The question of whether or not to participate in next year’s broadcast spectrum incentive auctions, and the battle over whether or not there are enough protections in place for broadcasteers, continues to vex our industry. Is it too much to ask for some guarantees? Or at least a bit more fairness on the part of the FCC?

At stake are those stations that could end up being relocated in the “duplex gap,” the portion of spectrum between wireless up- and downlinks. For those broadcasters that have to move channels after the repack, some of them may end up in this portion if the FCC can’t find a channel for them. When the commission made the proposal earlier this year, opposition was swift and fierce. And proof of the potential interference was outlined in the pages of TV Technology by veteran columnist Charlie Rhodes, formerly chief scientist with the ATSC Test Center and who now conducts his own research on interference. Rhodes outlined his concerns in his column, “Assessing Post Channel Repack Options,” and his warnings were summarized in comments filed by Sinclair Broadcasting in September.

“Using the commission’s recently adopted ISIX model [the FCC’s adopted interference model, based on Longley-Rice], Mr. Rhodes cautions that harmful interference will indeed occur and be far greater with the aggregation of ‘super blocks’—10 MHz wide assignments—by wireless carriers,” wrote Mark Aitken, vice president of Advanced Technology for Sinclair. “ISIX interference can arise from signals offset in frequency by more than 6 MHz. In fact, Mr. Rhodes notes that two Super Blocks of 10 MHz each may generate third-order distortion products spanning a significant 27 MHz. In short, broadcast and wireless broadband will demonstrably interfere with each other, and that will be exacerbated by placing broadcast channels in close proximity to wireless users in the duplex gap.”

The NAB, likewise, warned the FCC that placing stations in the gap will limit those stations’ ability to expand their service areas or take advantage of new innovations in broadcast technology. The association also decried the commission’s lack of fairness to stations that decide not to participate in the auctions, hinting that the commission’s latest notice on auction procedures could punish such stations by placing them in the duplex gap, which is also occupied by wireless carriers in other markets.

“For a long time, the FCC had been suggesting that broadcasters would be randomly selected to be placed into the wireless band, and it would not be based on whether, and to what extent, they participated in the auction,” wrote Patrick McFadden, vice president of spectrum policy for NAB in September. “Obviously it would be alarming if the FCC made judgments based on participation.”

“The recent Procedures Public Notice, however, could be read to suggest the FCC has decided that only non-participating stations will be placed in the wireless band, if the auction successfully closes at the initial clearing target,” McFadden said. “In addition, it appears that the only other stations that could be added to that list are broadcasters who participate but drop out in one stage, only to see the auction move on to another stage because it could not close. In other words, if the auction fails to close at that initial stage, the only additional stations that can be relocated to the wireless bands are stations that drop out because their asking price is too high. This doesn’t exactly sound ‘voluntary’ to most broadcasters.”

Despite the “moving target” aspect of the spectrum auctions and pressure from Congress to initiate them to satisfy budget revenue projections, the FCC needs to remember and hold fast to its central core mission: to protect spectrum and manage the airwaves to minimize interference, particularly post repack. Sinclair’s Mark Aitken again:

“Interference protection is the raison d’etre of the FCC,” he, said. “The laws of physics have not changed, and repacking broadcasters in bands reserved for mobile wireless broadband highlights the commission’s challenge.”

We couldn’t agree more. Add to that the results of a recent study by Digital Tech Consulting that predicted that the FCC’s 39-month window may not allow enough time for more than 400 stations to be relocated to new channels and it’s clear that the commission is not doing enough to ensure a methodical transition. Adopting more stringent rules to protect those stations that remain operating after the auction could go a long way in helping to improve their image in the eyes of our industry, and more importantly, protect a valuable public resource.

WASHINGTON—There will more interference than FCC anticipates in the duplex gap. That’s the upshot of a filing on the Federal Communications Commission’s Incentive Auction docket made by Mark Aitken, vice president of Advanced Technology for Sinclair Broadcast Group.

“Interference prevention is the raison d’être of the FCC,” he wrote. “The laws of physics have not changed and repacking broadcasters in bands reserved for mobile wireless broadband highlights the commission’s challenge.”

The commission is proposing to place orphaned TV stations in the duplex gap—the band of spectrum between wireless up- and downlink frequency blocks. Orphaned TV stations will be those not sold in the auction, and that the FCC can’t find a channel for in the TV band after the auction. The FCC is proposing to put these TV stations into the duplex gap, something both broadcasters and wireless providers oppose. The FCC, however, says it needs the flexibility of assigning stations to the duplex gap in order to reach its spectrum-clearing goals.

The impact of doing so remains disputed.

Aitken submitted an article by TV Technology contributor Charles Rhodes, “Assessing Post-Repack Channel Options.” Rhodes was chief scientist at the Advanced Television Test Center, a non-partisan, independent testing facility set up to develop digital TV technology. He is also a recipient of the David Sarnoff Medal and holds several patents. He now conducts signal-interference tests in his own facility and reports the results in TV Technology.

“Using the commission’s recently adopted ISIX model, Mr. Rhodes cautions that harmful interference will indeed occur and be far greater with the aggregation of ‘super blocks’—10 MHz wide assignments—by wireless carriers,” Aitken writes. “ISIX interference can arise from signals offset in frequency by more than 6 MHz. In fact, Mr. Rhodes notes that two Super Blocks of 10 MHz each may generate third-order distortion products spanning a significant 27 MHz. In short, broadcast and wireless broadband will demonstrably interfere with each other and that will be exacerbated by placing broadcast channels in close proximity to wireless users in the duplex gap.”

Aitken also cites a study by the European Broadcasting Union, “Can LTE Share Spectrum With DTT,” which found that cellular long-term evolution transmissions to be incompatible for sharing with direct terrestrial, or broadcast, TV.

The study concludes that terrestrial TV transmitters would have to be between 19 and 56 miles by land from a single LTE base station, depending on its characteristics, to avoid interference from that LTE operation. Given the greater likelihood of several LTE base stations all operating on the same frequency, a distance of between 124 and 184 miles would be needed.

LTE base stations also are vulnerable to interference from digital TV transmitters and would need between 124 and 372 mile of separation, depending on the transmitter.

The EBU study, “which investigated potential sharing of wireless LTE and broadcast spectrum similarly concludes that such sharing is impractical; LTE cannot share spectrum with digital broadcasting,” Aitken said. “These cautionary predictions should inform the commission as it seeks to repack broadcast channels in the duplex gap. Neither broadcasters nor wireless broadband users will find the sharing acceptable.”

Sinclair’s filing comes during the last days of the comment period on a previous commission Notice of Proposed Rulemaking on preserving one UHF channel in the TV band in each market for wireless microphones and unlicensed white-space devices. Opponents of duplex gap placement question potentially kicking a TV station out of the TV band to accommodate an undefined number of wireless mics and the minimal number of white-space devices. Comments are due on the docket Sept. 30.

Joe Snelson

SEATTLE—A Federal Communications Commission request for comment on a proposal to reserve one vacant UHF TV channel in each geographic area of the U.S. for use by unlicensed white space devices and wireless mics has unleashed criticism from an array of television industry organizations.

Joe Snelson, president of the Society of Broadcast Engineers noted that just a few years ago, the commission had issued plans to assign two dedicated channels—in most markets on each side of UHF channel 37—for wireless microphone use. “The ground rules have changed several times from the original two channels,” he said, “and it seems like it keeps moving.”

(As this story went to press for the July issue of TV Technology, SBE had not yet provided formal comments to the NPRM. However, the FCC did suspend the comment period deadline, originally set for Aug. 3.)

In its response to the NPRM (15-146), the Radio Television Digital News Association said that, in television markets where a broadcast station is located on that previously dedicated wireless microphone spectrum, “news operations in that market would be left without assurances that they could cover breaking news to the extent possible in other local markets.

“This approach would run counter to the commission’s [previous] finding that some exclusive 600 MHz spectrum is necessary for licensed wireless microphone operations,” the association continued. “Having already slashed its allocation for wireless microphones by two-thirds down to 4 MHz, the commission cannot feasibly reduce it any further.”

The proposed sharing of spectrum with WSDs has been a particular sticking point in the commission’s proposal. “White space” refers to channels in the television band that are not licensed to broadcasters in a particular television market, but are licensed to broadcasters in other markets. A WSD would determine whether it could operate without interfering with a broadcaster in any particular market by accessing a database detailing which channels are open to WSD use.

A broad coalition of industry associations representing broadcasters and advocates for users of unlicensed wireless WSDs has asked the FCC to reconsider its proposal to prevent the relocation of TV stations to areas of the broadcast spectrum used by such unlicensed devices and wireless microphones. The National Association of Broadcasters is among that group, and has also filed its own comments to the NPRM.

“We’re not against the concept of white spaces,” said Dennis Wharton, executive vice president for communications for NAB. But he pointed to flaws in the WSD database that render it ineffective.

There are fewer than a thousand WSDs that have been sold and are in use at this point. Purchasers of WSDs are not required to obtain licenses to operate them, but must register them with information such as name and address, email address and device location information.

Any review of these submissions quickly turns up intentionally errant submissions. One registrant gave the latitude and longitude a WSD of a spot in the Atlantic Ocean, about 500 miles off the shore of Cameroon. Because there are no TV band licensed broadcasters at that location, the WSD would determine it could operate on any channel, likely causing interference with licensed users. Bogus WSD user information such as John Q. Public, a frequently used 123 Jump Street address and phony email addresses would hinder the ability to contact the owner of an interfering WSD.

“Having geo-location attached to those devices seems to make sense to us,” said Wharton, who also suggested using some system of query and response via email during the WSD registration process.

MULTIPLE DATABASES
Fig. 1: Example of KAET studios wireless microphone protection filing as translated to a point-radius (circle) pattern. On the right is a much smaller resultant protected area. (Demonstration)
The WSD database is actually a group of databases, supplied by multiple vendors, which are required to be synced every 24 hours, at a minimum. Referring to this multiple databased system, Karl Voss, chief engineer at Phoenix public station KAET-TV, said “the biggest thing is they never decided to have one vendor do the database.”

He detailed differences in the way the databases are put together, noting an example that one vendor does not allow describing a licensed user’s WSB protection area as a polygon, even though the FCC’s rules require that polygons be allowed (Figs. 1 and 2). When he entered the information as a polygon, after syncing, “in one database it showed up as a circle.” The circle description would have afforded much less actual protected area when seen by a WSD.

Voss, who is also a frequency coordinator for the National Football League, described another problem with the multiple databases and their need to sync every 24 hours. In the worst case, information entered into database A could take 24 hours to reach database B, and since WSDs are only required to query a database every 24 hours, the combination of the two delays could mean a database entry could take 48 hours to reach a particular WSD.

Fig. 2: Example of KAET studios wireless mic protection filing submitted as a polygon. On the right is the resultant protected area. (Demonstration)
He said in practical terms, in the week before an NFL game “I have been blocking out every frequency known to man at any event that I’m doing, just so the white-space devices are absolutely shut down.”

Such a broad brush approach is necessitated by the last-minute nature of frequency coordination at such events.

“I don’t have any idea until the last moment what wireless microphone or IFB frequency is going to be used by the host broadcaster,” he said. “We may coordinate things a week in advance and then I find out that the vendor shipped different equipment, and then we have to throw away our coordination plan and start all over again with different frequency blocks.”

With all this doom and gloom, it should be noted that white space technology offers “if you can’t beat them, join them” opportunities. “We have been looking at providing WSD equipment that will work in those channels,” said John Payne, chief technology officer at microwave equipment manufacturer IMT. “From the ENG vendor side, for applications like wireless cameras, it gives us opportunities to provide solutions to broadcasters.”

The graph is Fig. 23 of the FCC's June 2 R&O, page 453. Light Blue: post-incentive auction wireless spectrum; Orange: Channel 37 reserved for radio astronomy and medical telemetry. Diagonally shaded gray: guard bands. The left one is the duplex gap. Blocks 21–36 and 38–44 represent the remaining DTV channels based on the amount of spectrum sold, indicated at left. WASHINGTON—The National Association of Broadcasters said it’s OK to put six TV stations in the duplex gap in the post-incentive auction repack, but only if they must. The NAB’s Rick Kaplan proffered the compromise in a letter to the Federal Communications Commission on Tuesday. It opened with a cautionary tale about not overdoing it.

“The NAB urges the commission to uphold the widely supported compromise it adopted in the incentive auction order that dedicates the 600 MHz duplex gap for unlicensed uses and wireless microphones used to cover breaking news and local and national emergencies,” Kaplan said. “It is unclear why, 14 months after the FCC adopted this compromise, commission staff now believes it essential to impair the duplex gap with TV stations in certain markets across the country. If adopted, this change would eliminate both the guaranteed nationwide channel for unlicensed uses and the very limited remaining reserved spectrum available to broadcasters to cover critical news events. No other solution being discussed comes close to supporting both of these important services.”

Kaplan further said that, while the NAB “remains opposed to the proposed impairments,” it would accept six TV stations in the duplex gap—the buffer zone between wireless up- and downlink spectrum. “Impairment” refers to the interference that putting a TV station in the duplex gap will create for the adjacent wireless carrier. Putting TV stations in the duplex gap renders it ineffectual for newsgathering and reduces the value of the adjacent wireless spectrum. Broadcasters, wireless operators, the white-space device camp and the wireless mic contingent all opposed the FCC proposal to stick TV stations in the duplex gap.

The duplex gap initially was designated for use by wireless microphones and unlicensed, or “white-space” devices. Then the commission discovered it couldn’t reach its lowest incentive auction clearing target of 84 MHz nationwide without being able to put TV stations in the duplex gap. It was set to vote last week on auction rules that would have allowed it, and waived what’s known as the “sunshine period” to release related information late on a Friday evening six days before the meeting. Red flags flew at the NAB, lawmakers got involved and the FCC pulled the item. (See “FCC Postpones Incentive Auction Vote.”)

The meeting was held. The commission voted on another item, and in a press scrum after the meeting, FCC Chairman Tom Wheeler said they needed to put a TV station in the duplex gap in six markets. He did not say how many, but the NAB’s letter said they would agree to one each in up to six markets, with just one of those markets among the top 25.

This is consistent with the data illustrated in the FCC’s sunshine document, in which TV stations in Los Angeles—the second largest TV market in the United States—would end up in the duplex gap at an 84 MHz clearing target. The total number of markets impaired is six. They are Los Angeles (2), Harrisburg, Penn. (45); Madison, Wis. (82); Buffalo, N.Y. (52); Milwaukee (35) and Flint, Mich. (70).

The second of three illustrated clearing targets—114 MHz—would impair seven markets, but none in the top 25. The third—126 MHz—would leave just two markets impaired, though one would be No. 12 Detroit, which likely will be fraught with Canadian coordination issues.

Kaplan emphasized that once the FCC reached its clearing target, that no more stations be put in the duplex gap.

“Thus, if a volunteering station elects to drop out of the auction and cannot be repacked in the broadcast portion of the band, the commission must buy that station at its last accepted price,” Kaplan said. The commission was considering a mechanism called “dynamic reserve pricing” to allow it to adjust that price downward, but seller opposition was fast and furious.

The letter said that the NAB preferred leaving all TV stations out of the duplex gap, and that the commission had “produced no data to suggest that the success of the auction hinges on its ability to impair the duplex gap.”

With the auction eight months away, however, the NAB said it would accept a six-market impairment limit with no dynamic reserve pricing.

Also see…

July 21, 2015
“Incentive Auction is Eight Months Away”
The Federal Communications Commission is considering a date certain of March 29, 2016, reflecting its previously stated goal of getting it done during the first quarter of next year.

July 16, 2015
“What the Heck Is The ‘Duplex Gap’ And Why Has It Blown Up The July FCC Meeting?”
“Difficult as it is to believe, there are times in policy when issues do not break down simply by partisan interest or into neat categories like incumbents v. competitors or broadcasters v. wireless carriers.”

June 12, 2015
“McAdams On: The Auction’s ‘Poison Pill’”
One of the most contested components of the proposed TV spectrum auction rules is “dynamic reserve pricing.”

February 17, 2015
“Eleven FCC Scenarios for The 600 MHz Band Plan”
The FCC is proposing 11 scenarios for a 600 MHz Band Plan following the spectrum auctions. Which of these will be adopted will be determined by the outcome of the auction in 2016.