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SECTION 1
GENERAL SERVICE AND SYSTEM CONSIDERATIONS
Since the Soviet Union launched its Sputnik satellite, there has been an
impressive growth in the use of space to improve the range, quality, and
reliability of radio communications. This use of space for communications
has been confined to long-hau] trunk and mobile services and indirect
broadcasting through the wedding of long-hau] satellite communication
circuits to local, over-the-air, and community cable television and radio
services. A few analytical studies of space-based direct audio broadcasting
possibilities were conducted in the 1960's and 1970's, and, the United
States and other nations have pursued the use of nations satellites to
provide video broadcasting direct to individual surface receivers. Yet
DBS-TV has not been realized.
Several times during the first 20 years of the space age, engineering
consideration was given to the design of a DBS-A system for use by the U.S.
government only. Early attempts made it clear that the technological
demands involved in the design of such a system, especially development
costs, were too high. Later, after potentially useful technological
development had progressed for other purposes, new engineering studies
looked more promising. Operations, cost, and financing were considered only
briefly because communications engineers were discouraged by the obstacles
posed by these factors.
Space technology has continued to advance and further developments
relevant to DBS-A are now expected. Operational (and perhaps, in a creative
sense, financial) circumstances have also changed. A growing number of
persons concerned with improving the prospects of international audio
broadcasting now believe that the correlation of forces at last appear to
favor the use of space soon.
Experts in the field, especially space and communications engineers,
must now appreciate the fact that the use of space for international audio
broadcasting will occur only if
l. A politically sensitive and operationally useful broadcasting
service can be developed and accepted as available to al] interested
government broadcasters on an equal basi s.
2. A sufficiently innovative and practical system can be designed to
provi de such a servi ce.
3. Novel means of financing are found to meet large acquisition and
ongoing O8M costs so as to allow the acquisition and use of the service at
an acceptab] e pri ce.
Any serious discussion of the practical possibility of replacing the
world's present surface-based, HE, ionospheric, shortwave methods and means
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with space-based direct audio broadcasting must begin with the realization
that all countries may not immediately embrace the new service. There can
be no assurance, therefore, that all HE shortwave radio receivers throughout
the world would be replaced by receivers designed to receive high-quality
signals broadcast by space-based transmitters.
If the geostationary orbit assumed here is to be used by space-based
broadcasting transmitters, international or at least regional agreement must
be sought and obtained regarding the orbital slots to be employed. And
agreement must be reached regarding the radiowave spectrum to be used and
the signal transmission and reception standards to be maintained. Such
agreements require that a large number of countries believe that their audio
broadcasting interests would be better served by a space-based
system-service than they are by systems available today or the
individual-nation surface-based HE systems projected for tomorrow. A
nation's decision to go with space broadcasting will be shaped by political,
operational, cultural, financial and economic factors affecting that
nation. Therefore, those giving serious thought to the acquisition of any
space-based systems for the delivery of any broadcasting services using such
systems, must be prepared to use space for audio broadcasting in a
particularly sensitive, equitable, innovative, and sophisticated fashion to
accommodate the factors that can be expected to shape the nation's decision
to broadcast via space. To do otherwise could easily delay the acquisition
of the system-service and jeopardize the likelihood that the service will
become reality in the predictable future. Many--quite possibly all--of the
wor1d's governments expect that planning the use of space broadcasting will
mirror the International Telecommunications Union Convention planning
agreement that states: "...the planning of...bands allocated to the
broadcasting service shall be based on the principle of equal rights of all
countries, large or small, to equitable access to these bands...."0
also
Widespread international support for a space-based system-service would
1. Involve a large number of active broadcasters, increasing the
likelihood of spreading the costs more efficiently over a large number of
system users and substantially reducing the unit cost to each.
2. Allow people throughout the world to learn much more about the
interests, values, and activities of other people in other countries.
The greater the coverage area, the lower the cost of its use, the
greater its listening acceptability compared to other competitive services,
6. World Administrative Radio Conference for the planning of the HE bands
allocated to the broadcasting service, First Session, Geneva, 1984
Report to the Second Session of the Conference, General Secretariat of
the International Telecommunications Union, Geneva, 1984; page 75,
paragraph 4. l. l.
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and the more equitably the service is made available to all countries, the
more likely it is that broadcasters throughout the world will use it, and
the greater its value to the people of the world.
The audio broadcasting community should plan from the beginning to use
space to provide a high-quality service that can be delivered to people
anywhere who are interested in access to the service. That would likely
include perhaps 99 percent of the world's population. The community should
be prepared to proceed without the active participation of some countries.
Those countries can continue to be served with HE broadcasting from
surface-based transmitters. Such leadership could contribute to what lan M.
Ross calls the use of "telecommunications...to improve the quality of human
exi stence . " ~
Service Requirements
The service requirements of a space-based broadcasting system include
the following:
l. The system should be capable of providing acceptable service to
essentially the entire wor1d's population.
2. Some countries may not initially wish to utilize the service, but
the system should be designed so the service would be available to all
countries for broadcast to all other countries on an equitable access and
price basi s.
3. The system should be reliable.
4. The system should be of generally high quality, with higher quality
available on demand for some areas and/or times at a price premium.
5. The system should place no more demand upon the listening audiences
than what is expected of listeners to today's local over-the-air AM and FM
audio broadcasting stations, including ease of moving receivers about;
locating, pointing, or adjusting antennas; using house electrical current or
batteries; and tuning from one station to another.
6. The system should be easily and effectively accessible through the
use of low-cost receivers that require little power to operate, use small
antennas, are easily tuned, can be used indoors and out, are readily
transported, and can be used while in motion.
7. "Telecommunications," lan M. Ross, Technological Frontiers and Foreign
Relations, National Academy Press, National Academy of Sciences,
National Academy of Engineering, Council on Foreign Relations,
Washington, D.C., 1985; pages 22-45.
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7. The system should be able to be used economically by broadcasters
who wish to direct one or a few programs toward relatively small audiences
located essentially anywhere on the globe. Broadcasters also should be able
to use the service to address relatively large audiences with multiple
programs, with the price of such service related to the audience area, the
number and duration of broadcasts, and their level of quality.
8. The system should have an acceptably low annual price for a standard
quality broadcasting channel.
9. The system should be installed and operated region-by-region as
dictated by political and financial circumstances.
JO. The system should use the electromagnetic spectrum efficiently and
without precluding the continued use of HE shortwave surface-based
broadcasting by countries wishing to do so.
General engineering-operational requirements for an initial space-spaced
audio broadcasting system can be inferred from these basic broadcasting
service characteristics.
The word initial should be stressed. Some system engineering parameters
cannot be defined until the following factors are clarified:
l. The number of programs to be broadcast simultaneously, their times
and durations, and the geographical size and location of the audiences.
2. The quality of service desired.
3. Any influence the ionosphere may have on coverage of specific areas
and signal fading and attenuation in others.
4. Foliage, building wall, and terrain roughness that can increase
red i owave p ath ~ os s.
5. The influence of electrical noise generated external to the
receiver, including commercial, industrial, and naturally occurring noise.
Judgments about the character and pace of related space and
communications technology developments must also be made. Such judgments
may need to be revised later. Large space-segment costs and financing must
be addressed, and perhaps an installation staging process may need to be
p ~ anned.
Finally, the prospect of space-based broadcasting--and the accompanying
financial costs--offers innovative engineering concepts to meet development
challenges within the constraints created by the financial means of many of
the system's potential users, both broadcasters and listeners.
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Engi neeri ng-Operational Characteri sties
The basic engineering-operational system characteristics follow:
l. Direct broadcasting coverage should be provided to most of the
world's population. Excluded are the areas within the Arctic and Antarctic
circles; the ocean, heavy jungle, extreme desert, and extremely high
altitude regions; and particularly difficult terrains where mountains would
shield a receiver from direct and diffracted field strengths radiated from
space.
The remaining 15 percent of the Earth's surface area of 200 million
square miles (3Q million square miles or 80 million square kilometers),
should be served. This area contains at least 99.9 percent of the world's
population. Particular provision could be made to serve such individual
locations as Point Barrow, Alaska; Got had, Greenland; Tromso, Norway;
Murmansk, U.S.S.R.; La Paz, Bolivia; Brasilia, Brazil; Alice Springs,
Australia; and one or more locations in the Artic and Antarctica that lie
outside these general boundaries.
Even areas weld within the Arctic and Antarctic circles could be served
if desired; a small Canadian government group now receives television via
geostationary satellite at 76° north latitude, only 900 miles from the
North Pole. Special provisions also could be made to serve surface ships
and aircraft making long transoceanic trips.
2. It should be a common user system.8 Without particular reference
to their specific organizational forms, it could be a system of the general
character as those provided by Intelsat, Inmarsat, Eutelsat, etc. (The VOA
has long accepted the practice of making some of its broadcasting facilities
available for use by other countries.)
3. While coverage of most of the globe should be the fundamental goal,
regional coverage would be quite acceptable, even perhaps preferable
initially. Provision could be made for region-to-region linkage, probably
via direct satellite-to-satellite optical or millimeter wave circuits in the
overal ~ system des i gn.
4. Al] locations within a large region should be served by broadcasts
by any country during the primary evening and morning listening hours,
eventually, all locations throughout the world should be able t~o~be so
served.
5. Transmitters in geostationary orbits should be employed to ease
receiver use where antenna directivity is employed in reception.
8. In the United States, called common carrier.
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6. Virtually lOO percent (99.9 percent +) overall, hour-to-hour
reliability should be maintained throughout the year. All factors that
could cause signal degradation below the minimum acceptable service
standards should be considered: the entire broadcasting plant, the
receivers in normal condition and sensible operating use, and all signal
transmi ssi on vagari es.
7. Three levels of service would be available for receivers meeting
minimal acceptance standards:
a. Basic service: 35 db signal-to-noise ratio (SIN) in a
post-detection bandwidth of 5 kHz, available in all broadcast channels and
to all receivers in all locations.
b. Standard service: 45 db SIN in a post-detection bandwidth of
5 kHz, available in nearly all locations.
c. Superior service: 50 db SIN in a post-detection bandwidth of
15 kHz, with provision for stereo operation, available in as many as lO
percent of the channels simultaneously.
8. The lowest reasonable overall broadcasting plant acquisition and
O8M cost should be sought. A single channel should ideally be supplied to a
broadcaster at the same unit price (or less) as an over-the-air local
service AM (MF) broadcasting channel, when normalized for comparable
coverage, duration, and quality of broadcasting service.
9. The lowest reasonable retail prices should be sought for fixed and
transportable Basic and Standard service spacewave receivers. A unit price
of a very few tens of dollars, at most, is preferred and should be
obtainable in large-scale production;9 mobile receiver vices could be
somewhat greater.
lO. The system should be installed and operated on a large regional
basis. It should also have sufficient flexibility to easily accommodate
increases in use and the interconnections of large regional systems.
ll. Frequency modulation or digital modulation should be employed to
minimize the need for in-orbit transmitter peak power, while providing the
large SIN and small interference levels required for high-quality service
and the most efficient use of the radiowave spectrum.
12. Techniques should be employed to minimize the overall bandwidth and
spectrum allocation required to meet the system capacity, reliability, and
quality requirements.
9. The potential market size would be hundreds of millions of receivers.
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Representative terms from entire chapter:
broadcasting service
