CT-474:
Satellite Communications
Yash Vasavada
Autumn 2016
DA-IICT
Course Details
▪ What you will learn:
– Engineering design of wireless communication through satellites
▪ Textbooks:
– Main Text:
▪ Satellite Communications Systems: Systems, Techniques and Technology by Gerard Maral and Michel
Bousquet, Fifth Edition
– Supporting Texts:
▪ Satellite Communications by Timothy Pratt, Charles Bostian, and Jeremy Allnutt
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
2
Assignments and Tests
▪ Reading Assignments:
– In each class, you will be given a reading assignment. You will benefit the most if you come to the next class
after completing this reading assignment
▪ Homework:
– You will be asked to solve theoretical problems. There will typically be one homework assignment per
week.
▪ Projects:
– There will be several Matlab-based projects. Projects may require concentrated, sometimes even intense,
effort.
▪ Exams:
– There will be two mid-terms and one final exam
▪ You can consult me out of class. My office hours for CT-474 will be: Monday, Thursday: 2 to 3 pm at
FB-1 1231
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
3
Grading Policy
▪ You will be graded on the combination of the effort you exhibit during the course of the semester in
doing the homework and projects. Exams are intended to ensure that you’ve understood the key
points well and they will carry equal weight as semester-long assignments.
– Do a good job throughout the semester and you are likely to earn a good grade
▪ Grading Percentages:
– Homework: 10%.
– Projects: 30%.
– Exams: 60% (Midterm-I: 20%. Midterm-II: 20%. Final: 20%).
▪ We will experiment with self-grading of homework and projects. Self graded homework should be
uploaded to Moodle course website.
– Exceptions to the due-dates will be given only in extenuating circumstances.
▪ Honor Policy: you are expected to take an oath of honesty (no cheating, copying, plagiarism).
A quote: process of teaching is futile. No one can educate those who are not interested in learning. Rest will anyhow educate themselves.
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
4
My Background
▪ I am interested in studying applications of machine learning to communications
▪ I’ve worked in the industry in satellite/wireless communications
▪ Types of problems I am interested in:
– Development of algorithms that understand the source of the communication better
▪ Such algorithms can significantly reduce the data required for transmission over the communication channel
– Development of algorithms that can better recover the transmitted message given the noisy replica at the
receiver
– Development of efficient and smart algorithms in general
▪ Interpolation, noise mitigation, prediction, data compression, classification, error recovery, etc.
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
5
Why to Learn about
Satellite Communications
▪ Satellite Communications: a great technology, and the perfect time to get on-board
– Seventy years ago, the technology was non-existent, its birth occurred in late 1950’s, and the technology was
in its infancy throughout 1960’s. Technology today has progressed to an extent when satellites have become
affordable, and….
– …with the advent of Internet, the demand for broadband communications over long distances has grown
significantly. In addition, the applications of SATCOM such as remote sensing, positioning/navigation, weather
monitoring, etc. are also growing leaps and bounds
▪ Major big companies are either already heavily invested or are getting invested in this field
– Existing stalwarts: Boeing, Hughes, Echostar, Airbus, Thales, THURAYA, Space Systems Loral, Inmarsat,
Qualcomm, DirecTV, Dish Network, THURAYA, Viasat, Globalstar, Iridium, iDirect, Gilat, etc.
– Governments of nearly all the major countries are involved in this field: ISRO, MEXSAT, Eutelsat, GPS, etc.
– New entrants: OneWeb, LEOSAT, Tesla, Google, Microsoft, Facebook, Virgin Group, Softbank, NTT Docomo
▪ And the above list names only a few of the players in this field
▪ Why this surge in interest: potential of worldwide voice/data connectivity by laying “fibers in the sky”
A technology whose “time has come”. Prospect of a great career!
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
6
History
▪ Sir Isaac Newton in late 1600’s describes how satellites come to occupy their unceasing orbits
– Physics rules out the possibility of infinitely lasting free running pendulum motion – loss of energy dampens
the oscillations.
– In that context, one of the mysteries solved by Newton is: where do the satellites get the energy to move
continually about in their orbits?
▪ Sir Isaac Asimov in 1945 suggests use of a satellite in an equatorial orbit at a height of ~36000 km
above the earth
– Geostationary orbit in which the satellite orbit rotation rate is same as the Earth’s rotation rate about its
axis (≈ 360𝑜 /𝑑𝑎𝑦), and so the satellite appears fixed in the sky
▪ Satellite era began in earnest in 1957 with the launch of Sputnik
satellites by Soviet Union
▪ First communication satellite “Signal Communication by Orbital
Relay (SCORE)” was launched by USA in late December of 1958
with a broadcast Christmas message from President
Eisenhower - "Peace on Earth, Good will toward men“. Lifetime:
12 days!
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
7
History of Satellite
Communications: Early Years
Year
Country
Name
Description
1960
USA
Echo-1
A passive reflector satellite that reflected back the received radiation back to the Earth.
Did not succeed as a communication satellite.
1962
USA
Telstar
A relay of T.V. signals, although used for testing of telephone, telegraph, etc. as well
1964
-
Intelsat
A consortium, that has > 130 governments and international organizations, was formed.
1965
USA
Early Bird
A project by USA company, Comsat, to provide the first commercial communication
service via satellite
19651969
Launches of multiple GEO satellites to provide coverage over Atlantic Ocean (1965), Pacific
Ocean (1967) and Indian Ocean (1969)
19721975
Domestic communication satellites by Canada (Anik), USA (Westar) and Phillipines
(Palapa)
1976
USA
1979
Yash Vasavada
Marisat
First mobile communication satellites built by Hughes for Comsat. Customer: US Navy
Inmarsat
Major provider of satellite communications to ships and planes. Formed in 1979 as a
consortium of 28 countries.
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
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Progress of Satellite
Communications: Then and Now
▪ Satellite launch technology has improved by two orders of magnitude:
– First INTELSAT-1 satellite launched weighted 68 kg.
– Launch vehicles can carry a load of greater than 13000 kg in 2008
▪ Satellite life span has increased by an order of magnitude:
– Initial satellites had a life span of 1 to 2 years
– Satellites today are built to last 10 to 20 years
▪ Satellite payload technology has improved and the cost (of especially small-sized SATs) has reduced
– Use of higher powered amplifiers on board
– Use of contoured beam antennas whose footprints are adapted to the shapes of continents
– Use of multi spot-beam technology and of frequency reuse technology
▪ Satellite Earth Stations have become cheaper
– Initial earth stations were only a few, since they were expensive (> 30 million USD) and large (> 30 𝑚 antenna
diameter)
– Today millions of cheap earth stations with very small dish size (Very Small Aperture Terminal or VSATs) are
deployed throughout the world
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
9
Progress of Satellite
Communications: Then and Now
▪ Mobile satellite communications has become an affordable, convenient, and reliable technology
– Early SAT phones were expensive and bulky
▪ First generation SAT phones were priced at multiple thousands of dollars and had size/weight resembling a suitcase (early
1990’s) and later a brick (late 1990’s)
▪ SAT phones today are nearly indistinguishable from the cell phones in cost, size and weight
– Early Mobile SAT systems were plagued with technical problems (e.g., loss of call during hand-offs)
▪ Technology has progressed to the extent that hour-long phone calls are possible through a constellation of moving satellites
▪ New technologies and developments are redefining the state of the art
– Signal processing schemes
▪ Payload nonlinearity mitigation that allows the satellite amplifier to operate close to the saturation
▪ Overlay in frequency domain of the satellite inbound and outbound traffic signals
▪ On-board and ground-based beamforming
– Advancement in RF and Antenna design
▪ Use of higher frequency bands (Ku, Ka and above)
▪ Affordable satellite tracking antennas on the ground
▪ SATCOM is a field of intense research and development. New technologies and developments are
continually making the communications via satellites an attractive alternative to land-based means of
communications
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
10
Frequently Used Terms in the
Vocabulary of SATCOM Engineers
▪ Frequency Bands:
– L band (1.6 GHz), S band (~2 to 2.5 GHz), C band (4-8
GHz)
– Ku band (10 to 15 GHz), Ka band (20-40 GHz) C
▪ Multiple Access Schemes:
– FDMA, TDMA, CDMA, LTE, OFDMA, SC-FDMA, SCPC
▪ Forward/Return Links, Up/Down Links
http://blog.idirect.net/ku-v-ka-battle-of-the-bands/
Forward Link: GW to Users via SAT
Return Link: Users to GW via SAT
Uplink: Any link toward SAT
Downlink: Link coming from SAT
▪ Transmitter Concerns:
– Transmit Power
– EIRP (Equivalent Isotropically Radiated Power)
▪ Receiver Concerns:
– System Noise Temperature (T) and Noise Figure
– G/T: Gain of receive antenna over T
▪ System Concerns: Bandwidth, Bit Rate, Target
Es/No or C/No, BER
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
11
Reading Assignment
▪ MB, Chapter 1
Yash Vasavada
DA-IICT. Autumn 2016
CT-474. Lecture 1: 27th July 2016.
12