The overall purpose of the Satellite Data Link System (SDLS) demonstrator was to prove the feasibility of satellite based aeronautical communication system using Code Division Multiple Access (CDMA) access technique in geo-stationary orbits. To prove this feasibility, SDLS demonstrator addressed two different levels, the sub network level, in order to validate technology (modems, protocols), to validate the offered tele-services and to give preliminary evaluation of associated performances, the application level, in order to validate the capability to integrate SDLS in Air Traffic Network (ATN)/Air Traffic Management (ATM) environment and air/ground voice communication capabilities that lead to a new operational procedure. The demonstrator was a first step for a future system implementation.
The objectives associated with the sub network level were:
- To validate the use of CDMA in aeronautical satellite communication system, the SDLS demonstrator implemented CDMA wave form (based on existing wave form) and multiple access techniques;
- To validate the capability to transfer application data flow, the SDLS demonstrator provided customized internal tele-services;
- To validate the concept of service for aircraft position report, the SDLS demonstrator implemented the Automatic Position Report (SDLS APR) service. The SDLS APR service provided dedicated paths and avoided ATN/AMSS overheads in the transfer of position messages between AES and GES;
- To take into account ATN architecture, the SDLS demonstrator validated the capability to integrate SDLS in ATN;
- To cope with ICAO and user needs about transfer delay, the SDLS demonstrator guaranteed (under given conditions) a transfer delay;
- To validate the transfer delay objectives, the SDLS demonstrator evaluated performances at sub-network level.
The objectives associated with the application were:
- To cope with CNS/ATM concept, the SDLS demonstrator integrated a reduce set of ATS and AOC services;
- To validate the integration of SDLS demonstrator in operational aeronautical safety context, SDLS demonstrator implemented voice and mechanisms to guarantee establishment of emergency or distress calls;
- To validate the transfer delay objectives , the SDLS demonstrator evaluated performances at application level.
The SDLS system was a fully operational aeronautical communication system. It provided services that met the aeronautical community requirements in terms of safety (integrity, availability, continuity) and in terms of service performance (number of communications, transit delay, and coverage area). It was oriented to perform operational demonstrations of a CDMA satellite based communication for aeronautical applications. Safety topic was addressed by a priority communication service function. Performance was addressed in a transit delay and connection establishment delay measurement capability. The notion of service coverage did not existed in the SDLS Demonstrator. Theoretically, the SDLS Demonstrator could be used anywhere within the Geostationary satellite payload footprint. Safety system implementation constraints for aeronautical usage were clearly not addressed (certification, etc.). Nevertheless, the software was developed according to DO178B standard (level D or C).