Developed by a team at University College London, the technology is similar in principle to traditional radar, but rather than actively transmitting radio waves, it makes use of the “soup” of Wi-Fi signals that already swamp our airwaves.
Dr Bo Tan, one of the lead researchers on the project, told The Engineer that the technology has potential applications in a range of scenarios, from surveillance of hostage situations to gesture recognition systems. The system could also be used to monitor people in their homes and trigger an alert if they fall, he said.
Tan explained that like traditional radar systems, the technology relies on detecting Doppler shifts in radio waves as they reflect off moving objects.
He said that in order to capture target movement the technology requires at least two receiver channels. One channel locks onto a direct base radio signal from a local wireless signal transmitter (such as a router) whilst the other measures the reference signal as it bounces off a moving target.
By comparing the two signals using software supplied by National Instruments the system is able to figure out the velocity and position of a detected target.
During tests of a two-channel demonstration system, the group was able to use a domestic-strength Wi-Fi signal to detect a walking person, and a range of body gestures through a 25cm thick brick wall.
The next stage is commercialisation, and Tan said that the group has already had discussions with a number of electronics firms and government agencies that are interested in exploring a variety of applications.
Tan added that the complete lack of spectrum occupation and power emission ensures that the radar is undetectable, making it particularly attractive for military or security surveillance.