Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 11
WORKING PAPER 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 _ ~ ~ _ WORKING PAPER
OCR for page 12
WORKING PAPER 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. - 12 - WORKI NO PAP ER
OCR for page 13
WORKING PAPER 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. — 13 — WORK] NO PAP ER
OCR for page 14
WORKING PAPER 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. — 14 — WORKING PAPER
OCR for page 15
WORKING PAPER 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. ~ 5 - WORKING PAPER
OCR for page 16
WORKING PAPER 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. ~ 6 - WORKING PAPER
Representative terms from entire chapter: