What is the principle of sending and receiving short messages?

As simple as telephone signals, telephone signals are low-frequency audio signals, which are transmitted through mobile phones. It is transmitted to the main room through the signal tower, decoded by the main room and sent to the tower. The short message sent by the tower to the person you want to call is slightly different, because the short message is valid, that is to say, the signal text information signal belongs to the short pulse signal sent by you. When the other party is turned on, the letter will be sent as mentioned above, but when the other party is turned off, the letter will be stored in the database of the terminal and sent when it is turned on. Of course it will be soon. Don't forget that the propagation speed of electromagnetic waves is 3 times 10 to the eighth power. It can reach 300 thousand kilometers in a second. The speed of light, of course.