Satellite Link Design: C/N Ratio
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C/N Ratio calculation
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Satellite Link Design: C/N Ratio
- 1. Arpan Deyasi Dept of ECE, RCCIIT, Kolkata, India Course: MCE203A Satellite Link Design: Part-II 4/21/2020 1Arpan Deyasi RCCIIT MCE203A
- 2. Satellite Link Design Objective 1. Meeting a minimum C/N (Carrier Signal-to-Noise) ratio for a specified time-period 2. Carrying maximum traffic at minimum cost 4/21/2020 2Arpan Deyasi RCCIIT MCE203A
- 3. Link Design Procedure [i] Determine frequency band in which system will operate [ii] Determine communication parameters of satellite [iii] Calculate S/N and BER for baseband channel [iv] Determine the parameters for transmitting and receiving Earth stations [v] For transmitting uplink, calculate C/N for uplink using uplink budget and transponder noise power budget [vi] Based on gain of the transponder, calculate output power of the Transponder [vii] Determine C/N for downlink and establish noise budget for receiving Earth station [viii] Calculate values of all the loss parameters due to atmospheric Conditions [ix] Determine link margin by calculating the link budget 4/21/2020 3Arpan Deyasi RCCIIT MCE203A
- 4. Carrier-to-Noise Ratio Noise power of the receiver TBkP Bn = If ‘G’ be the overall gain of the receiver GTBkP Bn = If ‘PR’ be the signal power at the input GPC R= 4/21/2020 4Arpan Deyasi RCCIIT MCE203A
- 5. Carrier-to-Noise Ratio TBk P N C B R = Therefore, Carrier-to-Noise power is Substituting the value of ‘PR’ is 2 4 = RTBk GGP N C B RTT π λ T G Rk GP N C R B TT = 2 4π λ 4/21/2020 5Arpan Deyasi RCCIIT MCE203A
- 6. Carrier-to-Noise Ratio T G N C ∝ G = GR, gain of the receiver For a given satellite, ‘R’ and ‘λ’ are constant G/T ratio is called Figure of Merit of Earth station B NN =0 called Noise Power Spectral Density 0 4 10log( ) 20log 10log 10logR T T B dB C R G P G k N T π λ = − + − 4/21/2020 6Arpan Deyasi RCCIIT MCE203A
- 7. Effect of Uplink on C/N Ratio Non-linear effects are included in C/N ratio for uplink by including back-off terms [ ] 0 4 10log( ) 20log 10log 10log T T dB R B u C R P G N G k BO T π λ = − + − − 4/21/2020 7Arpan Deyasi RCCIIT MCE203A
- 8. Effect of Downlink on C/N Ratio Non-linear effects are included in C/N ratio for the downlink by including back-off terms [ ] 0 4 10log( ) 20log 10log 10log T T dB R B D C R P G N G k BO T π λ = − + − − 4/21/2020 8Arpan Deyasi RCCIIT MCE203A
- 9. Complete Link Design Useful carrier signal at the receiving Earth station is L GGGC N C RTSU = 0 CU: signal power at satellite transponder point GS: satellite transponder gain GT: satellite transmitting antenna gain GR: satellite receiving antenna gain 4/21/2020 9Arpan Deyasi RCCIIT MCE203A
- 10. Complete Link Design Noise power spectral density at the input of Earth station receiver is L GGG NNN RTS UD )( 000 += N0: noise power density at transponder input N0D: noise power density at the input of Earth station receiver N0U: noise power density at the input of Earth station transmitter 4/21/2020 10Arpan Deyasi RCCIIT MCE203A
- 11. Complete Link Design + == L GGG NN L GGGC N C N C RTS UD RTSU T )( 00 00 RTS D U U T GGG LN N C N C 0 0 0 + = 4/21/2020 11Arpan Deyasi RCCIIT MCE203A
- 12. Complete Link Design For a transponder having bandwidth ‘B’ and radiating constant power ‘PT’, Its gain ‘GS’ is defined as BNC P G UU T S 0+ = For downlink, signal power ‘CD’ is L GGP C RTT D = 4/21/2020 12Arpan Deyasi RCCIIT MCE203A
- 13. Complete Link Design B N C N C N C N C N C DU DU T + + = 00 00 0 Since ‘B’ is much smaller compared with both C/N ratio DUT N C N C N C + = −−− 1 0 1 0 1 0 4/21/2020 13Arpan Deyasi RCCIIT MCE203A
- 14. Complete Link Design DU N C N C >> 00 DT N C N C ≈ −− 1 0 1 0 Complete link design depends on C/N ratio of downlink 4/21/2020 14Arpan Deyasi RCCIIT MCE203A
- 15. Interference Effect on C/N Ratio Interference effect on uplink is given by UUuplinkNet I C N C N C + = −− − − 11 0 1 0 I: noise power involved with interfering signal 4/21/2020 15Arpan Deyasi RCCIIT MCE203A
- 16. Interference Effect on C/N Ratio Interference effect on downlink is given by DDdownlinkNet I C N C N C + = −− − − 11 0 1 0 4/21/2020 16Arpan Deyasi RCCIIT MCE203A
- 17. Interference Effect on C/N Ratio Net carrier to noise ratio in presence of interfering signal downlinkNetuplinkNetNet N C N C N C − − − −− + = 1 0 1 0 1 0 + + + = −− −− − DD UU Net I C N C I C N C N C 11 0 11 0 1 0 4/21/2020 17Arpan Deyasi RCCIIT MCE203A
- 18. + = −−− 11 0 1 0 I C N C N C Net Interference Effect on C/N Ratio where DU I C I C I C + = −−− 111 4/21/2020 18Arpan Deyasi RCCIIT MCE203A
- 19. Interference Effect on C/N Ratio For noise dominance > N C I C For interference dominance < N C I C 4/21/2020 19Arpan Deyasi RCCIIT MCE203A
- 20. https://www.tutorialspoint.com/satellite_communication/satellite_ communication_link_budget.htm References 4/21/2020 20Arpan Deyasi RCCIIT MCE203A T. Pratt, C. Bostian, J. Allnutt, “Satellite Communications”, John Wiley & Sons, 2nd Ed., 2003 A. K. Maini, V. Agarawal, “Satellite Communications”, Wiley, 1st Ed., 2019 S. Katiyar, “Satellite Communication”, S. K. Kataria & Sons, 1st Ed., 2007