Researchers Use Wi-Fi to Track Movement in Indoor Environments

Researchers from North Carolina State University have developed a technique for measuring speed and distance in indoor environments using Wi-Fi. This technique can be used to improve navigation technologies for robots, drones - or pedestrians trying to find their way around an airport. The technique uses a novel combination of Wi-Fi signals and accelerometer technology to track devices in near-real-time.

This approach is called ‘Wi-Fi-assisted Inertial Odometry (WIO)’. It uses Wi-Fi as a velocity sensor to accurately track how far something has moved. Think of it as sonar, but using radio waves, rather than sound waves. Many devices, such as smartphones, incorporate technology called inertial measurement units (IMUs) to calculate how far a device has moved. However, IMUs suffer from large drift errors, meaning that even minor inaccuracies can quickly become exaggerated.

In outdoor environments, many devices use GPS to correct their IMUs. But this doesn't work in indoor areas, where GPS signals are unreliable or nonexistent. WIO is created to work in conjunction with a device's IMU, correcting any errors and improving the accuracy of speed and distance calculations. This improvement in accuracy should also improve the calculations regarding a device's precise location in any indoor environment where there is a Wi-Fi signal.

The researchers wanted to test the WIO software but ran into a problem: they could not access the Wi-Fi network interface cards in off-the-shelf devices such as smartphones or drones. To address the problem, the researchers created a prototype device that could be used in conjunction with other devices. The researchers found that using WIO improved a device's speed and distance calculations dramatically. For example, devices using WIO calculated distance with a margin of error ranging from 5.9% to 10.5%. Without WIO, the calculated distance of the device can be 40% to 49% with a marginal error.

The researchers are currently working with Sony to further improve WIO's accuracy, with an eye toward incorporating the software into off-the-shelf technologies. The paper, ‘Enhancing Indoor Inertial Odometry with WiFi,’ will be presented at UbiComp 2019, being held from Sept. 11-13 in London, U.K.