Improving WiFi signal in tunnels and underground trains

[akerkarprashant]

TL;DR

WiFi signal strength in Tunnels & Subways.

As we see the WiFi signal strength is very low as observed in Tunnels, Subways & Undergrounds while we travel in a train or walk. We do not get the wireless network.

Can there be any technical solutions for increasing the Wireless signal strength in these areas?

Can this be considered a technological barrier?

 

[Baluncore]

As we see the WiFi signal strength is very low as observed in Tunnels, Subways & Undergrounds while we travel in a train or walk. We do not get the wireless network.

Many tunnels have a "leaky feeder" system that provides continuous WiFi, phone and radio throughout the tunnel.
https://en.wikipedia.org/wiki/Leaky_feeder
I do not believe there is a technological barrier, it has simply not been implemented in your sample of tunnels. Where are the tunnels that need it ?