Ten satellite systems for international communication are briefly described. Modulation and coding schemes on some of these systems are highlighted

Wu, William W.

English

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N92-o 2021
INTERNATIONAL COMMUNICATIONS SATELLITE SYSTEMS
William W. Wu
INTELSAT
Washington, D.C. 20546
ABSTRACT
Ten satellite systems for international communication are briefly
described. Modulation and coding schemes on some of these systems
are highlighted.
i
An invited paper to be presented at the Advanced Modulation and
Coding Technology Conference, sponsored by NASA Lewis Research
Center, June 21-22, 1989.
PRECEDING PAGE BLANK NOT FILMED
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https://ntrs.nasa.gov/search.jsp?R=19920012778 2020-03-17T13:12:55+00:00Z
1.0 Introduction
After a quarter century of innovation, development,
cooperation and services, satellite communications have had
significant world wide impact and brings people closer than ever
before. International satellite communications has increased by a
factor of more than one hundred. Nearly two hundred countries and
territories use satellite for television, radio, telephone and data
services. As technology advances, service requirements and traffic
patterns change, the interests of satellite communication
communities also change. Among the changes is the creation of
multiple international communication satellite systems.
In this paper an attempt is made to highlight these
systems. Among the international systems considered are:
• INTELSAT
• INMJkRSAT
• MOLNIYA - STATSIONAR
• EUTELSAT
• ORION
• ARABSAT
• ASIASAT
• ASTRA
• PANAMSAT
• HISPASAT
Although some of these systems are regional, in this paper a system
is referred to as international if its operation is beyond the
boundary of a single nationality. Otherwise they are referred to
as domestic or national systems. A glance at some of the
synchronous orbit satellites is shown in Figure 1 [i].
2.0 INTELSAT
INTELSAT is the international telecommunication satellite
cooperative established by the world wide treaty. With 15
satellites the INTELSAT system covers all three oceanic regions
over the globe. Its membership contains 115 countries and link
together more than 165 countries and territories. At present,
there are more than one thousand ground stations utilizing
INTELSAT's space segments. Technically, INTELSAT was the first to
use channe!ized repeater in INTELSAT IV, the first to exploit
spatial re-use of frequencies in IS-IVA, the first to combine
spatial and polarization frequency re-use in INTELSAT V, the first
to implement high speed TDMA and SS/TDMA in INTELSAT VI, the first
to use a linearizer in INTELSAT VII. Most of all, all INTELSAT
digital systems employed error correcting codecs. A number of
these codecs have been introduced into other international
communication satellite systems.
316
To meet traffic demand the following INTELSAT systems have
been implemented:
• FDMA/FM
• SPADE, SCPC
• IBS
• INTELNET
• TDMA
• IDR
• VISTA
Some of these systems are well known, others can be found in
references [2, 3, 4, 5]. The INTELSAT gateway stations are shown
in Table i. The six INTELSAT satellite series are summarized in
Table 2. The main features of INTELSAT VII is shown in Table 3.
No new modulation and coding schemes have been proposed through the
TDMA system to be operated on INTELSAT VII.
All INTELSAT digital systems employ phase modulation. For
SPADE and SCPC systems rate 3/4 self-orthogonal convolutional code
with threshold decoding is used for 48 kbps data, the rate 7/8
convolutional code are used for 56 kbps data. The (128, 112) BCH
code of 120 Mbps is implemented in the INTELSAT TDMA system. The
(24, 12) Golay code is used for digital speech interpolation
assignment messages. For INTELSAT's IBS both rate 1/2 and rate 3/4
punctured convolutional codes with soft decision Viterbi decoding
are part of the system. Operated from 64 kbps to 45 Mbps the
INTELSAT Intermediate Data Rate (IDR) system has a constraint
length 7 convolutional punctured code of code rate 3/4 with Viterbi
decoding [6].
3.0 INMARSAT
The system was established in 1979 and operational in 1982
for the purpose of international maritime communication. Today the
INMARSAT system provides services to more than 70 countries. Among
one of the most forward looking international organization INMARSAT
not only provides services to ships in all three oceanic regions,
but also is in the process of providing land mobile as well as
aeronautical applications. In a recent paper on mobile satellite
services Mr. Olof Lundberg, the Director General of INMARSAT set
the tone for international co-ordination, co-operation and
competition [7]. Coordination for networks operate within the
allocated and limited L-band is essential, because such networks
have been planned by Australia, Canada, France Japan, Mexico,
Papua-New Guinea, U.S., U.S.S.R. as well as INMARSAT. Cooperation
among the network providers, users and manufacturers can enhance
the marketability and unify the compatibility. Competition can
keep cost low and the quality of service high.
The INMARSAT system consists of the space segment, coast
stations, and stations on ships. For _he space segment INMARSAT
currently leases capacity on various satellites, such as MARISAT of
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COMSAT General, MARECS of ESA (European Space Agency), as well as
INTELSAT satellites. At present there are 13 coastal earth
stations coordinated by the Operations Control Center in London
provide services to more than 4,000 ship stations. Most of these
stations are 1.0 m in diameter, with 23 dB gain. The system
supports data transmission up to 56 kbps [8].
Due to small antenna size on ships and severe fading
environment error coding becomes essential. Comprehensive
transmission channel modeling, analysis and simulation were
provided by researchers at DFVLR. In addition, modulation and
coding scheme for maritime satellite channel were evaluated. BPSK
with differential coding were selected, and rate 1/2 constraint
length 7 convolutional with interleaved Viterbi decoding as well as
multiple burst error correcting Reed-Solomon code were recommended
[9]. At present the INMARSAT system contains a (63, 57) BCH code
for assignment and request messages, a (63, 39) BCH code for
channel request messages. The ship-to-shore 56 kbps data
transmission uses the convolutional code with soft decision. Rate
3/4 decoders are also implemented [6].
4.0 MOLNIYA-STATSIONAR
At least one hundred MOLNIYA satellites, over three series,
were built and launched by the Soviet Union since 1965. Since 1970
MOLNIYA systems have provided international services mostly to
neighboring U.S.S.R. countries. Since 1975 STATSIONAR satellites
have been continuously launched into the 80's.
STATSIONAR satellites have associated a number of ground
station networks including Orbita, Ekran and Moskva. Both MOLNIYA
and STATSIONAR satellite systems operated on the Intersputnik
network for international communication. The Intersputnik network
includes most communist east European and Asian nations with close
relation to the Soviet Union such as Cuba.
Among other technical details the MOLNIYA and STATSIONAR
satellites differ in orbits. MOLNIYA systems operate on an
elliptical inclined orbit and 62-65 degree inclination for power
conservation and earth coverage. The STATSIONAR satellites are
operated on the synchronous equatorial orbit. The STATSIONAR has
three system variations: RADUGA, EKRAN, and GORIZONT. Each system
variation has a number of series.
For example, Raduga 20, EKRAN 20 or GORIZONT 20. The
STATSIONAR satellites operation 5.7/6.2 GHz and 3.4/3.9 GHz bands.
Although it is difficult to get detail information on these
satellites some data is available from the U.S. Congressional
Research Reports on Soviet Space Programs and other references
cited by Martin [I0]. As far as modulation and coding are concern,
it is most likely phase modulation with convoiutional coding have
been used for their digital systems. This is judged from other
scientific journals published in the U.S.S.R.
318
5.0 EUTELSAT
With 26 signatories the system was formally established in
1985 by the European Conference of Post and Telecommunication
Organization (CEPT) and operated from Paris. Just as NASA has the
mandate to support U.S. industry, EUTELSAT was created to promote
satellite technology in Europe. From technical viewpoint EUTELSAT
has had close association with the European Space Agency (ESA).
The EUTELSAT TDMA system is operational since 1987.
The EUTELSAT system has four satellites in orbit and each
satellitehas ten transponders. Each transponder has 80 MHz or 72
MHz usable bandwidth. The system is operated at Ku-band. Each
EUTELSAT satellite has three spot beams with both vertical and
horizontal polarization. The second version of the EUTELSAT system
is scheduled to be operational in 1990. The revised system has
five satellites totaling sixteen transponders, nine of them with 36
MHz bandwidth and system is capable of controlling 29 traffic
stations and each station can monitor 7 transponders. The
countries (stations) can communicate through this system are:
Austria (Aflenz), Belgium-Netherland-Luxembourg (Lessive), Clrprus
(Makarios), France (Bercenay-en-othe), Germany (Usingen), Italy
(Fucino), Portugal (Sintra), Spain (Guadalajara),
Sweden-Denmark-Finland- Norway (AEGSTA), Turkey (Ankara), and
United Kingdom (Madley) Ill, 12]. Seven of the transponders have
72 MHz usable bandwidth with a 50W TWTA, the EUTELSAT II has the
unique switchable beam coverages. For narrow spot beam 50 dBW
e.i.r.p, from the satellite is obtainable. For wide beam,
coverage, 44 dBW is expected at edge of coverage. With EUTELSAT II
satellites, the TDMA stations have diameters of llm with G/T of 37
dB/K. The modulation for EUTELSAT digital systems is QPSK, and the
error coding is the rate 7/8 (128, 112) BCH code as used in the
INTELSAT TDMA system. Except the transmission rate of the EUTELSAT
system is lower at 24.576 Mbps.
6.0 ORION
The ORION satellite system is planned to be implemented for
international public telecommunication services between U.S., the
U.K. and other possible countries in North America and Europe. To
be expected operational in 1992 the ORION satellites are to be
located at 322.5°E/37.5°W and 313°E/47.0°W in orbit. These
satellites use 14 GHz for uplink and 11.45 - 12.2 GHz and
12.5-12.75 GHz for downlink. Each ORION satellite has 34
transponders in eight fixed beams. The bandwidth of each satellite
is 2 GHz. Every satellite is to be operated at Ku-band. The
satellites are designed to operate in both horizontal and vertical
polarizations. The system is designed to provide digital services
primary to VSAT stations with size from 1.2m to 1.8m. TVRO
stations are of 0.85m. The maximum e.i.r.p, of a ORION satellite
is 54.7 dBW.
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Modulation for the ORION depends on the carrier type and
information rate. For television services there are 17.5, 30, and
36 MHz analog FM bandwidths with frequency deviations of 7.5, 19
and 25 MHz respectively. Digital video is transmitted at 44.7 Mbps
with QPSK. For information rates of less than 8 Mbps both BPSK and
QPSK can be used. For data rate at 8 Mbps 80PSK will be used,
For data rates between 40 Mbps to 60 Mbps, 16 QAM is proposed. For
140 Mbps, 64 QAM modulation will be implemented. Depending on the
modulation scheme both rate 1/2 and rate 3/4 convolutional codes
are used for error corrections.
7.0 Concluding Remarks
Based on Westar VI series satellites the first ASISAT system
is due to launch in the Spring of 1990 by the Chinese Long March
III. The northern beam of ASIASAT intends to cover most China,
India, Japan and the Northern part of Southeast Asia. The southern
beam covers Thailand, Pakistan and may be Iran. Half of the
ASIASAT system capacity may be expected to be used for television
distribution.
ASIASAT has twenty four 36 MHz bandwidth transponders with
dual polarization frequency reuse. Transmitters are operated at
3702 to 4198 MHz and the receivers are operated at 5927 to 6423
MHz. At edge of coverage the e.i.r.p per transponder is 34.5 dBW.
ARABSAT came into existence at the end of 1976 through the
twenty two countries of the League of Arab States. Two satellites
were launched in 1984. The technology of ARABSAT satellite
centered around INTELSAT V and Telecom I. The communication
subsystem uses C-band with one additional downlink at 2.5 GHz.
Modulation is FM without channel coding.
ASTRA is operational since February 1989. The system is a
Luxembourg based broadcasting network for the European continent.
There are scrambling devices used in ASTRA system to black out the
unintended receivers. 50,000 TVRO with such decoder are expected
in 1989.
PanAmSat has been operational since June 1988 with a 24 -
hour-per-day English language news service through Cable News
Network(CNN). PanAmSat is in the process to expand the coverages
to Peru, the Dominican Republic and Costa Rica, The digital
carriers of PanAmSat system can also be operated from 64 khps to
2.0 48 Mbps with QPSK modulation throughout. Error correcting.
Code used are rate 1/2 constraint length 7 convolutional codes
either with Viterbi decoding or sequential decoding. The choices
of modulation and coding in the PanAmSat system are actually left
to the users.
HISPASAT is recently proposed for 1992 by Spain to provide
television services covering not only the country of Spain, but
also Europe, North and South America. Thus it is classified here
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as an international system. HISPASAT intends to use 1.2m to 4.5m
earth stations at Ku band, and 2.0m to 2.5m antennas for television
receive only. At C-band the system intends to have 2.6m to 7.0
earth stations. Technical details such as modulation and coding
are not yet available.
From a brief review on international satellite communication
systems in this paper, it is not very exciting to report the fact
that with all the variation and technological advancement in
modulation and error coding, very little has been actually
introduced into these practical systems. It is time for modulation
and coding experts to educate system decision makers to look beyond
what has been done and to show what can be done. The NASA
Conference on Advanced Modulation and Coding Technology is an
important forum not only for sponsored industry briefing, but also
a focal point of new modulation and coding techniques to be
recommended for future satellite applications world wide.
321
References:
[i] Pelion, J. and Wu, W. W. "The Challenge of 21st Century
Satellite Communications: INTELSAT Enters the Second
Millenniam", IEEE Journal on Selected Areas in
Communications, Vol. SAC-5, No. 4, May 1987
[2] Wu, W. W., Elements of Diqital Satellite Communication,
Vol.l 1984, Vol. II 1985, Computer Science Press
[31 Perillan, L. B. and Wu, W. W., "INTELSAT Services and Their
Evolution" Proceedings of 1987 ICC.
[4] Special Issue on INTELSAT TDMA/DSI, International Jr. on
Satellite Comm. Vol. 3, No. 1 @ 2, Jan/June 1985
[5] Special Issue on IDR, Intl. Jr. Satellite Comm., Vol. 6. No.
4, Oct/Dec 1988.
[6] Wu, W. W., Haccound, D., Peile , R and Hirata, Y., "Coding
for Satellite Communications" IEEE Journal on Selected
Areas in Communication, Vol, SAC-5 No. 4, May 1987.
[7] Lundberg, O. "Mobile Satellite Services: International
Co-ordination, Co-operation and Competition" Proceeding of
the mobile satellite conference, May 1988.
[8] Ghais, A., Berzins, G., and Wright, D., "INMARSAT and the
Future of Mobile Satellite Services", IEEE Jr. of selected
Areas in Satellite Communications Vol. SAC-5, No. 4 May 1987.
[9] Hagenauer, J., Dolainsky, F., Lutz, E., Papke, W., and
Schweikert, R. "The Maritime Satellite Communicatio Channel
- Model, Performance of Modulation and Coding", IEEE Jr. of
selected Areas in Satellite Communications Vol. SAC-5, No. 4
May 1987.
[I0] Martin, D. Communication Satellites 1958-1988, Aerospace
Corporation, 1988.
[11] Carsuro, A. "The European Telecommunications Satellite
Organization", Satellites International Macmillan-Press Ltd.
1988
[12] Celebiler, M., Fiedler, S., and Fresia "Testing of a TDMA
System: The EUTELSAT Experience:, ICDSC-7, Munich, May 1986.
322
/SATELLITE LOCATIONS
(Geostationary ocbit, equatorial plane)
0o
180 °
*" FUTURE LOCATION
FIGURE 1"
323
TABLE 1: INTELSAT GATEWAYS
Type
LARGE
(Country)
I II I I
Minimum
Earth Station Antenna Size G/T
Standard (m) (dBI ° K)
A 15-32 35.0
C 11-30 37.0
B 11-13 31.7
Services
Frequency
Bands
(GHz)
Telephony, data 6/4
TV, IBS
Telephony, data 14111 &12
TV, IBS
Telephony, data 6/4
TV, IBS
INTER-
MEDIATE
(Teleport)
F-3 9-10 29.0
E-3 8-10 34.0
F-2 7-6 27.0
E-2 5.0-7.0 29.0
Telephony, data 6/4
IBS, TV
Telephony, data 14/11&12
IBS, TV
Telephony, data 6/4
IBS, TV
Telephony, data 14/11&12
IBS, TV
SMALL
(Business)
F-1 4.5-5 22.7 IBS, TV 6/4
E-1 3.5 25.0 IBS, TV 14/11&12
D-1 4.5-5.5 22.7 VISTA 6/4
VSAT
TVRO
G 0.6-2.4 5.5
1.2-11 16
INTELNET 6/4;14/11&12
TV 6/4;14/11&12
DOMESTIC Z 0.6-32 5.5-16 Domestic 614;14/11&12
324
325
TABLE 3: INTELSAT VII MAIN FEATURES
3 dB more E.I.R.R than IS-VA
Hemi 29.0
Global 26.5
Zone 29,0
C-Spot NEW
Ku-Band Spot 41.0
C-Band all SSPA
Better linearity
Ku-Band TWTA/Linearizer
Better linearity ._ more capacity
3 Spot Beams
More flexible for domestic connectivity
TDMA
-_ 33 dBW
= 29 dBW
33 dBW
(36.3 dBW)
45 dBW
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International communications satellite systems

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