Impact of Altitude of Anchors on Performance of UWB Real-Time Locating System

Ultra-wideband (UWB) technology has recently improved the performance of real-time locating systems (RTLS) to centimeter-level accuracy. One of commercially available integrated circuits (IC) for UWB RTLS is from Decawave. Its DW1000 IC can be used in two-way ranging (TWR) method to measure precise time of flight, thus accurate estimation of the distance between an anchor and a tag. A trilateration algorithm can then estimate the position of a tag in two-dimensional (2-D) and three-dimensional (3-D) space from the distance between the tag and three or more anchors. In this work, the impact of altitude of anchors above the tag on the performance of a TWR UWB RTLS was studied. In the experiments, the anchors and tag were first placed on the first floor of a building. Then, some of the anchors were raised or moved to higher floors. The results revealed that the error distances along x-, y-, and z-axis varied differently with increasing altitude of the anchors, thus changing their contribution to the 2-D and 3-D performance. The results indicated that altitude of anchors dramatically affected the performance, especially in 3-D. The results can help suggest how to find optimal positions of anchors for deployment of the RTLS.