Know 5g, Know 5g

Shanghai Runxin Technology Co., Ltd. Chuang Research Societypreface

With the increasing demand for communication network, it has developed from single voice communication to high-speed Internet access, online viewing of short video and so on. However, this is not enough to meet the development needs. The important changes come from the past communication technologies that provide communication between people. With the rapid development of mobile Internet and Internet of things and the emergence of more and more intelligent devices, in virtual reality, augmented reality, ultra-high definition video, intelligent wear, smart home, intelligent meter reading and intelligent transportation, Unmanned driving and other fields will produce great communication demand. With the continuous growth of user demand, the mobile communication network will face: 1000 times of data capacity growth, 10-100 times of wireless device connection, 10-100 times of user rate demand, 10 times of long battery life, etc. 4G network can not meet these needs, so 5g technology came into being.

electromagnetic wave5g is the fifth generation communication technology, which is mainly characterized by millimeter wavelength, ultra wideband, ultra-high speed and ultra-low delay. 1g 4G focuses on more convenient and fast communication between people, while 5g will realize the interconnection of all things at any time, anywhere and everywhere, so that humans dare to expect to participate in it synchronously without time difference with all things on the earth through live broadcasting.Wireless communication uses electromagnetic wave to communicate. Electromagnetic waves include light waves and radio waves.

The characteristics of electromagnetic wave are determined by its frequency. Electromagnetic waves of different frequencies have different properties, so they have different uses.For example, high frequency X-ray, with strong penetration, can be used for flaw detection or automatic control of assembly line in industry. It has great lethality to cells and is used to treat tumors in medicine.Radio waves are used for communication, and its spectrum resources are limited. In order to avoid interference and conflict and ensure communication quality, we will divide spectrum resources and allocate them to different objects and users.

We mainly use if UHF for mobile phone communication.The spectrum division of 2g-4g of domestic communication operators is as follows. Domestic and global mainstream 4G bands use UHF and UHF.The global 5g frequency range is shown in the figure below

The Ministry of industry and information technology has determined the frequency of 5g (fifth generation mobile communication) in China in the form of notice. The working frequency bands are 3300mhz-3600mhz and 4800mhz-5000mhz respectively. The bandwidth of the first working frequency band is 300 MHz; The bandwidth of the second operating band is 200 MHz. This is a characteristic of 5g communication - Super bandwidth.With the continuous development of communication technology, from the initial 1g to the current 4G, the electromagnetic wave frequency is higher and higher, and the spectrum bandwidth is wider and wider.The higher the frequency, the richer the frequency resources that 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 between frequency and wavelength isIf calculated at 28ghz, wavelength = speed of light / frequency = 300000000 (M / s) / 28000000000 (Hz) = 10.7mm, which is a feature of 5g communication - millimeter wave.

5g advantageSignificant characteristics of 5g communication frequency band: the higher the frequency, the shorter the wavelength, and the closer to linear propagation (the worse the diffraction and wall penetration ability). The higher the frequency, the greater the attenuation in the propagation medium.When 5g communication network signal is covered, the number of base stations required increases significantly and the cost increases significantly. This is part of the reason why 1G-4G communication is useless.

Ultra low delay is a very important characteristic of 5g. Ideally, the end-to-end delay is required to be 1ms, and the typical end-to-end delay is about 5-10ms. Some ideas need to be followed to realize 5g ultra-low delay. First, the transmission delay of air interface should be greatly reduced. Second, we should reduce the forwarding nodes as much as possible and shorten the distance from the source to the destination node. Third, we should take into account the whole, and make the technologies at different levels such as air interface, network architecture and core network cooperate with each other from the perspective of cross layer consideration and design, so that the network can understand the delay requirements of different vertical services.

New frame structure: in terms of frame structure, shorter subframe length will be considered, and ACK / NACK feedback will be completed in the same subframe in order to reduce air interface delay.Terminal direct communication (D2D): in traditional communication mode, data packets pass through the whole network node, and each forwarding means an increase in delay. The mode of direct communication between terminals can realize the communication between devices without transmission through the network.

Sinking of core network functions: in the 4G network, LTE removes the RNC in 3G, transfers most of the functions of RNC to the base station, integrates part of the work into the core network, and adopts the two-layer network architecture of eNodeB and EPC. The flat architecture reduces the nodes and reduces the delay. In the 5g network, some functions of the user side of the core network will further sink to the access network, the original centralized core network will become distributed, and the functions of the core network will be closer to the terminal to further reduce the delay.

Mec (mobile edge computing): MEC pushes computing, processing and storage to the mobile boundary, providing wireless possibility for service innovation at the mobile edge entrance, so that massive data can be processed in real time and quickly to reduce delay.