Long Term Investigations, EEC Towards Selective Addressing of Aircraft with Voice Radio Watermarks Horst Hering, Konrad Hofbauer EUROCONTROL Experimental Centre (EEC), Bretigny, France 1 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Outline Introduction Aircraft Identification Tag (AIT) basics AIT benefits Motivation for R&D Issues of the radio communication Proposed solution Selective PTT switch Demonstrator Experimentation Results and conclusion 2 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Introduction Air traffic guidance based on: Standardised voice radio communication VHF channels (118…133 MHz) AM - modulation technique known to be sensitive for disturbance - poor voice quality Party line concept One voice channel /sector One controller All aircraft obligation for identification (down- & up-link) VHF VHF Voice Signal Voice Signal Transmitter Receiver (pilot/ ATCO) (ATCO /pilot) PTT Switch 3 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Aircraft Identification Tag * FM broadcast radios Radio Data System - RDS identify radio channel for listener Watermark techniques for conventional ATC radio channels Embedding digital data in analogue speech Not noticeable in transmitted speech Watermark VHF Voice Signal Embedder Transmitter (pilot/ ATCO) PTT Switch Signature (Originator) * H. Hering, M. Hagmueller, 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 22nd Digital Avionics Systems Conference (DASC 2003), Indianapolis, USA (2003) 4 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Aircraft Identification Tag 5 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC AIT Initial Feasibility Study* Deployment-driven requirements Rapid and simple deployment Legacy system compliance Bandwidth efficiency Minimal aircraft modifications Cost efficiency User-driven requirements Perceptual quality Data rate Real-time availability Error rate Maintaining established procedures No user interaction *AIT- Initial Feasibility Study, EATMP Info-centre, EUROCONTROL Brussels, Belgium (2006) (consortium: Sofreavia, Frequentis, Rockwell-Collins) 6 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Current AIT R&D Speech consists of segments with: periodic structure - voiced speech (vowel, semi-vowels and nasal sounds) noise-like structure - unvoiced speech (most of the consonants) Watermarking in unvoiced speech* Advantages High perceptual quality High data rate (capacity) Ex.: Original signal Ex.: Watermarked signal with 2000 bits per second *K. Hofbauer and G. Kubin, “High-rate data embedding in unvoiced speech,” in Proceedings of the International Conference on Spoken Language Processing (INTERSPEECH), (Pittsburgh, PY, USA), Sept. 2006. 7 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Aircraft Identification Tag Benefits Call sign confusion and ambiguity “Mis-identification” Safety Threat Malicious messages Radio transmissions issued by unauthorized 3rd party Security Threat Increase ATCO’s situation awareness Visual stimuli reinforce audio hearing 8 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Motivation for R&D High load of the radio communication channel over core Europe Small sectors (5…7 minutes fly through time) VOCALIS study* 60 hours of voice communications 12 different French en-route sectors featuring heavy traffic periods Watching party line is a hard task for pilots Average of 324 speech acts per hour About 5 speech acts per minute *L. Graglia et al., “VOCALISE: Assessing the Impact of Data Link Technology on the Radio Telephony Channel”, in proceedings of the 24th Digital Avionics Systems Conference (DASC 2005), Washington DC, USA (2005) 9 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Issues for the Radio Communication AIT downlink of a digital aircraft signature for the ATCO to increase safety and security Uplink of the aircraft address ??? similar benefits for the aircrew Generation of an attention getter 10 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Proposed Solution Uplink the aircraft address via AIT Watermark VHF Voice Signal Embedder Transmitter (ATCO) PTT Switch Signature Address (ATCO) (Destination) ATCO has to indicate the destination of each voice message to the AIT system On board of the addressed aircraft an attention getter is created 11 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Selective PTT Switch Concept Watermark VHF Voice Signal Embedder Transmitter (ATCO) Selective PTT ‘Mouse’ Signature Position (ATCO) Address (aircraft) Last AC AIT ATM System The selective PTT switch: Triggers the radio transmitter Interacts with the ATM system to define the called aircraft address 12 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Selective PTT Switch Logic Last aircraft calling in (AIT) is memorised for ~20 seconds Physical PTT switch triggers a selective logic Selective logic: Mouse cursor hovers above memorised aircraft this aircraft is called if PTT switch pressed Mouse cursor does not hover above an aircraft this memorised aircraft is called if PTT switch pressed Mouse cursor hovers above different aircraft this aircraft is called if PTT switch pressed memorised unanswered aircraft is highlighted for 2 seconds Mouse cursor hovers above ‘Public’ call button all aircraft in the sector are called 13 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Selective PTT Switch Based on AIT watermark technology Uplink voice messages with an embedded digital destination address Supports aircrew with automatic attention getter for ‘own’ radio messages Benefits for on board safety Benefits for the secured voice communication Implements digital features in analogue radio communication 14 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Selective PTT Switch Demonstrator Demonstrator setup Static air traffic situation (simulation screen shoot) Animated with audio and visual cues Aircraft calling in AIT highlighting of the aircraft calling in Selective PTT switch representation 15 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Demonstrator Screen 16 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Calling Aircraft Demonstrator assumption: all aircraft AIT equipped Blinking frame while aircraft is calling in 17 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Selective PTT Switch Pressed Calling LOT232 - aircraft that called in last Calling YUBRZ - system reminds that LOT232 called last 18 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Demonstration/ Experiments 12 operational experts of the EEC (ex-controllers) From 8 different European countries Period August 2007 Questionnaire “Selective PTT switch Concept - Usability” Based on an evaluated IBM computer usability questionnaire* *J. R. Lewis, “IBM Computer Usability Satisfaction Questionnaires: Psychometric Evaluation and Instructions for Use”, International Journal of Human-Computer Interaction, 1995 v.7 n.1 p.57-78 19 European Organisation for the Safety of Air Navigation
Long Term Investigations, EEC Global Question Usage of the selective PTT switch requires change of the current working procedures for the controller Selection of the called aircraft by hover the label and Pressing the PTT switch Is this change of the working procedures acceptable for the controllers ? 20 European Organisation for the Safety of Air Navigation
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