Initial Concept of Communication Principle

This article is used to answer and perfuse the teacher’s questions and homework. It does not answer the above questions very carefully, but you can use the above questions to understand the principle of communication. Please watch it rationally. If plagiarism is found, please take responsibility.

History of mobile communication

1G

The first generation cellular mobile communication system (1G):

• Duplex and analog system based on frequency division multiple access FDMA, the transmitted wireless signal is analog, so the system is an analog communication system;
• Use cellular networking technology to improve frequency resource utilization;
• Adopt cellular network structure, increase capacity density and activity range

2G

The second generation cellular mobile communication system (2G):

• Digital transmission system, voice quality and security performance have been greatly improved;
• GSM is based on time division multiple access TDMA;
• IS-54 is based on time division multiple access TDMA;
• IS-95 is based on narrowband direct sequence code division multiple access DS-CDMA;
• Appropriately add some modules and some protocols suitable for data services, which becomes 2.5G

3G

The third generation cellular mobile communication system (3G):

• Multi-media functions are added to overcome technical problems such as multipath, delay expansion, multiple access interference, near-far effects, and institutional problems;
• Achieved goals such as global roaming, high-quality multimedia services, multi-layer cell structure, and system capacity expansion;
• There are three CDMA technologies: DS-CDMA (WCDMA), CDMA-TDD (TD-SCDMA), MC-CDMA (CDMA2000), which are constructed and operated by China Unicom, China Mobile and China Telecom.

4G

The fourth generation cellular mobile communication system (4G):

• Orthogonal frequency division multiplexing technology OFDM, software radio technology, smart antenna technology, multiple input multiple output technology MIMO, IP-based core network, etc.;
• WCDMA evolved to FDD-LTE, TD-SCDMA evolved to TDD standard, my country’s TD-LTE was selected, and Wireless MAN-Advanced technology based on IEEE 802.16m also passed

5G

Fifth-generation cellular mobile communication system (5G)

• Use mMIMO, non-orthogonal transmission, full duplex, FBMC, flexible duplex and other technologies, including changes in fields including speed and feed, unlicensed spectrum use, IoT devices, virtualization, and new air interface NR
• There are three application scenarios of enhanced mobile broadband eMBB, high-reliability and low-latency connection uRLLC, and massive IoT mMTC, which can use licensed, unlicensed and shared spectrum, and use two new channel codes: LDPC and Polar codes

Awareness and trend prediction

• Every change in mobile communication technology requires a large amount of capital and technology investment. Through continuous accumulation, the previous technology is gradually improved and innovated, making this a force that promotes the advancement of society, allowing people to gradually get rid of the constraints of reality. Break out
• The future development should be towards perfecting the living space of everyone in society. Through intelligent interconnection and other methods, people can start to influence the things around them and make them a part of themselves, and then connect each independent existence. It is not only the individual who connects each object, but also the connection between each individual, which ultimately forms the advancement and progress of society

Technical characteristics and performance requirements of 5G communication

• High spectrum utilization, high frequency spectrum resources will be used more widely
• System performance is improved. 5G will focus on more extensive multi-point, multi-antenna, multi-user, multi-cell mutual cooperation, and mutual networking. Compared with 4G in terms of data rate, communication capacity, delay and supporting mobile speed, 5G progress
• Energy consumption and operating costs are reduced, and the layout of 5G base stations will become more dense, so the requirements for 5G energy consumption and operating costs will become more stringent

5G communication key transmission technology

Key wireless transmission technology

Massive MIMO technology, non-orthogonal multiple access technology, full duplex communication technology, new modulation technology, new coding technology, high-order modulation technology

Key network technology

Network slicing technology, edge computing technology, service-oriented network architecture

New 5G communication network architecture

The terminal equipment is connected to the base station through the air interface. The base station is connected to the core network through the bearer network as the access network, that is, the telecommunications room. The computer room is then connected to the backbone network through the bearer network. The access network is composed of BBU, RRU, and antenna. Divided into front, middle and backhaul, the core network adopts a service-based SBA architecture based on cloud native architecture design

mMIMO 、 OFDM 、 NOMA 、 CR 、 LTE-U

• mMIMO: MIMO refers to multiple transmitting antennas and receiving antennas. The first m represents Massive, which is large-scale. In 4G, MIMO has up to 8 antennas, which will realize 16/32 and other larger-scale antennas.
• OFDM: Orthogonal frequency division multiplexing technology is one of the realization methods of multi-carrier transmission scheme. Its modulation is based on IFFT and demodulation is based on FFT. It is the most complex and most widely used multi-carrier transmission scheme.
• NOMA: Non-orthogonal multiple access technology. Compared with orthogonal transmission, the receiver complexity is increased, and higher spectrum efficiency is obtained. Among them, there are key technologies such as serial interference cancellation SIC and power multiplexing.
• CR: Cognitive radio, which makes real-time behavioral decisions by understanding the state of the wireless internal and external environment, which is enabled by SDR, while enabling various other technologies
• LTE-U: Unlicensed channel, the solution to the problem of insufficient licensed spectrum proposed in R13, in order to achieve the effect of carrier aggregation, thereby achieving an increase in rate and capacity

VLC 、 mmWave 、 laaS 、 C-RAN

• VLC: Visible light communication, which uses light in the visible light band as an information carrier to directly transmit optical signals in the air
• mmWave: Millimeter wave, the wavelength range is 1mm to 10mm, the biggest difference from previous generations of mobile technology, increased bandwidth and speed, and reduced mMIMO antenna volume
• laaS: Infrastructure as a service, which is the bottom layer of cloud services and provides some basic resources
• C-RAN: This concept comes from the centralized RAN. In order to improve design flexibility and computing scalability, improve energy efficiency and reduce integration costs, the network functions of wireless access are softwareized into virtualized functions and deployed in standard clouds Environment, such as BBU function

Polar code, LDPC code, BCH code, convolutional code

• Polar code: The forward error correction coding method is currently the only method that can be strictly proven to reach the Shannon limit. Huawei uses polar codes in the field of 5G channel coding.
• LDPC code: Low-density parity-check code, a linear block code, used to correct the coding method that occurs during transmission. Its error correction capability is very close to the theoretical maximum. It is mainly promoted by Qualcomm as a control channel ratio coding scheme
• BCH code: a special type of error correction cyclic code, used to correct multiple random error modes, multi-level, cyclic, error correction, variable length digital code
• Convolutional code: an error control code, because the data is related to the binary polynomial sliding, it becomes a convolutional code. It was used in IS-95, TD-SCDMA-WCDMA, IEEE 802.11 and satellite systems before

Pros and cons of 5G

• Advantages: fast data transmission speed, large channel capacity, low latency, large bandwidth, bringing huge market space
• Disadvantages: higher requirements for software and hardware, temporary inability to reduce traffic costs, weak penetration due to the use of millimeter waves, high power consumption of the base station, and relatively small coverage area