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NEWS

Proposal: let license-free broadband use the FM radio band in subways

From "A most unusual FCC proceeding concerning the future of the white spaces in the FM radio band," by Jim Snyder, Truth, Justice, and Telecom Policy, 18 September 2006:

"I am writing to alert you to a most unusual FCC proceeding (ET Docket 06-161) concerning the future of the white spaces in the FM radio band. The Rail Network, with the apparent backing of many major mass transit systems throughout the United States, has petitioned the FCC to enhance the Part 15 (unlicensed) rules [to allow license-free use of unassigned channels in the 88-108 MHz FM audio broadcasting band] within subways...

"The current rules [for that band] only allow for Part 15 transmissions less than ten feet in distance... In practice, many of these devices can only send a clear signal several feet... The Rail Network says the Part 15 device will be at the front of each subway car and point to the back. The design will result in minimal energy emitted outside the subway car. When subways are underground, there will be no possible outside interference because FM radio signals are not available underground. Moreover, when cars are above ground, there will only be very brief interference even to a radio that happened to be immediately adjacent to a subway car because subway cars are constantly moving.

"Given today's political environment, the Rail Network's most compelling public interest argument for its proposed Part 15 modification is public safety. Rail passengers currently have minimal access to radio broadcast news in the event of a natural disaster or terrorist attack. The attacks on mass transit in London and Spain are specifically mentioned...

"The day-to-day programming Rail Networks plans to put on such spectrum remains unclear and may amount to little more than the type of programming available in many doctors' offices or airport lounges.

"The Rail Network previously received a waiver to provide such service in Atlanta, Georgia, where it already has a system up and running. Now it wants to be able to compete for requests for proposals for audio/video information systems from mass transit authorities throughout the United States...

"I'm inclined to support Rail Network's basic proposal for higher power Part 15 devices, especially when passengers are traveling underground. In several respects, I'd also suggest going well beyond Rail Network's proposal. Rail Network only plans to provide service on the unused channels within the FM band. But I don't see why when a subway was underground it couldn't use the entire [30] MHz allocated to the FM band. All that spectrum is currently lying fallow and this would put it to a good use.

"I'd also consider using the spectrum for broadband rather than broadcast service. Given its excellent propagation characteristics, the FM band could be excellent backhaul spectrum in an underground setting. In this application, the spectrum would link subway cars to the Internet backbone. The end user would then access this backbone via unlicensed spectrum using devices such as a WiFi enabled laptop or dual mode mobile telephone. Alternatively, unlicensed devices developed to use the unused spectrum in the TV band could be adapted to use the unused spectrum in the FM band as well. The FM band is located between TV channels 6 and 7. The incremental cost of adding FM band access to the next generation of unlicensed devices should be negligible.

"Of course, the broadcasters will scream bloody murder at Rail Network's proposal, so I assess its chances of success as very slim. Broadcasters, after all, have their own schemes for utilizing subway and other currently underutilized spectrum within the radio band... Giving incumbent broadcasters all the white spaces will surely come at an opportunity cost. This type of proceeding gives us a sense of what that opportunity cost might be..."

[Unlicensed Wireless: 25 September 2006]