Abstract:

The traditional TCP protocol is designed for wired networks, and it is assumed that the packet loss is caused by network congestion. However, in Ad Hoc network, in addition to the congestion loss, other noncongestion factors can also cause packet loss. The main factors affecting TCP performance of Ad Hoc Network are analyzed, and an endtoend TCP congestion control scheme (ImpMMJI) is proposed, which is based on the original congestion control scheme of MMJI. According to the forward path hops, the scheme adaptively adjusts the congestion window size and prevents the excessive growth of the congestion window. When the route changes or link interruption occurs, the scheme can calculate cwnd and ssthresh values of the congestion window in order to ensure the consistency of the TCP connection load rate when the routing is reconstructed. Besides, the scheme adds the state sign bit in TCP header of the ACK reply packet, which combines multiple measurement parameters to judge the network state so as to improve the network state recognition accuracy and make the sender respond in real time. The simulation results show that the scheme can improve the network throughput and the TCP performance obviously.

Key words: Ad Hoc network;end-to-end;TCP;congestion control