Study And Improvement Of AODV Protocol Based On NS2

As a wireless communication network, Mobile Ad Hoc network(MANET) is composed of some freely-moving nodes and has the feature of no central base station. Its random topological structure and limited nodes energy makes the design of a high-quality route protocol the key to solve the problem. AODV protocol, a classical on-demand routing protocol for Ad Hoc network, can find a effective route quickly. But the disconnection of the found link may extremely affect the performance of the network. Thus, it is quite significant and valuable to study the AODV protocol. Firstly, the background and development of Ad Hoc routing protocols were introduced. Secondly, main types of Ad Hoc routing protocols were shown, and parameters and performance of different routing protocols were compared. Then frame format and working mechanism of AODV were carried out detailly. Finally, two improvement program were proposed as follows to improve the performance of classical AODV.In the first scenario, because the traditional AODV protocol has only one communication link, when the communication link breaks down, another route discovery which would seriously affect the performance of the network are necessary. This paper presents a smart choice of backup route AODV(Smart Selection of Primary and Backup for Ad Hoc On-Demand Distance Vector Routing, SSPB-AODV), by adding a backup route and analyzing the historical data to make a smart choice: For the main route, when an interrupt occurs, it will decide whether to repair local route or switch to a backup route based on historical data; and for a backup route, the selection will be based on historical data to choose whether to repair or re-initiate a route discovery process. The results of simulation by NS2 show that SSPB-AODV can improve the networks performances effectively, especially the packet delivery fraction, normalized routing overhead, route discovery frequency and end-to-end delay.In the second program, because the bandwidth and the energy of nodes in the network are very limited, it is essential to consider the congestion control and energy balance in the process of designing routing protocols. A new protocol that measures the energy and load by hop cost, called EL-AODV(Measure Energy and Load Based on Hop Cost, EL-AODV), is proposed in Ad Hoc network. The protocol combines the number of hops in the link withnew hops conversed from remaining energy and link load to choose the path with smallest total number of hops as the communication link. In this way, we can improve the performance of the network so that a new route wouldn’t be established among the congestion and less residual energy nodes. According to the simulation results obtained by NS2, it is showed that the EL-AODV performs effectively in terms of packet delivery fraction, normalized routing overhead, end-to-end delay and nodes residual energy.