Routing Algorithms For Flapping Inhibition In Ad Hoc Network

As a new type of wireless communication, Ad hoc network gains much attention for its flexibility. Since self-organized with no center, its routing protocol is one of the key technologies which affect the network performance. Because of nodes'random movements, the topology changes all the time, unforeknowable. Route flapping means the frequent establishment and revocation of routes, and it would result in large delay or interrupt during communication, and deteriorate the quality of service. Moreover, mobile Ad hoc network is often built up by energy-limited terminals. If we use one route (maybe the best one under some condition) for too long, the nodes on it would be consumed much earlier than the others, which weakens the connectivity of the network. If the battery is low, the node's coverage may also change, and affect the link's stability. According to these disadvantages, this paper gives out some solutions.Firstly, this paper puts forward a recursive backup multi-route protocol AODV-SRM, reducing the delay when the communication route fails. AODV-SRM gets all independent routes between the source and the destination, and maintains them periodically. First, the source maintains routes. If it has only one route, a recursion method is used to find out a node with multi routes to the destination, and this node will start the maintenance. The route maintenance will not stop until the communication finishes. When the communication route fails, the node with multi routes will select a backup one instead of route re-discovery or local repair. This reduces communication delay and weakens the impact of route flapping.Secondly, aiming at the stability of links, this paper proposes a two-way routing protocol AODV-NS based on neighbor stability. Each node calculates its neighbors'lifetimes and the counts of route failure, and sets the combination of the two parameters as the weight of links. Unlike traditional single-way routing protocols, AODV-NS selects both upstream neighbor and downstream one according to the link stability, which makes the route more reliable. The shortcoming of AODV-NS is the reduction of independent route amount. The two-way routing protocol based on neighbor stability can inhibit route flapping better in dense scenes than in sparse ones.Thirdly, to reduce the packet loss caused by route flapping or collision, this paper gives out a multi-node cooperative routing protocol based on cross layer– AODV-CLC. Each node obtains the signal strength of its neighbors, and judges whether to join a cooperation group according to the signal strength. A cooperation group is set up by several handshakes. Traditional cooperative protocols only provide data cooperation, but AODV-CLC provides ACK cooperation besides, and reduces the source's unnecessary retransmission. To avoid congestion, one cooperator assists one cooperation source. To avoid collision during retransmission, one cooperation source selects only one cooperator. AODV-CLC ensures the transmission reliability at the cost of more control messages.Fourthly, considering the limited energy in mobile Ad hoc network, this paper describes a two-way routing protocol AODV-TEB, with a non-linear weight by the energy consumption ratio and the residual energy. When the energy is high, the weight mainly depends on the traffic load (the energy consumption ratio). On one hand, we avoid consuming key nodes too much. On the other hand, we avoid competing for hot nodes with other users which may cause collision. When the energy is low, the weight mainly depends on the node's residual energy. We try not to use nodes with low-battery, in case that the network is cut into small ones if bridge nodes run out of battery, thus prolong the network's lifetime.AODV-NS and AODV-TEB are two kinds of routing protocols. The former focuses on the route's stability, while the latter mainly considers the network's lifetime. The two routing mechanisms are chosen according to practical environment. They can be used separately or mixed. They are both compatible with AODV-SRM and AODV-CLC, and can be used in combination.