Terrestrial antennas DVB-S RCS

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8.1.1.3 AOC datalink “en route”

These AOC communications are quite new, developed to provide internet access onboard and are mostly based on 3 media: Terrestrial antennas, revamping a mobile phone techno, enhanced to support plane speed and distance 10km altitude Geostationary satellite GEO and classical DVBS2 + RCS Low orbit satellite constellations soon MEO too

8.1.1.3.1 Terrestrial antennas

Actually only one such solution exists, and is called the gogo-biz previously AirCell. Several communication towers are installed on the US territory under major fly routes and provide kind of ADSL like internet aboard. A special airground antenna has to be installed under the plane to be able to receive and emit data. Of course this service cannot be transposed for global ATC datalink, since it is just present on ground on profitable airways to oceanic coverage, isolatedremote places… In addition as this service operates in L-band, which is a very expansive band, and very regulated in every country, a global use is very improbable.

8.1.1.3.2 DVB-S RCS

Since the boeing initiative of ‘connection by boeing’ in early 2000, it was possible to get an internet access in a plane, like a particular living in a remote place far from PSTN DSL. This costs a special antenna on the top of the plane, very heavy, to replace the common parabolic dish used for TV reception internet by satellite. Several dynamic antennas exist, using different technologies. As the plane is moving, the antenna has to figure out how to point to the right satellite. This innovation is made possible trough the separate usage of multiples antennas dipoles and a lot of software to be able to delay amplify differently the reception of each element to provide the direction. Same alchemy for emission, as an antenna even a network antenna is always symmetric for emission or reception. Right now all commercial offers row 44, matsushita, … use Ku Band, but some antenna already exist to use Ka Band like the one from DLR’s Santana project allowing even higher bandwidth multiple gigabits per seconds. Those antennas are still not used for ATC, because they are heavy and cannot equip any plane only big ones with enough room on the roof, and their difficulty to operate on polar routes where the angle required to point GEO is too highfor the antenna . As most of flights between Asia and US use such airways, this is a problem. Copyright © 2011 Open Geospatial Consortium 109

8.1.1.3.3 Satellite constellations on GEO