Orientation and Location Tracking of XR Devices: 5G Carrier Phase-Based Methods

• Published in: IEEE journal of selected topics in signal processing Vol. 17; no. 5; pp. 1 - 16
• Main Authors: Talvitie, Jukka, Saily, Mikko, Valkama, Mikko
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.09.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 3D orientation estimation; 3D positioning; 5G mobile communication; 5G NR; Algorithms; Antenna measurements; Antennas; Bayesian filtering; carrier phase; clock drifting; Estimation; Extended Kalman filter; extended reality; integer ambiguity; Integers; Lower bounds; Network latency; Orientation; Phase measurement; Root-mean-square errors; six degrees-of-freedom; Three-dimensional displays; tracking; Tracking devices; X reality
• ISSN: 1932-4553; 1941-0484
• DOI: 10.1109/JSTSP.2023.3309463

Accurate knowledge of the three-dimensional (3D) orientations and 3D locations of the user devices, such as wearable glasses, is of paramount importance in different extended reality (XR) use cases and applications. In this article, we address the corresponding six degrees-of-freedom (6DoF) tracking challenge of 5G-empowered XR devices. We describe a new uplink (UL) carrier phase measurements based estimation approach, allowing for low-latency 3D orientation and 3D location tracking directly at the 5G network base-stations or gNodeBs (gNBs). Extended Kalman filter (EKF) based practical signal processing algorithms are described while also the applicable Cramér-Rao lower-bounds (CRLBs) are derived and presented. Also, the related aspect of over-the-air estimation of the XR headset antenna constellation or antenna geometry is addressed. Additionally, the important practical challenges related to user equipment (UE) clock drifting as well as integer ambiguities in carrier phase based methods are both considered. Finally, an extensive set of numerical results is provided in an example indoor factory like environment, covering both 3.5 GHz and 28 GHz network deployments. The obtained results demonstrate the feasibility of continuous 6DoF tracking through the proposed approach, with root mean squared error (RMSE) accuracies below one degree for the 3D orientation and below one centimeter for the 3D location, respectively. The results also demonstrate that UE clock drifting and carrier phase integer ambiguities can both be efficiently estimated and tracked, as part of the overall proposed concept and methods.