At that time, everyone was concerned about Ren Zhengfei's answer to other questions, but no one clearly stated what "microwave" is. Can't help wondering, is microwave a flaw?
Microwave is a very broad definition. It can refer to electromagnetic waves with a frequency of 300MHz~300GHz, and the corresponding wavelength is between 1mm and 1m. The microwave mentioned here is mainly referred to as millimeter wave.
The reason why the millimeter wave in the 5G era is suddenly favored: the bandwidth is large
Communication is the process of code decoding, modulation and demodulation, encryption and decryption. The electromagnetic wave is the one that carries all kinds of information. The electromagnetic wave is also the foundation of wireless communication. Globally, there are only two types of frequency bands deployed in 5G, one is sub-6GHz, which refers to the frequency band below 6GHz, and the other is millimeter wave.
As the name implies, the millimeter wave is an electromagnetic wave with a wavelength of 1 to 10 mm, and the corresponding frequency is 30 to 300 GHz. As a reference, the frequency band used by our current 4G is 2000 MHz, and 2G and 3G are even lower.
Whether it is 2G/3G or 4G era, millimeter wave has always been there, its history can be traced back to the 1890s, but for a long time, millimeter waves are only active in the university's laboratory, just theory explore.
To this day, the main applications of millimeter waves are satellite communications, radar and some military applications, such as early applications in radio astronomy, 77 GHz car anti-collision radar, etc., but in the 5G era, millimeter waves finally have to "turn over the serf and sing" .
Excerpt from Baidu Encyclopedia
The reason why 5G uses millimeter wave is simple and pure. There are abundant spectrum resources above 30 GHz. According to the conversion relationship, 1 GHz=1000 MHz, 1 MHz=1000 kHz, the spectrum resources of millimeter waves are an order of magnitude improvement.
In the past, the reason whyDevelopmentThere are two main reasons for millimeter waves. One is that commercial demand is not large, and the other is that the overall industry chain technology is immature and the cost of use is high.
The arrival of 5G accelerates this process, and makes millimeter wave an "optimal solution". The large bandwidth required for 5G is more than 100M, and operators have continuous 100M bandwidth is the basic requirement for 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 3MHz from 3500MHz to 3600MHz;China MobileObtain 5G test frequency resources in the frequency band of 2515MHz-2675MHz and 4800MHz-4900MHz.
It can be seen that China's three major operators have at least 100M continuous bandwidth resources to carry out 5G. In contrast, the spectrum resources of the three major operators in the 4G era are not continuous, and the bandwidth resources are less than 100M.
From 4G to 5G, another explosion of data, it requires faster transmission speed. Generally, there are two methods for increasing the wireless transmission rate. One is to increase the spectrum utilization, and the other is to increase the spectrum bandwidth. The spectrum bandwidth is simple and straightforward, and only sufficient bandwidth resources are required.
The maximum signal bandwidth of wireless communication is about 5% of the carrier frequency. The 4G network is in the sub 6GHz band. The maximum available bandwidth is 100MHz, and the data transmission rate does not exceed 1Gbps. In the millimeter wave band, the available bandwidth is greatly increased, and the data transmission rate is also multiplied. In addition to the improvement of new materials, new technologies and new processes, millimeter waves are finally coming to large-scale applications in the 5G era.
Solve the shortcomings of millimeter wave - Massive MIMO and beamforming
If the millimeter wave is an advantage, it will not be treated so much until now. The millimeter wave belongs to the category of "very high frequency". The transmission of electromagnetic wave is characterized by the higher the frequency, the shorter the wavelength, the weaker the diffraction ability, and the stronger the penetration ability. Signal penetration will lose a lot of energy, so the transmission distance will be closer. In short, the higher the frequency, the closer the electromagnetic wave travels.
More than this, compared with the lower frequency electromagnetic waves, the millimeter wave signal encounters a large attenuation of water, which seriously affects the propagation effect. Studies have shown that under normal circumstances, the greater the instantaneous intensity of rainfall, the farther the distance, the larger the raindrops, the more severe the millimeter wave attenuation. Therefore, in the millimeter wave communication system or communication line design, it is necessary to leave enough level attenuation. the amount.
In order to solve the problem of millimeter wave transmission distance, 5G has several key technologies born or enhanced. The first one is Massive MIMO, which is referred to as large-scale antenna technology. The meaning of MIMO is the “Multiple-Input Multiple-Output”. As shown in the following figure, MIMO technology in 4G era has been applied, but at most It is the 8 antenna of the base station and the 4 antennas of the mobile phone. If more antennas are to be placed at the frequency of the 4G, they will interfere with each other, but it will not be worth the loss.
In the ideal propagation model, when the transmit power at the transmitting end is fixed, the received power at the receiving end is proportional to the square of the wavelength, the transmit antenna gain, and the receive antenna gain, and inversely proportional to the square of the distance between the transmit antenna and the receive antenna.
The millimeter wave band has a high wavelength 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 (the mobile user may change the position at any time), the transmitting antenna and the receiving The gain of the antenna can't be increased too much, so the solution is only - increase the number of transmit and receive antennas, and the millimeter wave wavelength is short and the interference distance between each other is small, the antennas can be closer together, so the 5G antenna is not A number of heroes, but an array.
Currently mainstream equipment vendors include ZTE,HuaweiMassive MIMO products and solutions have been launched by Datang Mobile, Ericsson and Nokia. Due to the inherent differences in channel information acquisition between TDD and FDD, TDD-based array antennas are progressing faster.
The second is Beamforming, which is also used in WiFi routers. The large-scale antenna technology in the 5G era is the basic condition for beamforming.
Under the condition of no human interference, the electromagnetic wave is 360 degrees without dead angle propagation, a large part of which is not received, wasted, the antenna array can make the electromagnetic wave propagate toward the artificial direction, and the more the number of antennas, the electromagnetic wave propagation The more concentrated the direction.
Beamforming can make the wireless signal directional transmission to the direction that needs to be used, and also needs beam steering technology to continuously adjust according to the position change of the signal receiving point, and the technical content is high.
Why is China's millimeter wave deployment later than Europe and America?
Back to the question at the beginning of the article, why did Ren Zhengfei emphasize that "only Huawei is doing a good combination of 5G base stations and microwaves?" The main thing is to listen to the United States and some European countries.
Microwave base station return antenna (extracted from Jingxin Communication official website)
The 5G base station is deployed at a high frequency, so the base station is denser. If each base station is connected to the central computer room by fiber, the cost will be greatly increased, and it will be very complicated. Especially in parts of the United States and Europe, the fiber coverage in these areas is far less than domestic. The use of microwave technology for backhaul is an economically viable alternative.
A typical usage scenario for a millimeter-wave system is self-backhaul. A 5G air interface provides multiple access and transmission through one or more hops without the need for a fiber link.
Recently, Qualcomm also released its Qualcomm QTM052 millimeter wave antenna module for millimeter wave, including transceivers to all RF front-end devices, as well as power management ICs and antennas. According to Qualcomm, according to different requirements for mobile phone performance, Install 3 to 4 modules in a mobile phone. The spectrum covered by the module is also the mainstream millimeter wave band.
The RF link architecture below 6 GHz and the millimeter-wave RF link architecture are completely different. Qualcomm also introduced corresponding products separately, which means that in the early 5G commercial, the RF units of mobile phones in different countries or regions may be different. The frequency of support may also be slightly different. The first batch of 5G mobile phones will not have the "roaming" function, and the full-mode mobile phone will be implemented in the subsequent products.
The mainstream frequency bands of millimeter wave are 28GHz and 39GHz. Each country and region will deploy millimeter wave and spectrum below 6GHz according to historical conditions and spectrum resources. For example, North America may first deploy 5G in the millimeter wave band. 5G deployment under 6GHz, Japan and South Korea may deploy in both bands.
The three major domestic operators will not be able to commercialize the 5G millimeter wave band in 2022, which is also related to the historical development of China's communications. As early as 2013, the State Council issued the "Notice on Implementing the "Broadband China" Strategy and Implementation Plan", "Light into the Copper Retreat" and the policy of speeding up the fee reduction and other high-speed fiber to enter the homes of ordinary people, the backbone of the operators. The network resources are also very rich, so domestic operators in the early stage of 5G commercialization did not have a particularly strong willingness to use the millimeter wave as a backhaul, but instead explored other applications of 5G in the mature stage. Operators in Europe and the United States are not doing business in the business, the cost of fiber laying is high, and the coverage density is still low. The European and American regions have been marching toward the millimeter wave earlier.
The 2019 National Radio Management Tasks issued by the China Radio Administration in February this year pointed out that the frequency utilization plan for some millimeter-wave bands of the 5G system will be released in time to guide the development of the 5G system millimeter wave industry. Earlier, the Ministry of Industry and Information Technology also approved the 4.8-5.0 GHz, 24.75-27.5 GHz and 37-42.5 GHz frequency bands for China's 5G technology R&D test. The test site was the MTNet test room of China Telecom 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-independent networking) 5G networks, which not only saves network construction costs, but also balances network coverage and building penetration capabilities, which is even more for the domestic market. Mature choices, industry insiders said that the commercial millimeter wave in 2022 will not affect the competitiveness of domestic 5G.
Different countries and regions use different frequencies for carrying 5G in 2019.
China, Europe, Japan, South Korea, Australia and other places are using the frequency band below 6GHz to make the first wave of 5G mobile phones more popular countries and regions. Domestically, there is not such a high demand for millimeter waves in some foreign countries.
The industry expects that the development of millimeter wave in China may be very late, but compared with the high cost of renting fiber, the millimeter wave still has certain advantages. It is difficult to replace the fiber in the domestic millimeter wave to do the return, but the operator outside the country. It is possible to select the millimeter wave to do the base station backhaul.
Some people believe that the perfect 5G needs the universal application of the millimeter wave band in the 5G access system. The millimeter wave will make 5G close to its original idea, and related technologies are also evolving. Perhaps in the near future, the millimeter wave will become Common frequency bands of 5G or even 6G.