Satellite Networking
Introductory Lecture
http://web.uettaxila.edu.pk/CMS
/AUT2013/SatNet/
Overview
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Satellite technology has progressed tremendously
over the last 50 years since Arthur C. Clarke first
proposed its idea in 1945 in his article in Wireless
World.
Today, satellite systems can provide a variety of
services including broadband communications,
audio/video distribution networks, maritime
navigation, worldwide customer service and
support as well as military command and control.
Satellite Networks are also expected to play an
important role in the emerging 4G global
infrastructure providing the wide area coverage
necessary for the realization of the “Optimally
Connected Anywhere, Anytime” vision that drives
the growth of modern telecom industry.
Course Objectives
This course aims to:
 Provide a broad overview of the status of digital
satellite communications.
 Discuss main physical, architectural and
networking issues of satellite systems.
 Provide in-depth understanding of modern
modulation, coding and multiple access schemes.
 Review the state of the art in open research areas
such as satellite networking, internet over
satellite and satellite personal communications.
 Highlight trends and future directions of satellite
communication and networking including ISL and
conventional uplink and downlink communication
links
Course Pre-requisites
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Principles of digital communications
Telecom systems design
Section 1: The SATCOM Industry –
System Design Issues
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An Overview of Satellite Communications
• Examples of current military and commercial systems.
• Satellite orbits and transponder characteristics (LEO, MEO,
GEO)
• Traffic Connectivity: Mesh, Hub-Spoke, Point-to-Point,
Broadcast
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Basic satellite transmission theory
• Impairments of the Satellite Channel: Weather and Doppler
effects, Channel models.
• Communications Link Calculations: Definition of EIRP, Noise
temperature and G/T ratio, Eb/No. Transponder gain and SFD.
Link Budget Calculations. Down-link requirements. Design of
satellite links to achieve a specified performance.
• Earth Station Antenna types: Pointing/Tracking. Small
antennas at Ku band. FCC-Intelsat-ITU antenna requirements
and EIRP density limitations.
• Brief introduction to implementation issues: LNA, Up/down
converters, oscillator phase noise.
Section 2: Elements of Transponder
Design – The Baseband
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Physical Layer of the Transponder – The
Baseband System
Discussion on the theory of Digital
Communications: Modulation, Equalization and
FEC
• Digital Modulation Techniques: BPSK, QPSK, Nyquist
signal shaping.
• Overview of Bandwidth Efficient Modulation (BEM)
Techniques: M-ary PSK, Trellis Coded 8PSK, QAM.
• PSK Receiver Implementation issues: Carrier recovery,
phase slips, differential coding.
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Overview of Forward Error Correction (FEC):
Standard FEC types (Block and Convolution
Coding schemes, Viterbi Decoding), Coding Gain,
Concatenated coding, Turbo coding.
Section 3: Multiple Access Issues
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Spread Spectrum Techniques: Military and
commercial use of spread-spectrum. DirectSequence PN, Frequency-Hop and CDMA
systems.
Principles of Multiple Access Communications
• Multiplexing & Multiple Access FDD/TDD, FDMA, TDMA
• Concepts of Random Access: ALOHA, CSMA
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Multiple Access Techniques: FDMA, TDMA, CDMA.
DAMA and Bandwidth-on-Demand (BoD).
TDMA Networks: Time Slots, Preambles,
Suitability for DAMA and BoD.
Section 4: SATCOM Networks and
Services
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Satellite Communication Systems &
Networks
• Characteristics of IP and TCP/UDP over
satellite: Unicast and Multicast. Need for
Performance
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Enhancing Proxy (PEP) techniques.
• VSAT Networks and their system
characteristics.
• DVB standards and MF-TDMA
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The Future of SATCOM
• SATCOM’s role in the emerging 4G Information
and Communications (ICT) infrastructure.
Text Book
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Title: The Satellite Communication Applications
Handbook
Author: Bruce R. Elbert
ISBN: 1580534902
EAN: 9781580534901
Publisher:
Artech House Publishers
Reference Books
Title: Satellite Communications
 Author: Dennis Roddy
 ISBN: 0071371761
 EAN: 9780071371766
 Publisher:
McGraw-Hill Professional
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Reference Books
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Title: Satellite Communication Engineering
Author: Michael O. Kolawole
ISBN: 082470777X
EAN: 9780071371766
Publisher:
Marcel Dekker, Inc.
Pioneers in Satellite
Communication
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Konstantin Tsiolkovsky (1857 - 1935)
Russian visionary of space flight First described the multistage rocket as means of achieving orbit.
• Link: The life of Konstantin Eduardovitch Tsiolkovsky
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Hermann Noordung (1892 - 1929)
Postulated the geostationary orbit.
• Link: The Problem of Space Travel: The Rocket Motor
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Arthur C. Clarke (1917 – 19 March 2008)
Postulated the entire concept of international satellite
telecommunications from geostationary satellite orbit
including coverage, power, services, solar eclipse.
• Link: "Wireless World" (1945)
Satellite History Calendar
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1957
• October 4, 1957: - First satellite - the Russian Sputnik 01
• First living creature in space: Sputnik 02
1958
• First American satellite: Explorer 01
• First telecommunication satellite: This satellite broadcast a taped message: Score
1959
• First meteorology satellite: Explorer 07
1960
• First successful passive satellite: Echo 1
• First successful active satellite: Courier 1B
• First NASA satellite: Explorer 08
April 12, 1961: - First man in space
1962
• First telephone communication & TV broadcast via satellite: Echo 1
• First telecommunication satellite, first real-time active, AT&T: Telstar 1
• First Canadian satellite: Alouette 1
• On 7th June 1962 at 7:53p the two-stage rocket; Rehbar-I was successfully launched from
Sonmiani Rocket Range. It carried a payload of 80 pounds of sodium and soared to about 130
km into the atmosphere. With the launching of Rehbar-I, Pakistan had the honour of
becoming the third country in Asia and the tenth in the world to conduct such a launching
after USA, USSR, UK, France, Sweden, Italy, Canada, Japan and Israel.
• Rehbar-II followed a successful launch on 9th June 1962
1963
• Real-time active: Telstar 2
1964
• Creation of Intelsat
• First geostationary satellite, second satellite in stationary orbit: Syncom 3
• First Italian satellite: San Marco 1
Satellite History Calendar
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1965
• Intelsat 1 becomes first commercial comsat: Early Bird
• First real-time active for USSR: Molniya 1A
1967
• First geostationary meteorology payload: ATS 3
1968
• First European satellite: ESRO 2B
July 21, 1969: - First man on the moon
1970
• First Japanese satellite: Ohsumi
• First Chinese satellite: Dong Fang Hong 01
1971
• First UK launched satellite: Prospero
• ITU-WARC for Space Telecommunications
• INTELSAT IV Launched
• INTERSPUTNIK - Soviet Union equivalent of INTELSAT formed
1974
• First direct broadcasting satellite: ATS 6
1976
• MARISAT - First civil maritime communications satellite service started
1977
• EUTELSAT - European regional satellite
• ITU-WARC for Space Telecommunications in the Satellite Service
1979
• Creation of Inmarsat
Satellite History Calendar
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1980
• INTELSAT V launched - 3 axis stabilized satellite built by Ford Aerospace
1983
• ECS (EUTELSAT 1) launched - built by European consortium supervised by ESA
1984
• UK's UNISAT TV DBS satellite project abandoned
• First satellite repaired in orbit by the shuttle: SMM
1985
• First Brazilian satellite: Brazilsat A1
• First Mexican satellite: Morelos 1
1988
• First Luxemburg satellite: Astra 1A
1989
• INTELSAT VI - one of the last big "spinners" built by Hughes
• Creation of Panamsat - Begins Service
• On 16 July 1990, Pakistan launched its first experimental satellite, BADR-I from China
1990
• IRIDIUM, TRITIUM, ODYSSEY and GLOBALSTAR S-PCN projects proposed - CDMA designs
more popular
• EUTELSAT II
1992
• OLYMPUS finally launched - large European development satellite with Ka-band, DBTV and Kuband SS/TDMA payloads - fails within 3 years
1993
• INMARSAT II - 39 dBW EIRP global beam mobile satellite - built by Hughes/British Aerospace
1994
• INTELSAT VIII launched - first INTELSAT satellite built to a contractor's design
• Hughes describe SPACEWAY design
• DirecTV begins Direct Broadcast to Home
1995
• Panamsat - First private company to provide global satellite services.
Satellite History Calendar
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1996
• INMARSAT III launched - first of the multibeam mobile satellites (built by GE/Marconi)
• Echostar begins Diresct Broadcast Service
1997
• IRIDIUM launches first test satellites
• ITU-WRC'97
1999
• AceS launch first of the L-band MSS Super-GSOs - built by Lockheed Martin
• Iridium Bankruptcy - the first major failure?
2000
• Globalstar begins service
• Thuraya launch L-band MSS Super-GSO
2001
• XM Satellite Radio begins service
• Pakistan’s 2nd Satellite, BADR-B was launched on 10 Dec 2001 at 9:15a from Baikonour
Cosmodrome, Kazakistan
2002
• Sirius Satellite Radio begins service
• Paksat-1, was deployed at 38 degrees E orbital slot in December 2002, Paksat-1, was
deployed at 38 degrees E orbital slot in December 2002
2004
• Teledesic network planned to start operation
2005
• Intelsat and Panamsat Merge
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VUSat OSCAR-52 (HAMSAT) Launched
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CubeSat-OSCAR 56 (Cute-1.7) Launched
K7RR-Sat launched by California Politechnic University
2006
2007
• Prism was launched by University of Tokyo
2008
• COMPASS-1; a project of Aachen University was launched from Satish Dawan Space Center,
India. It failed to achieve orbit.
Intelsat
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INTELSAT is the original "Inter-governmental Satellite
organization". It once owned and operated most of the
World's satellites used for international communications,
and still maintains a substantial fleet of satellites.
INTELSAT is moving towards "privatization", with increasing
competition from commercial operators (e.g. Panamsat,
Loral Skynet, etc.).
INTELSAT Timeline:
Interim organization formed in 1964 by 11 countries
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Permanent structure formed in 1973
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Commercial "spin-off", New Skies Satellites in 1998
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Full "privatization" by April 2001
INTELSAT has 143 members and signatories listed here.
Intelsat Structure
Eutelsat
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Permanent General Secretariat opened September 1978
Intergovernmental Conference adopted definitive statutes with 26
members on 14 May 1982
Definitive organization entered into force on 1 September 1985
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General Secretariat -> Executive Organ
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Executive Council -> EUTELSAT Board of Signatories
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Secretary General -> Director General
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Current DG is Giuliano Berretta
Currently almost 50 members
Moving towards "privatization"
Limited company owning and controlling of all assets and activities
Also a "residual" intergovernmental organization which will ensure that
basic principles of pan-European coverage, universal service, nondiscrimination and fair competition are observed by the company
Eutelsat Structure
Communication Satellite
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A Communication Satellite can be
looked upon as a large microwave
repeater
It contains several transponders
which listens to some portion of
spectrum, amplifies the incoming
signal and broadcasts it in another
frequency to avoid interference with
incoming signals.
Motivation to use Satellites
Satellite Missions
Source: Union of Concerned Scientists [www.ucsusa.org]
Satellite Microwave Transmission
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Satellites can relay signals over a
long distance
Geostationary Satellites
• Remain above the equator at a height of
about 22300 miles (geosynchronous
orbits)
• Travel around the earth in exactly the
same time, the earth takes to rotate
Satellite System Elements
Space Segment
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Satellite Launching Phase
Transfer Orbit Phase
Deployment
Operation
• TT&C - Tracking Telemetry and
Command Station
• SSC - Satellite Control Center, a.k.a.:
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OCC - Operations Control Center
SCF - Satellite Control Facility
Retirement Phase
Ground Segment
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Collection of facilities, Users and Applications
Earth Station = Satellite Communication Station
(Fixed or Mobile)
Satellite Uplink and Downlink
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Downlink
• The link from a satellite down to one or more
ground stations or receivers
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Uplink
• The link from a ground station up to a satellite.
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Some companies sell uplink and downlink
services to
• television stations, corporations, and to other
telecommunication carriers.
• A company can specialize in providing uplinks,
downlinks, or both.
Satellite Uplink and Downlink
Satellite Communication
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Source: Cryptome [Cryptome.org]
When using a satellite for long
distance communications, the
satellite acts as a repeater.
An earth station transmits the
signal up to the satellite
(uplink), which in turn
retransmits it to the receiving
earth station (downlink).
Different frequencies are used
for uplink/downlink.
Satellite Transmission Links
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Earth stations Communicate by
sending signals to the satellite on an
uplink
The satellite then repeats those
signals on a downlink
The broadcast nature of downlink
makes it attractive for services such
as the distribution of TV programs
Direct to User Services
One way Service (Broadcasting)
Two way Service (Communication)
Satellite Signals
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Used to transmit signals and data
over long distances
}
• Weather forecasting
• Television broadcasting
• Internet communication
• Global Positioning Systems
Data
Communication
Satellite Transmission Bands
Frequency Band
C
Downlink
Uplink
3,700-4,200 MHz 5,925-6,425 MHz
Ku
11.7-12.2 GHz
14.0-14.5 GHz
Ka
17.7-21.2 GHz
27.5-31.0 GHz
The C band is the most frequently used. The Ka and Ku bands are reserved
exclusively for satellite communication but are subject to rain attenuation
Types of Satellite Orbits
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Based on the inclination, i, over the equatorial
plane:
• Equatorial Orbits above Earth’s equator (i=0°)
• Polar Orbits pass over both poles (i=90°)
• Other orbits called inclined orbits (0°<i<90°)
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Based on Eccentricity
• Circular with centre at the earth’s centre
• Elliptical with one foci at earth’s centre
Types of Satellite based Networks
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Based on the Satellite Altitude
• GEO – Geostationary Orbits
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36000 Km = 22300 Miles, equatorial, High latency
• MEO – Medium Earth Orbits
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High bandwidth, High power, High latency
• LEO – Low Earth Orbits
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Low power, Low latency, More Satellites, Small
Footprint
• VSAT
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Very Small Aperture Satellites
• Private WANs
Satellite Orbits
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Source: Federation of American Scientists [www.fas.org]
Geosynchronous Orbit
(GEO): 36,000 km above
Earth, includes commercial
and military communications
satellites, satellites providing
early warning of ballistic
missile launch.
Medium Earth Orbit (MEO):
from 5000 to 15000 km,
they include navigation
satellites (GPS, Galileo,
Glonass).
Low Earth Orbit (LEO): from
500 to 1000 km above Earth,
includes military intelligence
satellites, weather satellites.
Satellite Orbits
GEO - Geostationary Orbit
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In the equatorial plane
Orbital Period = 23 h 56 m 4.091 s
= 1 sidereal day*
Satellite appears to be stationary over any point
on equator:
• Earth Rotates at same speed as Satellite
• Radius of Orbit r = Orbital Height + Radius of Earth
• Avg. Radius of Earth = 6378.14 Km
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3 Satellites can cover the earth (120° apart)
NGSO - Non Geostationary Orbits
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Orbit should avoid
Van Allen radiation
belts:
• Region of charged
particles that can
cause damage to
satellite
• Occur at
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~2000-4000 km and
~13000-25000 km
LEO - Low Earth Orbits
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Circular or inclined orbit with < 1400 km
altitude
• Satellite travels across sky from horizon to
horizon in 5 - 15 minutes => needs handoff
• Earth stations must track satellite or have
Omni directional antennas
• Large constellation of satellites is needed for
continuous communication (66 satellites
needed to cover earth)
• Requires complex architecture
• Requires tracking at ground
HEO - Highly Elliptical Orbits
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HEOs (i = 63.4°) are suitable to
provide coverage at high latitudes
(including North Pole in the
northern hemisphere)
Depending on selected orbit (e.g.
Molniya, Tundra, etc.) two or
three satellites are sufficient for
continuous time coverage of the
service area.
All traffic must be periodically
transferred from the “setting”
satellite to the “rising” satellite
(Satellite Handover)
Satellite Orbits
Source: Union of Concerned Scientists [www.ucsusa.org]
Why Satellites remain in Orbits
Advantages of Satellite
Communication
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Can reach over large geographical area
Flexible (if transparent transponders)
Easy to install new circuits
Circuit costs independent of distance
Broadcast possibilities
Temporary applications (restoration)
Niche applications
Mobile applications (especially "fill-in")
Terrestrial network "by-pass"
Provision of service to remote or underdeveloped
areas
User has control over own network
1-for-N multipoint standby possibilities
Disadvantages of Satellite
Communication
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Large up front capital costs (space
segment and launch)
Terrestrial break even distance
expanding (now approx. size of
Europe)
Interference and propagation delay
Congestion of frequencies and orbits
When to use Satellites
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When the unique features of satellite communications
make it attractive
When the costs are lower than terrestrial routing
When it is the only solution
Examples:
Communications to ships and aircraft (especially safety
communications)
TV services - contribution links, direct to cable head, direct
to home
Data services - private networks
Overload traffic
Delaying terrestrial investments
1 for N diversity
Special events
When to use Terrestrial
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PSTN - satellite is becoming increasingly
uneconomic for most trunk telephony routes
but, there are still good reasons to use
satellites for telephony such as: thin routes,
diversity, very long distance traffic and remote
locations.
Land mobile/personal communications - in
urban areas of developed countries new
terrestrial infrastructure is likely to dominate
(e.g. GSM, etc.)
but, satellite can provide fill-in as terrestrial
networks are implemented, also provide similar
services in rural areas and underdeveloped
countries
Frequency Bands Allocated to the
FSS
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Frequency bands are allocated to different services at World
Radio-communication Conferences (WRCs).
Allocations are set out in Article S5 of the ITU Radio
Regulations.
It is important to note that (with a few exceptions) bands
are generally allocated to more than one radio services.
CONSTRAINTS
• Bands have traditionally been divided into “commercial" and
"government/military" bands, although this is not reflected in
the Radio Regulations and is becoming less clear-cut as
"commercial" operators move to utilize "government" bands.
Q&A
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????
Assignment #1
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Read the paper of Arthur C. Clark and
summarize his suggestions to support
Satellite for Communication purposes
Mail: adeel.akram@uettaxila.edu.pk
Mail Subject: SatNet