TV white spaces: New frontier could be especially helpful in rural areas
In wireless communications, spectrum inherently is the lifeblood of operations. Without spectrum, all the technology in the world is worthless in terms of establishing and maintaining a wireless network.
This reality makes last week’s launch of the first network operating on the unused frequencies between active TV channels, known as TV white spaces, in the small town of Claudville, Va., extremely notable. U.S. Rep. Rick Boucher (D-Va.) — chairman of the House subcommittee on communications, technology and the Internet — called the deployment a “milestone” in rural broadband deployment.
Currently, no rules have been established for the TV white spaces. Because the TV channels that are used vary from location to location, that means the available white spaces also differ between geographic regions. This makes the spectrum less attractive to auction as licensed airwaves.
But the biggest push — helped by the lobbying efforts of large companies such as Dell, Google and Microsoft — is to have the TV white spaces designated for unlicensed use.
Having unlicensed spectrum is not unusual, but the most popular unlicensed bands currently are at 2.4 GHz and 5 GHz — frequencies that are so high that signals using the spectrum have very limited range, so a lot of wireless network nodes are needed to provide any sort of wide-area coverage.
Few are as familiar with this as the team at online spectrum marketplace Spectrum Bridge. In their last venture before Spectrum Bridge, the group created a company called MeshNetworks that eventually was purchased by Motorola. The reality of dealing with the 2.4 GHz unlicensed band meant that it was “not unusual” for MeshNetworks to deploy 40 to 60 network nodes to cover a single square mile, said Rick Rotondo, vice president of marketing for Spectrum Bridge.
The number of nodes needed to cover a square mile in town with the terrain and tree cover that Claudville has would be even greater, Rotondo said. However, given the excellent propagation characteristics of TV white spaces spectrum below 700 MHz, one transmitter is able to provide almost 8 square miles of “rock solid” coverage in Claudville.
Another advantage of TV white spaces is that equipment for the spectrum is plentiful, because the television industry is so mature. Often, getting equipment that will operate in a “new” spectrum band with an experimental license requires development time and an assurance that the prototype equipment may not operate at a high level of efficiency. That was not the case in Claudville, where Spectrum Bridge is using a high-gain TV antenna designed specifically for the VHF frequencies used in the network to receive signals, Rotondo said.
“These things are optimized to within an inch of their lives, and they’re a dime a dozen,” he said.
Thanks to the availability of a prototype white-spaces radio from Koos Technical Services, the Claudville project was transformed from an idea proposed on a phone call to last week’s network launch in three months — and the total equipment cost was less than $5,000, Rotondo said.
As with most things in wireless communications, using white-spaces spectrum is not a silver bullet that will solve all the industry’s ills. In urban areas, there are so many TV stations that there is little available spectrum between channels to use. And even in Claudville, Rotondo said there was white-spaces spectrum that was available “on paper” that proved to be less than ideal for broadband services, because of interference from TV stations.
From a public-safety perspective, using unlicensed spectrum for mission-critical communications would not be a first choice. But many rural communities can’t afford licensed data solutions, and — unlike urban areas, where network congestion on unlicensed spectrum is a concern — they typically have more than TV white-spaces spectrum available than they would ever use, so white-spaces radios should be able to find a good channel to use without much problem. And having more network options is always a good thing for first responders, because you never know which one will survive the crisis of the day.
And developing radios that can find good channels in an unlicensed band promises to put a step closer to realizing the potential of cognitive radio. In fact, many industry experts have advocated using the TV white spaces as a commercial testbed for cognitive technologies being developed today for the military.
Meanwhile, if the FCC opts to designate the TV white spaces for unlicensed use, the Claudville model could prove attractive for a lot of rural communities — free spectrum, low-cost equipment and few sites to deploy and maintain. For policymakers looking for a way to bring broadband to citizens, businesses and first responders, proper usage of the TV white spaces could be a key piece to solving the puzzle.