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EUROCONTROL RESEARCH & DEVELOPMENT CENTRE1 /
INNOVATIVE RESEARCH
XX
‘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
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE2 /
INNOVATIVE RESEARCH
‘Aircraft Identification Tag’ – AIT
IntroductionAIT TechnologyWatermark TechnologyAIT AdvantagesConclusion
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE3 /
INNOVATIVE RESEARCH
VHF Air/Ground Voice Communication
Party-line communication in a ATC sector:
One frequency for all AC and the unique ATC controllerFor identification all pilot voice messages
start with the AC call-sign
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE4 /
INNOVATIVE RESEARCH
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 controller’s workload
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE5 /
INNOVATIVE RESEARCH
‘Aircraft Identification Tag’ – AIT
IntroductionAIT TechnologyWatermark TechnologyAIT AdvantagesConclusion
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE6 /
INNOVATIVE RESEARCH
Technical Idea for a Solution
‘Watermark’ technique Watermark for paper
Digital ‘Watermark’ technique Commercial use for IPR protection:
Digital picturesDigital videosDigital audio sources….
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE7 /
INNOVATIVE RESEARCH
Aircraft Identification Tag - AIT
Tag
Aircraft Ground VHF-Radio Communication:
voice with added tag(hidden watermark)
Ground :
Special displays
Innovative functions in the ODS
Voice hearing Tag decoding and data dispatching an for supplementary visual stimulus
3D audio
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE8 /
INNOVATIVE RESEARCH
‘Aircraft Identification Tag’ - AIT
AIT’s aim for the air – ground voice link:
Automatic identification of the originatorNot noticeable for partners on the party-lineIn time with ongoing speech (real-time)Without any pilots interventionNo modification to existing AC equipmentsSecure voice link
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE9 /
INNOVATIVE RESEARCH
Digital Audio-Watermarks
Special audio watermark equipment:
Watermark EncoderWatermark Decoder
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE10 /
INNOVATIVE RESEARCH
VHF Communication Link
TX
RX
Voice frequency (analogue 300 …. 3400 Hz)
Aircraft system
ATC systemPTT* switch
* PTT (Push To Talk)
Data(e.g. Call-sign)
WatermarkEncoder
Including unnoticeable watermark
Tag
WatermarkDecoder
Innovative ATC functions
Data(e.g. Call-sign)
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE11 /
INNOVATIVE RESEARCH
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 < 14 db (similar channel signal noise ratio)
pure Speech~ 800 ms
Watermarked Speech
start delay
Microphone output
PTT
TX voice
t
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE12 /
INNOVATIVE RESEARCH
‘Aircraft Identification Tag’ – AIT
IntroductionAIT TechnologyWatermark TechnologyAIT AdvantagesConclusion
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE13 /
INNOVATIVE RESEARCH
Watermark Encoder (simplified)
001110110100101011110110010….
011110110101010101010101100….
Digital Speech
Digital Payload Data
A/DConverter
D/AConverter
Analogue Speech
Analogue Speech with Watermark
01101…
Digital Speech with Watermark
Encoder
WatermarkEmbedder
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE14 /
INNOVATIVE RESEARCH
Watermark Embedder
Payload Data
Speech
ChannelCoding
(BCH-Code)
MUX
Sync.Sequence
SpectralShaping
SpreadingSequence
MUX Multiplexer
SNR Signal Noise Ratio
SNRCalculation
Watermarked Speech
Watermark Data
Embedder
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE15 /
INNOVATIVE RESEARCH
Watermark Decoder (simplified)
A/DConverter
Analogue Speech with Watermark
Digital Speech with Watermark
Payload Data
01101..
WatermarkExtractor
011110110101010101010101100….
Decoder
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE16 /
INNOVATIVE RESEARCH
Watermark Extractor
Payload Data
ChannelCoding
(BCH-Code)
Sync.Sequence
Integrator
SpreadingSequence
Synchron.
Watermarked Speech
Time VariantWhitening
Filter
Confidence
Extractor
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE17 /
INNOVATIVE RESEARCH
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> 9000 voice samples1 payload data error
12 16 20 24 280
1
2
3
4
5
SWR [dB]
ME
R [
%]
Watermark floor
-18dB -24dB -28dB
k = 12bits
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE18 /
INNOVATIVE RESEARCH
‘Aircraft Identification Tag’ – AIT
IntroductionAIT TechnologyWatermark TechnologyAIT AdvantagesConclusion
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE19 /
INNOVATIVE RESEARCH
C W P
ATC Implementation of AIT
SSR Data(Position, Ident, FL)
RX - VHF Audio
OperationalDisplaySystem
Flight-PlanData
AIT Decoder(Payload Data+ Confidence)
Correlation(SSR/AIT) for
ODS Selection
Track Selection
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE20 /
INNOVATIVE RESEARCH
Track 4
Track1
Track2
Track3
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE21 /
INNOVATIVE RESEARCH
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
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE22 /
INNOVATIVE RESEARCH
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 controller’s 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
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE23 /
INNOVATIVE RESEARCH
‘Aircraft Identification Tag’ – AIT
IntroductionAIT TechnologyWatermark TechnologyAIT AdvantagesConclusion
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE24 /
INNOVATIVE RESEARCH
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 performanceRobustness against transmission problems (noise, fading, …)
Usage in general avionics for airfields Tested with VHF; usage in oceanic areas with HF
probable
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE25 /
INNOVATIVE RESEARCH
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)
EUROCONTROL RESEARCH & DEVELOPMENT CENTRE26 /
INNOVATIVE RESEARCH
?Aircraft Identification Tag - AIT
Thank you!