There are two primary methods to enable a passenger Internet connection on an airplane. first one satellite and another one air-to-ground. I’ll talk about some of the key points on each of those.
two types of the technology behind airplane wifi largely resembles the gear that delivers wireless internet on the ground. Airplanes use many of the same towers and satellites that deliver data to our smartphones, connecting to towers on the ground, or to satellites, or to both
Air-to-ground methods signals go from the airplane directly to antennas on the ground. Air-to-ground (ATG) connectivity is ostensibly faster. ATG uses a network of ground cell towers and uses a version of CDMA, just like Verizon cell phones. Antennas are on the belly of the airplane, looks like a small fin.image via Gizmodo.
As the airplane flies, the connection hands off from one tower to the next just like your phone does when you’re driving. Users don’t notice any interruption. Bandwidth for the newest generation system (ATG4) is up to 9.8 megabits per second (Mbps) per airplane (shared across all users). This is enough for email and casual web surfing.
Image via United
Unlike air-to-ground, signals from the airplane go into space to an orbiting satellite and then down to the ground. These satellites are usually in geostationary orbit, 22,300 miles up. Three types offer different levels of performance (bands indicate specific transmission frequency ranges):
- L-band (e.g. Inmarsat Swift Broadband): pretty slow, max 422kbps per channel per airplane
- Ku-band (e.g. Panasonic, Global Eagle, and Gogo): tops out at around 20-40Mbps per airplane. Speeds depend on how many airplanes are in the satellite’s transponder “footprint” (aka spot beam)
- Ka-band (near future, satellites launching soon): promises even higher speeds
Image via Gogo
A modern satellite has dozens of transponders to support a large number of simultaneous connections, e.g. ships, airplanes, portable ground terminals. Leasing transponders (antennas) on satellites is very expensive, so this cost is usually passed on to the airline and the passengers. But Jetblue offers it for free.Using satellites means a few hundred milliseconds more latency since the data packets need to go 22,300 miles up to the satellite, then roughly 22,300 miles back down to the airplane. New constellations of low earth orbit (LEO) satellites providing lower latency high bandwidth connections are in development since 2015, e.g. by SpaceX.