Research On A Location-Based Routing Protocol E-LAR In Mobile Ad Hoc Networks

An Ad Hoc network is a self-orgnaizing wireless network without relying on immobile infrastructure. The construction of such network is easy and convenient, and is not limited by time and space. The topology of ad hoc network may change frequently due to the movement of the nodes. Therefore, traditional routing protocols are not suitable for ad hoc network, and research of routing protocols in such network has become a core problem. In recent years, routing protocol based on geographical position in mobile Ad Hoc networks has developed rapidly in virtue of its independent routing option, flooding avoidance, well scalability and adaptability.This thesis first introduces the background of the routing protocol based on geographical location for mobile Ad Hoc networks and then compares existing routing protocols in feature and performance. This thesis engages in intensive study on a typical routing protocol based on geographical position—Location Aided Routing (LAR) and put forward an Improved Location Aided Routing (I-LAR) in allusion to the inefficiency of LAR. I-LAR protocol takes the link expiration time into account when chosing the forwarding node, thus effectively improves the stability of the established path, lowers the packet loss rate of data transimission, and increased the quality of service for the network. Furthermore, I-LAR calculates the effective transmission distance by counting the information of completed transmission, and then adopts the "N+TTL" local flooding strategy which based on the distance between the source and the destination to further reduce the the control overhead.As there is no effective strategy to update the position information in I-LAR, so the data in the position table may easily become invalid. Then the flooding scheme is used instead which increases the control overhead. An Extended Location Aided Routing (E-LAR) based on ILAR is proposed to solve this problem. E-LAR protocol finds the location of the destination by using the mechanism of asking the way, and introduces location update strategy to locate the destination faster and more accurate, which reduces the control overhead effectively. This thesis uses the OMNET++ network simulation software to build a model for the routing protocol pre and post respectively, in which packet delivery ratio, control packet overhead and end-to-end delay are selected as the main evaluation parameters. Simulation result shows that compared with LAR, the improved protocols can increase the packet delivery ratio and reduce the control packet overhead notably.