Positioning System Based On UWB

There has been a great deal of interest in UWB (ultra-wideband) communications, especially after the UWB technology is approved of being employed in civil productions by the FCC (Federal Communications Commission). The UWB technique is becoming a potential one for wireless positioning with many advantages, such as low power, anti-multipath, security and high precision especially. The research of UWB positioning systems, therefore, has great application values.The techniques of UWB positioning systems include two important parts that are ranging and positioning. The main work of the dissertation is as follow:There generally are three methods of ranging for UWB positioning systems, which are according to the time of arrival (TOA), the received signal strength (RSS) and the angle of arrival (AOA). The TOA-based method is adopted in the dissertation after the characteristics of each approach are investigated. Based on widely studying the existing techniques of TOA estimation, we propose two algorithms in the dissertation; the one is based on PCA (Principal Component Analysis) and the other is based on Kalman filtering. The former uses the spectral analysis of the autocorrelation matrix of the received signal disturbed by noise in order to get the sum of the energy of projections in signal space. And then we can get the TOA by selecting a threshold with low complexity and sampling rate. This algorithm can eliminate noise effectively and obtain high accuracy, but the amount of calculation is large and it is hardly to implement real-time processing. The later can easy to deal with this problem by using Kalman filtering. We only analyze the received signal samples by PCA within a predefined window in a frame period so as to reduce the computational complexity. The center of the window in current frame is the predicted TOA value during the previous frame with Kalman filtering, and the size of the window is determined by system models.There are two kinds of methods in UWB positioning system, which are non-iterative and iterative algorithms. Taylor series expansion method has been widely used in solving nonlinear equations for its high accuracy and robustness, but its results depend highly on the initial coordinate estimation of a mobile station. With the purpose of resolving this problem, a new algorithm based on the coordinate of base station and the TOA estimation is proposed to estimate the initial coordinate of mobile station. The main idea behind this algorithm is to use the coordinate of base station which can receive the signal of the mobile station to estimate the initial coordinate of mobile station.Extensive experiments carried out show that both TOA estimation algorithms are robust to noise and multipaths and the precision of TOA estimation can achieve ns order. The positioning algorithm based on the coordinate of base station and the TOA estimation is simple and feasible and satisfies the requirements of the initial coordinate of mobile station by Taylor series expansion.