Congestion Control Scheme For Wireless Network

With the increase of the wireless network users and the growing demand ofcommunications in the network, network congestion is becoming more frequent. How to ensurestability of data stream and secure transmission in the network becomes a growing concern ofthe research scholars.TCP protocol ensures reliable communication of the network nodes; it is the most widelyused protocol of end-to-end transport in the wired network. Wireless channel is not reliable, ithas a high error rate and mass delay, the performance of TCP in the wireless network is notwell. Therefore, for the wireless network congestion problems, the researches have proposed avariety of schemes, which are mainly divided into: Segmented connection scheme, end-to-endscheme, the link layer scheme, the combination scheme of TCP and other protocol layer. In alarge number of studies based in the wireless network congestion, TCPW (TCP Westwood) isan ideal algorithm. When ACK compression or the packet response delay occurs, TCPW mayoverestimate actual available bandwidth of the network. To resolve this problem, an inprovedTCPW is proposed in this paper.Additionally, this article also studied congestion controlscheme with TCP and the network layer protocol used in conjunction, proposed a variableintegral PID algorithm. The simulation result verify that the two programs both can controll thecongestion well, track network status in real time, and adjust the network congestion timely.In this paper, the work and the research results are as follows:1. The analysis of the wireless network environment, the hot and difficult of the congestioncontrol strategy, and the status of congestion control; the analysis of the TCP protocol in thewireless network.2. For the TCPW overestimate the network available bandwidth value, propose a TCPWimprovement program. The new algorithm solves the network asymmetry caused by the TCP return path of the transmission path and the problem TCPW overestimate the availablebandwidth value. Through simulation analysis, the new algorithm has better throughputperformance, track network status better than TCPW.3. Studied the use of network congestion control with the TCP and the network layerprotocol compatible, proposed a variable integral PID algorithm to resovle the large overshootof the PID algorithm. When unexpected data stream injecte into the network, the PID algorithmoften has a large oscillation. The main idea of the variable integral PID algorithm proposed inthis paper try to change the integral term cumulative speed, with corresponding to the size ofthe queue length: The larger of the deviation and the slower of the integral speed; the smaller ofthe deviation and the faster the speed. With the simulation analysis, the variable integral PIDalgorithm is more effective than PID, PI and RED.