So far, more than 45 OEMs around the world have announced or will announce the launch of 5g terminals, more than 50 operators have deployed 5g commercial networks, and more than 345 operators are investing in 5g

5g is widely recognized worldwide as a general enabling technology in the industrial 4.0 era. It will bring revolutionary improvement of user experience and digital transformation of thousands of industries, inject new vitality and stimulate new potential into industries such as digital entertainment, medical treatment, health, energy manufacturing and transportation.

Relevant data show that so far, more than 45 OEMs around the world have announced or will announce the launch of 5g terminals, more than 50 operators have deployed 5g commercial networks, and more than 345 operators are investing in 5g. From the perspective of terminals, the shipment of 5g mobile phones is expected to reach 750 million in 2022, and the number of global 5g connections is expected to increase from 1 billion in 2023 to 2.8 billion in 2025.

     

Figure 1: Global 5g deployment planning outlook

5g millimeter wave industry chain is basically mature

As we all know, the frequency band below 6GHz (FR1) and millimeter wave (FR2) are the core of 5g deployment. Only when the network is deployed with millimeter wave at high frequency, sub-6ghz and LTE at intermediate frequency, 2G and 3G networks at low frequency, and combined with multi carrier aggregation technology, the three indicators of rate, coverage and delay of the whole 5g network can be optimized.

At present, the FR1 band is relatively more crowded. Except China, few countries can allocate more than 100m continuous spectrum to operators below 6GHz; Although the coverage of millimeter wave band is relatively weak, the rich spectrum resources can realize high-speed data transmission and significantly improve the capacity, which is very important to fully release the full potential of 5g performance, capacity and throughput.

According to the 5g millimeter wave technology white paper released by GSMA, 5g millimeter wave is expected to contribute US $565 billion to global GDP by 2035, accounting for 25% of the total contribution of 5g. In the Chinese market, it is expected that by 2034, the economic benefits brought by 5g millimeter wave band will reach about US $104 billion, of which manufacturing, hydropower and other utilities in vertical industries account for 62%, professional services and financial services account for 12%, and information, communication and trade account for 10%.

"However, at present, the commercialization of 5g millimeter wave is still in its infancy, the industrial chain has not fully blossomed, and the application scenario is in a state of 'being raised in a boudoir that people don't know'." Said Si Han, President of GSMA Greater China.

The world radiocommunication Conference (wrc-19) of the International Telecommunication Union (ITU) in 2019 is an important moment in the history of millimeter wave development. The meeting determined that the millimeter wave band between 24GHz and 86ghz will be used for international mobile communication (IMT), of which 24.25-27.5ghz, 37-43.5ghz, 45.5-47ghz, 47.2-48.2ghz and 66-71ghz bands are globally integrated and consistent IMT bands, marking a solid step towards maximizing the best performance and scale effect of 5g millimeter wave in the global industry.

As of June 2020, 79 operators in 17 countries and regions have the frequency license to deploy 5g millimeter wave at 24.25-29.5ghz, and more than 120 operators are actively investing in millimeter wave. In addition to the generally optimistic 28ghz band, the United States is also actively promoting the deployment of 24GHz / 37ghz / 39ghz / 47ghz commercial networks; In Asia, China approved the development of R & D tests in the 5G millimeter wave band of 24.75-27.5GHz and 37-42.5GHz as early as July 2017. Japan, Korea, Thailand, China Hongkong and China Taiwan have also completed some of the distribution and auctions of 26GHz and 28GHz spectrum. The EU will unify the radio spectrum in the 26ghz band in May 2019, so that Member States can set common technical conditions for the use of the band and open it to use. Italy, Finland and Norway have completed the allocation or auction of some spectrum.

Figure 2: 5g millimeter wave 24.25-29.5ghz investment of global operators

Although European and American countries are one step ahead of China in the allocation and use of millimeter wave bands. However, as 5g is an important part of the "new infrastructure" strategy, the pace of 5g millimeter wave construction of the three major domestic operators has also begun to accelerate significantly.

Chi Yongsheng, vice president of China Unicom Research Institute, said that with the development of 5g and the expansion of industrial applications, the communication frequency band is bound to develop in the direction of millimeter wave. Since China Unicom and China Telecom jointly built and shared more than a year ago, by the end of August this year, the two sides have completed the construction of 300000 shared base stations. The overall workload in 2020 has been completed by 93%, and the shared construction coverage has been completed for all prefecture level cities. By the end of this year, the number of shared base stations will reach 380000, and the two operators have saved about 60 billion yuan of investment.

"From the perspective of China Mobile, millimeter wave is expected to have large-scale commercial capacity in 2022. Deploying millimeter wave network based on SA will be an ideal choice for operators. At that time, China Mobile will consider using carrier aggregation and dual connection deployment to cooperate with frequency bands below 6GHz to solve the bottleneck of millimeter wave deployment." Li Nan, deputy director of the Institute of wireless and terminal technology of China Mobile Communications Research Institute, said that the outfield test data showed that when 3deu structure was adopted in the 24.75-27.5ghz band, the test bandwidth supported 100m, 200m, 400m and 800m, the cell peak rate could reach 14.7gbps, and the user delay was 1-1.5ms, which was consistent with the theoretical analysis and effectively improved the confidence in millimeter wave.

From the perspective of equipment and chip manufacturers, at present, mainstream equipment manufacturers support 800m bandwidth. Qualcomm is the earliest. Several generations of commercial millimeter wave antenna module products can support millimeter wave full band. In addition, Samsung exynos 5123, MediaTek Helio M80 and other series chips can also support millimeter wave. In terms of domestic terminals, ZTE, Yijia, oppo, Yiyuan and other manufacturers have launched mobile hotspots, mobile phones, modules and other products supporting millimeter wave respectively. For example, oppo and Ericsson have realized the end-to-end test of 5g millimeter wave commercial system and commercial CPE, the downlink rate of 4.06gbps and the uplink rate of 210mbps. In the pull-out test, the downlink rate of 200Mbps is still maintained at 2.3km.

The soldiers and horses did not move, and the standard went first

In terms of standard maturity, both 3.5GHz adopted by China and 28ghz dominated by the United States are synchronized. For example, many 5g NR enhancement features supporting millimeter wave have been introduced into rel-16 project, including integrated access and return (IAB) technology supporting flexible deployment of small base stations, enhanced beam management, dual connection optimization, positioning technology, etc., in order to focus on enhancing vertical industry applications and improving the overall system performance. Meanwhile, in order to further improve 5g NR millimeter wave energy efficiency, R16 also supports terminal auxiliary power saving, efficient carrier aggregation operation and c-drx (discontinuous reception based on Networking).

In rel-17 and future versions, more features supporting millimeter wave 5g NR enhancement will be introduced, including optimizing IAB to support distributed deployment, so as to help introduce full duplex operation and mobile relay (such as automobile) to improve capacity, coverage and quality of service; Optimized network coverage and beam management to reduce system overhead, enhance performance and improve network coverage; Continue to expand the spectrum range, support the frequency band from 52.6ghz to 71ghz and license free spectrum; Support new scenarios other than embB, and expand millimeter wave support to the fields of direct communication, urllc (ultra-high reliability and low delay communication) and industrial Internet of things; Continuously enhance the positioning technology to achieve centimeter accuracy, lower delay and higher capacity.

   

Figure 3: 3GPP standard schedule

In addition to the physical layer and system design, 3GPP also provides extensive support for millimeter wave in terms of RF standards, including single band standardization for millimeter wave band concerned by operators in R15 stage, further support for carrier aggregation in millimeter wave band in R16 / R17 stage, and cross band carrier aggregation and double link of FR1 and FR2, It can basically meet the current needs of operators for millimeter wave deployment. Subsequently, 3GPP will also consider cross band carrier aggregation between millimeter wave bands to further enrich the combination of millimeter wave working scenarios and bands.

Demand leads three application scenarios

At present, in addition to focusing on creating three application scenarios - hot spot coverage such as indoor and outdoor transportation hubs / venues, industrial Internet and other industrial applications, and wireless bandwidth access to homes / office buildings, China Unicom is taking the scientific and technological Winter Olympics as the time node to accelerate the development of domestic millimeter wave industry chain through millimeter wave pilot verification of Winter Olympics scenarios, It is expected that the deployment of all winter Olympic venues and equipment will be completed in June 2021.

How to better realize the application landing based on the characteristics of 5g millimeter wave? Chi Yongsheng believes that application scenarios should be fully focused. For example, in the case of to C, we should create a brand special zone by providing high-quality services, ensure accurate coverage of hot areas by relying on 5g millimeter wave, and do a good job in the diversion of business volume; In the to a scenario, FWA (fixed wireless access) can be used to meet the needs of home broadband or office broadband; In the to B scenario, millimeter wave can be combined with mec (mobile edge computing) and AI technology to superimpose more value-added services on the characteristics of large bandwidth and high rate, so as to provide exclusive services for industrial Internet based scenarios such as smart plant, park and wharf.

   

Figure 4: measured signal results of stadiums and gymnasiums after 5g millimeter wave deployment and comparison test results of 4G and 5g millimeter wave download rates

"To give full play to the full potential of 5g millimeter wave, we need to accelerate the expansion to more valuable mobile access applications." Li Nan said. The potential application scenarios of 5g millimeter wave in the future, in addition to the 2C applications such as XR (extended reality) social networking, games and HD live broadcasting, which require high speed, can also give play to the technical advantages of 5g millimeter wave super uplink, super downlink data transmission and ultra short delay in 2B industry applications, and expand the application of 5g millimeter wave in vertical industry, To promote the development of millimeter wave.

Because the characteristics of millimeter wave band are different from those of sub-6ghz, the application scenarios are different, and the deployment rhythm is also different. Chen Peng, senior technical expert of China Telecom, said that in terms of 5g millimeter wave network deployment, operators will no longer adopt wide area full coverage above prefecture level cities, but focus on indoor, hot areas and vertical industries as capacity hotspot solutions. For example, when deployed indoors, millimeter wave can complement existing wireless services provided by Wi Fi and expand to new terminal types, bringing superior speed and unlimited capacity while supporting enhanced experience. At the same time, the large bandwidth and more accurate directivity of 5g millimeter wave will also become a potential return scheme in areas where optical fiber resources are scarce.

Four Misunderstandings of 5g millimeter wave

"Tao", "law" and "art" are the image statements given by Wang Jianli, chief engineer of ZTE wireless product planning. The so-called "Tao" refers to the ability to fundamentally solve the poor coverage of millimeter wave; "Method" refers to designing their own array antenna architecture, beam algorithm and reflector technology based on the unique beam characteristics of millimeter wave; "Technology" refers to actively participating in the formulation of 3GPP standards and understanding the technical details.

In fact, as far as millimeter wave itself is concerned, its biggest advantage lies in the rich frequency band resources; Secondly, it has large bandwidth and fast transmission speed. The bandwidth of 400m or even 800m is four times that of 3.5GHz band, the transmission speed can reach 10Gbps, and the air interface delay is small, which provides natural advantages for the development of high reliability and low delay services; Finally, the millimeter wave antenna is small in size, can form a narrower beam, has strong spatial distribution ability, and can make up for the propagation loss and penetration loss caused by too high frequency to a certain extent. Of course, the latter is also the deficiency of millimeter wave technology. In the typical scene of penetrating concrete, the penetration loss is as high as 109dB, which is more than twice that of 2.6GHz and 3.5GHz.

"The key to a new breakthrough in mobile broadband is to realize the mobility of millimeter wave" - this is the core view of Dr. Luo Tao, senior director of engineering and technology of Qualcomm. As mentioned above, the biggest advantage of millimeter wave is that it has rich bandwidth resources. Operators can deploy networks with 800MHz bandwidth. In addition, millimeter wave base stations and mobile phones supporting millimeter wave can use carrier aggregation or beam aggregation to realize data transmission, and support dense spatial multiplexing while reducing interference.

In his view, the initial stage of millimeter wave deployment focused on smart phones, mainly driven by operators, and focused on densely populated urban areas. The latest measurement results of ookla Speedtest show that based on the measurement of the existing network in the frequency band below 6GHz (such as 3.5GHz and 2.6GHz), the 5g download speed is five times faster than 4G LTE. Compared with the frequency band below 6GHz, the measured download speed of 5g millimeter wave terminal is four times faster, with an average rate of 900mbps and a peak rate of more than 2gbps, which means that the audio book of 10 hours can be downloaded in one second, The speed is amazing. At the same time, the high-capacity characteristic of millimeter wave also helps to promote operators to provide unlimited traffic packages, which is a major benefit to consumers.

     

Figure 5: compared with the frequency band below 6GHz, the measured download speed of 5g millimeter wave terminal is 4 times faster

Dr. Xu Ying, R & D director of Qualcomm China, said that there are still four misunderstandings in the current industry and academia, including consumers, about millimeter wave mobility:

Myth 1, "millimeter wave coverage is limited and expensive". He believes that this problem can be solved through two measures: first, combine sub-6ghz with millimeter wave, use the low frequency band of sub-6ghz for 5g coverage nationwide, and use millimeter wave to achieve hot spot coverage in scenes requiring large capacity and high rate; Second, the deployment of millimeter wave networks in key application scenarios, such as Olympic venues, concert halls, shopping malls and transportation hubs, not only has a relatively low cost, but also can achieve a better coverage effect.

Myth 2, "millimeter wave only supports line of sight transmission". In fact, supporting fast channel switching is a key solution for millimeter wave. In other words, if a transmission path is blocked by hands or other parts of the body, you can quickly find a new transmission path by activating another module on the mobile phone. When this conversion is extended from within the base station to between different base stations, the switching of millimeter wave transmission between different base stations can be realized quickly.

Myth 3, "millimeter wave is only used for fixed scenes". In order to verify the performance of millimeter wave modem, Qualcomm experimenters either test the mobile phone in a scene with large traffic and blocked by people, or choose a more extreme test environment, fix the mobile phone equipped with Xiaolong X50 chip on the UAV, and remotely control the UAV to shuttle around the park. Thanks to advanced beam management algorithms, mobile phones can maintain high-speed network connection even in these challenging environments.

     

Figure 6: test the ultimate mobility of 5g through the mobile test terminal fixed on the UAV

Myth 4, "the overall dimension of millimeter wave terminal is large". Taking Qualcomm's first commercial millimeter wave module as an example, it integrates antenna, RF front-end and transceiver in a very compact size. A mobile phone can adopt multiple such millimeter wave modules, which can not only meet the compact and slim design requirements of smart phones, but also meet the power consumption requirements and provide maximum performance.

The scale deployment and commercial operation of 5g millimeter wave system will be an important basis for 5g subsequent evolution and 6G technology research and development. "Only through the large-scale deployment and commercial operation of 5g millimeter wave system can the global mobile communication industry obtain the first-hand experience of high-frequency network deployment and operation, extract further market and technical requirements, and guide the follow-up evolution of 5g and the research and development of 6G technology." Said Yang Guang, senior analyst in the field of wireless communications at strategy analytics.

Avoid "talking on paper"

No matter how advanced communication technology is, if it can not be installed into terminals such as smart phones, it is tantamount to "talking on paper". Zhong Yongwei, senior Wireless Engineer of Yijia mobile phone, and Xie Wanbo, head of the pre research team of Xiaomi mobile phone antenna department, respectively introduced how they installed millimeter wave technology into smart terminals.

Zhong Yongwei said that putting millimeter wave into mobile phones will mainly face the following three challenges: first, the path loss is relatively high and the coverage is limited. In particular, if the mobile phone adopts the traditional antenna form, the coverage will be less than 1 / 8 of 3G, and the connectivity will be greatly damaged; Second, if the traditional antenna and chip separation method is adopted, it will lead to low signal transmission efficiency, serious heating, greater difficulty in manufacturing process and higher production cost of mobile phone; Third, millimeter waves are easily blocked by objects, especially for mobile phones. There are not only buildings, but also hands or human bodies.

"If mobile terminals want to consider the coexistence of sub-6ghz and millimeter wave, they will encounter challenges in Antenna Integration and supporting a wide frequency band." Xie Wanbo frankly said that the first challenge is space. How to integrate millimeter wave and traditional antenna requires a lot of energy and manpower; The second challenge is the user experience. The contradiction between the easy occlusion of millimeter wave and the flexible use of mobile phones requires a lot of effort to try how to give full play to the advantages of millimeter wave; The third challenge is technology. Many things in technology are directly related to user experience. This series of problems need new materials, new processes and new implementation methods. This work requires all parties involved in the industrial chain to tackle key technical problems. "

Research results from academia are also of great benefit. Chen Jixin, professor and doctoral supervisor of School of information science and engineering of Southeast University and director of Department of electromagnetic field and microwave engineering, shared the research situation of millimeter wave multichannel chip. Millimeter wave and terahertz bands are in the transition band from electronics to photonics. They have rich spectrum resources and have high academic and engineering research value in the fields of information, life, national defense, aerospace and so on. Among them, millimeter wave multichannel chip is the core device of 5g and b5g / 6G mobile communication. With the evolution of mobile communication, millimeter wave chip will continue to evolve.

Professor Liu Zhihong of Xi'an University of Electronic Science and technology introduced the technology and current situation of the third generation semiconductor material Gan on Si (silicon based gallium nitride) used in key RF devices of millimeter wave system. In the field of PA, the third generation semiconductor has indisputable advantages in output power and efficiency, and plays a leading role in radar, satellite, wired broadband, base station, RF energy and other fields. In the mobile phone RF device market, the challenge of gallium nitride technology comes from two aspects: first, the thermal resistance is relatively high, and the heat dissipation is relatively poor for high-power or especially high-power amplifiers; Second, the RF loss is high, especially when the frequency is high. In addition, from the perspective of large-size wafer growth and manufacturing, there are also challenges in stress, dislocation density, reliability and CMOS compatible process manufacturing. However, in the long run, with the gradual increase in the number of 5g base stations and the requirements for cost control, Gan will become a good choice.

At present, the market mainly focuses on silicon carbide based gallium nitride products, and mature commercial products mainly come from MACOM in the United States and OMMIC in Europe. However, Intel, TSMC, San'an, innosecco and other domestic and foreign companies are also in the stage of high-speed development. Professor Liu Zhihong believes that if you really expect the mobile phone RF front-end market to accept gallium nitride technology, it is absolutely an unavoidable topic to realize process compatibility with Si CMOS. From the current research results, XD team has been able to design and manufacture 80nm silicon-based GaN HEMT. Although there is still a lot of room to be optimized, it has exceeded the existing gallium arsenide products in terms of power and efficiency, which also represents its potential in the mobile terminal market in the future.