WASHINGTON — The software developed to determine TV channel assignments following next year’s spectrum incentive auction can churn hundreds of millions of data sets requiring hours of processing. That would presumably comprise a final analysis of the entire United States.
A test run of TVStudy software involving 13 Alaska TV stations took less than a minute on a MacBook, according to Robert Weller, technical analysis branch chief for the Federal Communications Commission’s Office of Engineering and Technology. He and his colleague, Brett Tarnutzer, assistant chief of the FCC Wireless Telecom Bureau, presented a run-through of the commission’s TVStudy on Thursday.
“Repacking is a ‘map-coloring’ problem,” Weller said, whereby stations are separated far enough to prevent interference, but close enough together to maximize the use of the spectrum.
A repack scenario was presented assuming 84 MHz was claimed from the TV band for wireless broadband use, leaving Chs. 2-36 for TV station operation. The intent of the repack is to assign channels in the most spectrum-efficient manner possible while minimizing interference for households with reception within a defined coverage area. The coverage area is defined as the noise-limited contour without regard to interference. Therefore, all households within a coverage area do not necessarily have reception because terrain obstructions, for example.
TVStudy is based on Bulletin OET-69. OET-69 uses the Longley-Rice method for determining TV signal coverage and interference and was used to repack TV channels following the auction of 108 MHz of broadcast spectrum in 2008. It uses a five-step process:
- Establishes service contour.
- Divides area into cells.
- Determines if coverage exist in each cell.
- Determines interference in each cell.
- Determines each cell with interference-free coverage.
TVStudy represents an updated version of OET-69 in software form.
The Alaska demonstration assumed the commission’s proposal that new interference introduced by repacking cannot exceed 0.5 percent for any station involved, and can only “replace” interference that existed as of Feb. 22, 2012.
The software generates “pairwise” data files that yield what the commission calls a “yes-or-no determination” on predicted interference between co-channel and adjacent-channel stations. Weller said pairwise studies could generate multiple scenarios with point-by-point breakdowns.
Only full-power and Class A stations were used in the Alaska demo. Canadian channel assignments were assumed built at maximum ERP and allowed to interfere with U.S. stations. The criteria selected for the demo reflected those proposed in the February Public Notice introducing TVStudy: 2010 Census data and block locations; terrain data of one arc-second (rather than three); potential errors in the commission’s TV database; 0.75 degrees of beam tilt if actual values are unavailable; depression angles calculated from average height above mean sea level; and a uniform global grid system, in this case, measuring no smaller than 0.5 kilometers.
One exception involved Longley-Rice KWX-3 warnings, which flag cells in the grid for dubious reception. The jury is still out on how to treat KWX-3 warnings in the next repack, so for demonstration purposes, reception was assumed. The demo was carried out on three proxy channels, generating millions of output points. This data is intended then for analysis by other software that can determine de minimus requirements, Weller said.
With regard to input, analog records will always be interpreted as digital facilities, he said. The study must contain just one scenario, which can be a group of stations. It cannot include any stations in Southern or Eastern hemisphere, “so Guam is a special case that may have to be handled outside of pairwise method,” Weller said. The grid can be no smaller than 0.5 kilometers in a pairwise study, and no two facilities with same FCC facility ID.
“For 13 stations, largest files can have more than 600,000 rows in the output file,” Weller said. “So for a study with all stations in the U.S., the number is in the hundreds of millions.”
The 13-station Alaska test took 34 seconds on a 2.9 GHz i7 MacBook, an just 15 seconds for a 3-band pairwise study using a 2-by-2 kilometer grid. Stations can be labeled “desired” or “undesired.” The output is generated in CVS files.
Tarnutzer said this data is then used to develop a set of constraint files that allow a feasibility assessment for reassigning channels. The constraint files yield the universe of channels a station can be assigned. These are called “domain files.” The domain files allow for channel assignments in Canada and Mexico, as well as the 11 metropolitan areas where TV spectrum is dedicated for Land Mobile operations. Ch. 37, which is occupied by radioastronomy, is omitted from all domain files. The staff also assumed no repacking restrictions due to maritime radio except for Ch. 17 in Hawaii.
He said the commission was continuing to work with Canada on border coordination issues and would announce any developments “when it’s time.”
The audio and the slides from Weller and Tarnutzer’s presentation will be posted within the next couple of days, an FCC spokesperson said.
Also see…
August 20, 2013, “TVStudy Update No. 3 Does Cross-Border Analysis”
July 22, 2013: “FCC Releases Channel Repack Analysis, Updated OET-69 Software”
“One of the key advantages of the TVStudy Version 1.2 software is its ability to easily replicate multiple stations to generate various nationwide scenarios,” the commission said.
April 26, 2013, “FCC Releases Updated OET-69 TVStudy Software”
“This update addresses an issue with calculation cell indexing that can result in the population of some cells not being correctly considered, and which may cause the program to crash in unusual instances.”
February 6, 2013: “NAB—OET-69 Update Injects Legal Uncertainty”
Insiders say wagons are circling over the new methodology for predicting TV station coverage and interference.
February 5, 2013, “FCC Reveals Crucial Piece of TV Channel Repacking Model”
The FCC has quietly revealed what amounts to its methodology for repacking TV channels in the post-incentive auction spectrum band. The agency released a new version OET-69 software that it intends to use for the repacking, and is seeking input on its efficacy.
