[Jonnax]

Sounds like he was talking about something specifically to their network.

There's not some magic thing that everyone should be doing that will give 100% cell coverage.

It's a two way radio. The transmitter needs to talk to the phone. But the phone also needs to talk back.

Also carriers have different frequency spectrums allocated to them.

A carrier using 900MHz has to have fewer base stations than one operating using 1800MHz because lower frequencies transmit further.

They also are able to go underground and through walls better.