Need formula to selecting coaxial cable type and GSM antenna
It is very simple. You should convert any amplifier and attenuation in dB format. and formula is like this
Receiver_signal(dB)=Signal_at_antenna(dB)+Antenna_gain(dB)-Cable_Loss(dB)-other_loss(dB)
As your Receiver_signal should be above minimum signal strength with a margin for example(15 dB). Place this amount for Receiver_signal and compute Maximum cable loss. Cables are standards. Please find cable loss at this table. So you can find which cable is suitable for your work.