Breakthrough allows full-duplex over existing wireless systems

Posted by Kate Taylor

Rice University researchers say they've developed a full-duplex wireless technology that could allow wireless phone companies to double the throughput on their networks without adding any more cell towers.

The team says that tests of its system produced a signal quality that was at least 10 times better than any previously published result.

"Our solution requires minimal new hardware, both for mobile devices and for networks, which is why we've attracted the attention of just about every wireless company in the world," says Ashutosh Sabharwal, professor of electrical and computer engineering at Rice.

"The bigger change will be developing new wireless standards for full-duplex. I expect people may start seeing this when carriers upgrade to 4.5G or 5G networks in just a few years."

Full-duplex wireless was long thought impossible for wireless networks. Sabharwal uses the analogy of two people shouting to each other at the same time, so that neither can hear what the other is saying. The solution is either to take it in turns, or to use two different frequencies.

The Rice team overcomes this by employing an extra antenna and some cancellation technology - so that the shouter cannot hear himself, only the other person.

"We send two signals such that they cancel each other at the receiving antenna - the device ears," says Sabharwal. "The canceling effect is purely local, so the other node can still hear what we're sending."

It's not a new idea. But the Rice team is the first to be able to do it at low cost and without requiring complex new radio hardware.

"We repurposed antenna technology called MIMO, which are common in today's devices," says Sabharwal. "MIMO stands for 'multiple-input multiple-output' and it uses several antennas to improve overall performance. We took advantage of the multiple antennas for our full-duplex scheme, which is the main reason why all wireless carriers are very comfortable with our technology."

The team has even gone one step further and achieved asynchronous full-duplex too, allowing one wireless node to start receiving a signal while transmitting another. Asynchronous transmission is important for carriers wishing to maximize traffic on their networks, and Rice's team is the first to demonstrate the technology.