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Introduction to Aeronautical Data Links

Introduction to Aeronautical Data Links. Introduction. This presentation is intended to be a basic introduction to Air/Ground datalinks This introduction highlights aspects on the following topics : FANS 1A –ACARS and ATN messages The use of ATN compatible data links:

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Introduction to Aeronautical Data Links

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  1. Introduction to Aeronautical Data Links

  2. Introduction This presentation is intended to be a basic introduction to Air/Ground datalinks 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

  3. 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.”

  4. ATN and FANS 1/A

  5. C L I M B T O A N D M A I N T A I N F 3 3 0 , R E P O R T L E V E L F 3 3 0 F A N S 1 / A C A R S A i r c r a f t A T N A i r c r a f t • A F N • C M A • A D S • A D S • C P D L C • C P D L C • P D C • A T I S F A N S 1 B I T - B I T - S A T S A T A C A R S A T N C M U 6 2 2 A P P L N . A P P L N . R o u t e r M U V H F M o d e S S a m e M e s s a g e B i t s C H A R . C H A R . V D L A P P L N . A P P L N . 1 0 0 0 0 1 0 0 0 0 0 1 0 1 0 0 1 1 0 0 1 0 0 1 0 1 1 0 1 0 0 0 0 1 0 0 0 0 0 1 0 1 0 0 1 1 0 0 1 0 0 1 0 1 1 0 0 1 0 0 0 0 0 0 1 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 1 0 0 0 0 0 0 1 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 6 ARINC´s Explanation of Difference Between a FANS-1/A ACARS Message and an ATN Message 2 2 P r o t o c o l ( B i t - t o - h e x , C R C ) O 8 4 1 4 C 9 6 4 0 E 4 B 0 A T C R C 0 0 1 0 0 0 0 1 0 0 0 0 0 1 0 1 0 0 1 1 0 0 1 1 0 1 1 0 O 8 4 1 4 C 9 6 4 0 E 4 B 0 A T C R C 0 1 0 0 0 0 0 0 1 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 A C A R S P r o t o c o l A T N P r o t o c o l

  6. Character- vs. Bit-Oriented Messages Protocol Data Units (PDU) • Character-oriented protocol • Bit-oriented protocol PDU n 8-bit ASCII character PDU m Arbitrary sized bit fields

  7. Transition of FANS 1/A (ACARS) to ATN

  8. 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

  9. ICAO data link systems that can be used during flight T a x i D e p a r t u r e E n R o u t e A p p r o a c h L a n d T a x i T a k e - O f f Within l.o.s. VDL 2, 3, 4 Outside l.o.s. SATCOM HFDL VDL 2, 3, 4 VDL 2, 3, 4 VDL 2, 3, 4 VDL 2, 3, 4 VDL 2, 3, 4 VDL 2, 3, 4 l.o.s. : line of sight

  10. Different types of data link messages as a flight progresses T a x i D e p a r t u r e E n R o u t e A p p r o a c h L a n d T a x i T a k e - O f f 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 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 Off From Aircraft Engine Start To Aircraft Flight Plan Update Weather Reports From Aircraft On From Aircraft In Fuel Information Crew Information Fault Data from Central Maintenance Computer

  11. Overview of the VDL Modes

  12. The VDL Modes The 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

  13. The VDL Modes and 25 kHz/8.33 kHz voice systems Simultaneous Voice & Data (4 channels voice or ATN A/G data) Data Only (ATN A/G and ADS-B) Data Only (ATN A/G) AnalogVoice Analog Voice Analog Voice Analog Voice CSMA CSMA STDMA STDMA TDMA TDMA DSB AM DSB AM DSB AM DSB AM DSB AM DSB AM GFSK GFSK D8PSK D8PSK D8PSK D8PSK DSB AM DSB AM 8.33 8.33 8.33 25kHz 25kHz 25kHz 25kHz 25kHz Voice Channels MODE 4 Voice Channels MODE 2 MODE 3 MODE 4 MODE 2 MODE 3

  14. Long range data link systems Propagation Paths of SATCOM and HFDL (Satellite) SCINTILLATION “CLOUD” Jónhvolf in Icelandic IONOSPHERE HF SATCOM Propagation problems affecting HF and SATCOM are fairly independent HFDL GS GES GS=Ground station GES=Ground Earth Station

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. Situational Display Aircraft 1 Situational Display Aircraft emits signal Aircraft 3 Situational Display 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. ATC Surveillance ADS-Broadcast Concept

  20. 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

  21. Using satellites to determine your location would be navigation Using satellites or VHF to talk with airplanes is Communication Radar would be surveillance Air Traffic Management Centre Satellite Ground Earth Station Mode-S – Secondary Surveillance Radar VHF Voice and Data ICAO Communications/Navigations Surveillance (CNS) Environment

  22. 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.”

  23. 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”

  24. OSI 7 Layer Protocol Reference Model System ASystem B

  25. First CPDLC Message in Miami area

  26. Aviation Wireless Communications

  27. Agenda Today's Aeronautical Telecommunication Network (ATN) Potential of TCP/IP Architecture for Aviation Mobility Management Requirements Summary Discussion

  28. Wireless Application Categories (Voice and Data) Air Traffic Management (ATM) Air Traffic Control (ATC) Air Traffic Services (ATS) Communication, Navigation, & Surveillance (CNS) Airline Operational Communications (AOC) Flight Operations Maintenance Airport/Ramp Operations Airline Administrative Communications (AAC) Airline Passenger Communications (APC) Entertainment

  29. Global Customers of the Wireless Aviation Market SizeIndication Type 15,000 Aircraft plus ( times # of passengers) CommercialAviation Business Aviation 25,000 Aircraft plus General Aviation 100,000 Aircraft plus Cargo Aviation 10,000 Aircraft plus 50,000 Aircraft plus Military 184 Countries of ICAO Government

  30. Aeronautical Telecommunication (ATN) Network Environment Management Processor Data Display Processor Data Entry Processor Management Processor ATN End System ATN End System ATN End System ATN End System Avionics Subnetwork VHF Subnetwork Satellite Subnetwork Mode S Subnetwork HF Subnetwork CAA Ground Subnetwork ATN End System ATN End System ATN End System ATN End System ATN End System ATN End System Aeronautical Operations Data Base Aeronautical Operations Control Weather Data Base ATC FIS Data Base Weather Data Base ATN ROUTER ATN ROUTER ATN ROUTER Service Provider Ground Subnetwork Airline Ground Subnetwork

  31. Evolution of Aviation Wireless Communications SATS VDL Mode 4 NEXCOM VDL Mode 3 CPDLC II & III CPDLC I&IA PETAL II & LINK 2000 VDL Mode 2 HF Data Link GPS SATCOM (ATS,AOC,APC) EACARS & AVPAC Attempts ATN - ISO Definition ATN - IPv? Definition Passenger Telephone Systems CNS/ATM - FANS 1&A FANS Committee ACARS PanAm Satcom Demo 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025+

  32. ATN Architecture Consists of Applications and communication services that allow ground, air-ground, and avionics sub-networks to inter-operate • Context Management (CM) Application • Automatic Dependent Surveillance (ADS) • Controller Pilot Data Link Communication (CPDLC) • Flight Information Service (FIS) • ATS Message Handling Services (ATSMHS) End System(ES) End System(ES) Application Entity Application Entity Upper Layer Communications Service Upper Layer Communications Service Internet Communications Service Internet Communications Service Intermediate System (IS) Intermediate System (IS) Subnetwork Subnetwork Subnetwork

  33. Aeronautical Communication Requirements Interoperability with existing subnetworks High availability Mobile Communication Message prioritization Policy based routing Security Bit Efficiency Support for multiple mobile subnetworks Mobile platform forms its own Routing domain

  34. Today’s ATN Status ICAO - 91 Nations Agreement 1991 Published Standards - SARPS Edition 3, end of 2000 Several Cooperative Attempts - Stalled Out FAA Funded Router Development - ATNS,Inc. Limited ATN Router Availability End System Applications under development Wireless Components not yet “Red Label” European, Eurocontrol lead early trials ongoing FAA CPDLC I - Initial Operation 2002

  35. ATN Protocol Architecture Air-Ground ISO Application Application Application Service Element (ASE) Control Function (CF) Application Layer ASE Dialog Service (DS) DS Association Control Service Element (ACSE) ACSE CF Connection Oriented Presentation Protocol (COPP) Fast Byte COPP and COSP Connection Oriented Session Protocol (COSP) Transport Layer (TP4) Transport Layer (TP4) Network Layer (CLNP) Network Layer (CLNP) Sub Networks Air-Ground Subnetwork Ground-Ground Subnetwork Ground-Ground Subnetwork Air-Ground Subnetwork Fast Byte approach selected to obtain bit efficiency over the Air-Ground Link

  36. ATN and TCP/IP Protocol Architecture TCP/IP Architecture ATN Architecture Application ASE DS Application ACSE CF Fast Byte COPP and COSP Transport Layer (TCP) Transport Layer (TP4) Network Layer (IP) Network Layer (CLNP) Ground-Ground Subnetwork Air-Ground Subnetwork Ground-Ground Subnetwork Air-Ground Subnetwork With the Fast Byte enhancements, the two architectures appear similar in structure

  37. TCP and TP4 Features Comparison Function TCP Protocol TP4 Protocol Datatransfer Streams Blocks Flow control Octets Segments Error detection Checksum Checksum Error correction Retransmission Retransmission Addressing 16 bit ports Variable TSAP address Interrupt service Urgent data Expedited data Security Supported Variable in TP Precedence Supported 16 bits in TP Connection termination Graceful Non graceful Both support Connection-oriented and Connectionless Transport services Source: Aeronautical Related Applications Using ATN and TCP/IP Research Report, prepared by CNS for the NASA Glenn Research Center, November 23, 1999

  38. IP and CLNP Features Comparison Function CLNP IP VersionID 1 octet 4 bits Headerlength 1 octet, represented in octets 4 bits, represented in 32 bit words Quality of service QoS maintenance option Type of Service (Class) Segment/fragment 16 bits, in octets 16 bits, in octets length Total length 16 bits, in octets 16 bits, in octets Data unit ID 16 bits 16 bits Flags Don’t segment, more segments Don’t fragment, more fragments Segment/fragment offset 16 bits, represented in octets 13 bits, represented in units of 8 octets Lifetime, time to live 1 octet, represented in 500 millisecond 1 octet, represented in 1-second units units Higher layer protocol Not present Protocol identifier Lifetime control 500 millisecond units 1-second units Addressing Variable length 32-bit fixed (128 bits) Both support Connectionless Network services Source: Aeronautical Related Applications Using ATN and TCP/IP Research Report, prepared by CNS for the NASA Glenn Research Center, November 23, 1999

  39. IP and CLNP Features Comparison Function CLNP IP Options Security Security Priority Precedence bits in TOS · (Class) Complete source Strict source route · routing Partial source Loose source route · · routing Record route Record route · · Padding Padding · · Not present Timestamp · · Reason for discard Uses ICMP messages · · (Error PDU only) Source: Aeronautical Related Applications Using ATN and TCP/IP Research Report, prepared by CNS for the NASA Glenn Research Center, November 23, 1999

  40. Challenge for the Aeronautical World Could TCP/IP protocol meet Aeronautical requirements? Benefits: Lower Infrastructure cost Potential for new services: VoIP Multicast Security Integration with Public Infrastructure Challenges: Modifying Political agreement/ Industry Standards Addressing Technical Issues for: Mobility Management Policy based routing capability

  41. Subnetworks Air-Ground (A/G): Aeronautical Mobile Satellite VHF Data Link Mode S HF Data link Passenger Telephony Ground-Ground: X.25 PSDNs Frame Relay LANs Leased Lines NADIN

  42. Overview of VDL Modes Data Voice Characteristics Mode • Data rate of 1200 bps • Channel shared among all using aircraft • Channel access based Carrier Sense Multiple Access (CSMA) VDL Mode 1 Yes No • Uses the same frequency band as Mode1, but uses better data • encoding modem • Differentially encoded 8-phase shift keying (D8PSK) with channel • data rate of 31.5 kbps • Channel access based Carrier Sense Multiple Access (CSMA) VDL Mode 2 Yes No • Provide 4 logically independent channels in a 25kHz frequency • assignment. • Each channel can be allocated to voice or data. Uses differentially • encoded 8-phase shift keying (D8PSK) at 31.5 kbps • Standard media access control based on 4 slots structure • Extended range uses 3 slot structure Yes VDL Mode 3 Yes • Uses Self-organizing Time division multiplexing (STDMA) • Uses TDMA based short time slots • Uses a reservation protocol to gain link access VDL Mode 4 Yes No

  43. Subnetworks Requirements Byte and code independence Address individual systems Provide error detection Undetected error better than 1 in 108 Packet mode technology Connectionless and Connection mode Prioritization of data Important for safety related data QoS Management Throughput and Transit delay guarantees Mobile subnetworks Ability to report aircraft joining the subnetwork Ability identify aircraft leaving a subnetwork

  44. Mobility and Roaming Mobility between subnetworks while staying in contact Supported by the data link layer ATN must support Roaming between networks Aircraft may move from one mobile subnetwork to another Aircraft may be simultaneously attached to more than one mobile subnetwork

  45. Mobile Routing Issues Routes cannot be aggregated Mobile addresses not related to topology Route changes every time aircraft changes point of attachment High rate of routing updates Routers have to keep a route for each aircraft ATN size limited by router table capacity

  46. ATN Solutions for Mobility Uses Inter Domain Routing Protocol (IDRP) for routing Implements distributed IDRP directory using Boundary Intermediate Systems (BISs) Two level directory ATN Island concept consisting of backbone BISs Home BISs concept Scalability obtained by the two level structure Resilience is provided by the distributed approach

  47. ATN Island Routing Domain Confederation Mobile RD Mobile RD Another ATN Island ATN Backbone RDC ATN TRD ATN TRD Mobile RD ATN TRD ATN ERD ATN ERD ATN Island RDC

  48. Mobile Routing Example RD1, RD2 and RD3 support air/ground data links and RD4 depends on the other three (3) for A/G communication. Using IDRP RD1 and RD2 advertise a route to the aircraft and RD4 can choose one of the route based on Routing policy. RD3 RD1 RD2 RD4

  49. Mobile Routing Example As the aircraft travels it may lose contact RD1, RD1 informs others using the route withdraw message. RD4 now has one path to the aircraft through RD2 and thus routes all traffic through RD2. Further along in the flight, the aircraft may come in contact with RD3. A data link is established and routing information is exchanged. RD3 then advertises a new route to the aircraft. RD4 again has two routes to the aircraft and chooses a route based on local routing policy. The aircraft goes through a similar process to select a route.

  50. ATN Mobile Protocol Requirements Shall support wide variety of mobile communications networks including aeronautical mobile-satellite service (AMSS), VHF digital link (VDL), HF digital link and SSR Mode S. Shall be possible to communicate with airborne avionics in any part of the world. Shall support wide range of Organizational and National polices, including the enforcing of restrictions on what types of traffic can pass over both ground and air/ground data links, and control over which air/ground data link types are used by which applications BISs shall advertise routes to each other, where a route consists of the set of addresses which identifies the destinations reachable over the router, and information about the route's path including the Quality of Service and Security available over the route. Shall support policy based routing that enables users to control external access to their communications resources, and to protect themselves from problems elsewhere in the internetwork. The ATN, mobile “platforms” on board an aircraft shall form a Routing Domain and must include an ATN Router that is also a BIS. Shall support a two level concept of default route providers (ATN Island and Home) for containing high rate of information flow, and also to avoid the problems of routing instability caused by a rapid turnover of routing information. Mobile routing shall supportthe user requirement that the users can specify, on a per application basis, routing control requirements.

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