Scan Of A Triangle-based Mobile Ad Hoc Networks Broadcast Protocol To Achieve

An ad-hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any established infrastructure or centralized administration. Such a network can function in absence of fixed routing infrastructures, e.g. base stations. When the wireline network is not available, as in battlefield communications and emergency search-and-rescue operations, mobile ad hoc networks provide a feasible means for ground communications and information access.Since all communicating nodes can move with unlimited mobility, the topology of a mobile ad hoc network can change frequently. Traditional routing techniques are designed with implicit assumption of a comparatively stable network topology, and their performance grade in mobile environment is bad. New routing techniques are demanded for the special mobile network, and it is a challenge for the researchers in this area. Generally, the problem of routing can be divided into three basic parts: unicast, broadcast and multicast. In this paper, broadcast routing is studied with flat structure.Broadcast is an important operation in mobile ad hoc network. It is not only an important communication ways in many mobile ad hoc network applications, but also the basic methods for route discovery in unicast and multicast routing protocols. Meanwhile, in many applications especially for battlefield and emergency communications, the size and density of the mobile ad hoc network is large. So we propose a Radar-Scan based on Trigonometry (RaST) algorithm to solve the problem broadcasting in a high density mobile ad hoc network.In the RaST broadcasting algorithm, when a node start a broadcast procedure, it counts the number of its neighbors firstly. If the number is smaller than the threshold value N, the node asks all its neighbors to rebroadcast the message;otherwise, it start the RaST mechanism by scanning all its neighbors to find the critical nodes, then adds the critical nodes found to the head of broadcast packet and sends it.When a node A receives a broadcast packet from its neighbor, it firstly judgewhether the packet is reduplicate. If not, Node A sends the packet to the upper level of the network;otherwise, abandon it. Then, if the sender uses the RaST mechanism, node A judge whether it is included in the critical node list of the sender. If not, node A abandons the packet;otherwise, it selects its critical nodes in a "certain" area, empties the former critical node list, adds the critical nodes found to the list in the head of the packet and rebroadcasts the packet.In order to evaluate the performance of the RaST algorithm, we implemented it in the NS2 platform, and select the broadcast operation in AODV as the comparing object. We set up a network scene whose area is 1000m* 1000m, and evaluate the RaST algorithm under four different node density and four different node movement. The experiment result shows that the RaST algorithm has good performance compared with AODV, and is stable in different environment.Besides, we implemented a mobile instant messenger system: MobiMessenger based on AODV protocols. The RaST algorithm can be add as a module to the system and develop an instant messenger system which can work in a high density network.Mobile ad hoc networks have been developed under the driving of the potential military and commercial application requirements. There are many problems that have not been resolved perfectly. Many research efforts should be made for the coming of a practical mobile ad hoc network.