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ATN Air-Ground Subnetworks

ATN Air-Ground Subnetworks. Presentation ATN2.2 by R. Oishi, ARINC CAO Regional ATN Seminar 6-7 May 2002. End Systems - Intermediate Systems. End System (ES) Computer system which executes end-user application programs May implement 7-layer stack as required

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ATN Air-Ground Subnetworks

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  1. ATNAir-Ground Subnetworks Presentation ATN2.2 by R. Oishi, ARINC CAO Regional ATN Seminar 6-7 May 2002

  2. End Systems - Intermediate Systems • End System (ES) • Computer system which executes end-user application programs • May implement 7-layer stack as required • Communicates to Intermediate Systems or possibly to other ESs • Intermediate System (IS) • Computer system which relays and routes NPDUs to other ISs or ESs • Implements up to Network Layer (Layer 3) • Implements CMIP and routing protocols

  3. ES ES ES IS IS IS IS IS IS ES ES ATN Functional Components

  4. Administrative and Routing Domains • Administrative Domain • A set of ESs, ISs, and subnetworks operated by a single organization or administrative authority • Routing Domain • A set of ESs and ISs bound by a common routing procedure • An Administrative Domain may contain one or more Routing Domains • A Routing Domain is always wholly contained within one Administrative Domain • There are smaller and larger area definitions to facilitate operation of a worldwide ATN

  5. Administrative Domain Routing Domain Routing Domain BIS BIS Example Administrative Domain

  6. Routing Protocols ISO 9542 ES-IS Host/Router Protocol(Optional) • Exchanges connectivity information within a local subnetwork environment ISO/IEC 10589 IS-IS Intra-Domain Protocol (Optional) • Exchanges connectivity and topology information among ATN routers (ISs) within a Routing Domain • Supports dynamic configuration of ATN routing tables on a domain-wide basis ISO/IEC 10747 IDRP Inter-Domain Routing Protocol • Exchanges routing information across routing domain boundaries • This is the ATN key element in maintaining communication with aircraft

  7. Protocols in Context ES IS BIS IDRP (ISO/IEC 10747) IS-IS (ISO 10589) ES-IS (ISO 9542) COTP Class 4 (ISO 8073) CLNP (ISO 8473)

  8. RGS RGS RGS RGS IS IS IS IS Mobile Routing - RGS Level Routing Domain

  9. Mobile Routing - RD Level RD 1 RD 2 RD 3 RD 4

  10. Air/Ground Subnetworks • VHF Digital Link (VDL) • Satellite • Mode S • HF Data Link

  11. VHF Digital Link (VDL)General Characteristic • Very High Frequency radio (118-137 MHz) • SARPs complete/validated for Modes 2-3 • Line-of-sight from remote ground station (RGS), coverage up to 200 NM depending on terrain, aircraft altitude, other factors • Three operational Modes of VDL • Mode 2 - Data only • Mode 3 - Data and voice • Mode 4 - Data only

  12. Simultaneous Voice & Data Data Only Data Only Analog Voice Analog Voice Analog Voice Analog Voice CSMA STDMA TDMA DSB AM DSB AM DSB AM DSB AM GFSK D8PSK D8PSK 8.33 8.33 8.33 25kHz 25kHz 25kHz 25kHz 25kHz Voice Channels MODE 4 MODE 2 MODE 3 VHF Usage

  13. VDL Technical Characteristics • Modulation: • Modes 2,3 Differential 8-Phase Shift Keying (D8PSK), 31.5 KBPS • Mode 4 Gaussian Frequency Shift Keying (GFSK), 19.2 KBPS • Medium Access: • Mode 2 - Carrier Sense Multiple Access (CSMA) • Mode 3 - Time Division Multiple Access (TDMA), maximum of 4 channels per frequency • Mode 4 - Self-organizing TDMA (STDMA)

  14. Satellite Data Link • Uses Inmarsat geosynchronous satellites which provide both telephone and data services, operating in L-Band (1550-1630.5 MHz) • SARPs approved • Worldwide coverage with 4 satellites, except polar areas • Four channel types: • P-Channel - ground-to-air signaling and user data • R-Channel - air-to-ground requests or data • C-Channel - both directions, voice or data • T-Channel - air-to-ground user data

  15. Satellite Data LinkTechnical Characteristics • Modulation: • Binary Phase Shift Keying (BPSK), 1200 or 2400 BPS • Quadrature Phase Shift Keying (QPSK), 4.8 or 10.5 KBPS • Medium Access: • P-Channel - TDMA • R-Channel - slotted Aloha • C-Channel - Single Channel per Carrier (SCPC) • T-Channel - TDMA

  16. Satellite Data Link Conventions Outbound Link Forward Link Uplink Return Link Downlink Inbound Link

  17. Mode S Data Link • Uses Secondary Surveillance Radar (SSR) transponder to transmit data (1090 MHz) and receive data (1030 MHz) • ICAO SARPs approved • Coverage with data linked SSRs or stationary antennas • Shares transponder with Traffic Alert and Collision Avoidance System (TCAS)/Airborne Collision Avoidance System (ACAS) and SSR functions

  18. Mode S Data LinkTechnical Characteristics • Modulation: • Pulse modulation, identifies Mode S from ATCRBS • DPSK, 4 MBPS for Mode S interrogation • Pulse Position Modulation (PPM), 1 MBPS for reply • Medium Access: • Random access, pulse modulation identifies Mode • Mode S timed to occur within ATCRBS suppression • Mode S reply by PPM allows reply to get through in face of a single ATCRBS interferencing signal • Other characteristics: • Data transferred in 56 or 112 bits of information • 24-bit parity error check

  19. Mode S Data LinkConventions Interrogation P1 P2 Data Reply Preamble Data ATC Radar Beacon System (ATCRBS)

  20. HF Data Link • Long-range coverage (3000 km) in aeronautical high frequency (HF) band (3-22 MHz) • ICAO SARPs complete • Multiple data rates (300, 600, 1200, 1800 BPS) • Frequency Division Multiple Access (FDMA) to maximize coverage; TDMA to organize data transmission

  21. HF Data LinkTechnical Characteristics • Modulation: M-ary PSK (2PSK, 4PSK, 8PSK) • Data Rates: 300, 600, 1200, 1800 BPS • Medium Access: TDMA, 32 second frame, 13 slots/frame, 1 MPDU/slot • Other characteristics: • Aircraft login to ground station • Ground station squitters transmitted • GPS synchronized ground stations • Frequencies coordinated between ground stations

  22. HF Data Link Frame Structure HFDL Frame (32 sec, 2700/day) Slot (13/frame) MPDU (1/slot) Message Protocol Data Unit (MPDU) Prekey Preamble Data

  23. HF Data Link • Service for ATC and AOC applications • 12-16 sites sharing 60 frequencies will eventually provide worldwide coverage • Data link coverage in polar regions • Multiple frequencies per site, multiple sites per aircraft

  24. Summary • ATN SARPs include the following air/ground subnetworks: • VHF digital link (VDL) • satellite link (satcom) • Mode S data link • HF data link (HFDL) • VDL Mode 2 will be the first operational ATC link

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