Wednesday, September 10, 2014

Seeing Through Walls with WiFi

Design News reports on an interesting development from the University of California Santa Barbara.  The project uses a pair of robots who can scan through walls by pointing WiFi antennas at each other and using simple algorithms to make decisions about what's inside the building.  Headed by Dr. Yasamin Mostofi, a professor of electrical and computer engineering, the University of California, Santa Barbara research team has spent a few years developing the imaging technology.
Imagine unmanned vehicles arriving behind thick concrete walls. They have no prior knowledge of the area behind these walls. But they are able to see every square inch of the invisible area through the walls, fully discovering what is on the other side with high accuracy. The objects on the other side do not even have to move to be detected. Now, imagine robots doing all these with only WiFi signals and no other sensors. In this project, we have shown how to do this.
The approach is simple; much simpler than Synthetic Aperture Radar, which provides nearly photographic quality images by signal processing radar returns.   Instead of manipulating the reflected returns from the radar transmitter, they measure signal strength of transmitted signals going through the space and apply simple mathematical functions to the strength before plotting the strength vs. position.  It's not intended for imaging behind walls, like a military or police operation looking for people hiding, and doesn't seem like it's fast enough to do that.  It's intended for search and rescue operations. 
Here's a demo video from the project web page:

I find it somewhat unusual that Dr. Mostofi's UCSB page shows she has MS and Ph.D. from Stanford in '04 with her BS from Iran's Sharif University of Technology in '97.  I didn't think it was feasible to emigrate from Iran these days, but her MS was '99 which pretty much means she started on it almost immediately after completing her BS.

The image quality isn't as good as SAR but I'll bet the hardware is tons cheaper than a SAR or bistatic imaging radar.  Cheap, low tech approaches to problems definitely have their place. 


  1. UCSB has dome some excellent research.

    Waaaay back when I worked for Hughes Aircraft, Hughes had its own research facility (SBRL, I think it was) in Santa Barbara, and the ideas flowed back-and-forth like water through a sieve.

  2. This provoked a thought: Not long ago I visited a friend in a retirement home, and noticed staff was constantly in motion, interacting with residents. I mentioned to a staff member their engagement level was pretty high, and she said it was partially for psychological reasons, but primarily for early problem detection - falls, other immobility issues which might lead to falls or indicate a need for immediate medical attention.

    My thought is this: I wonder if, with sufficient processing power, some improvements to this might make it possible to immediately detect such issues. For a simple example, a passage or area in which people travel vertically and suddenly the vertical mass disappears, replaced by a horizontal mass at floor level.

    And, venturing into Minority Report territory, enough processor cycles could measure changes in activity type and amount that, conceivably, could indicate a precursor, or the increased probability of one.

    Could be a force multiplier.