Satellite Communication

1
Satellite Communication

• Introductory Lecture
• http//web.uettaxila.edu.pk/CMS/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 speech and video coding, satellite
  networking, internet over satellite and satellite
  personal communications.
• Highlight trends and future directions of
  satellite communication

4
Course Pre-requisites

• Principles of digital communications
• Telecom systems design

5
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 and G/T ratio, Eb/No.
  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, oscillator phase noise.

6
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.

7
Section 3 Multiple Access Issues

• Spread Spectrum Techniques Military and
  commercial use of spread-spectrum.
  Direct-Sequence PN, 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.
  DAMA and Bandwidth-on-Demand (BoD).
• TDMA Networks Time Slots, Preambles, Suitability
  for DAMA and BoD.

8
Section 4 SATCOM Networks and Services

• Satellite Communication Systems Networks
• Characteristics of IP and TCP/UDP over satellite
  Unicast and Multicast. Need for Performance
• Enhancing Proxy (PEP) techniques.
• VSAT Networks and their system characteristics.
• DVB standards and MF-TDMA
• The Future of SATCOM
• SATCOMs role in the emerging 4G Information and
  Communications (ICT) infrastructure.

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 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)

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, ATT Telstar 1
• First Canadian satellite Alouette 1
• On 7th June 1962 at 753p 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

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 

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
• 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

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
• Pakistans 2nd Satellite, BADR-B was launched on
  10 Dec 2001 at 915a 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 

17
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 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 -gt Executive Organ
• Executive Council -gt EUTELSAT Board of
  Signatories
• Secretary General -gt Director General
• Current DG is Giuliano Berretta
• 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 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.

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
• TTC - 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

• 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.

• Source Cryptome Cryptome.org

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
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
35
Types of Satellite Orbits

• Based on the inclination, i, over the equatorial
  plane
• Equatorial Orbits above Earths equator (i0)
• Polar Orbits pass over both poles (i90)
• Other orbits called inclined orbits (0ltilt90)
• Based on Eccentricity
• Circular with centre at the earths centre
• Elliptical with one foci at earths 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

• 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.

• Source Federation of American Scientists
  www.fas.org

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 lt 1400 km
  altitude
• Satellite travels across sky from horizon to
  horizon in 5 - 15 minutes gt 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

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
Earths atmosphere

• Source All about GPS www.kowoma.de

51
Atmospheric Losses

• Different types of atmospheric losses can disturb
  radio wave transmission in satellite systems
• Atmospheric absorption
• Atmospheric attenuation
• Traveling ionospheric disturbances

52
Atmospheric Absorption

• Energy absorption by atmospheric gases, which
  varies with the frequency of the radio waves.
• Two absorption peaks are observed (for 90º
  elevation angle)
• 22.3 GHz from resonance absorption in water
  vapour (H2O)
• 60 GHz from resonance absorption in oxygen (O2)
• For other elevation angles
• AA AA90 cosec ?

Source Satellite Communications, Dennis Roddy,
McGraw-Hill
53
Atmospheric Attenuation

• Rain is the main cause of atmospheric attenuation
  (hail, ice and snow have little effect on
  attenuation because of their low water content).
• Total attenuation from rain can be determined by
• A ?L dB
• where ? dB/km is called the specific
  attenuation, and can be calculated from specific
  attenuation coefficients in tabular form that can
  be found in a number of publications
• where L km is the effective path length of the
  signal through the rain note that this differs
  from the geometric path length due to
  fluctuations in the rain density.

54
Traveling Ionospheric Disturbances

• Traveling ionospheric disturbances are clouds of
  electrons in the ionosphere that provoke radio
  signal fluctuations which can only be determined
  on a statistical basis.
• The disturbances of major concern are
• Scintillation
• Polarisation rotation.
• Scintillations are variations in the amplitude,
  phase, polarisation, or angle of arrival of radio
  waves, caused by irregularities in the ionosphere
  which change over time.
• The main effect of scintillations is fading of
  the signal.

55
What is Polarisation?

• Polarisation is the property of electromagnetic
  waves that describes the direction of the
  transverse electric field.
• Since electromagnetic waves consist of an
  electric and a magnetic field vibrating at right
  angles to each other.
• it is necessary to adopt a convention to
  determine the polarisation of the signal.
• Conventionally, the magnetic field is ignored and
  the plane of the electric field is used.

56
Types of Polarisation

• Linear Polarisation (horizontal or vertical)
• the two orthogonal components of the electric
  field are in phase
• The direction of the line in the plane depends on
  the relative amplitudes of the two components.
• Circular Polarisation
• The two components are exactly 90º out of phase
  and have exactly the same amplitude.
• Elliptical Polarisation
• All other cases.

Linear Polarisation
Circular Polarisation
Elliptical Polarisation
57
Satellite Communications

• Alternating vertical and horizontal polarisation
  is widely used on satellite communications
• This reduces interference between programs on the
  same frequency band transmitted from adjacent
  satellites (One uses vertical, the next
  horizontal, and so on)
• Allows for reduced angular separation between the
  satellites.

Information Resources for Telecommunication
Professionals www.mlesat.com
58
Related Information

• http//web.uettaxila.edu.pk/uet/narc/flvplay.htm

59
QA

• ????

60
Assignment 1

• Read the paper of Arthur C. Clark and summarize
  his suggestions to support Satellite for
  Communication purposes
• Visit http//web.uettaxila.edu.pk/cms/teSCms and
  visit JTrack-3D Link under Important Links
  section to complete the assignment
• You need to find out the satellite name of
  PakSat-1 in JTrack-3D and send a snapshot of
  JTrack-3D with PakSat-1 in it