Research On Routing Algorithm For Mobile Ad Hoc Networks

The fast development and advancement in wireless communication and computernetworks technologies lays a foundation for mobile wireless communication networks.Mobile ad hoc networks (MANET) is born from the situation and becoming the mainresearch interest in mobile networks. Without the support of fixed infrastructures,mobile ad hoc networks can provide a communication platform if the existingnetworking infrastructure can't be used or there is not networking infrastructure at all.So it expands the using of mobile communication networks and it can be widely usedin tactical communication, emergency search-and-rescue operations, meeting andconversations. And it's an important component of the next generation networks.Routing is used to search routes for data packets and transmit them todestinations and is a key technology for mobile ad hoc networks. As the keycomponents of routing technology, routing algorithms and protocols have direct effecton network performances such as ETE delay, throughput and delivery rate. There is nostationary infrastructure such as base station in mobile ad hoc networks. Each nodeacts not only as a host, but also as a router to forward data packets for other nodes. Itis a central and pivotal problem to assign the wireless resource effectively amongwireless nodes and construct stable and effective routing from sources anddestinations in mobile ad hoc networks.These special characteristics such as distributed, multi-hop, self-organizing,dynamic topology, time-variant channels, and limited resources etc make thetraditional routing algorithms and protocols for wired networks and centered wirelessnetworks can't be used in mobile ad hoc networks directly. So the appropriativerouting algorithms and protocols for mobile ad hoc networks must be designed, andthese special characteristics make it become a challenging task.In the paper we analyze the routing technology of mobile ad hoc networks, whichcan be classified into two categories: topology based and position based. And ourresearch focuses on the following aspects: position based beaconless routingalgorithm, performance comparison of position based and topology based routing,position based and topology based hybrid routing algorithm and routing maintenancealgorithm of DSR by using position information. The main achievements are listedas follows:1. The position based routing algorithm can be classified into two types: beacon orbeaconless routing algorithm, which depends on whether it needs the positioninformation of the neighbors' node to make the routing decision. The positionbased beaconless routing algorithm doesn't need the periodical beacon to maintainthe position information, and it makes its routing decision by the current nodeaccording to its location relative to the previous sending node and the destination.So it expends less wireless resource. The existing position based greedy routingalgorithms only consider one of the metrics: the progress or direction. We define anew metric which combines the traditional progress and direction, resulting in therouting has better performance in both traditional progress and direction. And wepropose an improved progress position based beaconless routing algorithm(I_PBBLR) by combining the new progress with beaconless greedy forwardingstrategy.2. Based on the detailed analysis of topology based routing algorithm, especially ofthe dynamic source routing (DSR), we model and simulate DSR by OPNET. Andwe compare DSR's performance with the improved progress position basedbeaconless routing (I_PBBLR) by simulations.3. The topology based routing algorithms depend on the link information todetermine routing, and they must maintain the being used routing at least. Positionbased routing need neither construct nor maintain routing, but they must get theposition of destination first. We propose a position and topology based hybridrouting algorithm for MANET. The simulations show the proposed hybrid routingalgorithm improved the performance of routing.4. Flooding is always used to construct routing in DSR. When the being used routingfailed, flooding is used again to maintain routing if there is no other routing in itsrouting cache. The often used flooding increases the overhead of routingmaintenance with the increment of nodes' mobility. We improve the routingmaintenance algorithm of DSR by using the position based beaconless routingalgorithm, propose a position based routing maintenance algorithm for DSR,which decreases the number of flooding dramatically in DSR. This improvementnot only enhances the performance of DSR, but also makes DSR more suitable forthe dynamic ad hoc networks in which the nodes move fast.