10/5/10

"White Space Broadband" - Good For The Internet, Potentially Bad For Your Wireless Microphones

tap-tap... Is this thing on??
Way back in the day, I was a techie-librarian at Oklahoma City University School of Law. One of the list servs that I frequently monitored (and still monitor today) is the Technoids list serv which discusses technology issues that law school technology workers face. Last week, an interesting post came in from Ryan Overdorf from the University of Toledo College of Law that identified a potential problem concerning the FCC's approval of using televisions "white spaces" as broadband Internet access and wireless the microphones used in law school classrooms. For those of us in law firms, some of us use these same wireless mics in our conference rooms, training rooms, or trial prep courtrooms. Rather than try to interpret Ryan's evaluation of the problem, I just asked that he guest post today and relay the message directly.

Guest Blogger - Ryan S. Overdorf 

The FCC has finally opened up the TV white spaces.  The new Television Band Devices (TVBDs) hold the promise of providing improved high-speed broadband access at reduced cost.   For wireless microphone users who must share those white spaces, however, these benefits do not come without challenges. The FCC eliminated the proposed "spectrum sensing" regulation that would have required TVBDs to avoid TV channels where wireless microphones were actively operating.

Wireless microphones will be protected from interference by TVBDs only in channels specifically reserved for their use. The first vacant TV channel above and below channel 37 is reserved for wireless microphones nationwide. In some markets and under some circumstances vacant TV channels from 14-20 are also reserved for wireless microphones.

Manufacturers and vendors have been selling microphone systems operating on unreserved channels because they thought the regulations were going to include spectrum sensing. If you use wireless microphones operating on those channels, your options for mitigating the interference risk are limited. You can increase the microphone squelch in an attempt to suppress the TVBD signal. TVBD users may be able to select specific channels, and you could specify certain channels to avoid. You could also ask TVBD users to shut down their devices when your wireless microphones are in operation.

It is possible that all of these measures would fail. A TVBD signal may be too strong to be squelched. A TVBD signal may extend too far to make either specifying channel selection or requiring device shutdowns a practical solution. No one will know for sure until TVBDs come on the market and begin competing with wireless microphones for vacant TV channels.

If you use wireless microphones, the first step is to determine the channels of operation for your microphones. Consult your manufacturer's manual. Some manuals list specific TV channels and frequencies while others list only the frequencies. The FCC lists each TV channel and its associated frequency in 47 C.F.R. § 73.603(a) [PDF].

For more information, see the "Changing Channels: TV Spectrum for Wireless Microphones and Wireless Broadband" web page.



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