From the ground to the sky, maybe this is the future of mobile phones?

Introduction

In ancient times, people basically communicated by shouting, which was not only time-consuming but also the sound could not be transmitted far.

Modern people can transmit messages over thousands of miles with just a mobile phone, which is convenient and fast.

Many people believe that with a good mobile phone, they can fully enjoy the joy of communication.

However, things are not that simple. Communication is a complex system and a huge network.

For a phone call to be connected, the signal may need to travel over mountains and across clouds.

Wherever you look, you see territory

Convenient communication is due to the huge number of base stations supporting the network.

By the end of 2022, the total number of base stations in our country will exceed 12 million , of which the number of 5G base stations will exceed 2.31 million.

Walking on the busy streets, strolling in the quiet park, riding on the speeding train, no matter where we are, we can take out our mobile phones and keep in touch at any time.

Whether it is for work or entertainment, when we are busy and having fun, our mobile phones are actually also busy.

Every mobile phone that is operating normally is establishing connections with the surrounding base stations.

When a mobile phone is turned on , it will send a signal to the nearest base station and submit a registration request to the core network. Only after the core network passes the inspection, the mobile phone is officially connected to the communication network.

Base stations are usually placed at high places, and the signal is like an invisible fishing net looking down, providing communication services to mobile phones within the coverage area.

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

When the phone moves , it will switch from the coverage of one base station to the coverage of another base station. The base station will trigger the switching process according to the strength of the signal and switch the phone to the radiation range of the base station with a stronger signal. During the entire switching process, the video or game you are watching will be seamlessly transferred to the new wireless access network without you noticing.

Little A, who is watching the ice lanterns in the cold north, wants to make a video call to Little B, who is basking in the sun in the warm south, to share their happiness.

The transmission of signals will go through a journey across mountains and rivers:

Little A also wants to make a video call to Little C who is building a road in the Gobi Desert. Can the call go through?

Little A also wants to make a video call to Little D who is doing a scientific expedition in the vast ocean. Can the call go through?

Although humankind's conquest of nature has spread across the globe, erecting base stations on the ocean, on the mountains, or in the desert is very difficult and seemingly unnecessary.

If there are some places on the ground where base stations cannot be built, what about the sky?

Look up to the sky, aim high

As early as 1957, when the first artificial satellite flew into the sky, humans had expanded the scope of communications to the sky.

In order to achieve communication between the ground and the satellite, the initial ground terminal was like a big and clumsy pot.

It was not until more than 30 years later that mobile terminals specifically for communicating with satellites appeared. We call them: satellite phones, and this name has continued to this day.

Yes, from the name, we can tell that its main function is: making phone calls.

With satellites, communications can be successfully conducted across the vast ocean and the Gobi Desert.

Satellite phones have their own unique advantages:

No longer dependent on ground base stations .

The signal from a satellite phone can pass through the sea of ​​clouds and connect to the satellite above your head, so you can make calls anytime and anywhere, even to people on the other side of the earth.

If the communication satellite is in a low orbit , it 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 satellite phone communication network covering the entire world, tens of thousands of low-orbit communication satellites need to be sent.

If a communication satellite is located in a synchronous fixed-point orbit as high as 36,000 kilometers , it can rotate synchronously with the earth, which is equivalent to being fixed. The antenna coverage of this type of communication satellite is large, and only three satellites are needed to cover the entire world and achieve 24-hour communication.

Satellites use dedicated operating frequency bands and are managed uniformly by the International Telecommunication Union (ITU-R).

ITU-R strictly regulates and approves applications for each satellite operating frequency band. Generally, it is necessary to apply for satellite orbit resources/satellite communication operating frequency resources at the same time.

The current satellite operating frequency range is: 1GHz~40GHz. Please see the table below for the divided operating frequency bands.

Complement each other's strengths and weaknesses, and transform into a whole

If you have an apple and I have a pen, can we combine them into an apple pen?

Haha, although it's just a joke, this method of learning from each other's strengths and overcoming each other's weaknesses is a best practice for continuous experimentation and progress in science and technology.

What will a "satellite phone" look like when it is a combination of a smartphone and a satellite phone? It's really exciting.

Will such satellite phones be far away from us?

There is still a long way to go before satellite phones can enter ordinary people’s homes.

01 Frequency Band

Although existing smartphones already support many frequency bands, satellite phones need to support more satellite frequency bands if they want to communicate with satellites.

The following are the frequency bands supported by a certain smartphone:

02Signal

The base stations on the ground are very close to us, so the antennas of mobile phones can be hidden. The satellites in the sky are very far away from us, and to maintain sufficient signals, we currently use external antennas.

We need a strong signal and a small antenna. Only humans who love to tinker with things would raise this difficult problem and work hard to solve it.

03 Cost

It costs money to launch a satellite into space, and it costs money to maintain the satellite communication system, both of which are considerable sums.

Nowadays, few people use satellite phones and there are fewer satellites, so of course the Internet speed is low and the cost is high.

If more people use satellite phones and more satellites are in the sky, then of course the Internet speed will gradually increase and the cost will gradually decrease.

After all, smartphones have also developed along the same path. From the initial price of more than ten yuan for 1MB to the current price of a few yuan for 1GB, the difference is like heaven and earth.