Full-duplex radio breakthrough can double Wi-Fi capacity

Stanford University researchers have found a way to double the capacity of wireless networks, while at the same time making them more reliable and efficient.

In pictures: What's hot at Mobile World Congress 2011

Their discovery supports full-duplex connections - allowing data to be transmitted between devices in both directions at the same time rather than in just one direction as has been the case until now, the researchers say. Both Wi-Fi and cellular networks could benefit.

The speed in either direction remains the same, however. So if a wireless network has a speed of 15Mbps, that doesn't change with the new technology, it just opens up the channel so both ends can send and receive at 15Mbps simultaneously. With current technology, one side sends then waits while the transmitter at the other end takes its turn.

"This technology breaks a fundamental assumption about the way wireless networks work," says Philip Levis, an assistant professor of computer science and electrical engineering at Stanford, one of the leaders of the research.

Equipment initially used to demonstrate this new capability has been refined so it requires two rather than three antennas, and details of this upgrade will be made public in a paper next month. This summer, the researchers will look into making commercial products based on their research, he says.

Using a cancellation technique, the researchers make it possible both parties in a wireless conversation can talk at the same time without drowning each other out. This can help reduce the number of failed connections on Wi-Fi networks that are dense and busy, researchers say.

Until now, the volume of a transmitted radio message overpowered the relatively weak incoming signal from the radio at the other end. Or as the researchers put it, "when a node transmits, its own signal is millions of times stronger than other signals it might hear: the node is trying to hear a whisper while shouting."

Technology developed at Stanford cancels out the signal created by sending machines so they can pick up the relatively quiet transmissions coming at them.

That assumption was that if both ends of a radio connection spoke at once, the signals being received would be obscured. The traditional way around the problem is to have radios communicating on the same frequency take turns transmitting so the outgoing signal doesn't interfere with the incoming. That's why people carrying on a conversation over wireless say, "Over," when they are done talking so there is no overlap.

Most of the time this isn't a problem in Wi-Fi networks because conversations take place between access points and individual end-user devices with little likelihood of simultaneous transmissions, Levis says. But in crowded environments, such simultaneous transmissions do occur and none succeeds.

With full-duplex transmissions enabled, when an access point starts to receive from an end device, it can immediately send a message back saying it is busy so other end devices in the area know not to transmit, Levis says.

In cellular networks where carriers use repeaters to extend the range of base stations, this technology could be used to make transmitting boosted signals from cell phones to base stations and base stations to cell phones more efficient.

The researchers' design uses two transmitting antennas, one receiving antenna at each node. Both transmitting antennas send the same data, but the receiving antenna is placed so it receives signals from the transmitting antennas that are out of phase so they cancel out. The result is there is no signal - or at least a very reduced signal - for the receiving antenna to receive.

Read more about anti-malware in Network World's Anti-malware section.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.

Tags wirelessNetworkingWi-FiStanford UniversityWLANs / Wi-Fi

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Tim Greene

Network World
Show Comments

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Tom Sellers

MSI P65

This smart laptop was enjoyable to use and great to work on – creating content was super simple.

Lolita Wang

MSI GT76

It really doesn’t get more “gaming laptop” than this.

Jack Jeffries

MSI GS75

As the Maserati or BMW of laptops, it would fit perfectly in the hands of a professional needing firepower under the hood, sophistication and class on the surface, and gaming prowess (sports mode if you will) in between.

Taylor Carr

MSI PS63

The MSI PS63 is an amazing laptop and I would definitely consider buying one in the future.

Christopher Low

Brother RJ-4230B

This small mobile printer is exactly what I need for invoicing and other jobs such as sending fellow tradesman details or step-by-step instructions that I can easily print off from my phone or the Web.

Aysha Strobbe

Microsoft Office 365/HP Spectre x360

Microsoft Office continues to make a student’s life that little bit easier by offering reliable, easy to use, time-saving functionality, while continuing to develop new features that further enhance what is already a formidable collection of applications

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?