Exploring communication base stations

一、What is a communication base station?

（一）Definition and Basic Principles

Communication base station, also known as public mobile communication base station, is a form of wireless radio station. Simply put, it refers to a radio transceiver station that transmits information between mobile phone terminals through a mobile communication exchange center within a certain radio coverage area.

We use devices such as mobile phones and computers every day to make phone calls, deliver messages, or surf the internet, and this is inseparable from the silent work of communication base stations. A base station covers a certain area through radio, and in this area, it acts as a relay station, responsible for receiving information sent by mobile phone terminals (such as our phones), including voice calls, text messages, or data requests, through antennas. Subsequently, the RF receiver inside the base station begins to function, converting the received wireless signal into a digital signal. Then, the digital signal processor performs a series of processing on these digital signals, such as filtering, demodulation, decoding, and error correction, to ensure the accuracy and reliability of the signal. This process is the signal reception and processing stage.

When the information is to be transmitted, the processed digital signal will be forwarded to the mobile communication core network, which is the core part of the mobile communication system. It is responsible for processing signals from the base station and connecting with other networks (such as the Internet and other operators' networks), so that the information can be accurately sent to the destination. If a base station needs to send information to a mobile device, it will first receive the corresponding digital signals from the core network, then use an RF transmitter to convert these digital signals back to wireless signals, and finally send them back to the mobile device through an antenna, so that we can smoothly receive the information.

A base station is mainly composed of a base station transceiver station (BTS) and a base station controller (BSC). BTS is responsible for the reception and transmission of wireless signals, just like a beacon on a lighthouse indicating direction, while BSC is responsible for controlling and managing base station transceivers, similar to the command system inside a lighthouse, to ensure the normal operation of the communication network. The specific working principles of different types of base stations, such as 2G, 3G, 4G, and 5G base stations, may vary depending on the communication technology standards used, but overall they all revolve around the signal reception, processing, forwarding, and transmission processes mentioned above for information transmission. The purpose is to enable us to maintain signals and freely transmit information anytime, anywhere within their coverage area.

（二）Important position

In China's mobile communication network system, the construction of mobile communication base stations is an important part of investment for mobile communication operators. It can be regarded as the most critical infrastructure in the entire mobile communication network, and its importance is reflected in many aspects.

    From the perspective of coverage, through reasonable layout and effective signal coverage, base stations enable people to use mobile devices such as smartphones to access the network and achieve communication functions, whether in bustling city centers, remote rural areas, mountainous regions, or even sparsely populated border areas. This greatly expands the scope of communication and eliminates geographical limitations.

    In terms of ensuring call quality, the performance, quantity, and layout rationality of base stations directly affect call quality. High quality base station equipment, reasonable site selection, and scientific frequency planning can reduce signal interference, ensure clear and smooth voice calls, and avoid situations that affect user experience such as call interruptions and blurry sound.

    In terms of investment efficiency, although the investment in base station construction is huge, the benefits it brings are also long-term and extensive. It is the foundation for the development of mobile services. With good base station coverage, it can attract more users to use mobile communication services, thereby driving the consumption of services such as voice calls, SMS, and mobile data traffic, creating economic benefits for operators, and promoting the healthy development of the entire communication industry.

    Moreover, the difficulty level of base station construction and the convenience of subsequent maintenance are also related to the stable and efficient operation of the entire mobile communication network. Convenient construction can enable base stations to be put into use faster and expand coverage in a timely manner; And easy maintenance can ensure that the base station is always in good working condition, reducing the communication impact caused by faults.

    With the development of mobile communication network services towards dataization and grouping, the trend of base station development is inevitably towards broadband, large coverage construction, and IP to adapt to the increasing demand for new communication technologies such as high-definition video calls, large data transmission, and the Internet of Things. As of the end of March 2021, China has built 819000 5G base stations, accounting for more than 70% of the world's total. This huge scale of base stations has laid a solid foundation for China to expand and enrich 5G network applications in many industries such as shopping, manufacturing, and healthcare. This also shows the important position of communication base stations in China's communication development and the progress of various industries in society.

二、The Development History of Communication Base Stations

（一）Early forms of base stations (1G to 2G era)

    The development process of communication base stations has witnessed the continuous innovation and evolution of communication technology. Going back to the 1G era, that was the beginning of mobile communication network deployment. In the late 1970s, the full English name for a base station was Base Station, abbreviated as BS, which is still used today. At that time, there were various standards, but the two main mainstream standards were AMPS and TACS. In 1987, China established the first generation of analog mobile communication systems in Qinhuangdao, Hebei and Guangdong, officially opening the prelude to China's mobile communication industry. However, 1G, as an analog system, has obvious drawbacks. It not only has low capacity and limited number of calls that can be supported within the same area, but also has poor call quality, often resulting in unstable signals, unclear sound, and extremely poor confidentiality. Even during base station maintenance, staff may accidentally overhear conversations between users.

    Entering the 2G era, base stations have a new name - Base Transceiver Station, abbreviated as BTS, which stands for Base Transceiver Station. Compared to 1G base stations, the naming BTS more accurately reflects its functional characteristics, as the transceiver is an important component of BTS. Taking Ericsson RBS2206BTS as an example, it mainly includes a common unit, a transmitting and receiving unit, and a combining and splitting unit. The common unit includes a power supply unit, a transmission interface unit, a clock distribution unit, etc. The functions of the transmitting and receiving unit include wireless signal transmission and reception, amplification, modulation/demodulation, encoding and decoding, and DSP digital processing. In fact, it integrates the baseband unit (BBU) and the radio frequency unit (RRU) into one. However, early 2G base stations were bulky and cumbersome, and expansion and operation were quite complicated. Each transmitting and receiving unit could only handle one carrier signal, and one carrier frequency could accommodate up to 8 users at the same time. Once the base station was congested and needed expansion, operation and maintenance engineers had to carry the bulky carrier frequency and shuttle between the rooftop base stations. If congestion continued, they had to expand the cabinets, which was a huge workload. It can be said that base stations in the 2G era are integrated BTS, with baseband processing, RF processing, power supply units, etc. all placed in one cabinet, like a big refrigerator, with high construction and expansion costs, and many inconveniences in operation and maintenance.

（二）Evolution under Technological Change (3G-4G Era)

    With the continuous advancement of communication technology and the arrival of the 3G era, the name of the base station has been changed to NodeB. Compared with the 2G era, the biggest change is the implementation of a separate architecture for BBU and RRU. In 2G BTS, BBU and RRU are integrated, which poses problems such as being large, heavy, and difficult to expand. In the era of 3G data, in order to cope with the constantly increasing demand for data rates, the baseband part needs to introduce technologies such as adaptive modulation and coding, MIMO multi antenna, etc. If the baseband and RF are still not separated, each expansion will require a separate channel from baseband processing, DAC conversion, RF amplifier to feeder, which will inevitably greatly increase construction costs. In this context, software defined radio technology has played a role by integrating the generation, modulation/demodulation, encoding and decoding functions of baseband signals into a "central base station hub" (BBU), and connecting them through the Common Public Radio Interface (CPRI) and Open Base Station Standards Initiative (OBSAI), allowing one BBU to provide a baseband resource pool for multiple RRUs. This modular base station architecture has obvious advantages, not only reducing network construction costs and improving the flexibility of network expansion and upgrading, but also using fiber optic connections between BBU and RRU to avoid high losses caused by traditional feeder long-distance transmission. In addition, the operator originally hoped to release the device lock binding and increase bargaining power to further reduce procurement costs, but this idea was ultimately not fully realized.

    In the 4G era, the name of the base station changed to eNB, which is an evolved Node B, and the biggest feature of the base station during this period was SingleRAN. SingleRAN also relies on software defined radio technology, which is another major change in the field of mobile base stations after the separation of BBU and RRU. It further reduces the complexity and construction cost of base stations. SingleRAN was first launched by Huawei. As early as 2008, Huawei and Vodafone deployed the world's first SingleRAN base station that integrates 2G and 3G. Its strength lies in fully utilizing the flexibility of software and standards, and facing the future integration of 2G/3G/4G, it can provide operators with a smooth transition to 4G at a lower cost. Therefore, it is highly favored by many operators in Latin America such as Am é rica M ó vil, Finland's TeliaSonera, Sweden's Net4 Mobility, Aero2, and has also helped Huawei occupy an important position in the 4G market.

（三）A New Look towards the 5G Era

    Nowadays, we have entered the era of 5G, which supports ultra-high speed, ultra-low latency, and super many connections, making business more diversified. This also puts forward new requirements for base stations. In terms of architecture, 5G base stations have undergone significant changes, with the introduction of Massive MIMO technology (massive multiple input multiple output) and the emergence of new devices such as Active Antenna Processing Units (AAUs) in the base station structure. Because the higher the order of MIMO, the more antennas and feeders are required, resulting in higher process complexity. Therefore, 5G integrates RRU with the original passive antenna to form AAU. The architecture of AAU in the signal transmission link is similar to that of RRU. It has its own responsibilities as BBU, with one responsible for transmitting and receiving wireless RF signals from the client, and the other responsible for processing the information contained in the baseband signal. The two use a pair of optical fibers to complete the transmission and reception of the baseband signal.

    At the same time, 5G adopts a 3-level network architecture, namely DU-CU core network (5GC), where DU and CU together form gNB. Each CU can connect one or more DU, and there are multiple functional segmentation schemes between CUs, which can adapt to different communication scenarios and communication requirements. These new changes in 5G base stations enable them to better meet various new communication needs such as high-definition video calls, large data transmission, and the Internet of Things. They have a symbolic significance in the entire development process of communication, symbolizing that communication technology has reached a new height and laying a solid foundation for the expansion of more communication application scenarios in the future.

三、Common types of communication base stations

（一）Macro base station

    Macro base stations are one of the most common types of base stations, typically installed on tall buildings, mountaintops, or towers. It has a large transmission power, which makes its coverage range relatively wide and can provide wireless communication services with wide area coverage. It is the main pillar of mobile communication networks and can meet the communication needs of a large area.

    For example, in urban areas, macro base stations are widely deployed to provide mobile communication services to a large number of users, support high-speed data transmission and coverage, and meet the huge and dense communication needs of cities; In rural and remote areas, it can compensate for the lack of geographical communication coverage, allowing local residents and businesses to enjoy communication service quality comparable to that of cities; In transportation hubs such as airports, stations and ports, Acer stations can meet the communication needs of a large number of passengers, provide stable communication connections, and support passengers' wireless communication and Internet access; In large sports venues, convention centers, and concert venues, the deployment of macro base stations can meet the instantaneous communication needs of a large number of users, ensuring the stability and reliability of communication services, and avoiding congestion and signal interference; In disaster and emergency rescue situations, even if the communication infrastructure is damaged or interrupted, macro base stations can quickly restore the communication network, provide emergency communication channels for rescue personnel, and assist in the rescue work; In addition, in remote areas and outlying islands where traditional wired communication networks are difficult to cover due to geographical limitations, macro base stations cover these areas wirelessly to provide stable communication services for residents and businesses, promoting economic and social development.

（二）Micro base station

    The transmission power of micro base stations is relatively small, so their coverage range is correspondingly reduced, usually around 50-200 meters. It is often used to fill areas that macro base stations cannot cover, such as installing on commercial buildings, street lamp posts, or outdoor walls.

    In cities, micro base stations are often used in densely populated areas such as high-rise buildings. In areas where macro base station deployment is limited, micro base stations can play a role by providing more stable and high-capacity wireless connections to improve local network quality and increase network capacity, solve signal coverage problems in these areas, and work together with macro base stations to ensure a good communication environment.

（三）Piji Station (Micro Station, Enterprise Small Base Station)

    The size and power of the Piji station are smaller than those of the micro base station, with a coverage range of approximately 20-50 meters. It is mainly used in indoor environments such as shopping malls, office buildings, airports, or subway stations.

    In these densely populated indoor public places with high communication demands, Piji stations can provide partial coverage to solve the communication needs of insufficient indoor signal coverage or high-density user areas, improve indoor signal quality, and enable people to enjoy smooth communication services indoors, meeting various needs such as making phone calls and using the internet.

（四）Fly base station (micro station, home level small base station)

飞基站是最小类型的基站，它的覆盖范围非常有限，通常在 10 - 20 米左右，常用于家庭或小型企业的宽带接入等场景。

例如在家庭环境中，飞基站可以为家庭成员的手机、电脑等设备提供稳定的网络信号，满足一家人日常上网、观看视频、进行线上办公或者学习等需求；对于小型企业来说，飞基站也能保障办公区域内的通信，方便员工开展工作以及与外界进行业务联系等。

（五）Other special base stations (such as base station vehicles, etc.)

像基站车这类特殊基站，是一种移动式基站，通常安装在车辆上。它具备独特的优势，可用于应急通信、临时活动或特殊场合下的通信支持。

比如在发生洪水、塌方、泥石流等地质灾害，地面传输网络出现损坏，导致传统基站无法正常工作时，基站车就可以快速部署到相应地点，并提供临时的通信覆盖，方便有关部门进行抢险救灾指挥、工作协调，普通百姓也能通过它求救、报平安；在大型集会、演唱会、体育赛事等人员聚集的临时活动场合，基站车同样能发挥作用，保障现场的通信顺畅，满足大量人员的通信需求。

四、Key components of communication base stations

（一）Computer room and its internal equipment

    The computer room of the communication base station is equipped with many key devices that work together to ensure the normal operation of the base station.

    Firstly, there is the signal transceiver, which acts as the "heart" of the base station, responsible for the reception and transmission of wireless signals. On the one hand, it receives signals from mobile devices and converts them into a form that can be processed by the base station; On the other hand, the signal to be transmitted to the mobile device is converted accordingly and sent out to ensure accurate transmission of information between the base station and the mobile terminal.

    Monitoring devices are also indispensable. They are like the "eyes" of a base station, constantly monitoring the operating status of various equipment in the computer room, including key parameters such as temperature, humidity, and voltage. Once parameter abnormalities are detected, timely alerts can be issued to remind staff to come and inspect and handle them, avoiding the impact of equipment failures on the normal operation of the base station.

    The fire extinguishing device plays the role of a "safety guard", and there are a large number of electronic devices placed in the computer room, which poses a certain fire hazard. The fire extinguishing device can quickly activate in the early stages of a fire, extinguish open flames in a timely manner, prevent the spread of fire, minimize damage to base station equipment caused by fire, and ensure the safety of the base station.

    The power supply equipment is equivalent to the "energy source" of the base station, which introduces the mains power and performs corresponding conversion and distribution, providing stable and reliable power support for all devices in the computer room. Whether it's signal transceivers, monitoring devices, or other equipment, they all rely on continuous power supply from the power supply equipment to function properly. Once there is a problem with the power supply, the entire base station will be paralyzed.

    Air conditioning equipment plays a role in regulating the environment of the computer room, maintaining the temperature and humidity within a suitable range. Base station equipment generates heat during long-term operation. If the heat cannot be dissipated in a timely manner, excessively high temperatures can affect equipment performance and even cause equipment damage; However, high or low humidity is also not conducive to the stable operation of equipment. Air conditioning equipment can effectively solve these problems and create a good operating environment for the equipment.

    The equipment in these computer rooms each plays an important role, and they cooperate with each other to ensure the stable and efficient operation of the communication base station. They are an important foundation for the base station to work normally and provide us with high-quality communication services.

（二）Iron tower mast and related structures

    As an important supporting structure for communication base stations, tower masts can be divided into various forms based on shape and other factors, such as angle steel towers, steel tube towers, single tube towers, masts, etc. Each form has its unique application scenarios and characteristics, but it contains several key structural parts that play a crucial role in ensuring the operation of base stations and signal transmission.

    The lightning protection grounding system is an indispensable part of the tower mast, like a "protective umbrella", always protecting the base station equipment from lightning damage. Due to the fact that the tower mast is often high above the ground, it is prone to lightning strikes during thunderstorms. The lightning protection grounding system can introduce the strong current generated by lightning into the ground, avoiding damage to sensitive electronic equipment in the base station caused by the current, ensuring the safety of equipment and personnel, and ensuring stable operation of the base station under various weather conditions.

    The tower body is the main structure of the entire tower mast, which bears the responsibility of supporting equipment such as antennas. It must have sufficient strength and stability to resist the influence of wind, self weight, and other external factors. Different types of tower bodies, such as angle steel towers, are constructed from angle steel and have a solid and stable structure; Steel pipe towers are mainly made of steel pipes, with a simple appearance and low wind load. Choosing a suitable tower structure based on actual construction needs and environmental conditions can better ensure the reliable operation of the base station.

    The basic part is the foundation of the tower mast, deeply rooted underground, firmly fixing the entire tower mast, dispersing various loads transmitted by the tower body, and ensuring that the tower mast will not tilt, collapse or other safety issues during long-term use. The design and construction of the foundation need to be comprehensively considered based on various factors such as the geological conditions, tower height, and load size of the base station, in order to ensure that it can provide stable support for the tower mast.

    The bracket is a structural component used for installing and fixing antennas, cables, and other equipment, ensuring that these devices are in the appropriate position and angle on the tower mast for better signal transmission and reception. A well-designed and installed bracket can enable the antenna to accurately cover the target area, improving the efficiency and quality of signal transmission.

    Cables are the "veins" of signal transmission, connecting equipment in the computer room with antennas and other components on the tower mast. They are responsible for accurately transmitting processed electrical signals to the antenna end for transmission, and also transmitting the signals received by the antenna back to the computer room for further processing. The performance of cables directly affects the quality of signal transmission. High quality cables can reduce signal loss and ensure clear and smooth communication.

    In addition, there are some auxiliary facilities, such as climbing ladders, which facilitate the maintenance and inspection of the tower mast and related equipment by the staff; Lighting equipment provides necessary lighting conditions for nighttime operations. Although these auxiliary facilities may seem inconspicuous, they are essential for the daily maintenance and management of the base station, helping to ensure that the base station provides us with long-term stable communication services.

（三）The Mystery of Antennas

    Antennas are extremely critical components in communication base stations, with different application scenarios and transmission directions, and exhibit different characteristics according to different configuration methods. They play a core role in the signal transmission and reception process of base stations.

    From the perspective of application scenarios, antennas are divided into two types: indoor and outdoor. Indoor antennas are mainly used in densely populated indoor public places with high communication requirements, such as large shopping malls, office buildings, airports, or subway stations. They can provide partial coverage and effectively solve the communication needs of insufficient indoor signal coverage or high-density user areas, allowing people to enjoy smooth communication services indoors and meet various needs such as making phone calls and using the network. Outdoor antennas are often used for wide area coverage in outdoor environments, such as being installed on tower masts to provide wireless signals for larger surrounding areas, ensuring that outdoor mobile devices can smoothly access the network for communication.

    According to the transmission direction, antennas can be divided into directional and omnidirectional types. Omnidirectional antennas exhibit uniform 360 ° radiation in the horizontal direction, commonly known as non directionality, and a beam with a certain width in the vertical direction. Generally, the smaller the lobe width, the greater the gain. They are commonly used in suburban and regional station types with a large coverage area. Directional antennas exhibit directional radiation within a certain angle range in the horizontal direction pattern, and also exhibit a beam with a certain width in the vertical direction pattern. The smaller the lobe width, the greater the gain. They are commonly used in station types of urban residential areas, with small coverage but high user density and frequency utilization. They are suitable for areas with clear requirements for signal coverage direction.

    The role of antennas is crucial in the process of transmitting and receiving signals at base stations. When the base station sends signals to the outside, the electrical signals processed by the equipment in the computer room are transmitted to the antenna end through cables. The antenna converts the electrical signals into wireless signals and radiates them to the surrounding space, allowing mobile devices within the coverage area to receive them; When mobile devices send signals, the antenna can receive these wireless signals and convert them into electrical signals, which are then transmitted back to the data center through cables for further processing.

    There are different configuration methods for antennas, such as omnidirectional transmission and omnidirectional reception. Antennas with omnidirectional configuration can send signals outward in all directions, ensuring that the signals can cover a certain area in all directions. They are suitable for scenarios that require large area coverage and do not require high signal directionality; The omnidirectional configuration can receive signals from various directions, which can better capture signals emitted by mobile devices from different directions and improve the comprehensiveness and accuracy of signal reception. Different configuration methods need to be reasonably selected based on factors such as the specific environment, coverage requirements, and business characteristics of the base station, in order to achieve the best signal transmission and reception effect and ensure communication quality.

（四）Base transceiver station

    A base station transceiver station (BTS) is one of the core components of a communication base station, which covers key contents such as wireless transmission/reception equipment, antennas, and signal processing. It plays an important role as a wireless modem in the entire communication process, responsible for the reception, transmission, and processing of mobile signals, and has a direct impact on network coverage and signal quality.

    The wireless transmission/reception device is a key link in achieving signal conversion and transmission. The receiving device is responsible for receiving wireless signals transmitted from mobile devices through antennas, converting them into digital signals, and preparing for subsequent processing; The transmitting device, on the other hand, converts the digital signal processed by the signal processing part back into a wireless signal and sends it out through an antenna, allowing the mobile device to receive the corresponding information. The process of sending and receiving is like a "porter" of information, ensuring that the information can be smoothly transmitted between the base station and the mobile terminal.

    As a part of the base station transceiver, the antenna has different types and characteristics as mentioned earlier. Here, it works closely with wireless transmission/reception equipment to complete the signal transmission and reception work. Different types of antennas are suitable for different scenarios and requirements, and their performance directly affects the coverage range, strength, and transmission quality of signals. For example, directional antennas can concentrate signals in a certain direction for long-distance and accurate coverage, while omnidirectional antennas can radiate signals in all directions, ensuring that signals can be received in all directions within the coverage area.

    The signal processing part is also an important component of the base station transceiver station. It needs to perform a series of complex processing operations on the received signal, such as filtering, demodulation, decoding, error correction, etc., to ensure the accuracy and reliability of the signal. At the same time, when the signal is to be sent out, it will also perform corresponding encoding, modulation and other processing on the digital signal to be transmitted, so as to meet the requirements of wireless transmission. Through these processing steps, interference during signal transmission can be effectively reduced, signal quality can be improved, and we can ensure clear voice calls and stable data transmission when using mobile devices for communication.

    As a wireless modem, the overall performance and working status of the base station transceiver station play a decisive role in network coverage and signal quality. If the equipment performance of the base station transceiver is excellent, the configuration is reasonable, and the operation is stable, then it can provide stable and high-quality signal coverage for a larger area, meeting the communication needs of many users at the same time; On the contrary, if there is a malfunction or poor performance of the base station transceiver, it may lead to a reduction in signal coverage, weakened signal strength, call interruption, network lag, and other situations that affect the user experience. So, ensuring the good operation of base station transceivers is the key to maintaining high-quality communication services.

五、The Importance of Choosing the Location of Communication Base Stations

（一）Environmental considerations

    When choosing the location of a communication base station, it is necessary to comprehensively consider the surrounding communication environment, as environmental factors have an undeniable impact on the signal transmission of the base station.

    Firstly, it is necessary to avoid areas with strong electromagnetic interference and pulse interference as much as possible, such as radar stations, radio stations, television stations, etc., because the strong electromagnetic or pulse signals generated in these areas are likely to interfere with the communication signals sent and received by the base station, causing signal confusion, loss, or serious degradation of transmission quality, which in turn affects the clarity of communication, network stability, and data transmission speed when we use mobile devices such as smartphones.

    At the same time, it is also necessary to stay away from commercial places and warehouses with a large amount of flammable and explosive products, such as gas stations and enterprises storing flammable and explosive materials. These areas have high safety risks. Once an accident occurs, it will not only cause devastating damage to the base station itself, but may also trigger a series of chain reactions due to damage to the base station equipment, such as communication interruption affecting the development of surrounding emergency rescue work. Therefore, for the dual consideration of safety and stable signal transmission, it is necessary to stay away from these dangerous areas.

（二）View and influence of surrounding buildings

    It is best to build communication base stations within a wide field of view, and there should be no tall buildings around them. This site selection requirement is of great significance for ensuring that the signal transmission of the base station is not obstructed and avoiding signal interference.

    A broad field of view allows the signals emitted by the base station to propagate as far away as possible, reducing the obstruction and weakening of signals by obstacles, and ensuring that mobile devices within the coverage area can smoothly receive strong signals. If there are tall buildings around the base station, the signal will be obstructed, reflected or refracted during the propagation process. As a result, the coverage area of the signal will be reduced, and some areas may have weak or even no signal. Moreover, the reflected and refracted signal may also produce multipath effects, causing delays, distortions and other problems in signal transmission, affecting communication quality. For example, in a city with high-rise buildings, if the base station is improperly located and surrounded by high-rise buildings, the signal in the nearby blocks is prone to instability and intermittent phenomena.

（三）Correlation between Geology and Tower Type Selection

    In the construction of base stations, the selection of towers is crucial, and this requires consideration of the geological conditions of the construction area before scientifically selecting the appropriate tower type.

    Before officially carrying out the design and implementation of communication base station tower selection, it is necessary to conduct a comprehensive investigation of the geological conditions of the construction area to understand whether there are geological risks such as loose soil, easy settlement, and underground caves in the construction area. For example, in some soft soil geological areas, special attention needs to be paid to the stability of the tower foundation; If it is in an earthquake prone area, the seismic performance of the geology should be considered. Based on the understanding of geological conditions, a series of effective measures will be proposed to select the appropriate tower type, and a comprehensive examination of economic, technical, and safety indicators will be conducted to ultimately determine the appropriate form of the iron tower.

    For pile based communication base stations, the selection of the tower must first consider the performance of the pile, including crack resistance and settlement, and analyze and verify these performance indicators, after all, the entire load of the communication tower basically acts directly on the foundation. In order to improve the stability of the tower, special attention must be paid to foundation construction, which includes three different forms: extended foundation, single pile foundation, and group pile foundation. If necessary, such as to further enhance the bearing capacity of the foundation, tie bars and anchor bolts can be added, and liquefaction treatment can be carried out on the foundation to ensure that the iron tower can stand stably for a long time and ensure the normal transmission of base station signals. For example, when constructing base stations in areas prone to liquefaction such as riverbanks and beaches, taking these preventive measures can help the base stations better cope with the challenges brought by complex geological conditions.

六、The radiation from communication base stations

（一）Basic concepts and classifications of radiation

    In daily life, we often hear the word 'radiation', but did you know that radiation is actually classified differently? Radiation can generally be divided into two categories: ionizing radiation and electromagnetic radiation.

    Ionizing radiation, in simple terms, is a type of high-energy radiation that carries photons with energy large enough to break chemical bonds between molecules, such as X-rays, gamma rays, and others that we are familiar with. If the intensity of this type of radiation is too high or the human body is exposed to it for a long time, it will have a destructive effect on biological tissues, so strict protection and dose control requirements are often required when exposed to ionizing radiation.

    Electromagnetic radiation, on the other hand, is a relatively low-energy form of radiation that mainly reflects thermal effects. It is similar to the electromagnetic stove we use in our daily lives to heat food, which relies on the thermal effects generated by electromagnetic radiation and does not damage the molecular bonds of organisms. The radiation generated by communication base stations belongs to the category of electromagnetic radiation.

    In fact, there are various types of radiation present everywhere in our living environment. Household appliances such as radio stations, microwave ovens, computers, televisions, hair dryers, radios, etc. all produce electromagnetic radiation. Even lightning strikes, sunspot activity, the atmosphere, and the universe in nature also produce electromagnetic radiation. It can be said that we are always in an environment of electromagnetic radiation. The electromagnetic radiation generated by base stations has its own characteristics, and it has attenuation during spatial propagation, that is, its radiation intensity will rapidly decay with increasing distance. Moreover, the electromagnetic radiation of base station antennas also has strong directionality, mainly covering nearby areas in a horizontal direction, just like when we open an umbrella, its downward energy is very small. In addition, buildings also have strong shielding effects on electromagnetic fields, so base station antennas built on rooftops usually do not have a significant impact on residents inside the building.

（二）The actual situation of radiation from communication base stations

    When it comes to the radiation level of communication base stations, many friends may not have a clear concept and always feel that the base station looks quite large and conspicuous, and the radiation level should not be small. Actually, compared to our common household appliances, the radiation level of residential base stations is really negligible.

    Let's take a look at the radiation level data of some common household appliances, such as televisions. The radiation intensity tested on the front close to the display screen was 50 microwatts per square centimeter, and the radiation intensity on the back close to the chassis can reach 40 to 50 microwatts per square centimeter; The radiation of a hair dryer can reach 100 microwatts per square centimeter, and the radiation of an induction cooker can even reach 580 microwatts per square centimeter. The commonly used wireless routers in households also generate radiation of over 60 microwatts per square centimeter within a range of 1 meter.

    However, China has strict standards for the electromagnetic radiation of communication base stations. According to the national standard "Electromagnetic Environment Control Limits" (GB8702-2014), the power density of the communication frequency band should be less than 40 microwatts per square centimeter. Considering that base station signals may overlap with each other, operators usually control it within 8 microwatts per square centimeter during actual construction. The radiation coverage area of communication base station antennas is often relatively wide, with radiation power dispersed over an area of several square kilometers. Moreover, the distance between the base station and the human body is generally over 10 meters, so its impact on the human body is much smaller compared to household appliances that come into close contact.

（三）The relationship between network upgrade and radiation changes

    With the continuous development of communication technology, the network is constantly upgrading, such as from 4G to 5G era. Many friends have a question in their hearts, that is, with the upgrade of the network, the radiation of communication base stations also increases? Actually, it's not like that.

    Network acceleration, such as 5G networks being faster than 4G networks, relies not on enhancing the signal transmission power of communication base stations, but on expanding transmission bandwidth, improving anti-interference ability, and receiving sensitivity. It is like widening highways, allowing information to be transmitted more smoothly and quickly, rather than relying on increasing "horsepower" to speed up. And, from 2G base stations to 5G base stations, the radiation is actually getting smaller and smaller. For example, in the 4G era, the power of large base stations was 40 watts, and the power of small base stations was 20 watts. With the support of 5G technology, the power of micro base stations is only 10 watts, and the power of micro base stations even reaches 250 milliwatts. After beamforming, the power allocated to the antenna output port of 5G base stations is only 4 watts. Compared with the power of 15 watts to 40 watts per household lighting lamp, the radiation of 5G base stations can be said to be negligible.