How do mobile phones send short messages through electromagnetic waves?

Mobile phones do send short messages by sending electromagnetic waves directly to the base station. The transmitting power of the mobile phone can cover as far as the base station!

Let alone send text messages. When a mobile phone makes a call, the voice of the other party is provided to your mobile phone by electromagnetic waves emitted by the base station. Where's your voice? Of course, the mobile phone sends electromagnetic waves to the base station. This shows that the radiation of mobile phone can definitely reach the base station.

There is a lot of communication between mobile phones and base stations. Such as the most basic power determination.

The transmitting power of mobile phone is not constant. The mobile phone sends signals to the base station, and the base station keeps sending signals to the mobile phone. The symbol of the signal strength on the mobile phone is that it evaluates the signal strength received from the base station and gives it. You can see that the signal intensity displayed on the mobile phone can change within a few seconds after you enter the room, which means that the base station will send a signal to the mobile phone in at least a few seconds, even if you don't call or send a text message.

Similarly, at the request of the base station, the mobile phone will also send signals to the base station regularly. After evaluating the cell phone signal, the base station will send a signal to the cell phone again, telling it that your power is too small or too large. The mobile phone will adjust its transmission power accordingly.

Therefore, the communication between the mobile phone and the base station helps the mobile phone to determine its own transmission power. Mobile phone power will be low in cities and high in remote mountainous areas.

The "signals" mentioned above are all transmitted by electromagnetic waves between mobile phones and base stations.

Texting, too?

First, the mobile phone sends a request to the base station,

The base station will reply to this request and say that it can be sent.

If the mobile phone does not receive the request, it will resend the request. If there is no reply after repeated retransmissions, the sending error will be displayed, and some mobile phones will display invalid services (my mobile phone is it).

Then after receiving this request, the mobile phone modulates the short message into electromagnetic waves and sends them to the base station.

After receiving it, the base station will reply to the mobile phone with a report saying, I received the short message you sent, and what is its length?

If the mobile phone doesn't receive this report, it will resend it. If it resends many times and still doesn't receive a reply, it will show that sending failed.

So sometimes, you send a text message, but the other party receives two identical ones. This is because when the other party's mobile phone sent the first message, it didn't receive the system reply, so it was sent again.

If the mobile phone receives the report from this base station, it will tell the user that the transmission is successful.

If you ask for a report, that is, the other party receives a text message to reply to your report, then there are still some behind, so I won't go into details.

In this way, although you sent a short message, there were many responses between the base station and the mobile phone.

The same is true for receiving text messages. Generally, the base station will send the short message directly to the mobile phone, but the mobile phone will give the base station a reply saying that I received it. If the base station does not receive this reply, it will continue to send.

For example, if your mobile phone message is full, then the mobile phone will not tell the base station that I received it, and then when your message is deleted, the message retransmitted by the base station will reach your mobile phone. When the base station receives this reply, it thinks that you have received the message and will not resend it.

In other words, accepting SMS is also a reply between the mobile phone and the base station, rather than a simple sending and receiving process of the base station.

Perhaps this form of repeated signaling confirmation is what you see as a handshake.

Electromagnetic waves have nothing to say. The signals sent between the mobile phone and the base station just mentioned are all transmitted between them in the form of electromagnetic waves.