Plug-and-play Indoor GPS Positioning System with the Assistance of Optically Transparent Metasurfaces

Due to the poor indoor coverage and positioning accuracy, existing indoor GPS positioning systems leverages additional RF infrastructure as relay with known position. However, in practice, learning the relay position requires establishing an additional connection between user and relays, which is user unfriendly and even infeasible. In this paper, we propose GPSWindow, a plug-and-play indoor GPS positioning system without the prior knowledge of the relay position. By attaching optically transparent metasurfaces to windows, GPSWindow focuses the incident signal towards determined direction and provide an indoor continuous GPS signal coverage. We exploit the difference between consecutive satellite measurements and the Doppler shift measurements to recover the satellite-to-user true distance from the measured satellite-metasurface-user distance, and then locate the user using the traditional trilateration positioning method, eliminating the requirement of relay position. We also design an error correction method that leverages IMU on smartphone and the Doppler shift information to enhance GPSWindow in mobile scenarios. Extensive real-world experiments demonstrate that GPSWindow can provide continuous position service and achieve median positioning accuracy of 3.6m in indoor environments.