1. SATELLITE DATA LINK SYSTEM (SDLS)
A DEDICATED MOBILE SATELLITE COMMUNICATION SYSTEM RESPONDING TO THE HIGHLY DEMANDING REQUIREMENTS OF CIVIL AVIATION
Claude Loisy
European Space Agency (ESA)
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

2. Satellite Data Link System
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

3. The Air/Ground Communications of Civil Aviation
Two Categories of Communications
Safety related : ATS (Air Traffic Services)
AOC (Airline Operational Communications)
Non Safety related :  AAC  and  APC (passenger communication)
Technical Requirements for Safety Related
Specified by ICAO (SARPs)
Mandated by States to Air Transport
Communication Systems Deployed at Present
Terrestrial “VHF” : generally available in continental airspace
Terrestrial “HF” : low capacity, slow response but worldwide coverage
Satellite “AMSS” : costly and deployed on only 2000 aircraft
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

4. Meeting the Future Capacity Requirements of Safety Communications
Required Capacity is Steadily Increasing
Air Traffic volume displays an almost constantly expanding trend
Anticipated reduction in aircraft geometrical separations will induce an increase in tactical exchanges and the per aircraft communication traffic
The VHF Aero Band is Nearing Saturation
Frequency Re-use is severely limited by network geometry
Recent Introduction of higher efficiency modulation techniques for voice (8.33 KHz instead of 25 KHz channels) is buying some extra time
Introduction of data services will initially increase spectrum demand
Introduction of a new system is being studied
Satellite is among the options under consideration
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

5. ICAO Requirement Summary for the Next Generation Satellite System
Geographical Coverage
Worldwide coverage is needed
Two types of scenario:
LEO or MEO constellation
Interoperable GEO based networks
Continuity of Service Provision
Users expect high continuity based on a stable technical standard
Avionics lifetime should by far exceed that of aircraft (no retrofits)
Services and Associated Performances
Voice and/or Data
Fast response and high availability
Affordable Costs
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

6. SDLS Main System Options
Safety Communication Dedicated System
Allows stable and less challenged access to radio frequency spectrum
Avoids the inherent risks of sharing resources with a business venture
Highly simplifies the design and reduces costs
Open Technical Standard
Geosynchronous Orbit (HEIO for the N polar cap)
Capability for Highly Distributed Satellite Access
Aircraft Earth Station Characteristics
Low cost isotropic antenna
Low cost single channel and medium transmit power level
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

7. SDLS Main Design Characteristics (1)
Services
Voice service (point to point and “Party Line”) 
Data service including broadcast and polled on-board parameter retrieval
Network Architecture
Capability for decentralised satellite access
Satellite Diversity
Dictated by service availability requirements
Equipment Redundancy
For both airborne and ground is part of the design
Communication Resource Management
Fixed and demand assignment, handling of priority levels
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

8. SDLS Main Design Characteristics (2)
Multiple Access Scheme
Synchronous CDMA in the fixed to mobile direction
Quasi Synchronous CDMA in the mobile to fixed direction
Fixed Earth Stations
Ku or C-Band depending on satellite feeder links
Only Ku-Band VSATs practically allow highly decentralised access
Aircraft Earth Stations
Low cost solutions meeting avionics standards are readily available
Only the CDMA modems require a specific development
Space Segment
MSS GEO satellites at L-Band have already been deployed worldwide
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

9. ICAO/AMCP WG C 2nd meeting
The SDLS Demonstrator
Objectives
Provide evidence to the prospective Aviation users that a satellite based Air / Ground communication system can meet their most stringent requirements provided the correct design options are selected
SDLS Programme Phases
Key system performance demonstrator with AESs on ground (on-going with targeted completion third quarter 2002)
A full scale validation with airborne avionics and the participation of CAAs and airlines is in the planning stage
Industrialisation could immediately follow a decision by aviation to take advantage of SDLS to build an ICAO standard
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

10. ICAO/AMCP WG C 2nd meeting
Conclusion So Far
Satellite appears to be very well suited for the Safety Communications of Aviation
Extended geographical coverage capability
High service quality levels are achievable with proven technology
Affordable costs
Difficulties Inherent to the Aviation Environment
Decisions tend to be taken only when forced by external constraints
Trial and error often takes precedence over theoretical analysis
Long term planning appears to be almost incompatible with the fundamentally political nature of international decision making processes
However
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

11. SATELLITE DATA LINK SYSTEM SDLS
It May Well Happen !
ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001

12. ICAO/AMCP WG C 2nd meeting
7 to 11 May 2001