Introduction to Aeronautical Data Links Prepared by - Loftur Jónasson & Jennie Jónasson Iceland Telecom Seminar on the Implementation of Data Link and.

Introduction to Aeronautical Data Links

Prepared by -

Loftur Jónasson & Jennie Jónasson

Iceland Telecom

Seminar on the Implementation of Data Link and Satcom Communications

Bangkok, Thailand, 17-19 November 2003

IntroductionThis presentation is intended to be a basic introduction to Air/Ground datalinks, based on the work done in ACP (formerly AMCP) WG-M, as well as our operations experience with Iceland Radio in the North Atlantic, where FANS-1/A is currently being utilised.

This introduction highlights aspects on the following topics:

FANS 1A –ACARS and ATN messages

The use of ATN compatible data links:

SATCOM (also called AMSS)

HF data link (HFDL)

VHF Digital Links: VDL Mode 2 VDL Mode 3 VDL Mode 4

The authors of this presentation have borrowed the work of many others in the aviation industry for this presentation. The authors would like to take this time to thank ARINC, SITA, the FAA, the Swedish CAA, Nav Canada, UK NATS and many others. The authors would like to thank them all for their contributions.

Free Flight - the end goal

From the US FAA´s Architecture - Version 4.0, Section 6 Free Flight Phase 1, Safe Flight 21, and Capstone -

“Free Flight will allow pilots to change routes, speeds, or altitudes as needed, while in en route and oceanic air space. Air Traffic Controllers will not impose restrictions on pilot-initiated changes, except when there is a potential conflict with other aircraft or special use airspace. This capability will allow pilots to fly optimized profiles , the most efficient cruise speeds, wind-aided routes, and arrival descent profiles. Any activity that removes operational restrictions is a move towards Free Flight.”

ATN and FANS 1/A

AirborneApplication

(CNS/ATM-1)

Protocol(ATN)

Bit-OrientedSubnetworks

(VDL,Satcom Data 3)

ATC Automation

Protocol(ATN)

Protocol(622)

Character-OrientedSubnetworks

(ACARS; VHF,Satcom Data 2)

ATN Stack

Protocol(622)

Communications SelectionAPI

ACARS Aircraft ATN Aircraft .

AirborneApplication(FANS-1)

FANS 1/A(622) Stack

ADS CPDLC CMA.

.Gateway

.AFN

ARINC´s Explanation of Difference Between a FANS-1/A ACARS Message and an ATN Message

ACARSMU

SAT

VHF

BIT-APPLN.

622

CHAR.APPLN.

F A N S 1

• A F N• A D S• C P D L C

A TN C M UR o u ter

S A TB IT -A P P L N .

C H A R .A P P L N .

• C M A• A D S• C P D L C• P D C• A T I S

M o de S

VD L

CLIMB TO AND MAINTAIN F330, REPORT LEVEL F330

1000 0100 0001 0100 1100 1001 0110 0100 0000 1110 0100 1011 0000

1000 0100 0001 0100 1100 1001 0110 0100 0000 1110 0100 1011 0000

Same Message Bits

FANS 1/ACARS Aircraft ATN Aircraft

622 Protocol(Bit-to-hex, CRC)

AT O8414C9640E4B0 CRC

AT O8414C9640E4B0 CRC1000 0100 0001 0100 1100 10 1 0110

0100 0000 1110 0100 1011 0000

ACARS ProtocolATN Protocol

0

Character- vs. Bit-Oriented Messages Protocol Data Units (PDU)

PDU n

PDU m

8-bit ASCII character

Arbitrary sized bit fields

Character-oriented protocol

Bit-oriented protocol

Transition of FANS 1/A (ACARS) to ATN

ACARSMU

SAT

VHF

BIT-APPLN. 622

CHAR.APPLN.

ACARSMU

SAT

VHFCHAR.APPLN.

• OOOI• PDC• ATIS• OCD

Step 1 - ACARS Step 2 - ACARS/622 Step 3 - VDL Step 4 - ATN

• OOOI• PDC• ATIS• OCD

FANS 1

• AFN• ADS• CPDLC

VDLCMU

SAT

VDL

BIT-APPLN.

CHAR.APPLN.

• OOOI• PDC• ATIS• OCD

• AFN• ADS• CPDLC

ATN CMURouter

SATBIT-APPLN.

CHAR.APPLN.

• OOOI

• CMA• ADS• CPDLC• PDC• ATIS

Mode S

ACARS

ADNSCHAR.AOC

• OOOI

CHAR.

• PDC• ATIS• OCD

CHAR.

ACARS

ADNSCHAR.AOC

• OOOI

CHAR.

• PDC• ATIS• OCD

CHAR.

622

BIT

• AFN• ADS• CPDLC

VDL

APNCHAR.AOC

• OOOI

CHAR.

BIT

BIT

• AFN• ADS• CPDLC

• PDC• ATIS• OCD

VDL

APN

BIT

Mode S

NADIN

ATN

CHAR.AOC

• OOOI

BITAOC

BIT

CMAPDCATISOCDADSCPDLCTFM

BIT

CHAR.

VDL

Transition from FANS 1/A to ATN using VDL Mode 2

Step 1: ACARS Step 2a: Character Applications over VDL

Step 2b: VDL Step 3: VDL/ATN

ICAO data link systems that can be used during flight

Departure En Route Approach Land Taxi

Taxi Take-Off

VDL 2, 3, 4

VD

L 2

, 3, 4

VDL 2, 3, 4 Within l.o.s.

VDL 2, 3, 4

Outside l.o.s.

SATCOM

HFDL

VDL 2, 3, 4

VD

L 2

, 3, 4 VDL 2, 3, 4

l.o.s. : line of sight

Departure En Route Approach Land Taxi

Taxi Take-Off

From Aircraft

Link Test/Clock Update

Fuel/Crew Information

Delay Reports

Out

To Aircraft

PDC

ATIS

Weight and Balance

Airport Analysis

V-Speeds

Flight Plan-Hard Copy

Load FMC

From Aircraft

Off

From Aircraft

Engine Start

To Aircraft

Flight Plan Update

Weather Reports

From Aircraft

Position Reports

Weather Reports

Delay Info/ETA

Voice Request

Engine Information

Maintenance Reports

To Aircraft

ATC Oceanic Clearances

Weather Reports

Reclearance

Ground Voice Request

(SELCAL)

From Aircraft

Provisioning

Gate Requests

Estimate Time-of-Arrival

Special Requests

Engine Information

Maintenance Reports

To Aircraft

Gate Assignment

Connecting Gates

Passengers and Crew

ATIS

From Aircraft

On

From Aircraft

In

Fuel Information

Crew Information

Fault Data from Central Maintenance Computer

Different types of data link messages as a flight progresses

Overview of the VDL Modes

Name VDL Mode-2 VDL Mode-3 VDL Mode-4

Access method CSMACarrier Sense Multiple Access

TDMATime Division Multiple Access

STDMASelf-Organising Time Division Multiple Access

Capability Data Only Data and Voice simultaneously

Data Only

Modulation D8PSK D8PSK GFSK

Channel band-width

25 kHz 25 kHz 25 kHz

The VDL ModesThe numbers mean what order they entered ICAO for

standardising – they are not in succession

VDL Mode-1

Taken out of Annex 10 before ever implemented

– no longer exists

VDL Mode-2

Data Only

Successor to ACARS

25 kHz

VDL Mode-3

Voice & Data together

US FAA Program

25 kHz

VDL Mode-4

Data Only

Primary purpose is ADS-B

Swedish design

25 kHz

The VDL Modes and 25 kHz/8.33 kHz voice systems

MODE 2 MODE 3Voice Channels MODE 4

25kHz 25kHz 25kHz 25kHz 25kHz

MODE 2 MODE 3Voice Channels MODE 4

DSB AMDSB AM D8PSK D8PSK

DSB AM

DSB AM GFSK

TDMACSMA STDMA

Ana

log

Voi

ceA

nalo

g V

oice

Ana

log

Voi

ceAnalog Voice

Data Only(ATN A/G)

Simultaneous Voice &

Data(4 channels

voice or ATN A/G data)

Data Only(ATN A/G

and ADS-B)

DSB AMDSB AM D8PSK D8PSK

DSB AM

DSB AM GFSK

TDMACSMA STDMA

8.33 8.338.33

Long range data link systems Propagation Paths of SATCOM and HFDL

GES

IONOSPHERE

SCINTILLATION“CLOUD”

HF

SATCOM

HFDL GS

Propagation problemsaffecting HF and SATCOM

are fairly independent

(Satellite)

GS=Ground station

GES=Ground Earth Station

Jónhvolf in Icelandic

HFDL(HF Data Link)

• HFDL - High Frequency Data Link• With ground stations around the world• Iceland Radio houses one of the

Ground Stations• Can accommodate ACARS or ATN• Developed to be used in areas where

satellite cannot be used• Cheaper alternative to SATCOM

SATCOM(AMSS)

• Satellite Communications• A system available for ACARS and for

ATN• Satellites can be used for Data Link and

for voice - often referred to as SAT Voice

• Inmarsat is the current provider for aeronautical communications 1

ADS-CAutomatic Dependent Surveillance-Contract

• The C stands for contract. An ADS-C message is only sent after a link “contract” between the aircraft and the ground has been established.

• ADS-C is currently used using SATCOM or HF data link.

ADS-BAutomatic Dependent Surveillance-Broadcast

ADS-B is a broadcast of the aircraft’s position, mainly derived from the GNSS system. It provides the pilot of a properly equipped aircraft a display on his instrument panel of where other aircraft are in relation to his aircraft.

ADS-Broadcast Concept

Situational Display

Situational Display

Situational Display

Aircraft emits signal

Aircraft 1

Aircraft 3

ATC Surveillance

When Aircraft 1 sends a signal, Aircraft 2 and Aircraft 3 and ATC can see Aircraft 1 on their displays. In an ADS-B environment all aircraft will be “broadcasting” signals to other aircraft and the ground.

Mode-S Extended Squitter

• Mode-S was standardised by ICAO several years ago

• The ICAO 11th Air Navigation Conference has decided that all ADS-B implementations should support the use of Mode-S squitter

ICAO Communications/Navigations Surveillance (CNS) Environment

Air Traffic Management Centre

Satellite Ground Earth Station VHF Voice and Data

Mode-S – Secondary Surveillance Radar

Radar would be surveillance

Using satellites to determine your location would be navigation

Using satellites or VHF to talk with airplanes is Communication

What is the ATN?

• “The ATN concept emerged from a need to interchange bit-oriented digital data over dissimilar aeronautical data links, using, for interoperability purpose, the principles of the International Organization for Standardization (ISO) open systems interconnection (OSI) architecture.”

Describe the ATN

• “The ATN design supports the incorporation of different air-ground subnetworks and different ground-ground subnetworks, resulting in a common data transfer service. Furthermore, the ATN design is such that user communication services may be introduced in an evolutionary manner”

OSI 7 Layer Protocol Reference Model

System A System B

Layer 7

Application

Layer 6

Presentation

Layer 5

Session

Layer 4

Transport

Layer 3

Network

Layer 2

Data Link

Layer 1

Physical

Layer 7

Application

Layer 6

Presentation

Layer 5

Session

Layer 4

Transport

Layer 3

Network

Layer 2

Data Link

Layer 1

Physical

First CPDLC Message in Miami area