Researchers promise doubled wireless spectrum efficiency
November 19, 2012
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 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
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.
UpdateThis 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