AMCP/WG-C/WP 21

AERONAUTICAL MOBILE COMMUNICATIONS PANEL

Working Group C Meeting No. 1

Montreal, Canada

11-19 October 2000

Agenda Item 7: Future systems: Satcom
Presented By: Claude LOISY, European Space Agency
Information Paper

EUROPEAN SPACE AGENCY SPONSORED DEVELOPMENT

OF A SERVICE DEMONSTRATOR FOR

A FUTURE SATCOM SYSTEM DEDICATED TO CIVIL AVIATION

AIR / GROUND SAFETY COMMUNICATIONS

SUMMARY

This document updates a summary status report presented to the 12th meeting of AMCP WG-A on research and development activities, either already completed or recently undertaken, within the framework of the European Space Agency (ESA) Telecommunication Programmes. The objective of this work is to demonstrate the capabilities of dedicated satellite communication network architectures and designs using satellites in the geostationary orbit, in meeting the specific requirements of highly demanding and specialised applications such as the Civil Aviation safety air/ground communications.

A service demonstrator for the proposed “Satellite Data link System” (“SDLS”) is being designed and produced under a contract of some 3.5 million Ecus recently placed by the European Space Agency with a European industry consortium led by Alcatel Space Industries (ASPI) of Toulouse France.

The intention is to make this demonstrator available to a user’s led entity for performance evaluation in test environment representative of the targeted operational context.

  1. Introduction

As had been reported to AMCP WG-A 12th meeting (WP 514a attached as Annex 1), the European Space Agency(ESA) has been sponsoring study and development work since 1994 with the objective of demonstrating the potential of Satcom for implementing the A/G safety communications of civil aviation beyond the scope of the “AMSS” system presently in use. Indeed, “AMSS” has been targeting the coverage of oceanic type of airspace, where alternative communication means are scarce or simply missing.

As a consequence of the early work performed, it is thought that a modern specifically designed aeronautical satcom system could provide voice and data communication performances equivalent to those of terrestrially based radio systems and hence well in line with what is required for the mostly demanding high density continental airspace. Besides, the present state of satcom technology would allow to equip all aircraft, within installation constraints and costs equivalent to those of the terrestrial VHF systems.

  1. System Demonstrator under Development

The European Space Agency awarded in Spring 2000 a contract to a European industry consortium led by Alcatel Space Industries (ASPI) of France to study design and implement a SDLS service demonstrator.

SDLS (standing for Satellite Data link System) is a system and network concept defined by the European Space Agency with the specific target of meeting the future requirements of the safety A/G communications of Civil Aviation. This concept was analysed and evaluated through study contracts awarded to industry by ESA. It is now validated and embraces also voice communication along with the data exchanges. It is also important to note than rather than using a dedicated satellite constellation in LEO or MEO orbit, the worldwide deployment of SDLS would take place using geostationary space segment at L-Band already in place, at least in an initial phase. Dedicated payloads on-board host geo satellites deployed for other missions could subsequently be implemented with the view of improving the quality of service.

It is ESA’s intention to accurately follow the development of emerging specifications produced by Civil Aviation recognised entities for the performances of a future A/G voice communication as the definition of SDLS evolves, in order to give the new system a maximum chance to be optimised with respect to the users wishes. Concerning existing ICAO SARPS for Satcom, it is the intention that SDLS will fully satisfy the requirements of Chapter 12 of Annex 10.

For what concerns the service demonstrator to be produced under the ASPI contract, it is based on a system concept access techniques and protocols originally developed by ESA to satisfy the market of private networks to be used by terrestrial transport industry, with a focus on fleet management for land mobiles. This concept was implemented a few years ago using capacity from the Inmarsat network and was validated. The implementation of the SDLS demonstrator by ASPI will heavily rely on this already technically validated work. One of the most attractive service element provided by the demonstrator for evaluation by Civil aviation will however be a specific new development, since it does not correspond to any particular requirement of road transport fleet management. This is the so called “party line” which is heavily used by civil aviation to handle voice communication for the exchange of tactical messages between aircraft pilot and air traffic controllers on the ground. The SDLS demonstrator will emulate the party line service in a significantly improved environment with regard to the comfort reliability and robustness of handling the random access (Push To Talk) function which is the key feature and troublesome characteristic of party line in the busy sectors of the airspace.

The SDLS demonstrator will confine itself initially to demonstrate attainable performances of the A/G communication system using AESs installed on the ground. This limitation, dictated by the available budget at this point in time, does really impact on the validity of the service demonstration, since the propagation characteristics of radio waves between aircraft and geo satellites have been heavily studied and experimented with. Hence their contribution to system performance can be reliably predicted.

It is ESA’s intention, after validation of the technical performances of the SDLS demonstrator by the industrial consortium to offer usage of the demonstrator to civil aviation entities for operational evaluation. Requests for evaluating the SDLS demonstrator will be handled by ESA in accordance with the requirements of its Member States. Preference is therefore likely to be given to requests emanating from Europe. Preliminary studies for the integration into pre-operational evaluation test beds are about to be started.

  1. Further Phases of SDLS
Beyond the on ground demonstrator phase and assuming that performance expectations are generally satisfied, it is the intention to proceed with an in-flight demonstration, having equipped a limited number of aircraft with the suitable avionics. The intention is to involve candidate airlines in the demonstration with the scope of accessing to a large number of flight opportunities and reach an as large as possible audience for the demonstration.

Assuming aviation’s interest would get further confirmed, which in view of the predicted congestion of the VHF frequency band over the high traffic density areas appears to be a highly probable prospect, if the demonstrated system performances are good, the development of a fully fledged system satisfying all identified operational requirements could be initiated.

It is important to note at this stage that the system studies have not identified areas of concern in terms of availability of the required technologies, they are all readily available today.

ANNEX 1

AMCP WG-A 12th meetingAMCP/WG-A/WP/514a

EUROPEAN SPACE AGENCY SPONSORED STUDY WORK

TOWARDS

A FUTURE GEOSTATIONARY BASED SATCOM SYSTEM DEDICATED TO CIVIL AVIATION AIR / GROUND SAFETY COMMUNICATIONS

Presented by C. Loisy European Space Agency

SUMMARY

This document presents a summary status report of research and development activities, either already completed or recently undertaken, within the framework of ESA’s Telecommunication Programmes with the view of demonstrating the capabilities of dedicated satellite communication network architectures and designs using the geostationary orbit, in meeting the specific requirements of highly demanding and specialised applications such as the Civil Aviation safety air/ground communications. ESA has taken the commitment, at the Brussels meeting of AMCP-WGA, to keep the Working Group regularly informed of the achievements of the relevant study work financed by ESA member States.

Against the background of earlier development work targeted at studying the applicability of mobile satellite systems, using simple lightweight and rather inexpensive mobile user terminals, to the operational communication requirements of fleets of vehicles, and based on the results achieved with experimental implementations using geostationary satellites (initially MARECS, then INMARSAT II and III and now the European pre-operational L-Band payload with European regional coverage EMS), the European Space Agency (ESA) undertook in 1994 to study the applicability of using the experience and results collected in their experimental work referred to as Mobile Satellite Business Networks (MSBN) when planning a second generation Satcom system for the safety air/ground communications of Civil Aviation.

In contrast with the initial target of the present AMSS which has been focusing on oceanic airspace environment, the ESA study deliberately addressed the service requirements corresponding to all types of airspace, including high traffic density continental airspace; the view was also to make the service accessible, in terms of avionics requirements and operation costs, to all commercial aircraft, including possibly General Aviation. Since the results obtained within ESA appeared promising, a feasibility study contract was awarded to industry in 1995. The study work performed under an ESA contract [Ref.1] awarded to a consortium led by ALCATEL ESPACE of France, and to which SOFREAVIA (a subsidiary of the French CAA) contributed, achieved a comprehensive specification of communication performance requirements for the service. The work went on analysing various network architectures and designs although mainly focusing on using geostationary satellites. An economic analysis followed which provisionally concluded, pending further detailed studies, that in the particular framework of the airspace under control by the ECAC (European Civil Aviation Conference) countries, the proposed SDLS (Satellite Data Link System) could address a significant market, since, from a performance vs. cost point of view, it would be a highly credible competitor to Mode-S over continents, not to mention the same capabilities being offered in addition, beyond radar coverage.

The ALCATEL feasibility study having identified considerable constraints to achieve some performances and specifically the transfer delay for ADS reports, as a consequence of both the way the ATN ADS application is specified and also other ATN requirements (in particular some significant protocol overheads which may strongly affect the Mobile Sub-network performance as well as its economics), an alternative approach had been investigated, as part of the study considerations: the introduction of “Specific Services” as a possible complement or replacement for those applications, which would be most suffering in terms of performance from a strict compliance to ATN, in particular ADS.

In order to pursue the idea, a further contract under the name “Synchronous Satellite Link for ATM” was placed by ESA in 1996 with NATIONAL AVIONICS LTD of Ireland, assisted in their work by the Irish Aviation Authority (IAA), with the view of refining this latter approach. The study was successfully completed and the Executive Summary of the contract Final Report is available [Ref.3]. In the mean time the final field test results of the CDMA based MSBN experimental system were obtained, which successfully demonstrated the feasibility of a two way full duplex data link, with a 4.8 Kb/s error free user data rate or high quality vocoded voice, using a 14 dBw EIRP AES (20W HPA with a short connection to a quadrifilar helix isotropically radiating antenna) and the Global Beam of the Indian Ocean INMARSAT III satellite.

Finally, based on the results mentioned above, ESA has reached the conclusions that a second generation Satcom system:

  1. using primarily the Regional Spot-beams, and also Global Beams where Spot-beams are not available, as currently provided by geotationary satellites in the MSS or dedicated payloads on-board FSS or BSS satellites,
  2. using low cost AESs with 20W HPA capability and an isotropic antenna,
  3. providing a decentralised network architecture capability (GESs co-located with the ATCCs) since low cost VSAT type GESs can be used in so far as the feeder links to the satellite are implemented at Ku-Band,
  4. meeting the availability requirements of “Primary Means” systems through provision of full redundancies by means of:
  • satellite diversity (two satellites always simultaneously in view of the aircraft and the GES,
  • fully active redundancy at the GES (in particular two VSATs: one for each satellite)
  • full standby redundancy in the aircraft,
  1. dedicated to the provision of aeronautical safety communications (ATS and AOC)
  2. using sub-bands in the 1.5 / 1.6 GHz MSS bands allocated world-wide,
  3. meeting the requirements of ATS including the highly demanding ones of some applications (specifically ADS) in all categories of airspace through a combined provision of ATN and non ATN “Specific Services”,

could be implemented world-wide in compliance with the set of recommendations to States regarding the implementation of the Aeronautical Mobile Satellite Service as they are to be found in Annex 10 of the ICAO Convention. In particular, the open competition in procuring the various system elements (Space segment, Ground segment and User segment) could be maintained.

As a consequence, taking into consideration the interest shown by several European CAAs and Eurocontrol as well as by European industry, the European Space Agency has engaged a further action in 1997 in issuing a competitive Invitation To Tender, the Work Statement of which [Ref.3] calls for the detailed study and implementation of an in-flight demonstrator system of SDLS in order to prove the expected merits of a communication system based upon the following approach:

  • use technology already developed for the modems (whether CDMA or FDMA) ,
  • incorporate an extra TDMA layer (when compared to the present AMSS) in order to allow an efficient spectrum sharing by GESs and therefore have the capability to economically accommodate a larger number of them,
  • provide an ATN compatible interface for integration and application testing within existing operational test beds,
  • provide also under “Specific Services” an “ADS” application which exhibits guaranteed performances (in particular for the transit delay) irrespective of network loading,
  • provide for performance testing under fully loaded conditions.
  • . use the EMS geostationary payload at L-band with its feeder links at Ku-Band for service evaluation

The rationale for proposing SDLS as a second generation Satcom is explained in detail in [Ref.4].

Following the evaluation of the submitted offers, a contract was placed in November 1997 for a ceiling amount of 4 MECUs with an industrial group led by ALENIA AEROSPAZIO of Rome and including the participation of ENAV (the Italian CAA). Work was started for the study phase following financial authorisations by Member States for an initial amount of 1.2 MECUs and is on-going.

References

[Ref.1]: Aeronautical Satellite Data Link System Study,ESA contract 11225/94 /NL/US.

[Ref.2]: Final Report (Executive Summary),ESA contract 11967/96/NL/US Synchronous Satellite Data Link for Air Traffic Management.

[Ref.3]: Statement of Work Aeronautical Satellite Data Link System for Air Traffic Management (SDLS), TSM/60058/CL/asp,Issue1.

[Ref.4]: Future Satcom System Tailored for ADS in High Density Airspace, Claude Loisy, European Space Agency, The Netherlands. Proceedings of Automatic Dependent Surveillance Conference, 24th March 1997, The Royal Aeronautical Society, London, United Kingdom

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