The Localization Technology Based On TDOA For Wireless Sensor Network Nodes

Wireless sensor networks as new information acquisition and the processing technology, it has very broad application prospects in the military and national defense, the industry and agriculture, the environmental monitoring, the physical health, and many other fields has the significant application value. Wireless sensor networks are considered the most important technology of the future of humanity it will have a great impact on the way of life. For most applications, there is no marking data location is limited, it has become a positioning sensor network one of the essential support technologies, at present has received the domestic and foreign scholar's widespread attention.At present, compared with perfect localization technology such as GPS localization technology, because of the location time and positioning accuracy as well as the complex environmental limits, is unable to be competent completely the fully-directional localization need, especially in the indoor environment, it is almost entirely unavailable. Therefore, related high accuracy localization technology's research has receives pays attention, many research devote is to use small, light, cheap sensor set up wireless sensor networks that can replace GPS technology. The existing wireless sensor network localization algorithm may divide into two categories: range-based on technology positioning algorithm and range-free on technology positioning algorithm. As sensor nodes energy, cost, size and other factors, range-free positioning algorithm has higher practicability. However, the most distance irrelevant algorithms request the anchor node high-density uniform distribution, resulting in increased costs of the network, the correspondence communications competition and conflict intensifies, severely limits the distance unrelated to the application of positioning algorithm, called anchor nodes sparse problems. Distance positioning algorithm can be related to high accuracy positioning, moreover uses in the indoor localization, this article main research range-based localization technology.In the wireless sensor network each node in a space coordinate system determined that oneself space position the process is called the node localization. In sensor node localization technology, according to the location of the node identification, the sensor node divides into the anchor node and the unknown node. The anchor node position is known, the unknown node needs according to the minority anchor node, to determine own position according to some kind of localization mechanism. The anchor node in the network nodes in the proportion of small, can be deployed manually or can carry GPS positioning equipment get their precise position. The unknown node may extract own exact location through some algorithms according to the anchor node obtained their precise position.The time difference of arrival localization is based on range-based wireless sensor network localization methods, and has been widely used in the positioning of cellular networks. This chapter involves the wireless sensor network localization algorithm main research basis minority anchor node position, according to some kind of localization mechanism determined that other nodes the positional information, then we can achieve the concern of the incident location information.This article mainly research based on time difference of arrival wireless sensor network localization. This localization method does not need the node the overall synchronization, reduces node the extra hardware expenses, reduced the node power loss and the cost. Because the unknown node only needs to monitor the signal which passively three anchor nodes send out, does not need the initiative transmitting message, reducing sensor nodes such effective communication. This article mainly obtains many group of time difference of arrival time differences according to the mutual correlation method, to be converted into the distance between two nodes anchor, can be established about the testing node position hyperbolic equations, the solution hyperbolic curve equation uses the least squares method, the weighting least squares method and the Chan algorithm, applies to these three methods based on Range-Based the technical wireless sensor network localization results were improving. Because the least squares method, the weighting least squares method and Chan the algorithm obtains the node is scattered, finally application of these three algorithm cancroids weighted average secondary location, the localization effect obviously enhancement so that the positioning Convergence of better results. The least squares method, the weighting least squares method and Chan algorithm these methods apply in the cellular network localization are widespread, this article applies them in the WSN positioning system has the very good localization application.