ScotRail has teamed up with Cisco for the Project Swift experiment, which could be spread to other routes if successful.
It is also claimed to be the fastest train wi-fi in the world, at up to 300 Mbps - ten times as fast as current ScotRail wi-fi.
Cisco said passengers would be able to download the entire Beatles back catalogue in fewer than two minutes.
Coverage should be uninterrupted through tunnels and cuttings.
The trial is expected to start in October or November and run until the end of March.
ScotRail spokesman Rob Shorthouse said: “Our customers consistently tell us that one of the things that they expect on their journey is fast, reliable wi-fi.
“This pilot scheme, which we are undertaking on behalf of the entire rail industry, will allow us to fully understand how we take our current on-train wi-fi to the next level.”