Pseudorange-Based IR-UWB Localization

The application of the impulse-radio ultra-wide band technology is already established in indoor localization. Usually, two-way ranging (TWR) or time-difference of arrival (TDoA) approaches are utilized. In this paper it is shown that it is possible to perform time of arrival (ToA) positioning with accuracy similar to the TDoA. The ToA method estimates the bias between the clocks of the anchors (fixed infrastructure nodes) and the tag (localized user equipment). As a direct consequence, any timestamps taken by the tag may be converted to the common system timescale with accuracy of several nanoseconds. The approach is verified by real measurements. We demonstrate that the positioning solution can be obtained by least-squares optimization on epoch-by-epoch basis. We also show that the extended Kalman filter can be used to estimate tag position along with the bias and drift of its clock.