The Research Of On-demand Routing Protocols In Mobile Ad Hoc Networks

Mobile ad hoc network is a wireless mobile network, which works in an environment without a fixed framework. It has some characteristics being different from the general network, such as no center, self-organization, multi-hop routing, dynamic network topology and so on. In recent years, mobile ad hoc network has been widely applied to many fields, including emergency disaster relief, military battlefield, sensor networks and traffic. With the development of mobile ad hoc network, many imperfect aspects also come to light. Because of issues of routing, energy conservation, safety, quality of service and so on, the mobile ad hoc network face significant technical challenges. This paper studies on-demand routing protocol in mobile ad hoc network, proposes an improved routing algorithm and evaluates the effectiveness of this algorithm by OPNET simulation.Firstly, the paper summarizes the recent on-demand routing protocols having been proposed, introduces some important protocols and compares their performance. Then, this paper analyzes the problem of redundant route request message for AODV (Ad hoc on-demand distance vector) routing protocol, and introduces a improved LAR-based AODV routing protocol. LAR-based AODV introduce the mechanism that makes use of the destination node location information to limit the routing search to a particular region in LAR (Location-Aided Routing) into AODV. To a certain extent, this mechanism reduces the some redundant route request messages. To further reduce unnecessary redundancy route request messages, this paper improves the LAR-based AODV route search process to re-calculate the forwarding angle by intermediate nodes to reduce the surplus route request messages. Besides, the improved route search process ensures that number of neighbor nodes in forwarding angle is not less than the threshold M, which is useful to reduce the probability of route search failure. In Addition, the improved mechanism adds the location-based counter method into route search process. This method sets the timer by node position information, rather than random, thereby giving the intermediate nodes closer by destination node priority to forward route request message. Combination of these improvements, this paper proposes Geography-based AODV routing protocol. Finally, in the OPNET network simulation platform, this paper achieves the LAR-based AODV and the Geography-based AODV routing protocol proposed by this paper by adding and modifying its own AODV routing protocol. The simulation results shows that Geography-based AODV in the data delivery ratio, routing overhead, the total packet dropped, end to end delay and the average route hops is better than AODV and LAR-based AODV.