We’ve all heard the familiar line — “Let’s synchronize our watches” — before a group goes out on a perilous mission.
And we’re all familiar with the concept of synchronized clocks. Less known, but equally important, is that wireless devices need to be synchronized, too. However, instead of requiring a precision of minutes, wireless devices have to make their clocks match within fractions of a second.
This so-called “clock synchronization” is needed for a range of purposes — from increasing cellphone coverage to increasing data speed rates to setting precision localization in areas where GPS is not available.
Appearing this week at the 2015 IEEE International Conference on Communications in London, Andreas Molisch, professor of electrical engineering at the USC Viterbi School of Engineering, presented a paper co-authored with Marcelo Segura and S. Niranjayan, former postdoctoral students at USC, and Hossein Hashemi, also a professor of electrical engineering at USC Viterbi. The researchers experimentally demonstrated the first wireless network synchronized with nanosecond accuracy.
That’s a nanosecond, as in a billionth of a second.
The ‘Blink’ algorithm
Segura, Niranjayan, Hashemi and Molisch have developed a prototype consisting of four nodes that synchronize to each other with an accuracy of approximately three nanoseconds. They also introduced a scalable protocol, which they call the “Blink” algorithm, that extends the same accuracy of the current small-size prototype (in this case, four wireless devices) to hundreds or even thousands of wireless devices.
“Previous research has addressed precision synchronization, but, in the publicly available literature, nanosecond accuracy was achieved only by connecting devices via cables and only between few wireless devices,” Hashemi said. “Even though GPS is widely used and is considered very precise, it does not easily provide this level of accuracy and cannot be used in many indoor settings.”
Added Molisch: “Our group’s “Blink” protocol will allow for wireless transmission over longer distances with less energy and stands to improve the overall efficiency of wireless networks.”
With this enhanced technology, the engineers believe that applications such as coordinated signal jamming of enemy military receivers; extremely precise localization; and coordinated navigation, tracking and operation of UAVs will all be possible in the future.
While this work has several applications for the military, it also has practical use for other situations in which increased precision is necessary, such as communication among a group of driverless cars to share location information. Other possible applications include helping a person with limited sight navigate an indoor physical space or providing a map for robots employed in the home or in industrial settings.
The research was supported primarily by the Office of Naval Research and the Ming Hsieh Institute at USC Viterbi.