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Slide 3:

Pioneers in Satellite Communication Konstantin Tsiolkovsky (1857 - 1935) Russian visionary of space flight First described the multi-stage rocket as means of achieving orbit. Link: The life of Konstantin Eduardovitch Tsiolkovsky Hermann Noordung (1892 - 1929) Postulated the geostationary orbit. Link: The Problem of Space Travel: The Rocket Motor 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)

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Satellite is a microwave repeater in the space. There are about 750 satellite in the space, most of them are used for communication. They are: Wide area coverage of the earth’s surface. Transmission delay is about 0.3 sec. Transmission cost is independent of distance.

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Satellite Signals Used to transmit signals and data over long distances Weather forecasting Television broadcasting Internet communication Global Positioning Systems

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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 Communication

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Basic Principles Satellite Uplink Earth Station Downlink Tx Source Information Rx Output Information Earth Station

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How do Satellites Work Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means. The two stations can use a satellite as a relay station for their communication One Earth Station sends a transmission to the satellite. This is called a Uplink . The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink .

Slide 9:

Ground Segment ? Collection of facilities, Users and Applications Earth Station = Satellite Communication Station (Fixed or Mobile)

Satellite for internet:

Satellite for internet Internet service provider

satellite systems for cellular networks:

satellite systems for cellular networks base station or gateway Inter Satellite Link (ISL) Mobile User Link (MUL) Gateway Link (GWL) footprint small cells (spot beams) User data PSTN ISDN GSM GWL MUL PSTN: Public Switched Telephone Network

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“Typical” Fixed Satellite Network Branch Offices Corporate Data Center/HQ Network HUB Corporate Offices Gas Stations Apartment Buildings Residential Internet Applications Credit Card Validation ATM/Pay at the Pump Inventory Control Store Monitoring Electronic Pricing Training Videos In-Store Audio Broadband Internet Access Distance Learning

Break throughs of History of satellite communication :

Break throughs of History of satellite communication 1945 Arthur C. Clarke publishes an essay about “Extra Terrestrial Relays” 1957 first satellite SPUTNIK 1960 first reflecting communication satellite ECHO 1963 first geostationary satellite SYNCOM 1965 first commercial geostationary satellite “Early Bird” (INTELSAT I): 240 duplex telephone channels or 1 TV channel, 1.5 years lifetime 1976 three MARISAT satellites for maritime communication 1982 first mobile satellite telephone system INMARSAT-A 1988 first satellite system for mobile phones and data communication INMARSAT-C 1993 first digital satellite telephone system 1998 global satellite systems for small mobile phones

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Satellite History Calendar 1945 Arthur C. Clarke publishes an essay about „Extra Terrestrial Relays 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 7 th 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 9 th 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

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Satellite History Calendar 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

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Satellite History Calendar 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 Ku-band 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.

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Satellite History Calendar 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 2 nd 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 VUSat OSCAR-52 (HAMSAT) Launched 2006 CubeSat-OSCAR 56 (Cute-1.7) Launched K7RR-Sat launched by California Politechnic University 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.

Slide 18:

Sputnik - I First satellite

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Explorer-1 First American satellite:

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ECHO I balloon” satellite - passive

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SYNCOM 2 Picture from NASA first Geosynchronous satellite

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Telstar I Allowed live transmission across the Atlantic

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Intelsat I first commercial geostationary satellite

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Intelsat 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 Permanent structure formed in 1973 Commercial "spin-off", New Skies Satellites in 1998 Full "privatization" by April 2001 INTELSAT has 143 members

Iridium project to deploy many satellites for world coverage:

Iridium project to deploy many satellites for world coverage

Slide 26:

Communication Satellite 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.

Slide 27:

When to use Terrestrial comm 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

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When to use Satellites 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

Applications :

Traditionally weather satellites radio and TV broadcast satellites military satellites satellites for navigation and localization (e.g., GPS) Telecommunication global telephone connections backbone for global networks connections for communication in remote places or underdeveloped areas global mobile communication  satellite systems to extend cellular phone systems (e.g., GSM) replaced by fiber optics Applications

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Satellite Services & Applications Infrastructure / Support Services Remote Sensing Pipeline Monitoring Infrastructure Planning Forest Fire Prevention Urban Planning Flood and Storm watches Air Pollution Management Geo-spatial Services Direct-To-Consumer Broadband IP DTH/DBS Television Digital Audio Radio Interactive Entertainment & Games Video & Data to handhelds Voice/Video/Data Communications Rural Telephony News Gathering/Distribution Internet Trunking Corporate VSAT Networks Tele-Medicine Distance-Learning Mobile Telephony Videoconferencing Business Television Broadcast and Cable Relay VOIP & Multi-media over IP Launch Vehicles Ground Equipment Insurance Manufacturing

Slide 31:

Critical to the Future of Aviation Currently providing secure and reliable voice and data communications In-flight data and voice communications for Crew, Air Marshals and passengers Establishing specialized secure communications for airplanes, airports, seaports, and border control. Enable Search and Rescue Next Generation Satellite Services Global Air Traffic Management Black Box Alternatives Advanced passenger and safety services

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Critical To Rural areas

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A military system that is now central to the lives of millions of civil and commercial users Public safety dispatch – improves response time Search and Rescue – locates emergency calls Air Traffic Control – guides planes in all weather Telecommunications – primary timing source, E-911 enabler Transportation – tracks trains, trucks, vital shipments Underpins US Warfighting Precision Munitions Cruise Missiles Unmanned Aerial Vehicles Navigation – GPS

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Commercial Remote Sensing QuickBird .61 m color image Provides scientific, industrial, civil, military and individual users with high resolution images for: Defense & intelligence Homeland security & asset protection Insurance & risk management Transportation & infrastructure planning Natural resource assessment Agriculture Disaster relief Insurance and risk management Oil & gas exploration Mapping

Slide 35:

Critical to Weather Forecasting Search and Rescue Environmental satellite system is composed of: Geostationary Operational Environmental Satellites (GOES): short-range warning and “narrowcasting” Polar Orbiting Environmental Satellites (POES): longer term forecasting Both are required for providing complete global weather monitoring The satellites carry search and rescue instruments, and have helped save the lives of about 10,000 people to date.

Slide 36:

Critical To National Security 80% of satellite communications used during Operation Iraqi Freedom were provided by the private sector To meet its near-to-midterm war-fighting requirements, DOD must continue to use commercial SATCOM

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Critical to Flow of Information Newsgathering – First choice for live coverage, providing high-bandwidth video links from remote locations to capture “breaking news” Program Delivery – National broadcasts from four major television networks and more than 180 cable channels are relayed to over 10,000 local cable systems via satellite

Slide 38:

Advantages of Satellite Communication 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) 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 Higher Bandwidths are available for use. Satellite to Satellite communication is very precise

Slide 39:

Disadvantages of Satellites Launching satellites into orbit is costly. Satellite bandwidth is gradually becoming used up. There is a larger propagation delay and Interference in satellite communication than in terrestrial communication. Congestion of frequencies and orbits

Slide 40:

Satellite up links and down links can operate in different frequency bands: The up-link is a highly directional, point to point link The down-link can have a footprint providing coverage for a substantial area "spot beam“. Band Up-Link (Mhz) Down-link (Mhz) ISSUES C 3,700-4,200 5,925-6,425 Interference with ground links. Ku 11.7-12.2 14.0-14.5 Attenuation due to rain Ka 17.7-21.2 27.5-31.0 High Equipment cost

Slide 41:

Radio Frequency Spectrum Commonly Used Bands

Satellite Frequencies:

Satellite Frequencies There are specific frequency ranges used by commercial satellites. L-band (Mobile Satellite Services) 1.0 – 2.0 GHz S-band (MSS, DARS – XM, Sirius) 1.55 – 3.9 GHz C-band (FSS, VSAT) 3.7 – 6.2 GHz X-Band (Military/Satellite Imagery) 8.0 – 12.0 GHz Ku-band (FSS, DBS, VSAT) 11.7–14.5 GHz Ka-band (FSS “broadband” and inter-satellite links) 17.7 - 21.2GHz and 27.5 – 31 GHz

Slide 43:

Signals Signals: Carried by wires as voltage or current Transmitted through space as electromagnetic waves. Analog: Voltage or Current proportional to signal; e.g., Telephone. Digital: Generated by computers. Ex. Binary = 1 or 0 corresponding to +1V or –1V.

Slide 44:

Separating Signals Up and Down: FDD: Frequency Division Duplexing. f1 = Uplink f2 = Downlink TDD: Time Division Duplexing. t1=Up, t2=Down, t3=Up, t4=Down,…. Polarization V & H linear polarization RH & LH circular polarizations

Slide 45:

F 1 (Gravitational Force) v (velocity) Why do satellites stay moving and in orbit ? F 2 (Inertial-Centrifugal Force)

Slide 46:

MOLNIYA VIEW OF THE EARTH ( Apogee remains over the northern hemisphere)

Orbital Options:

Orbital Options A Geosynchronous satellite (GEO) completes one revolution around the world every 23 hrs and 56 minutes in order to maintain continuous positioning above the earth’s sub-satellite point on the equator. A medium earth orbit satellite (MEO) requires a constellation of 10 to 18 satellites in order to maintain constant coverage of the earth. A low earth orbit satellite (LEO) offers reduced signal loss since these satellites are 20 to 40 times closer to the earth in their orbits thus allowing for smaller user terminals/antennas

Slide 49:

Main orbit types : LEO 500 -1000 km GEO 36,000 km MEO 5,000 – 15,000 km

Slide 50:

Types of Satellite based Networks Based on the Satellite Altitude GEO – Geostationary Orbits 36000 Km = 22300 Miles, equatorial, High latency MEO – Medium Earth Orbits High bandwidth, High power, High latency LEO – Low Earth Orbits Low power, Low latency, More Satellites, Small Footprint VSAT Very Small Aperture Satellites Private WANs

Slide 51:

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

Geostationary satellites:

Geostationary satellites Orbit 35,786 km distance to earth surface, orbit in equatorial plane (inclination 0°)  complete rotation exactly one day, satellite is synchronous to earth rotation fix antenna positions, no adjusting necessary satellites typically have a large footprint (up to 34% of earth surface!), therefore difficult to reuse frequencies bad elevations in areas with latitude above 60° due to fixed position above the equator high transmit power needed high latency due to long distance (ca. 275 ms)  not useful for global coverage for small mobile phones and data transmission, typically used for radio and TV transmission

Slide 53:

Geostationary Orbit Today

Slide 54:

Geostationary Orbit (GEO) Characteristics of Geostationary (GEO) Orbit Systems User terminals do not have to track the satellite Only a few satellites can provide global coverage Maximum life-time (15 years or more) Above Van Allen Belt Radiation Often the lowest cost system and simplest in terms of tracking and high speed switching Challenges of Geostationary (GEO) Orbit Transmission latency or delay of 250 millisecond to complete up/down link Satellite antennas must be of larger aperture size to concentrate power and to create narrower beams for frequency reuse Poor look angle elevations at higher latitudes

LEO systems:

LEO systems Orbit 500 - 1500 km above earth surface visibility of a satellite 10 - 40 minutes global radio coverage possible latency comparable with terrestrial long distance connections. 5 - 10 ms smaller footprints, better frequency reuse but now handover necessary from one satellite to another many satellites necessary for global coverage more complex systems due to moving satellites Examples: Iridium (start 1998, 66 satellites) Bankruptcy in 2000, deal with US DoD (free use, saving from “deorbiting”) Globalstar (start 1999, 48 satellites) Not many customers (2001: 44000), low stand-by times for mobiles

MEO systems:

MEO systems Orbit ca. 5000 - 12000 km above earth surface comparison with LEO systems: slower moving satellites less satellites needed simpler system design for many connections no hand-over needed higher latency, ca. 70 - 80 ms higher sending power needed special antennas for small footprints needed Example: ICO (Intermediate Circular Orbit, Inmarsat) start ca. 2000 Bankruptcy, planned joint ventures with Teledesic, Ellipso – cancelled again, start planned for 2003

Slide 57:

At the Geostationary orbit the satellite covers 42.2% of the earth’s surface. Theoretically 3 geostaionary satellites provides 100% earth coverage

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Parameters determining satellite position

Slide 59:

Spectrum Regulation International Telecommunication Union (ITU): Members from practically all countries around the world. Allocates frequency bands for different purposes and distribute them around the planet. Creates rules to limit RF Interference (RFI) between countries that reuse same RF bands. Mediates disputes and creates rules to deal with harmful interference when it occurs. Meets bi-annually with its members, to review rules and allocations: World Radio Communication Conference (WRC). There are also the Regional Radio Communication Conferences (RCC), which happen less often.

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Satellite System Elements

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Satellite Subsystems Communications Antennas Transponders Common Subsystem (Bus Subsystem) Telemetry/Command (TT&C) Satellite Control (antenna pointing,attitude) Propulsion Electrical Power Structure Thermal Control

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Space 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

Slide 63:

Components Bus Power Subsystem Telemetry and Command Subsystem Attitude and Control Subsystem Propulsion Subsystem Payload Communications Subsystem Transponders

Slide 64:

Transponders The transponder is the “brains” of the satellite - provides the connection between the satellite’s receive and transmit antennas. Satellites can have 12 to 96 transponders plus spares, depending on the size of the satellite. A transponder bandwidth can frequently be 36 MHz, 54 MHz, or 72 MHz or it can be even wider. A transponders function is to Receive the signal, ( Signal is one trillion times weaker then when transmitted ) Filter out noise, Shift the frequency to a down link frequency (to avoid interference w/uplink) Amplify for retransmission to ground

Slide 65:

Types of Satellite Stabilization Spin Stabilization Satellite is spun about the axis on which the moment of inertia is maximum (ex., HS 376, most purchased commercial communications satellite; first satellite placed in orbit by the Space Shuttle.) Three-Axis Stabilization Bias momentum type (ex., INTELSAT V) Zero momentum type (ex., Yuri)

Slide 66:

Power Modern satellites use a variety of power means Solar panels are now quite efficient, so solar power is used to generate electricity Batteries are needed as sometimes the satellites are behind the earth - this happens about half the time for a LEO satellite Nuclear power has been used - but not recommended

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Harsh Environment Satellite components need to be specially “hardened” Circuits which work on the ground will fail very rapidly in space Temperature is also a problem - so satellites use electric heaters to keep circuits and other vital parts warmed up - they also need to control the temperature carefully

Slide 68:

Alignment There are a number of components which need alignment Solar panels Antennae These have to point at different parts of the sky at different times, so the problem is not trivial

Slide 69:

Antennae alignment A parabolic dish can be used which is pointing in the correct general direction Different feeder “horns” can be used to direct outgoing beams more precisely Similarly for incoming beams A modern satellite should be capable of at least 50 differently directed beams

Slide 70:

Separating Signals (so that many transmitters can use the same transponder simultaneously) Between Users or “Channels” (Multiple Access): FDMA: Frequency Division Multiple Access; assigns each transmitter its own carrier frequency f1 = User 1; f2 = User 2; f3 = User 3, … TDMA: Time Division Multiple Access; each transmitter is given its own time slot t1=User_1, t2=User_2, t3=User_3, t4 = User_1, ... CDMA: Code Division Multiple Access; each transmitter transmits simultaneously and at the same frequency and each transmission is modulated by its own pseudo randomly coded bit stream Code 1 = User 1; Code 2 = User 2; Code 3 = User 3

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