b-vhf final project results – brussels – 19. september 2006 page: 1 air ground communication...

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)

[email protected], [email protected]

© 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


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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)



BER Performance – ENR-WC Scenario

required Rx power: -88 dBm

windowing

only strong NBIcompensated /notch filtered

weak & strong NBIcompensated

combination with windowing

worst case



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



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



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




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




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



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



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

b-vhf final project results – brussels – 19. september 2006 page: 1 air ground communication...

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