Why is there no signal in the underground?
Why is there no signal in the underground? High-frequency signals, like the ones used by mobile phones, are easily blocked by thick barriers of concrete or soil.
Is there 4G in the underground?
Currently around 10% underground tube stations have 4G and 5G mobile coverage. The first Tubes stations in London's West End have received high-speed mobile coverage. 4G and 5G is available at Oxford Circus and Tottenham Court Road ticket halls and on the Central line between the stations.