satellite communication basics
DESCRIPTION
Basics of SATELLITE COMMUNICATIONTRANSCRIPT
Satellite Communication
04/12/23 RTTC \ SATCOM 1
OVERVIEWOF
SATELLITE COMMUNICATION AND
SATELITE SYSTEM
Satellite Communication
04/12/23 RTTC \ SATCOM 2
Satellite Communication
SATE
LLIT
E
COM
MUNICATIO
N
Satellite Communication
04/12/23 RTTC \ SATCOM 4
Transmission System
can be placed under three broad categories
Radio SystemRadio System Co-axial cable systemCo-axial cable system Optical fibre systemOptical fibre system
Radio SystemRadio SystemDeals with electronic radiation of electromagnetic
energy from one point to another through atmosphere or free space
It is possible only in certain portion of frequency spectrum
Frequency from 9Khz to 400Ghz
Satellite Communication
04/12/23 RTTC \ SATCOM 5
Earth
Layers of Atmosphere
Different layers of the atmosphere play a
role in propagating radio waves
18K
m
70K
m
500K
m
Satellite Communication
04/12/23 RTTC \ SATCOM 6
Ionosphere and troposphere are useful for radio communication in certain
frequency range
Radio communication can be placed under four categories
Skywave or Ionosphere communicationSkywave or Ionosphere communication
LOS M\W Communication LOS M\W Communication
Troposphere scatter communication Troposphere scatter communication
Satellite communicationSatellite communication
Satellite Communication
04/12/23 RTTC \ SATCOM 7
Ionosphere communicationIonosphere communication
It deals with frequency range of 3-30Mhz which are classified as HF band
Alti
tude
(K
m)
Electron density
F1
F2
ED
IONOSPHERE
EarthT R R
Satellite Communication
04/12/23 RTTC \ SATCOM 8
LOS M\W CommunicationLOS M\W Communication
IS CHARCTERSIED BY
► the useful range of frequencies lie between 150Mhz-150Ghz
► it is line of sight communication limited by horizon due to the curvature of the earth
► Signal propagation is affected by free space attenuation
► Frequency / Phase modulation technique are employed
► Spread spectrum or Time sharing techniques are used
Satellite Communication
04/12/23 RTTC \ SATCOM 9
d0 Optical horizon
dr radio horizon
OPTICAL & RADIO HORIZON
A Microwave link
A B
R R
Satellite Communication
04/12/23 RTTC \ SATCOM 10
Troposphere scatter communicationTroposphere scatter communication
Are single hop systemAre single hop system Operates over length greater than LOS distanceOperates over length greater than LOS distance
Scatter region
Atmospheric turbulence and local variation of refractive index in the tropospheric region causes scattering of electromagnetic waves
Satellite Communication
04/12/23 RTTC \ SATCOM 11
50Km
10000Km
750Km
Troposphere scatter
1500Km
Ionosphere Reflection
SATELLITE
COMMUNICATIO
N
Satellite Communication
04/12/23 RTTC \ SATCOM 12
Earth
Global Coverage
Satellite Communication
04/12/23 RTTC \ SATCOM 13
Advantages Of Sat. Com
1. Large Coverage Area
2. High Quality
3. High Reliable
4. High Capacity
5. Flexibility
6. Easy For installation
7. Emergency Communication
8. Point to Multipoint transmission
Satellite Communication
04/12/23 RTTC \ SATCOM 14
Sat. Com Network
1. Space Segment
Upl
ink
Downlink
2. Ground Segment
Satellite Communication
04/12/23 RTTC \ SATCOM 15
Sat. Com Network
Frequency for space communication depends on
1. Band width required
2. Noise consideration
3. Propagation factor
4. TechnologyMost of the sat.Com uses 6/4Ghz frequency band
1. Less Atmospheric Absorption2. Less noise both galactic and manmade3. Less Space loss compared to high frequency
Satellite Communication
04/12/23 RTTC \ SATCOM 16
59000-64000Mhz & 54000-58000Mhz59000-64000Mhz & 54000-58000MhzV Band V Band
Inte.SatInte.Sat
40000-51000Mhz & 40000-41000Mhz40000-51000Mhz & 40000-41000MhzV BandV Band
INSATINSAT6725-7025Mhz & 4500-4800Mhz6725-7025Mhz & 4500-4800MhzExt “C”BandExt “C”Band
27500-30000Mhz & 17700 – 27500-30000Mhz & 17700 – 21200Mhz21200Mhz
““K”BandK”Band
14000-14500 & 10950-11200Mhz14000-14500 & 10950-11200Mhz
11450-11700Mhz11450-11700Mhz
““Ku” BandKu” Band
7900-8400Mhz &7250-7750Mhz7900-8400Mhz &7250-7750Mhz““X” BandX” Band
INSATINSAT5925-6425Mhz & 3700-4200Mhz5925-6425Mhz & 3700-4200Mhz““C” BandC” Band
INSATINSAT2500-2700Mhz2500-2700Mhz““S” BandS” Band
1830-2700Mhz1830-2700Mhz““L” BandL” Band
Frequency band for Sat. Com
Satellite Communication
04/12/23 RTTC \ SATCOM 17
Equator
4000miles
A
35786KmB
Geographical Advantage
Time Delay
Upl
ink
3578
6Km
250m
sec
Downlink 35786Km
250msec
Satellite Communication
04/12/23 RTTC \ SATCOM 18
Geostationary Satellite
Altitude:35786KmDirection :moves in eastern direction as earth
Period of revolution is 23Hr 56min34sec
EquatorEquator
Satellite Communication
04/12/23 RTTC \ SATCOM 19
Broadcasting mode of operation
Satellite Communication
04/12/23 RTTC \ SATCOM 20
Kinds of Communication Satellites
depends on type of orbit and freq. band used.
Communication Satellite can be classified by the orbit used and also by frequency band used.
natural laws that control the movement of satellites. These are based on Kepler's laws
1.The orbit plane of any earth satellite must bisect the Earth centrally.
2.The Earth must be at the centre of any orbit.
Satellite Communication
04/12/23 RTTC \ SATCOM 21
The choice of orbit is restricted to three basic types.
1.polar,
2.equatorial
3. inclined
Satellite Communication
04/12/23 RTTC \ SATCOM 22
Communication SystemsCommunication Systems Satellite communication systems are Satellite communication systems are
classified classified 1.Communication system
Multiplexed telephone channels with one (i) carrier frequency system, and (ii) Single channel per carrier system.
2.Modulation systemAnalog modulation (Frequency Modulation system),
and Digital modulation system
Satellite Communication
04/12/23 RTTC \ SATCOM 23
3.System configurationPre–assignment system
Demand assignment system, and
MULTIPLE ACCESS TECHNIQUES
the number of earth stations to be interconnected is such larger than the number of
transponders
the capacity of a transponder is much more than what is required between a pair of earth
stations;
Satellite Communication
04/12/23 RTTC \ SATCOM 24
Types of Multiple Access
Frequency Division Multiple Access (FDMA)
Time Division Multiple Access (TDMA)
Code Division Multiple Access (CDMA)
Satellite Communication
04/12/23 RTTC \ SATCOM 25
1. FDMA36Mghz36Mghz
E/S DE/S DE/S CE/S CE/S BE/S BE/S AE/S A
Transponder BW is divided into smaller frequency bands and assigning them to different E/S
E/S transmitting the carriers towards the satellite within the assigned frequency bands
Retransmitting the carriers from satellite after frequency translation and amplification by a common transponder
E/S receives all the carriers which contain telephony channels meant for the E/S
Satellite Communication
04/12/23 RTTC \ SATCOM 26
1. FDMA
A-B A-C A-D
Station AFM
SatelliteABCD ABCD
FM FM FM
Station C
DA B
A-C
Satellite Communication
04/12/23 RTTC \ SATCOM 27
TDMA
P B C D
PSKTDMABUFFER
TIMING INFORMATION
To UP-Converter
B
C
D
Satellite Communication
04/12/23 RTTC \ SATCOM 28
TDMA
P B C D
PSKTDMABUFFER
TIMING INFORMATION
To Down-Converter
B
C
D
P A B D P A C B
Satellite Communication
04/12/23 RTTC \ SATCOM 29
EQUIPMENT CONFIGURATION OFCOMMUNICATION
Satellite Communication
04/12/23 RTTC \ SATCOM 30
SPACE SEGMENT
A satellite consists of essentially two parts Communication payload Support subsystems
Communication payload for communication
satellites comprises
1.communication transponders
2.transmit/receive antennas.
Satellite Communication
04/12/23 RTTC \ SATCOM 31
Major support subsystems include :
Structure
Attitude and orbit control systems
Electrical power system
Thermal control system
Telemetry and Telecommand system
Satellite Communication
04/12/23 RTTC \ SATCOM 32