Wednesday, December 6, 2023

Aeronautical Communication - Designations, Divisions, Domains

Aeronautical Communication is characterized in several different ways, which can get confusing. Follow along the avalanche of acronyms.

Radio frequencies are designagted as "Route" or "Off-Route". Broadly, Route refers to communication that factors into the trajectory of the airplane, and is characterized as a safety service. Everything else is non-safety, "Off-Route". 

Aeronautical Mobile Services (AMS) are provided by line-of-sight (LOS) networks such as VHF and beyond-line-of-sight networks (BLOS) such as HF (shortwave). AM(R)S or AMRS are AMS Route communications. AM(OR)S, or AMS, are AMS Off-Route communications.

Aeronautical Mobile Satellite Services (AMSS) are provided by BLOS networks that involve a satellite relay. AMS(R)S or AMSRS are AMSS Route communications. AMS(OR)S or AMSS are AMSS Off-Route Communications.

Air Traffic Services (ATS) includes communication between Air Traffic Facilities and Aircraft (Pilots). ATS includes data link communication such as Controller Pilot Data Link Communication (CPDLC) and Automatic Dependent Surveillance  (ADS-C, contract based). Context Management (CM) provides the secure connection between a particular ATS facility (Air Navigation Service Provider, ANSP) and an aircraft.

CPDLC and ADS-C are performance-based. Required Communication Performance (RCP) is applied to CPDLC. Required Surveillance Performance (RSP) is applied to ADS-C.

Aeronautical/Airline Operational Control, AOC, is broadly the communications between the Pilot/Airplane and the Operating Entity/Airline.  Generally AOC is considered a safety service, but the message set can include non-safety services as well. Operational communication gets to the efficient operation of the operator.

Aeronautical Administrative Communication (AAC) is broadly the communications relating to passenger entertainment, airplane health monitoring and maintenance. 

Aeronautical Passenger/Public Communication (APC) is broadly the communications relating to passenger devices.

Onboard networks are subdivided into four domains: ACD, AAC, PIESD, and PODD.

The Passenger-Owned Devices Domain (PODD) includes networks that communicate with the Passenger Device.  All communication with passenger devices is considered APC.

Virtual LAN (VLAN) allows segregation of traffic on a single Ethernet connection. PODD extends along any VLAN that communicates with the passenger devices.  PODD is considered a major cybersecurity attack plane requiring considerable efforts to restrict passenger devices to PODD and to not have access to any other domain.

The Passenger Information and Entertainment Services Domain (PIESD) is broadly applied to Inflight Entertainment (IFE) and to Inflight Connectivity (IFC), or Inflight Entertainment and Connectivity (IFEC).  PIESD can include passenger-oriented transactions (such as credit card processing), but does not include the "data plane" for user devices. 

PIESD segregation from PODD is a challenge. For example, a single wireless access point may communicate with passenger devices and with cabin crew devices. VLAN segregation is applied for segregation.

Some PIESD traffic relates to passenger devices (the airline portal, transaction processing, streaming entertainment). The remainder of PIESD traffic is between the IFEC components, for example for content update and for maintenance and control of the IFEC system.

Aeronautical Information Services Domain (AISD) is broadly applied to AAC.  Beyond airplane health monitoring (AHM) and maintenance, AISD includes connectivity with the Electronic Flight Bag (EFB). The EFB, by definition, is a non-safety function. EFB therefore is grouped as part of AAC and hence AISD.  The EFB should have no AOC application.

As many EFB are now hosted on iPads, and with concerns about using it as an attack vector, a special device, the ARINC 759/834(A) Aircraft Interface Device (AID)/Aircraft Interface Device Function (AIDF) stands between the EFB and aircraft networks. 

The Aircraft Control Domain (ACD) is applied broadly to Aircraft Communication, Addressing and Reporting System (ACARS). ACARS communication is most properly applied to ATS and AOC safety communications. 

Some ACARS traffic is not safety related and can span across to AAC. However, ACARS is constrained to ACD, while AAC is AISD. Special cybersecurity measures are applied to allow ACARS cross-domain traffic from AISD. 

Narrowband L-band satcom networks such as Inmarsat and Iridium have AMSRS designations. They are allowed to use the spectrum for non-safety applications only while assuring that the safety service performance is not degraded unacceptably.  Generally, narrowband satcom systems apply different radio channels to manage safety (ATS/AOC) and non-safety (AAC/APC). 

Broadband Ku/Ka satcom networks such as offered by Viasat, Viasat GX, Panasonic, Intelsat, Hughes, and Anuvu are designated AMSS for non-safety applications only (AAC, APC) and can span AISD, PIESD, and PODD. These networks operate a single carrier with "network slices" applied to different traffic grouping and with different quality of service (QoS). 

Hyperconnected ATM (HCATM) is an emerging concept to allow AOC/ATS messaging across a broadband Ku/Ka-band AMSS. The ACD router takes special measures (virtual private network, VPN) to connect via AISD and span across the AMSS link to provide strong authentication, integrity and confidentiality suitable for safety application.

Stay tuned!

Peter Lemme

peter @
Copyright 2023 All Rights Reserved

Peter Lemme has been a leader in avionics engineering for 42 years. He offers independent consulting services largely focused on avionics and L, Ku, and Ka band satellite communications to aircraft. Peter chaired the SAE-ITC AEEC Ku/Ka-band satcom subcommittee for more than ten years, developing ARINC 791 and 792 characteristics, and continues as a member. He also contributes to the Network Infrastructure and Interfaces (NIS) subcommittee.

Peter was Boeing avionics supervisor for 767 and 747-400 data link recording, data link reporting, and satellite communications. He was an FAA designated engineering representative (DER) for ACARS, satellite communications, DFDAU, DFDR, ACMS and printers. Peter was lead engineer for Thrust Management System (757, 767, 747-400), also supervisor for satellite communications for 777, and was manager of terminal-area projects (GLS, MLS, enhanced vision).

An instrument-rated private pilot, single engine land and sea, Peter has enjoyed perspectives from both operating and designing airplanes. Hundreds of hours of flight test analysis and thousands of hours in simulators have given him an appreciation for the many aspects that drive aviation; whether tandem complexity, policy, human, or technical; and the difficulties and challenges to achieving success.

No comments:

Post a Comment