1. Broadband Satcom for Aeronautical Communications
Graham Huggins
EADS Astrium Limited
and
Paul Ravenhill
Helios Technology Limited
ATN 2003
24 September 2003
IEE, London

2. CONTENTS
Motivation, objectives, constraints
Communications requirements
Technical Issues
Technical Options
Conclusions

3. ACKNOWLEDGEMENTS
This work was supported by the British National Space Centre through a study contract under its 3 programme.
Thanks are due to:
Hemat Gohil and Ian Munro of BNSC
Stuart Forsyth of Helios
Alan Schuster-Bruce of Thales Avionics

4. MOTIVATION
ATM limitations currently contribute to delays
In the future it is widely accepted that without changes, ATM limitations will inhibit the anticipated expansion of the civil aviation industry with impacts on the global economy
Many experts believe that data links form the cornerstone of the future ATM improvements
In particular VHF saturation is a problem in areas of high air traffic density and there is satellite spectrum available
There may be demand for broadband communications for passengers – satellite is the obvious way for long haul flights
Security concerns have increased in recent years – could lead to increased interest in continuous coverage

5. OBJECTIVES
Establish how satellite communications might form an essential component of future aviation communications infrastructure
To base future satellite communications for aviation on global open standards and not use proprietary systems
Determine the road map to achieve the vision
Determine the key space technology necessary
“Broadband” is defined loosely – we have not introduced a minimum data rate

6. WHAT HAS HELD UP THE TAKE UP OF SATCOM IN AVIATION ?
Cost of usage
Cost of installation
Cost of maintenance
Passengers use airline’s phone

7. CONSTRAINTS AND DRIVERS
Overall communications system will consist of terrestrial and satellite communications components
Ideally want the choice of physical layer to be transparent to the end user
Initial computations suggest that aviation requirements are insufficient to “fill” a modern satellite – we need to keep in mind the prospect of using some satellite resources for other types of communications.
Need to bear in mind issues such as safety, mounting of antennas, cost, availability etc.
Need to be spectrally efficient
The time frame is more or less that of Inmarsat 5
Inmarsat will soon be offering Swift 64
We will consider any type of communications to / from an aircraft
Emphasis is on civil aviation

8. CURRENT ACTIVITIES AND INITIATIVES
EC – Single European Sky legislation
EC – Road map study for Data Links – Helios Technology
EC – Analysis of options for overall improvements to ATM for aviation
Eurocontrol – NexSat
Boeing Connexions (passenger communications)
FAA GCNSS

9. COMMUNICATIONS REQUIREMENTS
Cockpit
ATS (Voice, data, surveillance, security)
Cabin
Airline
Administrative (AAC)
Operational (AOC)
Passengers
Telephony
Internet
In flight entertainment
Analysis of data rate and capacity requirements was carried out

10. COMMUNICATION TYPES and CONNECTIVITY

11. Medium Earth Orbit (MEO)
Geostationary (GEO)
Regional
Phased deployment possible
No satellite handovers
Appreciable propagation delays
No coverage of polar regions
Medium Earth Orbit (MEO)
Intermediate between GEO and MEO
Low Earth Orbit (LEO)
Negligible propagation delays
Needs a lot of satellites
Numerous handovers
Iridium was seriously considered
Future availability seems in doubt

12. ORBIT PREFERENCE
GEO is seen as the most appropriate orbit class – at least for a 1st generation
The regional nature of GEO fits better with political concerns over ownership and deployment dates
More options for selling spare communications capacity
Delays not usually problematic with data
Lower cost
Established technology
Lack of polar coverage not considered to be critical

13. FREQUENCY OF LINK L-band Ka band Ku band C band
Ideal for mobile users – no significant rain fade
Scarce – likely to be always relatively expensive
Already used by Inmarsat
Long wavelength so large antennas needed
Technology well established
Ka band
Plenty of spectrum available
Technology not so advanced
Ku band
Used for TV – some aviation usage
Technology established, spectrum fairly scarce
C band
Scarce

14. COMMUNICATIONS SERVICES
We wish the communications system to handle voice, packet data and surveillance
Voice expected to decline in importance but considered essential for emergency situations
We absolutely wish to avoid an open circuit for long periods of time – capacity on demand
Some communications services may be of broadcast mode eg weather reports, surveillance reports of nearby aircraft etc.
We want to charge per bit of useful data not for time circuit was open
Need a Bandwidth on Demand system with good guarantee of quality of service
Rapid channel set up times
Asynchronous Transfer Mode fits these requirements

15. SATELLITE PAYLOADS
High capacity & small antennas on aircraft drive satellite to use numerous spot beams over coverage area (up & down links)
Switching between feeder link channels and mobile link spot beam channels in a spectrally efficient manner is very difficult to perform with analogue technology
Need digitally processed payloads
Digital payloads can be either transparent or regenerative
Inmarsat 4 will use transparent digital payload processor
Regenerative is well suited for ATM by having an onboard switch that switches actual ATM cells
Such satellite systems have potential for huge data carrying capacity (10Gbps or more) – greater than aviation’s need

16. ATS CONNECTIVITY

17. AIRLINE CONNECTIVITY

18. APC/IFE CONNECTIVITY

19. CONCLUSIONS
Economic studies indicate that an “aviation only” or “ATS only” satellite communications system is expensive and that there would be “spare” capacity for selling to other users
Open standards for communications interfaces are strongly preferred
Cockpit and Cabin communications can realistically be delivered by the same satellite system
The communications system for aviation in the future will consist of both satellite and terrestrial – this is not a question of satellite fighting against terrestrial
We studied L-band and Ka band
A bandwidth on demand system is best suited to delivering quality voice, data and broadcast services
Regenerative payloads on satellites able to switch ATM cells preferred eventually