Recently I had a flight to Singapore on a SilkAir plane equipped with free Wi-Fi on board providing a streaming access to a selection recent movies, TV short features and some music for all passengers, but no access to Internet which is the very costly part in an airplane. SilkAir is the short-haul carrier of Singapore Airlines which operates a fleet of Airbus A320 and Boeing B737-800 aircrafts.

That is an interesting evolution of commercial airlines policies to see that we are moving from “zero electronic equipment should be turned on aboard aircrafts” to “please enjoy our high capacity free Wi-Fi access points and turn on your smartphones / tablets / laptops” (except Galaxy Note 7, or you might see your plane perform an emergency landing on the nearest airport).

Here is a quick review of the SilkAir Wi-Fi service on this blog:
SilkAir’s best-kept “secret”: FREE in-flight entertainment with SilkAir Studio

When I saw this, I wanted to have a better idea of what the constraints would be to dimension such system to work properly in those conditions:
– High density of users (around 142 seats on the planes depending on configuration)
– High throughput consumption (live video streaming mainly and some music)

What about interference? and number of simultaneous connected users?

Quick review of the technical setup

The system provides 2 separate SSID silkair1 and silkair2. You can chose either of them to connect. Unfortunately I forgot to check what was the frequency band used by the access points. I would assume though that they would use 2.4 GHz rather than 5 GHz.

(illustration credit: http://thepointsguy.com/2015/11/how-in-flight-wi-fi-works/)

The server provides various services:

  • 21: ftp, 22: ssh, 53: dns
  • 80 and 443: http and https, seems to be on the popular nginx webserver
  • 554:  rtsp, 873: rsync
  • 3306: mysql, 7070: realserver, 7911: (unknown)

To use the service, you need to download a mobile app from the local server, which means you also need to allow your phone to install apps from untrusted sources, which is not an ideal but understandable considering you don’t have a connection to Internet.

Hopefully next time I fly SilkAir I will have enough battery on my smartphone to look into this in more details.