As people's demand for communication networks continues to grow, it has evolved from a single voice communication to high-speed Internet access and online short video viewing. But this is not enough to meet the development needs. The important change comes from the past communication technology that provides communication between people. With the rapid development of the mobile Internet and the Internet of Things, more and more smart devices appear in the virtual world. Reality, augmented reality, ultra-high-definition video, smart wear, smart home, smart meter reading, smart transportation, unmanned driving and other fields will generate great communication needs. With the continuous growth of user demand, the mobile communication network will face 1000 times the data capacity growth, 10 to 100 times the wireless device connection, 10 to 100 times the user speed demand, and 10 times the long battery life demand in the next 10 years. Wait, 4G network cannot meet these needs, so 5G technology came into being.
Electromagnetic wave
5G is the fifth-generation communication technology. Its main features are millimeter-level wavelength, ultra-wideband, ultra-high speed, and ultra-low latency. Among them, 1G~4G are used for more convenient and faster communication between people, and 5G will realize the interconnection of everything at any time, anywhere, and let humans dare to expect to participate in it synchronously with all things on the earth through live broadcast without time difference.
Wireless communication uses electromagnetic waves for communication. Electromagnetic waves include light waves and radio waves.
The characteristics of electromagnetic waves are determined by its frequency. Electromagnetic waves of different frequencies have different properties and therefore have different uses.
For example, high-frequency gamma rays have strong penetrating power and can be used for flaw detection or automatic control of assembly lines in the industry. It has great lethality to cells and is used to treat tumors medically.
Radio waves use electric waves for communication, and its spectrum resources are also limited. In order to avoid interference and conflicts and ensure communication quality, we will divide spectrum resources and allocate them to different objects and uses.
We mainly use IF~UHF for mobile phone communication.
The frequency spectrum of domestic communication operators 2G-4G is divided as follows. The domestic and global mainstream 4G frequency bands use UHF and UHF.
The frequency range of global 5G use is as follows
The Ministry of Industry and Information Technology has determined the frequency of my country's 5G (fifth generation mobile communication) in the form of a notice. The working frequency bands are: 3300MHz-3600MHz frequency band and 4800MHz-5000MHz frequency band. The bandwidth of the first working frequency band is 300 MHz; the bandwidth of the second working frequency band is 200 MHz. And this is a feature of 5G communications-ultra-bandwidth.
With the continuous development of communication technology, from the initial 1G to the current 4G, the electromagnetic wave frequency used is getting higher and higher, and the spectrum bandwidth is getting wider and wider.
The higher the frequency, the more abundant frequency resources can be used, and the wider the spectrum bandwidth. The higher the transmission rate that can be achieved-ultra-high speed.
At present, 28GHz is mainly used for testing in the world.
The conversion formula of frequency and wavelength is:
If calculated at 28GHz, wavelength=speed of light/frequency=300000000(m/s)/28000000000(Hz)=10.7mm, and this is a feature of 5G communication-millimeter wave.
5G advantages
The salient features of the 5G communication frequency band: the higher the frequency, the shorter the wavelength, and the closer it is to linear propagation (the poorer the diffraction and wall penetration capabilities). The higher the frequency, the greater the attenuation in the propagation medium.
When 5G communication network signal coverage, the number of base stations required will increase significantly, and the cost will increase significantly. This is part of the reason why 1G-4G communication is useless.
Ultra-low latency is a very important feature of 5G. Ideally, the end-to-end delay is required to be 1ms, and the typical end-to-end delay is about 5-10ms. To achieve 5G ultra-low delay, some ideas need to be followed. First, the transmission delay of the air interface must be greatly reduced. Second, it is necessary to reduce forwarding nodes as much as possible, and shorten the distance between source and destination nodes. Third, we must take the whole into consideration, from the perspective of cross-layer considerations and design, make the air interface, network architecture, core network and other technologies at different levels cooperate with each other, so that the network can understand the delay requirements of different vertical services.
New frame structure: In terms of frame structure, a shorter subframe length will be considered, and ACK/NACK feedback will be completed in the same subframe, in order to limit the air interface delay.
Terminal direct communication (D2D): In traditional communication methods, data packets have to pass through the entire network node, and each forwarding means an increase in delay. The direct communication mode of the terminal can realize the communication between the devices without passing through the network.
Core network function sinking: In the 4G network, LTE removes the RNC in 3G, transfers most of the RNC functions to the base station, and integrates part of the work into the core network, using a two-layer network architecture of eNodeB and EPC. The flat architecture reduces the number of nodes and reduces the delay. In the 5G network, part of the core network user plane functions will further sink to the access network, the original centralized core network becomes distributed, and the core network functions are closer to the terminal to further reduce the delay.
MEC (mobile edge computing), mobile edge computing: MEC pushes computing, processing and storage to the mobile boundary, and provides wireless possibilities for mobile edge entry service innovation, so that massive data can be processed in real time and quickly to reduce latency.
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