Federal Aviation Administration (FAA) CHANG MAI - ATN SEMINAR CPDLC OVERVIEW December 2001 Federal Aviation Administration (FAA) William J. Hughes Technical l Center (WJHTC) Vic Patel, FAA/ACT-550 ISSP Manager/ATN Technical Lead Page 1
CONCEPTUAL MODEL OF THE ATN 09/00 End System (ES) Application Process ATN End-to to-end End System (ES) Application Process Application Entity ATN Communication Services End-to to-end Application Entity Upper Layer Communications Service ATN Internet Communication Services End-to to-end Upper Layer Communications Service Internet Communications Service Intermediate System (IS) Intermediate System (IS) Internet Communications Service Subnetwork Subnetwork Subnetwork Page 2
Open Systems Layer Structure System A System B Application Presentation Session Transport Network Link Physical Network Link Physical Network Link Physical Application Presentation Session Transport Network Link Physical Page 3
Application Layer System A System B Application Presentation Session Transport Network Link Physical Application Presentation Session Transport Network Link Physical Page 4
ATN FastByte Protocol Stack Application in ASN1 PER Presentation Session Transport Network Link Physical FastByte FastByte Application in ASN1 PER Presentation Session Transport Network Link Physical Page 5
ATN Communications Model Application Transport COTP or CLTP TPDU Header User Data Application Transport Network Header User Data CLNP NPDU Network Router Router Router Subnetwork 1 Subnetwork 2 Subnetwork 3 Subnetwork 4 Page 6
End System Protocol Architecture ATN End System Support Application ASEs CPDLC, CM, ADS, FIS Fast BYTE Session & Presentation Layers CO and CL Transport Layer CL Network Layer ES-IS Routing End System Application ASEs Fast Byte Presentation Session COTP / CLTP CLNP Data Link Physical Subnetwork Page 7
ATN End Systems Protocols Required TP4 (with mandatory checksum support) CLNP Protocols Recommended ES-IS Page 8
TP4 Functions Connection Mode Protocol Ensures end-to to-end Reliable Delivery Provides a Checksum on each Packet Retransmits on Packet Loss or Corruption Provides End-to to-end Flow Control Page 9
Connectionless Network Protocol (CLNP) 81h Len Dest Source Options & User Data Created by Sender Sender sends it and forgets it Interpreted by Routers Delivered to Destination System Page 10
CLNP Functions Simple Datagram Format Message Header Identifies Source and Destination Priority Traffic Type AOC Routing Requirements ATSC Class Page 11
CPDLC CPDLC allows two way communication between pilot and controller, but using data link rather than voice Data Link Page 12
ELEMENTS OF A CPDLC SYSTEM SATCOM LINK EFFECTIVE CONTROL VHF COM LINK GROUND EARTH STATION ATSU Page 13
CPDLC Functions Creation of a dialogue between pilot and controller, ground or air initiated Passing messages selected from ICAO standard list Ability to use free text if required Freedom to communicate with a non-controlling authority for the purposes of getting future clearances Transfer of communication between control authorities by data link, rather than voice Page 14
Compatibility with Voice Phraseology The CPDLC Application must include a set of clearance/information/request message elements which correspond to voice phraseology employed by ATC procedures ICAO CPDLC Message Set ICAO Doc 4444 PANS/RAC Page 15
Compatibility with Voice Operations 09/00 Routine Messages Data link Non-routine Messages Voice Controllers and Pilots will use CPDLC in conjunction with existing voice communications Page 16
CPDLC Messages A CPDLC Message is composed of - a. The Message Header, plus b. Message Element 1, plus (optionally) c. Message Element 2, plus (optionally) d. Message Element 3, plus (optionally) e. Message Element 4, plus (optionally) f. Message Element 5. Page 17
CPDLC Functions Controller-Pilot Message Exchange Function Transfer of Data Authority Function Down Stream Clearance Function Ground Forward Function Page 18
CPDLC Services CPDLC-start service DSC-start service CPDLC-message service CPDLC-end service DSC-end service CPDLC-forward service Page 19
Roger (No Parameters) Sample CPDLC Messages WILCO (No Parameters) Affirm (No Parameters) AT [time] EXPECT CLIMB TO [level] CLEARED [ route clearance] SQUAWK MODE CHARLIE REPORT REMAINING FUEL AND PERSONS ON BOARD Page 20
Normal Data Authority Operations 09/00 CURRENT DATA AUTHORITY NDA CDA Control Connection No Dialogue No Control AIRCRAFT TRACK Connection Dialogue No Control Connection Dialogue Control Data Authority Boundaries NEXT DATA AUTHORITY DDA DOWNSTREAM DATA AUTHORITY Page 21
Current Data Authority Operations 09/00 CDA Control CURRENT DATA AUTHORITY Connection NDA Connection No Dialogue No Control Connection Dialogue Control NEXT DATA AUTHORITY AIRCRAFT TRACK The CDA may - 1. Exercise Control, using full Message Set 2. Nominate Next Data Authority (NDA) 3. Generate transfer of control to NDA Page 22
Next Data Authority Operations 09/00 CURRENT DATA AUTHORITY NDA Connection No Dialogue No Control Nominates NDA NEXT DATA AUTHORITY AIRCRAFT TRACK The NDA may - 1. Initiate a connection with an aircraft 2. Accept a connection from an aircraft only if it has been nominated as NDA by the CDA Page 23
Downstream Data Authority Operations CDA Connection Dialogue Control Control CURRENT DATA AUTHORITY A Downstream Data connection is always Air User initiated. A limited, non tactical message set is used. A downstream link is not affected by normal CDA/NDA actions. NEXT DATA AUTHORITY DDA DOWNSTREAM DATA AUTHORITY Connection Dialogue No Control Page 24
Benefits from use of CPDLC 09/00 To improve SAFETY by - Reducing risk of controller-aircrew misunderstandings Reducing congestion on voice channels Reducing risk of failure in the transfer of information To improve ATM EFFICIENCY by - Increasing controller/aircrew productivity Enabling automation Providing concise and precise exchanges between controller and aircrew Reducing the voice communication workload Page 25