Research On The Management Of Transfer Control In Concurrent Multipath Transfer

Concurrent Multipath Transfer (CMT), as a new technology to improve network performance, has attracted more and more attention of researchers. CMT aims to aggregate bandwidth with the help of flow control, congestion control, resource management, scheduling, and handover management. As the key technology of the next generation Internet, CMT improved the network utilization, but also increased the difficulties of resource management. At the same time, the way to use mobile terminal to access the Internet is a research hotspot in the future. Then there is a new challenge for resource management, when a mobile terminal is used to realize CMT.This paper focuses on the constrained optimization problem between aggregation bandwidth and limited physical resource, when terminal is used to acess the Internet. Based on the analysis, the resource management model is built to improve performance in CMT. In our proposed model, Stream Control Transmission Protocol (SCTP) is charactered into multiple level round. Based on the model, we can obtain the throughput and resequencing length in Receiver Buffer (RBUF). Optimization theory is also imported to solve the tradeoff problem in CMT. A series of key technology, including flow and congestion control, paths selection, scheduling and handover management, have been discussed. Through the combination of theoretical proof and simulations, the corresponding algorithms and mechanisms are proved.Our work in this paper includes the following parts:(1)This paper studies the flow and congestion control with limted RBUF. Through the experiment, it is observed that bandwidth utilization is low, when RBUF is smaller than the bandwidth delay product. That is because RBUF size affects transfer performance. So how to maximize the bandwidth utilization of the network with limited RBUF is one part of our research in this paper. Here a new transfer control meachnism based on Virtual Receiver Window (RWND) is proposed. This new meachnism achieve the ideal RWND by network measurement. When the real RWND is lower than the ideal RWND, Virtual RWND is used to compensate the time delay of the RWND’s change, in order to make full use of the idle resources network. The simulations show us that the performance of the new transfer control meachnism based on Virtual RWND is imporved.(2)This paper discusses the paths selection problem in CMT. Through the experiment, it is observed that the aggregate bandwidth doesn’t increase with the number of paths, when RUBF is limited. How to select the suitable paths subset with limited RBUF size, to achieve the throughput maximization, is one part of the research in this paper. For the question above, we bring multiple level round, which is used for a new CMT model. Congestion Window(CWND) works together with Slow Start Thresh (SSTHRESH) to denote the space state, while the states transitions are discussed. Based on the analysis above, the aggregate bandwidth and the resequencing length are studied. Based on the model mentioned above, the paths selection problem is formulated as a knapsack problem, which maximizes the overall throughput and limits the resequencing queue length expectation to the fixed RBUF size. Through the computer simulations, the proposed analytical model can predict the throughput of CMT accurately. It is proved that our proposed path selection has achieved much better performance than the others in CMT.(3)Scheduling plays an important role in CMT. In this paper, we analyze why there is RBUF Blocking. How to schedule the packets intelligently is one part of our research in this paper. Based on the study above in this paper, we raise an arriving time prediction model. According to the arriving time prediction, we schedule the packets more intelligently to seek in order arrival at the receiver. Meanwhile we analyze the loss possibility and the RBUF overhead of scheduling packet on certain path. In order to reduce RBUF overhead, we import the idea of Forward Error Correction (FEC) to increase arrival possibility. FEC increases reliability, but also occupies the effective bandwidth. Redundancy scheduling for CMT is formulated as a constrained optimization problem. Here we propose a new redundancy scheduling approach for CMT, which makes a decision about which path to transfer and which key packet should be redundant. Simulations proved that the proposed approach provides superior performance than the others.(4)In wireless mobile network, handover management is the way to keep connection consistenly. Traditionally there is no path running during the handover period, so performance evaluation only takes into account of the paths participating in handover. But in CMT, except for the paths related, there are still other paths running during the handover period. Hence, handover affects both the related paths and the other paths. How to handover intelligently in CMT is one part of our research in this paper. For the new characteristics in CMT, we research handover in this paper. The signaling interaction process of handover is analyzed. Based on the analysis together with the time delay, signaling overhead, a new handover decision model for CMT is built. With the help of the decision model, we introduce the principle of utility maximization in economics, to make the decision in which throughput’s maximization can be achieved. The simulation results show that our proposal can achieve better performance.