International Civil Aviation Organization

World-wide CNS/ATM Systems

Implementation Conference

Rio de Janeiro, 11 – 15 May 1998

WW/IMP-WP/38

11/5/98

Item 1

Agenda Item 1:	Overview of CNS/ATM systems implementation

ATN: SYSTEMS STATUS AND STANDARDIZATION IN PROGRESS

(Presented by the Secretariat)

INFORMATION PAPER

1.	Introduction

1.1	This paper presents the current status of the process of standardization of the aeronautical telecommunication network (ATN) in ICAO. The paper also provides a brief summary of the technical provisions already developed for the ATN.

2.	The ATN Concept

2.1	The need for an international communication network supporting civil aviation activities has long been recognized. The first attempt towards such global network was the aeronautical fixed telecommunication network (AFTN) which is in wide use today. The AFTN provides for the exchange of text messages between ground facilities like air traffic control (ATC), meteorological offices and other and other aviation facilities. AFTN has been, and still is invaluable to the safety and efficiency of international civil aviation.

2.2	As air traffic grows and at the same time, demand for higher safety, efficiency and economy of flight increases, there is a need to enhance the overall aeronautical communication system so that:

a)	aircraft (in flight) can become connected to the network as well;

b)	automatic data interchange can be performed between airborne and ground systems;

c)	existing limitations in capacity, integrity and response time can be overcome; and

d)	messages other than written text can be accommodated.

The ATN has been conceived to address the above-mentioned needs.

2.3	The ATN concept defines the architecture for interconnection and inter-operability of different air-ground and ground-ground data networks. It is based on data communication standards developed by the International Organization for Standardization (ISO) and fulfils the operational requirements defined for air traffic services communications. It can also accommodate aeronautical operational control (AOC) and aeronautical administrative communication (AAC) and aeronautical passenger communications (APC).

2.4	In the data communications terminology, the term "gateway" refers to the interface between two completely dissimilar networks. In order to facilitate transition from existing AFTN to the ATN, gateways will have to be deployed allowing the transfer of a certain type of ground-ground messages between the two networks. Other types of gateway may also be developed to link other existing networks, such as those used for aircraft communications addressing and reporting system (ACARS) with the ATN.

3.	Standardization Process

3.1	The ATN concept was first developed by the Special Committee on the Future Air Navigation Systems (FANS) of ICAO. Later the task of developing the necessary technical provisions was given to an ICAO panel of experts from 20 States and 7 international organizations which is called the Aeronautical Telecommunication Network Panel (ATNP).

3.2	The ATNP has developed the first set of Standards and Recommended Practices (SARPs) for the ATN. This set, which is to be published later this year (for applicability in November 1998), has also been commonly referred to as the CNS/ATM-1 Package. The Package is produced in two parts: a "core" part which contains broad, general and mostly regulatory-type provisions, and a detailed part which contains all the necessary technical details. The core part will become part of Annex 10 — Aeronautical Telecommunications and the detailed part will be published as an ICAO manual.

3.3	The CNS/ATM-1 Package covers the following main types of provisions:

—	system level requirements;

—	system architecture; and

—	applications (protocols, message structures, etc.);

i)	air-ground applications

– Context Management (CM);

– Automatic Dependent Surveillance (ADS);

– Controller-Pilot Data Link Communication (CPDLC); and

– Flight Information Service (FIS)

ii)	ground-ground applications

– Aeronautical Interfacility Data Communication (AIDC); and

– Air Traffic Services Message Handling Services (ATSMHS).

3.4	The necessary provisions for AFTN/ATN Gateways and the use of common ICAO data interchange network (ATN) as part of the ATN are included in the CNS/ATM-1 Package. ICAO however doesn't undertake the development of provisions for gateways for interconnection of the ATN to other non-ICAO networks (like ACARS. If necessary and/or economically justified, such activities will be undertaken by service providers who run those networks.

3.5	Work is in progress to develop further enhancements to the CNS/ATM-1 Package. These enhancements, which do take into account the need for backward compatibility (with the initial CNS/ATM-1 Package), include the addition of new provisions relating to systems management, network/message security and new applications. These enhancements are expected to be finalized by the year 2000.

3.5	Supporting guidance material has also been produced to help States with their planning, implementation and operation of the ATN. Two documents entitled "Manual of the Aeronautical Telecommunication Network (ATN) - First Edition" and "A Worldwide Planning Document for the Evolutionary Development of the Data Interchange Portion of the Aeronautical Fixed Service (AFS)" have already been published by ICAO in 1991 and 1996 respectively. A comprehensive manual, containing guidance material on all aspects of the ATN, has also been developed which is currently in process for publication in 1999.

4.	Implementation Activities

4.1	Some air-ground data links such as aeronautical mobile satellite service (AMSS) and secondary surveillance radar (SSR) Mode S data links, which support data interchange in a network-like environment (i.e. a number of users with individual addresses) have already been implemented to support some initial applications like ADS and CPDLC. However, special "routers" are required, both in the air and on the ground, to select "the best route for each message" and to interconnect these individual links with other ground networks so that universal interconnectivity of all aeronautical computers can be achieved. The development of such "routers" in line with ICAO provisions is currently in progress. Also, pre-operational trials of "end systems" which contain the necessary application software, and "intermediate systems" or "routers" which perform relaying and routing functions, are being conducted in Europe and the United States.

4.2	On the ground-ground applications side, interest is being shown in several regions in the ATSMHS. Unlike AFTN which can handle rather small messages, ATSMHS can support exchange of large volumes of data. Furthermore, the message integrity (ie being free of errors) and transit time of the ATSMHS is far superior to those of the AFTN. Provisions have been included in ATN SARPs for the inter-operability of AFTN and ATSMHS via special gateways. Planning activities for the use of ATSMHS have already started in a number of ICAO regions.

4.3	The full benefit of CNS/ATM systems can only be achieved if they can truly become global and this can only be achieved by a global communication network. The ATN offers the global connectivity to the international civil aviation community while maintaining the special requirements for integrity, capacity and efficiency. It is however anticipated that the implementation of the ATN will be gradual and based on "islands" approach. Certain geographical areas like the core of Europe and the United States, which have high levels of air traffic and therefore immediate requirements for improved communications performance, may implement islands of the ATN and start reaping the promised benefits. Other parts of the world which don't have such immediate requirements may start with their implementations later. In any case, it is anticipated that ATN-related implementation activities will significantly increase in the next 2 to 3 years.

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