Research On Fault Tolerant Technologies In Wireless Sensor Networks Based On Trust Management

Wireless Sensor Network (WSN) is a network system which is composed by a large number of miniature and low-cost intelligent sensor nodes deployed in monitoring area by using wireless communication channel through multi-hop self-organizing mode.The hardware structure of the sensor nodes is simple and has finite energy. Because the sensor nodes are usually deployed in rugged and unattended environments and the wireless channel itself is not reliable, all these lead to the frequent breakdowns of the network such as communication link disconnection, nodes damage or energy exhaustion, which brings that the data collected by the sensor network can not reflect the real situation of the area in which the events have occurred. Meanwhile, the network may be attacked by malicious nodes or the problems of the software of the sensor nodes may lead to collected data errors. To the data-centric wireless sensor networks, it is very necessary to carry on research on fault tolerance and reliability of the network.Due to the lack of trust management mechanism of WSN, this thesis proposes a trust management mechanism based on a kind of the credibility of the nodes. The core idea of this mechanism is to take into account the data collected by sensor nodes not only correlated on the node itself but also with other sensor nodes data within the field, by obtaining the data confidence level according to the similarity matrix, to calculate the available correspondence bandwidth and the excess energy and obtain the bandwidth and energy credit. Then the trust model is built by the credibility of the data, bandwidth and energy of the sensor nodes in wireless sensor network and the model is introduced to the management system, all the behaviors of the network building and the nodes are based on the credibility.Subsequently, the trust management system is introduced to the event detection of the sensor nodes and an algorithm of NCFTED (Nodes Credit Fault-Tolerant Event Detection) is proposed. The main idea of this algorithm is that when the sensors detect abnormal data, the failed nodes are excluded according to FNE (Fault Nodes Exclude) and the cluster heads established under a trust environment, are selected by taking advantages of the trust rank of the nodes in this field. By analyzing, A multi-hop mode can save more energy than that of single-hop. Specially for the nodes of the cluster head or the ones far from them, The multi-hop mode should be adopted as far as possible to communicate between inside and outside of the clusters and transmit the data to the base stations.In this thesis, the prospect and significance of this research was firstly narrated and the promising applications together with the problems of current wireless sensor network were analyzed. It also simply described the application prospect of wireless sensor network in detail and the current research status of trust management mechanism with fault-tolerant technology both at home and abroad, and the structure and basic features of current wireless sensor networks. The trust evaluation model of the nodes was obtained by calculating the credibility of them and it was introduced into the fault-tolerant detection technology.Secondly, this thesis emulated the algorithm NCFTED, which can detect abnormal data by collecting the sensor data of the neighboring nodes only for one time and exclude the failed nodes by simple calculation though NS2 network emulation platform. The emulation had figured out that the algorithm had a high rate of identification, low rate of false detection and alarm, low computational complexity and high fitting degree. Because the establishment of the clusters can only be conducted when the abnormal data is detected, the communication traffic of the network is very little and the clusters have the best expansibility in the large-scale networks.