Stanford researchers have developed the first wireless radios that can send and receive signals at the same time, unlike the current radio traffic that can flow in only one direction at a time on a specific frequency.
The breakthrough has been achieved by a trio of electrical engineering graduate students, Jung Il Choi, Mayank Jain and Kannan Srinivasan, under guidance of professors Philip Levis, and Sachin Katti.
They are currently trying to increase both the strength of the transmissions and the distances over which they work. These improvements are necessary before the technology is practical for use in Wi-Fi networks.
The technology could have wide ranging impacts, such as overcoming a major problem with air traffic control communications.
The group has a provisional patent on the technology and is working to commercialise it.
With current systems, if two aircraft try to call the control tower at the same time on the same frequency, neither will get through.
These blocked transmissions have caused aircraft collisions, which the developers believe can be prevented with their new technology in near future.
But according to researchers, even more promising are the system’s implications for future networks.
Levis said once hardware and software are built to take advantage of simultaneous two-way transmission, there’s no predicting the scope of the results.
It took the students several months to figure out how to build the new radio. Their main roadblock to two-way simultaneous conversation was this: Incoming signals are overwhelmed by the radio’s own transmissions, making it impossible to talk and listen at the same time.
Levis said, "When a radio is transmitting, its own transmission is millions, billions of times stronger than anything else it might hear [from another radio]. It’s trying to hear a whisper while you yourself are shouting."
But, the researchers realised, if a radio receiver could filter out the signal from its own transmitter, weak incoming signals could be heard.
"You can make it so you don’t hear your own shout and you can hear someone else’s whisper," Levis said.
Their setup takes advantage of the fact that each radio knows exactly what it’s transmitting, and hence what its receiver should filter out. The process is analogous to noise-canceling headphones.
