Research On Wireless Localization Technology

Localization is to obtain the position of the target in certain coordinate system in accordance with some methods. Wireless localization is the most widely used in all localization techniques (such as localization based on ultrasound, infrared ray and laser, radiolocation, etc). It is one of the key issues in the applications of wireless communication systems. It provides services based on location for the network, which can assist the network optimization, the optimization of transmitters and receivers, interference suppression, resource allocation, surroundings identification, target localization, etc. Based on the measurements of the radio parameters transmitted or reflected by the target, such as, time of arrival, signal strength, Doppler frequency shift, and measurement parameters obtained according to the radio propagation models, such as distance, distance difference and direction, wireless localization makes use of the equations of anchor nodes(at least three) to get the positions of the target. Cooperative localization is one of the processing techniques with broad application prospects. It takes the cooperation of the sensor nodes into account, which can improve the localization accuracy and extend the localization coverage.The wireless localization technology involves "two aspects" and "three questions" in the paper. The "two aspects" are measurement techniques and localization processing methods and the "three questions" are the conditions for unique localizability, the computational complexity of localization, the complexity of localization in typical nodes deployment scenarios, which are the technology foundation and the theory foundation, respectively. The localization precision is affected by the following factors:(1) the estimation error of the radio parameters affected by channel noise, multipath transmission, shadow, link jam, clock skew, time-varying surroundings and communication system, etc.; (2) the position precision of the anchor node; (3) the measurement error of the measurement parameters obtained according to the radio propagation models; (4) the error caused by position calculation.The principle, characteristics and complexity, etc. of the existing typical wireless localization techniques are investigated in the paper. The advantages and disadvantages and the sphere of application of localization techniques are analysed and their improvements are summarized. And then the theory of wireless localization is analysed through the perspective of graph theory. Hence, a wireless cooperative localization algorithm is proposed, which considers both of the factors affecting the localization precision. To tolerate some minor errors in the information of node position, a reference anchor node is employed. On the other hand, Dixon method is used to remove the outliers of measurements, and the standard deviation threshold and the learning model are put forward to reduce the ranging error and effectively improve the positioning precision. Simulations were run to evaluate the performance of the algorithm. The results show that the proposed algorithm has more precise location and better stability and reduce the negative influences of noise and the location coverage is ensured.