Research On Ultra-wideband Precise Positioning Technology

In recent years, Ultra-Wideband (UWB) technique has been the focus of researchsubjects. Especially following the approval of the UWB technology by the FederalCommunications Commission (FCC) in February2002, it also results in an increasingresearch in UWB applications. UWB has many advantages, including low powerconsumption, high multipath immunity, low system complexity, accurate positionlocalization，which make UWB technology have huge potential among wirelesslocation technologies. No matter in the military field or in the civilian field, itsapplication is becoming wider and wider. If UWB localization is used in targeting,goods tracking or searching and rescuing of urgent accident, people can get twice theresult with half the effort. Therefore, the research of UWB positioning systems hasgreat application values.In this paper, the study focuses on improving the accuracy of ultra-widebandpositioning. Based on ultra-wideband wireless communication theory, this paperanalyzes of ultra-wideband signal and channel characteristics, studies the wirelesslocation methods, and especially focusing on the ranging and positioning algorithm,accomplishes the simulation of ultra-wideband high-precision positioning.This paper analyzes the advantages and disadvantages of a variety ofultra-wideband positioning technology, and finds the technology suitable forultra-wideband positioning based on the theory. The research shows that: the accuracyof the received signal strength positioning technology is poor; the angle of arrivalpositioning technology needs array antenna, which will result in increased costs and isnot suitable for intensive indoor multipath environment; The time of arrivalpositioning technology can fully exploit of the high resolution of UWB signals, andcan achieve relatively high positioning accuracy.Multipath propagation is the main factor of affecting the performance of UWBranging. The most of the current TOA estimation algorithm are based on the strongpath detection or static threshold algorithm, which cannot meet the requirements of the variance of SNR and channel conditions change. Against the limits of thesealgorithms, this paper proposes an algorithm of the dynamic threshold based onskewness using Multi-pulse time-average. The optimal threshold formula is got byfitting the curve of the different skewness and threshold. Simulation results show thatthe algorithm can achieve higher accuracy ranging.The paper analyzes the commonly used algorithm of time difference of arrival(TDOA) technology-Taylor algorithm, Chan algorithm and extended Kalman filteralgorithm for dynamic tracking. Meanwhile, these algorithms are applied toultra-wideband positioning, and we compared the performance of various algorithmsand do the simulation both in the case of static positioning and dynamic tracking. Thesimulation results show that using the proposed TOA estimation algorithm,ultra-wideband positioning system can achieve high-precision positioning in the CM1,CM2environment of the IEEE802.15.4a standard.