5G is one of the hotly debated topics recently. “Autonomous driving”, “smart home” and “Internet of Everything” are all more or less related to the popularity of 5G. At this time, my country is pressing the “fast forward button” on 5G development, promoting the construction of new infrastructure, deepening integrated development with all walks of life, and contributing to the development of the international digital economy.
Maybe you already know a lot about 5G: wider bandwidth, faster speed, denser base stations, as well as millimeter waves, macro base stations, micro base stations, D2D, etc… Today, the editor will talk to you The other side of 5G.
I believe that in the eyes of many people, “5G = faster network speed” is an upgraded version of “super 4G”. So is 5G just faster than 4G? Maybe the answer is not that simple…
Origin｜Sina
Why is 4G sometimes fast and sometimes slow?
Let’s take a look at 4G first. If you have used 4G, you must have had this experience. On the subway that is crowded with people at peak times in the morning and evening, the 4G network speed of your mobile phone will become extremely slow. Once in an open space, the internet speed will return to normal.
Why does internet speed deteriorate in places with a lot of people? Will there be traffic jams on the Internet? If you want to find out, you also need to see how 4G base stations work.
The electromagnetic waves emitted by a 4G base station will be transmitted to all directions like water waves. These electromagnetic waves contain the information that your mobile phone will receive.
The waves that spread to all corners of the world
When there are many mobile phones connected to this base station at the same time, the base station needs to send the information that everyone needs to read to their respective mobile phones.
At this time, the system will separate the information required by each person, package it into “small packages”, and transmit it to all corners of the country through electromagnetic waves in accordance with the specified order.
4G adopts an 8-input and 8-output mode, which means that the system will divide the information uploaded from the network into 8 small parts and send them out from 8 channels respectively. The recipient collects 8 pieces of information and puts them together to obtain complete information. This is like a two-way line with eight lanes in the forward and reverse directions. Each piece of information split into “small packages” is like a car.
So if there are a particularly large number of connected mobile phones, your internet speed will slow down, just like traffic jams during morning peak hours.
Origin｜Antenna System Industry Alliance
So how to make the Internet speed faster? We have two options!
The first method is very intuitive, which is to send information faster, that is, each car drives faster. Let the limited electromagnetic waves carry more information, which means increasing the bandwidth.
The second method is to build the “road” wider and even register a “dedicated lane” for each mobile phone. This is also the most eye-catching technology in 5G – Massive MIMO and beamforming.
Your exclusive “fast lane”
5G is similar to 4G. It also uses multiple input and multiple output methods to split a huge information into many small parts, which are sent or received in sequence, so that each mobile phone can quickly exchange information with the base station. .
The difference is that 5G has as many as 64 sending channels and 64 receiving channels! By building wider roads, the “congestion” problem will naturally be alleviated. (This is called Massive MIMO skill)
However, the changes in 5G do not stop there.
The electromagnetic waves of the 4G base station are emitted nearly uniformly. The 5G base station will transmit signals aimed at the connected mobile phone.
When the base station “discovers” a mobile phone, it will form a very narrow beam of electromagnetic waves and emit it in the direction of the mobile phone, tracking the mobile phone all the time as it moves. When multiple mobile phones are connected at the same time, it will also emit multiple beams pointed at each mobile phone and track them.
beamforming
Origin｜Antenna System Industry Alliance
Compared with 4G, where we are all bathed in a large-scale electromagnetic wave, 5G provides each mobile phone with its own “exclusive lane”.
What are the advantages of doing this? One is to make the use of electromagnetic wave energy more efficient. It only needs to emit a beam of electromagnetic waves in the direction of the mobile phone. There is no need to emit electromagnetic waves indiscriminately all over the world.
Second, because the electromagnetic waves are concentrated in a very narrow area, the signals that mobile phones can receive will be stronger. Most of these signals are valid, and there will be fewer useless interference signals. We all know that in order to make the Internet speed faster, in addition to increasing the bandwidth as often said, enhancing effective signals is also a feasible method.
Phased array skills and the most powerful radar
Friends who read this may ask, how does 5G achieve the point of electromagnetic beams carrying information pointing at mobile phones and keeping track of them?
This starts with radar.
Whether in games or film and television works, most radars always need to be constantly rotating. This is because early radars could only emit electromagnetic waves in a certain direction for detecting the position of enemy aircraft. In order to monitor the entire sky, the radar base must roll with the transmitting equipment to scan the entire sky.
rotating radar
Origin | Kerbal Space Program
But if you are a military fan, you will definitely find that most modern radars are flat-shaped and generally do not roll. This kind of radar is called phased array radar.
Phased array radar on fighter plane
Origin｜Military Network
phased array radar
Origin｜China News Service
We might as well do such a small experiment. Throw two stones into the water together and observe the ripples of the water. You will find that the water waves are not evenly dispersed in all directions, but have strong fluctuations in some directions, weak fluctuations in other directions, or even no fluctuation at all. This is the nature of waves. The principle of superposition.
Next we still throw two stones into the water, but this time let one stone enter the water first and the other stone enter the water later. You will find that there is still a phenomenon of different strength and weakness of fluctuations, but the direction has changed, as if a certain angle has been rotated.
If you slightly change the time difference between the stones entering the water, you will also find that this perspective will change significantly. In other words, we can control the direction of the distribution of water wave strength by stimulating the time difference between two water waves.
Changing the phase difference can change the beam direction
People call the difference in the sequence of several waves called the phase difference, and the phase difference can change the intensity distribution and direction of the new fluctuation formed by the superposition of these waves. This is the principle of phased array radar.
There are hundreds of electromagnetic wave transmitters on the phased array radar, and they can generate electromagnetic waves independently. By changing the phase difference between hundreds of beams of electromagnetic waves, the direction and intensity distribution of the new electromagnetic waves generated by their superposition can be changed, so that the electromagnetic waves can sweep across most of the sky without the need for the radar base to rotate.
After the phased array radar detects an enemy aircraft, it can also change the phase of each electromagnetic wave so that the final beam will follow the enemy aircraft tightly, leaving it nowhere to escape.
Did you guys think of anything after reading this? That’s right, 5G base stations and phased array radars use the same principle, and your mobile phone plays the role of “enemy plane”.
A base station that does not want to be a phased array radar is not a good 5G
Origin｜Sohu
There are also hundreds of units that emit electromagnetic waves on the 5G base station. By adjusting the phase of the electromagnetic waves, the 5G base station can form many areas with strong fluctuations in space, change their direction, and track your mobile phone at any time. Let the electromagnetic signal with high intensity and low interference be pointed at your mobile phone all the time.
do you know! In addition to 5G phased array technology, it is also used in medical ultrasound imaging, which is what we commonly call B-ultrasound.
In addition to “Massive MIMO” and phased array technologies, the practical use of 5G also involves more detailed technical issues. Interested friends can learn about it for themselves!