Research On Self-organized Routing Algorithm For Large-scale Wireless Ad Hoc Networks

Mobile Ad Hoc Network(MANET) is consisted of a group of wireless mobile nodes. It is a network system that doesn’t rely on fixed communication infrastructure, and can be quickly deployed at various situations. MANET is usually a self-organizing peer-to-peer network which has no centeral control point. Nodes in the network are homogeneous. Each node is not only a mobile terminal which just sends or receives packets, but also acts as a router that forwards packets. So the network has strong survivability. Furthermore, nodes can join or leave the network dynamically. Nowadays, MANET has been widely used in military and civilian areas such as disaster relief, and plays an increasingly important role in commercial areas.In this paper, our aim is to design an efficient routing protocol for large scale Ad Hoc Networks. Generally, Ad Hoc network has high mobility with frequent topology changes. So a scalable routing protocol has to efficiently reduce the total routing overhead without sacrificing routing functions.Therefore, we focus upon the network layer, and propose a virtual backbone-based Hazy Sighted Link State(VB-HSLS) routing algorithm. It is a kind of proactive routing algorithm, which adjusts the frequency of control message transmission based on the distance between sources and destinations. So it cares more about the topology changes close to the node itself, which enhances the adaptability of the network changes. Especially, such method significantly reduces the routing overhead. The backbone election and maintainance algorithm is based on the connectivity of nodes, and is used to limit the forwarding of routing control messages within the subnet of backbones. It further reduces control overhead with mininal influence upon routing functions. The proposed algorithm not only improves the efficiency of the protocol, and avoids the redundant forwarding, but also maks the protocol more suitable for large-scale mobile Ad Hoc networks.In order to verify the performance of the proposed protocol, it is implemented and analysed via OPNET network simulator. Firstly, we implement the protocol on OPNET, and design a variety of simulation scenarios. Then, by modifying the node model and the format of HELLO packet, as well as adding virtual backbone table, a subnet of connected virtual backbones is elected from the network. After that, the forwarding method for control message is improved, which effifiently combines the HSLS algorithm and virtual backbone based forwarding approach. In the end of this paper, simulation results are collected and analysed. By comparing the performances of DLS, HSLS and VB-HSLS protocol under different network density and mobility, it is demonstrated that the proposed protocol is more efficient and suitable for large-scale mobile Ad Hoc networks.