This paper mainly briefly introduces the changes of base stations in different generations of wireless communication.
What is a base station? 1G~6G base station changes?
Since the birth of mobile communication networks in the late 1970s, mobile base stations have accompanied mankind for 40 years, bringing unprecedented changes to human society, but do you know its story?
Definition: A base station is a public mobile communication base station. It is an interface device for mobile devices to access the Internet. It is also a form of radio station. A radio transceiver station for information transfer. The construction of mobile communication base stations is an important part of the investment of mobile communication operators. The construction of mobile communication base stations is generally carried out around factors such as coverage, call quality, investment benefits, difficulty of construction, and convenient maintenance. With the development of mobile communication network services in the direction of dataization and packetization, the development trend of mobile communication base stations must also be broadband, large coverage construction and IP.
For most people, when it comes to base stations, the first thing that comes to mind is the picture below:
signal tower
Yes, this is indeed a kind of base station. The function of the base station is to radiate and receive electromagnetic wave signals, allowing nearby communication devices to connect to the communication network. For us, the base station is a signal source. When we get close to it, our mobile phone signal will be full and we can surf the Internet more happily.
With the upgrading of communication technology, what changes have taken place in the base station? Since the base station is responsible for the radiation reception of electromagnetic wave signals, its characteristics are directly determined by the communication frequency band. Regarding the communication frequency band, you can check the frequency subsection of the previous 6G series "Things about 6G-------The frequency is higher" to understand.
In the 1G era , the transmission of analog voice signals was carried out, and the so-called communication was limited to making calls (big phones).
Schematic diagram of a base station in the 1G era
1G is an analog system, not only has low capacity, poor call quality, but also extremely poor confidentiality, but 1G base stations can spread farther, but due to poor communication quality, we do not count the coverage of 1G base stations here.
The 2G era has entered the digital age, and the development of digital circuits has also made mobile terminals smaller. The typical representative is Nokia mobile phones. At this time, the communication frequency is about 1GHz, the corresponding wavelength is about 3m, and the coverage radius of a base station is about 5-10 kilometers . Stepping from 1G to 2G is from analog modulation to digital modulation. In comparison, the second generation of mobile communication has a high degree of confidentiality, and the capacity of the system is also increasing. At the same time, mobile phones can also access the Internet from this generation, but People can only browse some text information.
In the 3G era , with high-bandwidth and stable transmission, video telephony and the transmission of large amounts of data are more common, and mobile communication has more diversified applications, which are regarded as an important key to open a new era of mobile communication. At this time, the communication frequency is about 2GHz, the wavelength is about 1.5m, and the coverage radius of a base station is about 2-5 kilometers . At this point we can surf the Internet to browse pictures and simple web pages.
In the 4G era , it has the characteristics of faster speed, flexible communication, high intelligence, high-quality communication, and low cost, and can meet the requirements of almost all users for wireless services. At this time, the communication frequency is about 3GHz, the wavelength is about 1m, and the coverage radius of a base station is about 1-3 kilometers . At this point we can surf the Internet to brush the video.
In the 5G era , the ITU divides 5G application scenarios into two categories : mobile Internet and Internet of Things . With the characteristics of low latency, high reliability, and low power consumption, 5G has a wide range of application fields. It can not only provide ultra-high-definition video, immersive games and other interactive ways to upgrade; it will support massive machine communication and serve smart cities and smart homes. ; It will also "show its skills" in vertical industries such as Internet of Vehicles, mobile medical care, and industrial Internet. At this time, the communication frequency is about 30GHz, the wavelength is about 10mm, and the coverage radius of a base station is about 100-300 meters .
In the 6G era , terahertz technology is to be adopted, combining millimeter wave and submillimeter wave, and the coverage of a base station is expected to be less than 200m . In the 6G era, the network will be "densified" , and our surroundings will be full of small base stations.
Therefore, the base stations in the future will be more and more like street lights, with a base station every few tens of meters . The difference is that the base station will not rest during the day.
In addition to changes in coverage distance, key technologies in base stations also need to keep pace with the times.
When the frequency of the signal exceeds 10GHz, its main mode of propagation is no longer diffraction. For non-line-of-sight propagation links, reflection and scattering are the main signal propagation methods. At the same time, the higher the frequency, the greater the propagation loss, the closer the coverage distance, and the weaker the diffraction ability. These factors will greatly increase the difficulty of signal coverage. Not only 6G, but also 5G in the millimeter wave band. 5G currently uses two key technologies, Massive MIMO and beamforming, to solve such problems. Massive MIMO mainly compensates the loss on the high-frequency path by increasing the number of transmitting antennas and receiving antennas, that is, designing a multi-antenna array. Spatial multiplexing technology is to increase the amount of transmitted data under the configuration of MIMO multiple antennas. At the transmitting end, the high-rate data stream is divided into multiple lower-rate sub-data streams, and different sub-data streams are transmitted on the same frequency band on different transmitting antennas. Since the spatial sub-channels between the antenna arrays at the transmitting end and the receiving end are sufficiently different, the receiver can distinguish these parallel sub-data streams without paying additional frequency or time resources.
Spatial Multiplexing Technology
MIMO's multi-antenna array concentrates most of the transmitted energy in a very narrow area. Since the area is relatively narrow, there will be less interference between different beams.
However, since the narrow beam emitted by the base station is not 360-degree omnidirectional, it cannot be guaranteed that the beam can cover users in any direction around the base station. In this case, beamforming technology can be used . Beamforming is to manage and control the beam through complex algorithms, making it like a "spotlight". These "spotlights" can find where the mobile phones are clustered, and then cover them with a more focused signal.
5G uses MIMO technology to improve spectrum utilization. The frequency band of 6G is higher, and the further development of MIMO in the future is likely to provide key technical support for 6G.