The Federal Communications Commission is expected this fall to implement a database designed to prevent interference between wireless devices’ use of “white spaces” and digital television broadcasts.
The database would monitor and track usage of white spaces—the broadcast frequencies between those used by digital television broadcasters—and would theoretically work with other equipment to allow the use of the currently unused spectrum.
This could enable creation of wireless hotspots with far greater range and coverage than today’s wi-fi networks.
Proponents of such unlicensed wireless availability include computer and tech companies such as Google, Microsoft, Dell, and HP, while the broadcast industry is still expressing concerns about potential interference white space devices could impose on digital programming.
Interference Concerns
Part of the FCC’s agreement to allow the use of white spaces initially included the formation of a central geo-location database of licensed-spectrum use by broadcasters around the country. Such a database allegedly would mitigate potential interference between unlicensed spectrum use and licensed broadcasts; for example, white space network access on a smartphone would have no effect on nearby digital television broadcasts.
Technology employing the UHF/VHF frequency bands would enable creation of wi-fi hotspots in some places with several times the coverage area of what one would typically find in a coffee shop or restaurant, according to Peter Stanforth, chief technology officer of Spectrum Bridge in Orlando, Florida.
To access wi-fi transmissions in this space, wireless users would need new wireless adapters not yet on the market.
Since 2008 the FCC has been working on details of rules to allow the use of this white space, Stanforth says. The problem is how to enable use of the unused spectrum without interfering with already licensed spectrum.
Technical Details
Many of the technical details regarding how to ensure against interference are still to be worked out, agreed Rich Noonan, a wireless network system engineer at Cellular Specialties in Manchester, New Hampshire. “The big challenge is with unlicensed equipment to avoid interfering with licensed users. So systems will appear in more rural areas first [due to lower chance of interference]. But the areas with the most demand are urban areas. In those areas, the frequency management protocols have to be worked out.”
Noonan said some of the technical problems can be solved by allowing some short delays during unlicensed use of the white-space spectrum to ensure licensed users take precedence when necessary. These delays of several seconds are acceptable and somewhat commonplace in machine-to-machine communications but are unlikely to be tolerated for traditional phone calls.
As equipment becomes better at sorting out spectrum, these delays would become less frequent, Noonan says. Even so, Stanforth expects it will be nearly two years before all the necessary equipment is available in the market to take advantage of these larger wi-fi hotspots in the white spaces.
In the meantime, there could be other uses for the spectrum. In mid-September, Spectrum Bridge launched a broadband trial network for telemedicine applications in Logan, Ohio, along with partners Google and Hocking Valley Community Hospital.
Phil Britt ([email protected]) writes from South Holland, Illinois.
