Shulou(Shulou.com)11/24 Report--

Introduction: people in ancient times, communication basically depends on roar, do not talk, the sound is not far away.

Modern people, as long as a mobile phone, can transmit sound thousands of miles, convenient and fast.

Many people think that if you have a good mobile phone, you can enjoy the joy of communication.

However, it is not that simple. Communication is not only a complex system, but also a huge network.

The connection of a phone may require a signal to cross the mountains and soar through the clouds.

The eyes are all convenient communications in the territory, because there are a large number of base stations to support the network.

By the end of 2022, the total number of base stations in our country has exceeded 12 million, including more than 2.31 million 5G base stations.

Walking on a busy street, walking in a quiet park, riding on a speeding bullet train, no matter where we are, we can take out our cell phones and contact us at any time.

Whether for work or entertainment, we are so busy that our mobile phones are also busy all the time.

Every working mobile phone is connected to the surrounding base station.

As soon as the phone is turned on, it will send a signal to the nearest base station and submit a registration request to the core network. After the core network check is passed, the mobile phone will be officially connected to the communication network.

The base station is usually placed in a high place, and the signal looks down like an invisible fishing net, providing communication services for mobile phones within coverage.

Even if we stay within the coverage of a base station and do not change our location, in order to avoid losing contact with the communication network, the mobile phone needs to trigger the registration update process periodically, and the core network will regularly ask whether the mobile phone is online through the base station.

When the mobile phone moves, it will switch from the coverage of one base station to the coverage of another base station. According to the strength of the signal, the base station will trigger the handover process and switch the phone to the radiation range of the base station with stronger signal. During the whole switching process, the video / games being played will be seamlessly transferred to the new wireless access network, and we have no perception.

Xiao A, who watches ice lanterns in the cold north, wants to make video calls to Xiao B, who is basking in the sun in the warm south, to share their happiness.

The transmission of the signal will experience a journey across mountains and rivers:

Xiao An also wants to make a video call to Xiao C, who is engaged in road construction in the Gobi Desert. Can you get through?

Xiao An also wants to make a video call to Xiao D, who is engaged in scientific research and navigation in the boundless sea. Can you get through?

Although the pace of human conquest of nature has spread all over the world, it is difficult and unnecessary to erect base stations on the sea / in the mountains / in the desert.

If even some places on the ground cannot build base stations, what about the sky?

Looking up at the sky, the goal is high as early as 1957 when the first man-made earth satellite flew into the sky, and human beings have extended the field of communication to the sky.

In order to realize the communication between the ground and the satellite, the ground terminal at the beginning is like a big and stupid pot.

It was not until more than 30 years later that there was a mobile terminal specializing in satellite communication, which we call satellite phone, and this term continues to this day.

Yes, from this name, we can see that its main function is to make a phone call.

With the satellite, the vast sea and the Gobi Desert can also communicate successfully.

Satellite phones have their own unique advantages:

No longer dependent on ground-based base stations.

The signal of the satellite phone can pass through the sea of clouds and connect with the satellite overhead, even with people on the other side of the earth.

If the communication satellite is in low orbit, then the communication satellite is moving relative to the ground, and the area covered by the satellite antenna is small and constantly changing, resulting in short communication time. In order to build a global satellite telephone communication network, tens of thousands of low-orbit communication satellites need to be sent.

If the communication satellite is in a synchronous fixed-point orbit as high as 36000 kilometers, it can rotate synchronously with the earth, which is equivalent to being fixed. The antenna coverage of this kind of communication satellite is so large that it only needs three satellites to cover the whole world and achieve 24 hours of all-day communication.

The satellite uses a dedicated working frequency band and is uniformly managed by the ITU ITU-R.

ITU-R strictly regulates and approves the application of each satellite working frequency band. In general, it is necessary to apply for satellite orbit resources / satellite communication working frequency resources at the same time.

The current working frequency range of the satellite is: 1GHz~40GHz, the working frequency band is divided in the following table.

When you have an apple and I have a pen, can it be applepen?

Haha, although it is a joke, this method of learning from each other's strong points to offset one's weaknesses is a best practice in which science and technology is constantly trying and improving.

The combination of smart phone and satellite phone is "satellite phone". What will it look like? Can not help but think about it, very much looking forward to it!

Will such satellite phones be far away from us?

There is still a long way to go before satellite phones have flown into the homes of ordinary people.

Although existing smartphones already support many frequency bands, satellite phones need to support more satellite bands in order to communicate with satellites.

The following are the bands supported by a smartphone:

02. The base station on the signal ground is very close to us, so the antenna of the mobile phone can be hidden. The satellite in the sky is far away from us, and it is currently solved by external antennas in order to maintain enough signals.

The signal should be strong and the antenna small. This kind of problem, which is both necessary and necessary, will only be put forward by human beings who "love to toss about" and will try their best to solve it.

It costs money to launch a satellite, and it costs money to maintain the satellite communication system, which is a lot of money.

Nowadays, few people and satellites use satellite phones, but of course, the Internet speed is low and the cost is high.

Well, if there are many people using satellite phones and there are many satellites in the sky, of course, the Internet speed will gradually increase and the cost will gradually drop.

After all, smart phones also come this way, from the original 1MB of more than ten yuan to the current 1GB of a few yuan, it is simply the difference between heaven and earth.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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