Radio Waves Offer Cheap Gesture Detection on Smartphones

A research project at the University of Washington shows a way to add gesture control to phones without requiring sophisticated new sensors. It works by identifying the interference that hand gestures cause in the radio signals that are already transmitted to and from a phone.

Called SideSwipe, the project could make it possible to answer a call with a wave of a hand, even if your device is buried deep in a bag. It might let you scroll through a recipe without putting your dirty hands on the display, or navigate a map without having to obscure any part of it with your fingers.

The key to SideSwipe is looking at how hand movement changes the wireless signal and using that to determine specific gestures. A paper on the project will be presented in October in Hawaii at the annual ACM User Interface Software and Technology Symposium.

The researchers investigated signal interference on phones that use the wireless standard GSM because it’s extremely common around the world (in the U.S., T-Mobile and AT&T use it), though they say the technology could also work with newer wireless standards like LTE.

To detect gestures in the lab, researchers connected a Samsung Nexus S smartphone to an array of four receiving antennas that could measure changes to GSM signals resulting from gestures made in various directions when calls were in progress. Researchers tested the system by asking 10 people to use 14 gestures each. The system could accurately detect those gestures 87 percent of the time at a distance of 25 to 30 centimeters from the handset.

The researchers say this kind of gesture recognition could be added to smartphones using antennas already within the phone or by printing additional antennas on a phone’s circuit board. But to become part of your smartphone, SideSwipe would need to pique the interest of smartphone makers.

The SideSwipe prototype smartphone was used to sense gestures only when the phone was in the process of making a call, because that guaranteed a GSM signal. But Chen Zhao, a UW graduate student and coauthor of the research paper, says an app running in the background on the phone could potentially sniff out and translate incoming gestures at other times, providing it could access the device’s GSM module.

For now, the researchers are refining their external antenna design, and plan to test SideSwipe with activities like walking and running, and explore how it can work with other wireless network technologies.