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Snjezana Gligorevic and Michael Schnell German Aerospace Center - DLR

B-VHF System Concept. Channel Occupancy and Capacity Analysis. Snjezana Gligorevic and Michael Schnell German Aerospace Center - DLR. Overview. B-VHF in Current VHF Band Situation NavSim Simulations Channel Occupancy Measurements B-VHF System Design Conclusion.

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Snjezana Gligorevic and Michael Schnell German Aerospace Center - DLR

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  1. B-VHF System Concept Channel Occupancy and Capacity Analysis Snjezana Gligorevic and Michael Schnell German Aerospace Center - DLR

  2. Overview • B-VHF in Current VHF Band Situation • NavSim Simulations • Channel Occupancy Measurements • B-VHF System Design • Conclusion

  3. Current VHF Band Situation – Theoretical 25 / 8.33 kHz channel spacing All channels continuously allocated & used Power Frequency 25 kHz 25 kHz VHF AM-Channel Analog 8.33 kHz VHF AM-Channel Digital 25 kHz VHF VDL-Channel

  4. Power Frequency 25 kHz Current VHF Band Situation – Practical 25 / 8.33 kHz channel spacing Only a part of the allocated channels are used Not all channels are ‘seen’ with full power all the time 25 kHz VHF AM-Channel Analog 8.33 kHz VHF AM-Channel Digital 25 kHz VHF VDL-Channel

  5. Power Frequency 25 kHz 25 kHz VHF VDL-Channel Digital B-VHF Channel B-VHF Overlay System 25 / 8.33 kHz channel spacing Only a part of the allocated channels are used Not all channels are ‘seen’ with full power all the time 25 kHz VHF AM-Channel Analog 8.33 kHz VHF AM-Channel

  6. NavSim Simulations • Worst Case Simulation • Considerable more occupied VHF channels expected than in measurement flights! • All ground stations (100% duty cycle) and ATC sectors within radio horizon considered. • Each ATC sector is represented by a worst-case interfering A/C, i.e. interfering A/C (100% duty cycle) is located at the border of ATC sector next to victim receiver (observation point).

  7. B-VHF Cell Cell Radius Cell Center B-VHF A/C DSB-AM A/C NavSim Simulations – Worst Case Interfering A/C ATC Sector

  8. NavSim Simulations • Worst Case Simulation • Considerable more occupied VHF channels expected than in measurement flights! • All ground stations (100% duty cycle) and ATC sectors within radio horizon considered. • Each ATC sector is represented by a worst-case interfering A/C, i.e. interfering A/C (100% duty cycle) is located at the border of ATC sector next to victim receiver (observation point). • Multiple observation points; 12 points on a circle representing a fictitious B-VHF boundary

  9. Cell Radius B-VHF A/C DSB-AM A/C NavSim Simulations – Multiple Observation Points ATC Sector B-VHF Cell Cell Center

  10. NavSim Simulations – Results

  11. NavSim Simulations – Results

  12. NavSim Simulations – Results

  13. Results of Measurements Worst case Simulations EBBR / EDDM 6.4% / 17.6% 67.2%/ 79.1%

  14. Cell Radius DSB-AM A/C Max. Interference -95.0 dBm B-VHF System Design – Link Budget Analysis B-VHF Cell ATC Sector Distance? Cell Center B-VHF A/C Power? 41.0 dBm

  15. Cell Radius20 nm B-VHF A/C DSB-AM A/C Example – Link Budget Analysis Threshold: -75 dBm (65% VHF band available @ EDDM) B-VHF Cell Interference Power10.2 dBabove Signal Level 42 nm Cell Center -78.4 dBm -75.0 dBm 41.0 dBm -88.6 dBm 21.0 dBm -95.0 dBm -85.2 dBm 24.4 dBm -95.0 dBm Interference Power10.2 dBabove Signal Level

  16. Conclusions • Interference towards DSB-AM can be avoided! • B-VHF Tx power < 21 dBm (A/C) and < 24.4 dBm (GS) • With respect to SNR, small B-VHF Tx power no problem(SNR > 64 dB for 25 kbit/s transmission per 25 kHz) • This holds even for the “-75 dBm” threshold (worst case) • Large interference from DSB-AM towards B-VHF • Worst case interference on used subcarriers within B-VHF system is10.2 dB above B-VHF signal level • Actual interference is much lower then the simulated worst case • Actual interference is not present all the time (duty cycle!) • B-VHF overlay system able to cope with large interference power levels • Spread-spectrum system • Interference reduction by spreading (diversity) and coding • Final verification of B-VHF system concept with simulations

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