HomeTrendyThe Magical Science of Wi-Fi on Airplanes
December 2, 2019
The Magical Science of Wi-Fi on Airplanes
The Magical Science of Wi-Fi on Airplanes
SSurfing the internet at 35,000 feet is now something that we expect on flights. According to the 2018 Global Traveler study, 94% of global travelers feel that inflight internet would enhance their travel experience and 30% of them explicitly look for this feature when booking their flight.
Currently, airlines make $17 per passenger for services like inflight food and retail. Inflight Wi-Fi will add $4 to this ancillary revenue and is estimated to bring in $30 billion in additional revenue for airlines by 2035.
Given these stats, it’s not surprising to see airlines around the world rushing to add inflight Wi-Fi to their list of amenities. But how does an airline deliver this modern luxury to flyers who are cruising at nearly 560 mph at more than 6 miles above sea level?
There are two ways for the internet to reach planes:
Air to ground (ATG) system
This system, the first to be developed, works like the ground-based mobile data network you’re accustomed to through your cell phone. But unlike mobile towers that focus signal downward, the towers meant to provide internet to planes project them upward. Antennas fitted under the belly of the plane receive the signal and send them to the onboard server. This server has a modem that converts radio frequency signals into computer signals and vice versa, providing access to passengers through the Wi-Fi access points installed inside the aircraft. Information is exchanged between the plane antenna and the towers along the path of the flight. The towers, in turn, are connected to operation centers run by the service providers which are similar to the control centers of your broadband ISP.
The image above shows the ATG-4 system made by the company Gogo, currently the most installed ATG system among U.S. airlines. Gogo’s coverage spans across North America and includes more than 200 towers.
ATG systems have two significant drawbacks:
They operate on a lower frequency (800 MHz), in which peak data speed per flight is limited to 10 Mbps. In comparison, the average fixed-line internet speed in the U.S. is close to 100 Mbps. When multiple users on a flight are logged in, the speed per user is barely enough to check emails and even that would take forever.
The coverage is spotty in areas where there are fewer network towers, like large patches of desert, and nonexistent above water bodies. This makes the ATG system an unpopular choice for international travel.
Inflight Wi-Fi using satellites is more complicated, but also faster and more reliable.
Instead of under the belly of the aircraft, antennas are installed on the top of the plane. These antennas receive the signal from the satellites that are orbiting the earth. But since the satellite and the aircraft are both moving at incredible speeds and are approximately 22,000 miles apart, the antennas need to constantly adjust their position to be able to receive signals. In addition to an onboard server and Wi-Fi access points, a separate device controls the movement of the antenna based on the flight location and speed. The satellites are linked to ground stations which are further connected to operation centers set up by the service providers.
The two major advantages of satellite-based inflight internet are:
It’s available everywhere except the North and South Poles. In a long-haul flight, the antennas might have to reposition themselves to connect to a different satellite but typically no more than once. This makes a satellite-based system the obvious choice for international travel.
It operates on higher frequencies which allow more bandwidth and speed. The two main frequencies allocated for satellite internet are Ku-band (12–18 GHz) and Ka-band (26–40 GHz). These two bands allow peak bandwidth between 30 to 100 Mbps per aircraft, which is significantly higher than the 10 Mbps offered by ATG systems.
However, there are three main drawbacks with this system:
It’s more expensive, both in terms of equipment, maintenance, and bandwidth costs than the simple ATG system. This makes the satellite option less popular among smaller airlines and airlines on regional routes.
The distance the data has to travel is extremely high, thus increasing the latency. Latency is the time it takes data to travel between its source and destination in milliseconds. Although the overall speed is faster, when you click on a link, there will be a noticeable delay before the page starts loading, but once it starts it will load almost immediately. ATG systems, on the other hand, will start loading almost immediately because of the lower latency but will take a significant time to complete. Here is an infographic showing the mind-boggling distance the data travels (nearly 45,000 miles).
In addition to equipment, installation, and maintenance costs, the other hidden cost posed by an inflight Wi-Fi system is fuel costs. While it might seem trivial, the change in shape caused by the antennas installed on the outside of the plane puts the aircraft at an aerodynamic disadvantage. This increases drag, which increases fuel consumption. Currently, service providers are working toward reducing the size of the antenna to decrease this cost. Gogo’s latest 2Ku antenna is less than 4 inches thick, creating a much smaller bump……..Read More>>