Modeling and Assessment on The Tightly Coupled Integration of TWTOA-Based UWB and INS

Conventional indoor positioning techniques (i.e., Wi-Fi, Bluetooth, and ZigBee) have been well researched and widely used for the indoor localization service. However, these methodologies can hardly provide users high-accuracy positioning solution. Along with the rapid developments of the internet of things (IoT), the conventional indoor positioning methods cannot match the high-accuracy requirements of IoT. In this paper, we present a practical high-accuracy indoor positioning algorithm, in which the Two-way Time-of-arrival (TWTOA) ranging-based ultra-wide-band (UWB) is integrated tightly with the inertial navigation system (INS). In such a method, the INS is utilized to overcome the impacts of the non-line-of-sight (NLOS) delays on UWB high-accuracy positioning. According to the experiment results, UWB only can provide decimeter-level positioning accuracy. However, UWB positioning accuracy would degrade significantly while suffering NLOS delays. After integrating these NLOS-contaminated UWB ranges with INS tightly, the influences of NLOS could be inhibited, which results in higher accuracy positioning results. Meanwhile, the field test also demonstrated that the number of available UWB base stations could also present visible impacts on the positioning accuracy of the UWB/INS tightly coupled integration.