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Aircraft Identification Tag AIT
Safety and Security Increase for ATM through
unnoticeable Watermark Aircraft Identification
Tag transmitted with the VHF Voice Communication
Horst Hering, ERC Bretigny, France Martin
Hagmüller, Gernot Kubin, TU Graz, Graz , Austria
XX
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Aircraft Identification Tag AIT

• Introduction
• AIT Technology
• Watermark Technology
• AIT Advantages
• Conclusion

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VHF Air/Ground Voice Communication

• Party-line communication in a ATC sector
• One frequency for all AC and the unique ATC
  controller
• For identification all pilot voice messages
  start with the AC call-sign

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Call-sign ambiguity through

• Low quality of the VHF transmission
• Call-sign is incompletely transmitted
• Very similar call-signs of different AC
• Pilot used a shorted/ omitted the call-sign
• Error of comprehension/ speaking
• Short AC transmission without any speech
• Controller occupied, caught parts of the msg.
  only

? Resulting by increase of controllers workload
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Aircraft Identification Tag AIT

• Introduction
• AIT Technology
• Watermark Technology
• AIT Advantages
• Conclusion

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Technical Idea for a Solution

• Watermark technique
• Watermark for paper
• Digital Watermark technique
• Commercial use for IPR protection
• Digital pictures
• Digital videos
• Digital audio sources
• .

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Aircraft Identification Tag - AIT
Aircraft ? Ground VHF-Radio Communication
voice with added tag (hidden watermark)
Innovative functions in the ODS
Special displays
Ground
3D audio
? Voice hearing ? Tag decoding and data
dispatching an for supplementary visual stimulus
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Aircraft Identification Tag - AIT

• AITs aim for the air ground voice link
• Automatic identification of the originator
• Not noticeable for partners on the party-line
• In time with ongoing speech (real-time)
• Without any pilots intervention
• No modification to existing AC equipments
• Secure voice link

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Digital Audio-Watermarks

• Special audio watermark equipment
• Watermark Encoder
• Watermark Decoder

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VHF Communication Link
Aircraft system
ATC system
TX
PTT switch
RX
Voice frequency (analogue 300 . 3400 Hz)
PTT (Push To Talk)
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AIT Specifications (basic)

• Payload Data (call-sign)
• 12 bits (SSR code)
• 24 bits (Mode S identifier)
• 36 bits (General avionic tail-number)
• Timing
• Signal Watermark Ratio
• lt 14 db (similar channel signal noise ratio)

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Aircraft Identification Tag AIT

• Introduction
• AIT Technology
• Watermark Technology
• AIT Advantages
• Conclusion

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Watermark Encoder (simplified)
Encoder
Digital Speech with Watermark
Analogue Speech
A/D Converter
D/A Converter
001110110 100101011 110110010 .
011110110 101010101 010101100 .
Digital Speech
0 1 1 0 1
Analogue Speech with Watermark
Digital Payload Data
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Watermark Embedder
Watermarked Speech
Speech
Sync. Sequence
Spreading Sequence
Spectral Shaping
SNR Calculation
MUX
Watermark Data
Channel Coding (BCH-Code)
MUX Multiplexer SNR Signal Noise Ratio
Embedder
Payload Data
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Watermark Decoder (simplified)
Decoder
Digital Speech with Watermark
A/D Converter
011110110 101010101 010101100 .
01101..
Analogue Speech with Watermark
Payload Data
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Watermark Extractor
Watermarked Speech
Extractor
Sync. Sequence
Spreading Sequence
Channel Coding (BCH-Code)
Integrator
Synchron.
Time Variant Whitening Filter
Payload Data
Confidence
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Results from Experiments

• Experiments (1000 watermarked voice samples /
  campaign)
• Data rate 80/ 100 bits per second
• Payload data 12/24/36 bits
• Dependency
• MER -- Signal Watermark Ratio/Watermark Floor
• Result (example)
• Data rate 80 bits/s
• Payload 12 bits
• Watermark floor 18db
• gt 9000 voice samples
• 1 payload data error

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Aircraft Identification Tag AIT

• Introduction
• AIT Technology
• Watermark Technology
• AIT Advantages
• Conclusion

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ATC Implementation of AIT
SSR Data (Position, Ident, FL)
RX - VHF Audio
Flight-Plan Data
C W P
Operational Display System
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Track1
Track3
Track2
Track 4
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Benefits from AIT (I)

• Air-Ground Voice Communication
• Automatic identification of the originator
  (signature)
• Security against fake voice com. (terrorists)
• No modification to certified AC equipment
• Not noticeable for party-line partners

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Benefits from AIT (II)

• ATC System
• Digital AC call sign is available in time with
  pilots VHF voice communication
• Innovative functions on the ODS (i.e. Radar track
  selection during voice communication)
• Support of controllers SA through supplementary
  visual stimuli's
• Add redundancy to the voice channel AC
  identification
• Prevent from supplementary workload caused by
  call-sign ambiguity for the controller
• Support for correlation unusual AC telephone
  names and belonging 3-letter call-signs (e.g.
  Airkibris ? KYV)
• Protection against fake AC voice communication

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Aircraft Identification Tag AIT

• Introduction
• AIT Technology
• Watermark Technology
• AIT Advantages
• Conclusion

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AIT for Air-Ground Voice Communication

• Benefit for safety of air transportation
• Address the security aspect against fake voice
  com.
• Automatically without any humans intervention
• Standard technology no AC modification
• Realised demonstrator
• High performance
• Robustness against transmission problems (noise,
  fading, )
• Usage in general avionics for airfields
• Tested with VHF usage in oceanic areas with HF
  probable

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Speech Samples

• Original speech (without watermark)
• Watermarked speech (W-floor -20db SWR 16db)
• Watermarked speech (W-floor -24db SWR 20db)
• Watermarked speech (W-floor -28db SWR 24db)

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Aircraft Identification Tag - AIT
?

• Thank you!