Adjacent Satellite Interference A Case Study SUIRG Annual Conference July 11- 13, 2006 Stockholm
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Transcript of Adjacent Satellite Interference A Case Study SUIRG Annual Conference July 11- 13, 2006 Stockholm
Adjacent Satellite Interference
A Case Study
SUIRG Annual ConferenceJuly 11- 13, 2006
Stockholm
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
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 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
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
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
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
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
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
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 - 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
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 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
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
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’
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
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
• 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