Commission must boost protection from unlicensed TV band device interference, says SBE
May 27, 2009 9:51 AM, By Phil Kurz
The FCC must do more to protect wireless microphone operation — a critical component of electronic newsgathering (ENG) — from harmful interference generated by unlicensed TV band devices, the Society of Broadcast Engineers (SBE) told the commission in reply comments (pdf) filed May 18.
The comments are the latest twist in FCC proceedings aimed at authorizing the use of unlicensed transmitting devices in TV spectrum not used by TV stations. In them, the society addressed various “broader concepts that should trouble the commission” regarding the case of fixed white space device backers.
The SBE argued in the comments that the commission cannot move forward with its proceeding based on the notion that unlicensed TV band devices should be allowed in the TV spectrum unless incumbent licensees show that there will be interference. Rather, the commission “must proceed carefully” to make sure interference to broadcast and broadcast auxiliary services will not occur.
In its comments, the SBE argued that the commission has a track record of proceeding with the utmost care to protect incumbent spectrum users before authorizing new services in the same band. The society pointed to the commission’s actions in authorizing ultra-wideband transmission systems as well as its decision not to ease restrictions on unlicensed device power levels when it revised its Part 15 rules in 1989 as two examples.
Another broad concept in the crosshairs of the SBE is the conceptual error found in comments from the Public Interest Spectrum Coalition (PISC), as well as Dell and Microsoft, that “wireless microphones are due less interference protection” than that given in the commission’s Second Report and Order in the proceeding.
The filing laid out the case that the concept of a protection zone for wireless mics into which high-powered TV band devices could not be used — something both PISC and Dell and Microsoft favor — is flawed. This notion is “based on a complete misunderstanding of the means by which broadcast auxiliary spectrum is utilized,” the filing said. “Wireless microphones are deployed by broadcasters on a ubiquitous, itinerant basis. They are not used in any narrow geographic range,” the SBE comments said. Because of the itinerant nature of news, a 1km “protection zone” for registered wireless mics as an effective means of protecting wireless mics from TV band device interference is “a fiction.”
"The proponents of TV band devices have failed to deal with the fact that what they are attempting to justify is mobile, itinerant sharing between a licensed service that by definition must have spectrum priority and an unlicensed technology with no allocation status and no entitlements to operate whatsoever, except on an at-sufferance basis,” according to the filing.
The SBE filing also addressed the hotly contended issue of spectrum-sensing technology intended to prevent TV band devices from operating on spectrum in use by TV stations and wireless mics. In a previously filing, the SBE suggested sensing technologies “should be able to monitor levels lower than -114dBm.”
In its most recent filing, the society flatly stated, “spectrum sensing does not work,” and “if it is to be used as a placebo in order to attempt to justify adding an incompatible unlicensed service atop licensed broadcast and broadcast auxiliary services in the same spectrum,” rules must be in place “that make some technical sense.”
Calling the -114dBm threshold “inadequate and arbitrarily determined by the commission,” the SBE said under no circumstances should it be reduced, but rather must be increased.
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