Using single frequency network technology to supplement a station’s main ATSC 3.0 signal looks to improve service, increase over-the-air audience and enable new revenue sources, including better reception by mobile devices and data delivery. But this would come at a price of nearly $2 million per station, according to a plan developed by engineering consultants Meintel, Sgrignoli & Wallace.
How much is it worth to deliver a stronger TV signal throughout a market?
Many station groups will likely find themselves confronting that question if ATSC 3.0 — the next-generation digital television standard currently under development — is authorized by the FCC.
A recent study by engineering consultancy Meintel, Sgrignoli & Wallace for Pearl, the consortium of nine major station groups working to bring next-gen TV to fruition, found that doing so comes with an equipment cost of nearly $2 million per station.
That is the price estimate for a very specific scenario which envisions deploying four single frequency network (SFN) sites to augment the strength of the signal transmitted from the Big Stick , says Dennis Wallace, managing partner of Meintel, Sgrignoli & Wallace.
The scenario envisions the SFN sites located at the periphery of a service area. Each would use a directional antenna pointed back at the center of the market where the Big Stick resides and transmits at full power, he says.
The RF technology required at each SFN site, including a transmitter, combiner, feed line, STL and broadband antenna would cost about $2.77 million, or about $11 million total.
The scenario depicted in the study envisions six local stations sharing the transmission sites, which translates into about $1.9 million apiece for the technology, Wallace says.
Wallace has dubbed this type of network a sparse SFN, as compared to a dense SFN with 15 to 20 individual transmitter sites, which is more akin to some SFN deployments in Europe.
What broadcasters may well end up purchasing for their $2 million SFN investment depicted in this scenario is a future filled with improved service delivery, a growing over-the-air audience and new revenue sources.
“Single frequency networks are a tool in the ATSC 3.0 toolbox that will allow broadcasters to build business models that reflect their individual markets’ needs,” he says.
For example, delivering a higher signal level throughout the coverage area will enable transmission of more robust signals enabling better reception by mobile device, he says.
Broadcasters with service areas shielded by hills and other obstructions will benefit as well.
“If you are in a place like Pittsburgh where it’s very difficult to achieve coverage because of topography, an SFN will allow you to fill in those areas where you had weak signal and coverage,” Wallace says.
Indoor reception farther into buildings also will improve not only because signal strength is greater but also because signals are coming from multiple directions, one of which will likely be in line with a window or other feature easily penetrated by the transmission, says Jay Adrick, a former VP with GatesAir and now a consultant to the company.
SFNs can even make it easier to deliver Ultra HD to the home.
“If I want to deliver Ultra HD, I need to achieve a much higher signal level in order to get reception of my Ultra HD service.
“Instead of being at 15 dB, I might need to be near 20 dB because UltraHD is a real high data rate service. How do I make that up? By deploying an SFN,” Wallace says.
Even new services, such as robust data delivery over the air for third parties, will benefit from higher signal strength and SFNs, he adds.
Other SFN operational costs exist, including electrical power, which for the four sites combined will equal or slightly exceed the cost of power for the Big Stick, and the monthly cost of leasing, or one-time expense of building, a tower at each site, he says.
“There are also some economies of scale that might be gained in terms of actual labor costs,” Wallace says. “You might have one or two engineers to take care of all the facilities in a market as opposed to every station having its own RF engineer or transmitter engineer.”
However, it is not necessary for a station to incur the entire cost of deploying a four-site SFN as envisioned by the study in one fell swoop, says Anne Schelle, managing director of Pearl.
“There are different factors that will dictate the buildout from market to market,” she says. “You are going to be looking [to use] existing facilities as much as possible, and build out the SFNs as required.”
It is even possible that just as wireless carriers use cell sites built and managed by companies like American Tower and Crown Castle, broadcasters too could turn to a third party to build and maintain SFN sites for a fee, she says.
Today, a handful of SFNs exist around the country transmitting ATSC 1.0 (A/53) digital television.
Broadcasters transmitting a future OFDM-based ATSC 3.0 signal may be more attracted to deploying single frequency networks because orthogonal frequency division multiplexing removes some of the complexity involved with single-carrier 8VSB SFNS.
“The guard interval [built into an OFDM transmission system] allows for the reception of multiple signals [that are] delayed without impacting the ability of the receiver to receive,” Wallace says.
The upshot is greater flexibility in locating the SFN sites in the network because the timing of signals arriving at a receiver from each location is not as critical.
Sharing SFN sites within a market has another benefit that may become particularly important following the FCC’s repack of TV stations into less spectrum.
“Sharing of sites buys us better spectral efficiency because if you have adjacent channels, you are going to solve the interference of adjacent channels by combining those facilities and co-locating,” Wallace says.
“Now I don’t have to worry about protecting an adjacent channel in the same market if we are all co-located at the same facility.”
By co-locating adjacent channels at the same SFN facilities, the signals from adjacent channels will likely travel along a similar path to the TV, and the path loss of both signals will be about the same, he says.
As a result, the TV tuner is much more likely to be able to tune in the desired channel without interference from a stronger adjacent channel signal. If the channels’ transmitters were located separately, it is possible that the adjacent channel could be closer to the TV tuner, delivering a stronger signal than the tuned channel and causing interference, Wallace explains.
While single frequency networks can ensure stronger signal strength throughout a market and open up new opportunities to broadcasters, they are not a requirement of ATSC 3.0.
“Broadcasters don’t have to use it if they don’t want to,” Wallace says. “But certainly the broadcasters who see value in single frequency networks, they have that toolset available to them, and it will provide them with a lot more options.”