There are several ways in which we can navigate aboard an airplane. None of them are transcendental, they are practical solutions to a tangible problem that airlines resort to and then offer them to their customers at very different rates. To understand better we turned to Claudio Casetti, Professor of Telecommunications Networks at the Politecnico di Torino: “The principle is not unlike what we are used to with the Wi-Fi connection at home or in the office. In the rooms of the house the Wi-Fi signal is spread by one or more devices called ‘Access Points’ (technical term of the Wi-Fi Router) and reaches the various laptops, smartphones, tablets, smart TVs and other sensors that we may have installed in home; connectivity to and from the outside (the backhaul in technical terms) is managed by an operator through a fiber optic connection, copper or through the cellular network. On a plane, one or more access points broadcast the signal in the cabin, and the backhaul is achieved through a satellite connection (air-satellite-ground station) or with a direct connection to the ground using an ‘aeronautical’ version of traditional cellular connections. There are different standards and operators depending on the region: in Europe there is the European Aviation Network operated by Inmarsat and Deutsche Telekom and based on 4G, but with a roadmap of evolution to 5G in the coming years. The use of satellite or terrestrial backhaul depends on the location of the aircraft, with satellite link being the only solution available over the ocean or in sparsely populated areas. The satellite has a greater delay than the terrestrial link, due to the round trip time of the signal towards the satellite (which orbits about 35,000 km away), but a band (and therefore a data speed) higher than the terrestrial one ”.
Air-To-Ground
In Europe, the British mobile satellite telecommunications company Inmarsat implemented Air-to-Ground (AtG) technology in Europe as early as 2014, providing connectivity to passengers on continental flights. From that moment on, even in Europe, internet connections on board airplanes have spread, even if not all airlines offer a Wi-Fi service, others make it available only on long-haul flights or, again, on certain aircraft models only.
The AtG connection travels from the ground to the aircraft and, from there, to the ground. A mode that only works when flying over land. AtG technology is constantly evolving and different providers offer more powerful solutions that are gaining a market for themselves. Gogo, one of the world‘s leading providers of internet and entertainment services for aircraft, is a large laboratory where new solutions, including hybrid ones, are tested to increase both browsing speed and connection stability.
AtG communication takes place via radio waves emitted by cellular antennas located on the ground to which the aircraft connects while in flight by hooking up from time to time to the closest one. The aircraft is equipped with antennas located on the underside of the fuselage. The bandwidth guaranteed by this technology varies from 3.1 Mbps to 9.8 Mbps – not enough for smooth navigation – this partly explains why airlines, when making offers for in-flight Internet use, prepare packages that they only allow the sending and receiving of text (and text only) through any instant messaging application.
The connection also tends to be weaker, where the antennas on the ground are more diluted (the morphology of the territories does not always allow them to be equally distributed), and to be a dancer when the plane releases from one tower to dock with another. .
Satellite
The limits of AtG technology can be overcome thanks to satellites that communicate with the aircraft via the Ku band – from 12 GHz to 18 GHz frequency – and that reflect the signals coming from the towers on the ground back to the aircraft. To take advantage of this possibility, antennas are mounted on the top of the aircraft fuselage.
The contribution of the Ku band allows passengers to navigate at higher speeds (30-40 Mbps) but, even in this case, it is not a guarantee: first of all, the total band refers to the aircraft and not to the individual user, this means that the more people are connected to the network, the more the bandwidth will become saturated and, moreover, a satellite can communicate with several airplanes at the same time and this also affects the available bandwidth. At the expense of the use of satellite technologies there is also latency, that is the time it takes for the data to travel between the point of origin and the destination, much higher than the latency times of AtG technology.
To fully enjoy the potential of navigation, including for example the possibility of using streaming content, it is necessary to use the Ka band, also satellite (between 27 and 40 GHz) and which allows you to navigate at higher speeds even at 100 Mbps. It goes without saying that when flying over oceans or over territories with poor ground repeaters, it is necessary to leverage satellite technology.
There is also the energy issue, as Professor Casetti explains: “An important aspect is energy consumption: the ‘terrestrial’ backhaul uses small antennas placed on the belly of the aircraft, while the ‘satellite’ backhaul uses an antenna. larger, similar to our parables on the roofs, protected by a dome and placed on top of the plane. The size and position of the dome produce adverse aerodynamic effects that lead to greater fuel consumption, making the satellite solution less ‘green’ “.
Costs
ITA Airways (the prices indicated here are inherited from those applied by Alitalia) offers various packages, from 10 Mb to 200 Mb of traffic, whose prices range from 1.9 euros to 19 euros.
KLM offers 30 minutes of free navigation on continental flights, which can only be used to send and receive text messages (therefore without multimedia elements). Other solutions vary from 8 to 18 euros for the entire duration of the flight. The same logic also applies to intercontinental flights
Lufthansa offers three different packages. The first costs 7 euros and allows you to surf at 64 Kb per second. Enough speed to use instant messaging apps. Alternatively, for 17 euros, you can buy 500 Mb of data traffic at 400 Kb / s, a package that the airline recommends to those who want to “surf the Internet moderately”. The same browsing speed, but with a data volume of 1 Gb, costs 29 euros.
Swissan airline that is part of the Lufthansa group, is more expensive: 20 Mb of traffic can be purchased for 9 Swiss francs (8.6 euros) and up to 220 Mb of traffic for 59 francs (56.5 euros).
In short, tariffs that are not purely proletarian: “There are certainly several factors at play. This is indeed an expensive service, especially if you want broadband on board. In this case, the satellite connection is currently the only one able to guarantee bands higher than 100Mb / s (aggregate value for the whole aircraft: the band available to the single passenger user is much lower and depends on how many are using the service. in that moment). The satellite is the bottleneck: the number of satellites is limited and each has a maximum capacity with which to serve users. The price is set by the operator rather than by the carrier, which offers Wi-Fi on board as an additional service and has no commercial interest in discouraging its use. Finally, there are factors of economy of scale: at the moment the service is not offered by all companies, and those who offer it have not yet extended it to the entire fleet: it is conceivable that with the increase in supply, prices will drop. ”Explains Professor Casetti.
Offer that new technologies, in this case linked to 5G, will contribute to increase. “5G guarantees more bandwidth, greater coverage and stability, thanks to the ability of 5G antennas to ‘track’ each individual aircraft from the ground and therefore offer a ‘dedicated’ backhaul to each aircraft that uses the technology“, concludes Professor Casetti.