Analysis And Improvement Strategy Of TCP Performance For Ad Hoc Networks

Ad Hoc Networks has strong independence and flexibility, It can exist as an independent network or serve as an effective complement to the existing network structure. Because of these advantages of the Ad Hoc network, making it a hotspot of current research in the field of mobile communications. Ad Hoc Networks using the wireless channel as a transmission medium, and the nodes move frequently, the traditional TCP protocol designed and developed for wired networks can not meet the Ad Hoc network requirements. How to improve the transmission performance of TCP protocol in Ad Hoc Networks, is the current problems to be solved.The subject analysis works principle of the traditional TCP protocol, and used NS2simulation tool to create the model of Ad Hoc Networks,further validate the transmission characteristics of the Ad Hoc Networks, as well as the specific problems of the traditional TCP protocol is applied to the Ad Hoc network. Pointed out that the MAC layer, the existence of hidden terminal and exposed terminal problems on the TCP performance, and the use of different network layer routing protocol and transport layer TCP version to TCP performance.The subject summarized the improvement of the TCP protocol in Ad Hoc Networks. On this basis, According to traditional TCP protocol can not effectively distinguish between packet loss causes and adapt to frequent route replacement due to node mobility, resulting dramatic decline in transmission performance,we proposed a new improved algorithm called TCP vegas-N, on the basis of TCP Vegas improved slow start algorithm, Base_rtt and rtt values and congestion control algorithms, and use NS2to validate the algorithm in Ad Hoc network performance. Verify that TCP Vegas-N can effectively improve the shortcomings of the traditional TCP protocol,able to solve the traditional TCP can not distinguish between packet loss problems, congestion window size can be adjusted according to the routing hops, TCP protocol in Ad Hoc network transmission performance has been greatly enhanced.