Design And Implementation Of Real Time Locating System Based On CSS Techniques

With rapid progress and development of science, the node location information has an irreplaceable core role in the network applications. The GPS system has successfully solved the outdoor localization, and has brought enormously beneficial impacts to people’s life. In the application scenarios without GPS signal, however, the investigation of wireless positioning is a subject of intense interest in the field of sensor network. For the situation without GPS signal, this thesis designs and implements a high precision wireless real-time locating system based on the Chirp Spread Spectrum techniques.Firstly, this thesis designs the system architecture and implements the wireless real-time locating system. Secondly, the data filter algorithm and positioning algorithm which can mitigate the NLOS problem are researched. Finally, this thesis tests system functionality and performance in indoor and outdoor respectively. Specific contents are as follows:(1) Locating system requirements analysis and architecture design:Firstly, wireless location technology and methods at home and abroad are analyzed and compared. Then the CSS technology combined with SDS-TWR algorithm is selected, which is a TOA ranging method to implement wireless locating system.(2) The realization of wireless real-time locating system:Firstly, this thesis implements the hardware design and debug, which is based on NanoPAN5375 module and Atmel MCU. Secondly, the thesis realizes SDS-TWR ranging algorithm between anchors and tags. And the thesis carries out the TDM scheduling and multipoint ranging, data extraction, protocol analysis, data filtering and positioning algorithm, etc.(3) Mitigating NLOS transmission interference. In the aspect of improving ranging error, SDS-TWR ranging algorithm and curve fitting method can reduce accidental error, an improved Kalman filtering algorithm is proposed to smooth range data and to abate the NLOS range error. In terms of localization algorithm, the thesis performs the weighted least squares localization algorithm combined with Min-Max. And at the same time, the paper realizes residual weighting algorithm to decrease the NLOS error and locating estimation error.(4) Testing locating system functionality and performance under different scenarios: locating system is equipped with zone location, one-dimensional location, two-dimensional location and tracking function. The indoor and outdoor location accuracy can reach about 1 m.