Research On Wireless Location And Location Parameters Estimation Algorithms

Location Based Service is a value added service. It often uses different location technology along with Geography Information System, provides location information for users through mobile communication network. Along with the rapid development of the mobile communication technology, more and more users hope mobile communications systems could provide more accurate location services. The mobile location technique has become one of the hottest problems in recent years.The process of calculating the location estimate could be regarded as consisting of two parts. The first part provides estimation of TDOA/AOA location parameters and the second part is using location algorithms to determine the MS's position.The common using method in time delay estimation is generalized cross correlation (GCC), but it has a definite limitation in overcoming correlative noise in space. For improving TDE's performance, this paper analyzes time delay estimation method which uses bispectrum, because original bispectrum algorithm is not good enough in distinguishing, this paper modifies it. The simulation result justifies that the improved algorithm is more effective in TDE estimation than original bispectrum algorithm.For AOA estimating algorithm, this paper analyzes traditional Bartlett, Capon and MUSIC. The simulation proves that the MUSIC is the best in evaluation accuracy. But traditional MUSIC algorithm can not distinguish correlative signal. For correlative signal's AOA estimation, this paper analyzes classical forward/ backward spatial smoothing algorithm, and a modified MUSIC algorithm. The simulation result justifies that the modified MUSIC algorithm could get better performance than spatial smoothing algorithm in AOA estimation.For location algorithm in cellular network, this paper mainly discusses some kinds of classical location algorithm in LOS environment. The simulation result indicates that Chan algorithm is the best in Gauss environment for single TDOA location algorithm. TDOA/AOA mixed location algorithm always has better precision than single TDOA location algorithm. The mixed location algorithm could get better capability when AOA measurements are more accurate. Aiming at NLOS (non-line of sight) problem in wireless location, this paper improves on traditional Chan algorithm, basic approach is using Kalman filter to optimize TOA measurements and lighten NLOS error's influence at first, then using reformative TOA measurements to get TDOA measurements, finally using Chan algorithm to get MS's position. The simulation result justifies that improved Chan algorithm has better performance than traditional Chan algorithm in NLOS environment.