Model traffic levels, which transforms several medium service quality effecting parameters into users' psychological factors, thus guarantees the quality of flow medium data. On the other hand, EDTA improves the QoS of multimedia stream in network by detecting and discarding these packets that accumulated delay exceeds multimedia stream's delay tolerance so as to maintain high bandwidth utilization. All kinds of packets are firstly classified into queues according to their own priorities which calculated by accumulative delay. Experimental results show that the proposed algorithm (EDTA) can improve the traffic performance for flow media more effectively, achieve better quality of network flow medium transmission, comparing with those algorithms using traditional control. And it is suitable to be used in any network condition and can improve the utilization of the network resources. The EDTA algorithms and schemes have been implemented and available on a 384/768Gbps switch. The idea of EDTA has been published in Journal of Computer Research and Development, Computer Science and in proceedings of the International Society for Optical Engineering.(2)A dynamic bandwidth allocation algorithm based on gate threshold was proposed to provide efficient and fair utilization of the Ethernet passive optical networks (EPON) upstream bandwidth and support QoS requirements of different traffic classes. The algorithm uses optical network unit (ONU) data-receiving rate to decide whether the current state is at high payload or at low payload, and further adjust optical line terminal (OLT) receiving data gate threshold from ONU. At high payload state, it lengthens polling cycle, shortens channel idle time and increases network throughput; at low payload state, it shortens polling cycle and increases data transmission. The algorithm decided the data-receiving rate from the ONU according to the ONU data-sending response rate and the gate threshold; implemented three methods to adaptive adjust the gate threshold, and analyzed these methods'characteristic. Experiments show this algorithm can decrease average packet delay and increase network throughput in 10G EPON. The algorithm for EPON system have been implemented on a 10G EPON OLT designed for the project "Research on key technology and system of next generation optical access" of Open Foundation of State Key Laboratory of Optical Communication Technologies and Networks(Wuhan Research Institute of Posts & Telecommunications). The idea will be published in Journal of Software, and has been published in Journal of Chongqing University(English Edition).(3)The authors propose the so-called high utility ONU grant scheduling policy based on Euclidian distance by the quasi-human strategy to solve ONU grant scheduling techniques for wavelength division multiplexed Ethernet passive optical networks (WDM EPONs), and take a scheduling theoretic approach to solving the grant scheduling problem. After formulate the joint grant scheduling and wavelength assignment problem as the rectangles packing problem, An effective heuristic algorithm is present, and the solution to the joint grant scheduling and wavelength assignment problem for WDM EPON can be obtained quickly by applying this algorithm. Simulation experiments show the grant scheduling algorithm can decrease average packet delay and increase network utilization. Results indicate that improvements may be obtained in the network performance. The idea will be published in Journal of Communication.(4)A new double local search algorithm(DLSA) for solving the multicast aggregation tree in networks is presented. It is aggregate multicast tree for wavelengths bandwidth allocation in medium data transmitting by multicast in optical fiber networks. The objective of this kind of multicast aggregation algorithm is minimizing the bandwidth wastage ratio subject to the constraints that the number of wavelength affects the aggregation results. A new priority aggregate rule based on the greedy strategy is proposed to generate initial solution, and proposed a new concept of neighborhood structure which is based on greedy strategy. DLSA search effectively in two kind neighborhood structures, and some off-trap strategies are proposed to jump from local optimal solution and carry the search to the feasible areas in promising directions. Simulation experiments show the double local search algorithm can aggregate multiple multicast group, and decrease the amount of aggregation multicast tree, and the results indicate that improvements may be obtained in different network condition. The idea of DLSA has been published in proceedings of the 5th international Conference on Wireless Communications, Networking and Mobile Computing and 2009 International Conference on Computational Intelligence and Software Engineering.The paper has applied for two patents, one is "Threshold of Buffer Management Strategy for Transmission Quality of Medium Traffic", and the other is "A Novel Dynamically Bandwidth Assignment Method for Ethernet Passive Optical Network". The author has written 16 papers about this paper. The first and the second innovation item have applied in some scientific research projects, and these projects and their measurement had been checked and accepted.