How does the Wifi in the trains works?

Nowadays the internet connections in the trains trips are available and anybody can sign in and enjoy the time. The Wifi technology in the trains are connected to the network coverage of the base stations (BTS) of the cellular phones, but I noticed when I am in the train in rural regions where the network coverage are very weak or there no network coverage, the Wifi connections inside the train are not disconnected.
How do the Wifi connections in the trains in the rural regions work?

The WiFi connection is only from the station inside the train, in fact there are probably several along the length of the train. The connection travels with the train so the signal should always be strong but the internet connection to the cell stations may drop or be slow occasionally. By utilising the length of the train, there may be several cell modems communicating with the base station so the problem of 'not spots' is reduced.

Brian.

thanks for your reply.
That means that the internet connections are not supported by the base stations of the cellular phone?

I do not understand this point. How can the length of the train be utilized?

The cell base stations work in exactly the same way as a single mobile phone would use them. They provide the 2G/3G/4G to the device connected to them, whether that be a single phone or a network within a train. The wireless router on the train communicates with the base station and relays the signal as Wifi to people on the train. It uses NAT to ensure each person seems to get an individual connection when really they are all sharing the one base station signal.

Imagine the cell signal was visible, like a fog. The fog would be almost everywhere but thicker and thinner in patches because of the effects of the terrain, for example it would be thinner where something obstructed the signal and thicker where there was a line of sight to the base station mast. Add to that the effects of reflections where the signal bounces off the surroundings and either reinforces or cancels the signal. The 'fog' would be very variable, even over distances of a few cm. To improve the reliability on a train, there are multiple antennas (possibly multiple routers cooperating with each other) along it's length so the chances that at least one of the antennas picking up a signal is vastly improved. It's the physical separation that improves the chances of a reliable connection.

Brian.