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 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

ATN Functional Components ES IS

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

Example Administrative Domain BIS Administrative Domain Routing Domain

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

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

Mobile Routing - RGS Level IS RGS Routing Domain

Mobile Routing - RD Level

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

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

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

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)

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

Satellite Data Link Technical 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

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

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

Mode S Data Link Technical 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

Mode S Data Link Conventions Interrogation P1 P2 Data Reply Preamble Data ATC Radar Beacon System (ATCRBS)

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

HF Data Link Technical 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

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

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

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