1. ATN Air-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. ATN Functional ComponentsES IS

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. Example Administrative Domain
BIS
Administrative Domain
Routing Domain

6. Routing Protocols ISO 9542 ES-IS Host/Router Protocol (Optional)
Exchanges connectivity information within a local subnetwork environment
ISO/IEC 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 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 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)

8. Mobile Routing - RGS LevelIS
RGS
Routing Domain

9. Mobile Routing - RD Level

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 ( 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
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

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 ( 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 Link Technical Characteristics
Modulation:
Binary Phase Shift Keying (BPSK), 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 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

19. Mode S Data Link Conventions
Interrogation
P1 P 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 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

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