SATELLITE LINK DESIGN

EC8094 SATELLITE COMMUNICATION UNIT III SATELLITE LINK DESIGN

UNIT III
SATELLITE LINK DESIGN


Basic link analysis, Interference analysis, Rain induced attenuation and interference, Ionospheric
characteristics, Link Design with and without frequency reuse.


3.1 Basic link analysis
3.2 Interference analysis
3.2.1 Carrier-to-Noise plus Interference Ratio
3.2.2 Interference into or from Adjacent Satellite Systems
3.2.3 Terrestrial Interference
3.2.4 Cross-polarization Interference
3.2.5 Adjacent Channel Interference
3.2.6 Intermodulation Interference
3.2.7 Intersymbol Interference
3.3 Rain induced attenuation and interference
3.3.1 Prediction of Attenuation
3.3.2 Effect of Rain Attenuation on System Noise Temperature
3.3.3 Carrier-to-Noise plus Interference Ratio Including Rain-Induced Attenuation
3.3.4 Path Diversity
3.3.5 Uplink Power Control
3.4 Rain-Induced Cross-Polarization Interference (Extra)
3.5 Ionospheric characteristics
3.6 Link Design with and without frequency reuse.
3.6.1 Satellite Link Design
3.6.2 Link without Frequency Reuse
3.6.3 Link with Frequency Reuse
3.2.6 Intermodulation Interference
3.2.7 Inter-symbol Interference
3.3 Rain induced attenuation and interference
3.3.1 Prediction of Attenuation
3.3.2 Effect of Rain Attenuation on System Noise Temperature
3.3.3 Carrier-to-Noise plus Interference Ratio Including Rain-Induced Attenuation
3.3.4 Path Diversity

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Compiled by: Mr. S.Parthiban, M.Tech.., Asst. Prof., Dept. of ECE, VRSCET.

,EC8094 SATELLITE COMMUNICATION UNIT III SATELLITE LINK DESIGN

3.3.5 Uplink Power Control
3.4 Rain-Induced Cross-Polarization Interference (Extra)
3.5 Ionospheric characteristics
3.6 Link Design with and without frequency reuse.
3.6.1 Satellite Link Design
3.6.2 Link without Frequency Reuse
3.6.3 Link with Frequency Reuse




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Compiled by: Mr. S.Parthiban, M.Tech.., Asst. Prof., Dept. of ECE, VRSCET.

,EC8094 SATELLITE COMMUNICATION UNIT III SATELLITE LINK DESIGN

3.1 Basic link analysis
Derive a formula for the combined C/N ratio of bent-pipe transponder satellite link. [Nov/Dec
2022][Nov 2023][Apr 2023]
➢ Consider a basic satellite link shown in Fig. 3.1.




Figure 3.1: Basic Satellite Link
➢ The transmit earth station transmits the carrier s(t) whose power is simply the EIRP of the
carrier given by:
EIRP = PT GT → (3.1)
Where,
PT = carrier power at antenna feed
GT = transmit antenna gain.
➢ For the time being we assume that the transmission occurs under clear-sky conditions and that the only
attenuation the carrier s (t ) suffers is the uplink free space loss, the atmospheric attenuation and the
antenna tracking loss.
➢ The uplink free space loss is given by
2
 4d u   4f u d u 
2

Lu =   =   → (3.2)
 u   c 
Where,
du → Uplink slant range (m)
fu → Uplink wavelength (m)
u → Uplink carrier frequency (Hz)
c → Speed of light = 2.997925  108 m/s

➢ Let S u (t ) be the carrier received at the satellite and nu (t ) the AWGN with zero mean that
contaminates the uplink carrier S u (t ) .
➢ Then the received carrier plus noise at the satellite is S u (t ) + nu (t ) .
➢ If the satellite antenna gain is Gu , the uplink carrier power, that is, the power of S u (t ) , is


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Compiled by: Mr. S.Parthiban, M.Tech.., Asst. Prof., Dept. of ECE, VRSCET.

, EC8094 SATELLITE COMMUNICATION UNIT III SATELLITE LINK DESIGN


Cu = E[ Su2 (t )]
( EIRP)Gu
=
Lu L
2
( EIRP)  c 
=   Gu → (3.3)
L  4fu du 
Where E[·] denotes the expected value and L is the sum of the antenna tracking loss and
atmospheric attenuation.
➢ The uplink noise power is (derived result : Not shown here)
N u = E[nu2 (t )]
= kTu B → (3.4)


where Tu = Satellite system noise temperature (K) and can be calculated from the noise
temperature of the satellite antenna (which is about 290 K since the antenna always
sees a hot earth) and the equivalent noise temperature of the satellite
communications repeater shown in Fig. 3.1.
B= noise bandwidth of satellite channel (Hz)
k= Boltzmann’s constant = 1.38  10-23 J/K

➢ The parameter G u / Tu is the satellite antenna gain-to-noise temperature ratio.
➢ From (3.3) and (3.4) the uplink carrier-to-noise ratio is
C C u  EIRP   Gu   1 
  = =     
 N  u N u  Lu L   Tu   kB 
2
( EIRP )  c   Gu   1 
=       → (3.5)
L  4f u d u   Tu   kB 
➢ Note that ( EIRP ) / 4d u L is simply the carrier power flux density (W/m2) at the satellite:
2


( EIRP)
= → (3.6)
4d u2 L

 4f 2 
➢ Also, the term  2u  is simply the gain of an ideal antenna whose aperture area is l m2 , when =

 c 
l and A = 1 m2 :

4f u2
G1m2 = → (3.7)
c2

Substituting (3.6) into (3.5) yields




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Compiled by: Mr. S.Parthiban, M.Tech.., Asst. Prof., Dept. of ECE, VRSCET.