JPRS ID: 10368 WORLDWIDE REPORT TELECOMMUNICATIONS POLICY, RESEARCH AND DEVELOPMENT

• Document Type: CREST
• Collection: JPRS
• Document Number (FOIA) /ESDN (CREST): CIA-RDP82-00850R000500040014-7
• Release Decision: RIF
• Original Classification: U
• Document Page Count: 36
• Document Creation Date: November 1, 2016
• Sequence Number: 14
• Content Type: REPORTS

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- JPRS L/ 10368
4 March 1982
W~rldwi~~ Re ort
_ p
TEIECOMMUNICATIONS POLICY,
. RESEARCH At~D DEYELOPMENT
CFO~10 4/82)
Fg~~ FOREIGN BROADCAST INFOF~MATION SERViCE
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- JPRS L/10368
4 March 198 2
WORLDWID~ REPORT
TELECOI~IMUNICATIONS POLIC~I, RESEARCH AND DEVELOPMENT
(FOUO 4/321
CONTENTS
~AS IA
JAP AN
B riefs
NTT Policy on Satellites. l.
_ SUB-SAHARAN AFRTCA
INTE R-AF12I CAN AFFAI RS
APTU Favors AFSAT Satellite for 1985-1994
(Pierre Langereux; AIR ET COSMOS, 16 Jan 82) . . . . . . . . . . . . . . . . . . . 2
ZAI RE
B rie fs
Agreement With Burundi 7
ZIMBABWE
Briefs
~ooperation With Romanian Newa Agency 8
_ a _ [III - WW - 140 FOUO]
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~
WES T EUItOx E
I TALY
Microproceasor Applications :Ln Transmission Systems
' (M. Calabrese, et al.; EITT~.'RONTCA E TELECpMUNICAZZpNI~
Nov-Dec 81) . 9
Digital Radio-Relay Syatems at 19 Qiz in Urban Areas
(P. Amadesi, et al.; ELFTTRONICA E~LEOOMt~TICA.ZIONI,
Nov-Dec 81) 21
I
�
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JAPAN
BRIEFS
IvTT POLICY ON SATELLITES--Tokyo, 16 Feb (JIJI Press)---The quasi-governmental
Nippon Telegraph and T~lephone Public Cnrp. (NTT) has fixed its policy of
_ orbiting its large-capacity commLnications satellites using the space shuttle
of the U.S. National Aeronautics and Space Administration (NASA). Japan's communi-
cations satellites for practical i:se have hitherto been launched using domesti-
cally-produced rockets. NTT, the narion's telecommi.mications monopoly, will seek
approval of the Space Development Council before making a final decision on this
, score. Under NTT's plans revealed so far, it will blast off a one-ton communica-
tions satellite with a capacity of 25,000 telephone circuits in fiscal 1988 and
a four-ton satellite with a capacity of 100,G00 circuits around fiscal 1992.
Japan's fiscal year starts in April. NTT also plans to link via these satellites
telephone stations exclusively for long-distance calls to be set up in each
- pre~ectv.re by putting up antennas of four meters in diameter on the roofs of
these ~ta.tions. Another factor behind NTT's emerging policy of launching large-
capacity cor;imunications satellites is its strong wish to advance into data
communications business. [Text] [OW161451 Tokyo JIJI in English 1436 GMT
16 Feb 82]
r,g0: 5500/2123
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ZNTER AFRIGAN AFFAIRS
~
APTU FAVORS AFSAT ~ATELLITE FOR 1985-1994
Paris AIR ET COSMOS in French 16 Jan 82 pp 34-36
[Article by Pierre Langereux: "For a Regional Telecommunications Satellite in Af-
rica--The Cauntries of the APTU (African Postal and Telecommunications Union) in
Favor of an 'AFSAT' Satellite ror 1?85-1994"]
[Text] The study carried out, under the aegis of the Euroapace group, by a Euro-
pean consultant group com~rising Satel-Canseil, the ITM [Modern Industries and
Techniquea] company and the Bureau Yves Aoussin= concerning "the teleco~nimications
_and radio-television needs of the 13 Francophone member countries of the AP TU~ and
4 neighbo ring cotm tries2 capable of being fulfilled by a satellite during the
period 1985-1994," has shown that a regional teleco~mmunications satellite could be
effectively useful Co a good number of countries of the APTU.
The situation of the 17 African countr.ies concerned by the study (as well as that
of the other countries of Africa, for that matter) is characterized b,y two dominant
traits: low GNP per inhabitant (Er 1,000 to 2,400), and disturbing u~1~~.erequipment.
, According to Mamadou Simpore, secretary general of the APTL', '�ror more than SO mil-
lion inhabitants (including Chad) of the APTU member ~.ountries, there were in 1980
only 110,000 direct-exchange telephone lines, or about 1 line per 500 popula.tion!"
Moreover, this insufficiency reflects some striking inequalities. As regards the
APTU, nearly 80 percent of telephone subscribers are in the capitals, wi~h the rest
= distributed among a few large cities; but there are practical.l.y no teleconununica-
tions facilities in the rural localities and even fewer in eh~ suzroundi.ng country-
side. In addition, the existing lines are subject to a variable, but always high,
rate of unavailability.
The satellite may o~viously appear ambitiuus, even extravaganC, in such a context.
Actually, it is not so at all, Mamadou Simpore states, for three principal reasons:
the satellite is the only feasible means of transmission it~ Africa, it is less ex-
pensive than the other transmission means, and it can only have a considerable ef-
- fect on the underequipment situation of the African continent.
1. Beni.n, Central African Republic, Comores, Congo, Ivory Coast, Djibouti, tJpper
Volka, Mali, Mauritania, Niger, Rwanda, Senegal and Togo. Chad, a member of
i.he APTU, did not participate in the study.
2. Zaire, Ghuna, Kenya and Sierra Leone.
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Study of Needs
The Eurospace study, carried out in close coordination with the APTU secretariat
and the African national administrations in the AFSAT group, began with a broad
study of the needs of the countries concerned and the development they have
planned. Thus, the consultants evaluated the entirety of the telecomlr,unications
and radio-television needs of each country, and then they estimated the preportion
of service that could reasonably necessitate a satellite rather than conventional
_ telecommunications means (radio waves, cables, etc).
~ The needs were divided into three categories: international and national (�nter-
urban) public telecommunications, sudio and video broadcasting, and telecommunica-
tions in the rural environment--these last being distinguished from interurban
telecommunications for functional reasons. "
The domestic situation of the countries was evsluated in terms of four equipment
levels: good, poor, or nonexistent network connection, or no network (the most com-
mon situation). The first two cases relate to national interurban connections, and
_ the third and fourtk,, to rural connections.
For international telecoaununications, the calculation of the traffic and the number
- of international circuits took account of all the APTU member countries as we11 as
Cameroon, Ganon and Zaire. The assumptions made are an average annual increase for
the whole of the countries' internationalconnections, but varying with the period
- considered (15 percent from 1979 to 1990 and 12.5 percent thereafter). Particular
stimuli to:.ard modifications of routing, transmission and general operation were
also envisioned. Finally, for distribution of traffic as between earth and space
f"acilities, the study adopted the following criteria: routing of traffic to region-
a? satellite on demand assignment, and 100-percent direct point--to-point connec-
tions via satellite when the existing infrastructure is weak, or only 25-perrent by
such connections when there is radio or underwater cables.
For national telecommunications (not including rural), calculation of the circuit
needs was based on a spatial-temporal estimate of the subscriber demand and on
traffic Forecasts, and a proposal for a distribution between satellite and earth
facilities resulted. All localities that have telephone service or rare to have it
between now and 1985 were taken into consideration. For the period 1985-1994,
ttiere c~as close coordination with the na'.ional administrations as regards the rates
of growth considered in order to adapt th~�m to each country, sometime: with growth
rate differentiated as between the capital and the provinces. The number of tele-
phone circuits anticipated for needs other than telephony were estimated at an
overall 5 percent of the number of channels expected for public service. These
circuits will be for telegraphy, leased circuits, new services (telecopying, data-
transmissi.on, etc) and for replacement af certain pri�~ate networks that l:ave now
reached saturation.
An estimate of traffic distribution was made in function of distances, with the ex-
- isting facilities taken into account. When there ~re modern facilities (cables,
radio) between two Iocalities, it: was supposed that 75 percent of tre circuits
- would go by satellite beyond a distance of 500 km; 50 percent for distances of 100
_ to 500 km; and that below 100 km, there would be no cirr_uita via satellite. On i:he
other nand, when there are no moder~n facilities, all circuits would go via satel-
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L1CP_--1R all countries--beyond a dietance of 100 km. Another hypothesis grouped
the countries into three categories for the distribution as between earth and space
facilities, with a t-,~~avier weighting than before as regards the criteria other than
economic. This leads in particular to a more precise assignment of the distribu-
tions in terms of the distances.
For telecommunications in the rural environment (defined as the regions not pres-
ently served by the national telecommunications network), two types of installation
ar~ envisioned: in a locality for public service, and providing service ko all the
inrcabitants; or in the countryside, mainly for the benefit of the farmers. The in-
stallation strategy is the planned to have two phases: first of all, installation
of network access points consisting of a"rural communications office" equipped
with a telex and telephone, and pcssibly a community TVi center; and next, extension
of service to subscribers who might ~ncrease the pr~fitability of the system, with
more r.ur.i offices added, creation of small local r.ietworks, and installation of
networks in the countryside. The total operatia:~ (the two phases) would be aver a
, period of 5 to 7 years.
The forecasting or rural telephone traffic was done by two methods. The basic hy-
pothesis considers maximum geographical service ac the lowest cost, the objective
for 1994 being the serving of 1 percent of the rural population residing in the lo-
calities concerned, with doubling of use uver a 10-year period (1985-1994). Com-
plementarily, a survey was made of the needs for the entirety of the rur21 zones of
each APTU country as of 1994.
Total APTU Half-L~uplex and Via-Satellite Circuit Needs
Telephone 1985 1994
Half-Duplex V~a Via
Circuits Total Satellite Total Satellite
Internationa?. 600 400 1,300 1,000
Interurban* 9,600 4,200 19,999 8,400
Rural 5,200 1,900 31,000 11,000
Totals 15,400 6,500 51,300 20,400
a
Radio-Television 2 to II TV programs
10 to 20 FM-radio programs
Special service channels
*[Sourc~~ gives no note relating to this note reference.]
- It is proposed to meet the rura~ telecommunications and television needs nanly by
satellite, ex~ept in ~he smgll-size countries. This would lead, as from 1985, to a
cot?ununity tele~ommunications and TV service, in the proximity of a station installed
i~-~ each locality, and in 1994, to a distribution of the preceding service to the
other subscribers of the locality (by wire) and to those located outside (by radio-
telephone).
For audio and video broadcasting, the esti*.:~tion is more difEicult to make. The
countries were divided into two categories. Those that havF already chosen to
transmit radio-TV progran~s via satellite--by means of a leF.sed reFeater on an In-
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telsat satellite--are obviously in a very good position for extension of coverage
by way of an African regional satellite. For the large countries that do not ~res-
ently have a sizable radio-beam infrastructure, the satellite represents the most
effective means (in terms of cost and speed of service) for providing coverage of
the country. But ~his assumes a complementary equipment effo~t (earth transmitting
staticn, receiving stations, TV-FM transmitters, community receivers, etc) in order
to make the space investinent a profitable one. For the countries that already have
a radio-beam network that is dense or developing, the satellite obviously seems
less attractive. As for other countries of small territory, use of the satellite
does not seem justified.
Conclusions in Favor of the Satellite
The study thus concludes that for the 13 countries of the APTU, the interurban
half-duplex-circuit needscome to 9,600 in 1985 and 19,000 in 1994--a 7-percent rate
of growth. If Zaire is added, these figures are 11,600 and 23,000 half-duplex
circuits, respectively.
The eventual use of a regional satellite for the international traffic among the 17
countries studies (the 13 APTU countries and the 4 neighboring ones) corresponds to
a capacity of 400 half-duplex circuits in 1985 and 988 in 1994. As regards nation-
al (interurban) traffic, the initial estimates indicate about 4,200 half-duplex
circuits in 1985 and 5,900 in 1994, including Zaire. In the case of hypotheses
that further favor the ground-based systems, the tatal number of half-duplex cir-
- cuits still comes to 2,700.
Concerning rural telecommunications, the total half-duplex-circuit needs of the 13
countries of the APTU was estimated at 5,~00 in 1985 and 31,000 in 1994. Including
Zaire, these figures are 6,300 and 49,200 half-duplex circuits, respectively.
rltiiong these needs, the proportion of rural telecommunications that could go vi.a
satellite was estimated at 1,900 nalf-duplex circuits in 1985 and 11,000 in 1994,
which represents an average annual rate of growth of 19 percent. With ~aire, these
- needs reach 2,500 and 15,700 half-duplex circuits, respectively. This 19-percent
growth rate, which may seem high in comparison with the other categories of tele-
communications, actually follows from the tremendous rural-telecommunications lag
in Africa. The secretary general of the APTU recognizes, in fact, that a start has
to be made from nothirig in order to try to reach an "acceptable" situation around
- 1994--one which would still be only a 1-percent telephone density in certain local-
ities and even just 0.5 percent in others!
In the area of radio-television, where extreme infrastructural weakness is also
noted, the equipment effort to be made is consideraole. But it is presently imped-
ed by the lack of equipment, qualified personnel and financial means. The APTU
study concludes that "six countries of Africa--the Cpntral African Republic, Upper
Volta, rfauritania, Mali, Niger and Senegal--present very favorable characteristics
for use of the satellite for meeting their radio-TV needs, and that two other coun-
tries--Congo and Ivory Coast--despite the present or future large size of their
radio-beam network, could find use of a satellite an attractive alternative for de-
velopment of their TV-FM radio network." On the other hand, the APTU study rP-
cognizes that the other five countries--Benin, Comores, Djibouti, Rwanda and Togo--
could solve their radio-TV network problems without ~ecourse to the satellite.
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, Such are the results of the study approved by the Council of the APTU at Lome in
August 1981 and presented publicly for the first time at the recent Eurospace In-
ternational Conference by Mamadou Simpore, secretary general of the APTU.
These data now constitute the basis for new complementary studies recently ordered
from Eurospace, both by the APTU and by the Pan-African Telecommunications +.inion
(PATU), in liaison with the African National Radio-Television Union (URTNA). One
of the studies, for which a contract of Fr 2 million has been made, is an extension
to the scale of the PATU--which incorporates all the countries of Africa (including
those of the APTU)--of the telecommunicatiuns-needs study previously carried out by
Eurospace. The other is a parametric study concerning the feasibility of an AFSAT
satellite system covering the needs of the APTU and eventaully those of the PATU
also. This second study is presently financed ~o the extent of Fr 3 million by the
European Development Fund (EDF), but supplementary financing is expected from France,
Italy and Great Britain, to reach the Fr Fi million needed for carrying out the
' work. These new studies will be conducted under the direction of the European
Eurospace group, with the participation of the European Space Agency (ESA), the ITM
company and the Fr~nch National Center for Telecommunications Studies (CNET), as
- well as with the GTS (Great Britain) and Consultel (Italy) companies.
COPYRIGHT: A. & C. 1982
_ 11267
CSO: 5500/5665
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ZAIRE
_ BRIEFS
AGREEMENT WITH BURUNDI--Zaire/Burundi agreement on telecommunications. The govern-
= ment of the Republic of Burundi and the Executive Council of the Republic of Zaire
signed a formzl agreement on telecommunications at Bujumbura on 11 December. The
purpose of the agreement is to set up and operate a direct telecommunications link
between the two countries for tele~raphic services, telex, rented circuits, fac-
simile, data transmission and radiophototelegrams using available and future tech-
- nology. [Text] [Paris MARCHES TRQPICAUX ET MEDITERRANEENS in French No 1886,
= 1 Jan 82 p 39] jCOPYRIGHT: Rene Moreux et Cie Paris 1982J 9855
CSO: 5500/5658
~

~
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ZIMBABWE
, RRIEFS
COOPERATION WITH ROMt~NIAN NEWS AGENCY--Salisbury, 25 Feb (PL)--Representatives
from the News Agencies of Zimbabwe (ZIANA) and Romanian (AGERPR~SS) signed in
- this capital an agreement for the exchange of information. The agreement was
signed by the chairman of the amalgamated mass media of Zimbabwe Davison Sadza
and the Romanian ambassador to this country Petre Bla~ovici. Sadza said he hoped
the signing of the agreement would go a iong way to improve the Yelationship
between the two countries. In reply Ambassador Blajovlr_i said the signing was
a new step forward to improve cooperation between the two countries. [TextJ
[PA242130 Havana PRELA in English 2020 GMT 24 Feb 82]
CSO: SS00/5693
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ITALY
MICROPRUCESSOR APPLICATIUNS IN TRANSMISSION SYSTEMS
Turin ELETTRONICA E TELECOMUNICAZIONI ir. Italian Nov-Dec 81 np 241-246
- [Article by M. Calabrese, M. De Bortoli, G. Panarotto, G. Rocca and E. Thomas*]
- [Text] Summary--Microprocessor applications in transmission systems. This paper
illustrates the reasons in favor of the use of microprocessors in telecommunica-
tions transmission systems. After an overview of the possible fields of applica-
tion of these devices, together with the advantages and the cc~mpromises for a pro-
fitable insertion within the complete system, some applications in experimental
plants are described. In a modem for digital transmission at 140 Mbit/s rate, the
- microprocessor controls several fundamental parameters; in another application it
_ implements a new equalization algorithm and in a field trial (COS 3/FOSTER) it col-
lects the significant link parameters and processes them for the overall system be-
havior monitoring. A forecast is also presented on futu-e developments of these
applications.
1. Introduction
_ Many applications have been found for microprocessors in the telecommunications
field, especially wittiin the framework of switching installations.
Their introduction into transmission systems has been less immediate, though, main-
ly for two reasons: the analog nature of the signal to be treated, and the high
frequencies involved.
The digital transmission systems offer greater possibilities for insertion of mi-
croprocessor devices, since treatment of the signal is required at discrete in
stants--that is, the instants at which the decision is made.
* Dr of Engineering Mario Calabreses, p.i. [expansion unknown] Marco De Bortoli,
- Dr of Engineering Gianfranco Panarotto, p.i. Giovanni Rocca, p.i. Ernesto Thomas,
of the CSELT (Telecommunications Research ~nd Study Center), Turin.
~ Typescript received 23 July 1981.
This paper ~;as presented to the annual Congress of the AICA [Italian Association
for Automatic Calculation] at Pavia, 23-25 September 1981.
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[Jithin this framework., two types of application have been individuated, distin-
guished essentially by the different ratio between the processing speed of the mi-
cro;~rocessor used and the speed of transmission of the symbols:
1) processing of the signal in real time, for transmission systems of sufficiently
low ,speed;
2) management of the equipment through processing of statistical magnitudes and of
significant signals at low speed, both through control of algorithms and through
monitoring of the system's performance characteristics.
These two aspects are dicussed in detail in this paper. Several sets of equipment
built in the CSELT are described. For each of them, the purpose and the type of
processing done cn the signals are presented.
From the applications described, the advantages that can be obtained through this
type of approach are obvious, especially for experimental projects: for example,
the considerable flexibility in the various tests, because of the possibility of
doing things through mere changes o� the software.
2. Genera: Considerations on the Use of Microprocessors in Transmission Equipment
= The use of microprocessors in transmission equipment, in place of analog circuits
or the traditional logical circuits, is justified when one of the f~llowing condi-
- tions occurs:
a) real-time processing of the signal is very complex and must be done with a low-
- speed data flow. In this case, use of a microprocessor considerably simplifies the
hardware of the equipment, requiring from the software a part of the funct~~ions
that have to be carried out;
b) the problem arises of monitoring functional blocks of the transmission equip-
ment, through development of algorithms on low-speed signals. or of keeping the
performance charact~ristics of such ~.pparatuses under contr~l. In such case, in
addition to the advantages cited in paragraph a), use of the microprocessor gives
the control or management structure considerable flexibility, tliis being an especi-
ally useful characteristic when experimental equipment is developed.
Attention is now drawn to the two peculiar characteristics of microprocessor archi-
tecture: modularity of the hardware and flexibility of the software.
Current technology makes available a considerable number of components, capable of
carrying out complex and specialized opErations,that can be inserted into micro-
processor systems as peripheral equipment un the system buses.
Several components of special importauce in transmission systems can be taken as
examples. Analog-digital (A/D) and di$ital-analog (D/A) converters, which make it
possible to digitalize analog signals and restore the processing results iii analog
- form, are the necessary i.nterfaces between the microprocessor and the system.
In addition, if the processings are rather complex from the mathematical F~oint of
view, it is possible to insert into the system a multiplier or arithmetical pro-
_ cessing unit capable of carrying out the fundamental arithmetica..l operations auto-
nomously, even on numbers ex~,rCssed in floating point, and of doing the conversions
between that format and the entire format.
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A single well-organized system is therefore ~asily e~pandable, from the hardware
point of view, to meet the individual requirements and adapt the structure to new
situations that may arise from time to time it~ the experimentation.
As for the software, its task is to receive the signals and process them. Through
program changes, it is possible t~ modify the al~orithms, while by modifying the
data it is possible to vary the static parameters of the problem, thus adapting the
program to the specific application in the best way.
In cases in which the processing of the signal has to be especially fast, it is ad-
- visable to use bipolar microprocessors of the bit-slice ~ype instead of the more
usual microprocessors built with MOS [Metal-Oxide Semiconductor] terhnologies.
This choice has an effect on both the hardware and the software. The user does in
fact have to construct both the central unit on the basis of the individual compo-
nents and the set of instructions most appropriate for the application or. the basis
of the elementary operations of logical-arithmetic type defined within the individ-
- ual components (microinstructions). The set of instructions is defined by the us-
_ er by accurate analysis of the slgorithm to be developed and isolation of the most
elementary and repetitive steps.
This approach may prove considerably burdensom in cases where support instruments
are lacking, both for development of the software and for the checking-out of the
system; nevertheless, the advantages obtained in terms of processing speed are
notable.
2.1. Processing of the Signal
Some af the main considerations relating to transmission of the signals are digital
filtering, ad.aptive equalization, the algorithms for extraction of the synchron-
isms, estimation of channels not known beforehand, and coding and decoding opera-
tions.
These functions, usually carried ouL in analog mode or with dedicated logic, are
carried out by means of logical and mathematical operations done on the flow of the
signal samples taken at the symbol-transmission speed.
One therefore thinks immediately of the possibility of doing these operations with
microprocessors. There is, however, a limitation i.n their use for these purposes,
due essentisily to the reduced processing speed as compared with the transcnission
_ speeds usually used. The basic cause of this limitation lies in the complexity of
the a.lgorithms and in the mass of data to be treated, which necessitate use o� mi-
croprocessors for processing signals whose transmission speed does not exceed some
10 kHz.
In order to partly overcome that limit, it is possible to construct microprocessor
architectures in which each processor is dedicated to the carrying-out of a single
function, with considerable advantages in overall processing speed and therefore
with the possibility of applica~ion to systems of higher transmission speed.
In Chapter 4, there is described in detail, as an examrle of real-time precessing
of the signal, a nonlinear equalizer of the "Decision Feedback and Eeedforward"
type (Bibliography 2).
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The high number of processings to be done, which is connected with the necessity of
_ a certain speed of the data-flow to be treated, required the use of a microprocess-
of the bit-slice type.
It is interesting to note that this arrangement fu1J.y met the expectations as re-
gai�ds the flexibility of its use: it was in ract possible, solely with m~difica-
tions of the software, to test the algorithm ir. various condition$ of number of
cells and parameter values. It was also possible--aQain, solely with variations of

~ the software--to achieve a transverse linesr eQUalizer for the purpoe~ of comparine
the performance characteristics of the two eQUalizers.
- 2.2. Management and Con*.rol of the Systems
A different class of microprocessor applications is the processin� of the statisti-
_ cal parameter's connected with the information signal. Examples of these statisti-
cal magnitudes, which werE used in the systems illustrated later, are the mean
quadratic error and the average of the absolute values of the error encountered in
the decision-making organ.
By optimizin~ ~these magnitudes,.it is possible to control several parameters of
fundamental importance in the system, such as the coefficients of the adaptive
equalizer, the optimal ptiase for signal-sampling, the phase of the demodulator--for
e:cample, in AM-SSB (Amplitude Modulation - Single Side-Ban) systems that require
coherent demodulation.
_ The statistical magnitudes referred to above can be obtained with dedicater: cir-
cuits or by making use of the microprocessor's processing capacities.
In the former case, the magnitudes are calculated by the external circuitsusing the
in-line signals and are transferred to the microprocessor at lower speed. In the
latter case, they are generally determined by using a data flow obtained by sub-
- samplin~ of the in-line signal.
The experimentation done den~onstrates that statistical magnitudes calculated in
this way are equally significant for controlling the system's parameters, provided
that the time interval of their integration is suitably chosen.
In both cases indicated above, the microprocessor is asked to perform the task of
minimizing the statistical function, in accordance with the optimization algorithms
best~adapted to the situation in question, of establishing the values of the para-
meters under control, and as the case may require, of f~zrnishing indications of
correct system functioning to a local operator.
In Ch3pter 3 is presented a transmission system, at the rate of 140 Mbit/s, that
uses the microprocessor for management of the receiving terminal. The microproces-
sor is used for control of the process of adaptation of the coefficients of the
transverse equalizer that has to compensate for the cable distortions, for control-
ling the decision thresholds and for recovery of the optimal sampling instant.
- Use of the microprocessor has proved especially a~'~rantageous because it has given
the designers considerable experience on the validity and the limits o� all the al-
ternatives examined, testing them directly in the installations in real conditions
and not only by computer simulation of th~~m.
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A final field of use of this type af device is general monitoring of the correct
functioning of the system and of its performance characteristics. For such pur-
- poses, the microprocessor does not have to have special speed characteristics but
only suitable peripheral equipment capable of collecting the magnitudes to be ex-
amined and providing them to the user in the m~st appropriate forn~, and, as the
case may call for, transmitting them to collection and supervision centers, as in
the remote monitoring systems, for example.
Microprocessors offer the advantage of being able ta coordinate collection of the
most significant data on the proper functioning of the ~ystem and do the process~
ing of them, thus furnishing a complete and organic picture of the parameters to be
monitored and facilitating recognition of causes of malfunction.
This methodology is especially useful in the perfecting of experimental systems and
in character.ization of them.
In Chapter 5 is presented, as an example of this approach, the system for acquisi-
- tion and processing of the measurement data of the ez;perimental optical-fiber
transmission installation COS 3/FOSTER. In this system, which has the task of re-
~ lating deterioration of transmission quality to the performance characteristics of
components of fundamental importance, it has been possible to distribute the pro-
cessi:ig capacity to the individual terminals that are geographically dispersed,
thus decentralizing the monitoring and treatment of the magnitudes measured and re-
serving to the centralized control unit the job of gathering and correlating the
data.
3. Microprocessor Inserted into the Hybrid-Type 140 Mbit/s Digital Transmission
System
3.1. Objectives of the Application
The microprocessor application concerns adaptive control of the multilevel receiv-
ing tenninal of th:~ "hybrid"-type 140 Mbit/s digital transmission system developed
in the CSELT (Bibliography 1).
This system provides �or the insertion, between two digital regener.ators, of a num-
ber of analog repeaters that only malce it possibl~ to recover the attenuation in-
~roduced by the cable into the useful signal band ~Figure 1): the effects of dis-
equalization of the signal and of the related variat~~:~ accumulate along the n
sections of analog repeti.tion fallinQ between two digital terminals.
It is therefore necessary to provide, for a high number of sections, an adaptive-
control device that makes it possible to re~over the variations of the system's
characteristics in time, maintaining satisfactory and constant transmission qual-
ity.
For this purose, the microprocessor device inserted into the receiving terminal
(Figure 2) examines the signal received, taking a sample out of every 1,000, and
calculates an error function (EF)*, by minimizing which it controls:
* The EF is defined thus: N iE~~li - iri~~ in which li is the level of the sym-
- bol received, lri is the relative reference level, and N is the base o� integra-
tion of the error function.
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1) the phase of sampling ins~ant ~T;
- 2) the values o~ the decision thresholds;
3) the coefficients of the adaptive transverse equalizer (ETA).
(1) ~1)
RI/ETITOHE NtNNERICO RIPETITORE NUMERICO i
p R.iT. p - - p n.ITr p
RIPE'fITONI ANAIOCICI
~2~
l _ J eeaz
~
~ 3~ SE210NE DI RIGENERAZIONE NUMERICA
Figure 1. Block diagram of the hybrid transmission system
Key:
1. Digital repeater 2. Analog repeaters 3. Digiral regeneration section
/ \ (2) (3) (4) (S) (6~ (7
\ 1 / EQUALIZ� F1U350
FILTHO
FLUSSO p' + SOIMMA ZqTORE ~~~0� DEC~- OATI
OATI q~CEZ10NE - TORE TRASVER NATORE SOAE DECISO
DALLA SALE
IINEA
~8~
COEfF. CAMPIO�
E.T.A.
B NATONE
ANELLO AD
~ ~ AGGANCIO ~ 1 O ~ ~S~~TIVO A
DI FASE MICROVFOC.
~ SEGNALE SOTTOCAMV.
~12) , ~11)
SFASATOHE f1/t7
VAHIA9ILE 1I1000 ~
FREOUENZA DI
CAMPIONAMENTO SOGLIE 01 OECISIONE
(13)
Figure 2. Block diagram of the receiving terminal of the 140 Mbit/s system
Key:
1. Data flow from line 8. ETA coefficient
2. Reception filter 9. Phase-hookup ring
3. Adder 10. Microprocessor
4. Transverse equalizer 11. Signal subsampled
5. Sampler 12. Variable phase-shifter
6. Decider 13. Sampling frequency
7. Data flow decided on 14. Decision thresholds
= 3.2. Reascns for Adoption of a Microprocessor
The device for control of the receiving terminal must carry out logical and arith-
metic functions of a certain magnitude, in accordance with algorithms that are
computer-simulated, only on the basis of simplified and therefore limiting wor;cing
hypotheses.
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In the development phase, it is therefore indispensable to be able to make use of a
device ir,~serted into the real terminal and making it possible to modify easily boll~
the test algorithms and the parameters relative to them.
- A device built with a microprocessor meets these requirements, inasmuch as the
hardwarestructure remains unchanged, while the behavior of the device depends on
the ccntent of the program memories (algorithms) and data (parameters). In addi-
tion, the various buses (addresses, data, control) existing in the microprocessing
structure permit easy connection of the most diverse peripheral equipment, which
makes possible rapid execution of ineasurements, recording, processing and presenta-
tion of the data of preeminent interest.
With the algorithms and the relative parameters defined, a aimpiified device is in-
_ serted ~n the terminal; this device too is built with a microprocessor, both for
easy transposition of the original device and because the complexity of the cir-
cui~, dimensions, construction time, power consumption and costs are decidedly com-
petitive with those of the alternative analog device built with traditional-logic
circuits.
4. Microprocessor for Development of a Nonlinear Equaliz~r
The application consists in the construction, by means of a microprocessor, ~f a
type of nonlinear equalizer recentiy designed in the CSELT (Bibliography 2).
This type of equalizer* unites with the principle of backward reaction of the deci-
- sions decided on (decision feedback) the forward reaction of the same symbols (de-
cision feedforward), thus permitting nearly total cancellation of the interfering
signals, even in the presence of strongly distorted channels.
_ The equalizer can be inserted into the receiving terminal of a digital transmission
system in accordance with the block diagram of Figure 3.
(1) (2) (3) (4) (S) (6)
SEGNALE FILTRODI CAMVIO� fILTRONON DECISORE SIMBOL
DALLA RICE210NE NATORE LINEARE OECISI
LINEA
~ ] ~ FRE~UENZA DI CAMPIONAMENTO ~
Figure 3. Block diagram of receiving terminal of a digital transmission system
with insertion of a nonlinear filter
Key:
1. Signal from line 5. Decider
2. Reception filter 6. Symbols decided on
3. Sampler 7. Sampling frequency
, 4. Nonlinear filter
~ * Patents filed.
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The equalizer considered, the block diagram of which is given in Figure 4, presents
two parallel paths: the upper one has the purpose of correcting the precursor of
the input wave form, and the lower ane, the relative tails.
h
~
,
Kp Kp KO
D + p + + p B
~ 4 f
Kp�
- SF~ T T - T +
O
A ~ ~ -
+ + T i D
~ - ~
- H'~ 0
w
i ~
SFZ ~ 4 T T T~
~l
0
C Kp�
KO OM~
" Figure 4. Block diagram of the nonlinear equalizer
YT JT 6T
-T 0 T 4T t �T 0 T t �T 0+T t -T 0~T t
A 8 C O ~
Figure 5. Diagram of the wave forms sampled at the various points of the equalizer
The SF1 filter is a transverse filter with eight coefficients; it makes it possible
to force to zero the interfering signals that are different from the precursor,
which will be cancelled by the following cells with decision feedforward, and by
the first tail.
- The addition of an ever greater number of cells of the decision-feedforward type in
cascade ensures a gradually decreasing error probability at the output of the upper
branch, since, in the event of a-nistaken decision in a cell, the error can be rem-
- edied in the succeeding cells. At the output of the upper path (point B), the sig-
nal is affected by the residue of the first tail not completely cancelled by SF1.
The SF2 filter too is a tY�ansverse filter with eight coefficients and has a role
analogous to that of SF1; the residual tail is cancelled by a cell of the decision-
feedback type, and the signal at point C will therefore be affected by a distortion
due to the residue of the precursor.
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The signals coming from the two routes flow together into an adder and from there
into a double cell with feedforward and feedback reactions that provides sor elim-
ination of the precursor signal and the residues tail.
The diagrams of the wave farms sampled at poit~ts A, B, C and D are given in Fig-
ure 5.
The type of algorithm used and the type of signal worked on lend themselves very
well to an arrangement using a microprocessor in which, by exploiting the flexibil-
ity of the software prepared, it has been possible to develop the various internal
functions of the equalizer and investigate various co~struction schemes and their
relative performance characteristics.
In particular, it has been possible to make a comp3rison between the performance
characteristics of the nonlinear equalizer of Figure 4(with N= 3) and those of
the eight-coefficient transverse equalizer of "zero-forcing" type--that is, of com-
plexity equal to that of each of the twa shaping filters SF1 and SF2.
From the curves of Figure 6, which indicate how the error rate at the decision
point varies with the variance of the signal-to-noise (S/N) ratio at the input of
the equalizing structure, it can be noted that the performance characteristics are
better in the case of the nonlinear equalizer.
1: FILTRO NON LINEAR[
~~2 2: fIITROTRALVERSAIE
(3)
Q , a
s ~~3
Q
W
~
~ ~O~
~
f
106
SM
14 16 18 17 1B 19 20 (dB)
6897
Figure 6. Curves comparing the performance characteristics of the nonlinear equal-
izer and the transverse equalizer
Key:
1. Nonlinear filter 2. Transverse filter 3. Error rate
5. Microprocessor Inserted into a System for Acquisition and Processing of the
Measurement Data of the Experimental COS 3/FOSTER Installation
The application consists in the construction of a microprocessor device whose task
is to:
1) take the measurement data relative to the significant magnitudes of one or more
transmission systems (up to a maximum of eight);
2) do several processing operations on them;
,
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3) ti~ansrnit to a(remote) centralized organ the i:~formati~n put into memory;
4) present this intormation in viaual form for local monitoring.
_ ~----~-----,r-----------,~-----r--- ~
I T. R~ T. R. T. R� T~ T�
~ I I ~ I SISTEMA U1 THA$1.115SK1NE I I I I I
~sros~rwo I~ ri~siTrvo ~ ~ I I isvos~nv I I ~srosrtrv ~
_ ( 1 4 YICRO~ I I A MICRO~ I I SU FIBHO OnIG ( 2) I ~ A MICRO~ I I A MICRO~ I7 `
vROCESS. ~I PROC ~ ~I PROCESS. II PROCESS Ii ~
~ BUS RSm ~I I~ ~i II I
li
~ IMODEM AqOEM I~ MOOE MOOEM ~
- --~I --~L--
CENTN~ CEMRALE ~ I CEN:~~LE CENTN.
S. MARIA AVENTINO idpDEM MOOEM I EVR r 6~ flpAA~ r 7 1
IN VIA ~ ? SU~ ? /
~IHEA DEDICATA I
~ 3~ ~ 5~ I MOOEM "EM I
~ ISPOSITIV ~
I A MI~qO I
~ PRCCESS. ~
i~l II
INTEAFA~CE ~
~ FS zi7 ~
i ORGANODI ~
ELA80RAZIONE ~
I ~ ~ CEN7RAl122AT0 I
ENTRALECOLOMBO ~ ~
1IIk---------~
Figure 7. Block diagram of the measurement-data acquisition and processing system
of the COS 3/FOSTER experimental installation
Key:
1. Microprocessar device 5. EUR center
2. Optical-fiber transmission system 7. Rome-South center
3. Santa Maria in Via center 8. 5 RS-232 interfaces
_ 4. Avention center 9. Centralized processing organ
5. Dedicated line 10. Colombo center
, The device in question is inserted into a measurement-data acquisition and proces~-
ing system, the block diagram of which is given in Figure 7 and that has the pur-
pose of monitoring the performance characteristics of the COS 3/FOSTER experimental
digital-transmission systems installed on optical cable between the Sax~ata Maria in
Via and Rome-South exchanges, in Rome (Bibliography 3, 4, S).
Because of the experimental aspect of the installation, it is necessary to relate
the deterioration of transmission quality to the course of the per�ormance charac-
teristics of thE principal system components to be monitored.
It is therefore necessary for the microprocessor to take, at regular time inter-
vals, a certain number of digital and analog magnitudes that characterize the sys-
tems' transmission and reception terminals and store them in memory.
The magnitudes to be memorized for each transmission system are the following:
1) number of erroneous bits within a suitable time window;
. 2) alarms of ~he receiving and transmitting terminal and power-supply alarms;
3) pilot current of the LED (Light-Emitting Diode) in the transmission terininal;
4) temperature of the LED container in the transmission terminal;
5) current of the AGC (Automatic Gain Control) reaction ring in the reception ter-
minal;
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6) polarization voltage of the APD (Avalanf�he Photodiode) in the reception ter-
minal.
The microprocessor assigns a sequential number to each data block, consisting of
the abovementioned magnitudes relative to all the systems monitored, and in addi-
" tion, calculates for each system the EFT*--a magnitude very significant for estab-
lishing, together with the error rate,** the quality of the transmission.
All these parameters characterize, for the time-interval considered, the state of
the transmission systems being mon~tored, and t~ey constitute the data block that
will be sent to the centralized processing organ on its request.
The centralized processing organ synchronizes the ir~dividual microprocessors and
periodically issues to them the order to send the last block memorized. In this
way, it is capable of deducing the cause of any deterioration of transmission qual-
ity.
The error rate is checked as follows: when the centralized processing organ per-
ceives that it has gone beyond preestablished thresholds, it memorizes on magnetic
_ support the "history" of the transmission system whose quality has deteriorated.
These measurement data are printed out and can be processed off-line to determine
any eventual functions of statistical distribution of the errors.
The measurement-data acquisition and processing system described is thus a typical
example of a distributed-intelligence system; indeed, some of the functions to be
performed have been assigned to the peripheral microprocessors. In this way, the
- following advantages over a completely centralized structure were obtained:
a) greater processing speed;
- b) greater flexibili~.y of the structure;
c) increase in overall reliability of the system.
The microprocessor also performs the function of local monitoring of transmission
systems: all the magnitudes stored in memory can in fact be visualized on a screen
and the local operator is therefore enabled to perceive any malfunctions of the
systems being monitored or deterioration of transmission quality.
6. Outlooks and Conclusions
The continual technological evolution in the field of integrated circuits opens up
n.ew prospects for the users of these devices. There are essentially two lines of
approach identifiable in the construction of microprocessors apparatuses for trans-
mission systems:
a) In the cases in which these apparatuses have to process the signal in real time,
the approach is to individuate very specific functions of the transmzssion system
* EFT = minutes without error
minutes of observation
number of erreneous bits
error rate - number of bits received
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(for example: filtering, coding) and develop them with microprocessors specialized
for such applications, which make possible a speed of treatment of the input sym-
bols of some 10's of kHz.
If it is necessary to increase the input-symbol processing speed beyond that limit,
the approach expected is to design ad-hoc (custom) integrated circuits. Such a
choice entails an integration of the tasks of the custom-circuit designer and of
the person who defines th~ architecture af the system to be integrated.
b) In those cases in which the m~croproc:essor apparatuses are intended to have sys-
tem management or control functions, th~ approach is to use "single chips" in the
minimal applications and 16-bit microprocessors when the data-processing problem is
- complex. In both cases, the approach is to distribute the processing capacity in
peripheral equipment, when the action of the controt or management system has to
extend over a broad territory.
BIBLIOGRAPHY
1. Fabbri, B., Sacchi, L., Tosco, F. and Veglio, G., "Hybrid-Type 140-Mbit/s Digi-
tal Transmission System on Coaxial Cable," CSELT Technical Reports, Vol III,
No 1, April 1975, pp 3-18. ELETTRONICA E TELECOMUNICAZIONI, XXV, 1976, p 135.
2. Tamburelli, G., "Digital Receiver with Distributed and Integrated Decision
Feedback and Feedforward (to Overcome the Nyquist Barrier)," CSELT Technical
Reports, Vol IV, No 4, December 1976, pp 199-209.
3. Bonaventura, G., Costa, B., Cottatellucci, 0., Daino, B., Esposto, F. and Lom-
bardo, F., "COS 3/FOSTER Field Trial with an Optical Cable in Rome," paper pre-
sented to the Sixth European Conference on Optical Communication, York, Septem-
ber 1980.
4. Bonaventura, G., Catania, B., Gagliardi, D., Paladin, G. and Tosco, F.,
"COS 3/FOSTER: First Optical Fibre System for Operational Service in Italy,"
paper presented to the International Conference on Communications, Denver,
June 1981.
S. Esposto, F., Lombardi, F. and Paladin, G., "Results and Evaluations of the
COS 3/FOSTER Optical-Fiber Experimenta~ilnstallation," ELETTRONICA E TELECOMUN-
ICAZIONI, XXX, 1981, pp 79-85.
COPYRIGHT: 19i4 by ERI-EDIZIONI RAI RADIOTELEVISIONE ITALIANA
11.267
CSO: 5500/2098
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IT'ALY
DIGITAL ftADIO-RELAY SYSTEMS AT 19 GHz IN URBAN AREAS
_ Turin ELETTRUNICA E 1'E:LECOMIiNICAZIONI in Italian Nov-Dec 81 pp 247-252
_ [Article by P. Amadesi, R. Failli, G. Masone and L. rforeno*]
[Text] Summary--Digital radio-relay systems operating at 19 GHz for metropolitan
areas. In the near future, digital radio-relay links should connect telephdne ex-
changes in metropolitan areas. The main problems related to the design and devel-
opment of such systems are considered and some proposed solutions are discussed.
First, the general system characteristics are dealt with and the choice of the 17.7
to 19.7 GHz band is justified, taking into account the expected hop length, link
capacity, availability required, etc. The criteria for an efficient spectrum util-
ization are next examined. The four-phase PSK seems to be the most feasible be-
cause it represents the best compromise between bandwidth occupancy and interter-
ence sensitivity in a multiple interference environment. Moreover, an effective
procedure for automatic carrier frequency assignment has been adopted in ordFr to
minimize the number of radio channels required. Finally the compatibility with
satellite systems sharing the same frequency band is discussed and some preliminary
_ results on coordination procedures are presented.
1. Introducticn
The linl: network that connects urban telephone exchanges has until now used almost
excliisi.vely paired cables installed in condui.t.
In recent years, though, digital systems on cable have been introduced especially
for the longer links, wtiere they offer the greatest advantages from the technical
and economic point of view. The introduction of digital-type exchanges will broad-
en the field of application of such systems, while in the future, optical-fiber
_ cables will also be used in the same type of network.
The digital radio-relay systems are a valid alternative or a complementary means in
this field ot application, and they offer the following advantages:
* k:ngineer Paolo Amadesi, En~ineer Luigi Moreno of the CSELT (Telecommunications
Research and Study Center), Turin; Engineer Renzo Failli, Engineer Giorgio Masone
~f the SIP [Italian Telephone Company], General Administration, Rome.
_ Typescript received 29 July 1981.
This paper was presented to the In:ernatianal Conference on Communications, 1981.
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---~~ussibili.ty of i,nproving network availability by adopting diversified means of
transmission (ca~le and radio) that are subject to breakdowns that have practic-
- a11y no correlation with one another;
--F~ossibility of making inexpensive relay links in areas of difficult topography;
--possibility of making urgent connections in a short time.
'rurthermore, cost comparisons have shown that medium- and high-:apacity radio sys-
tems are suitable, as against coaxial-cable systems, for connections longer than
about 2 km ~Bibliography 1).
_ The introduction o~ radio-rel~y systems into this new field requires a detailed ex-
amination of various questio~~s.
- The purpose of the present paper is to provide a concise description o� the main
J problems to be tackled in the design and develapment of the new radio systema to be
used in urban relay networks, illustratir.g also the principal solutions adopted.
_ Section 2, in particular, presents the characteristics of the system anticipated
for the 17.7-19.7 GHz band. In section 3 are discussed the criteria for efficient
' utilization of the spectrum within the urban environment, and an automatic proce-
dure for a;signment of frequencies in a close-mesh radio network is cited. Section
4 examines the problem of the sharing of the 17.7-19.7 GHz band as between radio
relays on lard and fixed services via satellite.
L. Characteristics of the System
]n order to define the principal characteristics of the radio equipment to be used
i.n the urban environment, and in particular the frequency band, the modulation
method and the capacity per carrier, it is necessary to determine sufficiently
closely the networic conFiguration, the distribution of the hop lengths ~nd the num-
f~er oL circuits to be transmitted on each run.
As tl~e first step, the visibility conditions between the urban telephone exchanges
in the major Italian cities, both with a direct connection and through intermediale
~ centers, including the existing radio stations, were checked. The height of tt~e
trestli~work possibly necessary for achieving the visibility conditions was assumed
to be. limited to reasonable values, in order to respect the cities' environmental
and esthetic requiremen~~
Vext, the compl?te co~ifigurations of the networks were determined, taking into ac-
~ount f~oth the visibilit}~ conditions and the preliminary assumptions relative to
rlie breakdown, as between cable systems and radio systems, of the digital relay
syste~ms anticipated in the next 20 years. In particular, it was assumed that the
_ riini.miim r.un length would be limited to 1.5 km and that connecl-ions would not be
made with more than 4 runs.
~~s an example, Figure 1 shows the network configuration planned in the metropolitan
area of Rome; for each run, the capacity, expressed in number of 35.368-Mbit/s sys-
tt_~ms (the third level of the European digital hierarchy), is indicated,
_ 'I't~~~ final conLiguration of each urban network will necess,3rily depend on more pre-
~~i.se technical and economic considerations, including overall network availability,
22
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tf~at will be possible only after an adequate period of experience with sy::tems in
use. Never[heless, the preliminary results already obtained are sufficient for op-
timizing the principal charac;:eristics of the system.
~
1 2 2
~ 8 2
_ 1
1 3 3 3
- 6 4 3
- 2
1 4 ~ 8 1 ~
1 ~ ~ 2
t 2 ~ 1
4 5 1 3 i
4
2 6 1 1
1 5 7 6 1
3 Z 4 5 2
p 1
7 1
2 3
2 ~ 5 0
~ 1
1 2
_ ~ 2
3
~
` 1 2
2 2
9905
Fi~;ure 1. Digital radio-relay network at 19 GHz planned in the area of the city of
- Rome for the year 2000. The number marked on each run is the number oI
34-Mbit/s groups required for the run.
w 30
~~o~~ .
J ~
J
~
W
J
Q ~ro f
- 1 ~ ~ .
r ~Q ~6 f i~f 3 l:~
~
Z ~ ~ Y 10
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a O ,e.y,~k' < S ~r� "r'S a ~~::a.: .
~ ~ t~ ~
O . 2 4.. 6 e ~
( 2) ~UNGHEZZA OELLA TRATTA ( km)
P'igure 2. Distribution of the run lengths
Ke}~:
1. Percentage of the runs 2. I.ength of run (km)
I~irst of all, two radio-channel capacity values were chosen: 34 Mbit/s and
140 ~lbit/s. It stiould be kept in mind that in the network planned for the ~irban
- area of Rome, which will certainly be one of the biggest ones, the number of
34-Mbit/s systems required for each run is between 1 and 11, and the percentage of
runs that require at least eight 34-hlbit/s systems, which would justify a digit
speed of 280 Mbit/s, is very Zow.
23.
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G'i~ura 'L presents a histogram of the distribution uf the run lengths; it can be
noted that the maximum length is approximately 10.5 km and that most of the runs
are shorter than 6 km.
In order to keep the unavailability times due to rain below reasonable limits (10
to 20 prime minutes per year) for each of the runs, using normal fading margins on
the order of 40 dB, it emerges that ltaly's climatic conditions do not permit the
use of bands higher than about 20 GHz (Bibliography 2). On the other hand, it is
not suitable to use frequencies lower than 13 GHz, which would make it possible to
have longer run lengths, since they are already assigned and used for medium- and
long-distance connections.
~ A further requirement of the systems under consideration is that a rather high to-
tal radio band be available in order to meet the capacity requirements of the nodes
in whicil many runs converge. The 17.7-19.7 GHz band therefore appears the most
suitable for this type of application.
The ICCR [International Consultative Committee on Radiotelegriphy] recently ap-.
~roved the provisional text of a new recommendation relative to the plans for chan-
nelization of this frequency band for radio-relay systems with capacity of about
280 Mbit/s, 140 Mbit/s and 34 Mbir/s (Bibliography 3). The plans recommended for
the configuration with cochannel reuse of frequencies for the capacities of
14U rlbit/s and 34 :Ibit/s are shown in 'r'igure 3.
As regards the modulation techniques, the considerations set out in section 3 in
relation to dense radio networks indicate that four-phase PSK [expansion unknown]
is the most suitable technique for the application examined in this paper.
'I'he radio-relay systems that operate at lower frequencies generally adopt some form
of prote~tion (for example, difference of frequency or of spacing) in order to re-
duce the effects oF the phenomena due to propagation and to improve the availabil-
ity of tt,.e system as regards equipment breakdowns aLso. In the 17.7-I9.7 GHz band,
attenuation from rain is the dominant effect of propagation because of the limited
lengths of the runs, and therefore it is not possible to improve the system's
availability due to the propagation factors except by careful choice of the run
lengths and of the fading margins.
Fur thes~. reasons, use of protection systems of the 1+ 1 type or the multiple-beam
ty~~e could only improve availability as regards equipment breakdowns.
In a~:~J~lications in urban areas where there is generally a diversified transmission
medi~.im, such as a cable network, it appears more appropriate to use unprotected
svstems, with consequent economic and spectrum-use advantages. The equipment must,
of co~�rse, be protected with sufficient reliability to obtain availability of the
ronnections similar to that of the cable systems.
'fable 1 presents the typical values of the parameters relative ta the equipment and
- the radio runs. In runs longer than 6 km, antennas of greater diameter (1.5 m)
_ wi11 be used in order to augment the fading margin availahle.
_ 24. .
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- .25.
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lation procedures have been developed for fast and accurate evaluation of the de-
teriorations of PS~ signals in a multiple-interference environment (Biblio~;rapliy 7).
In the preliminary phase of system definition, it was sought to evaluate the influ-
ence of various design parameters on utilization of the spectz~im, by means of a
generalized model based on the criteria and fundamental definitions of spectral ef-
ficiency (Bibliography 8).
The basic concept is that each radio connection, operated on a given frequency,
prevents other connections from operating on that same frequency within a given re-
gion, which depends on the transmitting power, the antenna pattert!s, the propaga-
- tion characteristics, the demodulator's sensitivity to interferences, etc.
Taking into accoucit the fact that the radio spectrum can be defined in the three
dimensions of frequencies, physical space and time (Bibliography 8), one can evalu-
ate the "quantity of spectrum (band X area X time) used" by any connection of the
network. Finally, the efficiency of utilization of the spectrum can be expressed
~ as tt~e ratio between the quantity of information transmitted on a given connection
_ and the spectrum used by that connection.
ln a previous article (Bibliography 9), a detailed description was given of the
model adopted. Below, several results are presented relative to the cfioice of mod-
t~lation method in digital radia-relay networks at 19 GHz.
3.1. Examination of Modulation Methods
The analysis model for utilization of the spectrum was applied vis-a-vis coherent
PSK modulation systems with M phases. It is know that with the increase of M, the
band occupied reduces, at equal transmission speed in terms of bit/s; neverttieless,
with increase of M a more limited number of frequeucy reuses is acceptable, since
_ sensitivity to interferences rises.
e
i E
N t
0 6 ae /7=a
~ a 2a
(1)~ ! ~r:2 e~
N 2 ~
z ~
~ t6 p
- ~ o
. W o i z a a
( 2 ~ BIT/FORMA D'ONDA
F'igiire 4. Efficiency of utilization of spectrum in a radio network with PSK modu-
. lation with M phases. On the abscissa is the number of bits associated
- with eac}~ wave form.
Ke;:
l. Spectral efCiciency (bit/s � Hz) 2. $it/wave-form
Fig~lre 4 presents, for various values of M, spectral efficiency E, which is equiva-
lent to the traffic capacity per band unit (bit/s�Hz) in a region of area equal to
26.~
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the mean quadratic value of the run length. Reference is also made to a parameter
Y, which is indicative of the network density and is defined as follows:
_ ~ Mean quadratic value of run length
- Y N Total area covered by radio network
in which N is the number of radio cente:-s in the network.
Analysis of several actual cases has shown that Y= 2 and Y= 4 can be taken as re-
presentative values for urban networks of inedium and high density, respectively.
The results of Figure 4 are based on the following hypotheses:
Transmission power equal on all runs
Performance-characteristics threshold error probability = 10-3 with 40 dB
fading margin
Antenna pattern (diameter of paraboloid ICCR mask ~Iteport 614) with gain of
= 1 m) 42.5 dB
Performance-characteristics deterioration
from total of interference 3 dB
( X= 1.6 PSK 2 and 4 phases
Standardized channelization pitch ( X= 2.0 PSK 8 phases
( X= 2.3 PSK 16 phases
Frequency reuse on cross-polarization ~ frequential %so YSK 2 and 4 phases
( interstitial' PSK 8 and 16 phases
Parameter of density Y= 2 and Y= 4
Various other calculations were carried out, with different sets of parameters, in
order to check, in the various cases, the best compromises for optimal use of the
spectrum. In any case, Figure 4 can be considered quite significant. It shows
that 4-phase PSK modulatiAn can be advised in this kind of application inasmuch as
it achieves the best compromise between band occupation and sensitivity to inter-
ferences, in a broad range of real situations.
On the other hand, 2-phase PSK is the most efficient in very crowded networks
and/or with antenna patterns that are not very directional. Eight-phase PSK, or
- other multilevel modulations of high order, may be preferable when limited band oc-
cupation becomes the dominant factor of spectral efficiency--that is, in low-dens-
ity networks, such as the long-range ones.
3.2. Assignment of Transmission Frequencies
- In the designing of a specific radio network, spectral efficiency can be optimized
by careful coordination of the interferences. Since the number of connections may
be very high, it is advisable for the assignment of the transmission frequencies
to each run to be done by means of an automatic procedure.
The procedure described in Bibliography 10 meets this requirement, assigning the
frPquencies with the restriction of not exceeding a maximum level of interferinK
* in the case of frequency reuse with interstitial method, it is intended that the
carrier frequencies on horizontal and vertical polarization be staggered by one-
half a channelization pitch.
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~ower in each recE�iver and with ttie objective of minimizing the total number ~i
carrier frequencies necessary in the entire network. The main advantage of thi.s
procedure is represented by the possibility of easily imposi.ng various restrictions
and of handling connections both of 34 Mbit/s and of 140 Mbit/s.
In the system-defin~tion phase also, this procedure can be useful for analyzing the
influence that various parameters (transmission power, antenna patterns, fading
margins) have on the number of carrier frequencies required.
Several preliminary tests of this procedure were carried out, using a network with
topological characteristics similar to those expected in the major Italian cities
(see section 2). These tests have confirmed the validity of the frequency-assign-
= ment procedure and the possibility of intensive frequency resue.
_ It was also verified ttiat the number of carrier frequencies required depends con-
siderat~ly on the choice of the transmission powers and the fading mzrgins. Consid-
er, for example, the two cases presented in Table 2. In the first case, it is as-
sumed that the power transmitted and the fading margin are fixed independently of
the run length, while in the second, the power transmitted in the shorter connec-
tions (under 4 km) is considered reduced by 6 dB, so as to reduce overal interfer-
- ence. In the shorter connections, it is also assumed thatthere is a reduced fading
margin, but nevertheless one that is suffi.cient to ensure the availability required
(t3ibliography 2).
Table 2--Parameters Adopted for Automatic Assignment of Carrier Frequencies
Hypothesis A Hypothesis B
nigit
Frequency Transmitted Fading Run Transmitted Fading
_ Power Margin Length Power Margin
34 Ptbit/s 16 dBm 40 dB < 4 km 10 dBm 35 dB
_ > 4 km 16 dBm 40 dB
14Q ,~1bit/s 22 dB 40 dB < 4 km ~6 dBm 35 dB
> 4 km 22 dBm 40 dB
In the second case, it emerges that the necessary number of carrier Erequencies is
25-percent less than in the first case. At present, other possible choices of
transmitted power are being considered, keeping in mind the restrictions imposed by
- tiie simplicity required for the operations of tuning and maintaining the equipment.
The abovementioned calculations were done with adoption of the antenna-directional-
ity ~nask proposed in ICCR Report 614 and assuming a 1-meter diameter of the parabo-
lid antenna. This mask was used merely as the first point of reference, while fur-
ther calculations are planned that will use the radiation patterns of antennas de-
_ siKned for these applications.
4. Sharing of Frequencies with Fixed Services via Satellite
'['he possible presence of fixed services via satellite t}iat share the entire 17.7-
19.7 Gtiz band, or part of it, with the fixed services on land, with primary-level
allocation, is a fundamental problem to be examined for correct planning of a
radio-relay network in an urban area.
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" In the Iirst place, the antennas' t:ansmissions adhere to appropriate restrictions
in ICCR Recommendations 358-2 and 406-4, so as to limit direct interference Cr.om
space transmitters in the ground receivers and from ground transmitters in the
space receivers.
Furthermore, the possible coexistence of radio-relay systems and earth stations re-
ceiving or trans~;itting from a satellite in a common geographical area requires
that the mutual interference~ be analyzed carefully, for correct coordination of
the services.
We illustrate several preliminary results relative to this question, obtained from
from the case of two satellite systems that are being planned in Italy.
a) ihe first problem examined concerns the earthward connection oF a national sat-
- ~llite for telephonic communication with spot-beam coverages (Bibliography 11,
- 13) of the nation's major cities. The connection planned for the satellice-to-
earth run uses the 17.7-20.2 GHz band and transports high-capacity channels. 7'he
earth stations receiving from the satellite must necessarily be situated within the
metropolitan areas or in the immediate vicinity in order to be connected easily
_ with the principal telephone-traffic switching centers. Consequently, all the ra-
dio channels via satellite that are not comprised within the 19.7-20.2 GHz part of
the band (which are assigned exclusively to service via satellite) undergo the in-
terferences caused by the urban radio relays. ~
For an initial quantitative evaluation of this interference, we established con-
servative hypotheses, assigning to the various par;imeters the numerical values giv-
en in Bihliography 11, considering the antenna radiation pattern of ICCR Report
- 390-3 for the earth-station antennas and examining the radio channels interfered
wity in the most unfavorable way.
The calculation results relative to the interferenc~ of a single transmitter of the
radio-relay network in an earth station receiving from satellite are presented in
Fifiure 5 in the form of "interference contours" on a topographical n?ap. Eact~ con-
to�r is characterized by a constant value of the gain GR of the radio-rel.ay antenna
in the direction of the earth station (ES) and represents the total of the minimum
distances around the ES i.n which a network transmitter with antenna gain GR can be
sited in such a way that tt~e C/I ratio at the earth-receiver input is equalto 35 dB.
C/I is the ratio between the powers of the useful signal coming from the satellite
in the sev~re fading conditions that cause rhe threshold condition of error rate of
10-3 and tne power of the nonfaded network interfering signal.
The 35-d13 value of C/I is rather protective in a case in which there is only one
interferin~; signal, and proves not very severe even if the radio network is dense;
for example, 10 interfering signals with /equal frequency/ and with C/I = 35 dB
each cause a total C/I ratio of 25 dB, which is therefore responsible for a consid-
erable deterioration of the receiver's performance characteristics.
Figure 5 shows that the distance required for limiting the interference from a
single transmitter is a notable function of antenna gain GR and unfortunately can
have values of several 10's of kilometers. Consequently, when the number of inter-
fering transmitters of the network is high, tl-ie possible inclusion of stations re-
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9 ceiving from the satellite to earth in an urban area of inedium extent appears
- rather critical.
zo
,Gp =20dB ~km~
~ 1 ~ SA7
t3 ~ }
~
S
\
5
1p (km)
_ 0
10
C~1 . 35dB
- ~ 20 ~
Fi~ure 5. Sharing of frequency with the downward run of a national satellite for
digital fixed services. Contours of interference in the case of a re-
ceiving earth station (ES) and an earth radio-relay transmitter with an-
tenna gain GR in the ES direction. C/I = 35 dB. The satellite's angle
of elevation is 40�, a val~ie typical for Italy.
Key:
1. Satellite
~
Gq ~ 1
- , 20d8
SAT
83 f
55
3
1
~ ES
20 1 p p
b
C/I:25d8 i~f
0
0 ~
Fi~;ur~ 6. St~aring of freyuency with the upward connection of. a television-broad-
casting satellite. Contours of interference in the case of a transmit-
ting earth station (ES) and an earth radio-relay receiver with antenna
gain C~ in tt~e rS direction. C/I = 25 dIi. The television satellite's
angle of elevation is 30�, a value typical for Italy.
Key:
l. Satellite
Assignment of the largest possible number of separate carrier frequencies to the
two services therefore appears to be a requirement for reducing the complexity of
coordination of the services.
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b) The second problem concerns the earth-satellite connection (feeder link) for
direct broadcasting of television signals that couZd operate in ~he 17.3-18.1 C:I1z
band and therefore share the spectrum portion between 17.7 and 18.1 GHz with the
other fixed services.
- In the Italian case, the five channels assigned to Italy anci to the Vatican will
probably fall within the sharing band (Bibliography 12), so that the power emitted
from the transmitting earth station will cause interference in every earth receiver
operating on those frequencies.
The possibility of siting the earth transmitting station within the metropolitan
area has been examined with che aid of the interference contours of Figure 6, ob-
tained in a manner analogous to those for Figure 5.
It was assumed that the EIRP (Effective Isotropic Radiated Power) of the eartti sta-
tion in the direction of the satellite is equal to 65 dBW and that the transmittinb
antenna has a diameter of 5 m radiation pattern in conformity with the ICCN charac-
teristic (Report 39U-3); the curves relate to the most severe interferential situa-
tion czused by the TV/FM channel most unfav~rably positioned in relation to a
34-Mbit/s digital channel.
In Figure 6 there is only one source of interference--that is, the earth transmit-
ting station--and the C/I ratio is therefore fixed at the critical value of 25 dEi.
The situation certainly appears more severe than in the preceding case of Figure 5,
- and topological coordination of the two services proves quite complex i_n those
cases in which the metropolitan network is rather dense.
Coordination of the ground services and those via satellite therefore constitutes
- an open problem that calls for further investigation in depth. More detailed and
closer analysis of the interferences examined in this section was subsequently un-
dertaken and is reported in Bibliography 14.
Acknowledgements
Ttie authors thank ~ir L. Bassis and Pfr M. Ercolin for their efFective cooperation in
carrying-out of this work.
BIBLIOGRAPHY
1. "Uigital Radio Relays for Urban Areas in the 19-GHz band." SIP Internal Re-
port, May ]980.
" 2. Colavito, C., "New Systems in Radio Networks," Conference on Radio Relays,
L'Aquila, May 1979.
3. ICCR, Study Group 9, "Radio Frequer..c~ Channel Arrangements for Digital Radio-
Relay Systems in the 17.7-19.7 GHz Frequency Band," Proposal for New Recommend-
ation, Doc 9/209, Interim Meeting, Geneva, October 1980.
31
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4. Colavito, C. and Sant'Agostino, M., "Binary and Quaternary PSK Radio Systems in
a Multiple Interferer.ce Environment," IEEE TRANS. CONL'~ILiNICATIONS, Vol COr1-21,
~ Septembei� 1973, pp 1056-1067.
5. Ruthroff, C.L., Tillotson, L.C. and Prabhu, V.K., "Efficient Use of the Radio
Spectrum and Bandwidth Expansion," PROC. IEEE, Vol 61, April 1973, pp 445-452.
6. Masone, G. and Moreno, L., "Optimal Use of Digital Radio Relays in Big Urban
Areas," 22nd International Conference on Communications, Genoa, October 1974.
7. Amadesi, P., "A Fast Evaluation of the Error RatE in CPSK Systems with Inter-
symbol and Multiple Cochannel Interferences by Means of Local Approximations
of the Error Function," International Symposium on Information Theory, Santa
Monica, Calif, February 1981, and CSELT TECHNICAL REPORTS, Vol 8, June 1981,
pp 199-206.
8. lierry, L.A., "Spectrum Metrics and SpP~trum Efficiency: Praposed Definitons,"
IEEE TRANS. ELECTROMAGNETIC COMPATIBILITY, Vol EMC-19, August 1977, pp254-260.
9. Moreno, L., "Spectrum Utilization in a Digital Radio-Relay Network," to be
published in IEEE TRANS. ELECTROMAGNETIC COMPATIBILITY.
10. Barberis, G. and Zingarelli, V., "Application of Network Optimization Algo-
rithms to the Radio Frequenc~ Assignment Problems," International Conference
on Communications, Denv~~r, June 1981.
11. Tirro, S. and Drioli, B., "Possibilities Offered by Artificial Satellites for
National Communications in a Large European Country," TELECOM '79, Geneva.
12, Tomati, L., "Planning of a Television-Broadcasting System from Satelli.te,"
ELETTRONICA E TELECOMUNICAZIONI, September 1977, pp 182-194.
13. 13erretta, G. and Tirro, S., "New Telecommunications Systems at 20/30 GHz,"
International Conference on Communications, Seattle, June 1980.
14. Amadesi, P. and Failli, R., "Criteria for Sharing of Frequencies by Radio Re-
lays and Earth Stations for Telecommunications via Satell.ite in a Large Urban
~rea," 29th International Conference on Communications, Genoa, October 1981.
Cc)E'YItIGHT: 1974 by ERI-EDIZIONI RAI RADIOTELEVISIONE ITALIANA
11267
cs0: 55UU/2099 END
32 -
FOR OFFICIAL USE ONLY
APPROVED FOR RELEASE: 2007/02/09: CIA-RDP82-00850R000500040014-7