Abstract
With the increasing demand for location awareness, indoor positioning has gradually become one of the research hotspots. In recent years the indoor positioning research field generally introduced dilution of precision (DOP) in the field of satellite navigation to the optimization of base station (BS) configuration, but in practice, the distribution of DOP and the distribution of errors is far from the same. This paper analyzes the applicability of DOP in the indoor time difference of arrival (TDOA) positioning systems from various aspects. Then, according to the ultrawideband (UWB) ranging error model, the TDOA time-difference measurement error model is derived and used as the BS configuration optimization metric. Finally, the experiments are conducted in 8 m $\ast ~8$ m $\ast ~3$ m small-scale scene and 100 m $\ast ~30$ m $\ast ~10$ m large-scale scene respectively to compare the positioning accuracy of the three BS configurations under different receiving signal-to-interference ratio (SIR). At the same time, the experiment is conducted in outdoor standard football field to compare the influence of multipath on the positioning accuracy of the three BS configurations under the conditions of two SIR. The experimental results show that the optimized BS configuration with DOP as the optimized target is not the best BS configuration, and the positioning accuracy is not as good as the commonly used cuboid 8-BS configuration in low SIR environment. It proves that DOP cannot be used as a decisive metric for the BS configuration optimization of UWB indoor positioning, but can be used as a reference index, and the optimized BS configuration with TDOA time-difference measurement error as the optimization target has higher positioning accuracy.
Highlights
With the development of wireless communication technology, location-based services have become a basic requirement for many Internet of Things (IoT) applications
In studies on the base station (BS) configuration optimization of indoor positioning, Sharp et al analyzed geometric dilution of precision (GDOP) for several specific cases and compared it with simulations of several typical geometries of indoor positioning system, and the results showed that GDOP exhibited good agreement with experimental results except when the mobile station (MS) was close to the BS [2][7], but due to NLOS and multipath issues in the indoor environment far more complex than Global Navigation Satellite System (GNSS), GDOP usually overestimating the accuracy of the positioning results when the MS is close to BS
The relationship between dilution of precision (DOP) and BS configuration is deduced according to the formula for solving DOP, and the limitations of DOP in the UWB indoor time difference of arrival (TDOA) positioning system are demonstrated from various analyses
Summary
With the development of wireless communication technology, location-based services have become a basic requirement for many Internet of Things (IoT) applications. Radio-based positioning has been widely used in navigation and tracking, and satellite-based positioning systems, such as the Global Positioning System (GPS), can be employed for in-vehicle and personal navigation. Satellite signals cannot provide reliable location service in an indoor environment because they are blocked by buildings [1]. A number of wireless positioning technologies are available for indoor scenes to position and track people and objects: Bluetooth, Wi-Fi, geomagnetic, pedestrian dead reckoning (PDR), sound, and ultrawideband (UWB) [1].
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