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TV Would Lose 120 MHz in National Broadband Plan

The FCC's National Broadband Plan (NBP) [PDF], delivered to Congress on Tuesday makes the case for an additional 500 MHz of spectrum needed for wireless broadband, and an additional 300 MHz of new spectrum for broadband within five years. As expected, much of this is expected to come from the UHF TV band.

The NBP's Recommendation 5.8.5 makes this clear.

"The FCC should initiate a rule-making proceeding to reallocate 120 MHz from the broadcast (TV) bands..."

In the plan, the FCC proposes several ways to clear this 120 MHz (20 television channels). The first is to create a new DTV Table of Allotments with different service areas and distance separations that would allow stations to operate on the same or adjacent channels with spacing that is currently prohibited, without increasing interference levels unacceptably.

One way they might do this would be to set the protected service area of a station at a higher signal level, perhaps by using the 48 dBµV/m community grade signal level instead of the current 41 dBµV/m signal level. Another way would be to allow greater amounts of interference between stations.

The NBP says this could clear 36 MHz of spectrum; however, clearing this spectrum will require some stations to change channels and replace their antennas, and possibly their entire transmission plants should they be relocated to a VHF channel. If this 36 MHz comes from the top end of the UHF TV band, as the NBP implies, it would mean that stations currently operating above Channel 45 would have to move.

With the 120 MHz reduction, the overall television band would be reduced to just 30 channels—only 2 through 31 would remain.

The FCC recommends the use of auctions and channel sharing to obtain the final 84 MHz of TV spectrum. To provide stations with an incentive for giving up spectrum, the commission proposes that Congress allow broadcasters to share part of the auction revenue, or to require the auction winner to pay incumbent licensees. Stations could give up all their spectrum and go silent, perhaps existing as cable-only operations, or they could join together and share a single 6 MHz channel.

While TV channels must be 6 MHz wide to comply with the ATSC standard for reception on current DTV sets, the 19.39 Mbps in that 6 MHz channel could be shared among multiple stations. In the NBP, the FCC points out that in some markets a single station transmits two networks on one channel, and some stations even run two HDTV programs on one channel. From what I've seen, while it's possible to run two simple HDTV signals (such as upconverted sitcoms and dramas, old movies, and some news) within 19.39 Mbps by using the latest generation encoders, it's not possible to run two high-quality, high-motion, complex content (such as sports programming) in less than 10 Mbps without noticeable and objectionable degradation.

Delivering multiple program streams to a common multiplexer and transmitter site from different studio locations isn't a trivial task, as statistical multiplexing would be needed to make the best use of the limited bandwidth and this requires two-way communication between the multiplexer and the various encoders. Determining who has priority to the bandwidth could also be an issue.

All stations could benefit if they share bandwidth, but they may not want to risk losing bandwidth should one or more of them be running complex and bandwidth-hungry programming.

If the auction value of the spectrum is high, I expect some stations would be happy to share one 19.39 Mbps channel and pocket the cash. Throughout the NBP, the FCC refers to cost per "MHz–Pop."

The value of a channel would be based on the number of people it could cover if used for broadband purposes, not the value of the TV broadcasting business. This means a Class-A LPTV or small full power station running infomercials could be worth as much as a full-power network affiliate. As a result, the MHz–Pop price will probably end up at a level below that necessary to entice a major network affiliate to give up spectrum, but it could be very attractive to broadcasters with smaller revenue streams, especially if they could consolidate their SD programming on a channel with other broadcasters.

If the repacking, auctions, and channel-sharing don't provide the 20 channels needed for broadband, the NBP lists additional options, none of which are very attractive.

These include: a transition to a cellular architecture on a voluntary or involuntary basis (I've previously described the technical challenges and high costs of such an approach), an auction of overlay licenses—with wireless carriers being given secondary rights to the spectrum and having to negotiate with TV broadcasters to clear the channels, license modification requiring stations to share a single channel, and "other innovative solutions that may emerge."

The FCC says that stations would not receive any portion of auction proceeds under these alternative solutions, but "should receive reimbursement from auction winners for any relocation or other transition expenses incurred."

As I mentioned earlier, elimination of TV channels above 31 would force many stations into the VHF band. The NBP recognizes this and adds as an additional measure to increase TV spectrum efficiency, the FCC would need to pursue "additional options" for dealing with VHF reception problems. These options might include power increases or "adoption of enhanced antenna and receiver standards."

The document notes, that without such measures, "VHF stations may continue to request channel reassignments to the UHF band, complicating efforts to reallocate spectrum from that band to mobile broadband use."

Other options could include spectrum fees for full-power TV broadcasters, establishing a deadline for LPTV stations to convert to digital, more efficient LPTV channel allocations, and allowing LPTV stations to participate in incentive auctions.

The FCC recognizes that reducing the UHF TV spectrum will also impact land-mobile radio systems that currently share television Channels 14-20 in some of the larger markets, along with wireless microphones and TV white space devices. The FCC proposes continuing to allow land-mobile users to operate under existing licenses, thus increasing the spectrum crunch on broadcasters in the major markets.

Readers should remember that the National Broadband Plan is just that, a plan. Before its provisions can become law, they will have to go through the FCC's process of proposed rule-makings, public comments and orders. Some of the actions will require Congress to change laws.

This is a critical time for free off-air broadcasting. The NBP makes the assumption that broadcast TV has declining value and serves only a small percentage of the population. However, antenna manufacturers are reporting record sales, and I've heard comments that the number of off-air viewers—including homes receiving only off-air television—may be starting to increase.

If you value the concept of television broadcasting and are looking forward to using the new ATSC Mobile DTV devices that are due out later this year, you must let your representatives in Congress know. Thanks to the Internet, this isn't that difficult; however, mailed paper comments may carry more weight.

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.