Research On Routing Protocols And Fault-Tolerant Event Boundary Detection Of Wireless Sensor Networks

Wireless sensor networks (WSNs) consist of a large number of small cheap tiny-sized sensor nodes that possess self-organizing capabilities and are densely deployed in the environment. The primary mission of wireless sensor network is to detect the events occurring in the range of sensor networks and then to report them to network users. It is not only a single network technique, but also a coordination science which includes sensor techniques, embedded computation techniques, distributed computation techniques and wireless communication techniques. WSNs change the people's interactive mode with nature and promise many new application areas, such as military applications, environmental monitoring, space exploration, disaster rescue, medical health, intelligent home, precision agriculture, building state monitoring, seismic monitoring and other commercial applications.Routing protocol is vital and also fundamental in WSNs'research and applications, and has great influence on performance of the networks. Characteristics of sensor nodes, such as large-scaled and dense deployment, constraints on power, communicating ability, computing ability, memory ability, and unattended infertile circumstance, bring great challenges to routing protocols. Moreover because of the application backgrounds of wireless sensor networks differ significantly, designing universal routing protocol is too complicated and is not conducive to saving energy and reducing complexity, and thus the design of wireless sensor network routing protocols needs to be closely related to the application backgrounds. Event Detection is an important application of WSNs. In order to increase the detection accuracy,false-tolerant techniques need be adopted. This dissertation addresses the wireless sensor network routing protocols and false-tolerant event boundary detection. The main contributions are outlined as follows:(1) Some representative routing protocols are introduced and analyzed along two lines: the flat routing protocols and the cluster-based routing protocols. Moreover, the basic principle and some typical algorithms about fault-tolerant event detection are summarized.(2) In most cluster-based routing protocols, each cluster members communicate only with cluster heads directly, that bring not only high and uneven energy consumption to cluster members, but also high work burden to cluster heads. Aiming at this problem, a cluster restructuring scheme (CRS) and delay adaptive data transmission protocol (DADTP) applicable to most cluster-based hierarchical network architectures is presented. Only if all cluster members are within one-hop communication range of their cluster heads, the CRS and DADTP are applicable. Furthermore, no position information of any sensor node is needed. Simulation results show that, the CRS and DADTP can alleviate the work burden of cluster heads greatly and lighten the energy consumption of both cluster heads and cluster members, which is great significance to stable performance of network and prolongation of the network lifetime.(3) In position-based routing protocols, GPS or a great deal of information exchange is necessary, which bring high cost or high energy consumption. Aiming at this problem, a station-aided organization algorithm and data transmission protocol (SOADTP) is presented, in which no position information of any sensor node is needed. By receiving the control message transmitted by the base station equipped directional antenna, the sensor node completed localization and clustering. According to their residual energy and the intensity of the signal they have received, which can reduce the communication cost between sensor nodes. Moreover, SOADTP designed two methods for localized rotation of cluster heads and the management of dead nodes. The simulation results under different scenes testified the validity of SOADTP. When CRS is adopted, the network performance will be farther improved.(4) Event Detection is an important application of wireless sensor networks. Aiming at the problem that faulty sensors decrease the accuracy of event detection, a novel distributed algorithm for fault-tolerant event boundary detection and report is advised. Only the sensors with abnormal readings need identify whether they are faulty through collecting the actual readings one time from their one-hop neighbors. Then normal event sensors detect whether they are boundary sensors by simple comparison. The width of the event boundary can be adjusted according to network users'requirements. At last, the boundary sensors are organized into clusters and the cluster heads route the boundary information to the base station through the gradient paths respectively. This program is of high detection accuracy, high degree of fitting, low false alarm rate, low false detection rate, low communication traffic, low computation complexity, low time-delay,and scales well to large sensor networks.