| Clipped from: Wireless Network Signals Produce See-Through Walls | Threat Level | Wired.com |
Wireless Network Signals Produce See-Through Walls
Researchers at the University of Utah have found a way to see through walls to detect movement inside a building.
The surveillance technique is called variance-based radio tomographic imaging and works by visualizing variations in radio waves as they travel to nodes in a wireless network. A person moving inside a building will cause the waves to vary in that location, the researchers found, allowing an observer to map their position.
| Clipped from: Technology Review: Blogs: arXiv blog: Wireless Network Modded to See Through Walls |
Wireless Network Modded to See Through Walls
The way signal strength varies in a wireless network can reveal what's going on behind closed doors.
The basic idea is straightforward. The signal strength at any point in a network is the sum of all the paths the radio waves can take to get to the receiver. Any change in the volume of space through which the signals pass, for example caused by the movement of a person, makes the signal strength vary. So by "interrogating" this volume of space with many signals, picked up by multiple receivers, it is possible to build up a picture of the movement within it.
| Clipped from: Radio Tomographic Imaging | SPAN |
Sensing and Processing Across Networks at Utah
Radio Tomographic Imaging
Radio Tomographic Imaging (RTI) is an emerging technology that locates moving objects in areas surrounded by simple and inexpensive radios. RTI is useful in emergencies, rescue operations, and security breaches, since the objects being tracked need not carry an electronic device. Tracking humans moving through a building, for example, could help firefighters save lives by locating victims quickly.
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The following video is an RTI experiment conducted by Joey Wilson and Neal Patwari at the Warnock Engineering Building at the University of Utah. The attenuation image is shown above the actual footage, with the red spots indicating heaviest attenuation.
| Clipped from: Radio Waves 'See' through Walls - University of Utah News Release: October 11th, 2009 |
On the left, a person walks around inside a square of 28 radio transceivers (mounted on plastic pipes) in the Warnock Engineering Building's atrium at the University of Utah. The person creates "shadows" in the radio waves, resulting in the image displayed on right, in which the person appears as a reddish-orange-yellow blob. University of Utah engineers also showed this method can "see" through walls to make blurry images of people moving behind the walls. They hope the technique will help police, firefighters and other emergency responders apprehend burglars and rescue hostages, fire victims and others.
University of Utah electrical engineer Neal Patwari walks around inside a square grid of radio transceivers (mounted on plastic pipes) during a test of a radio tomographic imaging (RTI) system that uses radio waves to "see," locate and track a moving person -- even a person moving behind a solid wall.
Sources:- Wireless Network Signals Produce See-Through Walls | Threat Level | Wired.com
- Technology Review: Blogs: arXiv blog: Wireless Network Modded to See Through Walls
- Radio Tomographic Imaging | SPAN
- Radio Waves 'See' through Walls - University of Utah News Release: October 11th, 2009
- Wi-Fi signals used to see through walls - Telegraph
- Researchers see through walls with wireless mesh - Ars Technica
- Attn Nerdy Pervs: See Through Walls Using a Wireless Network - Wireless - Gizmodo
- Radio waves 'see' through walls | Science Codex
- [0909.5417] Through-Wall Tracking Using Variance-Based Radio Tomography Networks
- arXiv.org e-Print archive
- SPAN | Sensing and Processing Across Networks at Utah
