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ACP-WGF/25 WP-04
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International Civil Aviation Organization
WORKING PAPER / ACP-WGF/25 WP-04
10/10/2011

AERONAUTICAL COMMUNICATIONS PANEL (ACP)

25th MEETING OF WORKING GROUP F

Dakar, Sénégal10-14October 2011

Agenda Item 6: / Any Other Business

SELECTION OF TECHNOLOGY FOR THE LDACS DATA LINK

(Presented by Claude Pichavant )

(Prepared by Larry Johnsson SWEDEN, Stephane Tamalet AIRBUS and Luc Deneufchatel FRANCE)

SUMMARY
The Future Communications Study (FCS) identified two candidate technologies for ground based air-ground communications, operating in the L-band (960-1164 MHz), LDACS1 and LDACS2. It was decided that because of the very challenging RF-environment, the selection would have to be based on results from tests of LDACS prototypes operating together with legacy systems operating in the band.
Note: This WP was already presented at ACP WGW04 as WP-19
(Montréal). It was felt useful to extend its distribution to ACP WG-F members
ACTION
Reinforce the necessity to finalise the agreed “two path” approach for selection of the LDACS technology, in order to fully understand the spectrum characteristics of the two LDACS candidate technologies minimising risks and ensuring an optimised and focused development of the selected LDACS system.
Stakeholders should be encouraged to make sufficient resources available to guarantee that the two LDACS options are being assessed in a sound and objective manner.

1.INTRODUCTION

1.1The ICAO work on defining a Future Communication Infrastructure (FCI) for aviation reinforced the role and need of a high-capacity and robust air-ground data link with a deterministic behaviour. Available spectrum and data link technologies were thoroughly studied.

1.2Taken into account identified constraints, it was finally concluded that the L-band (960-1164 MHz) would be the most appropriate portion of the aviation spectrum allocated for Aeronautical Mobile (R) Services (AM(R)S) for the new air-ground data link, named L-band Digital Aeronautical Communication System (LDACS).

1.3Two technologies were identified as promising candidate solutions for LDACS, but because of the harsh RF-environment in this portion of the spectrum and the extremely complex characteristics of its operational environment, it was decided that selection of the most appropriate technology must be based on results from real tests of LDACS prototypes operating in the band together with all other systems that are utilising the band today with a focus on the most challenging case that is the airborne cosite case.

1.4The ICAO ACP WGW/2 meeting in 2008 agreed that

a)since the spectrum compatibility between LDACS and other systems operating in and adjacent to the band could not be proven conclusively, final recommendations for a data link technology in the L-band could not be made;

b)continued investigations of especially spectrum compatibility should focus on “two paths” (LDACS1 and LDACS2) and eventually converge to one system; and

c)work should be carried out as soon as possible with a view to reaching a decision by 2009 in order to be able to deploy a system by 2020.

1.5This paper reinforces the necessity to finalise the agreed “two paths” approach, in order to fully assess the spectrum characteristics of the two LDACS candidate technologies minimising risks and ensuring an optimised and focused development of the selected LDACS system.

2.DISCUSSION

2.1Already when the L-band was selected for the future air-ground data link, it was known that this portion of the band is heavily utilised by legacy systems, both military and civilian. It was also recognised that the LDACS system would have to be robust enough to handle interference form, these legacy systems and still fulfil the expected requirements. Furthermore, the LDACS system would have to respect the existing legacy systems and not cause harmful interference into these.

2.2The cosite situation onboard aircraft where distances between the radios are short is the most challenging situation for LDACS operations.

2.3The agreed “two stream” work has progressed since the conclusion by ICAO ACP WGW/2. The approach is included in development activities such as the air-ground data link study by ENRI in Japan and the SESAR Program in Europe. Status was reported to the ICAO ACP WGW/3 in 2010. Ongoing initiatives have not yet resulted in sufficient data being available to support a selection of the most appropriate technology.

2.4Development of navigation services in Europe (RNP/PBN Implementing Rule etc) implies that navigation will to a great extent be based on GNSS positioning with DME/DME as aback-up positioning source. In order to get the required performance of the DME network, several new installations of DMEs will be required, thus creating more demand for frequencies in the L-band causing increased RF activities in the band.

2.5As the RF interference situation in the band intended for LDACS operation most likely will become more severe compared to the situation today, it is extra important that the agreed “two stream” approach is followed and that sound and complete assessments of both LDACS options are ensured.

2.6Furthermore the LDACS solution is expected to become the key air/ground communication enabler to support the major ATM evolutions in the coming decades. The demonstration of the robustness of the LDACS performances within the difficult RF operating environment is therefore a crucial step in the promotion of such technical solution at ICAO level.

2.7The LDACS technology selection step addressed in this WP is aiming to minimise the risk of non achieving this long term objective and to select a robust and fit to purpose solution.

3.ACTION BY THE MEETING

3.1The ACP WGF25 is invited to:

a)Note the information presented in this paper;

b)reinforces the necessity to finalise the agreed “two paths” approach, in order to fully understand the spectrum characteristics of the two LDACS candidate technologies, minimising risks and ensuring an optimised and focused development of the selected LDACS system;

c)encourage stakeholders to make sufficient resources available to guarantee that the two LDACS options are being assessed in a sound and objective manner.

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