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Presented by Mike Shorthose

Helios Technology LtdChamberlain House

High StreetBagshotSurrey

UK

VDL Mode 4Overview and development status

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Introduction

• Basic principles• Status of standards• Equipment, trials and assessments• Issues

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What is VDL Mode 4 ?

• VDL Mode 4 is a time-critical digital data link– Operates in 108-137 MHz range using a 25 KHz

communications channel

– Operates without the need for ground infrastructure

– Gaussian-filtered Frequency Shift Keying

– Modulation rate is 19,200 bits/s

• Provides a range of communications services– Main focus is surveillance applications

• Provides built-in ADS-B function• Supports air-to-air surveillance

– Also ATN compliant

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Self-Organising TDMA

• A superframe = 4500 slots/minute• Beginning of each time-slot synchronised to UTC• Slots reserved in advance by all stations• Management of time-slots shared amongst stations• Efficient use of data-link

4 slotsreserved byground station

2 slots reserved by aircraft A

1 slot reserved by aircraft B

VDL Mode 4 time slots

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Channel Operation

Ground Station transmits DoS

En-route traffic transmits on GSCs

LSCs

GS

C A

GS

C B

Terminal traffic transmits on GSCs and LSCs

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Periodic Broadcast Protocol

• Reserves slots in future superframes– All stations build up a ‘reservation table’

– Broadcast of position and ID information

Reserved

Current

Reserved

Reserved

Pt=3

Pt=2

Pt=1

Pt=0

Periodic Broadcast

Reservation

transmitted

Reserved for

broadcast

Reserved for

broadcast

Offset after Time-out & Reserve for

broadcast

Reserved

Reserved for

broadcast

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Introduction

• Basic principles

• Status of standards• Equipment, trials and assessments• Issues

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SARPs

• ICAO standards for VDL Mode 4 cover:– SARPS (physical layer)

– Technical Manual (higher layers)

• Milestones– Accepted by ICAO in early 2000 at AMCP/7

– Reviewed by states – state letters produced

– Expected final acceptance and incorporation in Annex 10 in November 2001

• Expect subsequent update of Technical Manual

Standards And Recommended Practices

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EUROCAE/MOPS

• WG-51: ADS-B: Use of broadcast communication for increased airborne surveillance information

• Set performance standards for VDL Mode 4 airborne transceiver

• “Interim VDL Mode 4 MOPS” – ED108– Published (July 2001)– Will be updated as system develops further– RTCA not publishing these MOPS

European Organisation for Civil Aviation Equipment

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ETSI

• Produces telecommunications standards throughout Europe

• Current activities– Certification of VDL Mode 4 ground

equipment currently being reviewed by RP05 working group

– Physical layer expected to be finalized by July 2001

– Higher layers expected to be finalized by November 2001

European Telecommunications Standards Institute

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Introduction

• Basic principles• Status of standards

• Equipment, trials and assessments• Issues

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Aircraft Architecture• GNSS transponder

• Dual redundant equipment for AT aircraft

Inertial Reference

System

GNSSReceiver

DME/VORNavigationSystems

FlightManagement

Computer

FlightDisplays

VDL Mode 4Communications

unit

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Equipment

• VDL Mode 4 ground and airborne equipment becoming available from several manufacturers

• Mobile display types – The MMI 500 and the NFS 5000

– Active cursor control in NAV display

– Frequency control for VHF link

– Provisions for dedicated VDL Mode 4 transceivers

– Interfaces to VHF link

• Fixed ground displays – RIMS system (fitted with runway incursion monitoring )

– GRPU (display ADS-B and radar data simultaneously )

The MMI 500 display

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Trials Milestones

NEAP

1996 1997 1998 1999 2000

NEAN

NUP Phase I

NAAN

NUP Phase II

NEAN NetworkEstablished

Installations inDLH B747-200

Installations inSAS F28

FARAWAY I/II

FREER III

Airborne ArchitectureGroup Final Report

Discussions with industry

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NEAN & NUP

• NEAN aimed at developing new technologies for data links and networking – WP1 aimed at checking coverage, network reliability

and end-to-end performance– WP3 aimed at development and implementation of the

ground part of the ADS-B network

• NUP– Aims at establishing a European ADS-B network based

on global standards – Phase 2 being planned

North European ADS-B Network & NEAN Upgrade Programme

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MFF & Med-Up

• MFF is conducted by ENAV, the Italian service provider– Determine concept of free flight in Mediterranean

– Defines operational requirements and procedures

– Guidelines to implement free flight operations

– Programme consists of six phases

• Med-up– Contributes to the Eurocontrol ADS work programme

– Provides testing of technical infrastructure

– Large-scale experimentation using several equipped aircraft

Mediterranean Free Flight & ADS Mediterranean Upgrade Programme

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Russian Activities

• Tyumen project – Investigation of ADS-B operation for en-route and

terminal areas

– Support of flights in regions currently without radar surveillance

• Southern Ring Project – VDL Mode 4 equipped flights

– Deployment of ground equipment

• Offshore oil and gas exploration – JV Gasprom considered equipping aircraft with VDL

Mode 4 transponders

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ADS-B Technical Link Assessment Team (TLAT)

• Evaluation of three ADS-B candidate technologies– FAA/Eurocontrol/Service providers/industry

• Results for VDL Mode 4– Aid to visual acquisition – generally not supported– Conflict/collision avoidance – supported beyond 3nm– Separation assurance/sequencing – generally supported– Airport surface – not assessed– Air-to-air applications – not assessed

• Issues for Mode 4– Optimisation of some system functions required

• Channel management/ trajectory change points / ground antenna design

– Identify channel assignments for GSCs / local channels

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• Basic principles• Status of standards• Equipment, trials and assessments

• Issues

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System development

• Further development of surveillance capability– Channel management

• Need to prove concept in high-density environment

– TIS-B / FIS-B

• Evolution of point-to-point functions– To make more efficient for ATN applications

– Re-working of data link service sublayer

– Review of connection to ATN

– Consideration of additional error checking/correction

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Spectrum

• Frequency issues– VDL Mode 4 needs multiple VHF channels

• The exact number is not known• ADS-B (2 GSCs plus local channels)• + channels for other services (TIS, FIS, point to point etc)

• Interference issues– Careful engineering of onboard systems required to

prevent interference between VDL Mode 4 and Mode 2 or with VHF voice R/T

– More trials needed to find optimum configurations