Research On Technologies Of Node Localization And Coverage Control For Wireless Sensor Network

Wireless sensor network (WSN) has the feature of low-cost, strong fault tolerance, rapid deployment, no fixed network support, and the capability of taking long-term monitoring tasks, so, WSN has broad application prospects in the fields of environmental monitoring, health care, military commercial sectors and etc. As a new technology, WSN raised many challenging research topics for researchers, and among the topics, the research on node localization and coverage problem are of great significance for the basic theory and the supporting technologies of WSN.In this thesis, we introduce the basic principles of node location and coverage control technology of WSN systematically, and discuss the node location and coverage control algorithms in-depth. Considering the problem to be solves urgently of node location and coverage control in monitoring WSN, we propose a precise, flexible node localization mechanism, as well as the energy-saving, efficient coverage control algorithms, which include centralized and distributed computing methods.In order to provide location information for monitoring WSN, the node need to be positioning flexible and efficiently after deployed. As the reflective, non-line and other factors, the localization error is greater in traditional positioning methods using RSSI ranging. Taking into account the above problem, a localization method with ring overlapping based on received signal strength indicator (ROBRSSI) is proposed for monitoring WSN. ROBRSSI make full use of the collaboration between nodes to design the algorithm, through which the requirement of the relative position between node and beacons is reduced, and combined with the idea of ring overlapping, ROBRSSI designs error transforming model, positioning refinement and positioning verification process, which restrained the effect of measurement error of RSSI on localization accuracy in traditional localization algorithms efficiently. Due to continuous working or attacks, some nodes will fail, and there need to add new comers in WSN and get the location information of the new comers timely. Considering the demand above, a localization approach for the new comer based on ROBRSSI is proposed. Simulation results show that the location accuracy and the localization percentage are better than traditional methods, and the localization method of new comer is efficient, which achieves precise localization.For the network with high density nodes, considering the energy issue, a dynamic coverage control strategy based on genetic optimization is proposed. In the proposed strategy, we design the mechanism of density detection to optimize the initial population and improve the quality of the population. In addition, we introduce the idea of taboo and designed two taboo operations to achieve the effective local search and improve the ability of global optimization. On the basis above, we design the rotation of coverage sets of nodes triggered by energy, which can balance the energy consumption and prolong the lifetime of network further. Through the designs, the optimization coverage sets of nodes with fewer nodes and higher coverage and balanced energy consumption are achieved by our strategy quickly; the energy consumption is reduced, and at the same time, the energy consumption is balanced, and the lifetime of network is prolonged effectively. Simulation results show that the proposed strategy can achieve better performance at early iteration.Due to the imbalance of the node’s energy consumption the sensing radius of node has some difference between each other, which will affect the performance of redundancy detection algorithm. In view of this complex application environment, a redundancy detection algorithm is proposed, which is coverage-preserving and satisfies K-coverage condition. At first, according to the redundancy distribution characteristic of the node in WSN, the algorithm designs effective neighbor selection, which reduces the computing time greatly. Furthermore, considering the boundary effects, the detection criteria under binary sensing model is proposed, and considering the sensing distance attenuation, the detection criteria under probability sensing model is proposed further, and the reasonableness of the criteria proposed is analyzed. In the complex environment under binary sensing model, when the nodes have the same sensing radius, the algorithm activates fewer nodes for working and the redundancy detection is thorough; when the nodes have different sensing radius, the algorithm detects the redundant node adequately and efficiently still; the performance of the algorithm under probability sensing model is stable, and it is easier and more accurate compared with grid-based method. Simulation results show that, compared with typical algorithms, the redundancy detection algorithm is more efficient and applicable, and the redundancy detection is more thorough. In the global periodic wake-up redundancy node scheduling schemes, a lot of energy consumption made by control information exchange and radio-frequency transceiver wakening is unnecessary. Furthermore, if a node dies between two rounds of the scheduling, events occurring within the sensing field of it will not be detected by other nodes until the next round begins, which affects the quality of coverage. Considering the problems above, the energy triggered coverage-preserving node scheduling scheme (ETCPS) is proposed. ETCPS mainly includes initial scheduling phase and local wake-up scheduling phase, after initial scheduling, the node whose energy reaches the threshold generates trigger event and updates the threshold, and the nodes relevant to the event are woke up to go into wake-up scheduling for adjustment. The scheme proposed guarantees a better coverage quality, and at the same time, it balances the network energy consumption. Simulation results show that the scheme proposed guarantees a better coverage quality and extends the lifetime of the network effectively.