Satellite Communication

1. Satellite Communication Introductory Lecture http://web.uettaxila.edu.pk/CMS/AUT2011/teSCms

2. Overview • 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.

3. 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.

4. 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 convertersetc.

5. 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.

6. 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.

7. 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.

8. 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.

9. Text Book • Title: The Satellite Communication Applications Handbook • Author: Bruce R. Elbert • ISBN: 1580534902 • EAN: 9781580534901 • Publisher: Artech House Publishers

10. Reference Books • Title: Satellite Communications • Author: Dennis Roddy • ISBN: 0071371761 • EAN: 9780071371766 • Publisher: McGraw-Hill Professional

11. Reference Books • Title: Satellite Communication Engineering • Author: Michael O. Kolawole • ISBN: 082470777X • EAN: 9780071371766 • Publisher: Marcel Dekker, Inc.

12. 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 EduardovitchTsiolkovsky • 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)

13. Satellite History Calendar • 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

14. 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 (International Marine Satellite)

15. 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 • 1990 • IRIDIUM, TRITIUM, ODYSSEY and GLOBALSTAR S-PCN projects proposed - CDMA designs more popular • EUTELSAT II • On 16 July 1990, Pakistan launched its first experimental satellite, BADR-I from China • 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.

16. 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 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 • 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.

17. Intelsat • INTELSAT is the original "International Telecommunications 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 and signatories listed here.

18. Intelsat Structure

19. Eutelsat • 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 • General Secretariat -> Executive Organ • Executive Council -> EUTELSAT Board of Signatories • Secretary General -> Director General • Current DG is Michel de Rosen • 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, non-discrimination and fair competition are observed by the company

20. Eutelsat Structure

21. Communication Satellites • 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.

22. Motivation to use Satellites

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

24. Satellite Microwave Transmission • 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

25. Satellite System Elements

26. 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

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

28. Satellite Uplink and Downlink • Downlink • The link from a satellite down to one or more ground stations or receivers • Uplink • The link from a ground station up to a satellite. • 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.

29. Satellite Uplink and Downlink

30. Satellite Communication 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.

31. Satellite Transmission Links • 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

32. Direct to User Services One way Service (Broadcasting) Two way Service (Communication)

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

34. Satellite Transmission Bands 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

35. Types of Satellite Orbits • 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°) • Based on Eccentricity • Circular with centre at the earth’s centre • Elliptical with one foci at earth’s centre

36. 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

37. Satellite Orbits 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.

38. Satellite Orbits

39. GEO - Geostationary Orbit • 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 • 3 Satellites can cover the earth (120° apart)

40. NGSO - 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

41. LEO - 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 satellitesneeded to cover earth) • Requires complex architecture • Requires tracking at ground

42. HEO - 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)

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

44. Why Satellites remain in Orbits?

45. 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) • 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

46. Disadvantages of Satellite Communication • 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

47. 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

48. When to use Terrestrial • 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

49. Frequency Bands Allocated to the FSS • 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.

50. Earth’s atmosphere Source: All about GPS [www.kowoma.de]