AIT

1
Konrad Hofbauer konrad.hofbauer_at_eurocontrol.int

• Aircraft Identification Tag (AIT)
• Radio message taggingThe system automatically
  complements each transmission with unnoticeable
  call-sign information.
• WatermarkingThe data is embedded into the
  analogue voice signal with standard watermarking
  techniques (e.g. Spread Spectrum).
• Automatic identificationThe receiver detects and
  displays the embedded information (within less
  than 1s).
• No modification to radio transmitters and
  receivers
• Previously developed systemFeasibility study and
  demonstrator in 1.

VHF air-ground voice communication

• Communication
• Air ground voice communication between
  controller and pilots
• Analogue VHF radio
• Party line channelThe controller and all
  aircrafts in an ATC sector communicate on the
  same frequency.
• Call-sign identificationPilot starts every
  message with its call-sign.
• Call-sign reception problemThere is a potential
  risk that the controller registers no or
  incorrect call-signs (due to technical and human
  factors).

Voice
Spectrum of voice signal with frequency- shaped
Spread-Spectrum watermark(simplified
illustration)
Watermark
Amplitude in dB
Frequency in Hz
Target objectives Target objectives Future research topics Future research topics
Capacity Capacity
Including aircraft position (by increasing payload data rate to up to 100 bit/s). Including aircraft position (by increasing payload data rate to up to 100 bit/s). Including aircraft position (by increasing payload data rate to up to 100 bit/s). Watermarking and data hiding algorithms Watermarking and data hiding algorithms Watermarking and data hiding algorithms
Inaudibility Inaudibility
Minimising the audibility and annoyance of introduced perceptual impairment. Minimising the audibility and annoyance of introduced perceptual impairment. Minimising the audibility and annoyance of introduced perceptual impairment. Speech impairment due to noise signals above the auditory masking thresholds Speech impairment due to noise signals above the auditory masking thresholds Speech impairment due to noise signals above the auditory masking thresholds
Reliability Reliability
Keeping error rate (system reports incorrect identification) smaller 10-4. Keeping error rate (system reports incorrect identification) smaller 10-4. Keeping error rate (system reports incorrect identification) smaller 10-4. Air-ground communication channel simulation and measurement Air-ground communication channel simulation and measurement Air-ground communication channel simulation and measurement
Security Security
Detecting unauthorised radio transmissions. Detecting unauthorised radio transmissions. Detecting unauthorised radio transmissions. Cryptography for systems with low data rate Cryptography for systems with low data rate Cryptography for systems with low data rate
Perceived quality Perceived quality
Increasing intelligibility of speech signal. Increasing intelligibility of speech signal. Increasing intelligibility of speech signal. Adaptive channel equalisation for highly time-varying systems Adaptive channel equalisation for highly time-varying systems Adaptive channel equalisation for highly time-varying systems
Reference 1 H. Hering, M. Hagmüller and G.
Kubin. Safety and security increase for air
traffic management through unnoticeable watermark
aircraft identification tag transmitted with the
VHF voice communication. In Proceedings of the
IEEE 22nd Digital Avionics Systems Conference
(DASC 2003).