Cell phone towers can be useful ATSC 3.0 DTS venues.
Will NextGen TV change the world or will the world change NextGen TV’s destiny?
Exactly how broadcasters will leverage NextGen TV to better inform and entertain viewers, and increase revenue with it remains to be seen. What is verifiably certain is that the build out of the national NextGen TV infrastructure is gaining momentum, providing experience, and expanding NextGen TV presence into more markets. According to Pearl TV, NextGen TV is on air in more than 20 cities from nearly 90 stations as of mid-January 2021.
The recent Virtual CES unveiled numerous NextGen TV receivers, while ATSC and Pearl TV were busy behind the scenes with webinars, announcements and projects. Overshadowing nearly all CES NextGen TV news is the FCC REPORT AND ORDER (R&O) adopted January 13, 2021, released on January 19, 2021 regarding single frequency networks (SFNs), more recently becoming known as a distributed transmission system (DTS).
“A DTS network employs two or more transmission sites located within a station’s service area, each using the same RF channel and synchronized to manage self-interference. Because it operates on only one frequency, DTS offers an alternative to traditional full power television transmission, which may use secondary translators that operate on additional frequencies,” the FCC defined in the R&O.
The usable bandwidth of an ATSC 3.0 signal is proportional to its strength and carrier to noise ratio at the receiver. DTS can maximize bandwidth for all viewers by filling in known, high-power, high-tower shadows and gaps every TV station becomes uniquely aware of.
“We conclude that by modestly easing limitations on DTS transmitters and providing additional clarity in our rules, we can help unlock the potential of DTS at this crucial time when many stations are considering migrating to the next generation broadcast television standard (ATSC 3.0),” the opening R&O paragraph states.
It continues “As the record in this proceeding demonstrates, affording broadcasters greater flexibility in the placement of DTS transmitters can allow them to enhance signal capabilities and fill coverage gaps, improve indoor and mobile reception, and increase spectrum efficiency by reducing the need for television translator stations operating on separate channels.” In short, it’s a good deal for all ATSC 3.0 TV broadcasters, commercial, public, full power and LPTV. Everyone wins.
Specifically, the FCC updated the current restriction that prohibits DTS signals from spilling over beyond a station’s authorized service area by more than a “minimal amount.” Consistent with its current approach, DTS transmissions will not be entitled to interference protection beyond the station’s authorized service area. The FCC’s decision to replace the current, subjective spillover standard with a bright-line rule that both expands and clarifies the permissible range of spillover will not only promote DTS use by facilitating more efficient and more economical siting of DTS transmitters, but it also will establish a clearly defined limit that will promote regulatory certainty.
The 41 dBu F(50,50) Contour
The FCC replaced the existing, and imprecise, “minimal amount” standard with a clearer, service-based approach that allows broadcasters greater flexibility in locating DTS transmitters, so long as, for UHF stations, the 41 dBu F(50,50) contour for each DTS transmitter does not exceed the reference station’s 41 dBu F(50,50) contour.
A 41 dBu F(50,50) contour refers to a boundary at which a signal is predicted to exceed 41 dBu at 50% of locations 50% of the time. The FCC provides corresponding dBu values for F(50,50) limiting contours for Low and High VHF stations in the revised Table of Distances included in Appendix A of this Report and Order (Order). Those values are 28 dBu for Low VHF and 36 dBu for High VHF.
This Table of Distances describes (by channel and zone) a station’s maximum service area that can be obtained in applying for a DTS authorization and the maximum interference area that can be created by its facilities.
By definition, a 41 dBu F(50,90) contour requires the predicted signal strength to be exceeded 90% of the time, it encompasses an area where a stronger signal could be expected to be received, i.e., an area smaller than that encompassed by a 41 dBu F(50,50) contour. Additionally, the distance from the 41 dBu F(50,90) contour to the 41 dBu F(50,50) contour is directly related to the radius of the F(50,90) contour, such that a lower power/lower antenna transmitter will have a smaller difference between the two. That effect makes it clear that a DTS node at a certain ERP and HAAT may be located at the edge of a station’s authorized service area. By replacing the current 41 dBu F(50,90) limiting contour with a 41 dBu F(50,50) limiting contour, the FCC gives broadcasters a certain room for spillover from DTS transmitters and thereby enable the placement of transmitters in locations that are not practical today.
NextGen TV News
Pearl TV applauded the FCC's decision to give broadcasters more flexibility when using ATSC 3.0 DTS for NextGen TV broadcasting. Pearl TV managing director Anne Schelle said “We’re pleased that the Commission adopted this change to the rules on Single Frequency Networks, since it will help broadcasters roll out NextGen TV more quickly and more efficiently. Pearl TV worked closely with the National Association of Broadcasters to develop an approach that had broad support across the industry and we’re glad the FCC adopted this proposal." She also said, "Pearl and our Phoenix Model Market partners launched an initial Single Frequency Network system in Phoenix, Arizona last year to test the concept and demonstrate the result of improved coverage and in-building reception.”
Pearl TV recently announced, "America’s broadcasters are now planning a push this year that will initiate next-generation ATSC 3.0 service in nearly 20 more cities by the end of the summer." The push is expected to make NextGen TV service available to the majority of US households by Fall 2021.
In December 2020, Pearl announced, "The Phoenix Model Market Partners are now working closely with Comcast in Portland, Oregon to explore how to deliver NextGen TV services to Comcast’s infrastructure in an effort that will require significant technical collaboration. This work could give the industry a foundation for a “real world” technical example of how to transmit ATSC 3.0 over hybrid fiber-coaxial infrastructure." Seven local broadcasters are now on the air with NextGen TV in Portland.
Earlier in December, five Detroit TV stations collaborated to launch "Motown 3.0 Test Track" marking the beginning of NextGen TV broadcasting in the Motor City. The goal of the Motown 3.0 Test Track is to provide another research and development environment for the automotive industry to road test proof-of-concepts and connected car solutions using the Internet Protocol (IP) capabilities of ATSC 3.0.
Five Tampa/St. Petersburg stations also launched NextGen TV services in early December. Four Columbus Ohio TV stations launched NextGen TV service in January 2021 as did seven major TV stations in Seattle. At its present trajectory, another 20 NextGen TV markets by summer’s end appears realistic.
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