FCITR MAGAZINE
IN- FLIGHT WI-FI
Aliaa Mahfooz Alabdali
Faculty of Computing and Information Technology Rabigh Information Technology Department
King Abdulaziz University
Kingdom Saudi Arabia
1. Introduction
Air travel has, for many years, been a largely phone-free zone. We've had to turn off our electronic devices, and rely instead on movies and in-flight magazines for entertainment. Today, connectivity is much more important. Passengers don't just want to admire the view, or complain about a meal to their neighbor - they expect to be able to tweet about it, immediately, complete with pictures. Many airlines are responding. In-flight Wi-Fi is now accessible on around 40% of US flights and on international long haul flights via companies such as Lufthansa, Emirates and Qatar Airways. Norwegian and Turkish airlines even offer the service for free, while Scandinavian airline SAS is testing it on some of its air craft now [1].
2. Gogo
2.1 Definition
Gogo is the biggest Internet service provider (ISP) in-flight broadband Internet service and other connectivity services for commercial and business aircraft [2].
2.2 Connectivity and Performance
Gogo provides continuous coverage with minimal interruptions in speed, detected when passing from one cell tower signal to the next. Gogo's connection speed is approximately 500–600 Kibibits per second for individual users for downloads and 300 Kibit/s for uploads Total bandwidth for all users on the flight is
approximately 3 Mbit/s [2].
2.3 In Flight Wi-Fi Technologies
Below are the ways for an internet signal to reach a device at 35,000 feet:
• Air-To-Ground (ATG)
It is a technology that Gogo currently uses. Gogo's ATG network is a cellular (meaning that there is hand over when
Figure 1: ATG
the aeroplane moves among service areas) radio network that has at least 200 towers in the continental U.S., Alaska and Canada. It delivers peak speeds of 3.1Mbps. The ground stations compose of original Airfone air- ground phone relay stations and newer locations, utilizing the 850 MHz ATG band. This technology is via ground-based mobile broadband
towers as ATG ground stations sends signal up toward the aircraft as seen in Figure (1). The aircraft communicates with the ground stations utilizing an antenna usually located on the bottom of the plane’s fuselage as seen in Figure (2). The antenna transmits and receives signals to and from towers on the ground. Avionics converts between proprietary Gogo protocols and standard Wi-Fi, which is handed out into the
passenger cabin through multiple interior wireless access point (AP) nodes as seen in Figure (3). As the plane moves along its land route, it automatically connects to signals from the nearest tower, so there is (in theory at least) no interruption to the passenger browsing. However, if the passenger passes a large area of water or the terrain is particularly remote, there will be
a problem in the connection [2].
Figure 2: An External Aircraft Antenna
Figure 1
Figure 3: Multiple Interior Wireless Access Point (AP) Nodes
• ATG-4
Gogo has improved to the previous ATG system ATG to a newer technology called ATG-4. It has advantage of multiple antennas compared to ATG as seen in Figure (4). These antennas arranged strategically along the fuselage—to grab signals and offer faster speeds.
Maximum total download bandwidth has increased from 3.1 Mbit/s in ATG to 9.8 Mbit/s in ATG-4 [2].
• Satellite
It solves the ATG networks connectivity problem as satellite has advantage in providing the aircraft with connectivity anywhere around the globe – over land or over water. This makes it possible for passengers to enjoy uninterrupted connection on all their wireless devices, and stream live TV during long-haul flights. The aircraft communicates with a satellite in orbit above the earth utilizing a small satellite antenna usually located on the top of the plane’s fuselage as seen in Figure (5).
• That satellite acts as a constant connection with a ground station to supply the aircraft with a live link to the Internet. As the plane moves along its land route, it automatically connects to the closest satellite in orbit, so there is no interruption to the passenger browsing even with a large area of water or the terrain is particularly remote. Thus, Wi-Fi signal is distributed to plane passengers cabin through wireless access point (AP) nodes as seen in Figure (6).
Figure 4: Multiple External Aircraft Antenna
Figure 5: Satellite Antenna
Satellite networks transmit data at different frequency bands: L-band and Ku- band. L-band – sometimes referred to as narrowband – operates at a frequency bandwidth between 1-2 GHz, and has only 30 MHz allocated for use. Comparatively, Ku-band networks utilize 500 MHz of frequency bandwidth between 11-14.5 GHz [5].
• Ku Band
This technology quite differently as the internet signals are received from Satellites above through Ku band instead of receiving signals from the ground as seen in Figure (7). This technology can transmit data rates at 10-30 Mbps to the aircraft [6].
Figure 6: Satellite Communication
Figure 7: Ku and Satellite
• Gogo Ground to Orbit (GTO)
It is a technology that Gogo currently announced in September 2013. It is new service called Gogo Ground to Orbit (GTO).
Gogo Ground to Orbit uses a Ku-band satellite antenna which installed at the top of the plane to receive the signal from the plane and Gogo's Air to Ground under the plan to return the signal to the Earth as seen in Figure (8).
According to Gogo, this technology can increase speeds up to 60 Mbps [6]. As seen in Figure (9), to get the Internet from a plane, the signal travels from the device to the cabin
wireless access points, to the airborne server, Figure 8: GTO
through the satellite controller equipment to the antenna, then to the satellite and down to one of several ground stations around the world, and finally on to the passenger data centre. This is then done in reverse for data travelling to the plane. Back on the ground, the global network operations centre constantly monitors all of the aircraft in service, along with the status of the satellite ground stations and the data centre.
Figure 9: Gogo Ground to Orbit Communication
• Using satellite for everything is not enough and putting on a new antenna is required anyway.
• The point of using the air-to-ground stuff because it is a lot less expensive, so Gogo wants to use that as much as it can.
• By doing all upload via the ground and download via satellite, Gogo can use a smaller, lighter antenna to communicate with the satellite than it would otherwise. So, receiving data is a lot easier than transmitting it.
• 2Ku
A new technology called 2Ku is currently in works that offer speeds in excess to 70 Mbps [6]. It uses two Ku-band antennas, one for download and the other for upload as seen in Figure (10). It offers improved upload speeds for passengers.
3. Flight Wi-Fi Speed
Back in 2008, the first onboard Wi-Fi service on a Virgin America plane, the 3 Mbps connection was adequate for a few laptops (and streaming video was prohibited).
But now, with every passenger toting at least one device to connect to countless apps, websites and services, there’s a much
greater strain on resources. These days, a satellite connection offers around 12 Mbps.
In-flight Wi-Fi, internet speed is going to catch up 28.9 Mbps in 2016. Upgraded antennas and satellite services, delivering up to 70 Mbps – much faster than the average connection on land. [4]. The chart illustrates the difference in wifi speed between different in-flight wifi technologies.
Figure 10: 2Ku Communication
4. Flight Wi-Fi Cost
All of that technology doesn’t come cheap – and nor do the in-aircraft systems.
Antennas also increase drag, adding fuel costs to the airline’s bill. Those fees – plus engineering and maintenance costs – are usually passed on to customers. The price of in-flight connectivity varies between airlines, although some offer free trials – for example, the first 10MB on an Emirates flight is free [4].
5. Conclusion
In-flight Wi-Fi is getting faster and cheaper, and is an increasingly common offering on budget and flagship airlines alike. There are different wifi speed between different in-flight wifi technologies. Upgraded antennas and satellite services, delivering up to 70 Mbps – much faster than the average connection on land. [4].
References:
[1]. Mike Williams. (2013, Aug 09). How does airplane Wi-Fi work? And will it ever get any better?. Retrieved from http://www.techradar.com/news/world-of-tech/future-tech/how-does- airplane-wi-fi-work-and-will-it-ever-get-any-better-1171510
[2]. Adam Clark Estes. (5 May 2017). Gogo Inflight Internet. Retrieved from https://en.wikipedia.org/wiki/Gogo_Inflight_Internet
[3]. Wikipedia. (2015, Apr 05). Every Major Airline's Wifi Service, Explained and Ranked.
Retrieved from http://gizmodo.com/every-major-airlines-wifi-service-explained-and-ranked- 1701017977
[4]. Hazel Plush. (2017, Jan 30). How does Wi-Fi work at 35,000 feet and why don't all airlines offer it?. Retrieved from http://www.telegraph.co.uk/travel/travel-truths/how-does- inflight-wi-fi-work/
[5]. Altitude serves . (2017, May 9). How-inflight-wifi-works. Retrieved from http://www.connected-altitude.com/services-technology/how-inflight-wifi-works/
[6]. Basant Tomar. (2015, Nov 18). In-Flight Connectivity----Past , Present and The Future.
Retrieved from https://www.linkedin.com/pulse/in-flight-connectivity-pastpresent-future- basant-tomar
