We’ve been hearing a lot about single-frequency networking lately, especially in connection with the rollout of ATSC 3.0. However, the technology has been around for a long, long time, with the first implementation taking place in the mid-1920s, and involving operation of radio stations fairly close to each other and sharing a common frequency.

This “synchronized broadcasting” technology involved the locking of transmitter carrier frequencies together (via a wired connection) to avoid unpleasant beat notes generated by the transmitter oscillators as they drifted slightly in frequency. (It helped if the two stations were broadcasting a common show [network-supplied, for instance] and weren’t geographically too far apart so that the slight delay due to audio delivery via telephone line wasn’t sufficient to cause an audible echo or “flanging” effect on consumer radio sets located midway between the common-frequency signals.)

During the 1950s and beyond, this sort of “on-channel” operation extended to television with the implementation of unlicensed “boosters” that retransmitted an off-air television station to small communities, or perhaps an individual, located in a valley area below the reach of the main TV signal. (These devices were typically located on mountain ridges with a receiving antenna directed at the desired station, followed by an RF amplifier feeding a transmitting antenna directed down into the valley without TV service.) These “boosters” could — and sometimes did — cause interference to television reception and other communications, and as such were a source of aggravation to the FCC. However, they did prove that on-channel operation of two or more transmitters was possible, if there was sufficient shielding from natural terrain to prevent multiple signals from reaching receivers.

[Read: Dallas ATSC 3.0 SFN Buildout Nears Completion]

Somewhat later, in the evolution of broadcast television, legal operation of such signal boosters or “gap-fillers” was permitted — but with care given to prevent interference to consumers in a station’s main service area through the use of terrain shielding and/or highly directional antennas.

Fast forward to the advent of digital television, and SFN technology took a giant leap forward due to the nature of the transmitted signal and the ability of receivers to reject unwanted signals (analogous to “ghosts” in analog television produced by reflections that create multiple signal paths). No longer did SFN implementers have to rely strictly on blocking of unwanted signals by terrain. According to ONE Media’s Fred Baumgartner, the very flat terrain in the Dallas/Ft. Worth area was one of the factors in locating the initial ATSC 3.0 SFN trial in that market, as it provides a “worst case” scenario in terms of terrain shielding.

Television industry consultant S. Merrill Weiss recognized early on, and engineered the world’s first ATSC 1.0 SFN in the State College, Penn., area to provide better coverage for the city’s WPSX-TV (now WPSU-TV). The use of DTV SFN technology has since spread to a number of other areas.

“There were 29 [SFN] applications filed before the repack,” said Weiss. “Of those 19 were approved before the freeze, and I believe all were built.”

Even though the technology has proven successful with ATSC 1.0, ATSC 3.0 should make television SFNs easier to implement.

“ATSC 1.0 is dependent on the design of the adaptive equalizer which can be quite different in its performance from receiver to receiver,” said Weiss. “ATSC 3.0 is dependent on the modulation that’s used, and all receivers will respond to it identically. And on top of that having multiple carriers (inherent in the 3.0 OFDM [orthogonal frequency division multiplex) signal] makes things a lot easier.”

Yiyan Wu, a scientist at Canada’s Communications Research Centre who has been heavily involved in the development of ATSC 3.0, added another factor in the signal’s potential versatility “ATSC 3.0’s OFDM modulation has a longer guard interval [than 1.0’s] and this provides more protection,” said Wu. “ATSC 1.0 uses variable equalization, and the longest echo that it can handle is about 64 microseconds. ATSC 3.0 can handle 150 microseconds. Longer echo means that your power can push out further. The longer the guard interval, the less transmission power you need.”

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METUCHEN, N.J.—When the upcoming TV spectrum incentive auction concludes later this year, the heavy lift begins. Several hundred TV station signals—as many as 1,200 according to one estimate—will have to be repacked into a reduced amount of spectrum. Think of running a giant electronic jigsaw puzzle through a compression codec to fit it into a smaller space. What’s more, consider that there will be no way to know which pieces will have to be fit into how much space, until after the auction.

By comparison, the repack following the 2009 digital transition involved a set amount of space and the knowledge of where nearly every puzzle piece would end up, much earlier in the process.

TV Technology has canvassed many experts over the last several months about how this next repack will be carried out, and what TV stations can do to anticipate it. We put the question to S. Merrill Weiss, a respected and well-known media engineer whose contributions were fundamental to the development and deployment of digital television. His credits include Fellow status with the Society of Motion Picture and Television Engineers, and winner of that group’s prestigious David Sarnoff Gold Medal Award, its highest technical recognition, the Progress Medal, the Engineering Achievement Award from the National Association of Broadcasters, and the Bernard J. Lechner Outstanding Contributor Award from the Advanced Television Systems Committee. 

Weiss provided a succinct and cogent breakdown of what TV stations and engineering personnel are up against with regard to the repack. Specifically, we ask what is necessary for stations to know and/or do immediately. Mr. Weiss responded as follows:

The answer is not simple. It all depends on the station’s position in the incentive auction and how the outcome of the auction affects the station’s situation.

There are a number of categories into which each station may fall. In addition, knowing what to do can be obscured from station personnel by upper-management decisions of which the station folks may be unaware. (I know first-hand of several cases of that sort.) The result can be that the stations cannot plan because they don’t know what possible fate awaits them. 

There can be good reasons for this, given the FCC’s proscription of communication to other participants of strategies and positions being taken in the auction.

To categorize at least some of the possible situations in which stations may find themselves, here are some that come to mind, on which I will elaborate below:
Stations that choose to go off the air;
Stations that choose to channel-share with one or more stations;
Stations that choose to move from one band to another (i.e., from UHF to High-VHF or to Low-VHF, from High-VHF to Low-VHF);
Finally, stations that are repacked whether they want to move or not.

Each of these categories brings a different set of considerations. Taking them one by one:

· Stations that choose to go off the air: It seems unlikely that station personnel will be told about such positions being taken in the auction, because such information could lead to a mass exodus for something that might never come to pass, depending on what happens in the auction.

Moreover, having station personnel on the street, seeking other employment, would serve to other stations as a signal of a station’s position in the auction, which communication is forbidden. Given this, I doubt such stations will be able to do anything in advance. Once the auction is over, the only things to be done will relate to preparing to shut down operations and to salvage whatever of a station’s facilities and equipment might have value post-auction. 

There will be 90 days after the auction, with the possibility of an extension of another 90 days, for the station to go off the air. Any salvage work can happen thereafter for as long as it takes. Of course, it also could be that a station will go off the air but maintain certain operations for distribution of its content by other means, for instance, by cable or by Internet delivery.

· Stations that choose to channel-share: This is one category in which stations can prepare, if their personnel know about the plan to share. (They very well may not know of such plans, for reasons similar to those already described.)

Even in cases in which station personnel know of sharing plans, it may not be possible to move forward beyond planning because actual implementation of such plans is likely to depend on one or more of the sharing parties being successful in the auction. So, implementation will depend on knowledge of such success.

Considering the planning that can be done before the auction is finished, it largely will focus on designing the facilities for a joint operation, selecting the protocols used to connect the stations together, deciding where to place certain equipment such as encoding pools, and so on. Some of this already has been done, in some cases, as a part of channel-sharing negotiations, but there may be other cases in which it is yet to be done.

Even when it has been done to a certain level for purposes of writing a contract, there still are likely to be details to be worked out, such as operating plans and the like.

· Stations that choose to move from one band to another: This is another category in which station personnel could prepare plans for post-auction facilities and operations—once again, if they know what position is being taken in the auction. 

Such plans could include preliminary technical designs and budgets. They would have to remain very preliminary because the real designs would depend quite heavily on what channels and coverage areas the stations are allotted by the FCC, which won’t be known until the auction is completed.

Then, there may be tradeoffs required to fit antennas and other equipment into the space available on towers or in transmitter rooms or shelters. Yet another possibility is that stations might be able to seek modification of the facilities that the FCC allots them, and that is likely to lead to design impacts, too.

· Stations that are repacked: Stations that choose not to participate in the auction may be orphaned in the middle of the new wireless broadband spectrum and have no changes to make. Others that either chose not to participate or that were not successful in the auction might be moved to a new spectrum location by the FCC.

In such cases, certain equipment that is channel-dependent is likely to have to be replaced, modified, or retuned, depending on its nature. Such changes are predictable and can be planned to some extent, although real planning will require knowledge of the actual channels to which the stations will move.

Again, there may be tradeoffs required due to space constraints of one sort or another (e.g., channel-dependent equipment can be larger at lower frequencies than at the higher frequencies from which the stations are likely to be moving).

Certainly, preliminary plans and budgets can be prepared, but they will have to be finalized post-auction, once the true outcome is known. Again, too, there may be opportunities for modifications of what the FCC allots to stations, which would be another cause for having to delay completion of planning and budgeting until after the auction and repack.

· Additional considerations: In respect to the last two cases, in which stations will remain on the air but move to new channels (including those that will channel-share on their new channels), it was mentioned that modifications of FCC-allotted facilities might be possible. This would be done to improve the service areas and signal strengths of the station facilities before they are built.

Planning for such potential opportunities could include lining up consultants to consider such possibilities as soon as the auction results are known. The chance exists that there will be a “land rush” after the auction, and, if there is, the stations that apply first are more likely to get what they might want than those that apply later. 

The extent to which this possibility will exist will depend on what the FCC will be willing to entertain post-auction. To some extent, that willingness will depend on what the commission already has decided, but they still are making decisions, leaving the potential for opening doors that may now seem closed.

Join Mr. Weiss on Tuesday, March 8 at 2:30 p.m. EST for “Drilling Down Into the Post-Auction Repack,” an exclusive Webinar produced by TV Technology and B&C, and also featuring theFCC’s Howard Symons; NAB’s Patrick McFadden and RF experts Jay Adrick and S. Merrill Weiss. Register here

Also see:
Feb. 26, 2016
“McAdams On: The Repack”
The post-incentive auction TV channel repack will make or break broadcasting. That’s not just my assessment, but the abridgment of many off-the-record conversations I’ve had over the last year with people who know a lot more than I do.

HOLLYWOOD, CALIF.—Shortly before the start of the SMPTE 2015 Annual Technical Conference & Exhibition, TV Technology spoke with S. Merrill Weiss about the upcoming track of sessions “Archiving the Future and the Future of Archiving” for which he is the session chair.

TV TECHNOLOGY: What is the future of archiving? How different does it look from what we envision today as “archiving,” i.e., a sort of a virtual library full of files.

 S. Merrill Weiss
S. MERRILL WEISS: Future archives are likely to be organized differently than they have been in the past. The trend already has begun toward “Object-Based” archives, as opposed to the storage of individual files as has been the practice previously. The issue with just storing files is that files that are related to one another, but of different content types, can end up in disparate locations, from which they can be difficult to retrieve when needed together. Examples of this phenomenon are files related to a single production project, which could have hundreds of thousands of image acquisition files representing individual frames, hundreds of audio acquisition files, a script in a word-processing document, a budget in a spreadsheet document, listings of props and locations in a database, binary applications to be broadcast along with the final production, and, of course, all of the files generated during post production in an array of versions. Archive Objects can collect all of the files from such a project and maintain their relationships to one another while storing them for both operational and long-term preservation purposes.

Another factor regarding future archives is that they will become much closer to what we consider to be operational storage today. There will be less differentiation between the two types of storage. Indeed, many productions today record for acquisition or post-production purposes directly to media intended for long-term storage. Doing so makes it easier to preserve all of the material created and collected as part of the production and post-production processes. The trend seems likely to continue and to accelerate.

Helping to facilitate the use of Archive Objects is a recently standardized approach developed within SMPTE called the Archive eXchange Format (AXF). AXF is a wrapper structure that enables archives to be independent of the hardware systems, operating systems, files systems and software applications on which they are created. That independence further enables archives to be recovered without the need for use of the original archive systems on which they were created. In fact, it permits recovery without the need for any archive system at all, thereby virtually eliminating the potential for orphaned archives. AXF already is seeing widespread use in the Media and Entertainment space and has the potential to extend to archiving applications of all sorts in all sorts of industries.

TVT: Will it be off-site? In the cloud?

WEISS: Future archiving is likely to be a mixture of on-site and off-site storage, with off-site and cloud storage becoming more widespread over time. Cloud storage, in particular, will depend on the use of Archive Objects to maintain relationships between files that are associated with one another as they are transferred from and recalled to producing, post-producing, and distribution locations and organizations. In fact, one of the trends in storage per se is the application of Object Storage in combination with geographic dispersal of data. Use of such techniques is facilitated by construction of Archive Objects specifically to enable streaming their data, which is the approach taken by AXF. It provides for the fastest transfer of files and their content between locations through whatever communication means happen to be applied.

TVT: With media companies creating multiple streams of content 24/7, will there have to be a systematic purge of archives?

WEISS: If anything, the trend is toward deleting less and less. With the plummeting cost of storage, it becomes more expensive to decide what is worth saving from what is not than it is just to save it all. Moreover, it is very difficult to know what will be of value in the future. With metadata bound to files and their content becoming simpler to establish and providing more relevant information about the content, appropriate matter for particular needs becomes easier to locate and recover from storage. The combination of these factors favors retention over elimination.

TVT: How important has the role of metadata become in archiving?

WEISS: As with so many aspects of media production and management, metadata has become critical in archiving. It is what allows the collection of files into Archive Objects. It is what allows the content of files to be known and selected. It holds all of the information needed for formal archival processes as needed for meaningful long-term preservation. A problem with the prevalence of metadata is that it is expensive to generate and collect. A consequence of this situation is that some content producers now are seeking to collect metadata on the set as content is created, in what have come to be called “digital birth certificates,” as a means of controlling the costs of metadata creation later. Work is under way in SMPTE to extend the AXF protocol to cover the needs of on-set creation of digital birth certificates, as it has been recognized by a number of producing organizations as a useful vehicle for providing the needed services.

S. Merrill Weiss is president of Merrill Weiss Group LLC and a consultant in electronic media technology and technology management. In a 46+ year career, he has spent more than 36 years involved in work on SMPTE standards. Merrill is a SMPTE Fellow and has received the SMPTE David Sarnoff Gold Medal and the Progress Medal. He also was a recipient of the NAB Television Engineering Achievement Award, the ATSC Bernard Lechner Outstanding Contributor Award, and the IEEE Matti S. Siukola Award.