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REPORT D 6 B-AMC Aircraft Integration and Ground Infrastructure

PROJECT TITLE: BROADBAND AERONAUTICAL MULTI-CARRIER

COMMUNICATIONS SYSTEM

PROJECT ACRONYM: B-AMC

PROJECT CO-ORDINATOR: FREQUENTIS AG FRQ A

PRINCIPAL CONTRACTORS: DEUTSCHES ZENTRUM FÜR LUFT UND RAUMFAHRT

E.V. DLR D

PARIS LODRON UNIVERSITAET SALZBURG USG A

MILERIDGE LIMITED MIL UK

DOCUMENT IDENTIFIER: D 6

ISSUE: 1.0

ISSUE DATE: 17.08.2007

AUTHOR: FREQUENTIS

DISSEMINATION STATUS: PUBLIC

DOCUMENT REF: CIEA15_EN504.10

Report number: D 6 Issue: 1.0

File: Final_D6_V10.doc Author: Frequentis

Page: I

History Chart

Issue Date Changed Page (s) Cause of Change Implemented by

Rev 01 25.05.2007 All sections New document TOC

Frequentis

Rev 02 11.07.2007 All sections DRAFT for internal review

Frequentis

Rev 03 16.07.2007 All sections DRAFT submitted to Eurocontrol

Frequentis

Rev 1.0 17.08.2007 Sections 1, 2 added, minor modifications of sections 3, 4, 5 and 6

FINAL submitted to Eurocontrol incl. received comments

Frequentis

Authorisation

No. Action Name Signature Date

1 Prepared M. Sajatovic 2007-07-30

2 Approved J. Prinz 2007-08-17

3 Released C. Rihacek 2007-08-17

The information in this document is subject to change without notice.

All rights reserved. No part of the document may be reproduced or transmitted in any form or by any means, electronic or mechanical, for any purpose, without the written permission of FREQUENTIS AG.

Company or product names mentioned in this document may be trademarks or registered trademarks of their respective companies.

CCMU

Dokumentenfreigabe



Page: II

Contents

1. Executive Summary.......................................................1-1

2. Introduction .................................................................2-1 2.1. Project Background ........................................................................ 2-1 2.2. Specific Context............................................................................. 2-2 2.3. Objectives of Work Package 6.......................................................... 2-2

3. B-AMC System Architecture ............................................3-1 3.1. System Architecture....................................................................... 3-1 3.1.1. Ground Sub-system � A/G Mode ...................................................... 3-1 3.1.2. Airborne Sub-system � A/G Mode..................................................... 3-3 3.1.3. Airborne Sub-system � A/A Mode..................................................... 3-5 3.2. B-AMC System Interfaces................................................................ 3-6

4. B-AMC Airborne Integration ............................................4-1 4.1. Airborne Integration � A/G Mode...................................................... 4-1 4.2. Airborne Integration � A/A Mode ...................................................... 4-3

5. B-AMC Ground Integration..............................................5-1 5.1. Ground Integration � A/G Mode ....................................................... 5-1 5.2. Ground Integration � A/A Mode........................................................ 5-3

6. References ...................................................................6-1

7. Abbreviations ...............................................................7-1

Illustrations

Figure 3-1: Ground Sub-system (A/G Mode) ...................................................... 3-1 Figure 3-2: Airborne Sub-system (A/G Mode)..................................................... 3-3



Page: III

Figure 3-3: Airborne Sub-system (A/A Mode) ..................................................... 3-5 Figure 4-1: Airborne B-AMC Integration (A/G Mode)............................................ 4-1 Figure 4-2: Airborne B-AMC Integration (A/A Mode) ............................................ 4-3 Figure 5-1: Ground B-AMC Integration (A/G Mode) ............................................. 5-1 Figure 5-2: Ground B-AMC Integration (A/A Mode).............................................. 5-3

Tables

Table 3-1: B-AMC System Interfaces................................................................ 3-6



Page: 1-1

1. Executive Summary

This deliverable "D6 � Aircraft Integration and Ground Infrastructure Considerations" is produced within "WP6 - System Implementation, Avionics and Ground Infrastructure" of the B-AMC study. It describes the airborne and ground infrastructure as required for the B-AMC system deployment and operation in the L-band. This task was conducted and mainly guided by the existing documentation of the B-VHF project, in particular [B-VHF D6] and [B-VHF D27].

Section 3 describes segments of the B-AMC system functional architecture. Separate descriptions are provided for the components of the ground sub-system operating in the A/G mode, for the corresponding airborne sub-system components, as well as for an airborne sub-system operating in the A/A mode. The B-AMC system interfaces to external airborne/ground voice and data link systems are specified along with the management interface for the B-AMC system management. With respect to A/G data link, both ATN and non-ATN interfacing options are shown. With respect to the A/A data link, the B-AMC system operating in the A/A mode is sited within generic airborne surveillance/Airborne Separation Assurance System (ASAS) architecture.

Section 4 describes some aspects of the B-AMC airborne integration. A separate analysis has been conducted for the B-AMC system operating in the A/G and A/A mode. In the A/G mode, the B-AMC airborne system is placed within the typical airborne communications architecture, comprising both voice and A/G data link. Furthermore, the options for integration of the B-AMC functional components within existing avionics are discussed. Particular attention has been paid to the possible re-using of existing radio resources, e.g. antennas, antenna diplexers, as well as to data link components like the Communications Management Unit (CMU). The B-AMC airborne architecture concept closely follows the approach adopted for other "new" aeronautical systems � e.g. integrating the higher layers of the sub-network stack within the CMU. No significant issues could be identified that would prevent such an integration.

The B-AMC radio itself could be installed as a separate box, comprising both A/G and A/A RF front ends and common lower parts of the B-AMC protocol stack (physical layer, MAC). Alternatively, the A/G part could be integrated within existing VDR units, possibly using combined VHF/L-band antennas. The B-AMC radio operating in the A/A mode interacts with external airborne ASAS/surveillance systems, but may also integrate ASAS/surveillance processing functions itself, becoming more attractive to General Aviation (GA), but also requiring an increased number of external interfaces.

Similar investigations have been conducted in Section 5 for the ground part of the B-AMC system architecture. It can be concluded that the proposed A/G infrastructure applies to all environments considered for the future B-AMC deployment (APT/TMA/ENR). However components with reduced functionality may be sufficient in the APT environment where no wide area coverage requirements apply. The required GNI functionality and complexity may be significantly reduced if no voice option is required.

With respect to the A/G data link service provision, the GNI would be attached to an A/G ATN router that in turn is connected to both ATS and AOC data link systems. The B-AMC system would appear as any other existing ATN sub-network, but with improved capacity and performance. Similar integration concepts would apply with respect to the B-AMC integration within the IP-based end-to-end data link framework.

----------- END OF SECTION -----------



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2. Introduction

This section provides an overview of the B-AMC project background, project specific context and in particular the goals of "WP6 � System Implementation, Avionics and Ground Infrastructure".

2.1. Project Background

The frequency band currently used for air � ground communications (117.975 � 137.000 MHz) is becoming congested. In some parts of Europe, it is extremely difficult to find a frequency to allow an assignment to be made. With the predicted increase in the number of flights, this situation will get worse. Although there is a programme in place to alleviate this problem by reducing channel spacing in the band from 25 kHz to 8.33 kHz, the relief that it will provide in terms of enabling the required assignments to be made will not satisfy demand in the long term. In addition to voice communications, future Air Traffic Management (ATM) concepts will require a much greater use of data communications than is employed in the current system.

The International Civil Aviation Organisation (ICAO), through its Aeronautical Communications Panel (ACP), is seeking to define a Future Communication System (FCS), to support ATM operations. In response, the Federal Aviation Administration (FAA) and EUROCONTROL initiated a joint study, with support from the National Aeronautics and Space Administration (NASA) and United States (U.S.) and European contractors, to investigate suitable technologies and provide recommendations to the ICAO ACP Working Group T (WG-T). The first stage of the study was to conduct technology pre-screening. More than 50 candidate technologies were assessed as part of the pre-screening activity. Some of those technologies will be carried forward to the next stage, which is to perform an in-depth analysis to identify those technologies that will meet the functional, performance and operational communications requirements of a future ATM system. These technology investigations will conclude in Q3 2007.

Within Europe, the ACP members agreed to adopt a two step approach to technology selection. Step 1 was to identify potential technologies, based upon their ability to meet a subset of the criteria contained in the EUROCONTROL / FAA Communications Operating Concept and Requirements document [COCRv2]. In Step 2, additional considerations / investigations addressing the concerns covered by the other initial selection criteria will be applied to the Step 1 selected technologies, aiming to produce a further short list and recommendations for implementation.

The FCS will be the key enabler for new ATM services and applications that will bring operational benefits in terms of capacity, efficiency and safety. The FCS will support both data and voice communications with an emphasis on data communications in the shorter term. It must support the new operational concepts, as well as the emerging requirements for communications of all types (both voice and data) with a minimum set of technologies deployed globally. The FCS will incorporate new technologies as well as the legacy systems that will continue to be used.

This project, of which this report is part, will contribute to the ongoing work of FCS investigations by providing an in-depth evaluation of one of the technologies carried forward from the Step 1 activity. The technology under consideration is Broadband � Very High Frequency (B-VHF).



Page: 2-2

2.2. Specific Context

The B-VHF project was a research project co-funded by the European Commission 6th Framework Programme. The project investigated the feasibility of a new multi-carrier-based wideband communication system to support aeronautical communications, operating in the VHF communication band. The B-VHF project has completed a substantial amount of work in developing and designing the system for operation in the VHF band. However, the "overlay" implementation option is only considered feasible when spending considerable effort on implementing the techniques for interference suppression and mitigation. For that reason, the investigation is now considering the implementation of a similar technology but in a different band. The candidate bands are:

! VHF navigation band: [112 or 116] � 118 MHz

! L band: 960 � [1024 or 1164] MHz

! C band: [5030 or 5091] � 5150 MHz

Each of the above bands is already being used by other systems. Therefore, detailed compatibility analyses between the new and existing systems must be the undertaken.

The B-AMC project will evaluate the possibility of implementing a system using similar technology to B-VHF but in the L-band of 960 � 1164 MHz. The generic name given to the system is Broadband - Aeronautical Multi-Carrier Communication (B-AMC).

At the project kick-off meeting, EUROCONTROL suggested that Work Package 1 (WP1) of this project should investigate three options with regard to the spectrum that could be used for the B-AMC technology.

! Option 1 - study the feasibility of utilising spectrum between successive Distance Measuring Equipment (DME) channels for B-AMC. This would allow for B-AMC frequency planning that is "independent" from DME planning. If "enough" spectrum is available, the B-AMC would be deployed as an inlay system in the L-band.

! Option 2 - if Option 1 proves to be not feasible, study the feasibility of assigning frequencies to B-AMC channels in areas where they are not used locally by DME. This would require the establishment of a relationship between potential B-AMC assignments and existing DME assignments.

! Option 3 - if neither Option 1 nor Option 2 proves to be feasible, investigate the feasibility of utilising the lower part of the band (960 � 978 MHz) for B-AMC, considering potential interference to the Global System for Mobile communications (GSM), which is operated in the lower adjacent band.

2.3. Objectives of Work Package 6

This deliverable "D6 � Aircraft Integration and Ground Infrastructure Considerations" is produced within "WP6 - System Implementation, Avionics and Ground Infrastructure" of the B-AMC study. The main objective of WP6 is to produce a description of the airborne and ground infrastructure - based on the output of the B-VHF project - as required for the B-AMC system in the L-band, taking constraints of existing airborne and ground architectures into account. This task is aiming to identify any major obstacles to a further consideration of the system rather than providing a complete analysis.

----------- END OF SECTION -----------



Page: 3-1

3. B-AMC System Architecture

3.1. System Architecture

This section describes elements of the B-AMC system functional architecture as well as the external system interfaces. Separate descriptions are provided for the ground sub-system operating in the A/G mode, for the corresponding airborne sub-system, as well as for an airborne sub-system operating in the A/A mode.

3.1.1. Ground Sub-system � A/G Mode

The expected ground B-AMC system components are shown in Figure 3-1. The meaning of the B-AMC functional blocks is the following:

! G_TX/RX - ground B-AMC transmitter and receiver

! GSC - ground station controller

! GNI - ground network interface

! G_Voice Unit � optional functional block containing the vocoder1

Figure 3-1: Ground Sub-system (A/G Mode)

Moreover, Figure 3-1 depicts the external functional blocks that directly interface with the Ground B-AMC system:

! ATN BIS (ground boundary router)

! Non-ATN data link system2 (optional)

1 The B-VHF system and also the B-AMC system aim to re-use the vocoder selected/validated for VDL Mode 3. 2 The non-ATN interface is optional (inherited from the B-VHF design). If all air-ground data link services are deployed over OSI- or IP ATN solution, this interface can be omitted.

B-AMC A/G

Ground Sub-system

g4

R1

g2

GNI G_Voice Unit

GSC

G_Voice System

ATN BIS

B-AMC Mgmt.

Non-ATN DLS

B-AMC G_TX/RX

g3

g1



Page: 3-2

! Ground voice system (optional)

! B-AMC management system

NOTE: Other ground data link components that are external to the B-AMC system, like ground ATN routers, ATN end-systems, data link applications processors or HMIs, are not shown.

The B-AMC ground infrastructure providing regional coverage comprises a number of B-AMC Ground Stations (GS). Each GS comprises physical B-AMC radio units (TX and RX) and the Ground Station Controller (GSC) that is connected to the Ground Network Interface (GNI).

The physical radio units (TX, RX) comprise the B-AMC Physical Layer (PHY) and the parts of the DLL layer (MAC sub-layer). Due to the required close co-operation between the PHY layer and the MAC sub-layer, it is not advisable to separate these entities. They should be rather kept both within a single physical unit. The management of the underlying physical resources (OFDM carriers), modulation, interleaving, frame synchronisation, Forward Error Correction (FEC), coding, provision and maintenance of the system timing and other PHY aspects are assigned to the physical radio units.

In order to support seamless handover between cells, transmitters of all GSs must be precisely synchronised to each other. The TX acts as timing master for the entire aircraft population within a cell and has to implement either a precise local timing source or to provide an interface to an external timing source (e.g. GPS). This is considered to be a local implementation issue. Therefore the timing interface has not been shown in Figure 3-1.

The GSC implements the DLL layer components above the MAC sub-layer and provides local support for voice operation, if voice channels are configured (e.g. local re-transmission within a party-line). As a minimum, the GSC has to implement the B-AMC Specific Services (BSS) sub-layer and a part of the Link Management Entity (LME) functionality that is required for the operation on the single RF channel. The required GSC functionality comprises support for the Net Initialisation, Initial Net Entry, Forced Handover and Seamless Handover procedures, as well as for reservation-based resource requests, including support for on-demand voice services and circuit-mode data link services (Link Establishment/Release).

The GSC takes care about the logon/logoff of an aircraft within a given cell (during the Initial Net Entry or handover procedures) and notifies the GNI about any A/C connectivity changes. The GSC maintains a local data base with ICAO addresses and Local IDs of all aircraft that are connected to that GS. This information is updated once a new aircraft enters or leaves the cell, as well as after a handover to/from another cell.

The GNI implements functions dealing with multiple cells and multiple frequencies and is therefore particularly involved with the GS switchover during handover procedures (as each cell operates on a dedicated frequency, this LME part cannot be included in the GSC). In particular, the GNI will be involved with managing the handovers between B-AMC cells. It will co-ordinate, schedule and re-direct existing voice and data link connections between a given cell and the specific aircraft to another cell operating on a different frequency, without loss of voice or data frames.

The GNI has a central repository with ICAO addresses (and Local IDs) of all aircraft that are logged on any of the attached GSs. This information is updated once a new aircraft entry/exit to/from the local B-AMC system, as well as after a handover between cells.



Page: 3-3

The repository of the unique ICAO addresses is used in all cases where a unique airborne B-AMC system identifier is required, e.g. when co-ordinating handovers with other GSCs.

NOTE: The mapping of the ICAO addresses to Local IDs may be implemented independently at each GSC, centrally at the GNI, or at both. The best option has to be selected yet.

The GNI implements the B-AMC sub-network layer functions and interfaces with an external ATN router. The GNI is responsible for preserving the sub-network data link connections during handovers. As long as the adjacent cell is attached to the current GNI, the GNI will just re-direct the existing connections to the new cell, but will not report the connectivity change to the ATN router. This procedure will avoid unnecessary management exchanges between an airborne and the ground ATN router. The GNI also provides support for non-ATN data link services (e.g. FL broadcast, downlink of A/C parameters) and implements interfaces to the (local) non-ATN ground DLSs that are provider or user of such data.

The GNI interfaces with the external VCS and accepts both traditional PTT and extended voice signalling.

NOTE: A Voice Unit is necessary for the B-AMC voice sub-system operation. Dependent on the selected overall GND architecture, it may be integrated within the B-AMC GNI, or within the ground voice system that is external to B-AMC system. If no voice channels are configured, this unit can be completely omitted.

Finally, the GNI provides an interface and implements functions necessary for B-AMC management, providing the access to all B-AMC resources (GSC, B-AMC radios) within an entire region.

3.1.2. Airborne Sub-system � A/G Mode

An airborne B-AMC sub-system operating in the A/G mode (Figure 3-2) comprises the following generic functional blocks:

! A_TX/RX - airborne B-AMC transmitter and receiver

! ANI - airborne network interface

! A_Voice Unit � optional functional block containing the vocoder3

Figure 3-2: Airborne Sub-system (A/G Mode)

3 The B-AMC system uses the vocoder that was selected for VDL Mode 3.

B-AMC A/G Air Sub-system

a3

R1

Non-ATN Avionics

ATN Avionics

Radio Control

A_Voice System

A_Voice Unit

B-AMC A_TX/RX

ANI C1 a1

a2



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These entities logically interact with external components:

! Radio control

! Airborne voice system (optional)

! ATN data link system

! Non-ATN data link system4 (optional)

These logical blocks do not imply any particular physical implementation. Several functional blocks may be combined within a single physical unit. A single function may be implemented through multiple units. In particular, the airborne network interface (ANI) will not exist as separate physical entity. Its functions will be distributed between the physical radio unit and the (external) ATN/Non-ATN data link function.

NOTE: The Airborne Voice Unit is expected to be integrated within the airborne B-AMC radio unit.

The roles of airborne B-AMC components are similar to their ground counterparts.

The airborne B-AMC radio in the A/G mode comprises the Physical Layer and the MAC sub-layer of the B-AMC protocol stack.

NOTE: The lower parts of the B-AMC protocol stack are different for A/G mode and A/A mode.

Each radio autonomously maintains a reference timing obtained from its controlling GS (as precise alignment with the GS timing is required for synchronous RL transmissions).

The radio also implements DLL layer functions above the MAC sub-layer that are required to support voice operations. As a minimum, the B-AMC radio has to implement the BSS sub-layer and that part of the LME functionality, which provides support for the Net Initialisation, Initial Net Entry, Forced Handover and Seamless Handover procedures, as well as for reservation-based resource handling.

The radio maintains a local data base with the B-AMC system configuration information that is relevant to that radio. The information is submitted by the GS during the Net Initialisation procedure. The radio is directly involved with all types of handovers between cells. In case of a seamless handover it co-ordinates the handover with the GS and re-directs the existing voice and DL connections to the adjacent cell operating on a different frequency, without loss of voice or data frames.

The radio takes care about the logon/logoff within a given cell (during Initial Net Entry or handover procedures) and notifies the ANI (implemented in the Communication Management Unit (CMU)) about connectivity changes. The ANI decides whether these reports shall be forwarded to the airborne ATN router (implemented within the CMU) or not (in case that the changes can be handled within a sub-network, being transparent to the router).

The ANI also provides support for non-ATN data link services (e.g. FL broadcast, downlink of A/C parameters) and will provide interfaces to the (local) non-ATN airborne data link systems that are provider or user of such data.

4 The non-ATN interface is optional (inherited from the B-VHF design). This interface can be omitted if all air-ground data link services could be deployed by using OSI- or IP ATN solution).



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3.1.3. Airborne Sub-system � A/A Mode

An airborne B-AMC sub-system operating in the A/A mode (Figure 3-3) comprises only the single generic functional block:

! A_TX/RX - airborne B-AMC transmitter and receiver

This entity logically interacts with external components:

! Radio control

! GNSS timing source

! ASAS/Surveillance processing system

! Cockpit Display of Traffic Information (CDTI, optional)

Figure 3-3: Airborne Sub-system (A/A Mode)

NOTE: The lower parts of the B-AMC protocol stack are different for A/G mode and A/A mode. As no subnetwork layer exists in the A/A mode, the entire B-AMC A/A functionality is allocated to the radio unit.

Each radio autonomously maintains the reference timing obtained from the local GNSS source, because precise timing is required for A/A transmissions.

NOTE: As with the B-VHF concept, an airborne B-AMC radio in the A/G mode derives its timing from the controlling GS.

The radio maintains a local data base with information about the Common Communications Channel (CCC) usage that is relevant to that radio. The information is collected from other CCC users during the Net Initialisation procedure. The radio uses the occupancy tables from this data base when selecting the time slots for its own transmissions.

The radio also implements DLL functions above the MAC sub-layer that are required to support A/A operations. As a minimum, the B-AMC radio has to implement the FEC algorithms required for achieving integrity for broadcast data.

The radio exchanges data with the external ASAS/Surveillance processing system. It acts as an ADS-B transmit sub-system and implements ADS-B/TIS-B receiving functions.

NOTE: In some implementations, these external ASAS/SUR functions may be implemented within the B-AMC radio, with modified wiring and modified external interface A2.

Assuming that addressed A/A data link would be used in support of ASAS operations, an HMI would be required to select/address another aircraft. An airborne CDTI becomes a logical candidate for such an interface. Therefore, an optional interface may be required

B-AMC A/A Air Sub-system CDTI

ASAS / SUR_P

R2

GNSS Time

A2 A1

A3

Radio Control

C1

B-AMC

A_TX/RX



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between an airborne B-AMC radio in the A/A mode and the CDTI unit (shown in Figure 3-3).

3.2. B-AMC System Interfaces

Table 3-1 shows all external interfaces of the B-AMC system, including both A/G and A/A mode.

Interface Description

R1 B-AMC air interface used in A/G mode

R2 B-AMC air interface used in A/A mode

A1 Interface to the local timing source (used only in A/A mode)

A2 Interface to the airborne ASAS/surveillance processing function (A/A mode)

A3 Interface to the airborne CDTI function (A/A mode, optional)

C1 Airborne radio control interface (A/G and A/A mode)

a1 Interface to the airborne ATN data link avionics (CMU/ATSU), used in A/G mode

a2 Interface to the airborne non-ATN data link avionics (A/G mode, optional)

a3 Interface to the airborne voice system (A/G mode, optional)

g1 Interface to the ground ATN BIS (A/G mode)

g2 Interface to the B-AMC management (A/G mode)

g3 Interface to the ground non-ATN data link system (A/G mode, optional)

g4 Interface to the ground voice system (A/G mode, optional)

Table 3-1: B-AMC System Interfaces

----------- END OF SECTION -----------



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4. B-AMC Airborne Integration

4.1. Airborne Integration � A/G Mode

Today, multiple airborne architecture solutions are in place, with significant differences between large transport aircraft, business aircraft and low-end general aviation (GA) aircraft. Moreover, there are also significant differences between architecture concepts of large aircraft manufacturers. Despite such differences, the simplified architecture illustrated in Figure 4-1 is regarded as generally applicable to the ATN-capable transport aircraft population and, with some modifications, may be applicable to the business- and GA population.

Figure 4-1: Airborne B-AMC Integration (A/G Mode)

Figure 4-1 shows two VHF radios (VHF1 and VHF3) and one B-AMC radio (B-AMC).

NOTE: Normally, the third VHF radio (VHF2) and further communication/navigation radios (e.g. HF, SATCOM, DME, or VOR) are installed as well, but they are not shown in Figure 4-1.

VHF radios are wired to the airborne Audio Management Unit (AMU). In order to be usable in the voice mode, the airborne B-AMC radios would have to be connected to the AMU. Moreover, for interoperability and compatibility reasons, this voice interface should correspond to the ARINC 750 specification (the digital voice unit should be implemented within the B-AMC radio).

B-AMC is capable of supporting ATN functionality. Hence, a CMU/ATSU unit is shown in Figure 4-1. The CMU is connected to various other systems like the Flight Management



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System (FMS), the Central Maintenance Computer (CMC), the Aircraft Condition and Monitoring System (ACMS), etc.

The CMU has direct interfaces to Printer and Multi-purpose Control and Display Units (MCDU) and in addition, on new Airbus aircraft, to Dedicated Control and Display Units (DCDU). The MCDU is used to communicate with multiple systems such as CMU, FMS, SATCOM etc. but only one is actively used at any time. It is also used as an HMI for AOC data link services.

The CMU internally comprises an ATN A/G BIS router and normally hosts higher sub-layers of different data link sub-network protocol stacks. The CMU acts as an end system for ATS and AOC data link services and as an airborne router for other onboard end systems like the Flight Management System (FMS).

NOTE: In some airborne architectures the CMU remains to be a router, while the FMS may implement an end system for AOC or ATS services.

To facilitate equipment certification, it is recommended that two physical units � the existing CMU and the B-AMC multimode transceiver � shall be used to accommodate all functions required for the B-AMC operation. Therefore, parts of the B-AMC data link protocol stack (e.g. the DLS sub-layer, sub-network layer) may be delegated to the CMU.

The CMU may be able to provide support for non-ATN data link services (e.g. FL broadcast or downlink of aircraft parameters). Alternatively, these operational services may be implemented within other avionics units (e.g. FMS), with an additional interface to the B-AMC radio unit.

An airborne B-AMC radio in the A/G mode operates as a full-duplex unit, comprising receiver and transmitter front-ends that operate on different RF channels. These front-ends must be sufficiently de-coupled from the same airborne platform for independent transmit/receive operations.

NOTE: If deployed as a stand-alone unit, the B-AMC airborne radio could comprise both A/G and A/A RF front ends � using separate antennas - and common lower parts of the B-AMC protocol stack (physical layer, MAC). Sharing the same radio hardware and antennas between A/G and A/A mode requires further detailed investigations.

When B-AMC TX and RX front-ends are using the same L-band antenna, an RF diplexer unit is required to provide the required TX/RX de-coupling. Such a diplexer (Figure 4-1) is functionally a part of the B-AMC airborne radio, but may be installed as a separate physical unit. With a diplexer, a B-AMC radio in the A/G mode could use a single L-band antenna or a switchable antenna pair (top or bottom-mounted antennas) that would have to be installed for the B-AMC system additionally. An antenna switch (not shown in Figure 4-1) would be required as well.

NOTE: If two separate L-band antennas could be made available to the B-AMC TX and RX, respectively, a combination of the TX and RX band-pass filters could be used instead of the diplexer. The TX filtering equipment would reduce the out-of-band noise and spurious products of the TX that may fall into the RX bandwidth. The RX filter would prevent the TX power contained within the �B-AMC occupied bandwidth� to reach the RX input circuitry.

The diplexer or filtering equipment described above would allow for an undisturbed operation of the B-AMC RX when the B-AMC TX transmits. However, [B-AMC D4] indicates that an airborne reception of the B-AMC RX would be jammed each time one of other non-B-AMC airborne L-band systems on the same aircraft starts to transmit.



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Moreover, when the B-AMC TX starts to transmit, other L-band receivers would be jammed, due to the very limited isolation between antennas. Therefore, the B-AMC airborne system operating in the A/G mode � as other L-band systems � should be attached to the suppression bus (shown in Figure 4-1). This bus is used by the attached L-band TXs to advertise their intentions to transmit. Based on that information, other TXs may then decide to delay their own transmissions. Attached L-band receivers can benefit from this information as well, e.g. use it to protect their input RF circuitry from prohibitive high received power levels.

Some antenna vendors already advertise multi-range VHF/L-band antennas (e.g. Sensor S65-8282-127 model) to be used as a replacement for the existing antennas in cases where multi-range capability is required. This offers potential for the B-AMC airborne radio to share the same antenna with the VHF radio (Figure 4-1). Independent operation of both radios would require additional investigations of the interference impact between the radios.

NOTE: Assuming that the VHF3 and the B-AMC radio are used in an exclusive mode (only one data radio is actively used at any time) for data-only purpose and are attached to the same combined antenna, no interference risk between these radios would arise any more.

Finally, assuming further progress in RF technology within the next years, it may be possible to integrate the B-AMC radio in the same package with the existing VHF radio (shown as yellow box in Figure 4-1). By extending the existing VDR standard, B-AMC would become another mode of a multi-mode VDR radio. At the same time, the number of external radio interfaces and the corresponding wiring effort would be significantly reduced.

4.2. Airborne Integration � A/A Mode

Currently, no common airborne architecture with respect to A/A data link is available. The simplified architecture from Figure 4-2 is expected to be applicable for both transport aircraft and GA population.

Figure 4-2: Airborne B-AMC Integration (A/A Mode)



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The B-AMC transceiver operating on a dedicated CCC provides basic ADS-B transmit/receive functionality. Dependent on the applicable safety requirements, it may has to be doubled. In Figure 4-2 a single unit is shown.

The B-AMC transceiver requires a precise timing (provided by GNSS) and it is wired to the airborne navigation system (NAV). In order to provide an A/A addressed data link, the B-AMC transceiver would have to be connected to an appropriate interface (in Figure 4-2, the CDTI is assumed to be usable for that purpose).

In large transport aircraft architectures the B-AMC transceiver would be wired to another unit (ASAS/SUR) that performs ASAS processing and surveillance transmit processing. This unit is external to the B-AMC system and in turn is connected to multiple external systems (FMS, Flight Computer, NAV, CDTI, other airborne data sources).

In GA architectures, the ASAS/SUR functionality as well as the CDTI may become integrated within the B-AMC unit itself. In that case, all external interfaces between the ASAS/SUR unit and other avionics items would have to be implemented at the B-AMC unit.

The B-AMC radio in the A/A mode operates as a simplex unit, comprising receiver and transmitter front-ends that operate in an exclusive way on the same RF channel (CCC) and are connected to the same antenna. Therefore, an RF TX/RX switch must be implemented as a part of the B-AMC airborne radio.

The B-AMC radio in the A/A mode, including the TX/RX switch, could use a single dedicated L-band antenna or a switchable antenna pair (top or bottom-mounted antennas) that would have to be installed for that purpose. An antenna switch (not shown in Figure 4-2) would be required as well.

However, in order to reduce the number of required antennas, the B-AMC A/A radio could adopt the same approach that was proposed for an UAT transceiver: to share an existing L-band antenna with the SSR transponder. This should be possible as the B-AMC A/A mode CCC is anticipated to be allocated close (968 MHz) to the UAT allocation (978 MHz).

In such a case an additional diplexer would be required (Figure 4-2), providing common antenna port and separate ports to the SSR transceiver/B-AMC transceiver with sufficient isolation between these ports.

For the same reasons described in section 4.1 for the airborne B-AMC system in the A/G mode, the B-AMC airborne system operating in the A/A mode should also be attached to the suppression bus (shown in Figure 4-2).

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5. B-AMC Ground Integration

5.1. Ground Integration � A/G Mode

Opposite to an optional deployment of the ground B-AMC infrastructure in the A/A mode, (Figure 5-2) the ground infrastructure in the A/G mode (Figure 5-1) is mandatory. This infrastructure applies to all environments envisioned for the B-AMC deployment. Reduced functionality of some components (GNI) may be sufficient in the APT environment if no wide area coverage is required. The required GNI functionality/complexity may be further reduced if no voice option is needed.

The required ground components comprise the GS equipment (physical B-AMC TX and RX, GSC) and the GNI.

Figure 5-1: Ground B-AMC Integration (A/G Mode)

The GNI manages the connectivity changes within the B-AMC sub-network due to aircraft mobility, in particular seamless handoffs between multiple GSs that provide a given communications service within some area. The connectivity changes due to transparent handovers between the B-AMC cells are not reported to the B-AMC sub-network protocol.

The GSCs of such GSs are attached to the GNI via ground networks. The GNI itself can be placed at any appropriate position, but it is expected that it would be deployed at the ATS facility. The GNI provides an interface to the B-AMC management system.

If the voice option is used, the GNI must be connected to the ground voice system (VCS) of the corresponding ATS facility. If the AOC voice option is used, an external AOC VCS (not shown in Figure 5-1) would access the GNI either directly via ground network, or indirectly via the ATS VCS. As long as only the basic voice functions are used (no selective voice, no advanced voice signalling), voice units could be implemented within the GNI. Hence, no changes would be required at the VCS side. With advanced voice features, moderate VCS modifications would be required.



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With respect to the A/G data link service provision, the GNI would be attached to an A/G ATN router that in turn is connected to both ATS and AOC data link systems. In such a case, the router has to support the new B-AMC sub-network protocol in parallel with existing ones. This may require in particular modifications of the Sub-Network Dependent Convergence Facility (SNDCF). Except for the improved communications performance, the B-AMC sub-network would otherwise behave within ATN like any other sub-network.

Similar provisions would be required in case of an IP-based end-to-end solution. Like the ATN case, the aircraft mobility would be managed within the B-AMC network itself and the connectivity changes due to transparent handover between the B-AMC cells would not be reported to the IP-equivalent of the ATN SNDCF.

Optionally, the GNI may use a direct connection to the ATS data link system � this may be necessary for ATS services with stringent timeliness requirements that probably would not be able to use end-to-end connectivity provided by the ATN.

If the B-AMC system is configured for data-only operation, the required GNI functionality will reduce, so there may be some limited potential for integrating the GNI mobility-management functions within the A/G router (Figure 5-1) while moving other GNI functions to the GSCs of the attached GSs. However, as the GNIs may have to be doubled, and normally multiple GNIs would be attached to the same router, such an approach may jeopardise the router performance and would require further detailed investigations.

The GSC component is involved with resource reservation and management. As these functions are time-critical, additional ground delays could jeopardise the system performance. Therefore, the GSC should be placed on site, as close as possible to the physical B-AMC ground TX and RX.

The B-AMC ground radio in the A/G mode operates as a full-duplex unit, comprising receiver and transmitter front-ends that operate on different RF channels. These front-ends must be sufficiently de-coupled for independent transmit/receive operations from the same ground location. If two separate L-band antennas are available to the B-AMC TX and RX, respectively, a combination of TX and RX band-pass filters will be used. Assuming the single antenna, TX/RX de-coupling would be provided by an RF diplexer unit (not shown in Figure 5-1).

Opposite to airborne B-AMC radios that may be tuned to any B-AMC channel, the ground B-AMC radios are basically single-channel equipment (once the channel is allocated, it would be permanently used). If the allocated channel should change (this should not happen frequently), the single-channel operation would again apply after such a change.

No potential (and no need) is seen for an integration of ground B-AMC radios with existing ground radios. However, the costs of the ground B-AMC infrastructure would be significantly reduced if the B-AMC ground radios were deployed at existing VHF COM sites. Due to the large frequency separation, the on-site de-coupling of B-AMC and VHF radios should be feasible.

NOTE: The TX filtering equipment should be used for reducing the out-of-band noise and spurious products of the B-AMC TX that may fall into the RX bandwidth of the VHF COM receiver, the B-AMC RX filter should prevent the main VHF COM TX power to reach the B-AMC RX input circuitry. Additional isolation could be achieved by the careful on-site placement of L-band and COM antennas.

Due to the possibly smaller size of the B-AMC cell compared to the ENR VHF GS coverage additional B-AMC GSs may be required for providing seamless B-AMC ENR coverage.



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At least some of such additional ground B-AMC TX/RX could be placed at existing DME sites (additional filtering equipment may have to be installed on site). DME ground equipment is also a single-channel equipment. DME TX and RX operate on RF channels separated by 63 MHz, but use the same ground antenna. Necessary DME TX - RX isolation is achieved by deploying an antenna switch [B-AMC D1]. With good engineering practices and sufficient frequency spacing between B-AMC and DME FL/RL channels (the amount of such spacing would depend on the DME mode) it may be possible to achieve sufficient isolation between both radios for an interference-free operation.

5.2. Ground Integration � A/A Mode

For B-AMC operation in the A/A mode on the CCC there is an option to deploy ground B-AMC radios for both monitoring airborne A/A transmissions and/or uplink provision of TIS-B information. In such a case a simple ground architecture applies (Figure 5-2). This architecture applies to all environments if ground participation (e.g. ground-to-air broadcast) or monitoring of B-AMC A/A communications (e.g. for ground surveillance purposes) is required.

Figure 5-2: Ground B-AMC Integration (A/A Mode)

The GS with the GSC and at least the B-AMC ground radio capable of receiving in the A/A mode are required. The transmitting radio is optional; it may be combined with the receiving radio (transceiver). The GSC would implement the required network protocols and functions (e.g. router), acting as a node on the ground data network (e.g. surveillance network). The GSC would become attached to the ATS surveillance processing system (SUR in Figure 5-2) via the ground network or to the TIS-B server (TIS in Figure 5-2). The GSC would transform the received B-AMC data formats to the standard formats adopted for the ground surveillance networks (e.g. ASTERIX). The GNI is not required in the A/A configuration. The GSC would also provide the management interface allowing for remote configuration and monitoring of the GSC itself as well as B-AMC ground radios attached to the GSC.



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In order to reduce deployment costs, it is recommended to install such ground B-AMC stations at existing sites. In particular, pure receiving sites could be co-located with VHF COM receiving sites.

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6. References

Reference Description

[B-AMC D1] B-AMC Report 1 � DME Spectrum Characterisation and L-band Spectrum Availability for an OFDM-like System, Issue 1.0, Aug. 2007

[B-AMC D2.1] B-AMC Report 2.1 - B-AMC System High Level Description, Issue. 1.0, Aug. 2007

[B-AMC D4] B-AMC Report D4 - B-AMC Interference Analysis and Spectrum Requirements, Issue 1.0, 22.08.2007

[B-VHF D6] B-VHF Functional Principles and Architecture, Issue 1.0, 05.04.2005

[B-VHF D27] B-VHF Deployment Scenario, Rev. 1.0, 03.10.2006

[COCRv2] EUROCONTROL/FAA Future Communications Study, Operational Concepts and Requirements Team, Communications Operating Concept and Requirements for the Future Radio System, Version 2, May 2007.

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7. Abbreviations

A/A Air-air

A/G Air-ground

A_RX Airborne Receiver

A_TX Airborne Transmitter

ACMS Aircraft Condition and Monitoring System

ADS-B Automatic Dependent Surveillance - Broadcast

AMU Audio Management Unit

ANI Airborne Network Interface

AOC Airline Operational Communications

APT Airport

ARINC Aeronautical Radio INCorporated

ASAS Airborne Separation Assurance System

ASTERIX All-purpose STructured EUROCONTROL Radar Information eXchange

ATN Aeronautical Telecommunications Network

ATS Air Traffic Services

ATSU Air Traffic Services Unit

B-AMC Broadband Aeronautical Multi-carrier Communications

BIS Boundary Intermediate System

BSS B-AMC Special Services

CCC Common Communications Channel

CDTI Cockpit Display of Traffic Information

CMC Central Maintenance Computer

CMU Communications Management Unit

COM Communications

DCDU Dedicated Control and Display Unit

DL_ES Data Link End System

DLL Data Link Layer

DLS Data Link Services

DME Distance Measuring Equipment

ENR En-route

FEC Forward Error Correction

FL Flight Level

FL Forward Link

FMS Flight Management System



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G_RX Ground receiver

G_TX Ground transmitter

GA General Aviation

GND Ground

GNI Ground Network Interface

GNSS Global Navigation Satellite System

GPS Global Position System

GS Ground Station

GSC Ground Station Controller

HF High Frequency

HMI Human Machine Interface

LME Link Management Entity

MAC Medium Access Control

MCDU Multi-purpose Control and Display Unit

NAV Navigation

OFDM Orthogonal Frequency Division Multiplexing

PHY Physical Layer

PTT Push to Talk

RF Radio Frequency

RL Reverse Link

RX Receiver

SATCOM Satellite Communications

SNDCF Subnetwork Dependent Convergence Facility

SSR Secondary Surveillance Radar

SUR Surveillance

SUR_P Surveillance Processing

TIS-B Traffic Information Service � Broadcast

TMA Terminal Manoeuvring Area

TX Transmitter

UAT Universal Access Transceiver

VCS Voice Communications System

VDL VHF Digital Link

VDR VHF Data Radio

VHF Very High Frequency

VOR VHF Omni-directional Range

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