Contents I. Introduction
The nodes in Ad Hoc network are able to move. Without the limitations of network infrastructure, they are easy and flexible to use. However, frequent mobility of nodes and the limitation of wireless transmission distance will lead to frequent breakage on the links of the active paths. As a result, this may cause the failure of routing information. If not timely reconstruct the path of failure, it will lead to the loss of data packets and the increases of data transmission delay. In addition, the competition and conflict of the wireless shared channel also cause the loss of packets. The commonly used method to determine link failure can not distinguish between causes of packet loss; it will give the same report to the network-layer as link error. These “failure of false link” reports call for additional routing discovering process; waste network bandwidth; increase the packet transmission delay; and result in deterioration of network performance. In the unicast protocol of Ad Hoc network, when a node moves around frequently, according to the better performance of on-demand routing protocols[2], comparing the most important two on-demand routing protocols AODV and DSR, AODV protocol performance is better than that of DSR and its scalability is also stronger than DSR under a condition of frequent node movement and heavy load of network[4].
