SATELLITE DATA LINK SYSTEM (SDLS)

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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)

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Satellite Data Link System
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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

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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

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ICAO Requirement Summary for theNext 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

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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

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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

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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

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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

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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

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SATELLITE DATA LINK SYSTEMSDLS
It May Well Happen !
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