To understand how mobile phones can make wireless calls, we can first understand how landlines make wired calls.
Telephone is a communication technology through the mutual conversion of sound energy and electrical energy, and the use of \"electricity\" this medium to transmit language. To communicate between two users, the simplest form is to connect two telephones with a pair of lines. When the speaker picks up the telephone to speak to the microphone, the vibration of the vocal cords stimulates the air to vibrate, forming sound waves, and the sound waves act on the microphone, making it produce current, called voice current, and the voice current is transmitted along the line to the receiver of the other phone, and the receiver is just the opposite of the transmitter - the current is converted into sound waves, transmitted to the ear through the air. In this way, the simplest call process is completed.
The wireless call between mobile phones is to replace the cable in the wired phone with wireless, and the replacement way is to replace the current with electromagnetic waves.
The communication between the mobile phone and the base station is an important step to realize the mobile phone wireless call, the mobile phone and the base station communicate through electromagnetic waves, the mobile phone and the base station have their own transmitters and receivers, and then communicate through different modulation and coding methods, which is what we usually call different standards, GSM and CDMA in the 2G era. WCDMA and TDS in the 3G era, TDD and FDD-LTE in the 4G era, of course, the core network is different in different times, and the adjustment coding method on the wireless side is also different.
The basic model of wireless communication is like this, and the specific wireless side interaction is a deep knowledge, which requires deep exploration and learning.
The number signal dialed by the user is converted into a unified format signal, and then transmitted by radio waves. When the nearby base station receives the signal, after a certain processing, the signal is restored, and the other communication equipment of the base station is connected to the other party's phone. If the other party is a fixed telephone, then the signal should be communicated with the wired telephone network through the city long-distance telephone program control exchange; If the other party is also a mobile phone, then the base station will receive the signal to other base stations, all the base stations will forward your signal once. As long as the other party is within the range of a certain base station radio wave, the two sides can talk on the phone.