Advantages of mmWave

Source： Communication world

The frequency bands used by 5G are divided into Sub 6GHz and mmWave. In the Sub 6GHz, ultra-high-speed, high-capacity communications have not been significantly improved, and these characteristics are in line with the characteristics of the mmWave band. Today, 5G construction is in full swing, and mmWave have naturally attracted the attention of the industry.

According to data in August 2020, 22 operators have deployed mmWave 5G systems globally, and the United States, Japan and South Korea have focused on deploying commercial networks in the 28GHz frequency band. At the same time, the United States is still considering the commercialization of the 26GHz frequency band. Generally speaking, the mmWave industry is not yet mature, and for operators and equipment manufacturers, opportunities and challenges accompany each other. In order to explore the progress of the mmWave industry, solve the challenges encountered in the mmWave development process, and look forward to the future of the mmWave industry, a reporter from Communications World Media interviewed Zhang Li, a senior researcher at the Institute of Wireless and Terminal Technology, China Mobile Research Institute.

Compared with frequency bands below 6 GHz, mmWave have the advantages of rich spectrum and low time delay. Zhang Li said that first, the mmWave spectrum resources are rich, the carrier bandwidth can reach 400MHz/800MHz, and the wireless transmission rate can reach more than 10Gbit/s; second, the mmWave beam is narrow, has good directivity, and has high spatial resolution. ; Third, the mmWave wavelength is short, the antenna size is small, and the miniaturization and light weight of the large-scale array are easier to realize; fourth, the mmWave sub-carrier spacing is large, and the single SLOT period (120kHz) is low-frequency Sub-6G (30kHz) 1/4, the air interface delay is reduced, which can meet the needs of the industry; fifth, the mmWave indoor and outdoor isolation is good, which is more conducive to eliminating indoor and outdoor interference when using different frame structures indoors and outdoors.

The biggest feature of mmWave is large bandwidth. In Zhang Li's view, mmWave can provide a higher user experience rate compared to the Sub 6GHz, which can meet the business needs of large-capacity concurrent public network and industry users, and further enhance 5G network capabilities. Considering the large loss of mmWave frequency band, poor penetration and diffraction ability, easy to be affected by the external environment, and limited coverage distance, it is suitable for areas with rich reflection paths and less open space. It is generally used for the supplement of the capacity layer and hot spot coverage. And fixed wireless access and many other scenarios, such as public network indoor high-capacity hotspot scenes, such as airports, railway stations, large commercial districts, etc.; public network outdoor high-capacity hotspot coverage, such as squares where large gatherings can be held, sports Stadiums, core arterial roads, etc.; industry online/downlink high-traffic, low-latency requirements, such as industrial Internet, high-speed rail sites, media, medical, etc.; fixed wireless access FWA scenarios to solve wireless broadband services for single-family or multi-storey apartment shops Wait. In addition, there are other application scenarios to be further explored.

"But we still need to see that the mmWave frequency band has large propagation loss and weak coverage, so continuous coverage is difficult and application scenarios are limited." Zhang Li emphasized that this will cause mmWave network construction to have higher technical requirements for base station products , In the absence of scale, the cost of equipment and overall network construction is high. At the same time, high-frequency devices have lower power consumption efficiency than devices in the Sub 6GHz, which will result in lower power efficiency of the whole machine. Overall, both the mmWave networking solutions of operators and the cost control of equipment manufacturers will face greater challenges.

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