When we traveled FT we had a Wilson Electronics antenna that we used to boost signals with.
IF we could get a 'tower' on cell phone the antenna would allow us to get 2 bars at least.
Antenna was on a pole that I attached to ladder and ran cable in thru rear window. We then had adapters that connected to antenna cable and allowed us to plug into cell phone external antenna plug and one that allow us to plug into air card external antenna plug.
BUT that is old school .............
I'm sure more tech savvy folks will info you about modems, tethering, jetpacking or whatever is the hot ticket now