Original URL: http://www.theregister.co.uk/2009/10/12/utah_through_walls_by_zigbee/

Boffins demo 'through-walls' people tracker

Ring of Zigbee nodes peers inside building

By Lewis Page

Posted in Broadband, 12th October 2009 11:35 GMT

Boffins in Utah have developed a method of detecting and tracking human bodies through building walls.

The method is called radio tomographic imaging (RTI) and doesn't involve any need for the people being tracked to wear any tag or chip. It works by surrounding the area to be monitored with a perimeter of wireless-network nodes, each of which compares signal strengths from all the others.

When the data from all nodes is assembled, radio-blocking objects such as human bodies can be located to within 3 feet - and this can be done with the radio nodes placed on the other side of walls from the area where the human target is.

Professor Neal Patwari of Utah Uni, one of the inventors of the tech, explains:

"The plan is that when there is a hostage situation, for example, or some kind of event that makes it dangerous for police or firefighters to enter a building, then instead of entering the building first, they would throw dozens of these radios around the building and immediately they would be able to see a computer image showing where people are moving inside the building."

Patwari and his colleagues have carried out peer-reviewed studies using the RTI person-tracker tech indoors and among trees. They have also done a through-walls study, carried out in Patwari's home, which so far is published only on arXiv.org - indicating that it hasn't received approval by other boffins. Here's a vid showing the test setup:

It certainly appears to work, though one does note that there are a lot of windows and the walls of Patwari's home don't look terribly thick.

The off-the-shelf network used in the test devices wasn't WiFi but Zigbee, kit used at the moment mainly in home or industrial automation apps. A working system would be cheap to buy, as most of the necessary hardware is already available. And there are definitely customers out there, many of them already embroiled in much more complicated and expensive efforts along the same lines.

Apart from a portable grid that cops, firemen or soldiers could use to track movements inside a building, Patwari and his colleagues suggest their gear could be installed as part of security or home-automation systems, or be used as a means of border monitoring.

"I have aspirations to commercialize this," says Patwari's co-inventor Joey Wilson.

There's more from Utah Uni here with links to all the published research. ®