Why is the deployment of 5G millimeter wave in China later than in Europe and the United States, which Ren Zhengfei has already said is a good thing?

The story starts with what Ren Zhengfei said. In a recent interview with CCTV, he mentioned, "There are very few manufacturers in the world that can make 5G, and Huawei is the best. There are very few manufacturers in the world that can make microwaves, and Huawei is the most advanced. There is only one company in the world that can combine 5G base stations with the most advanced microwave technology into one base station, and that is Huawei."

At that time, everyone was paying attention to Ren Zhengfei's answers to other questions, but no one clearly explained what "microwave" was. Leifeng.com couldn't help but wonder, what exactly is microwave?

Microwave has a very broad definition. It can refer to electromagnetic waves with a frequency of 300MHz~300GHz, corresponding to a wavelength between 1mm and 1m. The microwaves that Ren Zhengfei mentioned here mainly refer to millimeter waves.

Communication is the process of encoding and decoding, modulation and demodulation, encryption and decryption. Electromagnetic waves carry all kinds of information and are the foundation of wireless communication. Globally, there are only two frequency bands for 5G deployment: sub-6GHz, which refers to the frequency band below 6GHz, and millimeter wave.

As the name suggests, millimeter waves are electromagnetic waves with a wavelength of 1 to 10 mm, corresponding to a frequency of 30 to 300 GHz. For reference, the frequency band currently used by 4G is 2000 MHz, and 2G and 3G are even lower.

Whether it is the 2G/3G or 4G era, millimeter waves have always been there, and their history can even be traced back to the 1890s. However, for a long time, millimeter waves were only active in university laboratories and were merely theoretical explorations.

Leifeng.com learned that to this day, the main applications of millimeter waves are still satellite communications, radars, and some military applications, such as early applications in radio astronomy, 77 GHz automotive anti-collision radar, etc. However, in the 5G era, millimeter waves are finally going to "turn over and let the serfs sing."

Excerpted from Baidu Encyclopedia

The reason why 5G uses millimeter waves is simple and pure. There are abundant spectrum resources above 30GHz. According to the conversion relationship, 1GHz=1000MHz, 1MHz=1000kHz. The spectrum resources of millimeter waves are increased by an order of magnitude.

In the past, there were two main reasons why millimeter waves were not developed. First, the commercial demand was not large, and second, the technology of the entire industrial chain was immature and the cost of use was high.

The arrival of 5G has accelerated this process and made millimeter waves an "optimal solution". The large bandwidth required for 5G is often more than 100M, and operators have a continuous 100M bandwidth as a basic requirement for the development of 5G. In the 5G spectrum allocation plan determined by the Ministry of Industry and Information Technology, China Telecom obtained 5G test frequency resources with a total bandwidth of 100MHz from 3400MHz to 3500MHz; China Unicom obtained 5G test frequency resources with a total bandwidth of 100MHz from 3500MHz to 3600MHz; China Mobile obtained 5G test frequency resources in the frequency bands of 2515MHz to 2675MHz and 4800MHz to 4900MHz.

It can be seen that my country's three major operators have at least 100M continuous bandwidth resources to develop 5G. In contrast, in the 4G era, the spectrum resources of the three major operators were not continuous, and the bandwidth resources were less than 100M.

From 4G to 5G, there is another explosive growth in data, which requires faster transmission speeds. There are generally two ways to increase wireless transmission rates: one is to increase spectrum utilization, and the other is to increase spectrum bandwidth. Increasing spectrum bandwidth is simple and direct, and only requires sufficient bandwidth resources.

The maximum signal bandwidth of wireless communication is about 5% of the carrier frequency. 4G networks are all in the sub 6GHz frequency band, with a maximum available bandwidth of 100MHz and a data transmission rate of no more than 1Gbps. In the millimeter wave frequency band, the available bandwidth is greatly increased, and the data transmission rate has also increased exponentially. In addition, with the improvement of new materials, new technologies and new processes, millimeter waves are finally ushering in large-scale applications in the 5G era.

If millimeter waves were all advantages, they would not have been treated so seriously until now. Millimeter waves belong to the category of "extremely high frequency". The transmission characteristics of electromagnetic waves are that the higher the frequency, the shorter the wavelength, the weaker the diffraction ability, the stronger the penetration ability, and the signal will lose a lot of energy when penetrating, so the transmission distance is shorter. In short, the higher the frequency, the shorter the propagation distance of electromagnetic waves.

Moreover, compared with electromagnetic waves with lower frequencies, millimeter wave signals are particularly attenuated when encountering water, which seriously affects the propagation effect. Studies have shown that, in general, the greater the instantaneous intensity of rainfall, the farther the distance, and the larger the raindrops, the more serious the millimeter wave attenuation. Therefore, when designing millimeter wave communication systems or communication lines, sufficient level attenuation margins need to be reserved.

In order to solve the limitation of millimeter wave transmission distance, several key technologies of 5G have been born or enhanced. The first one is Massive MIMO, which means multiple-input multiple-output (MIMO) antennas. As shown in the figure below, MIMO technology has been applied in the 4G era, but at most there are 8 antennas in the base station and 4 antennas in the mobile phone. If more antennas are placed at the frequency of 4G, they will interfere with each other, which is not worth the loss.

In the ideal propagation model, when the transmission power of the transmitter is fixed, the reception power of the receiver is proportional to the square of the wavelength, the transmission antenna gain and the reception antenna gain, and inversely proportional to the square of the distance between the transmission antenna and the reception antenna.

The millimeter wave band has a high frequency and short wavelength, so the signal attenuation is very serious. The signal power received by the receiving antenna is reduced, the antenna transmission power cannot be increased, the distance between the transmitting antenna and the receiving antenna is not controlled (mobile users may change positions at any time), and the gain of the transmitting antenna and the receiving antenna cannot be increased too much. Therefore, the only solution is to increase the number of transmitting antennas and receiving antennas. Moreover, the millimeter wave wavelength is short and the interference distance between each other is small, so the antennas can be closer to each other, so 5G antennas are not judged by number, but an array.

Currently, mainstream equipment manufacturers including ZTE, Huawei, Datang Mobile, Ericsson and Nokia have all launched Massive MIMO products and solutions. Due to the inherent differences between TDD and FDD standards in channel information acquisition, TDD-based array antennas are progressing faster at this stage.

The second is beamforming, which is also used in WiFi routers. In the 5G era, large-scale antenna technology is the basic condition for beamforming.

In the absence of human interference, electromagnetic waves propagate 360 ​​degrees without blind spots, and a large part of them are not received and wasted. Antenna arrays can make electromagnetic waves propagate in a manually specified direction, and the more antennas there are, the more concentrated the propagation direction of the electromagnetic waves.

Beamforming can direct wireless signals to the direction where they are needed, and it also requires beam steering technology to continuously adjust according to changes in the position of the signal receiving point, which requires high technical content.

Back to the question at the beginning of the article, why did Ren Zhengfei emphasize that "only Huawei has done a good job in combining 5G base stations and microwaves"? This was mainly for the United States and some European countries to hear.

Microwave base station backhaul antenna (from Comba Telecom official website)

5G base stations are deployed at a high frequency, so the base station density is greater. If each base station is connected to the central computer room by optical fiber, the cost will increase significantly and it will also be very complicated, especially in the United States and parts of Europe. The optical fiber coverage in these areas is far less than that in China. Using microwave technology for backhaul is an economically feasible and suitable solution.

A typical use case of millimeter wave systems is self-backhaul, where a 5G air interface provides multiple access and transmission through one or more hops without the need for optical fiber links.

Recently, Qualcomm also released its Qualcomm QTM052 millimeter wave antenna module for millimeter waves, which includes everything from transceivers to all RF front-end devices, as well as power management ICs and antennas. Qualcomm said that depending on the different requirements for mobile phone performance, 3 to 4 of these modules can be installed in a mobile phone. The spectrum covered by this module is also a relatively mainstream millimeter wave frequency band.

The RF link architecture below 6GHz is completely different from that of millimeter wave, and Qualcomm has also launched corresponding products for each. This also means that in the early stages of 5G commercial use, mobile phones in different countries or regions may be equipped with different RF units, and the supported frequencies may also be slightly different. The first batch of 5G mobile phones will not have the "roaming" function, and full-mode mobile phones will be implemented in subsequent products.

The more mainstream frequency bands of millimeter waves are 28 GHz and 39 GHz. Each country and region will deploy millimeter waves and spectrum below 6 GHz based on historical conditions and spectrum resources. For example, North America may first deploy 5G in the millimeter wave band, China will first deploy 5G below 6 GHz, and Japan and South Korea may deploy both frequency bands.

Leifeng.com learned that the three major domestic operators may not commercialize 5G millimeter wave frequency bands until 2022, which is also related to the historical development of my country's communications. As early as 2013, the State Council issued the "Notice on the Implementation of the "Broadband China" Strategy and Implementation Plan". The "optical fiber in, copper out" and speed-up and fee reduction policies have allowed high-speed optical fiber to enter ordinary people's homes. The backbone network resources of operators are also very rich. Therefore, domestic operators did not have a particularly strong desire to use millimeter waves for backhaul in the early stage of 5G commercialization, but turned to further explore other applications of 5G in mature stages. Operators in Europe and the United States are businessmen and will not do business at a loss. The cost of laying optical fiber is high and the coverage density is still low. Europe and the United States have been moving towards millimeter waves earlier.

Leifeng.com found that the National Radio Management Work Points for 2019 released by the Radio Administration Bureau of China in February this year pointed out that the frequency use plan for some millimeter wave bands of 5G systems will be released in due course to guide the development of the millimeter wave industry of 5G systems. Earlier, the Ministry of Industry and Information Technology also approved the use of 4.8-5.0GHz, 24.75-27.5 GHz and 37-42.5GHz frequency bands for my country's 5G technology research and development tests, and the test sites are the MTNet laboratory of the China Academy of Information and Communications Technology and the 5G technology test field in Huairou and Shunyi, Beijing.

In the domestic market, Sub-6GHz is the key for operators to deploy NSA (non-standalone) 5G networks. It not only saves network construction costs, but also takes into account network coverage and internal penetration capabilities of buildings. It is a more mature choice for the domestic market. Industry insiders said that commercial millimeter waves will not affect the competitiveness of domestic 5G in 2022.

Different countries and regions will use different frequencies to carry 5G in 2019

China, Europe, Japan, South Korea, Australia and other places are among the most popular countries and regions for using the sub-6GHz frequency band for the first wave of 5G mobile phones. The domestic demand for millimeter waves is not as high as in some foreign regions.

Industry insiders predict that the development of millimeter wave in China may be very late, but compared with the high cost of renting optical fiber, millimeter wave still has certain advantages. In China, it is difficult for millimeter wave to replace optical fiber for backhaul, but in foreign countries, some operators may choose millimeter wave for base station backhaul.

Some people believe that perfect 5G requires the widespread application of millimeter wave frequency bands in 5G access systems. Millimeter waves will bring 5G closer to its original concept. Related technologies are also constantly evolving. Perhaps in the near future, millimeter waves will become a commonly used frequency band for 5G and even 6G.

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