It’s good to see researchers exploring ways to get more use out of existing spectrum, now that mobile and Wi-Fi data usage is climbing steeply. Some particularly interesting activity has occurred at Rice University, where researchers say that for the first time ever they have successfully demonstrated a wireless system that transmits data over “TV white spaces” without interfering with active television broadcasts.
Dubbed WATCH (Wi-Fi in Active TV Channels), the technology that the Rice researchers developed is designed to support high-speed Wi-Fi-like wireless data networks.
Rice researchers received FCC approval to demonstrate WATCH on the Rice campus in 2014. Boiled down to its essentials, WATCH actively monitors TV signals across UHF spectrum and makes use of signal-canceling techniques to insert wireless data signals into the same channel. Doing so effectively negates TV signals’ interference with them, Rice News’ reporter Jade Boyd explained.
The other essential facet of WATCH would require technology in smart TV sets or remote control devices to report when TVs are tuning into specific UHF channels. The researchers developed a smart remote app that accomplishes this. Using the app with a test TV set in the lab, the WATCH system automatically shifted its UHF transmissions to an alternate unused UHF channel.
WATCH also proved to be much more efficient at transmitting wireless data. “Our tests showed that WATCH could provide at least six times more wireless data compared with situations where we were limited only to the traditionally available white-space spectrum,” lead researcher Edward Knightly told Boyd. Knightly is a Rice professor and chair of electrical and computer engineering as well as director the Rice Wireless Group.
Tuning into a UHF TV broadcast on the lab’s test TV set took only a fraction of a second longer than normal, Knightly said. That’s less than a 5 percent increase, a time span that’s practically imperceptible to viewers, he added.
Why WATCH Could be Needed
Ranging from 400-700 megahertz (MHz), the UHF frequency band is well suited for wireless data transmission. Demand for mobile data is forecast to grow some 10-fold in just five years’ time, Rice researchers note.
Yet at the same time, UHF spectrum is some of the most underutilized, Knightly was quoted as saying. Market research firm Nielsen found that less than 10 percent of U.S. households rely on over-the-air broadcasts for TV programming, the Rice research team points out.
The FCC strictly regulates the use of UHF spectrum for wireless data transmission given its potential to interfere with broadcast, cable and satellite TV transmissions. As a result, UHF spectrum will continue to be underutilized – unless someone invents or discovers a means to eliminate the interference, that is. That’s what the Rice U. research said it has done.
Knightly pointed out that because they operate at lower frequencies than those used to transmit data to and from Wi-Fi hotspots, UHF signals can travel for miles. Walls or trees that would block Wi-Fi signals don’t pose obstacles for UHF signals, moreover. Hence wireless networking operating in the 400-700 MHz band is frequently called “super Wi-Fi.”
“Unfortunately, in the most densely populated areas of the country, where the need for additional wireless data services is the greatest, the amount of available white space is extremely limited,” Knightly noted. “In our most recent tests in Houston, one channel is open in parts of the city and none are available in others. This is fairly typical of a large U.S. urban area.”
“Allowing the UHF spectrum to be inefficiently used makes little sense today and will make even less sense in the future,” Knightly stated. “There are already more people in the United States who require mobile data services than there are people using broadcast-only TV. By showing that these two communities can coexist, we hope to spur innovation and a public debate about how this valuable resource could be used.”