ATN Product "TES"

1997 Successful management of outsourced companies in product development and subsequent distribution

Background

EUROCONTROL funded the “Trials End System (TES)” project to provide a prototype ATN End System in order to validate the ATN Standards and Recommended Practices. ATN was based on the OSI 7 layer model and the TES represented the Upper Layers of the model. The TAR/TTS project provided the lower layers and routers. TES was developed by an international consortium of companies led by Thomson CSF. The aim of the ATN is to provide seamless data link communications between an aircraft and an air traffic control centre using multiple satellite providers.

Challenge

I had to provide technical expertise to advise the project manager based in Brussels, and also to the outsourced companies responsible for the development of the product. The technical solution had to validate the international standards. The product was required for use by EUROCONTROL and member states. Documentation had to be accurate and Release Notes provided. Member States needed training and support in use of the TES API in national projects.

Actions

Integrate the “TES” product into the ATN test-bed. Design and run acceptance tests. Conceive and Run pre-operational trials. Distribute TES to national administrations.

Participate in ATN Standards community. Communicate with EUROCONTROL headquarters, national administrations and outsourced supplier organisations.

Investigate new applications and enabling technologies.

Support to TES project management in Brussels.

Provide all necessary documentation, Definition, Requirements, test and validation. Review external documentation.

Release Control Management of TES.

Install and maintain the ATN test-bed in Paris.

Support Users. Deploy TES in Europe. Manage TES licenses.

Propose improvements to international standards

Specify applications to help member states in their trials projects. Provide applications as open source to aid national projects and encourage re-use of code where appropriate.

Organise User Group Meetings for International Users of TES

Result

TES was successfully used in national trials of the ATN including Germany, UK France and Italy.

TES was a key element of proving the ICAO SARPS for ATN, and therefore the subsequent adoption of ATN by all stakeholders in the ATC community.

Meaning

This was the first time I had been involved in the development of a product from initial specification to successful final use. I was involved in all stages of the project life-cycle. This was the first project of a truly international nature that I had been involved in.

Details

3.2 Trials End System

3.2.1 Introduction

The ATN End Systems task within the Communications division of Eurocontrol embraces the

delivery of Air-Ground and Mobile services with the ATN as the prime communications

infrastructure. The project focuses on the delivery of ATM services throughout the entire flight

cycle, from the pre-departure stage, using fixed or radio links at the gate, through the taxiing,

takeoff, climb, en-route, descent, approach and landing, culminating with the arrival at the

destination gate.

Within this task, the Trials End System (TES) project has been involved in a number of

activities in support of the development and validation of the ICAO standards and

recommended practices (SARPs) for Air-Ground applications and supporting ATN Upper

Layers. These activities have included requirements analysis, formal modelling of the

applications, and the production of prototype software realisations of the applications specified

in SARPs.

The TES software has been further developed as a component of the Eurocontrol ATN Trials

Infrastructure (ATIF).

3.2.2 Objectives

The objectives of the TES may be summarised as:

• Validation of the ATN Air-Ground applications and Upper Layer SARPs.

This has been fully achieved with the publication by ICAO of the technical provisions for

ATN. The TES contractor independently analysed the draft SARPs, produced functional

and design specifications based on the draft SARPs and implemented the software

realisations. The TES software was then used to test the functionality, interoperability and

performance of the draft SARPs.

• Production of corresponding prototypes and simulation models.

This is achieved by the availability of the TES software and its continuing development,

enhancement and support. Also available are simulations of the ADS application and

ATN Upper Layer protocol, modelled using the formal language SDL.

• Use of TES in ATN experimentation programmes.

Ongoing, with the provision of the TES software to assist member Administrations in their

ATN experimentation, use in internal Eurocontrol experiments and interoperability testing.

3.2.3 TES Architecture

The TES software implements an OSI telecommunication stack based on an environment

from ATOS called C-OSIAM. The architecture of TES is closely related to the C-OSIAM

approach for building a telecommunication stack.

The ATN Upper Layers ensure the end-to-end communication between the two end systems

over a number of ATN routers connected via ATN compatible subnetworks

The two end systems communicate via a standard transport service interface. This point is

important since one objective of the TES software was to validate the SARPs for ATM

applications and ATN upper layers, and not the ATN Internet.

Each of the different TES communication infrastructure configurations is accessible from the

TES platform, a Hewlett-Packard workstation running the HP-UX operating system. The

default configuration, supplied to users, is to use the TAR-TTS to provide a complete ATN

protocol stack.

3.2.4 TES Components

The TES software implements the following air-ground ATN applications as published by

ICAO:

• The air-ground functionality of the Automatic Dependant Surveillance (ADS) application

(excluding the ADS Report Forwarding functionality)

• The air-ground functionality of the Controller Pilot DataLink Communication (CPDLC)

application

• Both the air-ground and ground-ground functionality of the Context Management (CM)

application

• The ATN Upper Layers (efficiency enhancement option Session Layer, efficiency

enhancement option Presentation Layer, Association Control Service Element (ACSE)

edition 2 and Control Function (CF)).

The TES software also implements a flexible Addressing Database (ADB) which provides a

repository for the information exchanged by the CM application, and makes this information

available to other applications and systems management.

Each of the TES software implementations includes both the airborne and the ground based

end system components.

The TES system also includes a COTS test harness which allows test data to be input into the

applications individually or concurrently. The test harness may be used to test both normal

and abnormal events through the TES APIs. This was used to validate the behaviour of the

TES prototype and the draft SARPs.

3.2.4.1 TES Interfaces

The TES software uses the transport layer interface to provide access to ATN Internet.

Different communications infrastructure configurations can be “plugged in” beneath the

transport interface, including:

• TAR-TTS, complete CNS/ATM-1 Package ATN Internet protocol stack;

• commercial off-the-shelf (COTS) lower layers (H-P OTS-9000 product).

Fundamental to the implementation approach is the definition of a set of Application

Programming Interfaces (APIs), enabling a modular approach to be taken. There is no

requirement for such interfaces to be standardised as SARPs, but it could be beneficial to

share the interface definitions with other States and Organisations, to encourage the

development of portable applications and therefore potentially decrease costs by maximising

the market relevance of products developed to work within the global ATN environment.

The TES software provides exposed C-language APIs which correspond closely to the

abstract service interfaces (ASIs) defined in the air-ground application SARPs.

The TES APIs are mostly concerned with giving the user access to data formatting and

sequencing functions. Two levels of API are provided:

• The “raw” API corresponds closely to the ASI defined in the SARPs. It requires the API-

user to initialise complex C data structures, allocating dynamic memory as necessary for

the data buffers. In fact, these structures have been automatically generated by an

ASN.1 compiler, so are not necessarily as user-friendly as possible.

• To provide a more user-friendly interface, each API call has associated with it one or

more formatting or unformatting functions. These functions hide the complexity of the

underlying C data structures from the API-user, and provide instead a “flattened”

parameter list, enabling the user simply to supply the values for the function call

parameters.

3.2.4.2 Limitations

The TES implementation satisfies the functional requirements in the air-ground SARPs - the

“User Requirements” specified in SARPs are explicitly excluded. Thus, any software

accessing the TES software must ensure that the user requirements are observed.

The air-ground SARPs also define interworking possibilities in terms of valid subsets of each

application. The TES software is not configurable in terms of the subsets defined in SARPs;

rather, it conforms to just one of the defined subsets.

The TES software does not include any End-User interface (such as a pilot display or

controller workstation simulation). It does include a licensable COTS test harness to simulate

the functions of such interfaces, and well-defined APIs to allow integration with end-user

applications.

3.2.5 Current Status

The TES software was originally developed in order to validate the draft ICAO SARPs known

as the “Munich output” (June 1996 versions). It has now been upgraded so that it conforms to

the SARPs versions approved in March 1997 (ICAO Version 1.1 - “post-Phuket” SARPs). It is

available for free issue for experimental purposes to Eurocontrol Member Administrations. A

four-day training course has been developed to assist users to exploit the TES software.

Availability: available now as TES release B.

The TES software has been ported onto a PC platform running SUN Solaris 2.5.1 /x86, in

preparation for in-flight trials. It has also been ported onto HP-UX 10 in addition to the original

HP-UX 9 platform.

Availability: Now.

An upgrade of TES to ICAO V2.2 is being performed. At the same time, various usability

enhancements are being implemented.

Availability: June 1998.

3.2.6 Future Developments

Future developments of the TES implementation include:

Simple ATN Messaging. A simple generic messaging service which would be capable of

carrying future (yet to be defined) information structures reliably and securely between

communicating partners, in the context of the Aeronautical Telecommunication Network.

Such a service could be used by future free-standing applications, or alternatively, embedded

into these new applications.

SARPs tracking. As SARPs changes are approved by ICAO, they will continue to be

evaluated for their effect on TES functionality and interoperability.

Remote Access. Currently, the TES user process must be co-hosted with the TES stack.

An enhancement to allow access via standard remote procedure call (RPC) mechanisms is

under investigation.

Other Platforms. The portation of TES software to other software environments and

platforms according to user requirements is under continual review. Other users are

evaluating DEC Alpha platforms.

3.2.7 Relation to Other Projects

As already mentioned in the ATIF description, TES is being used as component of the ATN

Trials Infrastructure, and so has a relationship with a number of ongoing ATN experimentation

activities, including:

• ProATN - this project will benefit from the TES software development and interface

definitions.

• DFS- Germany

• Eurocontrol - FITAMS

• FAA ATN Trials

• SICTA - Italy

• NATS - UK.