Summary

Indoor localization encompasses a suite of methods and systems designed to determine the position of people or objects within enclosed spaces where satellite navigation signals are unreliable or unavailable. Core techniques exploit various physical phenomena: radiofrequency measurements such as received signal strength, time or angle of arrival; ultrawideband signalling for high-precision ranging; Bluetooth Low Energy beacons and Wi-Fi fingerprinting for scalable deployment; visible light positioning using modulated luminaires; and hybrid schemes that fuse inertial sensors, landmarks and environmental cues. Recent advances in sensor fusion and machine learning have greatly enhanced robustness against multipath interference and non-line-of-sight conditions, while emerging platforms harness low-power electronics, energy harvesting and battery-free tags. Applications span smart manufacturing and logistics, asset tracking in hospitals and construction sites, immersive wayfinding in museums and retail, emergency response in fire and search-and-rescue operations, and next-generation human–machine interfaces. The integration of indoor positioning into the Internet of Things promises context-aware services, dynamic space management and automated workflows, underscoring its growing impact on urban infrastructure and industry 4.0. Nevertheless, challenges remain in standard isation, privacy protection, seamless handover across diverse infrastructures and cost-effective coverage in complex architectural environments.

Research from Nature Portfolio

Recent studies have demonstrated a novel passive radiofrequency approach that wirelessly generates an evenly spaced frequency comb for far-field ranging without onboard power. This quasi-harmonic tag leverages nonlinear interactions in a piezoelectric microacoustic resonator coupled to an RF parametric oscillator, achieving centimetre-level accuracy under micro-watt illumination. By passively harvesting broadcast energy, the system delivers robust immunity to multipath interference and operates in GPS-denied settings, suggesting new pathways for battery-free localisation of unmanned vehicles and low-maintenance asset tags in industrial or hazardous environments. The work opens a fresh frontier in RF-based indoor positioning by combining metrological techniques with wireless sensor design to overcome conventional limitations of range, power and environmental robustness.

Indoor Localization Techniques and Systems publication trend

The graph below shows the total number of articles in indoor localization techniques and systems across all publications each year (not limited to Nature Index journals).

Technical terms

Received Signal Strength (RSS): Power level measured at a receiver, used to infer distance from a transmitter.

Time of Arrival (TOA): The travel time of a signal from transmitter to receiver, enabling range estimation.

Angle of Arrival (AOA): The incident direction of a signal relative to a reference, used for triangulation.

Fingerprinting: Mapping of environmental signal patterns to known locations for later matching during positioning.

Multipath Interference: Signal reflections and scattering in enclosed environments that can degrade measurement accuracy.

Kalman Filter: An algorithm that fuses sequential measurements and system dynamics to produce optimal state estimates.

Visible Light Positioning (VLP): Localization using modulated light signals from LEDs detected by optical sensors.

Ultrawideband (UWB): Radio technology transmitting over a wide frequency band for high-resolution ranging.

Frequency Comb: A spectrum of equally spaced frequencies generated to enable precise distance measurements.

References

  1. Visible Light Positioning as a Next-Generation Indoor Positioning Technology: A Tutorial. IEEE Communications Surveys & Tutorials (2024).
  2. Passive frequency comb generation at radiofrequency for ranging applications. Nature Communications (2024).
  3. RFID localization in construction with IoT and security integration. Automation in Construction (2024).
  4. A Novel Convolutional Neural Network Based Indoor Localization Framework With WiFi Fingerprinting. IEEE Access (2019).

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