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Aviation

Keeping WiFi sky-high

Ever wondered how you receive your WiFi signal onboard?

Regular SAS travelers have probably by now already had the chance to test the high-speed WiFi service offered on most short haul flights. The service is being rolled out on a continuous basis with the aim of it being  available on the majority of short haul flights by early 2020.

The process of actually making the signal available for travelers to surf and stream online as if they were at home, is, inevitably a complex one. The Viasat satellite-based service enables passengers to connect by using the highest capacity Ka-band geostationary satellites, which send and receive internet data to and from the aircraft.

Each WiFi-equipped aircraft has a fuselage-mounted antenna, covered by a protective shell, known as a radome, along with a modem, server and several wireless access points, which work together to provide each passenger with a strong Wi-Fi signal onboard.
From there, for the traveler, it functions just like the WiFi systems we are used to at home, with access granted via a login.

But where does it come from? In a two-way process, data is transmitted to and from the plane through a satellite, some 36,000 kilometers above the Earth. The data is sent from the plane to the satellite, then down to a ground station, back up to the satellite and then finally to the plane – all in the space of less than one second.

SAS passengers receive high-speed connectivity on nearly all European routes, however, on some routes passengers may experience a temporary dropout as a result of the satellite coverage map. In practice this mainly tends to occur when you are flying over the North Sea or the Bay of Biscay.

Another reason for a possible loss of connectivity at times is “tail-blockage.” Satellites require a direct line of sight with an aircraft’s antenna to transmit data to passengers. Because geostationary satellites maintain a fixed position relative to the earth along the equator, if an aircraft’s tail is positioned between the satellite and the aircraft’s antenna a loss of service can occur. This can theoretically occur whenever a plane flies directly away from the servicing satellite, although in reality it very rarely happens and if it does, connectivity is only briefly lost.

And the good news is that the high-speed WiFi service is going to get even better. In 2021, Viasat expects to launch a new satellite that will increase the coverage area over the region, including areas that are currently not covered by the KA-SAT footprint.

How it works

Before you receive your data onboard, it has already traveled via the ground and a satellite over 30,000 km above the Earth. 

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