DTS: More or Less, What’s Your Guess?
The Federal Communications Commission ("FCC") has issued a Notice of Proposed Rulemaking looking toward relaxing restrictions on Distributed Antenna Systems ("DTS") for full-power television stations and making DTS newly available to Class A and Lower Power Television ("LPTV") stations.
With DTS, a TV station installs multiple transmitters at separate sites. Each transmitter operates on the same channel, and all broadcast the same content, at least when using the current ATSC 1.0 TV technical standard. There will be opportunities for varying the content to some extent to provide hyper-local services to small geographic areas after stations convert to the new ATSC 3.0 standard (known as "NextGen"). The advantage of DTS is that it evens out signal strength throughout a station's service area and can eliminate pockets of poor reception. In the digital world, a system of multiple transmitters operating on the same frequency is called a single frequency network ("SFN").
Translators can achieve a similar result in terms of evening out signal strength, but each translator operates on a different channel from the parent station. DTS eliminates the need to find a separate channel for each translator and to coordinate PSIP information on multiple channels to facilitate convenient viewer reception.
The existing rules require that the signal from each DTS transmitter be confined to within the 41 dBu service of the primary station. That requirement makes it difficult to locate a DTS transmitter near the fringe of a station's service area, because the signal is likely to spill beyond the 41 dBu contour limit. This problem can be minimized by using a directional antenna to aim the signal back inside the parent station's area, but that approach can impair the ability of the DTS signal to fill the reception gap it was intended to eliminate. Responding to a rulemaking petition by America's Public Television Stations ("APTS") and the National Association of Broadcasters ("NAB"), the FCC has now proposed that while DTS transmitter sites would still have to be located within the primary station's 41 dBu transmitter, the signals from DTS transmitters would be allowed to extend to the 36 dBu contour of the primary station.
The existing rules also allow only full-power TV stations to construct and operate DTS on a regular licensed basis. An application must be filed and approved before implementing DTS. When the FCC first approved DTS in 2008, it said that the record was not yet sufficient to justify authorizing DTS for Class A and LPTV stations. The new proceeding looks toward removing the Class A/LPTV roadblock. Without removal of the roadblock, two or more commonly owned Class A or LPTV stations with overlapping service contours may operate under the existing rules as a multi-frequency network ("MFN") that functions similarly to DTS, except that each channel has only one transmitter. If the new rules are adopted, Class A and LPTV stations will be able to operate multiple transmitters on a single channel as an SFN.
To date, the FCC has not proposed to allow broadcasters to operate a network comprised of only small distributed transmitters, with no central large main transmitter.
The rulemaking proposals raise several issues, which have already generated some questions, if not outright opposition, from parties other than APTS and NAB. Despite a study by APTS and NAB that says that the impact will be very small, Class A and LPTV licensees have noted that pushing the DTS coverage limit out to the 36 dBu contour will generate more interference to their stations that operate co-channel or first-adjacent at the fringe of a full-power station's service area. The Noting that it does not intend expanded DTS to increase the amount of interference protection that stations enjoy, the FCC has suggested that if a DTS configuration causes interference outside the primary station's protected signal contour, the DTS licensee should be responsible for curing the problem, even if the DTS station is full power, and the victim is an LPTV station; but if interference is increased within the primary station's currently protected contour, a full power DTS licensee's signal will remain primary over LPTV and other secondary services.
While expanding DTS signal areas could threaten some LPTV stations, the other side of the coin is that LPTV stations might benefit if full power stations implemented DTS in place of, rather than in addition to, some of the fill-in translators they now operate. If fill-in translators are shut down, more channels should be freed up for use by LPTV stations that currently suffer from large amounts of incoming interference. The FCC has not proposed to require shutdown of fill-in translators as a condition of receiving expanded DTS authority.
Meanwhile, the FCC has asked for comments on which technology will better advance localism: variable content on full power DTS transmitters under ATSC 3.0 or preserving channels for LPTV stations serving smaller communities within a DMA. It has also asked whether relaxing DTS restrictions might hasten the deployment of ATSC 3.0 and specifically whether more DTS combined with ATSC 3.0 might promote the provision of advanced data services to the public, a goal that appears to be near and dear to at least some of the Commissioners.
Users of wireless microphones, which are permitted to operate on TV channels on a secondary, non-interference basis, fear being squeezed off of channels they are now able to use. Microphone systems have already been pushed into smaller and smaller spectrum space by the reduction of the TV broadcast band from Channels 2-51 to Channels 2-38. It is becoming very difficult to accommodate microphones at large venues, like sports arenas, theaters, and major events of all kinds.
Proponents of expanded "White Spaces" operation of wireless data systems on vacant TV channels are also concerned about expanding the service of TV stations, which led Microsoft to raise its eyebrows when APTS and NAB filed their rulemaking petition.
The filing deadlines for comments and reply comments on the new DTS proposals will be announced with the proposals are published in the Federal Register. Watch CommLawBlog for a post when publication occurs.