Satellite Communication SystemD.C. Agarwal

Evolution and Growth of Communication Satellite Synchronous satellite idea was conceived by

Arthur C. Clarke in 1945 He point out:

satellite in a circular equatorial orbit with a radius of about 42,242 km would have an angular velocity matching that of the earth

Three satellites spaced 120 degree apart could cover the whole atmosphere

Electrical power for satellite can be obtained from sun radiation by means of solar cells

History 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 9 th 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

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

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, 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.

International Regulation and Frequency Coordination Specialized agency of UN Develop a series of radio regulations for

frequency allocations Four permanent organs

General Secretariat International frequency registration board (IFRB) International radio consultative committee (CCITT) International telegraph and telephone consultative

committee (CCITT)

General Secretariat

Located in GENEVA Responsible for the executive

management and technical cooperation

International frequency registration board (IFRB) Responsible for recording frequencies and

orbital positions For advising member countries on

operation of the maximum practical number of radio channels in portions of the spectrum where harmful interference my occur

International radio consultative committee (CCITT)

Responsible for studying technical and operational questions relating to radio communication,Reports, recommendations, resolutions and

decisions published

International telegraph and telephone consultative committee (CCITT)

Responsible for studying technical, operational and tariff questions relating to telegraphy and telephony and for adopting reports and recommendations

World Administrative Radio Conference (WARC) Held in 1979 Allocation of frequency bands for satellite communications Describes various satellite services under 17 categories

1. Aeronautical Mobile Satellite2. Aeronautical Radio navigation Satellite3. Amateur Satellite4. Broadcasting Satellite5. Earth-exploration Satellite6. Fixed Satellite7. Inter-satellite8. Land Mobile Satellite9. Maritime Mobile Satellite10. Maritime Radio navigation Satellite11. Meteorological Satellite12. Mobile Satellite13. Radio determination 14. Radio navigation Satellite15. Space Operations16. Space Research17. Standard Frequency and time signaling Satellite

WARC also Divided globe into three geographic regions for the purpose of frequency allocations

Region 1 Europe, Africa, USSR

and Mongolia

Region 2 North and South

America and Greenland

Region 3 Asia, Australia and

southwest pacific

Satellite Frequency Allocations and Band Spectrum

Six frequency bands allocated for the use satellite communications

Band Downward bands MHz

Uplink Bands MHz

Uhf – Military 250 – 270 (approx)

292 – 312 (Approx)

C Band – Commercial

3700 – 4200 5925 – 8400

X Band – Military

7250 – 7750 7900 – 8400

Ku Band – Commercial

11700 – 12200 14000 – 14500

Ka Band – Commercial

17,700 – 21200 27500 – 30,000

Ka Band – Military

20200 – 21200 43500 - 45500

Characteristics of a satellite system

Satellite in space links earth stations User is connected to earth station through terrestrial

network (telephone switch or a dedicated link to the earth)

The user generates baseband signal that is processed and transmitted to the satellite (received rf carriers) at the earth station

Uplink (signal transmitted from earth to satellite) and downlink (signal received from satellite to earth station)

Uplink and down link frequency spectrum is different in order to avoid interference

Advent of Digital Satellite Communication

Ease and efficiency of multiplexing multiple signals or handling digital messages in packets for convenient switching

The relative insensitivity of digital circuits to retransmission noise, commonly a problem with analog system

Potential for extremely low error rates and high fidelity through error detection and correction

Communication privacy Flexibility of digital hardware implementation which

permits the use of microprocessors and miniprocessors, digital switching and the use of large scale ICs.

Modulation technique

Analog communication system uses FDMM-FM-FDMA has been widely used and provided good quality satellite links But no of earth station is limited

Digital satellite system uses QPSK-TDMA, which accommodate large no. of earth stations with small loss in

transponder capacity. Quickly respond to traffic variations

Recent technique is CDMA Allowed micro earth station (0.5m antenna) Extremely low cost Provides good quality service

ISDN Further enhance the importance of digital communication networking

with satellite

Active and Passive satellites Comparison of the comm capability of active and passive satellite is

the amount of power radiated toward the receiving ground station by the satellie.

Passive satellite The ground transmitting system beams power at the reflector. Receiving ground system receives a fraction of power that has been

intercepted by the reflector and reradiated Active satellite

Receives a fraction of the energy beamed towards it by the ground transmitting system and the received power is amplified by active electronic mean.

Comm capability is much greater in active systems with directional antennas than passive satellite as the altitude is increased

Passive systems are advantages for military systems Modern comm satellites are active systems

Long life electronic equipment are available and these have enhanced the capability of active satellite system

Advantages of Satellite Communication Satellite relays are inherently wide area broadcast

Point to multipoint Where terrestrial links are point to point

Satellite circuits can be installed rapidly Once satellite is in position, earth stations can be installed and

communication my be established in days or even hours Station my be removed relatively quickly from one location and

reinstalled elsewhere Mobile communication

Unique degree of flexibility in interconnecting mobile vehicles Terrestrial networks interconnect mobiles vehicles by cellular radios.

Economical advantages Satellite costs are independent of distance, where

terrestrial network costs are proportional to distance Compared to fiber optic cable,

Quality of transmitted signal and locations of stations sending and receiving information are independent of distance

As long as two stations are within the geographic coverage area of the satellite antenna pattern, the two stations maintain the same quality of information transfer whether they are different KMs apart.

Good way of transmitting wide bandwidth signals across the ocean, as there will be limited capacities of undersea copper or optical cables