Study On The Detection Of Misbehavior In Wireless Mobile Ad Hoc Networks

The wireless mobile Ad Hoc networks is a distributied, instant self- organized autonomous and multi-hop system of a muster of wireless mobile nodes that are capable of communicating with each other over wireless links, which is a wireless system without a fixed infrastructure. The chief difference between the wireless moblie Ad Hoc networks and conventional cellular technology is the apparent lack of a centralized entity within an Ad Hoc networks. There are no base stations or mobile switching centers in an Ad Hoc networks. Recently, the wireless mobile Ad Hoc networks become the hot spot of communication domain due to its flexible, convenient mobility support.But the completely distributional characteristic in the wireless mobile Ad Hoc networks proposes a series of complex challenges for the network security design. Some nodes inevitably execute misbehavior, by violating the network protocol for their own benefit to gain the more network resource. In the wireless mobile Ad Hoc networks, how to use the limited wireless channel fairly and reasonably becomes an important topic. Because the lack of cooperation algorithm and the central infrastructure, which cause the fixed network mechanism to be unable to apply in the wireless mobile Ad Hoc networks, therefore in this thesis we propose two solutions in view of the misbehavior to some existing works.Firstly, the misbehaviors exist in the the DCF mechanism of IEEE 802.11 protocol, the misbehaving node may wait for smaller backoff intervals than well-behaved node,so it can occupancy the channel for a long time to transmit the data, that causes the others can't transmit. So it is necessary to detect and handle such misbehavior promptly and effectively. In the wireless mobile Ad Hoc network, through establishing the observation node, gathering the neighbor node's behavior information, we take these informations as the sampleing value, and utilize the signal sequence detection to detect such misbehavior. The simulation results indicate that with the appropriate parameters, the method in this paper can not only reliably and timely detect the misbehavior, but also minimize the average number of required observations.Secondly, we present modifications to the DCF mechanism of IEEE 802.11 protocol, instead of the sender selecting random backoff values to initialize the backoff counter, the receiver selects it and sends it to the sender in the CTS or ACK. The EIED (Exponential Increase Exponential Decrease) backoff algorithm is utilized to vary the contend window. Modifications to the DCF mechanism are used to detect the misbehavior. The penalty measures are taken further to correct the misbehavior. Simulation results indicate that the ratio of correctly detecting the misbehavior is improved and the throughput of the whole networks is increased with the proposed mechanism.