The mature application of 5G technology and the rapid development of 5G base station construction have brought earth-shattering new changes to people's production and life. Ultra-high-definition video transmission, intelligent driverless cars, the rapid development of the Internet of Things, and so on. It is believed that the development of 5G will also bring more new technological experiences to people.

       However, due to the differences between 5G technology and 4G technology, more 5G base stations need to be set up under the same coverage area. This, in turn, means that more optical cables need to be laid for the connections between these 5G base stations. But there might also be more places that are not suitable for using wired optical cables for the connections. Using wireless microwaves for the signal transmission back to the 5G base stations has become a necessary measure.

       Microwave backhaul cannot replace optical fiber as the mainstream backhaul method, but it does provide a low-cost and effective means for the rapid deployment of 5G networks and broadband networks. The commercialization of 5G is not merely an upgrade of 4G bandwidth; rather, it will give rise to more innovative business models. At that time, the new business models may place greater demands on microwave backhaul.

       In December 2016, the village of Atelier in Zhailumo Township, Zhaogu County, Liangshan Yi Autonomous Prefecture, Sichuan Province, was connected to "100M fiber-optic broadband". In recent years, China has led the world in the speed of its information infrastructure construction. It is quite common for fiber-optic or 4G networks to be launched in remote villages. However, this village with only about 70 households is not just remote; it also has a much harsher environment, as shown in the following picture:

       This is the route that students must take every day to go to and from school. It leads from the village to the outside world and requires climbing a nearly vertical staircase on an 800-meter drop cliff. Therefore, this village has another name - "Cliff Village". To quickly build an "information staircase" for the 70 households in the Cliff Village to communicate with the outside world, re-laying optical fibers was a difficult and costly project. Huawei and China Telecom finally chose the microwave backhaul method and completed the installation of 100-megabit broadband for every household in the Cliff Village within just a few days.

       Whether it is broadband or mobile communication, the user terminal data needs to be transmitted to the server or core network. This process involves backhaul. Especially in mobile communication, the connection between mobile phones and base stations, as well as between base stations and between base stations and servers, require the establishment of dedicated backhaul channels. This process can be achieved through wired optical fibers or wireless backhaul. Among them, microwave backhaul is a major method of wireless backhaul.

       Although fiber backhaul is more reliable than wireless and the cost of fiber is currently not high, when we need to deploy fiber over a vast area of land, this infrastructure requires a large amount of human resources. Moreover, some areas have harsh environments, which significantly increases the cost of fiber deployment. Additionally, fiber deployment requires occupying land resources, and ensuring the protection of underground fiber lines. In many countries overseas, the private nature of land resources leads to high transaction costs for renting land for fiber deployment. Therefore, using wireless methods like microwaves for backhaul is very effective. For example, the microwave backhaul in the cliff village has solved the challenges brought by the harsh environment.

       The microwave transmission method has certain drawbacks. The main issue is that it is limited to line-of-sight transmission. Moreover, when there is too much moisture or dust in the air, the quality of the microwave signal will deteriorate. However, this does not affect the fact that microwave backhaul has already occupied more than half of the backhaul market overseas.

       It can be seen that microwave backhaul has become the mainstream backhaul method in the 4G era, and this method will continue to be used in the 5G era as well. However, the inherent characteristics of 5G pose challenges to microwave backhaul, such as increased bandwidth, scarcity of public frequency bands, and strict network experience requirements. Previously, global microwave backhaul mainly used the 6-42GHz frequency band, with an average backhaul capacity ranging from 50Mbps to 500Mbps. Clearly, this was unable to meet the backhaul capacity requirements of 5G base stations. Therefore, the E band came into play, namely the 70GHz-80GHz frequency band.

       The E-band indeed provides strong support for 5G backhaul. In May 2019, Deutsche Telekom and Ericsson jointly achieved a 100Gbps backhaul rate over a 1.5-kilometer E-band microwave link, which is 10 times the current commercial microwave backhaul rate and can meet the requirements of 5G backhaul.

       According to the research report released by Dell’Oro, Huawei holds the largest share in the microwave transmission market. It obtained a 29% share in the fourth quarter of 2019. Previously, Ren Zhengfei, when interviewed by the media, had mentioned, "There aren't many manufacturers in the world that can produce microwaves. Huawei has reached the most advanced level." This might be the main reason why Huawei can lead the microwave transmission market.

       As mentioned earlier, in most overseas countries, especially developed ones, on the one hand, the labor costs are high, and on the other hand, land is privately owned, making the large-scale deployment of optical fibers very difficult. Therefore, the proportion of microwave backhaul is very high. However, in China, the labor costs are relatively low and the land is publicly owned, so the difficulty of optical fiber deployment has been greatly reduced, resulting in large-scale fiber laying. Does microwave backhaul have no scenarios in China? Undoubtedly, due to the extremely complete optical fiber infrastructure, microwave backhaul in China will never reach a situation where it is evenly matched with optical fibers like in overseas regions. However, it can still serve as an important supplement to optical fibers and has certain application scenarios.

（1）The role of wireless backhaul in universal telecommunications services

       Universal service, as the ultimate goal of the global information and communication industry development, has been implemented to the best extent in China.

       According to public information, the pilot program for universal telecommunications service was initiated by the Ministry of Industry and Information Technology and the Ministry of Finance at the end of 2015. The first three batches of pilot projects have led to a cumulative investment of over 40 billion yuan by central government funds in the investment of basic telecommunications enterprises, supporting and promoting the access of fiber optic networks to 130,000 administrative villages, including 43,000 impoverished villages. This pilot program has significantly improved the broadband network coverage level in rural and remote areas of our country.

       In June 2018, a new round of universal telecommunications service was fully launched. As an "upgraded version" of the universal telecommunications service, the Ministry of Industry and Information Technology officially approved and determined to support 123 cities to implement the construction of 4G base stations in rural areas, meeting the 4G network coverage requirements for 12,000 administrative villages, support 23 cities to implement the construction of 4G base stations in border areas, and support the city of Sansha in Hainan Province to implement the construction of 4G base stations on islands, among other decisions.

       Based on the basic availability of optical fiber networks, the Ministry of Industry and Information Technology and the Ministry of Finance continue to deepen the pilot program for universal telecommunications services, supporting the coverage of 4G networks in rural and remote areas. They aim to achieve a 4G network coverage rate of over 98% for administrative villages by 2020.

       The 4G coverage in administrative villages exceeds 98%, which is an impossible task for other countries around the world. While achieving 4G coverage, most areas have also achieved fiber-optic coverage. However, for harsh environments like the "cliff village" mentioned at the beginning of this article, microwave backhaul is the best way to quickly and cost-effectively achieve the goal of universal telecommunications service.

       With the development of 5G, universal service will eventually extend to areas covered by 5G. Perhaps at that time, microwave backhaul will once again play its role, delivering 5G services to a large number of remote and sparsely populated areas.

（2）Microwave backhaul in industry services

       5G is empowering various industries. In many industry application scenarios, especially in areas where fiber infrastructure is not yet complete, microwave backhaul can quickly and cost-effectively build a 5G network environment for industry customers, without the need to wait for fiber installation. For example, in some video backhaul scenarios, including public security monitoring, power transmission and distribution monitoring, and oil and gas production monitoring, if they are in remote areas, microwave can be directly used for backhaul.

       Take Huawei's AirFlash 5G enterprise microwave solution as an example. It has been implemented in sectors such as security, metro, power, and oil fields. In Zhoukou, Henan Province, through point-to-multipoint microwave access to video sites, the rapid launch and activation of the safe city video system was achieved; in Shenzhen Metro, the on-board 5G wireless monitoring video was uploaded quickly through microwave, providing support for intelligent inspection and customer service; in the Qinling ultra-high voltage transmission monitoring application, the microwave solution was used to provide visual information transmission back to the monitoring system for the unmanned area.