You can go to the settings with your Android phone, then about the phone, status, and signal strength. Anything above -90 means communication is possible, but -50 to -40 means an excellent signal. With an iOS phone, you can dial *3001#12345#*. The number on the upper left-hand corner shows the signal strength indicator. A number that is closer to zero indicates a stronger signal. You can also download a specialized app like Opensignal to test network strength.