Scientists use Wi-Fi routers to see humans through walls

Researchers demonstrate how Wi-Fi can be used for monitoring - and why it might actually be a good idea.
Written by Liam Tung, Contributing Writer
Image: Getty Images/iStockphoto

Scientists from Carnegie Mellon University have developed a cheap way to sense humans through walls by using two Wi-Fi routers to image a human's 3D shape and pose. 

The researchers outline in a new paper how they used a deep neural network called DensePose that maps Wi-Fi signals (phase and amplitude) to UV coordinates, which is when a 3D model's surface is projected to a 2D image for mapping a computer-generated image. 

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DensePose was developed by researchers at Imperial College London, Facebook AI, and University College London. 

The Carnegie Mellon researchers' key achievement with DensePose, first reported by Vice, is that they can accurately map multiple subjects' poses with an off-the-shelf 1D sensor -- Wi-Fi antennas -- rather than expensive RGB cameras, LiDAR, and radars. Also, they were able to use Wi-Fi to sense humans and their pose, rather than just being able to only accurately locate an object in a room.    

"The results of the study reveal that our model can estimate the dense pose of multiple subjects, with comparable performance to image-based approaches, by utilizing Wi-Fi signals as the only input. This paves the way for low-cost, broadly accessible, and privacy-preserving algorithms for human sensing," researchers Jiaqi Geng, Dong Huang, and Fernando De la Torre explain in their paper, DensePose From WiFi

The researchers ague that their Wi-Fi approach to imaging humans in households could be applied to home healthcare, where patients may not want to be monitored with a camera in places like the bathroom or with other sensors and tracking devices. 

Importantly, the Wi-Fi-monitoring system is not impacted by poor light or obstructions, such as walls. Also, it requires a very cheap setup, using equipment most people have at home already. The two TP Link Wi-Fi routers used in the study cost about $30 each, versus around $700 for the most common LiDAR.

"We believe that Wi-Fi signals can serve as a ubiquitous substitute for RGB images for human sensing in certain instances. Illumination and occlusion have little effect on Wi-Fi-based solutions used for interior monitoring. In addition, they protect individuals' privacy and the required equipment can be bought at a reasonable price," the researchers write. 

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"In fact, most households in developed countries already have Wi-Fi at home, and this technology may be scaled to monitor the well-being of elder people or just identify suspicious behaviors at home."

As the researchers note, there is a lot of literature on detection, tracking, and dense pose estimation from images and video, but very little on the subject of human pose estimation from Wi-Fi or radar. 

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