This is the first time someone has made 5G so simple and clear

1

A simple and magical formula

Today’s story starts with a formula.

It's a formula that's both simple and magical. It's simple because it only has 3 letters in total. It is said to be magical because this formula contains the profound secrets of communication technology, and countless people on this planet are obsessed with it.

This formula is it——

I believe many students recognize this formula. If not, and you are a science student, please remember to call your middle school physics teacher when you have time!

Please explain, the above formula is the basic formula of physics.Speed ​​of light = wavelength & times; frequency.

For this formula, we can say:Whether it is 1G, 2G, 3G, or 4G or 5G, everything remains the same. They all make a fuss about it and do not jump out of its "Five Finger Mountain".

Let me tell you slowly.

2

wired? wireless?

Communication technology, no matter what black technology or white technology, in the final analysis, can be divided into two types——Wired communications and wireless communications.

When I talk to you on the phone, information and data are either transmitted in the air (invisible and intangible) or in physical objects (visible and tangible).

If it is transmitted on physical materials, it is wired communication, which basically uses copper wires and optical fiber cables, collectively called wired media.

When data is transmitted over wired media, the rate can reach very high values.

Taking optical fiber as an example, in the laboratory,The maximum speed of a single optical fiber has reached 26Tbps. . . It is 26,000 times that of traditional network cables. . .

optical fiber

The air propagation part is the bottleneck of mobile communications.

The current mainstream mobile communication standard is 4G LTE, with a theoretical rate of only 150Mbps (excluding carrier aggregation). This is completely incomparable to wired.

Therefore, if 5G wants to achieve high end-to-end speeds, the focus is to break through the bottleneck of the wireless part.

3

What a magical wave

As we all know, wireless communication uses electromagnetic waves to communicate. Radio waves and light waves are both electromagnetic waves.

The functional characteristics of electromagnetic waves are determined by their frequency.Electromagnetic waves of different frequencies have different properties and characteristics, and thus have different uses.

For example, high-frequency gamma rays are very lethal and can be used to treat tumors.

constant frequency of electromagnetic waves

We currently communicate primarily using air waves. Of course, light wave communications are also on the rise, such as LiFi.

LiFi（Light Fidelity），可见光通信

Without digressing, let’s go back to the radio wave first.

Radio waves are a type of electromagnetic waves, and their frequency resources are limited.

In order to avoid interference and conflicts, we further divide the lanes on the radio wave highway and assign them to different objects and uses.

The uses of radio waves at different frequencies

Please pay attention to the red font in the picture above. Until now, we have mainly usedMedium frequency to ultra high frequency are used for mobile phone communication.

For example, the often mentioned "GSM900" and "CDMA800" actually refer to GSM operating in the 900MHz frequency band and CDMA operating in the 800MHz frequency band.

The current global mainstream 4G LTE technical standard belongs toUHF and UHF.

Our country mainly uses UHF:

As you can see, with the development of 1G, 2G, 3G, and 4G, the frequency of radio waves used is getting higher and higher.

Why is this?

This is mainly because,The higher the frequency, the richer the frequency resources that can be used.The richer the frequency resources, the higher the transmission rate that can be achieved.

Higher frequency → more resources → faster speed

It shouldn’t be difficult to understand, right? Frequency resources are like carriages. The higher the frequency, the more carriages there are and the more information can be loaded in the same time.

So, what is the specific frequency used by 5G?

As shown below:

The frequency range of 5G is divided into two types: one is below 6GHz, which is not much different from our current 2/3/4G. There is another kind, which is very high.Above 24GHz.

Currently, internationally, it is mainly used 28GHz Conduct experiments (this frequency band may also become the first commercial frequency band for 5G).

If calculated based on 28GHz, according to the formula we mentioned above:

Okay, this is the first technical feature of 5G——

4

millimeter wave

Please allow me to repost the frequency comparison table just now:

Please pay attention to the bottom line. Is it "millimeter wave"?

Go on, go on!

Okay, since high frequency is so good, you will definitely ask:"Why didn't we use high frequencies before?"

The reason is simple - it's not that I don't want to use it, it's that I can't afford it.

The salient characteristics of electromagnetic waves: the higher the frequency, the shorter the wavelength, and the closer it is to linear propagation (the worse the diffraction ability).The higher the frequency, the greater the attenuation in the propagation medium.

Look at the laser pointer (wavelength is about 635nm). The light emitted is straight. If it is blocked, it will not be able to pass through.

Looking at satellite communications and GPS navigation (wavelength is about 1cm), if there are obstructions, there will be no signal.

The big pot of a satellite must be calibrated to aim at the direction of the satellite, otherwise even a slight deviation will affect the signal quality.

If mobile communications use high frequency bands, then its biggest problem isThe transmission distance is greatly shortened and the coverage capability is greatly weakened.

covering the same area,The number of 5G base stations required will greatly exceed that of 4G.

What does the number of base stations mean? Money! Invest! The cost!

The lower the frequency, the cheaper network construction will be and the more favorable the competition will be. This is why, in recent years, China Telecom, China Mobile, and China Unicom have been fighting fiercely for low-frequency bands.

Some frequency bands are even called——Golden band.

This is why, in the 5G era, operators are desperately fighting against equipment manufacturers, hoping to reduce the price of base stations.

Therefore, based on the above reasons, in order to reduce the cost pressure on network construction under the premise of high frequency,5G must find a new way out.

What are the ways out?

First, there is the micro base station.

5

micro base station

There are two types of base stations, micro base stations and macro base stations. Just by looking at the names, you can tell that the micro base station is very small and the macro base station is very large!

Macro base station:

Common outdoors, build one to cover a large area

Micro base station:

Doesn’t it look cool?

There are even smaller ones, as big as a palm

In fact, there are many micro base stations now, especially in urban areas and indoors, where they are often seen.

In the 5G era, there will be more micro base stations, which will be installed everywhere and can be seen almost everywhere.

You will definitely ask, will there be any impact on the human body if there are so many base stations around us?

My answer is - no.

In fact, contrary to traditional understanding, in fact,The greater the number of base stations, the smaller the radiation!

Think about it, in winter, in a house with a group of people, is it better to have one high-power heater or several low-power heaters?

High power solution▼

Low power solution▼

The picture above is clear at a glance.The base station is small and low-power, which is good for everyone.If you only use one large base station, if it is close, the radiation will be large, but if it is far away, there will be no signal, which is not good.

6

Where did the antenna go?

Have you noticed that mobile phones used to have very long antennas, and early mobile phones also had small protruding antennas. Why do our mobile phones now have no antennas?

In fact, it’s not that we don’t need antennas;The antenna got smaller.

According to the antenna characteristics, the antenna length should be proportional to the wavelength, approximately between 1/10~1/4.

As time changes, the communication frequency of our mobile phones is getting higher and higher, the wavelength is getting shorter and shorter, and the antennas are also getting shorter!

For millimeter wave communication, the antenna has also become millimeter level. . .

This means that the antenna can be inserted into the mobile phone, or even many antennas can be inserted. . .

This is the third biggest killer feature of 5G——

7

Ｍassive MIMO

(Multi-antenna technology)

MIMO is "Multiple-Input Multiple-Output" (Multiple-Input Multiple-Output), multiple antennas transmit and multiple antennas receive.

In the LTE era, we already had MIMO, but the number of antennas was not large. It could only be said to be a junior version of MIMO.

In the 5G era, MIMO technology continues to be developed, and now it has become an enhanced version of Massive MIMO (Massive: large-scale, massive).

There are multiple antennas packed into a mobile phone, not to mention a base station.

In the past, base stations only had a few antennas:

In the 5G era, the number of antennas is not calculated by root, but by "array". . . "antenna array". . . At first glance, it has the rhythm of trypophobia. . .

However, the distance between antennas cannot be too close.

Due to antenna characteristics, a multi-antenna array requires that the distance between antennas be maintained at more than half a wavelength. If the distance is close, they will interfere with each other and affect the sending and receiving of signals.

8

beamforming

Everyone has seen a light bulb glow, right?

In fact, when the base station transmits a signal, it is a bit like a light bulb glowing.

The signal is emitted to the surroundings. For light, of course it illuminates the entire room. If you just want to illuminate a certain area or object, then most of the light is wasted. . .

The same goes for base stations, where a lot of energy and resources are wasted.

Can we find an invisible hand to bind the scattered light?

This not only saves energy, but also ensures that the area to be illuminated has enough light.

The answer is: yes.

This is - beamforming

An antenna array is arranged on the base station, and by controlling the phase of the radio frequency signal, the lobe of the electromagnetic wave after interaction becomes very narrow and pointed at the mobile phone it provides services, and can change the direction according to the movement of the mobile phone.

This spatial multiplexing technology changes from omnidirectional signal coverage to precise directional service without interference between beams.Provide more communication links in the same space, greatly improving the service capacity of the base station.

Straight ones can be broken into curved ones. . . Is there anything else that communication experts can’t do?

9

Don't charge me any money, okay?

In the current mobile communication network, even if two people call each other's mobile phones face to face (or send photos to each other through mobile phones), the signals are relayed through the base station, including control signaling and data packets. . .

In the 5G era, this is not necessarily the case.

The fifth major feature of 5G is D2D, which is Device to Device.

10

Ｄ２Ｄ

In the 5G era, if two users under the same base station communicate with each other, their data will no longer be forwarded through the base station, but directly from mobile phone to mobile phone. . .

In this way, a large amount of air resources are saved and the pressure on the base station is reduced.

However, if you think you don’t have to pay, then you are doing Tucson a disservice.

Control messages still have to go from the base station. You are using spectrum resources. How can the operator let you go? . .

postscript

I believe that through this article, everyone has a deep understanding of 5G and the communication knowledge behind it. And all of this is just based on mathematical formulas that a primary school student can understand. Isn't it?

Communication technology is not mysterious. As the most dazzling gem in the crown of communication technology, 5G is not an out-of-reach innovative revolutionary technology. It is more of an evolution of existing communication technology.

As an expert said -

The limits of communication technology are not limitations in technical technology, but inferences based on rigorous mathematics. It is basically impossible to break through in the foreseeable future.

How to further explore the potential of communications within the scope of scientific principles is the tireless pursuit of many strivers in the communications industry.

Okay, that’s it for today.

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