adjacent satellite interference a case study suirg annual conference july 11- 13, 2006 stockholm
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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 - PowerPoint PPT PresentationTRANSCRIPT
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Adjacent Satellite Interference
A Case Study
SUIRG Annual ConferenceJuly 11- 13, 2006
Stockholm
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C or Ku-Band Satellite dishEMR5520/5020
PAL TV
RG-6 Plenum
PAL ChannelModulator #1
PAL ChannelModulator #2
Tivella STB#2
Tivella STB#1
NetworkSwitch
Combiner
RG-6
EDS IP Addition-DownlinkA. Porter 11.4.2004
VideoOut
VideoOut
AudioOutLeft
AudioOutRight
AudioOutLeft
AudioOutRight
Ethernet Ethernet
Eth2/LAN2
Satellite In ForEMR5020.PCI1 forEMR5520
Installer Laptop computer
Eth1/LAN1
CAT5e
CAT5eCross Over
Cable
Block Diagram
Receive Only Site
2.4M Antenna
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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
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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
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10°
0°
Fuchsstadt
SpeedLink40: Forward link - User terminal antenna size IX (902) at 62.0°E , 5.97 GHz Up, 3.75 GHz Down Data rate: 3041 kbps, User terminal availability: 99.900% Uplink beam: IZ1 (NW), Downlink beam: IH2 (EH)
<2.4m2.4m to 2.8m2.8m to 3.2m3.2m to 3.7m>3.7m
Coverage Map – Installed Sites
ChennaiPune
Mumbai
Gurgaon
<2.4M
2.4M to 2.8M
2.8M to 3.2M
3.2M to 3.7M
>3.7M
Recommended Antenna Size
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2.4M Reference Site - BangaloreCarrier 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
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3.8M Test - BangaloreCarrier as seen on 3.8M Receiver Statistics
Good Eb/No = 7.4dB
Uncorrected Errors = 0
Works fine - Both TV Channels received properly
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2.4M vs 3.8M- BangaloreCarrier 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
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2.4M Client site - ChennaiCarrier 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 outSuspect Antenna Orientation, Cabling, Link Budget Errors
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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
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2.4M Client site - PuneCarrier 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
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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
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Adjacent Satellite PlotsPlots of signals 1422.6MHZ on 2.4M
SAT0 - Sat. of Interest SATW - Sat. 2º WestSATE - 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
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Measurements with Carrier OffPlot 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
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Comparision of SignalsSignals seen on 2.4M Prodelin Antenna
Carriers on SATW. Taken at 20MHz span centered around1422.6 MHz
Plot seen on SAT0 with Carrier ‘OFF’
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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 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
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Results at New Frequency
• 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
Carrier as seen on 2.4M Receiver Statistics
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• 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
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THANK YOU