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Researchers promise doubled wireless spectrum efficiency


November 19, 2012

Researchers believe they have cracked the code of spectrum efficiency (tower: Shutterstock, traffic: Shutterstock)

Researchers believe they have cracked the code of spectrum efficiency (tower: Shutterstock, traffic: Shutterstock)

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Wireless carriers love to talk about a Spectrum Crunch. Like oil, wireless spectrum is a finite resource. Companies like AT&T; warn that smartphone proliferation is eventually going to leave those "wells" dry. Carriers' answers to the problem usually involve government (less regulations, and more federally-owned spectrum released). However, researchers at U.C. Riverside have another solution: make those networks more efficient.

Though your smartphone is typically described as a full duplex device, meaning that it can handle incoming and outgoing data simultaneously, the two streams (i.e. what you hear and what you say during a voice call) require separate frequency bands. It's like a two-lane highway, where each lane takes up valuable spectrum.

But Professors Yingbo Hua and Ping Liang believe they have cracked the code of true full-duplex transmission on a single channel, so upstream and downstream would live together in one frequency band. This magical two-lane highway would only use one lane.

The secret sauce

The researchers believe the secret is "time-domain transmit beamforming" (Shutterstock)

The Riverside professors were hardly the first to imagine full-duplex transmissions, but there was always a big problem. Uploads and downloads in the same frequency band would cause interference. Hua's and Liang's solution is "time-domain transmit beamforming." As they explain, "[Time-domain transmit beamforming] digitally creates a time-domain cancellation signal, couples it to the radio frequency frontend to allow the radio to hear much weaker incoming signals while transmitting strong outgoing signals at the same frequency and same time."

This means that incoming signals would no longer be overpowered by outgoing signals. Radios would have something akin to "Spidey Sense." They would pick up those fleeting incoming signals, while still broadcasting powerful outgoing signals.

Since it's all taking place in one "lane of traffic" (frequency band), wireless efficiency would be doubled. It's like telling Verizon, O2, and Telstra that they just doubled their spectrum holdings. Such a breakthrough would be worth billions upon billions of dollars.

It's all academic

Have Yingbo Hua (left) and Ping Liang solved the "spectrum crunch?"

There is, however, a big difference between academic theory and proven implementation. Right now, time-domain transmit beamforming is the former. But the Riverside team insists that its theories are sound. Unsurprisingly, big companies are paying attention: the researchers "have had discussions" with several wireless telecom equipment businesses.

Will this be a spectrum breakthrough? It's too early to say, but any progress on this front is promising. As mobile data becomes a more integral part of our lives, increasing its efficiency is good news for customers. Our bills won't likely go down, but it would be one less excuse for them to go up.


This article was amended on November 20. It previous described smartphones, and their means of communication, as half-duplex, which is potentially confusing.

Source: UCR Today

About the Author
Will Shanklin Will Shanklin is Gizmag's Mobile Tech Editor, and has been part of the team since 2012. Before finding a home at Gizmag, he had stints at a number of other sites, including Android Central, Geek and the Huffington Post. Will has a Master's degree from U.C. Irvine and a Bachelor's from West Virginia University. He currently lives in New Mexico with his wife, Jessica. All articles by Will Shanklin

Just combining this with packet compression will make wireless capacity explode.

Joel Detrow

Don't want to sound like a pedant, but .....

Half duplex is where both ends take it in turns to transmit and receive on the same channel.

What you were referring to with Smartphones is full duplex, with separate channels to send and receive simultaneously.




2 sep channels is not, repeat not duplex. It is freq shift, and it acts much like...but it is not.

Walt Stawicki

Full duplex is an over-simplification of the method: signaling must allow for transit times which results in wasted time intervals. This method appears to start transmitting while continuing to receive due to the differences in time-skew. A simple explanation is that it fills the channel more fully in the time domain. The results might vary depending on distance and other signaling conditions that vary interference and timing conditions.

Nonetheless, any approach that starts out with the promise of 'duplex vs. simplex' doubling of capacity that has what appears to be solid credentials is exciting. Perhaps this will prove to be useful in some but not all signal conditions and perhaps will have limitations in what network and user device applications it is used, however, the benefits are fundamental such that the benefits may be multiplied through multiple channels and architectural methods.

At a point in wireless development were link spectral efficiencies have reached near practical Shannon limits and most gains are from use of higher order modulation and MIMO-AAS, this has potential to result in significant improvement in performance once it winds its way into adoption.

Robert Syputa

The need for spectrum capacity improvements is fo orders-of-magnitude, ten times in the next five years and 100 times in ten years. Smart antenna techniques, like SDMA (Spatial Division Multiple Access), are field proven and not yet used by LTE operators even though LTE can accommodate them. Every possible approach needs to be researched and implemented if society is to garner all of the benefits of wireless. re-distributing spectrum is not the answer. More pressure on new technology adoption is.

Martin Cooper
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