Lecture 1

EE-483 SPRING 2015SATELLITE COMMUNICATIONSLecture 1Introduction to Satellite Communication

Institute of Space Technology

General Course PolicyPunctuality is a must! All class matters will be put up by the class CR only. Quizzes will be unannounced. Assignments will be assigned regularly except for the week before an exam. Assignments should be hand written. Copied assignments will not be accepted and negative marks may be given. Assignments will not be accepted after the final submission date/time.

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Topics to be Covered

Introduction and BackgroundOrbital Aspects and LaunchingSpacecraft SubsystemsLink BudgetsModulationMultiple Access & On-board Processing CodingFrequency & Propagation AspectsEarth Station Technology & VSATsNon-Geosynchronous Orbits (NGSO)GPS and Future Trends

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OverviewArthur C. Clarke first proposed the idea of satellite technology in 1945 in his article in Wireless WorldToday, satellite systems can provide a variety of services including:broadband communications, audio/video distribution networks, maritime navigation, worldwide customer service and support,military command and control etcSatellite systems are playing 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*

Pioneers in Satellite CommunicationKonstantin 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)*

Satellite History Calendar1957 October 4, 1957: - First satellite - the Russian Sputnik 01First living creature in space: Sputnik 021958First American satellite: Explorer 01First telecommunication satellite: This satellite broadcast a taped message: Score1959First meteorology satellite: Explorer 07 1960First successful passive satellite: Echo 1First successful active satellite: Courier 1BFirst NASA satellite: Explorer 08April 12, 1961: - First man in space1962First telephone communication & TV broadcast via satellite: Echo 1First telecommunication satellite, first real-time active, AT&T: Telstar 1First Canadian satellite: Alouette 1On 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 1963Real-time active: Telstar 21964Creation of IntelsatFirst geostationary satellite, second satellite in stationary orbit: Syncom 3First Italian satellite: San Marco 1*

Satellite History Calendar1965Intelsat 1 becomes first commercial comsat: Early BirdFirst real-time active for USSR: Molniya 1A1967First geostationary meteorology payload: ATS 31968First European satellite: ESRO 2BJuly 21, 1969: - First man on the moon 1970First Japanese satellite: OhsumiFirst Chinese satellite: Dong Fang Hong 011971First UK launched satellite: ProsperoITU-WARC for Space Telecommunications INTELSAT IV Launched INTERSPUTNIK - Soviet Union equivalent of INTELSAT formed 1974First direct broadcasting satellite: ATS 61976MARISAT - First civil maritime communications satellite service started 1977EUTELSAT - European regional satellite ITU-WARC for Space Telecommunications in the Satellite Service 1979Creation of Inmarsat*

Satellite History Calendar1980INTELSAT V launched - 3 axis stabilized satellite built by Ford Aerospace 1983ECS (EUTELSAT 1) launched - built by European consortium supervised by ESA 1984UK's UNISAT TV DBS satellite project abandoned First satellite repaired in orbit by the shuttle: SMM1985First Brazilian satellite: Brazilsat A1First Mexican satellite: Morelos 11988First Luxemburg satellite: Astra 1A1989INTELSAT VI - one of the last big "spinners" built by HughesCreation of Panamsat - Begins ServiceOn 16 July 1990, Pakistan launched its first experimental satellite, BADR-I from China 1990IRIDIUM, TRITIUM, ODYSSEY and GLOBALSTAR S-PCN projects proposed - CDMA designs more popular EUTELSAT II 1992OLYMPUS finally launched - large European development satellite with Ka-band, DBTV and Ku-band SS/TDMA payloads - fails within 3 years 1993INMARSAT II - 39 dBW EIRP global beam mobile satellite - built by Hughes/British Aerospace 1994INTELSAT VIII launched - first INTELSAT satellite built to a contractor's design Hughes describe SPACEWAY design DirecTV begins Direct Broadcast to Home1995Panamsat - First private company to provide global satellite services.*

Satellite History Calendar1996INMARSAT III launched - first of the multibeam mobile satellites (built by GE/Marconi) Echostar begins Diresct Broadcast Service1997IRIDIUM launches first test satellites ITU-WRC'97 1999AceS launch first of the L-band MSS Super-GSOs - built by Lockheed Martin Iridium Bankruptcy - the first major failure? 2000Globalstar begins service Thuraya launch L-band MSS Super-GSO2001XM Satellite Radio begins servicePakistans 2nd Satellite, BADR-B was launched on 10 Dec 2001 at 9:15a from Baikonour Cosmodrome, Kazakistan 2002Sirius Satellite Radio begins servicePaksat-1, was deployed at 38 degrees E orbital slot in December 2002, Paksat-1, was deployed at 38 degrees E orbital slot in December 20022004Teledesic network planned to start operation2005Intelsat and Panamsat Merge VUSat OSCAR-52 (HAMSAT) Launched 2006CubeSat-OSCAR 56 (Cute-1.7) LaunchedK7RR-Sat launched by California Politechnic University2007Prism was launched by University of Tokyo 2008COMPASS-1; a project of Aachen University was launched from Satish Dawan Space Center, India. It failed to achieve orbit.*

Evolution of Satellite Communications*

Evolution of Satellite Communications*

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

Basic Principles*

Communication SatelliteA Communication Satellite can be looked upon as a large microwave repeaterIt 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.*

Basic Xtics of Satellites*Satellite in a geostationary Earth orbit (GEO) revolves around Earth in equatorial plane once in 24 hrs, maintaining precise synchronization with the Earths rotationA system of 3 satellites in GEO each separated by 120 deg of longitude can cover almost all globeRange from user to satellite is min 36,000 kmFor a GEO satellite, prop. delay of about one-quarter of a sec for a single hop b/w a pair of users

Basics: How Satellites are used*Service TypesFixed Service Satellites (FSS)Example: Point to Point CommunicationBroadcast Service Satellites (BSS)Example: Satellite Television/RadioAlso called Direct Broadcast Service (DBS).Mobile Service Satellites (MSS)Example: Satellite Phones

Motivation to use Satellites*

Satellite MissionsSource: Union of Concerned Scientists [www.ucsusa.org]*

Satellite System Elements*

Space Segment*Satellite Launching PhaseTransfer Orbit PhaseDeployment Phase Operation PhaseTT&C - Tracking Telemetry and Command StationSSC - Satellite Control Center, a.k.a.:OCC - Operations Control CenterSCF - Satellite Control FacilityRetirement Phase

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Institute of Space Technology

Ground Segment11-Oct-10*Collection of facilities, Users and Applications

Earth Station = Satellite Communication Station (Fixed or Mobile)

Satellite Footprints*In GEO satellite, the power directed towards the Earth covers some geographic area with its max signal strength near the central area of what is called its footprint, with decreasing strengths farther out from the areaIntelsat satellites useGlobal beams covers as much of Earth as can be seen by the satelliteHemispherical beamsZone beamsSpot beamsSmaller the beam-size, greater the signal strength on the Earth, and smaller the receiving antenna can be

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11-Oct-10Institute of Space Technology*

Institute of Space Technology

Satellite OrbitsSource: 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.*

Main Orbits*

Satellite OrbitsOrbits below 36,000 km altitude are termed as non-GEOAdvantage of non-GEO: less radiated power required and prop. delay is reducedTransponder: one complete microwave channel of transmission from a satellite*Source: Union of Concerned Scientists [www.ucsusa.org]

Geostationary Earth Orbit (GEO)*In equatorial planeOrbital Period = 23h 56 min. 4.091s = one sidereal day Satellite appears to be stationary to an observer over a point on the equator.Earth rotates at the same speed as satelliteRadius of orbit, r = 42,164.57 kmNOTE: Radius = orbital height + radius of the EarthAverage radius of Earth = 6,378.14 km

NGSO - Non Geostationary OrbitsOrbit should avoid Van Allen radiation belts:Region of charged particles that can cause damage to satelliteOccur at ~2000-4000 km and ~13000-25000 km*

Low Earth Orbit (LEO)*Much closer to the earth than GEO satellites, ranging from 500 to 1,500 km above the surfaceDont stay in fixed position relative to the surface, and are only visible for 15 to 20 minutes each pass => needs handoffsA network of LEO satellites is necessary for continuous communication (66 satellites needed to cover the EarthEarth stations must track satellites or have omnidirectional antennas

Medium Earth Orbit (MEO)*A MEO satellite is in orbit somewhere between 5,000 km and 15,000 km above the earths surfaceare similar to LEO satellites in functionalityare visible for much longer periods of time than LEO satellites, usually between 2 to 8 hourshave a larger coverage area than LEO satellites

Comparison of Orbit Types*

Other Orbits*Molniya Orbit SatellitesUsed by Russia for decadesMolniya Orbit is an elliptical orbit. The satellite remains in a nearly fixed position relative to earth for eight hoursA series of three Molniya satellites can act like a GEO satelliteUseful in near polar regionsHigh Altitude Platform (HAP)One of the newest ideas in satellite communicationA blimp or plane around 20 km above the earths surface is used as a satelliteHAPs would have very small coverage area, but would have a comparatively strong signalCheaper to put in position, but would require a lot of them in a network

Orbital Velocities and Periods*

Frequency Spectrum concepts:*

Radio Frequencies (RF)*

Space-Earth Frequency Usability*

Microwave Frequencies*

Spectrum Regulation*

Frequency BandsDifferent kinds of satellites use different frequency bands.LBand: 1 to 2 GHz, used by MSSS-Band: 2 to 4 GHz, used by MSS, NASA, deep space researchC-Band: 4 to 8 GHz, used by FSSX-Band: 8 to 12.5 GHz, used by FSS and in terrestrial imaging, ex: military and meteorological satellitesKu-Band: 12.5 to 18 GHz: used by FSS and BSS (DBS)K-Band: 18 to 26.5 GHz: used by FSS and BSSKa-Band: 26.5 to 40 GHz: used by FSS *

Radio Frequency Spectrum Commonly Used Bands*

GEO Satellite Applications*

LEO Satellite Applications*

Advantages of Satellite Communication*Mobile/Wireless Communication, Independent of LocationWide Area Coverage: Country, Continent or GlobeWide Bandwidth Available ThroughoutIndependence From Terrestrial InfrastructureRapid Installations of Ground NetworksLow Cost Per Added SiteUniform Service CharacteristicsTotal Service From a Single Provider

Disadvantages of Satellite Communication*Launching satellites into orbit is costlySatellite bandwidth is gradually becoming used up.There is a larger propagation delay in satellite communication than in terrestrial communication.

When to use SatellitesWhen 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 homeData services - private networks Overload traffic Delaying terrestrial investments 1 for N diversity Special events

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When to use TerrestrialPSTN - 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, 3G/4G LTE Systems etc.) But, satellite can provide fill-in as terrestrial networks are implemented, also provide similar services in rural areas and underdeveloped countries *

Basic Principles:System Block Diagram*

Future of Satellite Communications*

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Direct to User ServicesOne way Service (Broadcasting)Two way Service (Communication)*

Signals (1)*

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Separating Signals (1)*

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*****More detail in next lecture: A sidereal day is the time between consecutive crossings of any particular longitude on the earth with reference toinertial space (or its own axis); I.e., in practice, with reference to any star other than the sun. This corresponds to a 360 degree rotation.

**1 for N Diversity: Where there is negligible likelihood of route failure, there is no need for route diversity protection and the type of protection used is known as "1 for N". In point to point radio systems it is (typically 7 : 1) throughout the world. If a worker section down a route fails, the traffic is switched to a stand-by section. After repair of the worker, traffic is returned to it after a suitable period of time. This period of time is that necessary for a stability test, to check that the fault has been genuinely cleared. Traffic loss due to section failure can typically be reduced by several hundred times by the use of "1-for-N" protection.