Satellite CommunicationSatellite Communication

Introductory LectureIntroductory Lecture

http://web.uettaxila.edu.pk/CMS/AUT2011/teSCms http://web.uettaxila.edu.pk/CMS/AUT2011/teSCms

OverviewOverview 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 systems 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 ObjectivesCourse 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.

Section 1: The SATCOM Industry – System Design Issues

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 Basic satellite transmission theory

• Impairments of the Satellite Channel: Weather and Doppler effects, Channel models.

• Communications Link Calculations: Definition of EIRP, Noise temperature etc. 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 etc.

Section 2: Elements of Transponder Design – The Baseband

Physical Layer of the Transponder – The Baseband System

Introduction to 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. 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

Spread Spectrum Techniques: Military and commercial use of spread-spectrum. Direct-Sequence, Frequency-Hop and CDMA systems.

Principles of Multiple Access Communications• Multiplexing & Multiple Access FDD/TDD, FDMA, TDMA• Concepts of Random Access: ALOHA, CSMA

Multiple Access Techniques: FDMA, TDMA, CDMA. Demand Assigned Multiple Access (DAMA) and Bandwidth-on-Demand (BoD).

TDMA Networks: Time Slots, Preambles, Suitability for DAMA and BoD.

Section 4: SATCOM Networks and Services

Satellite Communication Systems & Networks• Characteristics of IP and TCP/UDP over

satellite: Unicast and Multicast. Need for Performance

Performance Enhancing Proxy (PEP) techniques.• VSAT Networks and their system

characteristics.• DVB standards and MultiFreq-TDMA

The Future of SATCOM• SATCOM’s role in the emerging 4G Information

and Communications (ICT) infrastructure.

Section 5: Space Remote Sensing

A survey of historical and current remote sensing systems will be presented, covering all major governmental and private systems.

The business of remote sensing, including system development, launch, and operational costs will be presented, along with remote sensing market trends and user communities.

Text BookText Book

Title:Title: The Satellite Communication Applications The Satellite Communication Applications Handbook Handbook

Author:Author: Bruce R. Elbert Bruce R. Elbert ISBN:ISBN: 1580534902 1580534902 EAN:EAN: 9781580534901 9781580534901 Publisher:Publisher:

Artech House PublishersArtech House Publishers

Reference BooksReference Books

Title:Title: Satellite Communications Satellite Communications Author:Author: Dennis Roddy Dennis Roddy ISBN:ISBN: 0071371761 0071371761 EAN:EAN: 9780071371766 9780071371766 Publisher:Publisher:

McGraw-Hill ProfessionalMcGraw-Hill Professional

Reference BooksReference Books Title:Title: Satellite Communication Engineering Satellite Communication Engineering Author:Author: Michael O. Kolawole Michael O. Kolawole ISBN:ISBN: 082470777X 082470777X EAN:EAN: 9780071371766 9780071371766 Publisher:Publisher:

Marcel Dekker, Inc.Marcel Dekker, Inc.

Pioneers in Satellite Pioneers in Satellite CommunicationCommunication

Konstantin Tsiolkovsky (1857 - 1935)Konstantin Tsiolkovsky (1857 - 1935)Russian visionary of space flight First described the multi-Russian visionary of space flight First described the multi-stage rocket as means of achieving orbit.stage rocket as means of achieving orbit.• Link: The life of Konstantin Eduardovitch TsiolkovskyLink: The life of Konstantin Eduardovitch Tsiolkovsky

   Hermann Noordung (1892 - 1929)Hermann Noordung (1892 - 1929)

Postulated the geostationary orbit.Postulated the geostationary orbit.• Link: The Problem of Space Travel: The Rocket MotorLink: The Problem of Space Travel: The Rocket Motor

Arthur C. Clarke (1917 – 19 March 2008)Arthur C. Clarke (1917 – 19 March 2008)Postulated the entire concept of international satellite Postulated the entire concept of international satellite telecommunications from geostationary satellite orbit telecommunications from geostationary satellite orbit including   coverage, power, services, solar eclipse.including   coverage, power, services, solar eclipse.• Link: "Wireless World" (1945)Link: "Wireless World" (1945)

Satellite History CalendarSatellite History Calendar 1957 1957

• October 4, 1957: - First satellite - the Russian Sputnik 01October 4, 1957: - First satellite - the Russian Sputnik 01• First living creature in space: Sputnik 02First living creature in space: Sputnik 02

19581958• First American satellite: Explorer 01First American satellite: Explorer 01• First telecommunication satellite: This satellite broadcast a taped message: ScoreFirst telecommunication satellite: This satellite broadcast a taped message: Score

19591959• First meteorology satellite: Explorer 07First meteorology satellite: Explorer 07

19601960• First successful passive satellite: Echo 1First successful passive satellite: Echo 1• First successful active satellite: Courier 1BFirst successful active satellite: Courier 1B• First NASA satellite: Explorer 08First NASA satellite: Explorer 08

April 12, 1961: - First man in spaceApril 12, 1961: - First man in space 19621962

• First telephone communication & TV broadcast via satellite: Echo 1First telephone communication & TV broadcast via satellite: Echo 1• First telecommunication satellite, first real-time active, AT&T: Telstar 1First telecommunication satellite, first real-time active, AT&T: Telstar 1• First Canadian satellite: Alouette 1First Canadian satellite: Alouette 1• On 7On 7thth June 1962 at 7:53p the two-stage rocket; Rehbar-I was successfully launched from Sonmiani Rocket 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 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 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. world to conduct such a launching after USA, USSR, UK, France, Sweden, Italy, Canada, Japan and Israel.

• Rehbar-II followed a successful launch on 9Rehbar-II followed a successful launch on 9thth June 1962 June 1962 19631963

• Real-time active: Telstar 2Real-time active: Telstar 2 19641964

• Creation of IntelsatCreation of Intelsat• First geostationary satellite, second satellite in stationary orbit: Syncom 3First geostationary satellite, second satellite in stationary orbit: Syncom 3• First Italian satellite: San Marco 1First Italian satellite: San Marco 1

Satellite History CalendarSatellite History Calendar 19651965

• Intelsat 1 becomes first commercial comsat: Early BirdIntelsat 1 becomes first commercial comsat: Early Bird• First real-time active for USSR: Molniya 1AFirst real-time active for USSR: Molniya 1A

19671967• First geostationary meteorology payload: ATS 3First geostationary meteorology payload: ATS 3

19681968• First European satellite: ESRO 2BFirst European satellite: ESRO 2B

July 21, 1969: - First man on the moonJuly 21, 1969: - First man on the moon

19701970• First Japanese satellite: OhsumiFirst Japanese satellite: Ohsumi• First Chinese satellite: Dong Fang Hong 01First Chinese satellite: Dong Fang Hong 01

19711971• First UK launched satellite: ProsperoFirst UK launched satellite: Prospero• ITU-WARC for Space Telecommunications ITU-WARC for Space Telecommunications • INTELSAT IV Launched INTELSAT IV Launched • INTERSPUTNIK - Soviet Union equivalent of INTELSAT formed INTERSPUTNIK - Soviet Union equivalent of INTELSAT formed

19741974• First direct broadcasting satellite: ATS 6First direct broadcasting satellite: ATS 6

1976 1976 • MARISAT - First civil maritime communications satellite service started MARISAT - First civil maritime communications satellite service started

1977 1977 • EUTELSAT - European regional satellite EUTELSAT - European regional satellite • ITU-WARC for Space Telecommunications in the Satellite Service ITU-WARC for Space Telecommunications in the Satellite Service

19791979• Creation of Inmarsat (Creation of Inmarsat (International Marine Satellite)

Satellite History CalendarSatellite History Calendar 1980 1980 

• INTELSAT V launched - 3 axis stabilized satellite built by Ford Aerospace INTELSAT V launched - 3 axis stabilized satellite built by Ford Aerospace 1983 1983 

• ECS (EUTELSAT 1) launched - built by European consortium supervised by ESA ECS (EUTELSAT 1) launched - built by European consortium supervised by ESA 1984 1984 

• UK's UNISAT TV DBS satellite project abandoned UK's UNISAT TV DBS satellite project abandoned • First satellite repaired in orbit by the shuttle: SMMFirst satellite repaired in orbit by the shuttle: SMM

19851985• First Brazilian satellite: Brazilsat A1First Brazilian satellite: Brazilsat A1• First Mexican satellite: Morelos 1First Mexican satellite: Morelos 1

19881988• First Luxemburg satellite: Astra 1AFirst Luxemburg satellite: Astra 1A

1989 1989 • INTELSAT VI - one of the last big "spinners" built by HughesINTELSAT VI - one of the last big "spinners" built by Hughes• Creation of Panamsat - Begins ServiceCreation of Panamsat - Begins Service

19901990  • IRIDIUM, TRITIUM, ODYSSEY and GLOBALSTAR S-PCN projects proposed - CDMA designs more IRIDIUM, TRITIUM, ODYSSEY and GLOBALSTAR S-PCN projects proposed - CDMA designs more

popular popular • EUTELSAT II EUTELSAT II • On 16 July 1990, Pakistan launched its first experimental satellite, BADR-I from China On 16 July 1990, Pakistan launched its first experimental satellite, BADR-I from China

1992 1992 • OLYMPUS finally launched - large European development satellite with Ka-band, DBTV and Ku-OLYMPUS finally launched - large European development satellite with Ka-band, DBTV and Ku-

band SS/TDMA payloads - fails within 3 years band SS/TDMA payloads - fails within 3 years 1993 1993 

• INMARSAT II - 39 dBW EIRP global beam mobile satellite - built by Hughes/British Aerospace INMARSAT II - 39 dBW EIRP global beam mobile satellite - built by Hughes/British Aerospace 1994 1994 

• INTELSAT VIII launched - first INTELSAT satellite built to a contractor's design INTELSAT VIII launched - first INTELSAT satellite built to a contractor's design • Hughes describe SPACEWAY design Hughes describe SPACEWAY design • DirecTV begins Direct Broadcast to HomeDirecTV begins Direct Broadcast to Home

19951995• Panamsat - First private company to provide global satellite services.Panamsat - First private company to provide global satellite services.

Satellite History CalendarSatellite History Calendar 1996 1996 

• INMARSAT III launched - first of the multibeam mobile satellites (built by GE/Marconi) INMARSAT III launched - first of the multibeam mobile satellites (built by GE/Marconi) • Echostar begins Diresct Broadcast ServiceEchostar begins Diresct Broadcast Service

1997 1997 • IRIDIUM launches first test satellites IRIDIUM launches first test satellites • ITU-WRC'97 ITU-WRC'97

1999 1999 • AceS launch first of the L-band MSS Super-GSOs - built by Lockheed Martin AceS launch first of the L-band MSS Super-GSOs - built by Lockheed Martin • Iridium Bankruptcy - the first major failure? Iridium Bankruptcy - the first major failure?

2000 2000 • Globalstar begins service Globalstar begins service • Thuraya launch L-band MSS Super-GSOThuraya launch L-band MSS Super-GSO

20012001• XM Satellite Radio begins serviceXM Satellite Radio begins service• Pakistan’s 2Pakistan’s 2ndnd Satellite, BADR-B was launched on 10 Dec 2001 at 9:15a from Baikonour Satellite, BADR-B was launched on 10 Dec 2001 at 9:15a from Baikonour

Cosmodrome, Kazakistan Cosmodrome, Kazakistan 20022002

• Sirius Satellite Radio begins serviceSirius Satellite Radio begins service• Paksat-1, was deployed at 38 degrees E orbital slot in December 2002Paksat-1, was deployed at 38 degrees E orbital slot in December 2002

2004 2004 • Teledesic network planned to start operationTeledesic network planned to start operation

2005 2005 • Intelsat and Panamsat Merge Intelsat and Panamsat Merge • VUSat OSCAR-52 (HAMSAT) Launched VUSat OSCAR-52 (HAMSAT) Launched

20062006• CubeSat-OSCAR 56 (Cute-1.7) LaunchedCubeSat-OSCAR 56 (Cute-1.7) Launched• K7RR-Sat launched by California Politechnic UniversityK7RR-Sat launched by California Politechnic University

20072007• Prism was launched by University of Tokyo Prism was launched by University of Tokyo

20082008• COMPASS-1; a project of Aachen University was launched from Satish Dawan Space Center, COMPASS-1; a project of Aachen University was launched from Satish Dawan Space Center,

India. It failed to achieve orbit.India. It failed to achieve orbit.

IntelsatIntelsat INTELSAT is the original "INTELSAT is the original "International Telecommunications

Satellite Organization". It once owned and operated most of ". It once owned and operated most of the World's satellites used for international the World's satellites used for international communications, and still maintains a substantial fleet of communications, and still maintains a substantial fleet of satellites.satellites.

INTELSAT is moving towards "privatization", with increasing INTELSAT is moving towards "privatization", with increasing competition from commercial operators (e.g. Panamsat, competition from commercial operators (e.g. Panamsat, Loral Skynet, etc.).Loral Skynet, etc.).

INTELSAT Timeline:INTELSAT Timeline: Interim organization formed in 1964 by 11 countriesInterim organization formed in 1964 by 11 countries

Permanent structure formed in 1973Permanent structure formed in 1973

Commercial "spin-off", New Skies Satellites in 1998Commercial "spin-off", New Skies Satellites in 1998

Full "privatization" by April 2001 Full "privatization" by April 2001 INTELSAT has 143 members and signatories listed here.INTELSAT has 143 members and signatories listed here.

Intelsat StructureIntelsat Structure

EutelsatEutelsat Permanent General Secretariat opened September 1978 Permanent General Secretariat opened September 1978 Intergovernmental Conference adopted definitive statutes with 26 Intergovernmental Conference adopted definitive statutes with 26

members on 14 May 1982members on 14 May 1982 Definitive organization entered into force on 1 September 1985Definitive organization entered into force on 1 September 1985

General Secretariat -> Executive OrganGeneral Secretariat -> Executive Organ

Executive Council -> EUTELSAT Board of SignatoriesExecutive Council -> EUTELSAT Board of Signatories

Secretary General -> Director GeneralSecretary General -> Director General

Current DG is Current DG is Michel de Rosen Currently almost 50 membersCurrently almost 50 members Moving towards "privatization"Moving towards "privatization" Limited company owning and controlling of all assets and activitiesLimited company owning and controlling of all assets and activities

Also a "residual" intergovernmental organization which will ensure that Also a "residual" intergovernmental organization which will ensure that basic principles of pan-European coverage, universal service, non-basic principles of pan-European coverage, universal service, non-discrimination and fair competition are observed by the company discrimination and fair competition are observed by the company

Eutelsat StructureEutelsat Structure

Communication SatellitesCommunication Satellites

A Communication Satellite can be A Communication Satellite can be looked upon as a large microwave looked upon as a large microwave repeaterrepeater

It contains several transponders It contains several transponders which listens to some portion of which listens to some portion of spectrum, amplifies the incoming spectrum, amplifies the incoming signal and broadcasts it in another signal and broadcasts it in another frequency to avoid interference with frequency to avoid interference with incoming signals.incoming signals.

Motivation to use SatellitesMotivation to use Satellites

Source: Union of Concerned Scientists [www.ucsusa.org]Source: Union of Concerned Scientists [www.ucsusa.org]

Satellite MissionsSatellite Missions

Satellite Microwave TransmissionSatellite Microwave Transmission

Satellites can relay signals over a Satellites can relay signals over a long distancelong distance

Geostationary SatellitesGeostationary Satellites• Remain above the equator at a height of Remain above the equator at a height of

about 22300 miles (geosynchronous about 22300 miles (geosynchronous orbits)orbits)

• Travel around the earth in exactly the Travel around the earth in exactly the same time, the earth takes to rotatesame time, the earth takes to rotate

Satellite System ElementsSatellite System Elements

Space SegmentSpace Segment

Satellite Launching Phase Transfer Orbit Phase Deployment Operation

• TT&C - Tracking Telemetry and Command Station

• SSC - Satellite Control Center, a.k.a.: OCC - Operations Control Center SCF - Satellite Control Facility

Retirement Phase

Ground SegmentGround Segment Collection of facilities, Users and ApplicationsCollection of facilities, Users and Applications

Earth Station = Satellite Communication Station Earth Station = Satellite Communication Station (Fixed or Mobile)(Fixed or Mobile)

Satellite Uplink and DownlinkSatellite Uplink and Downlink

DownlinkDownlink• The link from a satellite down to one or more The link from a satellite down to one or more

ground stations or receiversground stations or receivers UplinkUplink

• The link from a ground station up to a satellite.The link from a ground station up to a satellite. Some companies sell uplink and downlink Some companies sell uplink and downlink

services to services to • television stations, corporations, and to other television stations, corporations, and to other

telecommunication carriers. telecommunication carriers. • A company can specialize in providing uplinks, A company can specialize in providing uplinks,

downlinks, or both. downlinks, or both.

Satellite Uplink and DownlinkSatellite Uplink and Downlink

Source: Cryptome [Cryptome.org]Source: Cryptome [Cryptome.org]

When using a satellite for long When using a satellite for long distance communications, the distance communications, the satellite acts as a repeater.satellite acts as a repeater.

An earth station transmits the An earth station transmits the signal up to the satellite signal up to the satellite (uplink), which in turn (uplink), which in turn retransmits it to the receiving retransmits it to the receiving earth station (downlink).earth station (downlink).

Different frequencies are used Different frequencies are used for uplink/downlink.for uplink/downlink.

Satellite CommunicationSatellite Communication

Satellite Transmission LinksSatellite Transmission Links

Earth stations Communicate by Earth stations Communicate by sending signals to the satellite on an sending signals to the satellite on an uplinkuplink

The satellite then repeats those The satellite then repeats those signals on a downlinksignals on a downlink

The broadcast nature of downlink The broadcast nature of downlink makes it attractive for services such makes it attractive for services such as the distribution of TV programsas the distribution of TV programs

Direct to User ServicesDirect to User Services

One way Service (Broadcasting)One way Service (Broadcasting) Two way Service (Communication)Two way Service (Communication)

Satellite SignalsSatellite Signals

Used to transmit signals and data Used to transmit signals and data over long distancesover long distances• Weather forecastingWeather forecasting• Television broadcastingTelevision broadcasting• Internet communicationInternet communication• Global Positioning SystemsGlobal Positioning Systems

Satellite Transmission BandsSatellite Transmission Bands

Frequency Band Downlink Uplink

C 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 OrbitsTypes of Satellite Orbits

Based on the inclination, i, over the equatorial plane:• Equatorial Orbits above Earth’s equator (i=0°)Equatorial Orbits above Earth’s equator (i=0°)• Polar Orbits pass over both poles (i=90°)Polar Orbits pass over both poles (i=90°)• Other orbits called inclined orbits (0°<i<90°)Other orbits called inclined orbits (0°<i<90°)

Based on EccentricityBased on Eccentricity• Circular with centre at the earth’s centreCircular with centre at the earth’s centre• Elliptical with one foci at earth’s centre Elliptical with one foci at earth’s centre

Types of Satellite based NetworksTypes of Satellite based Networks

Based on the Satellite AltitudeBased on the Satellite Altitude• GEO – Geostationary OrbitsGEO – Geostationary Orbits

36000 Km = 22300 Miles, equatorial, High latency 36000 Km = 22300 Miles, equatorial, High latency

• MEO – Medium Earth OrbitsMEO – Medium Earth Orbits High bandwidth, High power, High latency High bandwidth, High power, High latency

• LEO – Low Earth OrbitsLEO – Low Earth Orbits Low power, Low latency, More Satellites, Small Low power, Low latency, More Satellites, Small

FootprintFootprint

• VSATVSAT Very Small Aperture SatellitesVery Small Aperture Satellites

• Private WANsPrivate WANs

Source: Federation of American Scientists [www.fas.org]Source: Federation of American Scientists [www.fas.org]

Satellite OrbitsSatellite Orbits

Geosynchronous Orbit (GEO): Geosynchronous Orbit (GEO): 36,000 km above Earth, 36,000 km above Earth, includes commercial and includes commercial and military communications military communications satellites, satellites providing satellites, satellites providing early warning of ballistic early warning of ballistic missile launch.missile launch.

Medium Earth Orbit (MEO): Medium Earth Orbit (MEO): from 5000 to 15000 km, they from 5000 to 15000 km, they include navigation satellites include navigation satellites (GPS, Galileo, Glonass).(GPS, Galileo, Glonass).

Low Earth Orbit (LEO): from Low Earth Orbit (LEO): from 500 to 1000 km above Earth, 500 to 1000 km above Earth, includes military intelligence includes military intelligence satellites, weather satellites.satellites, weather satellites.

Satellite OrbitsSatellite Orbits

GEO - Geostationary OrbitGEO - Geostationary Orbit In the equatorial planeIn the equatorial plane

Orbital Period = 23 h 56 m 4.091 sOrbital Period = 23 h 56 m 4.091 s = 1 sidereal day*= 1 sidereal day*

Satellite appears to be stationary over any point Satellite appears to be stationary over any point on equator:on equator:• Earth Rotates at same speed as SatelliteEarth Rotates at same speed as Satellite• Radius of Orbit r = Orbital Height + Radius of EarthRadius of Orbit r = Orbital Height + Radius of Earth• Avg. Radius of Earth = 6378.14 KmAvg. Radius of Earth = 6378.14 Km

3 Satellites can cover the earth (120° apart)3 Satellites can cover the earth (120° apart)

NGSO - Non Geostationary OrbitsNGSO - Non Geostationary Orbits

Orbit should avoid Van Allen radiation belts:• Region of charged

particles that can cause damage to satellite

• Occur at ~2000-4000 km and ~13000-25000 km

LEO - Low Earth OrbitsLEO - Low Earth Orbits

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 OrbitsHEO - Highly Elliptical Orbits 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)

Source: Union of Concerned Scientists [www.ucsusa.org]Source: Union of Concerned Scientists [www.ucsusa.org]

Satellite OrbitsSatellite Orbits

Why Satellites remain in Orbits?Why Satellites remain in Orbits?

Advantages of Satellite Advantages of Satellite CommunicationCommunication

Can reach over large geographical areaCan reach over large geographical area Flexible (if transparent transponders) Flexible (if transparent transponders) Easy to install new circuits Easy to install new circuits Circuit costs independent of distance Circuit costs independent of distance Broadcast possibilities Broadcast possibilities Temporary applications (restoration) Temporary applications (restoration) Niche applications Niche applications Mobile applications (especially "fill-in") Mobile applications (especially "fill-in") Terrestrial network "by-pass" Terrestrial network "by-pass" Provision of service to remote or underdeveloped Provision of service to remote or underdeveloped

areas areas User has control over own network User has control over own network 1-for-N multipoint standby possibilities 1-for-N multipoint standby possibilities

Disadvantages of Satellite Disadvantages of Satellite CommunicationCommunication

Large up front capital costs (space Large up front capital costs (space segment and launch) segment and launch)

Terrestrial break even distance Terrestrial break even distance expanding (now approx. size of expanding (now approx. size of Europe) Europe)

Interference and propagation delay Interference and propagation delay Congestion of frequencies and orbits Congestion of frequencies and orbits

When to use SatellitesWhen to use Satellites When the unique features of satellite communications When the unique features of satellite communications

make it attractive make it attractive When the costs are lower than terrestrial routing When the costs are lower than terrestrial routing When it is the only solution When it is the only solution Examples:Examples:

• Communications to ships and aircraft (especially safety Communications to ships and aircraft (especially safety communications) communications)

• TV services - contribution links, direct to cable head, direct TV services - contribution links, direct to cable head, direct to hometo home

• Data services - private networks Data services - private networks • Overload traffic Overload traffic • Delaying terrestrial investments Delaying terrestrial investments • 1 for N diversity 1 for N diversity • Special events Special events

When to use TerrestrialWhen to use Terrestrial PSTN - satellite is becoming increasingly PSTN - satellite is becoming increasingly

uneconomic for most trunk telephony routes uneconomic for most trunk telephony routes but, there are still good reasons to use satellites but, there are still good reasons to use satellites

for telephony such as: thin routes, diversity, for telephony such as: thin routes, diversity, very long distance traffic and remote locations. very long distance traffic and remote locations.

Land mobile/personal communications - in Land mobile/personal communications - in urban areas of developed countries new urban areas of developed countries new terrestrial infrastructure is likely to dominate terrestrial infrastructure is likely to dominate (e.g. GSM, etc.) (e.g. GSM, etc.)

but, satellite can provide fill-in as terrestrial but, satellite can provide fill-in as terrestrial networks are implemented, also provide similar networks are implemented, also provide similar services in rural areas and underdeveloped services in rural areas and underdeveloped countries countries

Frequency Bands Allocated to the Frequency Bands Allocated to the FSSFSS

Frequency bands are allocated to different services at Frequency bands are allocated to different services at World Radio-communication Conferences (WRCs). World Radio-communication Conferences (WRCs).

Allocations are set out in Article S5 of the ITU Radio Allocations are set out in Article S5 of the ITU Radio Regulations. Regulations.

It is important to note that (with a few exceptions) bands It is important to note that (with a few exceptions) bands are generally allocated to more than one radio services.are generally allocated to more than one radio services.

CONSTRAINTSCONSTRAINTS • Bands have traditionally been divided into “commercial" and Bands have traditionally been divided into “commercial" and

"government/military" bands, although this is not reflected in "government/military" bands, although this is not reflected in the Radio Regulations and is becoming less clear-cut as the Radio Regulations and is becoming less clear-cut as "commercial" operators move to utilize "government" bands."commercial" operators move to utilize "government" bands.

Earth’s atmosphereEarth’s atmosphere

Source: All about GPS [www.kowoma.de]Source: All about GPS [www.kowoma.de]

Q&AQ&A

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