Abstract:
Time-based ranging approaches have long been used for indoor positioning due to their reliability and accuracy. Two-way ranging (TWR) with ultrawideband (UWB) has often been utilized for indoor positioning systems (IPSs) in industrial settings due to the ranging accuracy offered by the temporal and spatial resolution of UWB even in challenging non-line-of-sight (NLOS) and reflective environments. With the adoption of the IEEE 802.11mc Standard, Wi-Fi now offers a fine time measurement (FTM) capability that supports the Wi-Fi round trip time (RTT) protocol for time-of-flight (ToF) ranging. This offers an improved ranging accuracy over previous non-time-based Wi-Fi ranging approaches and is considered a potential alternative to UWB TWR. In this article, we introduce UWB TWR and Wi-Fi FTM and discuss their use in real-time IPSs. We include a quantitative comparison of ranging performance in LOS and NLOS ranging measurements to give an initial indication of accuracy in industrial settings. Recommendations for researchers and IPS designers on which technology type to deploy for LOS and NLOS conditions as well as general guidelines for accurate ranging and localization for both technologies are also discussed.
