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

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

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

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

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

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

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

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

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

COMMUNICATION TYPES and CONNECTIVITY

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

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

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

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

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

ATS CONNECTIVITY

AIRLINE CONNECTIVITY

APC/IFE CONNECTIVITY

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