[opendtv] FCC Gives Official Nod to DTS

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Thu, 4 Dec 2008 17:48:45 -0500

"However, digital demodulators can be designed to allow receivers to
lock onto the most viable DTV signals and ignore the rest."

It is perhaps this misunderstanding of how SFNs work that creates most
of the overly optimistic predictions one sees consistently on this
topic. STILL now, after several SFNs have already been deployed in the
real world.

Receivers do not lock into any one transmitter and ignore the rest. Not
unless "the rest" are so much lower in strength that they are totally
overpowered by the one. The problem is always in areas of equal or near
equal power density, from two or more towers. Unless, of course, there's
some obstacle, at and near the contour lines, that makes reception

So I don't give a lot of weight to the idea that on-channel DTS expands
coverage area, if ubiquitous coverage over the area is required.
Although it could make reception easier within a given big stick area.

On the other hand, creating a system that works just as stated: "to
allow receivers to lock onto the most viable DTV signals and ignore the
rest," using translators (i.e. on different freqs), is IMO doable. And
it would IN FACT be more like a cell phone system, and it could
eliminate the need for big sticks.



FCC Gives Official Nod to DTS
by James E. O'Neal, 12.03.2008


Although the concept of Distributed Transmission Systems (DTS) has been
around for a number of years, and has even been deployed experimentally,
the FCC has been slow to issue its formal blessing. That finally changed
earlier this month when the commission issued an official green light to
implement the technology that closes holes in a digital television
station's service area.

DTS-also referred to as single frequency networking or on-channel gap
filling-originated some 17 years ago by S. Merrill Weiss, president of
Merrill Weiss Group LLC, who said that while he's pleased with the FCC
decision, the champagne glasses are not coming out of the cupboard just

"I'm not planning a celebration; there's still a lot of work to be
done," Weiss said. "I think that it will be a slow rollout, but there
are some stations that will benefit immediately. It will take the FCC
some time before the rules are fully in operation."

Weiss said that he expected some of the first stations that might take
advantage of the technology would be those with significant coverage
issues, but it could eventually be used more widely by those wishing to
engage in handheld and mobile TV broadcasting, as good signal coverage
is especially important for those applications.

Jack Wilson, director of marketing and business development at Axcera, a
company that has been heavily involved in DTS implementation and
testing, shared these views.

"Field testing has shown that DTS can significantly improve coverage in
a broadcaster's service area, most notably filling in coverage gaps
caused by terrain shielding or transmitting antenna deficiencies," he

He further acknowledged that the technology would play a big part in
making mobile television a reality.

"With the progression of ATSC M/H technology, DTS will provide a
significant coverage advantage for mobile TV services," Wilson said. "A
single high-power station isn't going to provide the service required
for mobile handheld devices with their lower gain receive antennas that
are only four feet off the ground, then a single high-power station
isn't going to provide the service required. You will also need more low
power sites for in-building coverage-this would be a driving factor for
DTS deployment. I believe that the most ubiquitous adoption of DTS will
be for mobile services to achieve the desired coverage, especially
in-building penetration."

DTS was made possible with the advent of digital television
broadcasting. Multiple transmitters operating on the same frequency and
sharing the same program feed can provide service to viewers' homes and
their mobile and handheld devices that otherwise might not receive
adequate signals. With analog television, the multiple signals would
hopelessly jam one another. However, digital demodulators can be
designed to allow receivers to lock onto the most viable DTV signals and
ignore the rest.


As DTS technology can provide coverage into areas totally unserved by
conventional tall transmitting towers and high-power transmitters, Weiss
was asked if he thought it might eventually spell the end of the tall
tower era of broadcasting.

"No, certainly not in the near-term," Weiss said. "There's too much
investment in tall towers right now. I see most stations using gap
fullers where they have areas [to service] that are obstructed from tall
towers, or where they have a lower power operation and can use the
technology as a service extender. Either way, it keeps high-power tall
tower operations going. In some situations, broadcasters could save
money and provide more reliable service, but I think that this will take
a long time."

For stations wishing to implement DTS, at minimum, a new transmitter,
antenna and methodology for obtaining a signal to transmit must be
provided. Weiss estimates that putting a "gap filler" on the air could
run between $50,000 and $150,000.

"It depends a lot on the size of the facility," Weiss said. "Some of the
cost will depend on how the facility gets the signal."

Some DTS installations may be able to get by with off-air pickup of the
broadcast signal from the station's primary transmitter. Others may
require fiber interconnection or the use of microwave radio facilities
for receiving a signal for transmission. If the area to be covered is
large and a station has multiple secondary transmission sites in areas
not easily served by fiber or microwave, then satellite distribution is
a possibility.

Weiss said that it was too early to know if the commission would allow
stations that will no longer be able to cover their original service
area to expand their reach with DTS.

"I can't answer that at this point," he said. "We probably won't know
until the full Report and Order is released."

Wilson said that single frequency networks make more sense than going
with traditional translator technology for filling such coverage gaps.

"Certainly DTS is the most spectrally efficient solution when
broadcasters complete the buildout of their coverage area," he said.
"DTS is operationally a better solution than rebroadcasting on different


The commission's decision came on the same day it voted to permit
unlicensed "white space" devices to operate within spectrum previously
set aside exclusively for television broadcasting.

A sizable group of white space device proponents view DTS as a direct
threat to maximizing opportunities for white space operation-more TV
transmitters in more places equates to less unused spectrum.

In comments representing the views of more than 20 DTS opponents filed
with the commission more than two years ago, the New America Foundation
and the Media Access Project declared that a favorable decision on DTS
would provide "a redefinition of broadcaster's service areas to include
many of the white spaces not currently covered by a broadcaster's
current single high-powered transmitter," pointing out that it could
eventually lead to "tens of thousands" of new television transmitters.

Weiss was unsure how the commission would balance the two interests.

"The broadcasters certainly are providing a service to some proportion
of the population, as evidenced in the Wilmington case," he said. Weiss
was referring to the September Wilmington, N.C. analog shutoff where
local station WECT lost viewership-a situation which potentially could
be remedied through the deployment of DTS. "The other interests claim
that they want to eliminate broadcasting from that spectrum within five
years and that they want to increase their power from 40 mW to 10 W.
They say they will keep coming back to the commission until they achieve

Weiss cited the success of a five-year DTS test in Pennsylvania that
allowed WPSU-TV, a PBS member station owned and operated by The
Pennsylvania State University, and licensed to operate in Clearfield,
Pa., to reach an underserved area.

"The station was blocked from providing service to its full market,"
Weiss said. "Now that's possible."
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