Distributed transmission system
Encyclopedia
In North American digital
terrestrial television
broadcasting, a distributed transmission system (DTS or DTx) is a form of single-frequency network
in which a single broadcast signal is fed via microwave
, landline
, or communications satellite
to multiple synchronised terrestrial radio transmitter sites. The signal is then simultaneously broadcast on the same frequency in different overlapping portions of the same coverage area, effectively combining many small transmitters to generate a broadcast area rivalling that of one large transmitter or to fill gaps in coverage due to terrain or localised obstacles.
digital television standard in use in North America was not designed for this mode of operation and was poorly-adapted to these applications. The restrictive timing requirements and poor multipath interference
handling of early ATSC implementations would have precluded multiple synchronous transmitters on the same frequency at the time of the first wide-scale commercial ATSC deployment in 1998; these restrictions eased somewhat as receiver design advanced in subsequent years. By 2004, technology existed to provide digital television receivers with the means to detect static (not mobile or changing) multipath interference (subject to certain timing constraints) and compensate for its effects on the digital signal.
Tests have been run by various individual broadcasters or broadcast groups, including the Metropolitan Television Alliance
(MTVA, a consortium
of New York city
television stations). A series of initial tests involving four distributed transmission sites and over 100 test measurement sites in NYC and New Jersey were completed in June 2008, along with smaller-scale tests in New York in 2007. The New York market is uniquely problematic for multipath reception due to the large number of man-made obstacles which prevent adequate digital coverage of the entire city from the main broadcast facilities atop the Empire State Building
. (The proposed 1776-foot Freedom Tower
has not yet been constructed, and the 2009 US DTV transition
has already been completed.)
; in the worst case, it is detected as a main signal and a reflection both of equal strength as signals arrive from multiple transmitters to the same intermediate location at slightly-different times.
The ATSC
standard used for digital television
in North America, unlike the DVB-T
standard in Europe
and other nations, uses 8VSB
instead of OFDM—a modulation
which allowed a station to transmit at lower peak power levels, but which historically has been far inferior in handling multipath reflections and RF interference.
The first widespread commercial deployment of US ATSC digital television began in 1998, with the first early adopters being stations in the largest markets (including New York city, served by transmitters atop the World Trade Center
). Digital receivers of this era, while expensive, were poorly equipped to deal with reflected signals—a severe drawback in urbanised environments. Later generations of receiver design significantly mitigated these limitations; by 2004 technology existed to build receivers capable of detecting and compensating for static multipath interference conditions where a single echo was 10dB weaker (within a 30 microsecond time difference) or the same strength (the worst case, but within a 12 microsecond range).
If the transmitters could be kept at sufficiently-precise synchronisation and sufficiently-close geographical spacing to operate within these limits, a single-frequency network using the new receiver design would be possible even with the existing North American ATSC digital broadcast standards.
Tests by Pennsylvania State University
public educational WPSX-TV (now WPSU-TV) were initially made in 2003 WPSU is a VHF 3 station which serves State College, Pennsylvania
from a distant transmitter which must also cover Johnstown
and Altoona
. As a digital station, WSPU had used a large UHF 15 transmitter at the location of the original low-VHF
broadcast tower, leading to localised problems with terrain shielding which interfered with UHF reception in State College itself. Relocation of the main transmitter would have interfered with the station's ability to serve the other two communities. Addition of a small (50 kW) synchronised digital TV transmitter in State College, on the same frequency as the main UHF 15 signal, proved a means to improve reception; further improvements would be possible by adding small co-channel 50 kW transmitters in each community to be served.
ATSC released standards on September 25, 2004 as guidance on the design of multiple transmitters, single frequency networks and multiple frequency networks. The new 2004 standards included:
Technical issues addressed included that of synchronisation between transmitters (GPS was used to supply a 1Hz and a 10 MHz reference frequency, as well as timing information) and precise control of transmitted frequencies (to within 1Hz). Identification for each individual transmitter needed to be embedded in the signal for troubleshooting purposes, yet the main data stream on every synchronised transmitter must be identical; this is done by adding a second, low bit rate spread spectrum
signal 27-30dB weaker than the main signal. As this "watermark" identifier is buried under the stronger main signal, multiple repetitions of this same identifier could be received and summed in order to provide a readable version of the watermark to broadcast technicians. A standard receiver, meanwhile, would see the same signal from all transmitters by design.
The generation of non-MPEG data carried as part of the transport layer
(such as the position of transmitted frame sync, or the initial state of trellis encoding devices) would also have to be matched exactly between every synchronised transmitter. Even though this data is discarded after the received signal is demodulated, any mismatch could create interference between the various co-channel signals. An extra “operations and maintenance” distributed transmission packet (OMP, packet identifier PID:0x1FFA) would need to be added to the ATSC data at the studio and used to control various parameters needed for configuration and synchronisation of the individual transmitters.
The location, directional pattern and power levels for each of the transmitters would also have to be very carefully chosen, as the ATSC system is subject to very strict limits on the maximum time difference between arrival of multiple versions of the same signal at the receiver. In problem reception areas, significant improvements could be obtained but careful design would be required to operate multiple co-channel transmitters without destructive interference.
Further tests run by Telemundo
owned-and-operated station
WNJU-TV, Ion TV and broadcast tower owner Richland Towers using one main New Jersey
transmitter and a Times Square
fill-in DTS secondary transmitter in 2007 indicated that, of fifteen test sites for reception of the station in New York city, 40% would obtain a substantial improvement in signal by the addition of a second transmitter to the existing station, while all but one would receive at least the same signal quality as was observed without a distributed transmission system. New York's Metropolitan Television Alliance
was to run similar tests, but on a larger scale, in 2007 and 2008.
has supported DTS in principle since 2004, an FCC call for public comment at the end of 2005 garnered a wide spectrum of responses in early 2006, ranging from strong support by groups such as the National Association of Broadcasters
to widespread opposition by groups who advocate the free use of "white spaces" (unused broadcast frequencies) for non-broadcast purposes such as wireless data.
The FCC granted six-month special technical authority to WTVE
Reading, Pennsylvania
in December 2006, allowing it to operate a distributed transmission system on an experimental basis but did not authorise the systems on any permanent, licensed basis at that time.
An FCC-sponsored test market exercise in Wilmington, North Carolina
shut down all analogue full-power commercial broadcasts at noon on September 8, 2008. While a large number of the resulting calls from viewers were straightforward questions about installation of antennas and converters, or the need to scan for channels before being able to watch digital television, hundreds more were about a more intractable problem. Viewers of longtime full-power low-VHF broadcasters like WECT
(NBC
6 Wilmington), a signal which in its analogue form reached to the edge of Myrtle Beach
, could no longer receive the station - even with the converter and proper antenna installation. The move to UHF 44 and a different transmitter site had substantially reduced WECT's coverage area and, for many who for many years were on the fringes of the analogue NBC 6 signal, WECT was no more.
On November 7, 2008 the FCC issued an order approving the use of distributed transmission systems by terrestrial DTV broadcasters, subject to various restrictions. This allows broadcasters to apply for DTS facilities to cover the area once covered by analogue TV, while not expanding coverage beyond the existing analogue coverage area. It also prohibits a broadcaster "cherry picking" a coverage area in such a way as to cover urban areas while leaving rural viewers with no signal.
This waiver has come too late to allow the newly-proposed DTS facilities to be constructed and operational before the federally-mandated 2009 analogue shutoff.
The Consumer Electronics Association
and CTIA
proposed in December 2009 to force all stations to use this method, so that the companies they represent could use the remaining space in the TV band for mobile broadband
. Unlike the digital television transition in the United States, they do not propose that stations be forced to pay for it however, much like the 2 GHz broadcast auxiliary service
was forced to move by the FCC, but only after the beneficiary (Sprint Nextel
) compensated broadcasters for the regulatory taking
.
, Spanish language
independent WSTE
7 "Super Siete" currently operates multiple analogue transmitters on the same frequency to cover various portions of the same island; this system has shown limitations due to interference between the transmitters if all are operational simultaneously. Use of a properly-synchronised digital DTS could help to reduce this interference.
In Pennsylvania
, independent WTVE
is licensed
to serve Reading
even though its primary audience is in Philadelphia
. A distributed transmission system now allows it to tailor its coverage area to improve coverage in areas where its signal is currently marginal
.
In Virginia
public television WVPT
/WVPY operate a combined total of five additional on-channel synchronised transmitters to fill areas blocked by mountains from two main VHF/UHF transmitters; a set of US$
100,000 synchronised digital transmitters can replace service from the same number of conventional analogue broadcast translators and also enable overnight datacasting
of instructional materials to the area's 188 school
s.
In New Mexico
, Telemundo
affiliate KTDO
proposes DTS as a means of pairing a low-power DTV facility currently operating in its community of license
(Las Cruces
) with a second facility atop a mountain overlooking El Paso, Texas
in order to reach a wider audience.
In Alaska
, Anchorage MyTV affiliate KYES-TV operates with limited resources and equipment, covering a large and sparsely-populated area with many small broadcast translator stations. While broadcast signal synchronisation is not an issue (as the overlap between signals falls entirely into unpopulated areas), the ability to re-use multiple small transmitters may allow the station to avoid the cost of building one large, expensive main transmitter for its digital signal.
Digital terrestrial television
Digital terrestrial television is the technological evolution of broadcast television and advance from analog television, which broadcasts land-based signals...
terrestrial television
Terrestrial television
Terrestrial television is a mode of television broadcasting which does not involve satellite transmission or cables — typically using radio waves through transmitting and receiving antennas or television antenna aerials...
broadcasting, a distributed transmission system (DTS or DTx) is a form of single-frequency network
Single-frequency network
A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.-Overview:...
in which a single broadcast signal is fed via microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
, landline
Landline
A landline was originally an overland telegraph wire, as opposed to an undersea cable. Currently, landline refers to a telephone line which travels through a solid medium, either metal wire or optical fibre, as distinguished from a mobile cellular line, where transmission is via radio waves...
, or communications satellite
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...
to multiple synchronised terrestrial radio transmitter sites. The signal is then simultaneously broadcast on the same frequency in different overlapping portions of the same coverage area, effectively combining many small transmitters to generate a broadcast area rivalling that of one large transmitter or to fill gaps in coverage due to terrain or localised obstacles.
History
While the idea of a single-frequency network of multiple transmitters broadcasting the same programming on the same channel from multiple transmitter sites is not a new concept, the ATSCATSC
ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
digital television standard in use in North America was not designed for this mode of operation and was poorly-adapted to these applications. The restrictive timing requirements and poor multipath interference
Multipath interference
Multipath interference is a phenomenon in the physics of waves whereby a wave from a source travels to a detector via two or more paths and, under the right condition, the two components of the wave interfere...
handling of early ATSC implementations would have precluded multiple synchronous transmitters on the same frequency at the time of the first wide-scale commercial ATSC deployment in 1998; these restrictions eased somewhat as receiver design advanced in subsequent years. By 2004, technology existed to provide digital television receivers with the means to detect static (not mobile or changing) multipath interference (subject to certain timing constraints) and compensate for its effects on the digital signal.
Tests have been run by various individual broadcasters or broadcast groups, including the Metropolitan Television Alliance
Metropolitan Television Alliance
The Metropolitan Television Alliance, LLC was organized in the wake of the loss of the transmission facilities atop the World Trade Center in 2001. Its mission is to identify, design and build a facility suitable for the long term requirements of its member stations to meet their over-the-air...
(MTVA, a consortium
Consortium
A consortium is an association of two or more individuals, companies, organizations or governments with the objective of participating in a common activity or pooling their resources for achieving a common goal....
of New York city
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
television stations). A series of initial tests involving four distributed transmission sites and over 100 test measurement sites in NYC and New Jersey were completed in June 2008, along with smaller-scale tests in New York in 2007. The New York market is uniquely problematic for multipath reception due to the large number of man-made obstacles which prevent adequate digital coverage of the entire city from the main broadcast facilities atop the Empire State Building
Empire State Building
The Empire State Building is a 102-story landmark skyscraper and American cultural icon in New York City at the intersection of Fifth Avenue and West 34th Street. It has a roof height of 1,250 feet , and with its antenna spire included, it stands a total of 1,454 ft high. Its name is derived...
. (The proposed 1776-foot Freedom Tower
Freedom Tower
One World Trade Center , more simply known as 1 WTC and formerly known as the Freedom Tower, is the lead building of the new World Trade Center complex in Lower Manhattan in New York City...
has not yet been constructed, and the 2009 US DTV transition
DTV transition in the United States
The DTV transition in the United States was the switchover from analog to exclusively digital broadcasting of free over-the-air television programming...
has already been completed.)
Technical issues
To the receiver, a signal from a single-frequency network appears as a single broadcast with strong multipath interferenceMultipath interference
Multipath interference is a phenomenon in the physics of waves whereby a wave from a source travels to a detector via two or more paths and, under the right condition, the two components of the wave interfere...
; in the worst case, it is detected as a main signal and a reflection both of equal strength as signals arrive from multiple transmitters to the same intermediate location at slightly-different times.
The ATSC
ATSC
ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
standard used for digital television
Digital television
Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...
in North America, unlike the DVB-T
DVB-T
DVB-T is an abbreviation for Digital Video Broadcasting — Terrestrial; it is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in the UK in 1998...
standard in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and other nations, uses 8VSB
8VSB
8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM....
instead of OFDM—a modulation
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
which allowed a station to transmit at lower peak power levels, but which historically has been far inferior in handling multipath reflections and RF interference.
The first widespread commercial deployment of US ATSC digital television began in 1998, with the first early adopters being stations in the largest markets (including New York city, served by transmitters atop the World Trade Center
World Trade Center
The original World Trade Center was a complex with seven buildings featuring landmark twin towers in Lower Manhattan, New York City, United States. The complex opened on April 4, 1973, and was destroyed in 2001 during the September 11 attacks. The site is currently being rebuilt with five new...
). Digital receivers of this era, while expensive, were poorly equipped to deal with reflected signals—a severe drawback in urbanised environments. Later generations of receiver design significantly mitigated these limitations; by 2004 technology existed to build receivers capable of detecting and compensating for static multipath interference conditions where a single echo was 10dB weaker (within a 30 microsecond time difference) or the same strength (the worst case, but within a 12 microsecond range).
If the transmitters could be kept at sufficiently-precise synchronisation and sufficiently-close geographical spacing to operate within these limits, a single-frequency network using the new receiver design would be possible even with the existing North American ATSC digital broadcast standards.
Tests by Pennsylvania State University
Pennsylvania State University
The Pennsylvania State University, commonly referred to as Penn State or PSU, is a public research university with campuses and facilities throughout the state of Pennsylvania, United States. Founded in 1855, the university has a threefold mission of teaching, research, and public service...
public educational WPSX-TV (now WPSU-TV) were initially made in 2003 WPSU is a VHF 3 station which serves State College, Pennsylvania
State College, Pennsylvania
State College is the largest borough in Centre County in the U.S. state of Pennsylvania. It is the principal city of the State College, Pennsylvania Metropolitan Statistical Area which encompasses all of Centre County. As of the 2010 census, the borough population was 42,034, and roughly double...
from a distant transmitter which must also cover Johnstown
Johnstown, Pennsylvania
Johnstown is a city in Cambria County, Pennsylvania, United States, west-southwest of Altoona, Pennsylvania and east of Pittsburgh. The population was 20,978 at the 2010 census. It is the principal city of the Johnstown, Pennsylvania, Metropolitan Statistical Area, which includes Cambria County...
and Altoona
Altoona, Pennsylvania
-History:A major railroad town, Altoona was founded by the Pennsylvania Railroad in 1849 as the site for a shop complex. Altoona was incorporated as a borough on February 6, 1854, and as a city under legislation approved on April 3, 1867, and February 8, 1868...
. As a digital station, WSPU had used a large UHF 15 transmitter at the location of the original low-VHF
Band I
Band I is the name of a radio frequency range within the very high frequency part of the electromagnetic spectrum.Band I ranges from 47 to 88 MHz, and it is primarily used for radio and television broadcasting....
broadcast tower, leading to localised problems with terrain shielding which interfered with UHF reception in State College itself. Relocation of the main transmitter would have interfered with the station's ability to serve the other two communities. Addition of a small (50 kW) synchronised digital TV transmitter in State College, on the same frequency as the main UHF 15 signal, proved a means to improve reception; further improvements would be possible by adding small co-channel 50 kW transmitters in each community to be served.
ATSC released standards on September 25, 2004 as guidance on the design of multiple transmitters, single frequency networks and multiple frequency networks. The new 2004 standards included:
- A/110A, "Synchronization Standard for Distributed Transmission, Revision A"
- A/111, "Design of Synchronized Multiple Transmitter Networks"
Technical issues addressed included that of synchronisation between transmitters (GPS was used to supply a 1Hz and a 10 MHz reference frequency, as well as timing information) and precise control of transmitted frequencies (to within 1Hz). Identification for each individual transmitter needed to be embedded in the signal for troubleshooting purposes, yet the main data stream on every synchronised transmitter must be identical; this is done by adding a second, low bit rate spread spectrum
Spread spectrum
Spread-spectrum techniques are methods by which a signal generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth...
signal 27-30dB weaker than the main signal. As this "watermark" identifier is buried under the stronger main signal, multiple repetitions of this same identifier could be received and summed in order to provide a readable version of the watermark to broadcast technicians. A standard receiver, meanwhile, would see the same signal from all transmitters by design.
The generation of non-MPEG data carried as part of the transport layer
Transport layer
In computer networking, the transport layer or layer 4 provides end-to-end communication services for applications within a layered architecture of network components and protocols...
(such as the position of transmitted frame sync, or the initial state of trellis encoding devices) would also have to be matched exactly between every synchronised transmitter. Even though this data is discarded after the received signal is demodulated, any mismatch could create interference between the various co-channel signals. An extra “operations and maintenance” distributed transmission packet (OMP, packet identifier PID:0x1FFA) would need to be added to the ATSC data at the studio and used to control various parameters needed for configuration and synchronisation of the individual transmitters.
The location, directional pattern and power levels for each of the transmitters would also have to be very carefully chosen, as the ATSC system is subject to very strict limits on the maximum time difference between arrival of multiple versions of the same signal at the receiver. In problem reception areas, significant improvements could be obtained but careful design would be required to operate multiple co-channel transmitters without destructive interference.
Further tests run by Telemundo
Telemundo
Telemundo is an American television network that broadcasts in Spanish. The network is the second-largest Spanish-language content producer in the world, and the second-largest Spanish-language network in the United States, behind Univision....
owned-and-operated station
Owned-and-operated station
In the broadcasting industry , an owned-and-operated station usually refers to a television station or radio station that is owned by the network with which it is associated...
WNJU-TV, Ion TV and broadcast tower owner Richland Towers using one main New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
transmitter and a Times Square
Times Square
Times Square is a major commercial intersection in the borough of Manhattan in New York City, at the junction of Broadway and Seventh Avenue and stretching from West 42nd to West 47th Streets...
fill-in DTS secondary transmitter in 2007 indicated that, of fifteen test sites for reception of the station in New York city, 40% would obtain a substantial improvement in signal by the addition of a second transmitter to the existing station, while all but one would receive at least the same signal quality as was observed without a distributed transmission system. New York's Metropolitan Television Alliance
Metropolitan Television Alliance
The Metropolitan Television Alliance, LLC was organized in the wake of the loss of the transmission facilities atop the World Trade Center in 2001. Its mission is to identify, design and build a facility suitable for the long term requirements of its member stations to meet their over-the-air...
was to run similar tests, but on a larger scale, in 2007 and 2008.
Regulatory issues
While the US Federal Communications CommissionFederal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
has supported DTS in principle since 2004, an FCC call for public comment at the end of 2005 garnered a wide spectrum of responses in early 2006, ranging from strong support by groups such as the National Association of Broadcasters
National Association of Broadcasters
The National Association of Broadcasters is a trade association, workers union, and lobby group representing the interests of for-profit, over-the-air radio and television broadcasters in the United States...
to widespread opposition by groups who advocate the free use of "white spaces" (unused broadcast frequencies) for non-broadcast purposes such as wireless data.
The FCC granted six-month special technical authority to WTVE
WTVE
WTVE, Channel 25 , is a Reading, Pennsylvania television station that has been in operation since May 4, 1980 Its schedule consists mostly of infomercials and paid religious programs. It also simulcasts Real Politics Live and Richard French Live which are produced by sister station WRNN in...
Reading, Pennsylvania
Reading, Pennsylvania
Reading is a city in southeastern Pennsylvania, USA, and seat of Berks County. Reading is the principal city of the Greater Reading Area and had a population of 88,082 as of the 2010 census, making it the fifth most populated city in the state after Philadelphia, Pittsburgh, Allentown and Erie,...
in December 2006, allowing it to operate a distributed transmission system on an experimental basis but did not authorise the systems on any permanent, licensed basis at that time.
An FCC-sponsored test market exercise in Wilmington, North Carolina
Wilmington, North Carolina
Wilmington is a port city in and is the county seat of New Hanover County, North Carolina, United States. The population is 106,476 according to the 2010 Census, making it the eighth most populous city in the state of North Carolina...
shut down all analogue full-power commercial broadcasts at noon on September 8, 2008. While a large number of the resulting calls from viewers were straightforward questions about installation of antennas and converters, or the need to scan for channels before being able to watch digital television, hundreds more were about a more intractable problem. Viewers of longtime full-power low-VHF broadcasters like WECT
WECT
WECT is the NBC-affiliated television station for the Cape Fear and Sandhills areas of North Carolina that is licensed to Wilmington. It broadcasts a high definition digital signal on UHF channel 44 from a transmitter southwest of Winnabow. The station can also be seen on Time Warner and Charter...
(NBC
NBC
The National Broadcasting Company is an American commercial broadcasting television network and former radio network headquartered in the GE Building in New York City's Rockefeller Center with additional major offices near Los Angeles and in Chicago...
6 Wilmington), a signal which in its analogue form reached to the edge of Myrtle Beach
Myrtle Beach, South Carolina
Myrtle Beach is a coastal city on the east coast of the United States in Horry County, South Carolina. It is situated on the center of a large and continuous stretch of beach known as the Grand Strand in northeastern South Carolina. It is considered to be a major tourist destination in the...
, could no longer receive the station - even with the converter and proper antenna installation. The move to UHF 44 and a different transmitter site had substantially reduced WECT's coverage area and, for many who for many years were on the fringes of the analogue NBC 6 signal, WECT was no more.
On November 7, 2008 the FCC issued an order approving the use of distributed transmission systems by terrestrial DTV broadcasters, subject to various restrictions. This allows broadcasters to apply for DTS facilities to cover the area once covered by analogue TV, while not expanding coverage beyond the existing analogue coverage area. It also prohibits a broadcaster "cherry picking" a coverage area in such a way as to cover urban areas while leaving rural viewers with no signal.
This waiver has come too late to allow the newly-proposed DTS facilities to be constructed and operational before the federally-mandated 2009 analogue shutoff.
The Consumer Electronics Association
Consumer Electronics Association
The Consumer Electronics Association is a standards and trade organization for the consumer electronics industry in the United States. The Consumer Electronics Association is the preeminent trade association promoting growth in the $173 billion U.S...
and CTIA
CTIA
CTIA may refer to:* Color Television Interface Adaptor, a custom chip inside early Atari 8-bit computers* CTIA – The Wireless Association* Cape Town International Airport...
proposed in December 2009 to force all stations to use this method, so that the companies they represent could use the remaining space in the TV band for mobile broadband
Mobile Broadband
Mobile broadband is the marketing term for wireless Internet access through a portable modem, mobile phone or other mobile device.-Description:...
. Unlike the digital television transition in the United States, they do not propose that stations be forced to pay for it however, much like the 2 GHz broadcast auxiliary service
Broadcast auxiliary service
A broadcast auxiliary service or BAS is any radio frequency system used by a radio station or TV station, which is not part of its direct broadcast to listeners or viewers...
was forced to move by the FCC, but only after the beneficiary (Sprint Nextel
Sprint Nextel
Sprint Nextel Corporation is an American telecommunications company based in Overland Park, Kansas. The company owns and operates Sprint, the third largest wireless telecommunications network in the United States, with 53.4 million customers, behind Verizon Wireless and AT&T Mobility...
) compensated broadcasters for the regulatory taking
Regulatory taking
Regulatory taking refers to a situation in which a government regulates a property to such a degree that the regulation effectively amounts to an exercise of the government's eminent domain power without actually divesting the property's owner of title to the property.-United States law:In common...
.
Individual broadcasters
In Puerto RicoPuerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
, Spanish language
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...
independent WSTE
WSTE
WSTE-DT is a full-power television station licensed to Ponce, Puerto Rico. It transmits on digital channel 7 over a four-site distributed transmission system.WSTE is owned by Univision and is operated by the network as well through WLII in Caguas...
7 "Super Siete" currently operates multiple analogue transmitters on the same frequency to cover various portions of the same island; this system has shown limitations due to interference between the transmitters if all are operational simultaneously. Use of a properly-synchronised digital DTS could help to reduce this interference.
In Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
, independent WTVE
WTVE
WTVE, Channel 25 , is a Reading, Pennsylvania television station that has been in operation since May 4, 1980 Its schedule consists mostly of infomercials and paid religious programs. It also simulcasts Real Politics Live and Richard French Live which are produced by sister station WRNN in...
is licensed
City of license
A city of license or community of license, in American and Canadian broadcasting, is the community that a radio station or television station is officially licensed to serve by that country's broadcast regulator....
to serve Reading
Reading, Pennsylvania
Reading is a city in southeastern Pennsylvania, USA, and seat of Berks County. Reading is the principal city of the Greater Reading Area and had a population of 88,082 as of the 2010 census, making it the fifth most populated city in the state after Philadelphia, Pittsburgh, Allentown and Erie,...
even though its primary audience is in Philadelphia
Philadelphia, Pennsylvania
Philadelphia is the largest city in the Commonwealth of Pennsylvania and the county seat of Philadelphia County, with which it is coterminous. The city is located in the Northeastern United States along the Delaware and Schuylkill rivers. It is the fifth-most-populous city in the United States,...
. A distributed transmission system now allows it to tailor its coverage area to improve coverage in areas where its signal is currently marginal
Rimshot (broadcasting)
A rimshot is a radio and television broadcasting term for a station that attempts to reach a larger media market from a distant suburban, exurban, or even rural location. The term is primarily used with FM stations, and mainly in North America...
.
In Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
public television WVPT
WVPT
WVPT is a public television station in Harrisonburg, Virginia. It is the PBS member station for the Shenandoah Valley of Virginia and West Virginia. The station is licensed to Staunton, and is located on the campus of James Madison University in Harrisonburg...
/WVPY operate a combined total of five additional on-channel synchronised transmitters to fill areas blocked by mountains from two main VHF/UHF transmitters; a set of US$
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....
100,000 synchronised digital transmitters can replace service from the same number of conventional analogue broadcast translators and also enable overnight datacasting
Datacasting
Datacasting is the broadcasting of data over a wide area via radio waves. It most often refers to supplemental information sent by television stations along with digital television, but may also be applied to digital signals on analog TV or radio...
of instructional materials to the area's 188 school
School
A school is an institution designed for the teaching of students under the direction of teachers. Most countries have systems of formal education, which is commonly compulsory. In these systems, students progress through a series of schools...
s.
In New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, Telemundo
Telemundo
Telemundo is an American television network that broadcasts in Spanish. The network is the second-largest Spanish-language content producer in the world, and the second-largest Spanish-language network in the United States, behind Univision....
affiliate KTDO
KTDO
KTDO, digital channel 47 , is a television station affiliated with Telemundo, serving the El Paso, Texas and Juarez Mexico television market. It is licensed to Las Cruces, New Mexico, it transmits in analog and digital...
proposes DTS as a means of pairing a low-power DTV facility currently operating in its community of license
City of license
A city of license or community of license, in American and Canadian broadcasting, is the community that a radio station or television station is officially licensed to serve by that country's broadcast regulator....
(Las Cruces
Las Cruces, New Mexico
Las Cruces, also known as "The City of the Crosses", is the county seat of Doña Ana County, New Mexico, United States. The population was 97,618 in 2010 according to the 2010 Census, making it the second largest city in the state....
) with a second facility atop a mountain overlooking El Paso, Texas
El Paso, Texas
El Paso, is a city in and the county seat of El Paso County, Texas, United States, and lies in far West Texas. In the 2010 census, the city had a population of 649,121. It is the sixth largest city in Texas and the 19th largest city in the United States...
in order to reach a wider audience.
In Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
, Anchorage MyTV affiliate KYES-TV operates with limited resources and equipment, covering a large and sparsely-populated area with many small broadcast translator stations. While broadcast signal synchronisation is not an issue (as the overlap between signals falls entirely into unpopulated areas), the ability to re-use multiple small transmitters may allow the station to avoid the cost of building one large, expensive main transmitter for its digital signal.
See also
- ATSCATSCATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
- Broadcast translator
- MediaFLOMediaFLOMediaFLO is a technology developed by Qualcomm for transmitting audio, video and data to portable devices such as mobile phones and personal televisions, used for mobile television...
(also a single-frequency networkSingle-frequency networkA single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.-Overview:...
, but using OFDM) - 8VSB8VSB8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM....