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Adjacent Satellite Interference A Case Study SUIRG Annual Conference July 11- 13, 2006 Stockholm

Adjacent Satellite Interference A Case Study SUIRG Annual Conference July 11- 13, 2006 Stockholm. 2.4M Antenna. Receive Only Site. Block Diagram. User Application. IP streaming based BTV satellite network

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Adjacent Satellite Interference A Case Study SUIRG Annual Conference July 11- 13, 2006 Stockholm

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  1. Adjacent Satellite Interference A Case Study SUIRG Annual Conference July 11- 13, 2006 Stockholm

  2. 2.4M Antenna Receive Only Site Block Diagram

  3. User Application • IP streaming based BTV satellite network • The IP streaming network is broadcast on a 2.75MHz carrier allowing for two IPTV channels using 1.2 MB of data each. • The Skystream EMR-5000\5520 receives the DVB carrier, decapsulates the IP data and forwards Multicast on to the LAN. • The Set Top Box decodes the Multicast IPTV streams and outputs analog audio and video for viewing on a normal PAL TV set

  4. Bench Mark Parameters • Receive Signal is at 3727.5MHz, RHCP (LNB Output=1422.6MHz) • Signal Strength of > -65dBm for the Skystream Receiver • Signal Lock • Eb/No of > 6dB (indicated on the Skystream Receiver) • LNB Offset of < 1 (indicated on the Skystream Receiver) • Reed Solomon Uncorrected Errors less than 5 over a period of 1Hr

  5. Gurgaon Mumbai Pune Chennai Coverage Map – Installed Sites <2.4M 2.4M to 2.8M 2.8M to 3.2M 3.2M to 3.7M >3.7M Recommended Antenna Size

  6. 2.4M Reference Site - Bangalore Receiver Statistics Carrier as seen on 2.4M Very High Uncorrected Errors Low Eb/No = 3dB Possible Causes - Terrestrial Interference - Lower Gain in Rx chain Next Step: Try the same setup on a 3.8M Antenna

  7. 3.8M Test - Bangalore Carrier as seen on 3.8M Receiver Statistics Good Eb/No = 7.4dB Uncorrected Errors = 0 Works fine - Both TV Channels received properly

  8. 2.4M vs 3.8M- Bangalore Carrier as seen on 2.4M Carrier as seen on 3.8M • 3.8M Results is in line with expectations • 2.4M Carrier ‘shape’ is suspicious. However no reasons attributed Next Step: Install 2.4M setup at Chennai and study performance

  9. 2.4M Client site - Chennai Receiver Statistics Carrier as seen on 2.4M Neglect this spike. It was a characteristic of the receiver when the LNB is powered from receiver. It was proved that this has no bearing on the results • Similar results as in Bangalore • Carrier parameters are as expected • Low Eb/No and High Number of errors Terrestrial Interference is ruled out Suspect Antenna Orientation, Cabling, Link Budget Errors

  10. Link Budget Analysis • C/N Measured on 2.4M at Bangalore is 7.9dB.This is as expected from the Link Calculations. • Eb/No measured is significantly lesser than Link Calculations. • Suspect Interfering signals, but source is not known. • Suspect that locations Bangalore and Chennai lie in weaker signal zone as per coverage map. Next Step: Install 2.4M setup at Pune which is in a stronger signal region

  11. 2.4M Client site - Pune Receiver Statistics Carrier as seen on 2.4M • C/N and Eb/No is better by about 1dB • Eb/No is below spec of 6dB • Uncorrected Errors are High • Suspect Rx signal level is too low for the IP Receiver Next Step: Use a Line Amplifier in Rx chain to improve signal level

  12. 2.4M - Bangalore with Line Amp Carrier as seen on 2.4M Receiver Statistics • Signal Level has improved • Eb/No is still at 3dB • Uncorrected Errors are High • Suspect Interfering Signal (Most Probably from Adjacent 2º Satellite) Next Step: Check for Signals in Adjacent Satellites

  13. Adjacent Satellite Plots Plots of signals 1422.6MHZ on 2.4M SATE - Sat. 2º East SAT0 - Sat. of Interest SATW - Sat. 2º West • SATW shows a large Carrier at the same frequency as our Downlink • 3dB Beamwidth of 2.4M Antenna is 2.2º. • Suspect strongly that SATW signal is the source of Interference Next Step: Switch Off SAT0 signal and make measurements

  14. Measurements with Carrier Off Plot on 2.4M Plot on 3.8M • 2.4M plot shows potential spurious signals • 3.8M plot is relatively clean • 3dB Beamwidth of 3.8M is 1.5º may not pick up signals from Adjacent 2º Satellite

  15. Comparision of Signals Signals seen on 2.4M Prodelin Antenna Carriers on SATW. Taken at 20MHz span centered around 1422.6 MHz Plot seen on SAT0 with Carrier ‘OFF’

  16. Conclusion • Problem is repeated at 3 Geographically different locations. Terrestrial Interference is ruled out • Rx signal levels and C/N as per Link CalculationsAntenna Orientation, Cabling issues are ruled out • Line Amplifier did not have any effectLow signal level is ruled out • Signal Interference is the causeSource of Interference is strongly suspected to be from Adjacent Satellite Next Step: Shift to a new Downlink Frequency

  17. Results at New Frequency Carrier as seen on 2.4M Receiver Statistics • New Frequency is 3895.64MHz (LNB = 1254.35Mhz) , RHCP • Eb/No =8.9dB and Uncorrected Errors = 0 • All results achieved with only change in Downlink Frequency • No other change in Antenna position or any other equipment

  18. Closing Observations • Satellite Operator decided to freeze on New Frequency and Level • All 4 Client Locations were successfully installed after this • The entire effort resulted in large delays and escalation of costs • Troubleshooting effort was complicated as many parties were involved needing close co-ordination. • Same problem may occur in future if frequency in Adjacent Satellite is re-allocated without taking our application into account. • Urgent need to review the use of 2.4M Antennas with 2-degree spacing Satellites • Similar Case studies on other Satellites, Applications and Antennas needs to be published with a view to reducing troubleshooting effort

  19. THANK YOU

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