In a broad sense, "base station" refers to the Base Station Subsystem (BSS), which includes the Base Transceiver Station (BTS) and the Base Station Controller (BSC), such as the BTS/BSC combination in a GSM system or the NodeB/RNC architecture in WCDMA. In a narrow sense, it refers to transceiver equipment with specific radio coverage capabilities. Its installation must follow legal procedures: operators must submit an approval form and obtain a site selection certificate; after construction, they must pass environmental testing to obtain an electromagnetic radiation compliance certificate; and finally, apply for a radio station license. According to the "Radio Management Regulations of the People's Republic of China" and the "Telecommunications Regulations of the People's Republic of China," base stations have the legal right to be established, and obstruction or damage is prohibited. The open-source project OpenBTS implements a software-based GSM protocol stack, supporting mobile phones to access communication systems without relying on traditional telecommunications facilities.
A base station is the basic unit that makes up a cellular cell in mobile communications, performing communication and management functions between the mobile communication network and mobile users. In a broad sense, a base station is short for Base Station Subsystem (BSS). Taking a GSM network as an example, it includes a Base Transceiver Station (BTS) and a Base Station Controller (BSC). One BSC can control dozens of BTSs. In systems like WCDMA, similar concepts are called NodeB and RNC. In a narrow sense, a base station, i.e., a public mobile communication base station, is a form of radio station, referring to a radio transceiver station that transmits information between a mobile communication switching center and a mobile phone terminal within a certain radio coverage area. OpenBTS is an open-source base station based on software, providing a standard GSM-compatible mobile phone interface that does not require the use of existing telephone provider interfaces to dial existing telephone systems. OpenBTS is known for being the first industry-standard GSM protocol stack based on open-source software.
What is a 5G communication base station? Someone once compared it to a giant router!
Professor Peng Mugen of Beijing University of Posts and Telecommunications: For example, when we use a wireless local area network, whether it's Wi-Fi on a mobile phone or Wi-Fi on a laptop, to access the network, there is a Wi-Fi node. The device on the network side facing the user is called an access node, or a base station in mobile communication.
So, do base stations emit radiation?
Radiation is divided into electromagnetic radiation and ionizing radiation, and 5G base stations emit electromagnetic radiation. Our 5G base station radiation control is extremely strict—less than 1/5 of the national standard! According to the national standard "Limits for Electromagnetic Environment Control" (GB8702-2014), the electromagnetic radiation of communication base stations must be less than 40 microwatts per square centimeter. In actual implementation, operators consider signal superposition and control the radiation to within 8 microwatts per square centimeter during construction.
According to the Ministry of Industry and Information Technology, as of now, my country has opened over 4.25 million 5G base stations (of which China Mobile has opened over 2.4 million), ranking first globally in number and second globally in total computing power. In addition, the total number of 4G base stations in my country has reached over 5 million. So, is there a relationship between network speed improvement and base station radiation levels? The conclusion is: the more communication base stations there are, the better the mobile phone call quality, and the less electromagnetic radiation generated between the mobile phone and the base station. "It's like air conditioning in a classroom: the more air conditioners installed, the less energy each unit needs to work hard to cool, thus saving electricity!" In fact, we live in an environment of electromagnetic radiation every day because the Earth itself is a large magnetic field, and natural phenomena such as lightning, thunder, and sunspot activity all generate electromagnetic radiation. In daily life, household appliances such as radios, base station antennas, microwave ovens, induction cookers, computers, televisions, hair dryers, and radios also generate electromagnetic radiation, so there's no need to worry too much! "5G construction is no longer proceeding at breakneck speed, but low-frequency base stations have unexpectedly taken the lead—in China Mobile's latest procurement of 400,000 base stations, 700MHz base stations accounted for nearly 40%, a record high! Huawei and ZTE firmly hold the top two positions, while Ericsson and Nokia Bell Labs have seen a reversal in their rankings in the low-frequency bands, reflecting the most brutal competitive logic of the second half of 5G: coverage capability determines survival."
China Mobile has just announced the results of its most significant 5G equipment order for 2025. The order for approximately 397,500 5G base stations was split among five equipment vendors: Huawei, ZTE, Nokia Bell Shanghai, CITIC Mobile, and Ericsson. This competition saw no upsets, only a complete reshuffling of the rankings. Unlike previous years, China Mobile adopted an "invited competitive negotiation" model, directly securing contracts with the five leading suppliers. Of the total procurement, 241,800 stations are in the 2.6GHz/4.9GHz bands, primarily targeting high-traffic urban areas; while 700MHz band base stations account for a substantial 155,700 stations, or 39.1%, almost half of the total. This proportion far exceeds the 21.9% (105,000 stations) of 700MHz procurement in 2024, and is nearly seven times the size of the 23,100 stations procured in 2023.
Scale contraction but significant structural change – this is the most prominent signal of this centralized procurement. Compared to the total of 480,000 base stations in 2024, the scale of 397,500 base stations this time represents a 17% reduction; while China Mobile's 5G capital expenditure has plummeted from 69 billion yuan in 2024 to 58.2 billion yuan, a decrease of 15.7%. The "golden expansion period" of 5G infrastructure is receding, but low-frequency base stations are rising against the trend, becoming the "ballast" for operators to fill coverage gaps. Why is 700MHz suddenly so popular? The answer lies in the laws of physics. Low-frequency electromagnetic waves have strong penetrating power and a large coverage radius; a single base station can cover an area several times that of a high-frequency base station. In mountainous areas, rural areas, underground parking garages, and other scenarios, it can eliminate signal dead zones at a lower cost.
China's 5G RedCap technology deployment has entered the stage of large-scale commercial use. The four major operators are accelerating the construction of RedCap networks. As of the second quarter of 2025, more than 1 million RedCap base stations have been activated nationwide, covering more than 330 cities. The Ministry of Industry and Information Technology (MIIT) policy clearly requires that by the end of 2025, all cities at the county level and above nationwide achieve continuous RedCap coverage, with tens of millions of connections and more than 100 terminal products. In terms of special environment applications, China Mobile has deployed 5G-A base stations supporting RedCap functionality on Mount Everest, with measured uplink capacity of over 200 Mbps in a single cell, meeting the needs of real-time data transmission for scientific expeditions and high-definition live streaming. In industry applications, RedCap has been widely used in power, industrial, and video surveillance scenarios, effectively solving the bottleneck problem of large-scale 5G IoT applications by reducing terminal costs by more than 60%. In the future, with the evolution of the R18 standard and further reductions in chip module costs, RedCap is expected to achieve over 100 million connections by 2026, becoming a mainstream technology for medium- and high-speed 5G IoT.
The deployment of 5G RedCap base stations in China is developing rapidly, with all four major operators actively promoting RedCap network deployment. As of the second quarter of 2025, China Mobile had deployed over 600,000 RedCap base stations, covering all county-level and above areas nationwide in the n28 band (700MHz), and deploying the n41/n79 bands as needed. China Mobile Tibet Company launched its first 5G-A base station on Mount Everest, which also supports RedCap functionality, providing stronger network support for the Everest scenic area. Since March 2024, China Telecom and China Unicom have completed the world's first full-band, full-standard, and full-scenario 5G lightweight (RedCap) commercial verification in five provinces (municipalities): Zhejiang, Guizhou, Guangdong, Henan, and Shanghai. Currently, they have achieved continuous 5G RedCap coverage in 17 provinces nationwide. In April 2024, Guangdong Telecom and Unicom completed the RedCap functionality activation of 120,000 stations across Guangdong Province in the 3.5GHz + 2.1GHz bands, forming a large-bandwidth 5G RedCap network with wide-area continuous coverage and deep indoor coverage. Leveraging the advantages of the 700MHz golden frequency band, China Broadcasting Network actively participates in the development of RedCap technology. It has completed the first batch of 5G RedCap new emergency broadcast terminal technology pilot projects and completed the first high-reliability 5G RedCap emergency broadcast test in China in March 2025.
From a technological evolution perspective, RedCap is the most attention-grabbing innovation in the IoT field in 5G Release 17, introducing medium-to-high-speed IoT capabilities into a single 5G network. By tailoring 5G terminal capabilities (such as reducing bandwidth, decreasing the number of antennas, and simplifying MIMO layers), it effectively reduces terminal complexity, cost, and power consumption, while retaining the low latency, high reliability, and high bandwidth characteristics of the 5G network. This "lightweight 5G" technology fills the gap between traditional 4G IoT (such as Cat.1/Cat.4) and full-featured 5G terminals, providing a superior solution for medium-to-high-speed IoT scenarios. As of the second quarter of 2025, the price of RedCap modules has dropped below 200 yuan, and with large-scale commercial use, it is expected to further decrease to below 100 yuan by the end of 2025, approaching the cost level of 4G Cat.4 modules.
