Research On Localization And Energy-Efficient Technology Of Wireless Sensor Networks

Wireless sensor networks are made up of massive sensor nodes that communicate witheach other through wireless communication. Sensor nodes can monitor a lot of changes in thesurrounding environment, such as temperature, brightness, sound intensity, humidity, pressure,target size, target mobile, sensitive substances and so on. After being monitored and processed,these data are passed to the sink node, or the base station or the central node by wirelesscommunications, and then these data are delivered to the users for the follow-up operations.Spreading process is called the node deployment of sensor nodes, which includes the regulartype and the random type. After deployment, these nodes locate themselves firstly and carryon autonomic wireless connection in accordance with their physical locations and thereby awireless network is formed. Because of miniaturizating, integrating, and networking, thewireless sensor networks are developing into an important route of access to the information.With the development of society and people's requirements, wireless sensor networks aredeveloping from the military fields to civilian areas. Therefore, the aeroamphibiousequipments constantly develop and the applications of wireless sensor networks continue toexpand. The wireless sensor networks are extensively used for civilian areas, such asenvironmental monitoring, medical monitoring, traffic monitoring, security monitoring,production monitoring, agricultural monitoring, underwater monitoring, and space explorationand so on.Wireless sensor network is a network system that wireless sensor nodes are organizedthrough wireless communications. There are a lot of related disciplines, includingmicro-electro-mechanism system, wireless communication technology, the sensor technology,data processing and distribution technology, and after data monitoring, data collection, anddata processing, sensor nodes spread the information and form a network eventually. Wirelesssensor networks form the connections of the physical world, the information world and the human world, and become an important way by which human beings can access toinformation. For setting up the communication bridge between environmental informationand people, wireless sensor networks have a profound impact on the development of thesociety and human progress. Especially in rugged environment, or even hostile environmentthat people can't reach, the application of wireless sensor networks can guarantee the safety ofpeople.When wireless sensor networks have been deployed, node's localization is theprerequisite in the follow-up works. Aiming at the localization in wireless sensor network,three algorithms are proposed in this paper to promote the accuracy of node's localization.Because of limited energy in wireless sensor networks, an energy-efficiency correctionalgorithm is proposed in this paper to reduce energy consumption of the network and extendthe network's life cycle.VDCSHC localization algorithm is proposed in this paper to enhance the localizationaccuracy in wireless sensor networks. Two-dimensional coordinate system in monitored areais considered as one that can make virtual moves. The calculation of the estimated coordinateof beacon nodes is also involved in the process of localization, when Centroid algorithm orDV-Hop algorithm is used. There will be some differences between the calculated values andthe real values of the coordinates. A new coordinate system is set up by a vertical andhorizontal virtual movement respectively according to the size of the errors. The positions ofall the nodes in monitored area are unchanged in this process. Thus, the moved value of thenew coordinate system will counteract the error generated by the localization algorithm. Eachbeacon node is in a virtual coordinate system newly built up after moving, through the controlof the Hop range, and then the surrounding unknown nodes are selected. These unknownnodes will refer to the new virtual coordinate system built according to the beacon nodes andcalculate their location information. All these unknown nodes will refer to this beacon nodeon the new virtual coordinate system to calculate their locations. And the error generated byoriginal localization algorithm is counteracted, and then the accuracy of location algorithmcan be improved.From the analysis, the unknown node should use the virtual dynamic coordinate system which is based on the nearest beacon node. When the unknown node and the beacon nodechoose the other three beacon nodes in the same way by trilateration, the only parameter thatcould affect localization accuracy is the distance between the measured node and thereference node, and the parameter is determined by the product of two parameters which arethe hop distance of each node and the hop quantity between itself and reference node. It ishard to determine the value. The huge difference between the hop quantities of two nodes maybe compensated by the huge error of each hop's distance. Nevertheless, it is certain that theerrors of two nearest nodes are the most similar. This paper proposes VDCSHC algorithmwith the idea of hop quantity control, which suggests that when the unknown node choosesvirtual reference coordinate system, it must choose the virtual coordinate system informationsent by beacon node in one hop. If the unknown node can not find the beacon node in one hop,it should ask for the related virtual coordinate system from other unknown nodes in its onehop, and if it still can not find the information, it adds the hop control size until it gets thevirtual coordinate system information successfully. If there is no beacon node or unknownnode in one hop, this unknown node is a meaningless node, and the localization of this nodeshould be given up. The simulation experiments show that the algorithm can enhance thelocalization accuracy efficiently.A new localization algorithm which is based on optimizing beacon nodes assembly andray scan is proposed in this paper to enhance the localization accuracy in wireless sensornetworks. OAARS is for short. The idea is that we need to optimize the selection of beaconnodes which assists the localization of unknown nodes at first. This could be performed bycomparing the signal intensity or the time of signal arrival. Firstly, every beacon node sendsits location to the nearby beacon nodes. The beacon node receives the signal records, thelocation and the signal intensity or the time of signal arrival, in order to gain the relativedistances between other beacon nodes and itself. Beacon nodes don't transmit the message.The beacon node monitors whether its record of other beacon nodes exceeds a constant. If not,there is a lack of beacon nodes within one hop and the request will continue.Secondly, beacon nodes send their records to the nearby unknown nodes. The laterreceive the message and record signal intensity of the beacon nodes, based on which a beacon node is chosen as reference node. Based on the record of the reference beacon node, theunknown node chooses the beacon node with the weakest signal intensity among those whosesignal intensity between the reference beacon nodes is stronger than that between thereference beacon node and the chosen unknown node as well as the beacon node with thestrongest signal intensity among those whose signal intensity between the reference beaconnode is weaker than that between the reference beacon node and the chosen unknown node.We mark those three beacon nodes, and then we can find several similar beacon nodes asoptimized beacon nodes set. Simulating the radar, we draw a ray from the original point. Theray scans in the first quadrant of the monitored two-dimensional Euclidean space. Wecalculate the intersection points' sets of the ray and the arc formed by these beacon nodes. Theintersection points' sets are filtered through certain method and then we calculate centroid ofthe left intersection points as the estimated coordinates of the unknown node. Simulationexperiments show significant improvement in localization accuracy.A new localization algorithm based on the adrenaline control of Genetic Algorithm (GA)in wireless sensor networks is proposed in this paper to enhance the localization accuracy,GACAL is for short. GACAL algorithm uses the GA to locate the nodes, and designs thefitness generation in GA. In this paper, the fitness corresponding to the dog world is"submission", and dogs have more biodiversity and species thriving than any other creatures,because of mankind's intervention, through choosing the individual breeding "looksobedience". People can intervene successfully in such a short time by the adrenaline controltheory.This paper proposes GACAL algorithm, and finds out the adrenaline control parametersin order to assist and guide the fitness function to make it faster to find the optimal solution.This paper introduces the design of GA steps and adrenaline control parameters for Centroidalgorithm in wireless sensor networks, the simulation experiments show that the newalgorithm can improve the localization accuracy effectively.A new energy efficiency algorithm is proposed in this paper based on energyconsumption transference and node gravitation in wireless sensor networks, ETCDGalgorithm is for short. This paper finds network characteristics when failed nodes come up, and makes data transference avoid these nodes in the network. We can avoid the path with thebiggest energy consumption in network by this way, and the energy consumption can bescattered into the whole network by performing this periodically in order to reduce thenetwork energy consumption and increase network lifecycle. Then how to determine thenodes with the highest energy consumption is the key to the problem. Through a large numberof experimental analyses, this paper finds that there is a certain relationship between thenumber of data transference and the number of nodes with the amount of data transference inthe whole network lifecycle. From this point of view, this paper describes this relationship,and gains the distribution features through experiments. According to this feature, ETCDG isput forward in data-transference stage to set strategy to promote energy efficiency of therouting protocol. Nevertheless, during this process, ETCDG produces extra energyconsumption. A new method based on node gravitation is proposed to reduce this extra energyconsumption. Experiments show that ECTDG algorithm can reduce the energy consumptionand prolong the lifecycle of wireless sensor network effectively.Furthermore, the application conditions of the three localization algorithms are analyzedin this paper, and then the shortcomings and the combining method of four algorithms aregiven. Finally, the future research direction is described.