Research On Routing Protocol Of Ad Hoc Network-mprovement OfAODV Routing Protocol

Mobile Ad Hoc network is a group of mobile nodes with wireless transmitters and receivers ,forming a multi-hop temporary self-organized network.It does not require any fixed infrastructure support, Node here has both host and routing capabilities, you can quickly build a mobile network anytime, anywhere. Ad Hoc network is characterized by self-organizing, non-center, multi-hop limited bandwidth, dynamic topology and so on. It has a lot of flexibility and Mobile node can join or leave the Ad Hoc network at any time. Because of these characteristics, traditional routing protocols cannot be applied directly on it. How to provide a stable and efficient route in this particular environment has become today an important research direction.According to different criteria Ad Hoc network routing protocols can be divided into different categories. According different ways of establishing a route, it can be divided into table-driven routing protocols, on-demand routing protocols and hybrid routing protocols. Among these protocols, on-demand routing protocols neither need to save the information of the other nodes in the network, nor need to periodically broadcast routing information to the other nodes, it can save a lot of network overhead, and it is the direction of Ad Hoc network route. AODV is a typical representative of n-demand routing protocols, so is the focus of research.This paper first introduces the background and the research status in the field and introduces the key technology, system structure and application situation of Ad Hoc network. Then it discusses the classification of routes applied on it, analysis the operation process of AODV routing protocol in detail, and summarizes the research status in the route discovery and route maintenance. On the basis above, we improve route discovery and maintenance respectively, propose SD_AODV(Shrink-Dynamically AODV),the main contributions are as follows:1: Considering the AODV routing protocol in the routing found phase is only simply choose path of the shortest hop to transmit data, it doesn’t take the load of the node into account, This can lead to network congestion, causing some of the network "center" node to early death due to excessive use. We choose nodes according their load to avoid choose path in high load, so it can achieve load balance, prolong network life and Reduce transmission delay.2: Considering nodes in Ad Hoc net work are in high-speed movements, and with the movement of the node, an optimal path may appear and route selected before is no longer a best one. But AODV will ignore the optimal path, once a path is selected, it will use the path until it break,this has seriously affected the performance of AODV protocol. To address this situation, the improved protocol changes dynamically according to network topology to search a best route between source and destination, reduce the negative influence of dynamic change of network topology. Results obtained through simulations demonstrate that the improved protocol is better than AODV in reducing network congestion and packet loss rate.