5g has been fully commercialized. With the continuous penetration of 5g in the vertical industry, people's idea of 6G is gradually put on the agenda. Facing 2030 +, 6G will fully support the digitization of the whole world on the basis of 5g, and combine the development of artificial intelligence and other technologies to realize the universal desirability of wisdom, fully enable everything, promote the society to move towards the "digital twin" world combining virtual and reality, and realize the beautiful vision of "digital twin and universal wisdom".

Around this overall vision, 6G network will give birth to new application scenarios in three aspects: intelligent life, intelligent Fu production and intelligent society, such as twin digital people, holographic interaction, super transportation, synaesthesia interconnection, intelligent interaction, etc.

These scenarios will require terabit peak rate, sub millisecond delay experience, mobile speed of more than 1000km / h, and new network capabilities such as security endogenous, intelligent endogenous and digital twin. In order to meet the higher requirements of new scenarios and new services, 6G air interface technology and architecture need to be changed accordingly.

 

01、Future network technology  

   

At present, with the deep integration of information and communication technology, big data and artificial intelligence, the further expansion of network ubiquity, the continuous improvement of user experience and personalized service demand, and the continuous emergence of many new enabling technologies, the network will also show the following major characteristics and development trends in the future.

1、Full spectrum communication

With the continuous improvement of communication demand, mobile communication networks need more spectrum. Since the spectrum below 6GHz has been allocated, and the 26ghz and 39ghz millimeter wave bands have been allocated to 5g, it is necessary to study higher frequency bands, such as THz and visible light, to meet the needs of higher capacity and ultra-high experience rate.

Visible light usually refers to the electromagnetic wave in the frequency band of 430 ~ 790thz (wavelength of 380 ~ 750nm), with a candidate frequency spectrum of about 400thz. Terahertz refers to the electromagnetic wave in the frequency band of 0.1 ~ 10THz (wavelength of 30 ~ 3000 microns), which is called a candidate frequency spectrum of about 10THz. Both of them have the characteristics of large bandwidth and are easy to realize ultra-high rate communication. They are a potential supplement to the future mobile communication system.

Frequency distribution

The spatial transmission loss of visible light and terahertz is very large, so it is not suitable for long-distance transmission in ground communication, but for providing larger capacity and higher rate in local and short-distance scenes.

In order to improve the coverage, visible light communication can take advantage of its characteristics of low power consumption, low cost and easy deployment, and combine with the lighting function to adopt ultra dense deployment to achieve more extensive coverage; Terahertz communication is more suitable for combination with large-scale antenna due to its long wave length, small antenna array size and low transmission power. It forms a terahertz beam with narrower width and better directivity, effectively suppresses interference and improves coverage distance.

From the perspective of the deployment of the whole 6G mobile communication network, it is necessary to comprehensively consider the cost, demand and business experience, and effectively use all available frequency resources in different scenarios. The frequency band below 6GHz will still play an important role, especially providing seamless network coverage. Millimeter wave will play a more important role. THz and visible frequency bands will provide greater capacity and higher rate in local and short-distance scenes.

Therefore, after visible light and terahertz communication are introduced into the mobile communication network, it is necessary to consider the deep integration networking of all frequency bands below 6GHz, millimeter wave, terahertz and visible light, so as to realize the dynamic complementarity of each frequency band, so as to optimize the overall service quality of the whole network and reduce the network energy consumption.

2、Integration of heaven and earth

In the future, while greatly improving the user experience rate, the network will also meet the network service needs of aircraft, ships and other onboard internet, ensure the service continuity of high-speed mobile ground vehicles, high-speed railways and other terminals, and support the deployment of massive IOT equipment such as real-time rescue and disaster relief, environmental monitoring, forest fire prevention, no man's land patrol inspection and ocean container information tracking, Realize the needs of low-cost coverage in sparsely populated areas. Therefore, the main form in the future is to expand the network coverage to the three-dimensional coverage network of natural space such as space, deep mountains, deep sea and land. Therefore, it is necessary to build an integrated space-time network to realize the three-dimensional "ubiquitous coverage" of the global communication network.

The air space integration network mainly includes three parts: the space-based composed of different orbit satellites, the space-based composed of various air vehicles, and the ground composed of satellite ground stations and traditional ground networks. It has the characteristics of wide coverage, flexible deployment, ultra-low power consumption, ultra-high precision and not easy to be affected by ground disasters.

Air space integration network

The 6G oriented air space integration takes the satellite communication network as an important supplement and extension of the ground communication network, and deeply integrates the two to significantly improve the user's air interface access capability and three-dimensional coverage capability. Through the satellite ground resource cooperative scheduling and satellite ground seamless roaming of the air-space integrated network, users can be provided with non perceptual consistency services to ensure network toughness, robustness and green intensive resources.

3、Doict fusion

6G is a new generation mobile communication system with deep integration of communication technology, information technology, big data technology, AI technology and control technology, showing strong interdisciplinary and interdisciplinary development characteristics. 6G's vision of "digital twin and ubiquitous wisdom" requires end-to-end design from multiple links of information collection, information transmission, information calculation and information application. Doict convergence will be the development trend of 6G end-to-end information processing and service architecture.

ICT deep integration promotes the full dimensionality of the network, which is the basis of flexible networks. The deep integration of ICT promotes the full penetration of artificial intelligence and big data into the network, which is the basis of intelligent network. The deep integration of doict promotes the development of deterministic network and is the basis of automation system and digital twin system.

Doict will realize the deep integration of cloud, network, edge, end and industry on the basis of big data flow, create a trusted environment by means of blockchain, improve the resource utilization efficiency of all parties, and jointly upgrade cloud computing capacity, network capacity, terminal capacity and business capacity.

4、Network reconfigurability

With the rapid development of mobile communication technology, business needs and scenarios are more diversified and personalized. In the future, 6G network will adopt more flexible reconfigurable architecture design.

On the one hand, based on shared hardware resources, the network allocates corresponding network and air interface resources for different services of different users to realize end-to-end on-demand services, and realize resource sharing while providing extreme services, so as to maximize resource utilization and reduce network construction cost; On the other hand, the minimalist network architecture and flexible and scalable network characteristics provide great convenience for subsequent network maintenance, upgrading and optimization, and further reduce the network operation cost of operators. In addition, facing the endogenous characteristic requirements of 6G intelligence, it also puts forward stronger computing power and scalability for the network.

5、Perception communication computing integration

Perception communication computing integration refers to the end-to-end information processing technology framework that synchronously performs information collection and information computing in the process of information transmission. It will break the chimney information service framework of terminal information collection, network information transmission and cloud computing. It is to provide unmanned Immersive and digital twins are the technical requirements of highly coupled services in perceptual communication and computing.

The integration of perception, communication and computing is divided into two levels: functional collaboration and functional integration. In the functional collaboration framework, perceptual information can enhance communication capability, communication can expand perceptual dimension and depth, computing can carry out multi-dimensional data fusion and big data analysis, perception can enhance the performance of computing model and algorithm, communication can bring ubiquitous computing, and computing can realize super large-scale communication.

In the function fusion framework, the sensing signal and communication signal can integrate waveform design and detection, and share a set of hardware equipment. At present, radar communication integration technology has become a hot spot. The integration of terahertz detection capability and communication capability, as well as the integration of visible light imaging and communication has become a potential technical trend of 6G. Perception and computing are integrated into a computing power perception network, and computing and network integration realize the end-to-end definable and microservice architecture of the network.

In the future, perceptual communication computing can realize functional reconfiguration based on the development of software defined chip technology.

Perception communication computing integration application scenario

The application scenarios of perception communication computing integration include unmanned services, immersive services and digital twin services. In the field of unmanned business, it provides the ability of agent interaction and collaborative machine learning; in the field of immersive business, it provides the ability of perception and rendering of interactive XR, the ability of perception, modeling and display of holographic communication; in the field of digital twin business, it provides the ability of perception, modeling, reasoning and control of the physical world; in the field of body area network, it provides personnel monitoring Human parameter perception and intervention ability.

 

02、Wireless enabling technology  

 
   

Facing the new index requirements brought by new application scenarios, such as TBPs peak rate, Gbps user experience rate, near wired connection delay and other requirements, it is difficult to meet only relying on the existing 5g technology. Therefore, the industry is also actively studying some new technologies, new architectures and new designs, hoping to form some new breakthroughs. This chapter will analyze the potential key technologies of future wireless access network from three aspects: basic transmission technology, protocol and architecture design and autonomous network technology.

As we all know, larger bandwidth can improve the peak rate of the system, but the improvement of spectral efficiency still depends on the development of physical layer transmission technology.

1、Distributed very large scale MIMO

After the introduction of super large-scale MIMO, the 4G / 5G network capacity has been greatly improved. However, due to path loss and inter cell interference, the user experience at the cell edge still needs to be improved. Distributed super large-scale MIMO extends the traditional centralized deployment mode to distributed deployment, introduces intelligent cooperation among multiple distributed nodes, and realizes joint scheduling of resources and joint transmission of data, as shown in the figure below. Through distributed deployment and intelligent cooperation, on the one hand, it can effectively eliminate interference and enhance signal reception quality; On the other hand, effectively enhance coverage and bring users a borderless performance experience. It will show great application potential in the future 6G network, especially in higher frequency band and intensive deployment scenarios.

Distributed very large scale MIMO

The industry has theoretically demonstrated the advantages of distributed MIMO in improving channel capacity. Theoretical analysis shows that under the same conditions of total number of antennas, total transmission power and coverage, the performance of distributed MIMO system is more uniform than that of centralized MIMO, especially for edge users.

Due to the significant increase of antenna size and number of nodes, distributed super large-scale MIMO challenges the information interaction ability between nodes, joint cooperative node selection and shape scheme design, algorithm complexity, interference processing and so on; At the same time, coherent joint transmission also puts forward higher requirements for the consistency of transceiver channels between nodes, and the air interface calibration scheme needs to be further studied.

2、Intelligent hypersurface

The Reconfigurable Intelligent surface (RIS) controls the electromagnetic wave through the structural units on the surface, and adjusts the parameters and position of each structural unit to adjust the reflection / emission amplitude and phase distribution of any electromagnetic wave. It has positive significance in solving the pain points of traditional wireless communication, such as non line of sight transmission and reducing coverage holes.

The following figure shows a system diagram of wireless communication assisted by RIS. The base station controls the RIS, and the RIS adjusts the amplitude and phase of its own structural unit based on the control, so as to realize the controlled reflection of the transmitted signal of the base station. Compared with traditional relay communication, RIS can work in full duplex mode and has higher spectrum efficiency. RIS does not need RF link and large-scale power supply, and will have advantages in power consumption and deployment cost.

RIS auxiliary communication system

The practical application effect of RIS in wireless mobile communication depends on the research maturity of metamaterials and the accuracy and efficiency of digital control of metamaterials. At the same time, the difficulty of super surface channel estimation caused by passive characteristics, the practical joint precoding scheme between base station and RIS, and the RIS network architecture and control scheme need to be further studied.

3、Super Nyquist transmission technology

In traditional communication systems, in order to avoid inter symbol interference (ISI), Nyquist criterion is usually used, which limits the symbol rate of transmission. Super Nyquist transmission technology error flavor found reference source. Send symbols at a faster rate, artificially introduce ISI during transmission, and then use a higher-level receiver to eliminate ISI through oversampling at the receiver, as shown in the figure below, so as to improve the actual transmission rate and spectrum utilization of the link.

Transceiver block diagram of super Nyquist transmission system

The power spectral density of super Nyquist transmission signal is only related to the frequency response function of transmission filter, and will not expand the bandwidth. In the following figure, the bandwidth of super Nyquist transmission system and traditional Nyquist system is compared. The baseband time domain waveform is rectangular wave, and the number of overlapping layers of super Nyquist transmission system is 4. It can be seen from the figure that the super Nyquist transmission system will not change the distribution shape of the spectrum, that is, it will not expand the bandwidth.

Bandwidth comparison between super Nyquist system and Nyquist system

In multi antenna antenna system, super Nyquist transmission technology is used to generate delay between transmitting antennas, and oversampling is used to create virtual receiving antennas, which can improve spatial multiplexing and diversity gain when the number of antennas on the user side is limited. Therefore, even a single antenna user can achieve spatial multiplexing gain. It can be seen from the figure below that the virtual antenna system based on ultra Nyquist transmission has obvious gain compared with the traditional miso at high signal-to-noise ratio, and can obtain more than 40% capacity gain at signal-to-noise ratio of 10dB.

Capacity comparison between super Nyquist transmission system and traditional Nyquist transmission system

The optimal decoding algorithm of super Nyquist transmission technology is Viterbi decoding algorithm based on maximum likelihood sequence estimation. However, its complexity increases exponentially with the increase of overlap. Therefore, the design of low complexity receiver is very important for the practical development of the system. At the same time, multi carrier and large-scale antenna are still the mainstream technology in the future. How to combine with OFDM / MIMO technology and consider the impact of actual multipath fading channel on the system needs to be deeply discussed.

4、Transform domain waveform

Waveform technology plays an important role in the air interface design of wireless communication systems in previous dynasties. The performance of OFDM waveforms used in 4G and 5g systems depends on the orthogonality between their subcarriers. If the orthogonality between subcarriers is destroyed by factors such as Doppler frequency offset, the performance will often decline significantly.

Schematic diagram of transform domain waveform

The transform domain waveform aims to overcome the above shortcomings of OFDM waveform. Different from the traditional waveform scheme, which considers that the transmission symbol is located in the classical time-frequency domain, the transform domain waveform considers that the transmission symbol is located in other dual domains (such as delay frequency, time-varying Doppler and other dual domains), as shown in the following figure. Through the transformation between dual domains, the transform domain symbols can achieve a multi-dimensional diversity effect, so that the adverse factors such as Doppler frequency offset in OFDM waveform can be effectively used as a diversity degree of freedom to improve the transmission performance.

Performance comparison between transform domain waveform and OFDM

The figure above shows the block error rate performance comparison between transform domain waveform and OFDM under the assumption of ideal channel estimation in 500km / h mobile environment. In the simulation, the CDL channel model is considered, the subcarrier interval is 60KHZ, the channel coding is convolutional code with 1 / 3 code rate, the number of subcarriers is 128, and the joint processing of six consecutive time-domain OFDM symbols is considered for the transform domain waveform. The results show that the transform domain waveform can effectively deal with the Doppler frequency offset in high-speed mobile environment and achieve better block error rate performance.

Although related research shows that the transform domain waveform scheme can achieve significant gain compared with the traditional OFDM based waveform scheme in high-speed mobile scenes, how to accurately recover the transmitted signal at a low cost is an important topic in the transform domain waveform research. In addition, how to design efficient reference signals to accurately obtain multi antenna channels with low overhead needs further research.

5、AI driven physical link

Since 5g communication, the intelligence of wireless network has become an important topic, which aims to achieve more efficient allocation and utilization of network resources. As one of the main enabling technologies of wireless network intelligence, AI technology is penetrating into the core network, network management, physical layer and high-level protocol stack of access network. Among them, physical layer AI generally refers to the technical scheme to realize or enhance the physical layer function of wireless network by using artificial intelligence / machine learning method.

AI in the physical layer can be mainly applied to CSI processing, receiver design and end-to-end link design. For example, the neural network in deep learning is used to learn the compressed representation of high-dimensional CSI in wireless communication, so as to reduce the CSI feedback overhead; Using artificial neural network to learn the inverse mapping from the received interference signal to the original signal, there is no need for explicit channel estimation and equalization; By jointly optimizing the transmitter and receiver in a specific channel environment, we can learn the non ideal effects in the channel and improve the transmission performance.

However, it is difficult to surpass the traditional design by using AI module to replace the traditional physical layer module in the way of "black box". In contrast, the idea of combining artificial intelligence methods with human expert knowledge is a better choice to absorb the advantages of both sides. In addition, in order to give full play to the potential of AI in reducing overhead and complexity, it is necessary to design the reference signal and air interface resource allocation accordingly, or even the joint design between multi link modules. Therefore, it may have more impact on the existing air interface framework and signaling design.

6、Plug and play link control

6G wireless access network needs to have the ability of automatic coverage expansion to better complete the three-dimensional full scene coverage. When a new network service body joins the network, it can quickly shake hands and plug and play to realize coverage expansion. The plug and play link control technology includes the following aspects:

Process awareness: perceive various types of access requests and start appropriate handshake and control signaling processes. For different types of access points, it is necessary to accurately identify, quickly complete access and realize flexible expansion of coverage.

Cloud to edge control and coordination: flexible and accurate control of edge access points by the cloud, including access control, automatic allocation of bandwidth resources and inter link coordination. AI capability can be introduced into cloud processing to support the above functions.

Self generation and self optimization of access points: use digital Twin / AI and other technologies to fully automate and monitor all access points throughout their life cycle. When the access point newly joins the network, it can automatically complete the configuration and realize self generation; When the access point is running, the parameters are adjusted and automatically optimized according to the real-time scene, and the service is improved as needed to better meet the needs of users.

Plug and play link control

High speed and efficient transmission channel and large bandwidth and high real-time transmission bandwidth are required between cloud and edge to ensure the real-time information interaction between plug and play interfaces. At the same time, powerful digital twins and AI algorithms are also required to complete the automatic control of remote access points.

7、QoS control of adaptive air interface

The 6G era will be a highly digital and intelligent era. Holographic image, XR service, virtual space perception and interaction and other new services all put forward more extreme requirements for the service quality assurance of 6G network.

The QoS control of adaptive air interface is based on the end-to-end QoS constraints, and realizes the QoS guarantee of air interface transmission data according to the real-time air interface transmission characteristics, relatively limited air interface resources, transmission feedback time constraints, etc. it is the key technology of on-demand air interface service and efficient network capability.

The QoS control of adaptive air interface includes the following aspects:

1、Flexible QoS detection mechanism: combine AI / big data technology to realize QoS detection, modeling and adaptive adjustment of hosted services.

2、Deep integration of business QoS and air interface capability: explore a new QoS mechanism combining business QoS and air interface service capability. Based on the precise requirements of the service, the wireless access network matches the service requirements with the real-time air interface status through scheduling and wireless resource management.

3、End to end QoS mechanism of as layer: the terminal carries out more detailed QoS management in combination with the QoS information provided by the access network to realize the accurate and efficient transmission of uplink and downlink data on the air interface.

Facing the future, the service requirements of 6G network are evolving. QoS mechanism involves core network, transmission network and access network. The unified and coordinated QoS mechanism of transmission layer and access network combined with core network is a follow-up problem to be considered.

 

03、Network enabling technology  

   

1、Lightweight signaling scheme

From the development process of 2G, 3G, 4G to 5g, with the continuous expansion of network scale and the increasing complexity, it leads to the complex redundancy of network architecture. According to the existing network development trend, the complexity of 6G network supporting the interconnection of all things will increase geometrically. Lightweight signaling scheme is an inevitable choice for 6G design.

6G wireless access network needs to be designed according to the unified signaling scheme, integrate a variety of air interface access technologies under the unified signaling control, realize the unified control of air interface and reduce the complexity of terminal access network. In terms of protocol stack function design, differentiated protocol function design can be considered, protocol function distribution and interface design can be optimized, and protocol function can be further enhanced combined with AI technology.

In terms of network function, 6G network can be divided into wide coverage signaling layer and on-demand data layer. Through the mechanism of separating signaling plane and user plane, a unified signaling coverage layer is adopted to ensure reliable mobility management and fast service access; Through dynamic on-demand data layer loading, it can meet the business needs of network users. The two cooperate flexibly to reduce the number of base stations deployed and improve users' service perception experience.

Lightweight signaling control

The lightweight signaling scheme needs the support of transmission network with high reliability, low delay and low cost. The transmission network needs flexible topology and sufficient bandwidth. The integrated design of wireless control center, transmission network and network access point is required. In addition, signaling and service separation need to coordinate the 6G available frequency band to give full play to the advantages of wide coverage and flexible service loading.

2、End to end service design

With the deep integration of doict technology and the emergence of a large number of new services, operators need the network to have the ability to respond quickly to new requirements in order to provide network services quickly. Cloud native service-oriented technology is an important technology to enable the above capabilities, driving the evolution of protocol functions to service-oriented architecture. The protocol function based on service architecture has the ability to run the protocol function according to business requirements. The technical characteristics are reflected in the following aspects:

1、Protocol functions driven by cloud native service technology: on the premise of complying with the logical constraints of each protocol layer, the protocol functions are implemented into modules that can be flexibly combined. Each module can be flexibly combined, deployed and operated as needed to realize the service capability of new network services.

2、Cloud native service technology driven interface: the internal and external interfaces of the access network are reconstructed based on the cloud native service interface form and interface protocol, which has supported the flexible combination of protocol function modules and open network capability;

3、Cloud native service technology driven capability opening: provide a convenient, fast and unified access network information exchange mechanism and policy adjustment mechanism to third parties to achieve intelligence and win-win results.

Protocol based on Service Architecture

The functions after protocol function reconstruction include basic functions and incremental functions:

1、Basic functions include cell level functions, such as connection management, user plane management, UE energy-saving management and corresponding network services.

2、Incremental functions include access network service registration, data acquisition and storage, capacity opening, AI analysis and decision-making and corresponding network services.

The high real-time and high flexibility of access network function put forward high requirements for the storage, computing power and real-time information interaction of the platform. Whether doict deep fusion technology can support this requirement needs further research and verification. At the same time, the access network has close functional coupling. How to achieve reasonable "high cohesion and low coupling" is a complex system engineering. Moreover, compared with traditional solutions, the current service technology brings an increase in the cost of single equipment. How to balance the cost and income is a systematic problem.

The protocol based on service architecture runs on the cloud platform, and uses the cloud native to realize the development, deployment and management based on micro service. The cloud native platform needs to adapt to the network characteristics and realize efficient, open and cross cloud deployment.

Evolution trend of cloud technology

In the past 20 years, computing technology has experienced rapid development from bare metal to virtual machine and container. Cloud native has become the most suitable technical practice for Cloud Architecture. Cloud native is an idea for cloud application design. Giving full play to the best practice path of cloud efficiency can help operators build elastic, reliable, loosely coupled, easy to manage and observable network systems, improve delivery efficiency and reduce operation and maintenance complexity. Representative technologies include immutable infrastructure, service grid, declarative API and serverless. The cloud native technology architecture has the following typical characteristics:

• The extreme elasticity can realize the response of seconds or even milliseconds;

• Highly automated scheduling mechanism can achieve strong self-healing ability;

• High adaptability enables large-scale replicable deployment across regions, platforms and even service providers.

  
  

Cloud native greatly reduces the threshold of cloud computing, enables cross domain collaboration between R & D and operation and maintenance, improves the speed of open iteration, and enables business innovation. At present, cloud native hotspot technologies are showing a blowout, including multi cloud container orchestration, cloud native server, cloud native storage, cloud native network, cloud native database, cloud native message queue, service grid, serverless container, function as a service (FAAS), back-end as a service (baas), etc.

Telecom services have higher requirements for performance, low delay, reliability, security and equipment cost. These require cloud native technology to evolve according to the characteristics of telecom services to meet the characteristics of high standards of telecom services.

3、Intelligent perception function

For 6G, there are more and more cloud strong interactive services with ultra-low delay and high bandwidth. The existing "layered" and "chimney" designs of application layer, service transport layer and mobile network layer cause the extension of data packet transmission and the decline of user experience.

In order to realize the real-time and accurate matching of service transmission capability and network capability, it is necessary to introduce high-precision real-time measurement and feedback of each protocol layer of the end-to-end network to enable collaborative optimization, and introduce intelligent processing functions at the network end, including intelligent estimation and prediction. On the one hand, it preprocesses the measured and interactive data to realize dimensionality reduction and compression, On the other hand, subscribe and notify according to the requirements of application layer & service transport layer, so as to reduce the overhead of network transmission.

Cross layer joint architecture design

At the same time, it makes a deep intelligent perception of the transmission requirements of the application layer, realizes the real-time perception and prediction of the transmission requirements at the packet level on the premise of fully protecting the user's privacy, and provides fine-grained guidance for the congestion control of the service transmission layer and the resource scheduling of the mobile network layer.

Smart perception network service system needs multi protocol layer, multi network element and multi technology field cooperation. It faces many challenges, such as difficult verification of technical scheme and the introduction of potential non-standard functions. At the same time, since the joint design of protocol layers and the standardization of interaction involve multiple standards organizations and working groups, the promotion of new technologies in standardization is facing great challenges.

4、Network autonomy system based on digital twin

Digital twin technology refers to the establishment of a virtual entity of the physical world entity in the digital world by digital means, so as to realize the dynamic observation, analysis, simulation, control and optimization of the physical world entity. Digital twin network technology includes function modeling, network element modeling, network modeling, network simulation, parameter and performance model, automatic test, data acquisition, big data processing, data analysis, artificial intelligence machine learning, fault prediction, topology and routing optimization. Thus, the difficult problems in each stage of the network can be transformed into the digital world to solve, and the autonomy of the network can be realized through monitoring, prediction, optimization and simulation.

Digital twin to realize network autonomy

Based on digital twin technology and artificial intelligence technology, 6G network will be an autonomous network with the ability of self optimization, self evolution and self growth. The self optimizing network predicts the trend of the future network state in advance, intervenes in advance for the possible performance degradation, continuously optimizes and simulates the optimal state of the physical network in the digital domain, and issues the corresponding operation and maintenance operation in advance to automatically correct the physical network.

Self evolving network analyzes and makes decisions on the evolution path of network functions based on artificial intelligence, including the optimization and enhancement of existing network functions and the design, implementation, verification and implementation of new functions. The self growing network identifies and forecasts different business needs, automatically arranges and deploys the network functions of each domain, and generates end-to-end service flows to meet business needs; Automatic capacity expansion shall be carried out for stations with insufficient capacity, and automatic planning, hardware self startup and software self loading shall be carried out for areas without network coverage.

As a new concept applied in the network field, digital twin technology needs to form more consensus in the industry. From the process of industry and other industries, this will take a long time. At the same time, digital twin technology relies on a large number of data acquisition, which will increase the equipment cost, and the way of data acquisition also needs breakthrough innovation。

5、Deterministic data transmission

The concept of certainty was first proposed and standardized in IEEE. The IEEE 802.1 working group created the audio video bridging (AVB) task force in 2007. Its goal is to replace HDMI, speakers and coaxial cables in the home with Ethernet. With the successful application of IEEE 802.1avb standard in studios, sports and entertainment places, this technology began to attract the attention of industry and automobile industry.

In 2012, the IEEE 802.1avb task force was renamed the time sensitive network (TSN) task force. TSN standard extends AVB technology, has mechanisms to ensure real-time performance such as time synchronization and delay guarantee, and supports traffic scheduling and shaping, reliability, configuration management and other related protocols. In 2015, IETF established the deterministic network (DetNet) working group, which is committed to extending the deterministic technology based on Ethernet to the wide area IP network, providing the worst-case limits of delay, packet loss and jitter, so as to provide determined data transmission.

It can be seen from the above that the deterministic transmission of fixed network has been proposed for 10 years, but the research on deterministic transmission for mobile network has just started, mainly because 1. The air interface is easy to be affected by the environment, and the transmission quality is difficult to predict; 2. Lack of end-to-end deterministic guarantee mechanism.

In the 6G era, deterministic data transmission will become the representative capability of 6G network to realize the characteristics of bounded delay, low jitter, high reliability and high-precision time synchronization. The difficulties to be overcome include the following aspects:

1、How to realize flexible resource reservation and real-time scheduling of wireless air interface. The unpredictability of air interface is the main bottleneck to realize end-to-end deterministic transmission. This requires that in the 6G era, firstly, the air interface resources are sufficient and unrestricted. The data packets can be flexibly scheduled in real time in the access network to ensure that the packets can be processed and sent within the specified time.

2、How to realize wide area deterministic transmission mechanism. IEEE TSN technology is difficult to be applied in wide area, mainly because CNC in TSN system can not carry out large-scale path operation and accurate real-time scheduling, and the time synchronization accuracy becomes lower and lower with the extension of path.

3、How to realize cross layer and cross domain deterministic mechanism integration. In the 5g era, mobile network is still a layer network carried on IP, which poses a severe challenge to cross domain collaborative deterministic transmission scheduling. In the 6G era, from the beginning of network design, we hope to realize heterogeneous access, fixed mobile integration and collaborative management. Mobile networks need to absorb the two-tier and three-tier deterministic transmission protocols of existing fixed networks to realize deployment integration, protocol support and collaborative scheduling, so as to realize end-to-end cross layer and cross domain deterministic data transmission.

6、Programmable network

6G network needs to support network programmability and realize the cooperation of five networks: access, edge, core, wide area and data, so that the telecom network can be customized across multiple services, multiple fields and the whole life cycle. Network programmability is embodied in many levels, from bottom to top, chip programmability (such as P4 and POF), FIB programmability (such as openflow), rib programmability (such as BGP and PCEP), device OS programmability, device configuration programmability (such as cli, NETCONF / Yang and ovsdb), controller programmability and service programmability (such as GBP and NEMO).

The future network needs to meet the programmability from four dimensions: network element, protocol, service and management:

1、Device network element programmability: with the diversification and personalization of data service types, in the face of the endless demand of users for new network functions, the network functions supported by the protocol stack of the device network element are limited, and the network card chip used can not predict all possible network functions in the next few years. As the basic component of the network, the network element needs its hardware architecture to allow users to redefine functions and complete the processing of different types of protocols, encapsulation and unpacking as needed.

At the same time, the upper software architecture is composed of modules or APIs with clear function division, which allows users to reorganize these modules or call interfaces to achieve customized purposes, such as classification, shaping, QoS, etc. The device network element supports programmability, which makes it possible to efficiently support the customization of users and the continuous evolution of new protocols.

2、Network protocol programmability: the function division of telecom network and data network is becoming more and more blurred, and the network protocol and architecture are infiltrating each other. With the continuous evolution of application scenarios, new requirements for network protocol stack functions emerge one after another, and the evolution and innovation of network protocols are also emerging (such as newip, srv6, quic, etc.). In the face of the long-term coexistence of old and new protocols, it is bound to require that end-to-end intra network and inter network protocols can support synchronous switching, Even according to the user service type and quality requirements, the slice end-to-end network protocol is selected as needed. And then realize the smooth switching from 5g + network to 6G network.

3、Service path programmability: the end-to-end network carries more and more abundant services. We need to see that the time for the network or network element to complete the new service upgrade is sequential. It supports the configuration of different user data on demand and the use of different business processing paths. It can not only adopt the old transformation scheme, but also realize the gradual drainage and smooth switching to the innovative network architecture, so as to meet the unlimited expansion of user needs on the basis of limited cost. Further, only when the forwarding path from the terminal, access network, core network, wide area network and the whole network of the data center is measurable and adjustable, can the end-to-end service, network and edge coordination be truly realized, and end-to-end network guarantee be realized.

4、Programmable management mode: with the increasing complexity of telecom network, the high operation and maintenance cost in the network and the late opening of inter network operation and maintenance barriers, the commercial liquidity is insufficient and the online speed of new services slows down. Management mode course programming means that in terms of monitoring and management mode, the network elements in the network should support a variety of or customized management means to promote the three improvements of resource efficiency, energy efficiency and operation and maintenance efficiency, so as to achieve a closed-loop autonomous network system oriented to user experience.

We previously reported the application of 5g in 21 vertical industries. With the continuous popularization of 5g, the future demand of communication will be more clear. Relevant new businesses, new applications, new services and new materials are developing rapidly, and new technologies such as cloud computing, big data, blockchain and artificial intelligence are constantly integrating with communication technologies. These urgently need to constantly promote the design and research of 6G in combination with the latest changes and development trends. Although the assumption of 6G at this stage seems a little wild, the development speed of technology often exceeds people's expectations.

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