Research On Key Techniques Of Mobile Ad Hoc Network

Mobile Ad Hoc Network (MANET) is a self-organizing and self-configuring multi-hop wireless network without predefined infrastructure, where the network topologies, traffic model and channel environment dynamically change with node mobility. It can establish instant communication infrastructures for civilian and military applications.Despite the long history of ad hoc networking, there are still quite a number of problems that are open. Such as Multiple Access Control (MAC), Routing protocols, Power management, and so on. In this paper, the MAC techniques, routing algorithm, and the flooding broadcast algorithm are discussed. The main research works and results are listed as follows.1. A new analysis model is proposed to research the saturation throughput and access delay of IEEE802.il protocol under Distribution Coordination Function. This model is simple but very accurate. Another analysis model is designed to analyze the optimal transmission buffer capacity of the IEEE802.11 protocol. The concept "Equivalent Service Time" is used to describe our model and then the system can obtain the good performance without loss of any store resources.2. A novel MAC protocol for Ad Hoc Network~FA_MACA (Flow Adaptive Multiple Access with Collision Avoidance) is presented. FA_MACA is an improvement of the well known MACA(Multiple Access Collision Avoidance) protocol, which not only avoids the "hidden terminal" problem in wireless channel, but also adaptively adjust the access delay based on the traffic flow and traffic priority of the network. Thus it decreases the collision and then improves the performance of the network. Simulation results show that FA_MACA outperforms several known multiple access protocols using traditional network access delay algorithms.3. Broadcast is an important operation in wireless ad hoc network. The simple broadcasting mechanism, known as flooding is easy to realize but can cause the broadcast storm problem. In this paper we present the Relative Degree Adaptive flooding Broadcast (RDAB) algorithm for Ad hoc networks to efficiently reduce the broadcast overheads in the network. Based on the current situation of the network and the degree of the nodes, RDAB calculates therelative degree of the nodes, decides which nodes need to relay and which nodes only need to receive. The higher the neighbor node's relative degree, the more uncovered nodes it can cover, so this kind of nodes can be selected to relay the broadcasting messages in the networks. Through the analysis of the reliability and the validity of RDAB algorithm, we can affirm that the RDAB algorithm is a valid flooding broadcast algorithm. Simulation results show that RDAB strategy outperforms the ordinary flooding broadcast method (OBM) for the Ad hoc networks.4. A novel routing protocol for ad hoc network-DSARP (Delay Sensitive Adaptive Routing Protocol) is presented in this paper. According to DSARP, the reliable route for delay sensitive traffic can be supplied and the route can be selected based on the constrained condition --"the Shortest route and the Lowest average delay". Therefore, the "hotspot" on the shortest path can be avoided. Meanwhile, the DSARP can assure to provide QoS guarantee and improve the performance of the network. Simulation results show that DSARP performs better than DSR routing protocol used in ad hoc wireless network.