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Full duplex radio technology developed that doubles speed of existing wireless networks

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February 14, 2011

The full duplex radio with two transmitting antennas that cancel each other out at the rec...

The full duplex radio with two transmitting antennas that cancel each other out at the receiving antenna

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Whether it be over walkie talkies or Wi-Fi, wireless communication is a one way street, meaning radio traffic can flow in only one direction at a time on a specific frequency. To get around this limitation mobile phone networks use a workaround that is expensive and requires careful planning, making the technique not feasible for other wireless networks. Now researchers at Stanford University have created a full duplex radio that allows wireless signals to be sent and received simultaneously, thereby instantly doubling the speed of existing networks.

The problem the researchers had to overcome is that when a radio is transmitting and receiving at the same time, the incoming signals are drowned out by the radio’s own transmissions.

"When a radio is transmitting, its own transmission is millions, billions of times stronger than anything else it might hear [from another radio]," says Philip Levis, assistant professor of computer science and of electrical engineering at Stanford. "It's trying to hear a whisper while you yourself are shouting," he says.

To overcome this problem a trio of electrical engineering graduate students, Jung Il Choi, Mayank Jain and Kannan Srinivasan, hit upon the idea developing a radio receiver that could filter out the signal from its own transmitter so the weak incoming signals could be heard. Similar to the way in which noise-canceling headphones filter out ambient noise, each radio would know exactly what it is transmitting and therefore what it should filter out.

Jung Il Choi and Mayank Jain (with Kannan Srinivasan, not pictured) began working on a new...

The idea seems so obvious that other researchers even told the students their idea wouldn’t work because something so obvious must have already been tried unsuccessfully. Luckily for the students, the naysayers were wrong and the team successfully developed the first full duplex radio device by designing a radio with two transmit antennas located either side of a single receiving antenna. When the signals from the two transmitting antennas meet at the receiving antenna, they effectively cancel each other out – not completely, but enough to allow the receiving antenna to pick up signals from other radios.

The most obvious advantage of the technology is that it instantly doubles the amount of information that can be transmitted, but it also has other benefits. With current air traffic control systems, when two aircraft try to call the control tower at the same time on the same frequency neither will get through. The new system would prevent such potentially disastrous scenarios.

Before the technology is practical for use in Wi-Fi networks the team will need to increase both the strength of the transmissions and the distance over which they work. They are currently working on this but are even more excited about the possibilities once hardware and software are built to take advantage of simultaneous two-way transmission.

The Stanford University students demonstrated their device last year at MobiCom 2010, where they took out first prize for best demonstration. The group has a provisional patent on the technology and is now working to commercialize it.

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag.   All articles by Darren Quick
2 Comments

seems revolutionary !!!

now make sure this doesnt die in the lab itself as so many promising discoveries have in the past!

Atul Malhotra
15th February, 2011 @ 09:53 am PST

I also would have thought this had already been considered, so it's impressive that they persevered despite the naysayers. It like Tesla's insistence on further developing AC when Edison had the world convinced DC was the best option. Looking forward to doubled speed on wireless networks in the near future.

Brutal McKillins
15th February, 2011 @ 12:20 pm PST
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