Enabling technologies

Pierre GAYRAUDTHALES Avionics

ASAS-TN Seminar

Brighton

11-13 October 2004

Content

ASAS

ADS-B

ADS-B Data Links• Mode S Extended Squitter• VDL Mode 4• UAT

TIS-B

On-board Sensors, Processing & Display

ASAS Enabling technologies

ASAS DisplayADS-B

ADS-B receiver ground station

TIS-B

Aircraft Sensors

ASASFunctional description

On-board systems and data sources(FMS, GPS, pilot

interface)

Airborne data processing, Display

Applications processing

ACAS

Aircraft N

ADS-B out

ADS-B in

On-board systems and data sources(FMS, GPS, pilot

interface)

Airborne data processing, Display

Applications processing

ACAS

Aircraft A

ADS-B out

ADS-B inNavigation information - any source including

GPS

Ground vehicle

ADS-B out

Ground systemsGround ADS-B

receiverATC

surveillance

Controller Working Position

ADS-B Definition

• ADS-B: « Automatic Dependent Surveillance – Broadcast »« A function on an aircraft or surface vehicle that broadcasts position, altitude, vector and other information for use by other aircraft, vehicles and by ground facilities » (Draft ICAO ASAS Circular)

• The broadcast is independent of any external stimuli• The originating aircraft does not know who receives and

uses its broadcast• Users: surrounding aircraft/vehicle and/or ATC• Three candidate data link technologies

– Secondary surveillance radar (SSR) Mode S Extended Squitter (SSR Mode S ES)

– VHF digital link Mode 4 (VDL Mode 4)– Universal Access Transceiver (UAT)

ADS-B Message content

• Data transmit by ADS-B generically defined by RTCA ADS-B MASPS DO-242A – Horizontal position and related data

– Lat/Long, Horizontal velocity, Ground speed, Heading on surface– Integrity (Navigation Integrity Category, Surveillance Integrity Level )– Optional: Airspeed, Heading while airborne

– Altitude and related data– Barometric altitude, Geometric altitude, Vertical rate, NIC baro

– Status – ICAO address, Call sign, Emitter category, Length and width– Emergency/priority, Capability class codes

– Target State: Target altitude and HDG/TRK– Trajectory Change (Under review)

• Arrangement within one or several transmissions according to the data link technology

ADS-BICAO data link policy

• Air Navigation Conference (2003) Recommendations • Strategy for the near-term

– ICAO encourages the selection of the SSR Mode S Extended Squitter as the initial data link

– Regional implementations• Europe: VDL Mode 4• US: UAT

• In the longer term– The current SSR Mode S extended squitter technology may

not be able to fully satisfy all of the requirements for ADS-B services in all airspaces

– Continue to develop standards for ADS-B link technologies, including VDL Mode 4 and UAT

SSR Mode S ESMain characteristics (1)

• On 1090 MHz channel – Secondary Surveillance radar (SSR) Mode A and C– Aircraft SSR Mode S responses to interrogations from

ground-based radars• Aircraft answers to ACAS interrogations including

transmission of non-solicited answers • ADS-B SSR Mode S Extended Squitters

• Based on (except Modes A and C)– Multiple Access: pseudo random timing of the

transmissions – Pulses modulated at 1 MHz able to convey 56 or 112-bit

messages– Downlink and Uplink predefined formats

SSR Mode S ESMain characteristics (2)

• Squitters– Aircraft broadcast non-solicited long squitters (112 bits)– Data to be transmit are prepared in « registers »– Different types of SSR Mode S Extended Squitters

• Airborne/Surface Position Squitter Content of registers 05/06 (rate: 0.5 s)

• Airborne Velocity Squitter: register 09 rate: 0.5 sAircraft Identification Squitter: register 08

• Event-Driven Squitter: register 0A

=> Several Squitters are necessary to transmit data

SSR Mode S ESStandardisation status

• ICAO SARPS: Annex 10 Vol III Ch 5 and Vol 4– The current standard is Amdt 77 – Plans to modify the content of some registers in order to

improve the characterisation of the safety level

• RTCA MOPS – DO-260: Minimum Operational Performance Standards

for 1090 MHz ADS-B– DO-260A: with proposed improvements on safety level

characterisation

SSR Mode S ESTransmitters

• On-board current Transponders– Mode S transponders transmit on 1090 MHz aircraft SSR

Mode S responses to interrogations from ground-based radars

– They are installed on most aircraft (mandatory on all IFR aircraft in Europe as of 31/03/2005)

• Evolution towards ADS-B Out Transmitters– Transmission of Extended Squitters is part of the

standard (provided Registers are loaded by the avionics)

SSR Mode S ESOn-board Receivers

• Current TCAS– The TCAS box includes a 1090 MHz reception function of

• answers of surrounding aircraft to ACAS interrogations• short squitters

• Evolution towards ADS-B receiver– SSR Mode S Extended Squitters can be received and

extracted by TCAS– Independency between TCAS and SSR Mode S

Extended Squitters reception is required: no common failure

VDL Mode 4 Main characteristics

• Frequency Band : 108-137 MHz (i.e. Nav and Comm bands)• Bandwidth : 25 KHz per channel• Time Division Multiple Access, self organised by the mean

of a common clock available to all users : UTC time (GPS)VDL4 user terminal checks available slots and make reservations in subsequent frames for transmission

• The VDL Mode 4 protocol allows to manage several VHF channels– 2 Global Signalling Channels (GSC) – Regional and Local Signalling Channels (LSC) for additional services

as required

• 4500 slots/minute• Bit rate : 19,200 bits/s

VDL Mode 4Standardisation Status

• ICAO SARPS: Annex 10 Vol III Ch 6.9+ Manual on VHF Digital Link (VDL) Mode 4

• Airborne MOPS: ED-108A in preparation• Ground: on-going ETSI standardisation

UAT Main characteristics

• Designed specifically for ADS-B with no constraints from legacy systems

• Single common wideband channel 2-3MHz 1 Mbps channel rate in 960-1215 MHz (ARNS band)

• Aircraft access the channel autonomously at random

• Transmission rate: 1/sec.

UAT Status

• Standardisation status– Frequency allocation: need to be co-ordinated on a world-

wide basis – SARPs not yet available– MOPS available (DO-282)

• Product status– UAT part of SafeFlight-21 Link Evaluation study– UAT selected by FAA Alaska Region (100-200

installations in Western Alaska)

TIS-BDefinition

• TIS-B« A service provided by ground stations, broadcasting information relating to aircraft based on surveillance carried out by ground systems, using ADS-B signals, formats and protocols, compatible with ADS-B receiving equipment » (Draft ICAO ASAS Circular)

• Data link technologies identical to ADS-B• Depends on a ground surveillance infrastructure

– e.g. SSR, PSR, ADS-B, multilateration, ASDE

• Users: surrounding Aircraft/Vehicle

TIS-B Role & Status

• Role– Provides aircraft with a complete picture of the traffic– Exact role to be defined (ADS-B gap filler, ADS-B data

validation, Bridge between different ADS-B data link technologies, Primary source for some ASAS applications?)

• Status– Elements in ICAO SARPS for SSR Mode S Extended

Squitters and VDL Mode 4 technologies– Complete SARPS to be developed– RTCA MASPS DO-280

On-boardSensors

• ADS-B requires on-board availability of– Aircraft position

• May be based on GPS or FMS multisensor position• Available on all RNAV capable aircraft• Integrity data from GPS (more difficult with FMS)

– Altitude and related data– Barometric altitude: always available

– Geometric altitude: if GPS

– Status• Ident: ICAO address and Call sign may require specific Control

Panel

On-boardProcessingSurveillance layer Applications layerData Link layer

Display

SurveillanceData

Processing

Own positionOther Systems (FMS, MCDU…)

ASAS tracks

ASAS tracks,Selected target, Guidance data

Display Management

ASAS Applications

TA/RAACAS tracksTA/RA

ACAS tracks

CAS LogicACAS Surveillance

Act

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UA

T /

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DL

M4

Rec

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ADS-BTIS-B

109

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Rec

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On-boardDisplay

• Cockpit Display of Traffic Information (CDTI)– Example of Navigation (FMS), TCAS and ASAS sharing

the same display