FCI (Future Communications Infrastructure)
Future Communications Infrastructure — the LDACS/AeroMACS/SATCOM multi-link stack replacing congested VHF/VDL with an ATN/IPS-capable aeronautical data link system
FCI (Future Communications Infrastructure)
Definition
FCI stands for Future Communications Infrastructure. It is the ICAO-defined communications stack that replaces the congested legacy VHF voice and VDL Mode 2 data link system with a multi-subnetwork, IP-capable architecture covering all phases of aeronautical operation. The term appears in Doc 9896 (ATN/IPS Manual, 3rd edition, 2026) as an established ICAO acronym alongside the multilink and mobility function specifications that bind it.
FCI comprises three complementary links:
- LDACS (L-band Digital Aeronautical Communications System) — a terrestrial digital data link for en-route and TMA airspace, operating in the L-band ARNS spectrum (960-1164 MHz).
- AeroMACS (Aeronautical Mobile Airport Communications System) — a WiMAX-derived broadband data link for the aerodrome surface, operating in C-band 5 030-5 150 MHz.
- Aeronautical SATCOM — satellite data link for oceanic, remote, and continental gap coverage (Iris/Inmarsat in Europe; future broadband systems globally).
Together they implement the ATN/IPS multilink concept standardised in Annex 10 Vol III §3.4.10: the ATN/IPS shall be capable of supporting multilink — the ability to use more than one available air-ground subnetwork concurrently.
Regulatory Basis
The normative foundations are:
Annex 10 Vol III (Communication Systems) — the primary SARPs instrument for aeronautical communications. Chapter 3 Part I carries ATN/IPS requirements including the multilink Standard (§3.4.10). Chapter 7 carries full AeroMACS SARPs introduced by Amendment 90 via the ICAO Communications Panel first meeting (CP/1, 2016). AeroMACS frequency allocation is 5 030-5 150 MHz at 5 MHz channel bandwidth (§7.4.2.1). LDACS SARPs are under development by the CP and not yet incorporated in Annex 10.
Doc 9896 (Manual on the ATN using Internet Protocol Suite Standards and Protocols, 3rd edition, 2026) — the authoritative technical guidance for the ATN/IPS including the mobility and multilink function (Part I §2.5.3), the AGMI protocol, and subnetwork interoperability. Doc 9896 explicitly defines FCI in its abbreviations list and provides worked scenarios of LDACS/SATCOM multilink handover.
GANP/ASBU (Doc 9750) — FCI is the physical-layer delivery vehicle for the ASBU Technology Thread COMI (Communications Improvement). COMI-B1 baselines ATN/IPS over VDL Mode 2 and AeroMACS; COMI-B2 targets the full FCI stack — LDACS for en-route and broadband SATCOM for oceanic — enabling TBO-B2 data link requirements.
ITU Radio Regulations — the L-band ARNS allocation protecting LDACS and the 5 030-5 091 MHz sub-band protected for AeroMACS by WRC decisions underpin the frequency assignments.
Operational Meaning
FCI addresses three structural deficiencies in the current aeronautical communications system:
VHF spectrum congestion. The 118-136.975 MHz VHF aviation band, already expanded to 8.33 kHz spacing in Europe, is approaching capacity. Voice and VDL data compete in the same band; increasing traffic density cannot be accommodated. LDACS operates in a completely separate spectrum (L-band) with higher channel capacity per aircraft and no interference to the VHF voice system.
VDL Mode 2 saturation. VDL Mode 2 delivers 31.5 kbps per channel. In high-density terminal areas, multiple aircraft simultaneously using the same VDL channel create message queuing delays that compromise CPDLC and ADS-C message timeliness. LDACS provides substantially higher capacity and a dedicated aeronautical spectrum allocation.
Coverage continuity. No single radio covers gate, surface, TMA, en-route, and oceanic. SATCOM fills the oceanic/remote gap; AeroMACS serves the surface; LDACS serves the Continental en-route. The ATN/IPS multilink function stitches them together: the aircraft presents a single persistent IPv6 address, and the Multilink Decision Engine selects subnetworks per packet according to traffic class and link availability.
Operationally, the controller-pilot CPDLC dialogue is maintained without interruption across subnetwork transitions (Doc 9896 §2.5.3.6): the context management and CPDLC session survives handover between AeroMACS on the surface, LDACS in the TMA, and SATCOM in oceanic. This is the data link substrate that makes TBO-B2 and FF-ICE execution-phase messaging feasible end-to-end.
Framework Structure
Three-link architecture
Each FCI link serves a defined domain:
- AeroMACS — gate to runway; airport surface. Broadband (several Mbps per sector), short range (1-3 km per BS), high data rate enables pre-departure clearance, ATIS, digital weather, surface operations, A-SMGCS data feeds, and AOC communications on the ground.
- LDACS — departure, TMA, en-route over land. 500 kHz channels inlaid in the DME/TACAN spectrum gaps; OFDM modulation; high capacity and resilience to interference. Primary bearer for CPDLC ATN B2 and ADS-C in continental airspace in the FCI era.
- SATCOM — oceanic, polar, and remote continental (below LDACS terrestrial coverage). The Iris service (SESAR- validated, Inmarsat SwiftBroadband) provides ATN/IPS-capable SATCOM; it began ATN/OSI operations in 2025.
ATN/IPS multilink integration
The ATN/IPS Mobility and Multilink Function (Doc 9896 §2.5.3) is the network layer that binds the three physical links:
- Each aircraft uses AGMI (Air/Ground Mobility Interface) to report its active datalinks and preferences to the ground infrastructure.
- The MDE (Multilink Decision Engine) applies a policy information base to select subnetwork per packet class.
- Vertical handover between heterogeneous subnetworks (e.g. LDACS to SATCOM at oceanic entry) preserves the IP session.
- The ATN/IPS function may be provided by a single Communications Service Provider or by multiple CSPs acting in concert.
Spectrum pillars
| Link | Spectrum | Channel BW | Domain |
|---|---|---|---|
| LDACS | L-band 960-1164 MHz (ARNS) | 500 kHz | En-route, TMA |
| AeroMACS | C-band 5 030-5 150 MHz | 5 MHz | Airport surface |
| SATCOM | Ku/Ka/L-band (system-dependent) | Variable | Oceanic, remote |
FCI and CPDLC/TBO dependency
FCI is the COM enabler layer underneath TBO. The dependency chain runs: FCI physical link -> ATN/IPS multilink session -> CPDLC ATN B2 messages -> RTA/CTA constraints -> i4D/TBO operations. A state or ANSP that deploys LDACS and AeroMACS without deploying the ATN/IPS multilink management layer does not gain the FCI benefit.
External Sources
- https://www.icao.int/safety/acp/pages/communications-panel.aspx - ICAO Communications Panel (CP); FCI, LDACS, AeroMACS SARPs work programme
- https://www.eurocontrol.int/concept/ldacs - EUROCONTROL LDACS page; European deployment and SESAR validation overview
- https://www.sesarju.eu/ - SESAR 3 JU / Digital European Sky; LDACS and AeroMACS validation results
- https://store.icao.int/en/annex-10-aeronautical-telecommunications-volume-iii-communication-systems - Annex 10 Vol III at ICAO store
- https://store.icao.int/en/manual-on-the-aeronautical-telecommunication-network-atn-using-internet-protocol-suite-ips-standards-and-protocols-doc-9896 - Doc 9896 ATN/IPS Manual at ICAO store
References
Annex 10 Vol III (Communication Systems), Chapter 3, Part I, §3.4.10 — "ATN/IPS shall be capable of supporting multilink"; Note 1 points to Doc 9896.
Annex 10 Vol III, Chapter 7, §7.1 — Definition of AeroMACS: high-capacity data link supporting mobile and fixed communications on the aerodrome surface.
Annex 10 Vol III, Chapter 7, §7.3.1-§7.3.9 — AeroMACS SARPs including IP packet data services and ATN/IPS support.
Annex 10 Vol III, Chapter 7, §7.4.2.1 — AeroMACS frequency band 5 030-5 150 MHz in 5 MHz channels.
Annex 10 Vol III, Chapter 7, §7.3.2 — AeroMACS shall only transmit when on the surface of an aerodrome.
Doc 9896 (ATN/IPS Manual), Abbreviations — formal entry "FCI Future Communications Infrastructure".
Doc 9896, Part I, §2.5.3 — Mobility and Multilink Requirements; AGMI protocol; multilink decision engine.
Doc 9896, Part I, §2.5.3.6 — CM/CPDLC dialogue maintained across AeroMACS, VDLM2, SATCOM subnetwork transitions.
Doc 9896, Part IV, §8.1 and §8.2 — guidance on mobility/multilink scenarios including LDACS/SATCOM concurrent use and vertical handover (authoritative source — not in local library for Part IV; advance unedited 2026 edition).
Doc 9750 (GANP), ASBU Thread COMI — Communications Improvement thread; COMI-B1/B2 as the FCI delivery milestones (authoritative source — not in local library; see ganpportal.icao.int).
Related topics
Detailed working notes on FCI — the LDACS/AeroMACS/SATCOM
multi-link aeronautical communications stack that ICAO is
developing to replace the congested VHF/VDL legacy system.
This folder expands the summary in topics/fci.md into
per-aspect files.
Files in this folder
overview.md— what FCI is, the three-link architecture, and where it sits in the ICAO/ASBU/ATN/IPS framework.components.md— constituent elements: LDACS, AeroMACS, SATCOM, the ATN/IPS multilink layer, and spectrum pillars.blocks.md— FCI through the ASBU COMI blocks; domain-to- link mapping; maturity stages.threads.md— functional axes: LDACS thread, AeroMACS thread, SATCOM thread, multilink management, ATN/IPS integration, spectrum/standardisation.modules.md— anatomy of one unit: LDACS en-route deployment as a worked example.enablers.md— CNS, spectrum, certification, institutional, training, and regulatory enablers.performance_objectives.md— KPAs, KPIs, and the FCI performance framework.timeline.md— historical evolution from VDL congestion drivers to AeroMACS SARPs to LDACS SARPs development.references.md— consolidated ICAO and authoritative external references.
Reading order
Start with overview.md to understand the three-link concept.
Move to components.md for the technical profile of each link.
Read blocks.md for the ASBU deployment sequence. Use
threads.md for functional decomposition. Open modules.md
for a worked example. Consult enablers.md, performance_ objectives.md, and timeline.md as reference material.
references.md consolidates all citations.
Source basis
Content is grounded in:
- ICAO Annex 10 Vol III (Communication Systems), Chapter 3 (ATN/IPS) and Chapter 7 (AeroMACS SARPs).
- Doc 9896 (Manual on the ATN using IPS Standards and Protocols, 3rd edition, 2026, advance unedited) — the principal ATN/IPS guidance document; defines FCI and the multilink function.
- Doc 9750 (GANP) and the ASBU COMI thread on the GANP Portal: https://ganpportal.icao.int/
- EUROCONTROL LDACS programme and SESAR 3 JU validation results.
What FCI is
Future Communications Infrastructure (FCI) is the name ICAO gives to the three-link aeronautical communications stack designed to succeed the current VHF voice and VDL Mode 2 data link system. The term is defined in Doc 9896 (ATN/IPS Manual, 3rd edition 2026) in its abbreviations list, alongside the multilink management specifications that are the integrating glue.
The stack consists of three complementary radio technologies:
- LDACS — L-band Digital Aeronautical Communications System. A terrestrial digital data link for en-route and TMA airspace. Uses OFDM in the L-band ARNS spectrum (960-1164 MHz), inlaid between existing DME channel pairs.
- AeroMACS — Aeronautical Mobile Airport Communications System. A WiMAX-derived broadband data link for the aerodrome surface. Standardised in Annex 10 Vol III Chapter 7; operates in the ICAO-protected C-band allocation 5 030-5 150 MHz.
- Aeronautical SATCOM — satellite data link for oceanic, polar, and remote continental airspace. Iris/Inmarsat SwiftBroadband is the current European ATM SATCOM service; future broadband systems will expand global coverage.
These three links are bound together by the ATN/IPS Mobility and Multilink Function (Annex 10 Vol III §3.4.10; Doc 9896 §2.5.3), which allows the aircraft to use more than one available air-ground subnetwork concurrently and to maintain persistent application sessions across subnetwork transitions.
Why FCI is necessary
VHF spectrum saturation
The 8.33 kHz VHF channel spacing plan in European airspace has been progressively implemented since 2000. By the 2020s, the VHF aviation band is close to exhaustion in the busiest areas. VDL Mode 2, which uses the same physical band for digital data, competes with voice channels. Growth in traffic density cannot be accommodated within the existing VHF framework.
VDL Mode 2 capacity constraints
VDL Mode 2 delivers 31.5 kbps per channel. In high-density terminal areas, multiple aircraft sharing a single channel produce message queuing delays that degrade CPDLC and ADS-C responsiveness. The COCR (Communications Operating Concept and Requirements) studies conducted within SESAR and ICAO showed that VDL Mode 2 alone cannot meet the data link capacity requirements for ATN B2 CPDLC services in high-density continental airspace beyond approximately 2030.
Coverage continuity
No single existing system provides continuous coverage across all flight phases at the data rates needed for TBO. SATCOM fills the oceanic/remote gap but is expensive for continental use. LDACS fills the continental data link gap at lower cost and with a dedicated aeronautical spectrum allocation.
Where FCI sits in the ICAO/ATM framework
FCI sits at the bottom of a layered stack:
- Physical / radio layer — LDACS, AeroMACS, SATCOM radios.
- Network layer — ATN/IPS with multilink and mobility function (Doc 9896).
- Application layer — CPDLC, ADS-C, CM (context management), ACARS.
- Operational layer — TBO, FF-ICE execution phase, ADS-C conformance monitoring.
FCI without the ATN/IPS layer is three separate radios. It is the multilink function that makes FCI a coherent infrastructure rather than a collection of separate data links.
Relationship to sibling topics
- ATN/IPS — the networking/IP layer running over FCI subnetworks. FCI provides the physical links; ATN/IPS manages addressing, routing, mobility, and multilink across them.
- SATCOM/Iris — the SATCOM component of FCI in the European context. FCI provides the framing; Iris is the specific SATCOM service.
- Datalink / CPDLC — the applications that FCI carries. CPDLC and ADS-C run on top of ATN/IPS which runs on top of FCI subnetworks.
- TBO — the operational concept that drives the FCI capacity requirements. TBO needs CPDLC ATN B2 (RTA/CTA delivery) and ADS-C (EPP) which in turn need the higher- capacity, continuous-coverage data link that FCI provides.
References
- Annex 10 Vol III (Communication Systems), Chapter 3, Part I, §3.4.10 — multilink Standard for ATN/IPS.
- Annex 10 Vol III, Chapter 7 — AeroMACS SARPs (definition, frequency, performance).
- Doc 9896 (ATN/IPS Manual), Abbreviations — "FCI Future Communications Infrastructure".
- Doc 9896, Part I, §2.5.3 — Mobility and Multilink Requirements.
- Doc 9750 (GANP), ASBU Thread COMI — FCI delivery milestones (authoritative source — not in local library; see https://ganpportal.icao.int/).
FCI is a structured set of five constituent elements: three radio links, the ATN/IPS multilink integration layer, and the spectrum/standardisation framework that underpins all of them.
1. LDACS — L-band Digital Aeronautical Communications System
Purpose and domain
LDACS is the terrestrial en-route and TMA data link component of FCI. It provides a high-capacity, dedicated aeronautical spectrum channel that supplements and eventually replaces VDL Mode 2 in continental airspace.
Spectrum
LDACS operates in the L-band ARNS (Aeronautical Radio Navigation Service) spectrum, specifically in the sub-band 960-1164 MHz. This band is internationally protected for aeronautical radionavigation. LDACS uses a "fill-in" spectrum deployment: its 500 kHz forward and reverse link channels are inlaid between the existing DME/TACAN channel pairs, which are allocated at 1 MHz spacing. This approach minimises new spectrum requirements and is designed to coexist with DME without harmful interference.
Technology
LDACS uses OFDM (Orthogonal Frequency-Division Multiplexing) modulation, which provides robustness against multipath fading in the aeronautical environment. It supports:
- Multiple access (TDMA-based uplink, OFDMA downlink).
- Quality-of-service mechanisms to prioritise safety-of-life traffic (CPDLC, ADS-C) over lower-priority traffic.
- ATN/IPS subnetwork services, enabling integration into the multilink management function.
Standards status
LDACS SARPs are under development by the ICAO Communications Panel (CP). The SARPs are not yet incorporated in Annex 10. SESAR 3 JU and EUROCONTROL have conducted extensive LDACS validation trials in European airspace as part of the Digital European Sky programme.
2. AeroMACS — Aeronautical Mobile Airport Communications System
Purpose and domain
AeroMACS is the airport surface data link component of FCI. It provides broadband wireless communications between aerodrome-based ground stations and aircraft and vehicles on the aerodrome surface.
Spectrum
AeroMACS operates in the frequency band 5 030-5 150 MHz (5 MHz channel bandwidth), as specified in Annex 10 Vol III §7.4.2.1. This band is part of the internationally protected aeronautical mobile service allocation agreed at ITU World Radiocommunication Conferences. AeroMACS operates in TDD (time division duplex) mode.
Technology
AeroMACS is derived from the IEEE 802.16-2009 WiMAX mobile standard. The aeronautical profile is defined in:
- RTCA DO-345 / EUROCAE ED-222 (AeroMACS profile document).
- EUROCAE ED-223 / RTCA DO-346 (MOPS).
- EUROCAE ED-227 (MASPS).
Capabilities standardised in Annex 10 Vol III Chapter 7:
- High-capacity IP packet data services (§7.3.8).
- ATN/IPS and ATN/OSI (over IP) message transport (§7.3.9).
- Multiple levels of message priority (§7.3.5).
- Point-to-point, multicast, and broadcast (§7.3.6-§7.3.7).
- Adaptive modulation and coding (§7.3.12).
- Handover between AeroMACS base stations (§7.3.13).
- Flexible implementation architecture (§7.3.15).
AeroMACS base stations (BS) are fixed ground installations; mobile stations (MS) are fitted to aircraft and vehicles. The coverage radius per BS is typically 1-3 km, sufficient for a large aerodrome.
Standards status
AeroMACS SARPs are fully incorporated in Annex 10 Vol III Chapter 7, introduced by Amendment 90 (CP/1, 2016). This is the only FCI link with published ICAO SARPs in Annex 10.
3. Aeronautical SATCOM
Purpose and domain
The SATCOM component of FCI provides coverage for oceanic, polar, and remote continental airspace where terrestrial LDACS cannot reach. It is also used as the fallback link when terrestrial coverage is unavailable during continental flights.
Technology
Multiple SATCOM systems serve aviation:
- Inmarsat SwiftBroadband / Iris — the European ATM SATCOM service developed under the Iris programme by Inmarsat and ESA with SESAR funding. Iris provides an ATN/IPS-capable SATCOM link; Doc 9896 §2.1.1 records that the Viasat/Inmarsat Iris service started ATN/OSI operations in 2025.
- FANS-1/A SATCOM — the legacy HF + SATCOM combination used in FANS-equipped aircraft for oceanic CPDLC and ADS-C. Remains in service until ATN/IPS SATCOM is universally available.
- Future broadband systems — next-generation LEO and MEO satellite constellations (e.g. Iridium Certus, Starlink aviation variants) are candidates for future FCI SATCOM capacity.
The ATN/IPS vertical handover capability (Doc 9896 §8.1.37 and the Definitions §"Vertical Handover") manages seamless transitions between LDACS, VHF, and L-band SATCOM as coverage domains change.
Standards status
SATCOM connectivity within ATN/IPS is addressed in Doc 9896. The Iris system has its own regulatory framework within SESAR. No separate Annex 10 SATCOM SARPs specific to FCI have been published; the system relies on existing ATN/IPS and ICAO Annex 10 Vol III Part II/V communications procedures supplemented by SESAR programme deliverables.
4. ATN/IPS Multilink Integration Layer
Purpose
The multilink integration layer is the network-level element that binds the three physical links into one coherent communications system. Without it, LDACS, AeroMACS, and SATCOM are three separate radios with three separate management systems.
Key elements
The layer is defined in Annex 10 Vol III §3.4.10 and detailed in Doc 9896 Part I §2.5.3:
- AGMI (Air/Ground Mobility Interface) — protocol used by the aircraft to exchange multilink status and link preferences with the ground IPS infrastructure.
- MDE (Multilink Decision Engine) — applies a policy information base to select access network per packet class. Policies encode traffic classifier, link status, rank, and operational constraints.
- ATN/IPS Mobility and Multilink Function (MMF) — deployed in the ground infrastructure; provides multiple ground ingress/egress points, maintains no single point of failure.
- Multilink Co-ordination Point (MCP) — coordinates multilink management across multiple CSPs.
Key requirements from Annex 10 Vol III §3.4.10
and Doc 9896 §2.5.3
- ATN/IPS shall support concurrent use of more than one A/G datalink per aircraft (§2.5.3.2).
- The end-to-end application session and/or dialogue service shall be maintained when the set of A/G datalinks changes (§2.5.3.6).
- Multilink shall operate in compliance with the Safety and Performance Requirements for each applicable airspace (§2.5.3.5).
Hierarchy of elements
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- LDACS ground proxy
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- AeroMACS base station
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- SATCOM ground proxy | ATN/IPS Mobility and Multilink Function | AGMI protocol <---> aircraft IPS | Applications (CPDLC, ADS-C, CM, AOC)
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5. Spectrum and Standardisation Framework
FCI depends on internationally protected spectrum allocations and a set of industry standards bodies beyond ICAO:
| Dimension | LDACS | AeroMACS | SATCOM |
|---|---|---|---|
| Spectrum | L-band 960-1164 MHz (ARNS) | C-band 5 030-5 150 MHz | Ku/Ka/L-band (system-dependent) |
| ICAO SARPs | CP — in development | Annex 10 Vol III Ch 7 | Doc 9896 guidance only |
| Industry standards | EUROCAE/RTCA (in development) | RTCA DO-345/346, EUROCAE ED-222/223/227 | RTCA, EUROCAE, Inmarsat specs |
| Key ITU body | WRC (ARNS protection) | WRC (5 030-5 091 MHz AMT) | WRC (MSS allocations) |
The ICAO Communications Panel (CP) is the lead standards body. Regional programmes (SESAR 3 JU in Europe, FAA NextGen in the US) drive validation. Interoperability between regions requires ICAO to harmonise SARPs across the three links.
References
- Annex 10 Vol III (Communication Systems), Chapter 3, Part I, §3.4.10 — ATN/IPS multilink Standard.
- Annex 10 Vol III, Chapter 7, §7.1 — AeroMACS definition.
- Annex 10 Vol III, Chapter 7, §7.3.1-§7.3.15 — AeroMACS SARPs.
- Annex 10 Vol III, Chapter 7, §7.4.2.1 — AeroMACS frequency band 5 030-5 150 MHz.
- Doc 9896 (ATN/IPS Manual), Part I, §2.5.3 — Mobility and Multilink Requirements.
- Doc 9896, Definitions — Multilink, Multilink Decision Engine, Vertical Handover definitions.
- Doc 9896, Part IV, §8.1 — background and context for mobility and multilink management (authoritative source — advance unedited 2026 edition).
FCI is delivered through the ASBU Technology Thread COMI (Communications Improvement), which covers both surface (COMS) and air-ground (COMI) communications. The blocks represent the maturity sequence by which FCI components enter operational service.
Domain-to-link mapping
Block 0 — Legacy baseline (from 2013)
At Block 0, air-ground communications rely on the existing technology stack:
- VHF voice for ATC instructions.
- VDL Mode 2 / ACARS for CPDLC (ATN Baseline 1) and ADS-C in equipped aircraft.
- FANS-1/A SATCOM for oceanic CPDLC and ADS-C.
No FCI-specific components are deployed in Block 0, but the foundation is established: aircraft equipped for CPDLC and ADS-C, and ground systems supporting ATN Baseline 1.
| Characteristic | Block 0 |
|---|---|
| Primary data link | VDL Mode 2 / ACARS |
| Oceanic coverage | FANS-1/A SATCOM (HF backup) |
| Surface data link | ACARS gate link (gatelink) |
| Network layer | ATN/OSI primarily |
| FCI component | None deployed |
Block 1 — ATN/IPS + AeroMACS surface (from 2019)
Block 1 introduces the first FCI component (AeroMACS) and migrates the network layer from ATN/OSI to ATN/IPS:
- AeroMACS surface deployment — broadband data link for gate and airport surface. Pre-departure clearance, digital ATIS, surface operations data, AOC messages. AeroMACS SARPs are in Annex 10 Vol III Chapter 7 (Amendment 90).
- ATN/IPS migration — ground infrastructure migrates to ATN/IPS IPv6 while maintaining backward compatibility with ATN/OSI. VDL Mode 2 continues as the en-route data link.
- Multilink groundwork — the ATN/IPS Mobility and Multilink Function is deployed in ground infrastructure, capable of managing VDL Mode 2 and AeroMACS as two concurrent subnetworks.
- CPDLC ATN B2 — ATN Baseline 2 messaging capability over the ATN/IPS network, enabling RTA/CTA delivery and the richer message set needed for TBO precursors.
| Characteristic | Block 1 |
|---|---|
| Primary data link | VDL Mode 2 (en-route); AeroMACS (surface) |
| Oceanic coverage | FANS-1/A + Iris ATN/IPS (initial) |
| Surface data link | AeroMACS (SARPs published) |
| Network layer | ATN/IPS (with ATN/OSI interop) |
| FCI component | AeroMACS surface; multilink layer |
Block 2 — Full FCI stack (from 2025)
Block 2 is the full FCI deployment target:
- LDACS en-route — terrestrial en-route and TMA data link in L-band. Replaces VDL Mode 2 as the primary continental data link. Requires LDACS SARPs (CP work programme) and ground station network build-out.
- Broadband SATCOM (Iris/ATN/IPS) — replaces legacy FANS-1/A SATCOM with ATN/IPS-capable broadband SATCOM for oceanic/remote coverage. Iris started ATN/OSI operations in 2025.
- Full multilink operation — LDACS, AeroMACS, and SATCOM managed concurrently by the ATN/IPS multilink function. Vertical handover between all three subnetworks is seamless. Aircraft holds one persistent IPv6 address.
- TBO data link capacity — sufficient link capacity and continuity to support TBO-B2: i4D, negotiated 4D trajectories, and ADS-C EPP conformance monitoring across all flight phases.
| Characteristic | Block 2 |
|---|---|
| Primary data link | LDACS (en-route); AeroMACS (surface) |
| Oceanic coverage | Iris ATN/IPS SATCOM |
| Surface data link | AeroMACS (fully operational) |
| Network layer | ATN/IPS with full multilink |
| FCI component | Full three-link stack |
Block 3 — Evolution and resilience (from 2031)
Block 3 extends FCI with higher capacity, additional spectrum options, and integration with future ATM concepts:
- Next-generation SATCOM (LEO/MEO constellations) for higher-capacity oceanic data link.
- Enhanced LDACS capacity for higher traffic densities as TBO-B3 requires richer air-ground data exchange.
- Full automation-to-automation communications for trajectory negotiation without controller intervention.
- Extended FCI coverage to UAS and emerging airspace users.
| Characteristic | Block 3 |
|---|---|
| Primary data link | LDACS + next-gen SATCOM |
| Oceanic coverage | LEO/MEO broadband SATCOM |
| Surface data link | AeroMACS enhanced |
| Network layer | ATN/IPS fully mature |
| FCI component | Evolution of all three links |
Summary table
| Block | Notional from | FCI focus | Key ASBU module |
|---|---|---|---|
| Block 0 | 2013 | Legacy VDL/FANS baseline | COMI-B0 |
| Block 1 | 2019 | AeroMACS surface + ATN/IPS migration | COMI-B1 |
| Block 2 | 2025 | LDACS en-route + broadband SATCOM + full multilink | COMI-B2 |
| Block 3 | 2031 | Next-gen links + TBO-B3 data rates | COMI-B3 |
References
- Annex 10 Vol III (Communication Systems), Chapter 7 — AeroMACS SARPs (Block 1 deployment basis).
- Annex 10 Vol III, Chapter 3, §3.4.10 — ATN/IPS multilink Standard (Block 1-2 network layer requirement).
- Doc 9896 (ATN/IPS Manual), §2.5.3 — Multilink Requirements governing the Block 1-2 transition.
- Doc 9896, §2.1.1 — Iris SATCOM ATN/OSI operations commenced 2025 (Block 2 SATCOM milestone).
- Doc 9750 (GANP), ASBU Thread COMI — Block deployment timeline (authoritative source — not in local library; see https://ganpportal.icao.int/).
FCI can be decomposed into six functional axes. Each thread represents a distinct subject line from which FCI evolves and which must be managed independently even though they interact constantly.
Thread 1 — LDACS (L-band Digital Aeronautical Comms)
Scope
The LDACS thread covers the terrestrial en-route and TMA data link component: spectrum engineering, SARPs development, ground station network design, avionics certification, and operational deployment.
Key activities by phase
- Standards — ICAO Communications Panel (CP) developing LDACS SARPs for incorporation in Annex 10 Vol III. EUROCAE and RTCA developing minimum operational performance specifications.
- Validation — SESAR 3 JU / Digital European Sky has conducted multiple LDACS flight trials in European airspace demonstrating ATN/IPS data link capability at realistic traffic densities.
- Deployment — LDACS ground station network requires dense terrestrial coverage similar to DME/TACAN. Frequency coordination must avoid interference to existing DME pairs.
- Avionics — aircraft need LDACS-capable avionics. Retrofit of existing fleets is a major transition cost; phased equipage plans required.
Interaction with other threads
LDACS provides the continental data link substrate that carries ATN/IPS multilink traffic. LDACS ground station deployment depends on the spectrum/standardisation thread (ITU coordination). LDACS operational activation depends on the ATN/IPS integration thread completing the multilink management layer.
Thread 2 — AeroMACS (Airport Surface Comms)
Scope
The AeroMACS thread covers the airport surface data link: WiMAX-based broadband communications for aircraft, vehicles, and fixed aerodrome infrastructure, operating in C-band 5 030-5 150 MHz.
Key activities
- Standards — Annex 10 Vol III Chapter 7 SARPs are published (Amendment 90, 2016). Industry MOPS (EUROCAE ED-223/RTCA DO-346) and MASPS (EUROCAE ED-227) define implementation requirements.
- Deployment — Airport operators install AeroMACS base stations (BS) as part of A-SMGCS and advanced surface operations upgrades. Aircraft with AeroMACS mobile station (MS) avionics use the surface data link.
- Services — pre-departure clearance, D-ATIS, surface movement data, digital weather, AOC communications.
- Coexistence — must avoid interference with MLS systems in the 5 030-5 091 MHz sub-band per Annex 10 Vol III §7.4.2.1 notes.
Standards basis
AeroMACS is the most mature FCI component in terms of ICAO standardisation. Annex 10 Vol III §7.3.1 states "AeroMACS shall conform to the requirements of this and the following chapters." The IEEE 802.16-2009 basis is explicitly acknowledged in the Annex (§7.3.2 Note 2).
Thread 3 — Aeronautical SATCOM
Scope
The SATCOM thread covers satellite-based data link for oceanic, polar, and remote continental airspace: spectrum coordination, service provider certification, ATN/IPS integration, and the FANS-1/A to ATN/IPS migration.
Key activities
- Iris programme (Europe) — the ESA/Inmarsat Iris service provides ATN/IPS-capable SATCOM for European ATM. Iris started ATN/OSI SATCOM operations in 2025 (Doc 9896 §2.1.1). Migration from ATN/OSI to ATN/IPS over Iris is the Block 2 SATCOM objective.
- FANS-1/A migration — oceanic regions continue with FANS-1/A SATCOM until ATN/IPS SATCOM is available fleet-wide. Dual capability (FANS-1/A + ATN B2) may be required during transition.
- Next-generation SATCOM — LEO and MEO constellations (Iridium Certus, Starlink aviation, OneWeb) are under evaluation for aeronautical use. Higher capacity and lower latency than legacy GEO SATCOM; ICAO and industry are assessing whether they can meet aeronautical safety and performance requirements.
- Polar coverage — current GEO SATCOM has poor polar coverage. LEO systems address this.
Thread 4 — Multilink Management
Scope
The multilink management thread covers the network-layer architecture that binds all FCI subnetworks: the AGMI protocol, the MDE, the ATN/IPS Mobility and Multilink Function, and the policy information base.
Key activities
- AGMI deployment — aircraft and ground infrastructure implement AGMI to exchange real-time multilink status.
- MDE configuration — policies are engineered by service providers to prioritise safety-of-life traffic (CPDLC, ADS-C) on the best available link and route other traffic on secondary links.
- CSP coordination — where multiple Communications Service Providers (CSPs) operate, the Multilink Co-ordination Point (MCP) ensures consistent multilink management. A single point of failure is prohibited (Doc 9896 §2.5.3.16).
- Vertical handover testing — integration testing across LDACS, AeroMACS, and SATCOM handover scenarios is required before operational deployment.
References
Doc 9896 Part I §2.5.3 is the normative source for this thread. Part IV §8 provides worked multilink use cases including LDACS-to-SATCOM foreign report scenarios.
Thread 5 — ATN/IPS Integration
Scope
The ATN/IPS integration thread covers the network-level migration from ATN/OSI to ATN/IPS, the interoperability requirements between the two generations, and the application-layer services running over ATN/IPS.
Key activities
- Ground infrastructure migration — ANSPs and CSPs deploy ATN/IPS ground networks; IPv6 routing, addressing, naming, and security (PKI) per Doc 9896 Part I.
- Interoperability with ATN/OSI — Doc 9896 Part III provides convergence mechanisms for ATN/OSI applications (CPDLC, CM, ADS-C) to run over the ATN/IPS transport layer.
- Application migration — CPDLC migrates from ATN Baseline 1 (over ATN/OSI/VDL Mode 2) to ATN Baseline 2 (over ATN/IPS/LDACS, AeroMACS, SATCOM).
- Security — ATN/IPS security is mandated: IPsec, TLS, PKI. Doc 9896 references Doc 10095 (PKI Manual), Doc 10090 (Security Services), Doc 10145 (Security Risk Assessment).
Thread 6 — Spectrum and Standardisation
Scope
The spectrum and standardisation thread covers the regulatory and ITU coordination work that protects the FCI frequency allocations and the ICAO standards development process.
Key activities
- ITU World Radiocommunication Conference (WRC) decisions — the 5 030-5 091 MHz sub-band aeronautical allocation for AeroMACS and the ARNS L-band protection for LDACS both require WRC-level coordination and maintenance through ITU Radio Regulations.
- ICAO Communications Panel (CP) — the standards- making body for FCI. CP/1 (2016) produced the AeroMACS SARPs. LDACS SARPs development is the current priority.
- EUROCAE/RTCA — joint standards bodies producing MOPS and MASPS for avionics certification (AeroMACS RTCA DO-345/346, ED-222/223/227; LDACS documents in development).
- National spectrum authorities — states must coordinate AeroMACS frequency assignments with MLS to avoid interference; LDACS requires coordination with existing DME users.
Thread interaction map
-
-
- LDACS + AeroMACS + SATCOM (physical) | | | +-----------+-----------+ | Multilink Management Thread | ATN/IPS Integration Thread | CPDLC, ADS-C, CM, FF-ICE applications ^ Spectrum/Standardisation Thread (underpins all physical links)
-
References
- Annex 10 Vol III, Chapter 7 — AeroMACS SARPs (Thread 2 normative basis).
- Annex 10 Vol III, §3.4.10 — ATN/IPS multilink Standard (Thread 4 normative basis).
- Doc 9896 (ATN/IPS Manual), §2.5.3 — Multilink and mobility management (Thread 4).
- Doc 9896, §2.1.1 — Iris SATCOM ATN/OSI operations 2025 (Thread 3 milestone).
- Doc 9896, Definitions — Vertical Handover, Multilink, MDE, AGMI (Thread 4 definitions).
- Doc 9750 (GANP), ASBU Thread COMI — overall FCI deployment context (authoritative source — not in local library; see https://ganpportal.icao.int/).
This file walks through one FCI unit as a worked example: the deployment of an LDACS en-route station pair and the activation of ATN/IPS multilink at a continental ANSP. This is the Block 2 (COMI-B2) unit that transitions a state from VDL Mode 2 to LDACS as the primary en-route data link.
The unit: LDACS station pair at one FIR entry point
Domain: En-route / TMA, continental airspace. Block: COMI-B2 (from 2025). Trigger: VDL Mode 2 channel congestion in a high-density sector, combined with the availability of LDACS SARPs and certified avionics from at least one major aircraft type.
Step 1 — Spectrum coordination
Before a ground station is installed, the ANSP must:
- Identify available L-band ARNS sub-channels in the local DME/TACAN channel plan. LDACS uses 500 kHz channels inlaid between DME pairs at 1 MHz intervals. The ANSP coordinates with the national spectrum authority and with adjacent ANSPs to confirm no harmful interference to existing DME users.
- Obtain national spectrum assignment for the chosen forward link (ground-to-air) and reverse link (air-to-ground) channel pair.
- File frequency coordination through the ITU process where required by national spectrum regulations.
Step 2 — Ground station installation
The LDACS ground station ("base station") is installed at a suitable site in the sector, typically co-located with existing VOR/DME or radar infrastructure to use the same tower, power, and communications backhaul:
- The ground station connects to the ANSP's ATN/IPS ground network as a new subnetwork access point.
- The AGMI ground proxy for the LDACS subnetwork is deployed as part of the ATN/IPS Mobility and Multilink Function.
- The new subnetwork is registered in the multilink policy information base alongside the existing VDL Mode 2 subnetwork.
Step 3 — ATN/IPS multilink configuration
The ATN/IPS Mobility and Multilink Function (per Doc 9896 §2.5.3) is configured for the new LDACS subnetwork:
- LDACS is added as a higher-priority subnetwork for safety-of-life CPDLC and ADS-C traffic within the LDACS coverage volume.
- VDL Mode 2 remains active as a secondary/fallback link outside LDACS coverage and during the equipage transition period.
- MDE policies are set: when LDACS is available with adequate signal quality, route CPDLC/ADS-C over LDACS; when LDACS is unavailable or the aircraft lacks an LDACS avionics unit, fall back to VDL Mode 2 or SATCOM as appropriate.
Step 4 — Aircraft avionics and equipage
For each aircraft operator whose fleet includes LDACS- capable avionics:
- The LDACS mobile station is tested and certified per EUROCAE MOPS.
- The aircraft's ATN/IPS stack is updated to include the LDACS subnetwork in its AGMI reporting.
- The flight management system (FMS) and avionics suite are updated to allow the cockpit CPDLC terminal to work over LDACS as well as VDL Mode 2.
- The aircraft's multilink logic is configured to prefer LDACS in LDACS coverage areas, automatically falling back to VDL Mode 2 or SATCOM outside.
Step 5 — Operational activation
The LDACS station is activated for trial operations:
- ATC ground systems receive CPDLC and ADS-C messages routed over LDACS for LDACS-equipped aircraft.
- The ATN/IPS multilink function confirms that CPDLC sessions are maintained without interruption as aircraft enter and exit LDACS coverage (vertical handover).
- Ground system tools display the active subnetwork for each CPDLC session, allowing controllers to monitor link health.
- Performance data (message delivery time, availability, error rate) are collected against the applicable Safety and Performance Requirements (SPR) for the airspace.
Step 6 — Performance measurement
Key performance measurements for this module (mirroring the FCI performance_objectives.md KPI table):
- CPDLC delivery time — measured from controller uplink to WILCO/UNABLE receipt. Must meet the RCP (Required Communications Performance) value for the airspace (e.g. RCP 240 for oceanic; RCP 130 for continental CPDLC).
- Link availability — LDACS coverage availability within the declared service volume (target >99.9% for safety-of-life services).
- Multilink session continuity — number of CPDLC sessions dropped or requiring re-establishment across subnetwork handover events (target: zero drops).
- Spectrum interference — no recorded interference to adjacent DME pairs; confirmed by post-activation monitoring.
Dependency chain for this module
Contrast: AeroMACS surface module (brief)
For comparison, an AeroMACS surface module at a major airport follows similar steps but with different specifics:
- Spectrum: 5 030-5 150 MHz, 5 MHz channels, coordinated with MLS.
- Ground stations: multiple BS installed at strategic points around the aerodrome surface (gates, apron, taxiway hold points) to ensure full coverage.
- Services: D-ATIS, pre-departure clearance, surface movement data, D-OTIS (obstacle-safe taxi routing), AOC.
- Coverage test: confirm all aircraft parking positions and taxiway areas are within at least one BS service volume.
- Handover: aircraft moving across the aerodrome surface perform break-before-make handover between adjacent AeroMACS BSs (Annex 10 Vol III §7.3.13).
References
- Annex 10 Vol III, Chapter 7, §7.3.1-§7.3.15 — AeroMACS SARPs used in the surface module comparison.
- Annex 10 Vol III, Chapter 7, §7.4.2.1 — AeroMACS frequency band (5 030-5 150 MHz).
- Doc 9896 (ATN/IPS Manual), §2.5.3.2-§2.5.3.16 — Multilink requirements governing Steps 3 and 5.
- Doc 9896, §2.5.3.6 — end-to-end CPDLC session maintained across subnetwork transitions.
- Doc 9896, Part IV, §8.2 — worked LDACS/SATCOM multilink use cases (authoritative source — advance unedited 2026 edition).
FCI cannot be deployed by ANSPs and aircraft operators in isolation. It depends on a set of enabling conditions across spectrum, regulation, standards, infrastructure, avionics, human factors, and institutional arrangements.
1. Spectrum protection and assignment
ITU Radio Regulations provide the international spectrum protection framework without which FCI cannot exist:
- LDACS L-band (960-1164 MHz) — the ARNS (Aeronautical Radio Navigation Service) allocation in this band is the spectrum basis. ITU WRC decisions must protect the LDACS inlaid channels from interference by non- aeronautical systems growing in adjacent bands (DME spectrum is shared with radar altimeters and military systems in some states).
- AeroMACS C-band (5 030-5 150 MHz) — the 5 030-5 091 MHz sub-band is protected at WRC for aeronautical mobile service. States must coordinate AeroMACS assignments with MLS systems sharing the lower end of the band.
- National spectrum assignment — each LDACS ground station requires a national frequency assignment coordinated by the national spectrum authority. Mass deployment of LDACS requires pre-planned national channel plans.
2. ICAO SARPs development (LDACS)
AeroMACS SARPs are published (Annex 10 Vol III Chapter 7). LDACS SARPs are the outstanding regulatory enabler:
- The ICAO Communications Panel (CP) is the responsible standards body. Until LDACS SARPs are incorporated in Annex 10, states cannot mandate LDACS avionics equipage under ICAO obligations and interoperability cannot be guaranteed.
- EUROCAE Working Group 82 (WG-82) and RTCA are developing the LDACS MOPS for avionics certification.
- Regional implementation mandates (e.g. European Implementing Regulation) will follow ICAO SARPs adoption.
3. Industry standards (MOPS and MASPS)
Aircraft certification agencies (EASA, FAA, CAAC) approve avionics against industry minimum operational performance standards:
- AeroMACS: RTCA DO-345 / EUROCAE ED-222 (profile), RTCA DO-346 / EUROCAE ED-223 (MOPS), EUROCAE ED-227 (MASPS) — all published.
- LDACS: MOPS under development in EUROCAE WG-82 / RTCA SC-228 (or equivalent). Until MOPS are published and approved by certification authorities, LDACS avionics cannot be certified for operational use.
4. Ground station network infrastructure
Terrestrial FCI coverage requires a dense ground station network:
- LDACS ground stations — spaced to provide continuous coverage across the served en-route and TMA volumes. Coverage gaps allow fallback to VDL Mode 2 or SATCOM via multilink but reduce the LDACS capacity benefit. States with smaller ANSP budgets may require bilateral or regional coordination to fund ground station deployment.
- AeroMACS base stations — typically 3-6 base stations per large aerodrome for full surface coverage, including all apron areas, taxiways, and runway holding positions. Airport operators are the primary infrastructure providers.
- ATN/IPS ground network — high-availability IPv6 network interconnecting LDACS ground proxies, AeroMACS gateways, SATCOM ground stations, and ANSP ATM systems. The ATN/IPS Mobility and Multilink Function must be deployed with no single point of failure (Doc 9896 §2.5.3.16).
5. Avionics equipage
The transition from VDL Mode 2 to FCI requires fleet-wide avionics upgrades:
- LDACS avionics — new radio units, antennas, and software in the aircraft avionics suite. Retrofit of existing long-haul and medium-haul fleets is expensive; line-fit from aircraft manufacturers for new deliveries is the more cost-effective path.
- AeroMACS avionics — MS units for aircraft operating at AeroMACS-equipped airports. Useful even without full FCI deployment for ground-only data services.
- ATN/IPS stack upgrade — aircraft IPS software and AGMI firmware must be updated to support multilink management across LDACS, AeroMACS, and SATCOM.
6. Certification and airworthiness
New avionics must follow the applicable certification basis:
- EASA CS-ACNS (Communication, Navigation, Surveillance) and FAA TSO frameworks.
- Supplemental Type Certificates (STC) for retrofit; type design changes for line-fit.
- Safety assessments (operational hazard assessment, safety assessment per Doc 9896) for each subnetwork deployment.
7. Procedures and training
FCI changes are largely transparent to controllers and pilots because the ATN/IPS multilink function manages subnetwork selection automatically. However:
- Controller procedures — CPDLC procedures (Doc 4444 Chapter 14) remain valid; the data link is the transparent carrier. Controllers may receive new displays showing active subnetwork status.
- Pilot procedures — minimal change; the cockpit CPDLC terminal continues to function identically. Pilots should understand the fallback hierarchy (LDACS -> VDL M2 -> SATCOM -> HF voice) in case of data link failure.
- Maintenance training — avionics technicians require training on LDACS and AeroMACS line-replaceable units.
- ANSP training — ground system managers must understand multilink policy configuration and performance monitoring.
8. Institutional and financing enablers
- National Air Navigation Plans — states must include LDACS and AeroMACS deployment in their national ANPs aligned with ASBU COMI-B1/B2 milestones.
- Regional coordination — LDACS coverage is most effective with coordinated regional deployment; a single-state deployment creates coverage gaps at FIR boundaries.
- Business case — Doc 9587 (ICAO policy on the economic regulation of international air transport) requires business-case justification for ASBU modules. The FCI business case depends on quantified capacity relief from VDL congestion and enablement of TBO operational benefits.
- SESAR / NextGen co-funding — large-scale FCI validation and initial deployment have been funded through SESAR (Europe) and FAA NextGen (US). APAC and other regions will require their own funding mechanisms.
References
- Annex 10 Vol III, Chapter 7, §7.3.2 Note 2 — AeroMACS MOPS reference (RTCA DO-345, EUROCAE ED-222/ED-223).
- Annex 10 Vol III, Chapter 7, §7.4.2.1 Note 1 — AeroMACS MASPS reference (EUROCAE ED-227).
- Doc 9896 (ATN/IPS Manual), §2.5.3.16 — no single point of failure requirement for ATN/IPS Multilink Function.
- Doc 9587 (Economic Regulation Manual), §relevant sections — business case requirements for ASBU module financing.
- Doc 9750 (GANP), ASBU Thread COMI — deployment enablers and dependencies (authoritative source — not in local library; see https://ganpportal.icao.int/).
The performance lens of FCI
FCI is a communications technology investment, not an end in itself. Its performance is measured by the degree to which it enables the operational objectives of ATM: safety, capacity, efficiency, predictability, and interoperability. The ICAO KPA framework (Doc 9854 / Doc 9883) provides the evaluation scaffold.
The performance chain for FCI runs:
KPA --> KPI --> Required Comms Performance (RCP) --> FCI subnetwork --> Operational service
The RCP specification (Doc 9869, Required Communications Performance) defines the transaction time, continuity, availability, and integrity requirements for each communication application. FCI subnetworks must satisfy the RCP specification assigned to the airspace.
Key Performance Areas applicable to FCI
FCI primarily influences six KPAs from the eleven defined in Doc 9854/Doc 9883:
| KPA | Relevance to FCI |
|---|---|
| Safety | Reliable CPDLC and ADS-C depend on the link; link failures create voice-only fallback with higher controller workload and error risk. |
| Capacity | Spectrum capacity determines how many CPDLC transactions can be handled per sector per hour; VDL congestion is the current capacity ceiling. |
| Flight efficiency | Higher-capacity, lower-latency data link enables real-time trajectory updates, reducing deviation from user-preferred trajectory. |
| Predictability | Timely CPDLC delivery of RTA/CTA constraints reduces variance between planned and actual gate-to-gate times (TBO enabler). |
| Interoperability | Multi-vendor LDACS/AeroMACS implementations must interoperate per ICAO SARPs; multilink transitions between subnetworks from different CSPs must be seamless. |
| Cost-effectiveness | FCI reduces reliance on expensive VHF spectrum expansion; shared LDACS ground station infrastructure amortises cost across multiple ANSPs. |
KPA contribution by link and block
The following matrix scores each KPA by the FCI deployment phase at which it is the primary benefit driver (1 = some benefit, 2 = clear benefit, 3 = primary driver). The columns are the three FCI links; the B1/B2 label indicates the ASBU block.
| KPA | AeroMACS (B1) | LDACS (B2) | SATCOM-IPS (B2) |
|---|---|---|---|
| Safety | 2 | 3 | 2 |
| Capacity | 2 | 3 | 1 |
| Flight efficiency | 1 | 3 | 2 |
| Predictability | 1 | 3 | 2 |
| Interoperability | 2 | 3 | 2 |
| Cost-effectiveness | 2 | 2 | 2 |
Required Communications Performance (RCP) targets
RCP specifications define the end-to-end performance required from the communications system for a given application in a given airspace. The FCI links must deliver subnetwork performance consistent with the RCP assigned:
| RCP type | Transaction time | Continuity | Availability | Typical use |
|---|---|---|---|---|
| RCP 10 | 10 s | 1-2 x 10-5 | 0.999 95 | Not yet operationally assigned |
| RCP 130 | 130 s | 1-2 x 10-5 | 0.999 95 | Continental CPDLC (COMI-B1/B2) |
| RCP 240 | 240 s | 1-2 x 10-5 | 0.999 95 | Oceanic CPDLC (FANS-1/A; SATCOM) |
| RCP 400 | 400 s | 1-2 x 10-5 | 0.999 95 | ADS-C periodic reporting |
LDACS targets RCP 130 or better in continental en-route airspace. AeroMACS targets similar or better performance in the airport surface domain. SATCOM (Iris) must meet RCP 240 for oceanic CPDLC.
Quantitative FCI performance objectives
Performance objectives specific to the FCI programme (drawn from ICAO Communications Panel and SESAR objectives):
Spectrum efficiency
The objective is to eliminate VDL Mode 2 channel saturation in high-density continental sectors by 2030 (COMI-B2 milestone). LDACS provides substantially more capacity than VDL Mode 2 per aircraft per channel by exploiting a dedicated spectrum allocation and higher spectral efficiency via OFDM.
Link availability
- AeroMACS: at least 99.9% availability in the declared service volume on the aerodrome surface.
- LDACS: at least 99.9% availability in the declared service volume within the terrestrial coverage area.
- SATCOM: at least 99.5% availability on oceanic routes with service-volume-specific values per Iris/SESAR.
Multilink session continuity
Zero CPDLC sessions dropped during subnetwork handover events (LDACS-to-AeroMACS at aerodrome entry; LDACS-to- SATCOM at oceanic entry). This is a binary quality objective measured per Doc 9896 §2.5.3.6.
Message latency
CPDLC uplink transaction time from controller input to pilot receipt in normal conditions: less than 10 seconds for LDACS in continental airspace (well within RCP 130). AeroMACS surface latency: less than 2 seconds.
KPAs, KPIs, and FCI performance monitoring
| KPA | KPI | FCI measurement |
|---|---|---|
| Safety | CPDLC transaction delivery rate | Percentage of CPDLC messages delivered within RCP time; downtime duration. |
| Capacity | VDL channel occupancy / congestion events | Reduction in VDL congestion events per sector per hour after LDACS activation. |
| Flight efficiency | Deviation from agreed trajectory (EPP delta) | Proxy: timely RTA delivery enables trajectory conformance; measured via ATFM. |
| Predictability | Arrival variance (actual vs planned landing time) | Proxy: CPDLC RTA/CTA delivery latency as a component of TBO predictability chain. |
| Interoperability | Multi-vendor handover test pass rate | Number of successful AGMI handover events between different CSP subnetworks. |
| Cost-effectiveness | CPDLC cost per transaction | Ground station and spectrum cost per CPDLC transaction delivered vs VDL M2 baseline. |
Why performance targets matter for planning
FCI investment is justified in ASBU terms only if the communications performance improvement is measurable. States submitting ASBU implementation plans are expected to show (per Doc 9587):
- The current VDL congestion problem quantified (channel load, message delay statistics).
- The projected FCI performance improvement (RCP compliance rate, channel relief factor).
- A business case that links FCI investment to the operational benefits enabled (TBO, CDM, ATFM).
References
- Annex 10 Vol III, Chapter 7 — AeroMACS SARPs establishing baseline availability and performance requirements.
- Annex 10 Vol III, Chapter 3, §3.4.10 — multilink Standard requiring compliance with SPR per airspace.
- Doc 9896 (ATN/IPS Manual), §2.5.3.5 — multilink shall operate in compliance with Safety and Performance Requirements for each applicable airspace.
- Doc 9869 (Required Communications Performance, RCP) — RCP specification framework (authoritative source — not in local library).
- Doc 9854 (Global ATM Operational Concept) — KPA framework; management by trajectory as the TBO operational concept FCI enables.
- Doc 9750 (GANP), ASBU Performance Objectives — COMI performance targets (authoritative source — not in local library; see https://ganpportal.icao.int/).
Two timelines for FCI
- Standards and regulatory timeline — when ICAO and industry published the SARPs, documents, and standards underpinning each FCI component.
- Operational deployment timeline — when FCI components entered or are projected to enter operational service.
FCI standards and regulatory timeline
| Year | Event |
|---|---|
| 1995 | Annex 10 Vol III restructured to include VDL SARPs (Amendment 70). |
| 1997-2004 | VDL Mode 2 SARPs progressively developed (Amendments 72-82). VDL M2 becomes the primary ATN data link standard. |
| 2005 | ICAO Council adopts the Global ATM Operational Concept (Doc 9854); "management by trajectory" established as a core concept. |
| 2006-2008 | ICAO initiates the Communications Operating Concept and Requirements (COCR) study identifying VDL Mode 2 saturation as a structural problem in high-density airspace. |
| 2010 | SESAR programme selects LDACS as the candidate L-band technology for European en-route data link. AeroMACS selected for airport surface. ITU WRC-07 protects 5 030-5 091 MHz sub-band for aeronautical mobile service (AeroMACS precondition). |
| 2012 | RTCA DO-345 / EUROCAE ED-222 published: AeroMACS profile document (base standard for aeronautical WiMAX deployment). |
| 2013 | ASBU framework introduced in GANP 4th edition; COMI thread defined for communications improvement; Block 0 baseline includes VDL M2. |
| 2013 | Annex 10 Vol III Amendment 88-A: VDL SARPs updated; provisions added to encourage ATN/IPS implementation while ATN/OSI remains supported. |
| 2015-2016 | AeroMACS MOPS published: EUROCAE ED-223 / RTCA DO-346. EUROCAE ED-227 (AeroMACS MASPS) published. |
| 2016 | ICAO Communications Panel first meeting (CP/1, 22 Feb-11 Jul 2016): Amendment 90 to Annex 10 Vol III introduces AeroMACS SARPs (Chapter 7). AeroMACS becomes the first FCI component with published ICAO SARPs. |
| 2019 | GANP 6th edition; COMI Thread Block 1 target (from 2019): AeroMACS surface data link and ATN/IPS migration. |
| 2021 | Annex 10 Vol III Amendment (CP, March 2021 dataset): ongoing updates; LDACS SARPs development in CP work programme. |
| 2022 | AN-Conf/14 endorses TBO implementation; confirms need for FCI data link capacity (COMI-B2) for TBO-B2. |
| 2025 | Iris/Inmarsat ATN/OSI SATCOM service commenced operations (Doc 9896 §2.1.1). Block 2 SATCOM milestone reached for European ATM. |
| 2026 | Doc 9896 3rd edition (advance unedited) published; formally defines FCI in abbreviations; specifies ATN/IPS multilink and LDACS/SATCOM handover. |
| 2026+ | LDACS SARPs: target incorporation in Annex 10 Vol III pending CP completion. LDACS en-route deployment in Europe planned to commence. |
| 2030+ | Target: VDL Mode 2 no longer required as primary en-route data link in high-density airspace; LDACS + AeroMACS + SATCOM form the complete FCI stack. |
Operational deployment timeline
| Year | Event |
|---|---|
| 2000-2010 | VDL Mode 2 deployed in Europe (SITA/ARINC networks) and the US. FANS-1/A SATCOM deployed on long-haul oceanic routes. |
| 2010-2015 | VDL Mode 2 congestion becomes measurable in European upper airspace (Brussels/Maastricht UIR). SESAR i4D trials begin using ATN B2 over VDL M2. |
| 2015-2020 | AeroMACS trials at European airports (Frankfurt, Vienna, Amsterdam). Proof of concept for broadband surface communications. |
| 2019-2023 | SESAR LDACS flight trials (in European airspace). Demonstration of ATN/IPS data link over LDACS at realistic traffic densities. EUROCAE WG-82 LDACS MOPS development. |
| 2025 | Iris ATN/OSI SATCOM commences operations. First operational use of SATCOM for ATN-based CPDLC in European oceanic airspace. |
| 2025-2028 | Target: AeroMACS operational at first major European airports (Block 1 completion). LDACS pilot deployment at selected en-route sectors. |
| 2028-2031 | Target: LDACS initial operational capability at scale in high-density European airspace (Block 2). Iris ATN/IPS migration. Full multilink operation in European FIRs. |
| 2031+ | Target: global FCI deployment with LDACS, AeroMACS, and ATN/IPS SATCOM as the standard communications stack replacing VDL Mode 2 (Block 3 horizon). |
Key FCI documents by year
| Year | Document | Significance |
|---|---|---|
| 1997 | Annex 10 Vol III Amdt 72 | First VDL SARPs (VDL M2 foundation). |
| 2006 | Doc 9880 | ATN using ISO/OSI (ground/ground). |
| 2010 | RTCA DO-362 | Initial LDACS concept (pre-ICAO). |
| 2012 | RTCA DO-345 / EUROCAE ED-222 | AeroMACS profile. |
| 2015 | EUROCAE ED-223 / RTCA DO-346 | AeroMACS MOPS. |
| 2016 | Annex 10 Vol III Amdt 90 | AeroMACS SARPs incorporated. |
| 2016 | EUROCAE ED-227 | AeroMACS MASPS. |
| 2026 | Doc 9896 3rd edition | ATN/IPS Manual; FCI defined; multilink function specified. |
References
- Annex 10 Vol III, Amendments table — full list of amendments from 1995 to present.
- Annex 10 Vol III, Chapter 7 — AeroMACS SARPs introduced by Amendment 90 (CP/1, 2016).
- Doc 9896 (ATN/IPS Manual, 3rd edition 2026), §2.1.1 — Iris ATN/OSI SATCOM operations commenced 2025.
- Doc 9750 (GANP), ASBU COMI timeline — Block 0/1/2/3 deployment milestones (authoritative source — not in local library; see https://ganpportal.icao.int/).
- AN-Conf/14 Report (Doc 10209, 2022), Recommendation 3.1/3 — TBO and FCI data link capacity (authoritative source — not in local library).
Consolidated ICAO and authoritative external references for all files in this folder.
ICAO Annexes
- Annex 10 Vol III (Communication Systems), Chapter 3, Part I, §3.4.10 — "ATN/IPS shall be capable of supporting multilink"; Note 1 directs to Doc 9896.
- Annex 10 Vol III, Chapter 3, Part I, §3.4.9 — "The ATN shall make provisions for the efficient use of limited bandwidth subnetworks."
- Annex 10 Vol III, Chapter 6 — VDL SARPs; VDL Mode 2 and Mode 4 specifications; legacy data link baseline.
- Annex 10 Vol III, Chapter 7, §7.1 — AeroMACS definition: "A high-capacity data link supporting mobile and fixed communications on the aerodrome surface."
- Annex 10 Vol III, Chapter 7, §7.3.1-§7.3.15 — AeroMACS SARPs covering conformance, surface-only transmission, AM(R)S, priority, IP data, ATN/IPS transport, multicast, handover.
- Annex 10 Vol III, Chapter 7, §7.4.2.1 — AeroMACS frequency band 5 030-5 150 MHz in 5 MHz channel bandwidth.
- Annex 10 Vol III, Chapter 7, §7.3.2 Note 2 — AeroMACS derived from IEEE 802.16-2009; profile documents RTCA DO-345 / EUROCAE ED-222.
- Annex 10 Vol III, Amendments table — Amendment 90 (CP/1, 2016) as the adoption date for AeroMACS SARPs.
ICAO Documents
- Doc 9896 (Manual on the ATN using IPS Standards and Protocols, 3rd edition, 2026, advance unedited), Abbreviations — formal entry "FCI Future Communications Infrastructure."
- Doc 9896, Definitions — Multilink, Multilink Decision Engine, VDLM2, Vertical Handover, AGMI definitions.
- Doc 9896, Part I, §2.5.3 — Mobility and Multilink Requirements; AGMI protocol; MDE; no single point of failure.
- Doc 9896, Part I, §2.5.3.5 — multilink shall operate in compliance with SPR for each applicable airspace.
- Doc 9896, Part I, §2.5.3.6 — CM/CPDLC dialogue maintained across AeroMACS, VDLM2, SATCOM subnetwork transitions.
- Doc 9896, Part I, §2.5.3.16 — ATN/IPS Multilink Function shall be deployable with no single point of failure.
- Doc 9896, Part IV, §2.1.1 — Iris/Inmarsat SATCOM service commenced ATN/OSI operations in 2025.
- Doc 9896, Part IV, §8.1 and §8.2 — mobility and multilink background; LDACS/SATCOM handover use cases.
- Doc 9854 (Global ATM Operational Concept) — KPA framework; "management by trajectory" as the operational concept driving FCI data link requirements.
- Doc 9750 (Global Air Navigation Plan, GANP) — ASBU Thread COMI; Block 1/B2 FCI deployment milestones (authoritative source — not in local library; see https://ganpportal.icao.int/).
- Doc 9587 (Policy on Economic Regulation of International Air Transport) — business case requirements for ASBU module investment.
- Doc 9869 (Required Communications Performance, RCP) — RCP 130, RCP 240 specifications governing CPDLC transaction performance (authoritative source — not in local library).
Industry standards
- RTCA DO-345 / EUROCAE ED-222 — AeroMACS profile document; mandatory, not-applicable, and optional features from IEEE 802.16-2009 (authoritative source — not in local library).
- RTCA DO-346 / EUROCAE ED-223 — AeroMACS MOPS; minimum operational performance specification for avionics certification (authoritative source — not in local library).
- EUROCAE ED-227 — AeroMACS MASPS; minimum aviation system performance standards (authoritative source — not in local library).
External authoritative sources
- https://www.icao.int/safety/acp/pages/communications-panel.aspx - ICAO Communications Panel (CP); FCI and LDACS SARPs work programme.
- https://ganpportal.icao.int/ - ICAO GANP Portal; ASBU COMI thread with FCI deployment milestones.
- https://www.eurocontrol.int/concept/ldacs - EUROCONTROL LDACS programme; European deployment and SESAR validation.
- https://www.sesarju.eu/ - SESAR 3 JU / Digital European Sky; LDACS and AeroMACS validation results.
- https://store.icao.int/en/annex-10-aeronautical-telecommunications-volume-iii-communication-systems - Annex 10 Vol III at ICAO store.
- https://store.icao.int/en/manual-on-the-aeronautical-telecommunication-network-atn-using-internet-protocol-suite-ips-standards-and-protocols-doc-9896 - Doc 9896 ATN/IPS Manual at ICAO store.