Many devices, such as smartphones, incorporate 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 does not work in indoor areas where GPS signals are unreliable or nonexistent.

A technique was developed for measuring speed and distance in indoor environments that uses a combination of Wi-Fi signals and accelerometer technology to track devices in near-real time. Wi-Fi-assisted Inertial Odometry (WIO) uses Wi-Fi as a velocity sensor to accurately track how far something has moved — similar to sonar but using radio waves, rather than sound waves.

WIO works in conjunction with a device’s IMU, correcting any errors and improving the accuracy of speed and distance calculations. The 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 could not access the Wi-Fi network interface cards in off-the-shelf devices such as smartphones or drones, so they created a prototype device that could be used in conjunction with other devices. Using WIO improved a device’s speed and distance calculations dramatically.

For more information, contact Muhammad Shahzad at This email address is being protected from spambots. You need JavaScript enabled to view it.; 919-515-8766.


Tech Briefs Magazine

This article first appeared in the May, 2020 issue of Tech Briefs Magazine.

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