What is the science behind mobile phones?

Solid state micro-circuitry and microwave transmission and reception.

The fundamental principals are the venerable principals of radio, including microwave transmission and reception, modulation and demodulation. To these engineers added the principals of detection and estimation theory, or simply signal processing, which allowed efficient use and sharing of the scarce resource of the electromagnetic spectrum. Next the developments in micro-circuitry and digital processing including software made networks and mobile phone instruments practicable. The principals of communications, that is signaling through layered architectures, are essential to the success of modern cell phone systems.