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

Block Diagram Receive Only Site 2.4M Antenna

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

Bench Mark Parameters Receive Signal is at MHz, 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

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

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

3.8M Test - Bangalore Carrier as seen on 3.8MReceiver Statistics Good Eb/No = 7.4dB Uncorrecte d Errors = 0 Works fine - Both TV Channels received properly

2.4M vs 3.8M- Bangalore Carrier as seen on 2.4MCarrier 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

2.4M Client site - Chennai Carrier as seen on 2.4M Receiver Statistics 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

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

2.4M Client site - Pune Carrier as seen on 2.4M Receiver Statistics 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

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

Adjacent Satellite Plots Plots of signals MHZ on 2.4M SAT0 - Sat. of Interest SATW - Sat. 2º West SATE - Sat. 2º East 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

Measurements with Carrier Off Plot on 2.4MPlot 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

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

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

Results at New Frequency New Frequency is MHz (LNB = Mhz), 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 Carrier as seen on 2.4M Receiver Statistics

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 Closing Observations

THANK YOU