Eco-WakeLoc: An Energy-Neutral and Cooperative UWB Real-Time Locating System

Indoor localization systems face a fundamental trade-off between energy efficiency and responsiveness, which is especially important for emerging use cases such as mobile robots operating in GPS-denied environments. Traditional real-time locating system (RTLS) either require continuously powered infrastructure, limiting their scalability, or are limited by their responsiveness. This work presents Eco-WakeLoc, designed to achieve centimeter-level ultra-wideband (UWB) localization while remaining energy-neutral by combining ultra-low power wake-up radios (WuRs) with solar energy harvesting. By activating anchor nodes only on demand, the proposed system eliminates constant energy consumption while achieving centimeter-level positioning accuracy. To reduce coordination overhead and improve scalability, Eco-WakeLoc employs cooperative localization where active tags initiate ranging exchanges, whilepassivetags opportunistically reuse these messages for time difference of arrival (TDOA) positioning. An additive-increase/multiplicative-decrease (AIMD)-based energy-aware scheduler adapts localization rates according to the harvested energy, thereby maximizing the overall performance of the sensor network while ensuring long-term energy neutrality. A comprehensive evaluation demonstrates centimeter-level accuracy with average errors in 3D space of 21.89cm for active tags using Levenberg-Marquardt trilateration, and 25.70cm forpassivetags through cooperative TDOA. The measured energy consumption is only 3.22mJ per localization foractivetags, 951 μJ forpassivetags, and 353 μJ for anchors. Real-world deployment on a quadruped robot with nine anchors confirms the practical feasibility, achieving an average accuracy of 43cm in dynamic indoor environments. Year-long simulations starting from an empty battery, and using solar harvesting from a 10cm2cell under typical indoor lighting conditions, show that tags achieve an average of 2031 localizations per day, while retaining over 7%battery capacity after one year – demonstrating that the RTLS achieves sustained energy-neutral operation. Eco-WakeLoc demonstrates that high-accuracy indoor localization can be achieved at scale without continuous infrastructure operation, combining energy neutrality, cooperative positioning, and adaptive scheduling to enable maintenance-free deployments suitable for large-scale Internet of Things applications.