How Wi-Fi on airplanes works and why it is expensive yet slow

Fliers in India will soon be able to access internet while flying through WiFi hotspots. Telecom Commission, the highest decision making body in the sector, has given a go ahead to in-flight Wi-Fi services. This means both domestic and international airline companies operating in India will be able to add WiFi access to their bevy of services to lure new passengers.

However, Wi-Fi service on flights is going to be a different ball game from the existing public Wi-Fi networks which are available at hotels, railway stations and cafes.

At an altitude of 35,000 feet, signals from land based mobile towers are too weak to allow users to make calls let alone access internet.

Which is why In-flight internet services are made available through geostationary satellites, widely used for TV signals and weather forecast. These satellites allow internet services on airlines in two ways—ATG (air to ground) and Satellite Internet. In the first case, the satellite first send signals to receivers on the ground, which then transmit them to antennas on the airline. However, this works only when the airline is flying over land. In the second case the Satellite beams signals directly to antennas on the airline. It allows users to connect anywhere, even when the flight is over water.

Wi-Fi on flights was first introduced in US by Gogo Inc. on Virgin Atlantic airlines in 2008. It offered speed of up to 3Mbps using Satellite Internet. This direct transmission of internet through satellites was initially carried out on Ku band. This is a portion of electromagnetic spectrum in the range of 12 to 18GHz. Ku is derived from German term Kurz Unter, which means short under. In a nutshell Ku band refers to frequency bands under the K band.

Most airline based service providers in US have transitioned from Ku band to the Ka band, derived from German term Kurz Above. This is frequency band or the portion of electromagnetic spectrum above the K band. It has a range of 26 to 40GHz, which means it will deliver better bandwidth and faster data speeds. Honeywell Aerospace, another in-airline service provider is giving data speed of up to 9Mbps on flights in US using Ka band.

Airlines will also have to install a server, router along with the equipment to re-orient the antenna to face the satellite and convert the satellite signals into data packets.

When an airline moves from the range of one satellite to another, it will lose signal for while. It is called the hand-off period and it is similar to the period when there is no network when a user on ground moves from the range of one tower to another.

Though the technology used has evolved, the speed of internet on flights is still slower than the internet speeds available on land based public WiFi networks which can muster speeds of up to 25 Mbps easily. This means users are still years away from getting the speeds which would allows them to stream movies from Netflix. All they can do is check a few emails and browse through news articles.

Also, users have to pay extra to access the WiFi network. Etihad airlines in US charges $4.95 for 30MB of data while British Airline charges $14 for an hour of unlimited data access, which is quite expensive in the age of 4G and free data.livemint