The following tests were realized with only 5 bases (detectors). Better precision and 3D positioning would have been achieved if more bases could have been placed on upper floors.
Bases are not synchronized: time fluctuations are estimated and compensated by the system at runtime. Tag positions are estimated and displayed every second (videos are a bit accelerated).
Indoor tests – office
Indoor tests – exhibition
Indoor tests – parking lot
- Localization by TDOA (Time Difference Of Arrival).
- Tags transmit, bases (detectors) receive.
- 20Mhz-wide proprietary radio modulation and protocol in the 2.4GHz band.
- 2ms-long transmissions, –137dB receiver sensitivity.
- More than 1km range in line-of-sight conditions.
- Bases are not synchronized: time fluctuations are estimated and compensated by the system at runtime.
- Measured times of arrival are collected by Ethernet connections (could be replaced by wireless links).
- Programmable transmit rate from 10 times per second to once per day.
- Small form-factor tags (30mm × 30mm), can operate with a standard coin cell while transmitting every 10s.
- Tags include an accelerometer for various purposes (fall detection, battery saving while not moving…).