| It becomes new character of Internet that wireless network and Mobile Computing have developed rapidly. People want to access network resources at anytime and any place with any method. In wireless network, due to the property of high bite error rate, mobile handoff, unstable link state and high bandwidth delay product, the traditional TCP-based congestion control mechanism suffers great performance degradation. Based on the new characteristic of wireless network, the paper adopts network measurement technology to improve the existing congestion control mechanism, which can improve the performance of network transmission.This paper firstly analyzes the existing congestion control mechanism of wireless network; secondly discusses the reason of congestion, criteria and the performance of network when congestion occurs; thirdly introduces several kinds of typical existing congestion control technology of wireless network. At last the paper analyzes the advantage and disadvantage of each congestion technology and their development situation.Then the end-to-end measurement technology based on wireless network is studied, the relationship between measurement parameters and congestion control is analysized, the method of network delay measurement (including One-way Delay and RTT-Round Trip Time) and the bandwidth measurement are given. In addition, the paper gives innovative algorithm of timing synchronization which is called Time-Syn in the measurement of One-way Delay, then verifies the improved algorithm Time-Syn correct and effective through the real network experiment.At last, based on measurement technique, the paper proposes an improved algorithm, and compare the two algorithms with NS2, verifying the improved algorithm effective and feasible.The paper has done the following two jobs:1. It presents time synchronization algorithm called Time-Syn aiming at eliminating defect of the time asynchronization between sender and receiver. Time-Syn eliminates clock skew and clock delay with NTP (Network Time Protocol) and Convex Set algorithm, which improves the accuracy of measurement results, then verifies the improved algorithm correct and effective through the real network experiment.2. Based on measurement technology, this paper presents an improved TCPW algorithm, which is called TCPW-V. The improved algorithm judges the types of packet loss through the two network parameters of RTT and bandwidth, then analysizes the reason of packet loss. When the packet loss is owing to congestion, we apply TCPW-V to network, which can reduce the delay jitter, improve the packet transmission rate, increase the throughput and improve the performance of the network effectively. The algorithm can deal with the wireless network congestion effectively and greatly improve the performance of wireless network. In the end, the paper simulates the two algorithms with NS2 and analysizes their performance criteria, which verifies the feasibility of TCPW-V. |
