"Two-way" radio breakthrough doubles Wi-Fi performance

 

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By Stewart Mitchell

Posted on 15 Feb 2011 at 12:54

Wi-Fi and mobile phone radio network speeds could double after scientists showed radio is able to send and receive over the same frequency at the same time.

The technology would overcome the problem best exemplified by pilots having to say “over” each time they take turns in talking over radio, but it could also be applied to wireless data networks, scientists at Stanford University said.

"Textbooks say you can't do it," said Philip Levis, assistant professor of computer science and electrical engineering at Stanford. "The new system completely reworks our assumptions about how wireless networks can be designed. Unlike radio before it has the unique ability that it can receive and transmit at the same time.”

The technique mimics the way humans are able to screen out the sound of our own voices during a conversation.

"It's like two people shouting messages to each other at the same time," said Levis. "If both people are shouting at the same time, neither of them will hear the other."

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

According to the researchers, the breakthrough uses two transmitters in the hardware at each end of a conversation, with the two transmitters working in a similar way to noise-cancelling headphones.

“The two transmit signals interfere destructively at the receive antenna to create a dead signal that the receiver can’t ‘hear’,” said Levis. “So you create this null position where the receiver can’t hear that signal and so is able to receive packets from other areas.”

The researchers claim this immediately makes radio equipment twice as fast as existing technology, and with further tweaking could lead to even faster and more efficient networks.

Current phone networks allow users to talk and listen simultaneously but, the scientists said, they use a work-around that is expensive and requires careful planning.

The researchers have not detailed when the technology might appear in hardware, but said they had applied for a patent and were working to commercialise it and improve signal strength to make it more suitable for Wi-Fi networks.