Analysis And Improvement Of TCP Performance For Ad Hoc Networks

Ad Hoc network is an multi-hop and temporary self-automation system composed of mobile terminals with radio equipments.It is a new type of wireless communication network.Ad Hoc network is widely applied into many fields for its great flexibility.The applied fields includes many areas where traditional wire and wireless network can not functionjust like arm equipments, urgent rescue, temporary meeting and etc. At present, TCP protocol is a end-to-end transmission protocol universally used on Internet.It can support a wide range of business on Internet including WWW,FTP,E-mail,Telnet and etc.So using TCP protocol in Ad Hoc network is very necessary.Traditional TCP protocol's design was just concerning about wire network.It contributes the loss of data package to network congestion and employ congestion-control process to solve the problem.The traditional TCP protocol is not appropriate for the speciality of Ad Hoc network environment.As the loss of data package in Ad Hoc network may be resulted from node movement,error of wireless channel or something else.Traditional TCP protocol can not correctly find the reason for package loss and just conduct congestion-control,leading to the decrease of TCP performance.So it is crucial to improve traditional TCP to make it fit into Ad Hoc network.The dissertation firstly gives a brief introduction of the features and application fields of Ad Hoc network,especially elaborates MAC protocol and routing protocol of Ad Hoc network.Through simulated experiment,we analyze the effect of the MAC protocol,route protocol and the preference of TCP CWL(Congestion Window Limit) on the performance of Ad Hoc network. Lastly,we propose a TCP improving scheme employing end-to-end identification on the basis of analysis of present scheme. Using the feature of data's one-way transmission latency,this schema firstly calls the receiver side to identify the network state.Then the sender side will take according measures in light of network state information carried by back ACK data package. Practice has proved the feasibility and efficiency of the proposal by the simulating experiment.