Stanford team doubles wireless speed

Posted by Kate Taylor

Stanford researchers have created a new wireless technology that allows signals to be sent and received simultaneously on a single channel. The development could double the speed of existing wireless networks.

While cellphone networks allow users to talk and listen simultaneously, this requires a complicated work-around that's less feasible for other wireless networks such as Wifi.

"Textbooks say you can't do it," says Philip Levis, assistant professor of computer science and of electrical engineering. "The new system completely reworks our assumptions about how wireless networks can be designed," he said.

The technique is based on the way human beings screen out the sound of their own voice when listening and talking simultaneously.

"When a radio is transmitting, its own transmission is millions, billions of times stronger than anything else it might hear. It's trying to hear a whisper while you yourself are shouting," says Levis.

But, the researchers realized, if a radio receiver could filter out the signal from its own transmitter, weak incoming signals could be heard.

Their setup takes advantage of the fact that each radio knows exactly what it's transmitting, and hence what its receiver should filter out - just like noise-canceling headphones.

The most obvious effect of sending and receiving signals simultaneously is that it instantly doubles the amount of information that can be sent.

But Levis also sees the technology having larger impacts, such as overcoming a major problem with air traffic control communications. With current systems, if two aircraft try to call the control tower at the same time on the same frequency, neither will get through. Levis says these blocked transmissions have caused aircraft collisions, which the new system would help prevent.

The group has a provisional patent on the technology and is working to commercialize it. At the moment, the team's working to increase both the strength of the transmissions and the distances over which they work - a necessary step if the technology's to be made practicable for Wifi networks.