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
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
“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,
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.
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
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
requirements, Weller said.
With regard to input, analog records will always be interpreted as digital
facilities, he said. The study must contain just
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.
August 20, 2013,
TVStudy Update No. 3 Does Cross-Border Analysis
July 22, 2013:
Releases Channel Repack Analysis, Updated OET-69 Software
of the key advantages of the
Version 1.2 software is its ability to easily replicate multiple stations to
generate various nationwide scenarios,” the commission said.
April 26, 2013,
Releases Updated OET-69 TVStudy
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:
Update Injects Legal Uncertainty
Insiders say wagons are circling over the new methodology for predicting TV
station coverage and interference.
February 5, 2013
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.