Bring Your Own Positioning System: An Infrastructure-free and Omnidirectional UWB-based Localization Approach

Wireless ad-hoc localization can play an enabling role for many safety-critical applications and help to save life. For instance, in challenging applications such as firefighting, first responders are often faced with the decision to enter a structure with limited to no visibility and lacking detailed information on the existing conditions. Relative position uncertainty or loss of contact may lower the operation's prospect of success or, in the worst case, result in human harm. This work aims to provide a novel ad-hoc localization system that allows for omnidirectional awareness of co-responders' locations, even under zero-visibility and non-line-of-sight conditions. To this end, we propose a novel ultra-wideband-based localization method combining multiple phase-difference of arrival capable nodes for accurate direction and distance estimation. A tightly integrated hardware setup enables time difference of arrival direction finding, augmenting the limitations of pure phase-based direction estimation. Additionally, single-sided two-way ranging is utilized for ad-hoc distance estimation. We have evaluated the localization performance for different realistic indoor scenarios under line-of-sight and non-line-of-sight conditions. Experimental results show an average 95th percentile 2D accuracy of 40 cm at a distance of up to 6 m in an unobstructed environment. In more challenging conditions which incorporate obstruction an accuracy of 1.2 m at up to 12 m distance could be achieved.