A Routes Maintaining Method For Decreasing The Flooding Congestion In Ad Hoc Network

In an Ad hoc network, to find a route always requires a global flooding of request packets. Because of the mobility of the nodes, the route discovery is carried out frequently. This flooding-based route discovery produces so much request packets which congest the network, we define this congestion as flooding congestion. Flooding congestion will affect the capacity of the network, so how to decrease the flooding congestion has become a hot field in the research of Ad hoc network.The work presented in this dissertation is part of the National Natural Science Foundation project-Swarm Intelligence. This project aims to explore a new parallel computing pattern in accordance with the large scale swarm cooperation,and try to run the algorithm in our hardware platform to simulate the swarm behavior. The individual nodes of the network are constituted by e-mouse(electrical mouse) developed by our laboratory. E-mouse has basic capacities such as moving forward, moving backward, IR-aided obstacle avoidance and receiving and sending data packets. A network consisted by these e-mice has the distinct characters such as high mobility, complete self-configuring, a limited bandwidth. Owing to these characters, a swarm intelligence network is a typical Ad hoc network. And the main purpose of this dissertation is to explore an efficient way to decrease the flooding congestion in such a network.The traditional way to decrease the flooding congestion is LAR mechanism. LAR assumes that source node knows the location and velocity information of the destination node, then it computes a limited flooding area to the destination by these information. In this way the amount of request packets is decreased significantly. But the precondition of LAR makes it not so applicable, so in this dissertation we propose a new flooding congestion decreased algorithm BLA-RM (Broken Location Aided Routes Maintaining). Compared with LAR, BLA-RM has the advantages as followed:1. In BLA-RM,source node computes the flooding area by the location information of the broken node and floods the request packets in such a limited area, while the location information can be delivered by the route error packet which is an existed carrier in the network, so get rid of the precondition of LAR.2. The flooding area computing formula of BLA-RM considers the different position the broken node locates in the whole route and the twisted extent of the route.3. BLA-RM also introduces the conceptions of noDrop_area and semiDrop_area, enhancing the robust of our algorithm. Finally, we conduct the simulation experiment for BLA-RM by NS2-a network simulator from UC Berkeley. Simulation method is adding BLA-RM to the existing mature Ad hoc routing protocols (AODV, DSR). Simulation results show the significant capacity of our algorithm in decreasing the flooding congestion. Also, the average end-to-end delay capacity is improved.