B-VHF Final Project Results – Brussels – 19. September 2006 Page: 1
Air Ground Communication Focus GroupMeeting
Brussels, 19. September 2006
B-VHF – Final ResultsC. Rihacek (FRQ), M. Schnell (DLR)
© B-VHF CONSORTIUM 2006File: B-VHF_AGCFG_Meeting_3.ppt Author: FREQUENTIS
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Contents
Main B-VHF Facts B-VHF Applicability Results of Physical Layer Simulations
• Sidelobe Suppression at the B-VHF Transmitter
• Simulation Scenarios for BER Evaluation
• BER Performance Without and With NBI Mitigation
Validation of B-VHF Approach• Laboratory measurements
• Measurement results
Conclusions and Outlook
© B-VHF CONSORTIUM 2006File: B-VHF_AGCFG_Meeting_3.ppt Author: FREQUENTIS
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Main B-VHF Facts
Broadband terrestrial cellular system based on multi-carrier technology• MC-CDMA for forward link (G/A)
• OFDMA for reverse link (A/G)
High capacity/high performance integrated voice and data link system tailored for specific aeronautical needs • Supporting existing and emerging applications and services
OFDM, OFDMA and MC-CDMA are mature technologies• Proven by high-capacity bandwidth-efficient techniques, like DAB,
DVB-T or W-LAN
• COTS products are already available (MC-CDMA adopted proposal for 4G)
Most modern and spectrum efficient technology
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Main B-VHF Facts
B-VHF is primarily designed as overlay system
Digital
B-VHF Channel
8,33 kHz VHF AM-Channel
25 kHz VHF AM-Channel
25 kHz VHF VDL-Channel
25 kHzFrequency
Analog
Power
Overlay concept enables in-band transition(e.g. VHF band)
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Applicability of B-VHF
B-VHF as overlay system (options)• VHF band
• Extended VHF band (COM+NAV+MIL)
• DME band
B-VHF without overlay (options)• VHF (COM/NAV/MIL) band, free certain parts
• DME band, use respective parts
• MLS band for A-SMGCS applications
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-200 -150 -100 -50 0 50 100 150 200
-80
-70
-60
-50
-40
-30
-20
-10
0
subcarrier index
po
we
r sp
ect
rum
(d
B)
Sidelobe Suppression at Tx
w/o sidelobe suppression:-22.8 dB
with 2 CCs:-38.3 dB
with 2 CCs& windowing:-51.4 dB
requirementsfulfilled
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Typical scenario• Available channels from NAVSIM tool (worst case)
• Actual interferers from measurement campaign
Worst case (WC) scenario• 1 MHz with max. number of interferers from measurements
Simulation Scenarios for FL
Spectrum Allocation
FL-ENR-WC
Scenario Interf.
6S/7W
Strong Interferer
Weak Interferer
B-VHF Channel (+Weak Interferer)Skipped Channel
2S/2W
Spectrum Allocation
FL-ENR
FL-TAKEOFF
FL-PARK
Scenario
1S/1W
Interf.
1S/2W
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BER Performance – ENR-WC Scenario
30 dB
Synchronisation and channel estimation work properly
Rx windowing not sufficient
Additional NBI mitigation required
required Rx power: -67 dBm !
worst case
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NBI Mitigation Techniques
Digital notch filtering• Assumption: A/D converter with sufficient resolution
• Only for strong interferers
Rx windowing in time domain• Simple method
• Slight extension of time domain signal required
• Peak of interferer is not reduced
Leakage compensation in frequency domain• Leakage effect due to DFT operation
• Estimation and compensation of interference
• Requires few observation subcarriers (reduced number of data subcarriers only for weak interferers)
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BER Performance – ENR-WC Scenario
required Rx power: -88 dBm
windowing
only strong NBIcompensated /notch filtered
weak & strong NBIcompensated
combination with windowing
worst case
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Laboratory Measurements
Measurements based on laboratory test-bed The B-VHF signal covers the maximum frequency
range symmetrical to the desired centre frequency of the DSB-AM receiver
System parameters• N_FFT = 128
• B = 266.66 kHz
• T_FRAME = 19.6 ms
• Tx windowing
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Laboratory Measurements
B-VHF interference on DSB-AM• Eight measurement scenarios
• Three different airborne, one ground victim receiver Rockwell Collins VHF 920 Honeywell KY176 B Dittel FSG90 Rohde & Schwarz ground receiver type series 200 (EU230)
• Four different assessments Squelch break SINAD ratio degradation PESQ criteria Signal to pulse ratio level
DSB-AM interference on B-VHF
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Selected Measurement Results
B-VHF interference on DSB-AM• Squelch break and SINAD measurements determine maximum
allowed B-VHF power @ DSB-AM victim receiver
• PESQ measurements lead to operational criteria for Frequency planning:Allow a B-VHF interference power value at the input of the DSB-AM airborne/ground receiver, which is 10 dB below the value which creates a 6 dB SINAD reduction at -85/-94 dBm.
DSB-AM interference on B-VHF• Without frequency gap (DSB-AM in B-VHF signal)
S/I = 15 dB leads to BER of 10-3
• With two VHF channels gap (DSB-AM in frequency gap) S/I = 5 dB leads to BER of 10-5
S/I < 3 dB forces synchronization failures
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Selected Measurement Results
Feasibility of overlay concept in VHF band• Assessment based on laboratory test-bed
• Spectral mask assumptions (worst case) DSB-AM and B-VHF output power 41 dBm Most critical receiver considered 600 m spatial separation required
• Assessment results under given assumptions Additional attenuation of 47 dB required in frequency gaps for 8.33
kHz mode and four channels notched out Additional attenuation of 54 dB required in frequency gaps for 25
kHz mode and two channels notched out
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Selected Measurement Results
Potential improvements of laboratory test-bed• Professional front-end design
Considerable noise level reduction Higher dynamic range (high-resolution DAC)
• Additional interference suppression at Tx 25-30 dB
Application of cancellation carrier technology Together with professional front-end design
• Increase bandwidth 6 dB From 266,67 kHz to 1066,67 kHz Respective power reduction in gap
• B-VHF output power reduction 10-20 dB Estimated power reduction Requires additional interference mitigation
at B-VHF Rx
> 55 dB
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Conclusions
Overlay concept and VHF in-band transition feasible• Theoretical considerations and simulations
• Laboratory measurements
Overlay concept requires additional efforts• Implementation of overlay specific techniques
• Reduced capacity during deployment
Applicability in non-VHF bands with or without overlay• DME band for ground-based aeronautical communications
• MLS band for airport communications
Scalability of B-VHF• B-VHF easily scalable (data rate/capacity ~ bandwidth)
• Large bandwidth enables high rate/capacity aeronautical communications for additional/new applications
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Outlook
Eurocontrol/FAA roadmap• Voice communication in VHF band using DSB-AM
• Data link communications in DME band
B-VHF technology is well suited for DME band• Main characteristics remain
High-capacity, high data-rate Flexibility and scalability
• Robustness against interference (DME, JTIDS)
• Possibility to apply overlay concept during deployment
Proposal: Investigate B-VHF technology for DME band