{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

notes-1. Satellite Communication - 1

notes-1. Satellite Communication - 1 - Satellite...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Satellite Communication Satellite Introductory Lecture http://web.uettaxila.edu.pk/CMS/AUT2011/teSCms Overview 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. Course Objectives Course 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 in­depth 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, Hub­Spoke, Point­to­Point, 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. Down­link requirements. Design of satellite links to achieve a specified performance. • Earth Station Antenna types: Pointing/Tracking. Small antennas at Ku band. FCC­Intelsat­ITU 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: M­ary 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 spread­spectrum. Direct­Sequence, 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 Bandwidth­on­Demand (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 MultiFreq­TDMA 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 Book Text Title: The Satellite Communication Applications Handbook Author: Bruce R. Elbert ISBN: 1580534902 EAN: 9781580534901 Publisher: Artech House Publishers Reference Books Reference Title: Satellite Communications Author: Dennis Roddy ISBN: 0071371761 EAN: 9780071371766 Publisher: McGraw­Hill Professional Reference Books Reference Title: Satellite Communication Engineering Author: Michael O. Kolawole ISBN: 082470777X EAN: 9780071371766 Publisher: Marcel Dekker, Inc. Pioneers in Satellite Communication Communication 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 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 Calendar Satellite 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 real­time active, AT&T: Telstar 1 • First Canadian satellite: Alouette 1 • On 7th June 1962 at 7:53p the two­stage rocket; Rehbar­I 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 Rehbar­I, 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. Rehbar­II followed a successful launch on 9 th June 1962 • 1963 Real­time 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 Satellite 1965 Intelsat 1 becomes first commercial comsat: Early Bird • First real­time 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 • ITU­WARC 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 • ITU­WARC for Space Telecommunications in the Satellite Service • 1979 Creation of Inmarsat (International Marine Satellite) • Satellite History Calendar Satellite 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 S­PCN projects proposed ­ CDMA designs more • popular EUTELSAT II • On 16 July 1990, Pakistan launched its first experimental satellite, BADR­I from China • 1992 OLYMPUS finally launched ­ large European development satellite with Ka­band, 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 Satellite 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 • ITU­WRC'97 • 1999 AceS launch first of the L­band MSS Super­GSOs ­ built by Lockheed Martin • Iridium Bankruptcy ­ the first major failure? • 2000 Globalstar begins service • Thuraya launch L­band MSS Super­GSO • 2001 XM Satellite Radio begins service • Pakistan’s 2nd Satellite, BADR­B was launched on 10 Dec 2001 at 9:15a from Baikonour Cosmodrome, • Kazakistan 2002 Sirius Satellite Radio begins service • Paksat­1, was deployed at 38 degrees E orbital slot in December 2002 • 2004 Teledesic network planned to start operation • 2005 Intelsat and Panamsat Merge • • VUSat OSCAR­52 (HAMSAT) Launched • • CubeSat­OSCAR 56 (Cute­1.7) Launched K7RR­Sat launched by California Politechnic University 2006 2007 Prism was launched by University of Tokyo • 2008 COMPASS­1; a project of Aachen University was launched from Satish Dawan Space Center, India. It failed • to achieve orbit. Intelsat 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 "spin­off", New Skies Satellites in 1998 Full "privatization" by April 2001 INTELSAT has 143 members and signatories listed here. Intelsat Structure Intelsat Eutelsat 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 pan­European coverage, universal service, non­discrimination and fair competition are observed by the company Eutelsat Structure Eutelsat Communication Satellites Communication 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 Motivation Satellite Missions Source: Union of Concerned Scientists [www.ucsusa.org] Source: Union of Concerned Scientists [www.ucsusa.org] Satellite Microwave Transmission Satellite 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 Satellite Space Segment Space 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 Segment Ground Collection of facilities, Users and Applications Earth Station = Satellite Communication Station (Fixed or Mobile) Satellite Uplink and Downlink Satellite 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. Satellite Uplink and Downlink Satellite Satellite Communication Source: Cryptome [Cryptome.org] 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 Satellite 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 Direct One way Service (Broadcasting) Two way Service (Communication) Satellite Signals Satellite Used to transmit signals and data over long distances • • • • Weather forecasting Television broadcasting Internet communication Global Positioning Systems Satellite Transmission Bands Satellite 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 Types 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 Types of Satellite based Networks Types 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 Satellite Orbits Source: Federation of American Scientists [www.fas.org] 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 Satellite GEO - Geostationary Orbit GEO 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) NGSO - Non Geostationary Orbits NGSO Orbit should avoid Van Allen radiation belts: • Region of charged particles that can cause damage to satellite • Occur at ~2000­4000 km and ~13000­25000 km LEO - Low Earth Orbits LEO 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 HEO 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] Source: Union of Concerned Scientists [www.ucsusa.org] Why Satellites remain in Orbits? Why Advantages of Satellite Communication 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 "fill­in") Terrestrial network "by­pass" Provision of service to remote or underdeveloped areas User has control over own network 1­for­N multipoint standby possibilities Disadvantages of Satellite Communication 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 When to use Satellites When • • • • • • • 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 When 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 fill­in as terrestrial networks are implemented, also provide similar services in rural areas and underdeveloped countries Frequency Bands Allocated to the FSS 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 clear­cut as "commercial" operators move to utilize "government" bands. Earth’s atmosphere Earth’s Source: All about GPS [www.kowoma.de] Q&A Q&A ???? ...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online