Telecommunications Research in the United States and Selected Foreign Countries: a Preliminary Survey. Report to the National Science Foundation (1973) / Chapter Skim
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TRANSMISSION, MODULATION/DEMODULATION AND CODING
TRANSMISSION, MODULATION/DEMODULATION AND CODING
Pages 103-151
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From page 103... ...
plant, will become predominantly digital. Digital multiplexing with access at appropriate bit rates for all existing services already exists in part.
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From page 104... ...
104 TRAFFIC 109 CALLS 1960 1970 1980 1990 TOTAL 94.0 159.6 -- TOLL 3.43 7.24 17.7 39.9 INTERSTATE 1.04 2.71 7.3 17.9 Figure l
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From page 105... ...
105 2000 r 1500 1000 500 CALLS/CAPITA/YEAR Total Toll • 1950 1960 4.1%/Year 189 7.4%/Year 49 1970 1980 1990 Figure 2
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From page 106... ...
106 400 300 200 O DC O 100 0 CARRIER GROWTH BY FACILITY J I I I I 1950 Open Wire YEAR 1960 J I L 1970 Figure 3
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107 FUTURE CARRIER GROWTH LLJ u cc PL o 15% 0 1950 1960 1970 1980 1990 Figure 4
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108 4 KHz TELEPHONE CIRCUITS IN THE BELL SYSTEM CO LLJ D O cc O LL. O CO 1000 r500 200 100 50 20 10 5 2 1.0 I 1950 1955 1960 1965 YEAR END 1970 1975 Figure 5
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From page 109... ...
109 FUTURE CARRIER GROWTH 111 0 c o 15% 5000 Miles of Waveguide 1950 1960 1970 1980 1990 Figure 6
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110 DIGITAL TRANSMISSION HIERARCHY 1.5Mb/s 6.3Mb/s 45 Mb/s 274 Mb/s LINES MULTIPLEXES BANKS AND CODECS Figure 7
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From page 111... ...
The advantages of digital plant and the ultimate limitations of the analog media point to this. The nature of new media, such as optical fibers, which may be important by the late l980's also favor the conclusion that digital transmission will prevail.
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From page 112... ...
112 ANALOG DIGITAL INTERFACING CLEVELAND TERMINAL hill' DSX-3 CLEVELAND JUNCTION L5 M34 WT4 N.Y.C. Figure 8
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From page 113... ...
113 MILWAUKEE L5 ANALOG DIGITAL INTERFACING CHICAGO TERMINAL Illl M34 T4 FEEDER CMG-3 CMG-3 CHICAGO JUNCTION DSX-3 Figure 9
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From page 114... ...
. Over the past decade, literally dozens of various lasers have been invented and developed to various stages of sophistication.
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From page 115... ...
The developers of this medium first faced the seemingly unsurmountable problem of reducing horrendous optical absorption losses. No more than five years ago the best optical fibers showed losses of hundreds of decibels per kilometer.
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From page 116... ...
IV. Modulators, Detectors, etc, and Optical Repeaters The simplest optical communication system must have, in addition to the source and the transmission medium, a modulator of some sort and a detector.
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Sol Buchsbaum Bell Telephone Laboratories Holmdel, N
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From page 118... ...
2./3/4 and the excellent report by the NAE Committee on Telecommunications, "Communications Technology for Urban Improvement."5 Alternative wide band communication transmission systems are discussed in this memorandum, namely, "optical transmission" applying coherent or incoherent light sources, optical planar dielectric waveguide technology (integrated optical subsystem) and fiber optics, as the basic components for wide band information transmission as compared to the circular low loss millimeter waveguide system being developed by the Bell Laboratories.
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From page 119... ...
Written (x l0l5) Long Total Distance Total Long Distance Long Total Distance 20 l.0 50 37 l00 l0 0 .56 0.33 9.0 l.5 230 25 0 .38 0.34 3.5 3.l 30 27 l5 l0 20 14 30 2l Table 2 CLASSIFICATIONS USED TO SUMMARIZE RESULTS OF THE STUDY Voice Telecommunications Telephone Mobile Radiotelephone Radio Program Transmission Video Telecommunications Videotelephone Closed Circuit and Other Special Television Services Television Program Transmission Record, Data, and Private Wire Communications Public Message Telegraph Teletype service (TWX and TELEX)
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From page 120... ...
120 PROJECTED INFORMATION TRANSFER VOLUME, 1970-1990 1020 ' TOTAL 10 19 18 10 « 1017 UJ Q 10 16 10 16 10 14 Voice Record Data and Private Wire - LONG DISTANCE Record Data and Private Wire 1970 1980 1990 1970 1980 1990 Figure l
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From page 121... ...
With the additional requirement on bandwidth, how much further will the present transmission networks be taxed, particularly if to this new "wired city" one adds additional network traffic such as the following: - community affairs traffic (newspaper-like) - educational traffic - medical traffic - community management traffic - transportation information traffic Where will this transmission capacity come from, or how will the introduction of the above-mentioned new wide band services be affected by insufficient transmission capacity?
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From page 122... ...
The major ones are: - Optical Fibers - Laser Links - Circular Millimeter Wave Guides - Light Pipes - Digital Microwave - Improved Satellite Links B Millimeter-Waves and Optical Transmission Communications engineers know that as the carrier frequency goes up, the amount of information that can be carried out on the carrier also increases.
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From page 123... ...
, where much work had been going on to take advantage of the coherent and narrow spectral distribution of laser beams, priorities for communications appeared to shift to the circular wave guides as the wide band transmission carrier, in spite of the recognized technological problems and inherent high cost of such systems. An excellent presentation of the Bell Laboratory efforts in optical communications technology is the paper by R
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From page 124... ...
D Optical Fibers for Information Transmission Although optical fibers have been in use for several years, their high attenuation (l000 db/km)
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From page 125... ...
It was Coming's belief, backed by a sizable expenditure on fiber optics technology, that the day will come when the fiber bundle will replace coaxial cable economically for a large number of video and other wide band applications. To provide the light beam, light emitting diodes (LED)
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From page 126... ...
makes possible direct optical detection to l.2 GHz.l4 IV. Program Considerations Programs to consider for monitoring and support to meet the needs for wide band services include: A
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From page 127... ...
Exploitation of higher and higher frequencies into the millimeter waves is well under way, but will entail expensive hardware and installation costs demanding almost from the beginning a high utilization or fill factor to be economical. For other practical reasons such wide band services provided by circular millimeter wave guide cannot readily be installed in built-up areas, areas which may be the early heavy users of video and high data rate services.
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Whether optical links are a viable approach to wide band services.
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From page 129... ...
J Bisbee, "Optical Fibers Joining Technique," BLTJ, 50, 3l53 (l97l)
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From page 130... ...
Early Bird started using a toroidal antenna pattern in which most of the energy was radiated away from the earth. Also, its bandwidth was only about l0% of that then allocated to communications satellites.
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From page 131... ...
Several dozen earth stations have been built, ranging in size from 25 foot to 97 foot diameter antennas, with the majority of them being of the smaller size. A substantial number of these stations are of Canadian manufacture, but for the most part the Canadian manufacturers are
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From page 132... ...
The Canadians and NASA are jointly working on an experimental "Communications Technology Satellite." Canada is to build the entire satellite, except for the 200 watt l2 gc power amplifier. NASA is to supply the Delta rocket and the 200 watt amplifier.
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D japan japan has plans for a communications satellite to be launched in the l977 period.
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From page 134... ...
Both the Molniya II and Statsionar use 20 repeaters for telephony each with l0 MHz bandwidth and 7 watt transmitter power, working into an antenna beam covering the visible earth plus a higher power, wider band repeater for TV. Using available characteristics of their earth stations and the above satellite data yields a repeater capacity of l20 one-way telephony channels, and a total capacity of l200 two-way telephone circuits, in addition to one TV channel.
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From page 135... ...
While the Franco-German Symphonie project has experienced difficulties, there is little doubt that these countries will eventually launch a communications satellite. While Symphonie won't be economically viable, future designs may well be economic, based on the Symphonie experience and also on their participation in Intelsat R&D programs (approximately 28%*
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From page 136... ...
Actually, of a total of over 80 Delta and Atlas/Centaur rockets launched since the launch of Early Bird (the first commercial communications satellite in l965) , only about 20% have been for commercial communications satellites.
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From page 137... ...
The l970's will see the application of communications satellites to domestic and regional use, and to special applications. As regards domestic service, Canada will have its system in operation by early l973; and the U.S.
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From page 138... ...
technology programs. The future application of communications satellites for special purposes - domestic, regional, aeronautical, maritime and broadcast - will result in a need for development and construction of new satellites.
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From page 139... ...
The U.S. leadership in satellite design is based on the existence of a number of highly experienced engineering and manufacturing teams built up over the past l0-l5 years for the development of NASA and Department of Defense satellites.
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From page 140... ...
From such programs will come the basis for future commercial satellite designs, as well as for new military and scientific satellites. Other governments are proceeding with their own communications satellite programs.
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From page 141... ...
I Antennas and General Station Considerations The first commercial earth station antenna, built by AT&T at Andover, Maine, was a 60-foot aperture horn which was scaled from the 20-foot aperture horn used in terrestrial radio relay stations designed for the Echo satellite experiment.
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From page 142... ...
Equipment is now fairly standardized and sufficiently reliable so that in most of the smaller stations it is technically feasible to employ one man per shift for two of the three shifts per day. The costs of earth stations having 97-foot diameter antennas have dropped from the range of $6 - $l2 million in l965 to $4 - $8 million in l969, and to $3 - $6 million at the present time.
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From page 143... ...
The paramps resulted in an increase in noise which was compensated by going from 85-foot diameter antennas to approximately 97-foot, which is the size now used in practically all earth stations. While such paramps are built mainly in the U.S., but also in Japan and Italy, and to a lesser extent in France and Germany (both of whom have only built for their own use)
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From page 144... ...
Therefore the multiplex equipment, IF amplifiers, modulators, demodulators, and up and down converters are all similar to those used in terrestrial radio relay systems and are built in most of the heavily industrialized countries of the world. The major difference in earth station equipment as compared to radio relay systems, is that greater flexibility is needed in the former as compared to the latter.
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III. Summary Satellite earth stations have generally reached a fair degree of maturity.
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From page 146... ...
l46 the number of stations and the number of channels in the system. Several U.S.
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From page 147... ...
communicating with the hospital in Fairbanks via the VHF voice channel on ATS-l. The objective of the scheduled one-hour per day "Doctor Call" was to determine the value of the reliable, but time-limited voice channel to provide health care services, and to provide some experience for the village medical aides operating with a small low-cost satellite terminal.
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From page 148... ...
43.6 22.0 l0/l/7l to 7/3l/72 l52.9 l4.8 (via HF) Service Unit Hospitals that serve only villages without satellite ground stations do not tend to use the satellite channels to other hospitals or major centers.
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From page 149... ...
The use of the 2.5 GHz, l5 watt transmitter and high gain antenna on the ATS-F satellite provides a much higher flux density at the ground receivers, and thus video signals as well as voice signals can be transmitted to the remote village sites. In addition to the extension of communications capacity to include television, schedule flexibility with ATS-F may permit appreciably more time to be devoted to Alaskan experiments, at least on occasion, than has been possible with ATS-l.
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From page 151... ...
Antenna gain - l4 db With a 3 dB transmission line loss, the ERP of the low power station is 6l.4 dBm.
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