| Ad hoc networks are a multi-hop temporary, decentralized, self-organized, distributed network system that consists of a number of wireless mobile terminals, which do not need to rely on fixed facilities. In Ad Hoc networks, frequent random movement of nodes will lead to change of network topology at any time and the network topology will be difficult to predict. Therefore, routing protocol is one of the important and difficult areas in research of ad hoc networks.Nowadays, reactive routing protocols are widely used in mobile ad hoc networks. Reactive routing protocols, such as DSR and AODV, select the shortest routing path as the route. In light load networks, their performance is good. However, when it comes to the high volume of data transferring, the performance deteriorates. Part of reason is because of their preference choosing the nodes that are in the center region of network as the intermediate nodes, incurring a large number of data transmitted through those nodes. When processing ability and bandwidth of all nodes are the same, those nodes that are in the center region of network may be the network bottlenecks, which would lead to the greater congestion, delay and performance degradation. In this case, the load balancing technology can effectively balance the load within the network, and improve network performance. Therefore, the load balancing should be considered in the design of routing protocol in wireless ad hoc networks, and the networks can maintain a continuous, efficient and stable operation.In this thesis, we firstly make a survey of the recent research status about load balancing routing protocols of ad hoc networks. And we analyze and compare these different load balancing routing protocols. Then we present a load balancing routing protocol that is improved based on DSR protocol. In this protocol, we introduce the concept of dynamic threshold, and this threshold reflects the network load timely. In the route discovery process, each node will compare its own load and the dynamic threshold to determine whether it is the heavy load node, and forwards selectively RREQs. This protocol prohibits the intermediate nodes from sending back route replies, in order to ensure that it is always using the latest load information in process of selection routing. Meanwhile, the destination node chooses an optimal route, which is based on the network load information recorded in the RREQs.The simulation shows that the proposed protocol could make the network load more evenly, reduce end to end delay, improve the success rate of packet transmission and have better throughput, which is compared with DSR protocol. |
