Research And Analysis Of Multi Link Transport Layer Protocol Based On High Speed Mobile Environment

With the rapid development of high-speed railway and mobile Internet, the high-speed mobile Internet has grown up. In this case, the traditional wireless technologies cannot meet people’s growing demand. Thus multilink wireless technology has been proposed to solve the problems, such as low bandwidth, high delay and long hand off delay, as fully as possible via merging the all kinds of wireless resources together, which will be a new trend in the future. How to optimize the multi link transport layer protocol in high speed mobile environment becomes a difficult problem.In this paper, we mainly analyze and study the two transport layer protocols of TCP and MPTCP, and improve the congestion control algorithms and strategies of the two protocols.Firstly,we analyze the performance of TCP protocol on the wireless network and introduce the WTCP scheme.There are deficiencies of WTCP protocol in the error control mechanism in the mobile wireless network.Based on this,a new solution is put forward combined with the link to Freeze of TCP-Freeze protocol.The new protocol of NWTCP is aiming at improving the mobile wireless network transmission performance.There are two main innovations of NWTCP protocol:(1)Through the ACK state information returning from the mobile terminal, the sender reduces or delays sending data,in order to reduce the reaction number of mobile terminal,then save energy;(2)For the frequent handoff of mobile wireless network,when the link is cut,there is not slow start of the send,but freezing.Once the link is recovery,then to send date at original windows,which can improve the network throughput.(3) Network simulation tool NS is used for emulation. The NWTCP protocol is compared with WTCP protocol and TCP protocol, which have been proved outperformed in the aspect of throughput.Secondly,we analysis and compared recent MPTCP congestion control algorithm. Then, we proposed a Bandwidth Estimation-based and Opportunistic Linked Increases MPTCP congestion control algorithm.This paper makes the follow contributions:(1)We analyze the opportunities and challenges of multipath transferring, then introduce and compared the existing MPTCP congestion control algorithms.(2)Developed a MPTCP congestion control model based on Bandwidth Estimation and Opportunistic Linked Increases.This model enables MPTCP to use uncongested paths for data transmission, according to the drop-rate and round-trip time of each path. And also, by estimating the bandwidth of the path, and then increases the congestion window slowly, the algorithm can reduce the possibility of congestion, so improve the throughput of these paths.This new congestion control algorithm is called BE-OLIA. (3)Developed network throughput trend prediction model based on the network throughput estimation model. According to the network throughput trend prediction and network bandwidth estimation, we proposed a new MPTCP congestion control algorithm IBE-OLIA(Improved Bandwidth Estimation-based Opportunistic Linked Increases).(4) Implement these two congestion control algorithms in NS-3,and did some experiments with different congestion control algorithms. The results of these experiments shows that our algorithm can improve the aggregation throughput of the end-to-end communication, and also improve the bandwidth utilization of the network.