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Special Report: Wireless Interference Protections

An update on TVBD rules and geo-location database operations

Rules for the operation of Television Band Devices (TVBD) in the core TV bands (low VHF – channels 2-6; high VHF – channels 7-13; and UHF – channels 14-51) were finalized in January 2010.

One of the requirements of TVBD operations was the establishment of a working and real-time accessible geo-location database from which TVBDs had to receive a list of available TV channels based on the TVBD’s physical location and type.

It’s only as of January 26, 2012 that the first database (Spectrum Bridge) commenced operations after receiving approval from the Federal Communications Commission’s (FCC) Office of Engineering and Technology (OET), the bureau overseeing TVBDs and the databases. The first TVBD was type approved last December (KTS Wireless).

Although several fixed point-to-point and point-to-multipoint TVBD installations have existed for over three years operating under developmental licenses in generally remote areas having quite a bit of available spectrum, it should now be expected to see fixed TVBD installations coming online this year in both rural and suburban environments.

Like the developmental systems, almost all of these first deployments will be in the high VHF channels and in mostly rural areas, though suburban locations should be anticipated.

The reasons are several, and are due to the interleaved matrix of TVBD rules that consider the type of TVBD, as well as its effective radiated RF power (ERP), its height above average terrain (HAAT), its location, and market economics. Given these parameters, the white space community realized some time ago that major urban areas simply don’t have enough spectrum – or any, in some cases – to permit TVBD operations, especially in the UHF band.

In those major urban centers where there is a channel or two for TVBDs to operate in the UHF spectrum (which should not be confused with channels available for wireless microphones, IEMs, coms and queuing), it’s almost always limited to personal/portable devices operating at the lower RF power limit of 40 mW.

The first deployments will be VHF, due primarily to coverage requirements and type of terrain. These systems are for back haul to locations not serviceable by fiber or copper infrastructure. Whether a private data link used to interconnect a remote facility, or the backbone on which a WISP (wireless internet service provider) can deliver internet service to one or more subscriber homes, these deployments are often characterized by distances of many kilometers and partially obstructed line of sight; exactly the conditions best suited for high VHF.

Further, as the broadband nature of DTV transmissions doesn’t work well in VHF (for reasons that do not affect computer networking nearly as severely and why many TV stations have returned to UHF after the DTV transition), this spectrum is now less congested than prior to the transition.

Database Status

The criteria that determines what channels are available to an individual TVBD at a given time and place are calculated in real time by the geo-location databases, of which there are nine provisional and one confirmed. Whereas Spectrum Bridge is the first to be confirmed, the other nine are Airity, Comsearch, Google, LS Telcom, Key Bridge*, Microsoft, Neustar, RadioSoft and Telcordia Technologies (*not a member of the White Space DataBase Administrators workgroup). Telcordia just completed its 45-day live test and appears to be on its way to being confirmed, though the comment period is not yet over as of this writing.

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Each database may use an algorithm of their own design that utilizes the information in the FCC’s Universal Licensing System (ULS) and Media Databases to determine which channels are available to which type of TVBD, but all databases must return identical – and correct as determined by OET – available channels based on the same criteria. So no matter which database operator a wireless mic user chooses to consult, the channels returned will be consistent.

The database administrators are further looking into developing a common user interface for wireless mic users for both the basic channel versus location query and the channel registration screens.

Some databases (at this time Comsearch, Key Bridge and Spectrum Bridge) are considering offering additional information that wireless mic users might find useful at no charge, such as other nearby wireless mic users who’ve reserved channels and displaying the channel availability information in a table format so that one can see what channels are available to what type of device. This can better aid in choosing the best channels (beyond the two reserved) to minimize the chance of interference.

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