IEEE TRANSACTIONS ON BROADCASTING, VOL. 38, NO. 2, JUNE 1992 111

SERVICE, SYSTEM, AND TECHNOLOGY CONSIDERATIONS

FOR SPACE-BASED INTERNATIONAL RADIO BROADCASTING

USED IN THE CONDUCT OF PUBLIC DIPLOMACY

T. F. Rogers

The International Radio Satellite Corporation

Washington. D.C., U . S . A .

Introduction

There are several activities now underway in Canada. Western Europe, and the United States that look to improving over-the-air radio broadcasting. It can now be seen, with considerable confidence. that ter- restrial and/or space-based transmitters could be employed at VHF/UHF/SHF (microwave), along with au- dio information compression, coding, and digital transmission techniques, to provide a better quality of service than is made available with terrestrial VHF FM transmitters, and a much better quality and reliability of service than with terrestrial MF AM transmitters.

Many, perhaps most, of these activities are concen- trating upon the delivery of exceptionally high quality, commercial, domestic. entertainment broad- casting.

These same techniques could be employed by those who now use surface-based shortwave (HF) radio broad- casting transmitters in the international conduct of public diplomacy.

This paper speaks only to the latter use of satel- lites and modern radio communications techniques. i.e., for the particular benefit of those government instrumentalities that wish to see their ability to conduct international public diplomacy radio broadcasting sharply improved.

Ddav’s Circumstances

Today‘s international radio broadcasters assist their governments in conducting public diplomacy by sending radio programs of speech and music to lis- tening audiences located up to many thousands of miles away. They do so with the best reliability. quality. and audience focus that the transmission medium, technology, and their financial resources allow.

They do so under the circumstances that manyhost of their listeners cannot afford to spend much for their radios: must use radios that are easily oper- ated: wish to listen to the broadcast programs with- in the privacy of their own homes: expect to be able to do so even if, at times, some others may not be in sympathy with their listening interests: and are being offered an increasing number of alternative listening and viewing opportunities.

The international radio broadcasting community uses surface-based hiah frequency/shortwave transmitters, and the shortwave reflecting properties of the Earth’s high altitude ionospheric plasmas and the Earth’s surface. to propagate their signals to great distances. The shortwave broadcasting art has been improving over a period of two generations and now.

at least for the major broadcasters, it is a truly powerful and sophisticated one.

But, now, shortwave has begun to approach some in- herent limitations. For even the use of costly re- mote repeaters and the most powerful transmitter arrays -- arrays in which several transmitters are used simultaneously on multiple frequencies -- oftentimes cannot improve signal receptivity enough because of (a) the inherent vagaries of the short- wave transmission medium and (b) the mutual inter- ference caused by signals arriving in the 1 istening areas from other countries that also employ powerful transmitting plants. As well, at times the broad- casters find that their signals are intentionally interfered with.

At best the reliability and quality of shortwave ra- dio broadcasting leaves a great deal to be desired. especially when compared with other media with which it must compete for listening audience attention. As a consequence, today‘s International shortwave audio broadcasters are losing the interest of some of their listeners, and they are apprehensive that this negative trend could continue.

Fortunately, it is now clear that a space-based UHF international audio broadcasting service, if proper- ly implemented, could go far toward relieving these grave shortwave difficulties. Such a service could be expected to increase the reliability, quality, and ease of reception to at least the level achieved in local over-the-air VHF FM broadcasting. It could be expected to approach the listening audience focus of powerful VHF FM terrestrial transmitters. It could be made very resilient to undue interference. And it should be able to do this for the entire world‘s international radio broadcasting community at a lower unit cost than it now pays for a lesser shortwave service.

Desirable Service Characteristics

What follows is an initial list of operating charac- teristics for an international service designed to meet the particular needs of all those engaged in using radio broadcasting to conduct public diploma- CY.

It should be noted that these characteristics re- flect the best that shortwave has come to offer -- a best that now can be greatly improved upon by the ability of space-based microwave transmitters to deliver signals of unexceptional reliability, quali- ty, and resi 1 iency via 1 ine-of-sight radiowave propagation directly to the radio in a sharply fo- cussed f ash ion.

At present this list reflects the professional ex- perience and judgement of the author (and several of

OO18-9316/92$03.00 0 IEEE

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his professional colleagues) and, as well, his un- derstanding of the consideration given to this im- portant matter in two related studies conducted by the National Research Council of the National Acade- mies of Sciences and Engineering in the United States of America. Final, detailed, service require- ments wi I 1 emerge from consideration thereof by the international radio broadcasting community in which schedule, financial, and other issues will make their influence felt.

o The service should be available to all of the countries of the world on an equitable. common car- rierlike, basis

o As with shortwave, all of countries of the world would be able to broadcast directly to the people in all of the other countries of the world on a re- ciprocal basis

o As with shortwave, it should be capable of pro- viding global coverage to nearly all populated re- gions outside of the far Arctic and Antarctic re- gions

o It should be available to the radio broadcasters. equitably, at the lowest unit lease price

o The basic channel-program service should be that of speech and music with, perhaps, various grades of service and, perhaps, some novel additional services

o It should have sufficient channel capacity to meet all of the needs of today's world-wide public diplomacy international radio broadcasters without mutual interference

o Signals should be able to focus upon a minimum audience area, with larger areas to be covered in multiples thereof

o It should have excellent short- and long-term re- liability -- equivalent, at least, to that offered in the United States and other developed countries by local over-the-air VHF FM radio broadcasting

o As with high effective radiated power shortwave, it should not be easily vulnerable to natural or manmade interference

o As with shortwave, listeners should be able to receive the broadcast programs within the privacy of their own homes

o A range of radio models should be available, with different performance and price levels, and with at least one of low initial and continuing cost, and easy operation, to meet mass market needs.

Service Impact

While this paper is concerned with the provision of an improved international radio broadcasting ser- vice, it is appropriate to say a few words about the most fundamental consequence of such a service be- coming available: the impact that it would be ex- pected to have on the world's listening audiences and the political value of this impact.

In time, manyhost listeners should have an extra- ordinary menu of listening opportunities made avail- able to them. At a very modest cost, and with ease and comfort, they would be able to become acquainted with the interests, activities, and aspirations of peoples, and policies of governments, up to half the world away. This should make for better understand-

ing of and. in time and at the margin, a more ready acceptance of. and empathy for, their fellow men and women around the globe. And it could foster more international political study in the world's schools and universities.

Hopefully, from the viewpoint of the United States of America and very many other countries. all of this should assist in the spread of pluralism and democracy. and thereby encourage global political stability, and social and economic progress.

able Svstem Characteristics

Two system acquisition-operation conclusions emerge from a consideration of these service characteris- tics:

o If they are achieved, o r even closely approached, the public diplomacy international radio broadcast- ing community would experience a long-awaited pro- gressive transmission revolution and, therefore, a serious effort must be mounted to see that this comes about:

o But a service with these characteristics can be provided only if the system plans are sound and if these plans are properlv implemented.

It must be appreciated by all who have a serious and responsible interest in the future prospects for the conduct of public diplomacy through the use of space-based transmitters that there is no way that the kind of system needed by the international audio broadcasters can be acquired and operated "on the cheap". It cannot be done with surface-shortwave, and it cannot be done from space.

There may well be significant markets for relatively modest capacity, relatively modest signal strength, and relatively modest coverage area, space-based commercial radio broadcasting services. Those who judge that this is the case (and the author does not consider himself competent to make such a commercial business judgement) should feel encouraged to ascer- tain if it is indeed the case. And, if made econom- ically available, they certainly could have appeal to governments for the conduct of some of their ac- tivities.

But I t is important that any such commercial enter- tainment service not be confused with the fundamen- tal kind of service needed by the VOA's, the BBC's, the Radio MOSCOW'S, .... of this world. For each such public diplomacy international radio broad- caster -- the specific. kind of broadcaster being considered here -- is charged by its government with a most serious responsibility: to assist its govern- ment in advancing its country's perceived national security interests. And for those who might consider the use of a radio broadcasting service put in place to meet the needs of commercial entertainment inter- ests for use in the conduct of public diplomacy, it would be well to keep in mind the words of Robert B. Reich who recently observed (in "The Work Of Na- tions", Alfred A. Knopf, New York, 1991; page 243): "In the life of a nation, few ideas are more dangerous than good solutions to the wrong prob- 1 ems. "

The public diplomacy international shortwave broad- casters now have a half-century of experience to draw upon in deciding what radio broadcasting ser- vice characteristics are desirable in order for them to conduct their activities most effectively and ef- ficiently.

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For instance, the transmitters employed. shortwave or UHF, must be sufficiently powerful ones -- just as, for instance, must those employed for the OMEGA global navigation system. or for the surface seg- ments of the NASA deep-space communications network: or for strategic early warning radars, ... . Today's more powerful individual shortwave transmitters em- ploy final power amplifiers with average power out- puts of some 500.000 watts. The sideband AN power can double this power output. Oftentimes two or more of these transmitters are employed simultaneously to reach particularly important listening areas. And these power amplifiers drive antennas with gains ap- proaching 200X. Thus, it is not unusual for a power- ful shortwave plant to broadcast toward a given lis- tening area with some 200 million effective radiated watts of radiofrequency power.

It is important to appreciate that there are no lim- itations upon shortwave flux density, i.e.. watts/ square meter, in the listening area. Like the use of the radiowave spectrum for radio astronomical scien- tific studies, public diplomacy radio broadcasting inherent 1 y requires "cl ear channels" or something close thereto. And it has been able to operate with- out such flux density limitations for the last 50 years.

While the performance of today's most powerful shortwave transmitters approach "the knee of the curve" insofar as prospects for their true improve- ment are concerned, it is possible for a relatively rich country to increase its shortwave tranmitters' effective radiated power even though it "beggars its neighbor" in so doing by increasing the potential for radiofrequency interference. For instance, a few years ago the National Research Council observed that, were the Voice of America to endeavor to meet its full shortwave broadcasting requirements, it should consider employing some shortwave transmit- ters with effective radio frequency power Outputs approaching 10,000 million watts. While, in the short run, this would provide it with a distinct advantage. it would come at a considerable financial cost and could raise some serious longer term is- sues. Thus the great inherent appeal of space-based radio broadcasting, which can see many more channels made available with much less effective radiated power. (See below.)

In this context, and in order to meet the desirable service characteristics outlined in the previous section. the following system characteristics now appear to be indicated:

o A few sophisticated and powerful geostationary satellite transmitters would be employed; they would be inter-connected y& direct satellite-to-satellite circuits and/or surface relays

o They would be UHF transmitters, operating prefer- ably in the 1.5 GHz "L-Band" region of the electro- magnetic spectrum: altogether, they would require the order of 10 MHz of radiowave spectrum and, as in the case of shortwave, without limitations placed upon the broadcast power surface flux density

o They would be sized so as to provide direct-to-the radio reception with the lowest priced radios like- ly to be used, and with enough effective radiated power to surmount foliage and building wall excess radiowave attenuation and any undue electrical or other signal interference

o Each transmitter would have a capacity of up to 100s of individual audio channels, each of which could provide up to the equivalent of digital com- pact disc (CD) audio quality

o Each would have a number of narrow transmitting radiation patterns (beams), some fixed and the oth- ers switchable and steerable: the minimal coverage area for each beam could be as small as 10.000- 100,000 square miles, with aggregations of beams used to cover larger areas

o Keeping in mind the absolute necessity to provide an adequate service even in the event of attempts by one or more governments to hinder "pub1 ic diplomacy" broadcasting, under special circumstances considera- tion may be given to the use of surface signal re- peaters o Speech and music information compression tech- niques would be employed so as to minimize the chan- nel bandwith and carrier-to-noise ratio required

o Digital transmission would be used, with suffi- cient appropriate coding, to ensure excellent relia- bility and quality of the received signal

o Each government broadcaster could employ its own up-link access to the orbiting transmitters, and/or employ a few central, and particularly sophisticated and powerful, system access links

o Most of the UHF-digital radios would be small, easily transported and tuned, and have small anten- nas which could be easily directed toward the orbit- ing transmitter

The RADIOSAT-INTERNATIONAL UHF space transmit- ters were initially sized so as to expect to have an end-of-life, on-beam, radio frequency power output of some 10 watts per channel. Were a maximum of. say, 10 channels (out of the 100s to be made availa- ble) to be broadcast from any one of its several 10s of beams, each of which would be expected to have a maximum gain of some 300,OOOX. then the effective radiated power output of that beam would be some 30 million effective radiated watts. Thus, the maximum single-beam radio frequency power output for 10 aud- io channels would require much less effective radi- ated power than that of a single transmi tterhingle audio channel surface-based shortwave transmitter. (Modifications in some of these initial figures, re- lated to a lower required EIRP, now seems to be pos- sible.)

Of course, careful transmitter filtering, and the relatively small and sharply confined surface radia- tion "footprint", would suffice to ensure that there would be no serious interference problems created for other electromagnetic services outside of the allocated broadcasting band.

Techno1 ow-Re1 ated Paci nq Matters

Some matters are more important than others when considering the time and difficulty associated with bringing the space-based international radio broad- casting service discussed here into being.

Perhaps the most fundamental and relatively immedi- ate one is the allocation of an appropriate portion of the electromagnetic (radiofrequency) spectrum to this service. This issue is expected to be addressed at the 1992 World Administrative Radio Conference (WARC).

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AI1 of the initial system parameters appear to lie within today's technological "state of the art". But (A) two of them are, perhaps, close to that edge. and will take a great deal of attention. And (B) there are two others that are related to the intro- duction of the new technology that must be given special consideration:

A L

o The space transmitter antenna must, of necessity, be relatively large and sophisticated. RADIOSAT-IN- TERNATIONAL initially considering the use of a para- bolic reflector with a diameter of some 50 meters (160 feet). While unusually large in absolute dimen- sion, its diameter-to-wave-length ratio (the funda- mental determinant of its required precision) of 5.000 centimeterd20 centimeters, i.e., 250X. would be only marginally larger than the U.S .A . Federal Government's (NASA's) Advanced Communications Tech- nology Satellite (the ACTS R & D satellite). The diameter-to-wavelength ratio of the latter's multi- ple spot-beam transmitting antenna reflector is 3 . 3 meters (330 centimeters)/l.S centimeters, i.e., 220x.

Nonetheless, there are reflector construction, pack- aging, launching, and unfurling technological chal- lenges, and associated beam forming and precision Earthward-pointing challenges. To the extent that EIRP requirements can be reduced, so will these challenges and their related financial costs.

o There are no apparent serious technological chal- lenges related to the microwave-digital radios. The challenge will come in producing, marketing, dis- tributing, and se1 1 ing them throughout the world at a price that the desired listening audiences would be prepared to pay and on a schedule that would meet the needs of the broadcasters and the financial backers of the spacebased service.

L o And there is another challenge -- one not of the technology itself, but one that would be a direct consequence of the introduction of this new technol- ogy. For speech and music programs then would be able to be delivered with a reliability and a quali- ty hardly dreamed of in the shortwave community, and with a geographical audience focus that is absolute- ly unimaginable there.

Therefore. those responsible for producing the pro- grams to be provided to the listening audiences would have to acclimate themselves to these new broadcasting characteristics and see that the char- acter of their programs match those of this new com- munications medium so that their share of market is maintained, and even increased, and that the messa- ges contained in the programs would be well re- ceived, intellectually and emotionally, by their listening audiences.

o Finally, the desirable service characteristics, perforce, require the acquisition of a technologi- cally sophisticated space segment. Obtaining the financing for the space segment could be the great- est challenge of al I .

While it can be readily shown that the unit cost of leasing channels from the common carrier-like ser- vice to be provided would be appreciably less than the full cost of an analogous shortwave service (setting aside the much better reliability, quality. and audience focus of the former) such a cost could

be beyond the financial capability of any one of to- day's government funded public diplomacy interna- tional radio broadcasters. Therefore, the required capital must be raised in a manner other than that employed to-day.

In searching out sources of such capital in the Uni- ted States. RADIOSAT-INTERNATIONAL has observed that the members of the private sector financial communi- ty spoken with so far are, understandably, essen- tially uninformed about international radio broad- casting organizations. activities and needs. This circumstance is not conducive to their making prompt, large, financial cmitments.

The international radio broadcasting community should appreciate that this matter needs particu- larly imaginative consideration.

Conclusions

The technology and operating characteristics of a space-based international radio broadcasting system designed to meet the service needs of the world's governments in the conduct of public diplomacy in an effective and efficient fashion now can be clearly seen.

These public diplomacy audio broadcasting character- istics must not be confused with those of space- or terrestrial-based commercial radio broadcasting.

The public diplomacy and the commercial requirements are inherently quite different and, therefore, it should come as no surprise that these different re- quirements must be met in quite different ways. As today with shortwave, meeting the world's public diplomacy radio broadcasting needs would require a more sophisticated space-based transmitting plant than that required for space-based domestic c m e r - cia1 radio broadcasting.

The international public diplomacy radio broadcast- ing cmunity now should position itself to assist in seeing that the kind of system and service it needs is forthcoming. For instance, it should see that appropriate frequency allocations, preferably at "L-Band". are made available at the WARC '92.

And, in general, it should position itself to see that it makes the transition from surface-based shortwave to space-based UHF in a sensible, paced, and prudent fashion.

The Author

The author has been associated with the development of new radio communications capabilities throughout much of his professional life.

He led the Communications Division of the Lincoln Laboratory of the Massachusetts Institute of Tech- nology that relayed television signals y& an orbit- ing satellite for the first time. Later, as an As- sistant, then Deputy, Director of Defense Research and Engineering in the Office of the Secretary of Defense, he was responsible for the development and installation of the world's first global (audio) satellite communications system, and the beginning of both mobile satellite communications and rapid, three-dimensional space-based navigation and posi- tion-fixing.

As Chairman of the Applications Committee of the

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NASA Space Program Advisory Council, as a member of several National Research Council committees, and as President of the Sophron Foundation, he has advised the National Aeronautics and Space Administration (NASA), the Voice of America (VOA), the Department of Comerce (DOC), the National Security Council (NSC), the Federal Communications Commission (FCC)

and the U.S. Congress on satellite communications matters .

He is a Fellow of the Institute of Electrical and Electronics Engineers and Chairman of the IEEE Aero- space R&D Policy Committee.