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1、1The Next-generation Protocol Stack-RANArchitecture,Protocol Stack and FunctionVersion 4.02Executive SummaryThe white paper firstly reviews the evolution of the communication protocolstack.Facing the future native AI characteristics of 6G network wisdom,analyze thepotential application scenarios and
2、 the needs of the network development.On thisbasis,thinking about the protocol stack architecture,functions,and evolution of thesmart endogenous network is proposed.The white paper hopes to arouse thecontinuous attention and thinking of the academic and industrial circles on theresearch of the 6G co
3、mmunication protocol stack architecture and functionenhancement direction,so as to truly achieve the deep integration of DOICT andpromote the comprehensive development of 6G.摘摘 要要本白皮书首先回顾了通信协议栈发展演进历程。面向未来6G智慧内生的特征分析潜在的应用场景以及网络自身发展的需求。在此基础上提出关于智慧内生网络的协议栈架构、功能、演进的思考。本白皮书希望引起学术界和产业界对6G通信协议栈架构与功能增强方向研究的
4、持续关注和思考,真正能够做到DOICT深度融合,促进6G全面发展。3Table of contentExecutive Summary.2摘要摘要.21.Introduction.42.Situation and challenge.62.1Review of the evolution of the protocol stack.62.2Future scenario analysis.92.3Technical challenges for 6G communication.283.The next generation protocol stack architecture.303.1P
5、otential features of future protocol stacks.303.2The architecture of the next-generation protocol stack.343.3Review on 3.0 protocol stack function.494.Next-generation protocol stack enhancement.514.1Space-Air-Ground-Sea Integrated Network.514.2Intelligence based RAN.544.3Adaptive protocol stack for
6、new architecture to support RAN nodes cooperation.564.4Integrated sensing and communication.615.Summary.65Reference.67Abbreviation.68Acknowledgement.6941.IntroductionThe white paper proposes 6G protocol stack views and thinking for 2030+,basedon the published versions such as The Next-generation Pro
7、tocol Stack over AirInterface 3.0 and The Next-generation Protocol Stack over Air Interface 2.0.Wehope to provide reference to study the 6G-oriented protocol stack architecture andfunctions for the industry.With the opening of the 5G commercial prelude in 2020,universities,researchinstitutions,indus
8、tries and other parties are gradually turning to the research of a newgeneration of mobile communication systems,and 6G has become a new focus.The6G Flagship of the University of Oulu in Finland took the lead in publishing theworlds first 6G white paper,and held the worlds first 6G summit in March 2
9、019.China is also actively developing the layout of 6G key technology.The universities,research institutes and various industries such as operators,manufacturer,cloudcomputing and Internet companies are cooperating closely to conduct research on6G-related topics.In addition,the companies such as Sam
10、sung,NTT DoCoMo,LGhave also begun 6G research and exploration.There are some white papers have studied the 6G vision and requirements,network architecture,and potential key technologies,which are of referencesignificance for the initial 6G research 1-5.At present,opinions on variousindustries of 6G
11、are letting a hundred schools of thought,but there are also somecommon opinions and trends in application scenarios,network characteristics,andkey technologies.In terms of vision and requirements,6G will build a new network of intelligentand efficient interconnection of humans,machines and things.6G
12、 will create aubiquitous,refined,real-time digital world.The credible and organically integrateddigital world accurately reflects and predicts the real state of the physical world in realtime,and finally realize the vision of digital twin,ubiquitous intelligence.In the5future,artificialintelligence(
13、AI)technologywillbeborninthemobilecommunication system and become the cornerstone of the current digital twin world,which means AI technology is native to 6G networks.In general,there are twoperspectives about the native AI 6G networks,the native-AI air interface and thenative-AI network architectur
14、e.In terms of key technologies,the native-AI air interface,that is,the deepintegration of AI,machine learning(ML)and other technologies,will breaks theexisting modular design framework of wireless air interface,realizes deep perceptionand efficient communication.Thereby the performance of native-AI
15、networks willsignificantly improve,such as efficiency,reliability,real-time and security,and realizethe self-operation and self-evolution networkIn terms of network architecture,the Native-AI network architecture uses theintegrated capabilities of communication,computing,and perception of networknod
16、es to enable 6G networks to natively support various AI applications and build anew network ecosystem.The 6G network architecture should have the characteristicsof native intelligence,native security,multi-domain integration,and integration ofcomputing and network.Among them,the endogenous intellige
17、nce is the embeddedAI capability of the 6G network,which realizes the endogenous intelligence of thearchitecture level.It can realize automated network operations,the combination ofnetwork and AI to provide communication and computing services,as well asintelligent perception,intelligent connection,
18、discovery,services,management andorchestration of DOICT integration,laying the foundation for the intelligentconnection of all things.In summary,6G and AI will gradually move towards full integration from theapplicationscenarios,keytechnologies,networkarchitecture,whichrequiresall-round innovation i
19、n theory and design.Native AI will be a key developmentconcept for the evolution from 5G to 6G,and the direction for promoting thesustainable development of 6G network62.Situation and challenge2.1Review of the evolution of the protocol stackThe mobile communication system has been developed from the
20、 first-generationmobile communication system(1G),and the fifth-generation mobile communicationsystem(5G)has also been commercialized in 2020.The network structure in the 3G era basically uses a three-layer architecture.Inthe 4G LTE era,the network adopts an all-IP architecture,and revolutionary chan
21、geshave taken place in network wireless transmission technology,air interface protocols,and system structure.The all-IP EPC(Evolved Packet Core,mobile core networkevolution)supports unified access of various technologies,and voice,text,and videoare all realized through the IP domain.Compared with th
22、e UTRAN system in the 3Gera,the 4G E-UTRAN system integrates NodeB and RNC into one network element,i.e.eNodeB.The eNodeBs use IP transmission and are logically connected to eachother through the X2 interface.Specifically,eNodeB refers to the elimination of thecentralized control of the RNC and the
23、addition of the physical layer,MAC layer,RRC layer,and scheduling,access control,bearer control,mobility management,andthe RRM measurement,based on the original functions of the NodeB of the UMTSsystem.In other words,the eNodeB realizes all the functions of the radio accessnetwork.Such a network str
24、ucture design greatly reduces the number of networkelements,so that the network deployment and the network maintenance are easier,and the network is flatter.The air interface protocol stack of the LTE system is divided into the user planeprotocol stack and the control plane protocol stack,and the us
25、er plane protocol stackof the LTE system is decomposed into different protocol sublayers.The user planeprotocol stack is similar to the UMTS system,including the physical(PHY)layer,themedium access control(MAC)layer,the radio link control(RLC)layer,and the7packet data convergence(PDCP)layer.These su
26、blayers are all terminated at theeNodeB in the network side.In downlink,the data is transmitted in the form of IPpackets,and the IP packets are processed by multiple protocol layers beforetransmitting via the air interface,as shown in Figure 1.Figure 1 4G LTE overall protocol stackThe control plane
27、protocol stack is shown in the following figure::Figure 2 Control plane protocol stack of 4G LTE 6The control plane protocol stack mainly includes the non-access layer(NAS),RRC,PDCP,RLC,MAC,and PHY layers.Among them,the PDCP layer providesencryption and integrity protection functions,the RLC and MAC
28、 layers provide thesame functions as in user plane.The RRC layer protocol terminates at the eNodeB inthe network side,and mainly provides functions such as broadcasting,paging,RRCconnection management,radio bearer(RB)control,mobility management,and UE8measurement reporting and control.The NAS layer
29、terminates at the MME innetwork side and mainly provides the functions including EPS bearer management,authentication,idle state mobility management,paging,security control,etc.In the 5G era,the SBA architecture of the 5G core network is constructed.TheSBA architecture includes modularization of net
30、work capabilities,the service-orientedinterfaces,and the C-plane and U-plane separation.The mobile communicationnetwork has a closer relationship with business,and supports network functionvirtualization and slicing technology.The introduction of the CU/DU separation inwireless side can better reali
31、ze flexible network deployment.The mobile network isno longer a solidification,but can be dynamically created and reconfigured so as toquickly support a variety of new business applications.The 5G air interface protocol stack is mainly divided into three layers and twosides.The three layers are the
32、network layer(L3),the data link layer(L2),and thephysical layer(L1).The network layer is the user of air interface services,namelyRRC signaling and user plane data;the data link layer(L2)distinguishes and labelsdifferent L3 data and provides different services;the physical layer(L1)provides theservi
33、ce of the the wireless resource and physical layer processing to the upper layerdata transmission.Figure 3 NR overall protocol stack 7From the control plane perspective,the structure is exact same in 4G and 5G.From the user perspective,5G has the same structure as 4G except for the addition ofa new
34、SDAP protocol layer.In 5G QoS framework,in order to provide the refinedgranularity of the QoS requirement,the basic transmission granularity in the core9network side is refined from the E-RAB in 4G to the QoS Flow;but in RAN side,5Gstill uses the radio bearer concept in 4G.Therefore,in RAN side,the
35、SDAP layer isintroduced to realize the mapping between DRB and QoS Flow.Figure 4 NR Control Plane Protocol StackFigure 5 NR User Plane Protocol Stack 782.2Future scenario analysis2.2.1 Space-Air-Ground-Sea Integrated CommunicationThe construction of terrestrial mobile communication networks is limit
36、ed byconstraints such as infrastructure cost and technical realization.Indeed,the networkcoverage accounts for only about 20%of the total land area at present.More than95%of marine areas without mobile radio connectivity,which is far from reaching theconstruction of a global mobile communication net
37、work.Realizing the full coverage10of Space-Air-Ground-Sea(SAGS)integration will be the goal of future 6G networkcommunications,and its performance metrics work capacity,energy efficiency,delay and reliability will also be 10 to 100 times higher than 5G networks.The SAGSintegrated communication syste
38、m includes space-based(various types of satellites,etc.),air-based(unmanned aerial vehicles,airships,airplanes,and other high altitudeplatforms),ground-based(cellular,non-cellular network facilities),and sea-based(seasurface and deep-sea communication equipment).The system supports a variety ofwirel
39、ess access methods in different application scenarios,uses all available radiospectrum resources to achieve Internet access for many users worldwide,and providesfast and consistent communication services.It is envisaged that system will alsointegrate precise positioning,navigation,remote sensing,mon
40、itoring,and otherfunctions to support regional economic and social development.Figure 6.The architecture of the Space-Air-Ground-Sea integrated networkFrom the perspective of application scenarios,the inland areas are mainlycovered by the terrestrial network,which gives full play to the advantages o
41、f highspeed and capacity.UAV communication can improve the service capacity of denselypopulated urban areas with highly dynamic data traffic loads and help to reduce the11network burden on the ground.Satellites or high-altitude platforms can provideeffective communication solutions in remote areas,m
42、arine economy,infrastructure,aviation mobility,and post-disaster emergency support,which can give full play to theadvantages of wide coverage,free from terrain constraints,flexible deployment.According to statistics,more than 70%of geographic space in the world involvesmore than 3 billion people wit
43、hout access to the Internet.The coordination ofterrestrial and non-terrestrial network is an important means to solve the problem ofthe population digital divide.Moreover,there are 38 million flights worldwide eachyear with 4.4 billion passengers,and 80,000 freighters with 38 million voyages,all ofw
44、hich are target customers of SAGS connection services and have huge market space.2.2.2 HolographyHolography is a technique that is used to display objects or scenes in threedimensions.Holographictelepresenceisbecomingarealitywiththerapiddevelopment in the supporting technologies:high-resolution imag
45、ing and sensing,wearabledisplays,mobilerobotsanddrones,specializedprocessors,andnext-generation wireless networks.Holographic telepresence may be achievedthrough real-time capture,transmission,and rendering of a 3D holographic data on alocal holographic display.Current commercially available 3D disp
46、lay product is based on stereoscopicprinciple,which only utilizes human binocular depth perception to create 3D illusion.3D holographic display has been considered as an ultimate glasses-free true-3Ddisplay technology because it can provide all depth cues and eliminate eye fatigue orvisual discomfor
47、t.It has been considered as an alternative to current stereoscopicdisplays on the market.As holographic display technology has made significant advances,holographicapplications are becoming a reality.The real-time,3D interactive applications willpermeate future life:1)tele conference:holographic tel
48、epresence will project remote12participants as a hologram to local meeting;2)Remote troubleshooting and repairapplications:allow technicians to interact with holographic renderings of artefactslocated in a remote location;3)Training and education:provide users the ability todynamically interact from
49、 remote with ultra-realistic holographic objects for teachingpurposes;4)tele-surgery:hologram feedback audio-visual and instruction to surgeonor robot;5)immersive entertainment,gaming,sports,and much moreIn a hologram,the same image is captured from different viewpoints,tilts,andangles.Depending on
50、the position of the viewer relative to the image,a different“field”in an array of images is seen,with each image depicting the same“object”or“scene”from a slightly different viewpoint.Streaming holographic videos overnetwork to the display systems has become an important research topic.Holographic-t
51、ype communication(HTC)will enable the ability to transmit andstream holographic data from remote locations across a network.Besides the requirements of low latency and high reliability,HTC service has itsspecific KPIsUltra-high bandwidth:Required bandwidth may start from roughly 1 Gbps andincrease u
52、p to 1 Tbps but depends heavily on encoding and trade-offs regardingbandwidth and compute for optimization schemes.Strict synchronization:At 60 frames/second,latency variation across channelsshould not exceed 7 ms(duration for half a frame).Support for concurrent flows.Depending on point cloud and i
53、mage arraydimensions,on the order of 1000 concurrent flows may need to be supported.And thenetwork should be capable of prioritizing streams based on dynamic and varyingcriteria(related to viewing position and user focus)Streaming a hologram over the network means to capture,render,and stream atarge
54、t object.Capturing is performed by a camera array outputting images of thetarget object from multiple angles and views.The camera feeds need to be merged,13rendered into a hologram,and encoded.The hologram is streamed across the network.On the receiver side,a client receives the stream,decodes it,an
55、d renders it for aholographic display or beamer.Volumetric media is highly compressed,and the volume is independent ofnumber of angles or tilts.Even with compression,holograms will require massivebandwidth.To cope with it,the current tendency is to come up with clever techniquesaiming to reduce data
56、 that needs to be transmitted by means of eliminating portions ofthe content that will go unnoticed by a user.For example,some areas may beobstructed from the users viewpoint,or some angles may not come into view basedon the users position.Schemes that take advantage of these aspects can dynamically
57、adapt which parts of the contents to stream,and at what quality,at any given time.The effectiveness depends on the ability to predict the users movement,thus rapidlyadapting the data as needed.This is referred to as the“user interactivity challenge”,and will enforce not only ultra-high bandwidth but
58、 also ultra-low latency(to ensureinteractivity with the content).In addition,perfect synchronization of concurrentflows will be needed.Contrary to other types of multimedia services(e.g.,UHDstreaming),the interactivity challenge of immersive HTC will require ultra-lowlatency even if dealing with pre
59、recorded content that does not involve real-timeinteraction with a remote party,as the user still interacts with the content simply byvirtue of changing viewing angle and position.In summary,handling HTC traffic,the network needs to manage a massivenumber of synchronized streams originating from eit
60、her different sensors,an object atdifferent angles,or a processed volumetric fusion.Traditional network is notcompetent to the specific requirements on ultra-high bandwidth(up to 1Tbps),ultra-low delay(1ms round-triplatencyover long distance),streambundlesynchronization.HTC-enabled network will desi
61、gn for distributed control intelligence,network slicing,stream prediction and prioritization,etc.From protocol stack aspect,cross-layer optimization,flexible protocol layer deployment for multi-stream can be abasic objective.142.2.3 Digital twin networkDigital twin is the real-time mirror image of p
62、hysical entities in the digital world,with the characteristics of real-time interaction,real-time iterative operation andoptimization.Based on the digital twin technology,the network can preprocess thedata and predict the operation direction of the future network in the network virtualspace in advan
63、ce.That is to say,the network fault can be checked and solved beforethe network fault occurs,avoiding the occurrence of the fault,so as to realize theautomatic network optimization and achieve the effect of preventive cure and zeromaintenance.In the digital twin network,some new functions,new servic
64、es and evenoptimization means can be verified in advance,and the implementation scheme canbe iteratively optimized.However,traditional network optimization and innovationoften need to be tried directly on the real network,which may have an impact andinterference on the existing network.Digital twin
65、network is a network system with physical network entity andvirtual twin,which can be interactively mapped in real time.In this system,variousnetwork management and applications can use the virtual twin constructed by digitaltwin technology to efficiently analyze,diagnose,simulate and control the ph
66、ysicalnetwork based on data and models.The 6G digital twin system provides a basic operating environment for 6G nativeintelligence,which provides basic support for AI-related processing and calculations,and simplifies the operating load and complexity of physical network.In other words,the 6G digita
67、l twin system and the native intelligence system together form a series ofonline operations for the operation,maintenance,application-oriented controlcalculation of the physical network,and become the brain of the physical network,directing each part of the physical network to complete the protocol
68、or the servicecapability required by the operator.As shown in Figure 7,the protocol stack scheme of native intelligence and15digital twin can be implemented by introducing the intelligent function body anddigital twin function body into different protocol stack functions of operation andmaintenance
69、system,core network,transmission network and access network.Figure 7Aprotocol stack function of native intelligence and digital twinThe OAM system includes the following sub-functions:1.Measurementprocessing function,which processes the measurement information reported by thenetwork side and the ter
70、minal side,including the measurement information reportedby the distributed intelligent function and the distributed digital twin based on the16network side and the terminal side,as well as the large-time scale information directlyreported by the network side and terminal side required by OAM.2.Data
71、 storagefunction,which cleans,accumulates,calculates,smoothes and combines the receivedmeasurement information for storage;3.AI processing function,which trains and runsAI model based on measurement information and stored data;4.O-API terminationfunction,responsible for the interface processing betw
72、een OAM and each networkelement.The DT function system of the OAM system is based on the abovesub-functions,and generates the overall digital twin mirror image of each networkelement and terminal.This digital twin mirror image is a large-scale mirror image,which mainly reflects the digital mirror im
73、ages of different network element levelsand the entire terminal,and depicts the overall characteristics of the network elementor terminal for management through OAM system.Based on the DT function,OAMperforms cell management,UE management,feature management,software versionmanagement,traffic managem
74、ent,etc.The above management functions are based onthe digital twin of the network element or terminal provided by the DT system tocarry out large-scale or large-granularity management such as coordination,control,and policy transmission at the cell level,terminal level,or service level.Digital twin
75、 function mirroring is performed for L3UP,RRM,MAC and PHY inthe access network.L3 DT in RAN is responsible for online simulation of theprocessing of data received and sent by the access network,and generates airinterface-oriented transmission strategies(data analytics and QoS analytics)throughthe pa
76、cket header information,payload length,cache status,etc.of each packet.DT inRRM is responsible for the online simulation of radio resource management,andgenerates control related to handover,flow control,QoS,etc.The edge controlunction realizes the function configuration of DUs driven by AI,selectio
77、n andmanagement of different DUs,etc.DT in MAC layer is responsible for generatingcorresponding online simulation for different MAC functions,including uplinkorchestrationcorrespondingtoMACULscheduler,downlinkorchestrationcorresponding to MAC DL scheduler,and air interface flow control(data flow CTR
78、L)17corresponding to data packet transmission and reception(MAC PDU).DT in PHYlayer is responsible for online simulation of physical channel processing,includingchannel estimation,channel model adaptation and selection,etc.OAM system communicates with the interfaces(open API)of various systemsfor in
79、formation exchange.Under the unified coordination of OAM,the upstream anddownstream data processing is completed between various functional entities.Forexample,when a UE applies for a new service,the OAM system generates interfacesfor the overall requirements of the core network,transmission network
80、 and accessnetwork,as well as the division of work of each network element according to theservice characteristics applied by the UE and the characteristics of this type of serviceaccumulated during the system operation,letting the transmission network provideproper bandwidth and corresponding trans
81、mission QoS guarantee and the corenetwork and wireless network consider the QoS guarantee characteristics whenestablishing end-to-end bearer.Based on this requirement,the AI and DT systems ofCN,TN and RAN respectively produce the required resource support in combinationwith their actual operation.If
82、 they cannot be satisfied,the information need to bereported to OAM in time.The intelligent control process of network internal integrated service control is asfollows:Figure 8 service control interaction flow chart of native intelligence and digitaltwin18Figure 8 shows the interaction process of na
83、tive intelligence and digital twin:1.CN,TN,CU and DU respectively perform service control at their respectivelevels.CN generates a demand for service control when a new user performs serviceapplication or load balancing processing.TN monitors the quality of data packets received or transmitted on ea
84、chtransmission node(such as router)in TN network in the process of receiving andtransmitting the carried service data packets(such as packet loss rate,data cacheoccupancy rate,packet detention delay,etc.),resulting in the demand for servicecontrol.The CU monitors the quality of service data packets
85、received and transmitted byeach user on the wireless link,including the data buffer occupancy rate of L3,theratio of data packets to be retransmitted,etc.,resulting in the demand for servicecontrol.DU monitors the reception and transmission quality of each data packet on theair interface,including H
86、ARQ retransmission,block error rate(BLER),the ratio oflarge data packets sent by segmentation,the ratio of small data packets sent byconcatenation into large data packets,the times of data packets moved betweeninternal buffers,the applicability of dynamic QoS indicators in air interface receptionand
87、 transmission,etc.If it needs to be initiated through the network operation and maintenance pipeline,an application shall be initiated to the OAM system.CN,TN,CU and DU send running status report to OAM system,including themonitoring information received and transmitted by the whole end-to-end servi
88、ce(application layer to application layer)on CN/TN/CU/DU,the running status of eachuser in the network,the transmission quality assurance of transmission network datareceiving and transmitting,the running status information of CN/TN/CU/DU itself orAI/DT software body,etc.The information about the us
89、er or service operation statuscan be the information data directly reported by the relevant function body,or the19reported information data after being processed by the relevant AI function body orDT function body on CN/TN/CU/DU according to the requirements defined with theOAM system interface.3.Th
90、e OAM system monitors the data volume of the whole network service.If itis necessary to initiate end-to-end transmission channel control,it will initiate thecontrol policy update process.4/5/6/7.OAMsendsservicecontrolpolicyupdatetoCN/TN/CU/DUrespectively.For CN,send end-to-end QoS policy update(4.En
91、d-to-end QoS control policyupdate),and CN can adjust the corresponding QoS parameters for the specifiedservice according to the policy,and generate a new QoS indication.For TN,the transmission bandwidth control strategy is updated,includingincreasing or decreasing the(logical)bandwidth of the transm
92、ission channel,adjusting the data transmission service quality assurance parameters of eachtransmission node,etc.For CU,the flow control strategy for data reception and transmission includesthe flow state of received CN data,the flow state of received and transmitted data toDU,etc.For DU,the air int
93、erface QoS control strategy is updated,including the MAClayer formulating targeted HARQ mechanism for the bearer of corresponding types ofservices,air interface transmission and feedback mechanism,and the arrangement ofphysical resources(physical channel,and corresponding coding/decoding,modulation/
94、demodulation,power,control companion channel,etc.).During the operation of the system,OAM system triggers the control flowbetween CN and base station according to the results ofAI and DT inspection.8.The OAM system sends the relevant updates of the AI model,strategy or DTsystem to the CN;9.Triggered
95、 by the OAM system,CN generates NAS(non Access Stratum)signaling and AS(Access Stratum)configuration signaling to configure the base20station(CU/DU)respectively.10/11.The base station sends a confirmation message to the CN,and the CNgenerates a corresponding completion confirmation message to the OA
96、M system.2.2.4 New Ultra-Dense NetworkIn 5G and before generations,Ultra-Dense Network(UDN)aimed to crowdedscenarios,such as shopping mall,railway station,airport,stadium with big show,etc.Connection density is defined as the total number of devices fulfilling a specificquality of service(QoS)per un
97、it area(per km2)with 99%grade of service(GoS).In5G,the requirement of connection density is 1 000 000 device/km2in urbanenvironment.The data traffic and the numbers of connected things will increase substantiallyfor 6G.Device density may grow to hundred(s)of devices per cubic meter.This posesstringe
98、nt requirements on area or spatial spectral efficiency and the requiredfrequency bands for connectivity.The technical KPI enhancements may potentiallybring deeper immersion and interaction for users(e.g.holographic interaction,tactileInternet etc.),even in hitherto underserved areas.Such capabilitie
99、s may add value toremote service delivery(e.g.health,education etc.)in ways that far exceed legacymobile technologies.Besides traditional use cases in UDN,use cases in new UDNcan include Ultra-dense devices in moving vehicles,Multi-sensory extended reality,and Industrial automation and robotics,etc.
100、Ultra-dense devices in moving vehicles:the moving vehicles can be trains,buses and even civil aircrafts.Here the infrastructure,vehicles,passengers,and goodsare seamlessly connected with high data rates.With the explosion of devices(including sensors and user application terminals)and diverse applic
101、ations,thedevices density and capacity requirements in the moving vehicles form a new UDNscenario.Multi-sensoryextendedreality:Augmented,mixed,andvirtualreality21(AR/MR/VR)applications,capturing multi-sensory inputs and providing real-timeuser interaction are considered under this use case.Extremely
102、 high per-user data ratesin the Gbps range and exceptionally low latencies are required to deliver a fullyimmersive experience.Remote connectivity and interaction powered by holographiccommunications,along with all human sensory input information,will further pushthe data rate and latency targets.Mu
103、ltipleview cameras used for holographiccommunications will require data rates in the order of terabits per second.With themultiple sensors,the device density can be large even in the scenario with lowpopulation desity.Industrialautomationandrobotics:Industry4.0envisionsadigitaltransformation of manu
104、facturing industries and processes through cyber-physicalsystems,internet-of-things(IoT)networks,cloudcomputing,andartificialintelligence.In order to achieve highprecision manufacturing,automatic controlsystems,and communication technologies are utilized in the industrial processes.Theemerging need
105、for the ultra-dense deployment of industrial IoT devices will require3D connectivity supporting up to 10 connections per m3.In summary,in 6G,the number of devices connected to the wireless network willbe much larger than the number of population,and the deployment of devices can bedifferent to the p
106、opulation distribution.Some distinct characteristics of new UDN canbe:1)the new UDN scenarios can be extended to any areas,and traditionalconnection density on urban/rural may not be applicable;2)the definition ofconnection density will be extended from area to spatial;3)the coverage of new UDNcan b
107、e dynamically.2.2.5 Integrated sensing and communicationInwirelesscommunication,electromagneticwavespropagatefromthetransmitter to the receiver through space to transfer information,while the receivedsignal also carries environmental information.Therefore,the communication process22has the sensing c
108、apability.There are a huge number of base stations in the world now,e.g.the number of base stations in China is on the order of one million.If the basestations and terminals can be used for sensing,the sensing range will be greatlyexpanded,as well as the sensing applications.The integration of sensi
109、ng andcommunication is one of the most effective means to build a digital twin world.The sensing and communication integrated system can provide location,direction,distance,and speed of the sensing target,or target detecting,tracking,ranging,imaging,etc.These sensing services can be used to improve
110、the performanceof wireless communications and the quality of life and production.According to thefunction and content of sensing,it can be divided into macro sensing and refinedsensing.Macro sensing generally includes weather,air quality,traffic flow,peopleflow,environmental reconstruction,and targe
111、t tracking.It can be used in scenariossuch as meteorology,life services,intelligent transportation,smart cities,and networkplanning and network optimization.Refined sensing generally includes motionrecognition,facial expression recognition,breathing monitoring,heartbeat monitoringand material detect
112、ion,etc.It can be used in scenarios such as intelligent interaction,medical health,and security checks.2.2.6 Native DeterminacyThe deterministic network was originally proposed to solve the problem that thebest-effort mechanism of the packet-switched network cannot guarantee the delayand jitter requ
113、irements of multiple services.Deterministic network technologyincludes IEEE TSN,IETF DetNet,and DIP,but it is limited to wired networks.Withthe continuous improvement of mobile network performance,vertical industrybusinesses have gradually begun to use wireless networks to achieve flexibility,largeb
114、andwidth,and low latency.5G network achieve determinacy by integrating withTSN to guarantee the performance of industrial time-sensitive services.With thediversification and differentiation of services in 6G,there will be a higher demand fordeterminacy.The realization of native determinacy in the mo
115、bile network will become23a very important feature.In the future,the diversified scenarios and differentiated network requirements of6G will have more stringent requirements for determinacy,not only including theexisting deterministic delay and jitter,but also deterministic bandwidth anddeterministi
116、cpositioning,reliability,availabilityandcertaintyofclocksynchronization.Typical services include cloud AR/VR,holographic communication,smart industry,etc.The existing deterministic mechanism for mobile networks onlyuses the entire network as a transparent bridge,which cannot truly sense servicerequi
117、rements and reuse the technical system of URLLC.In 6G mobile network,including the RAN side,in order to meet deterministic service needs,it needs to havenative deterministic capabilities which can intelligently sense business needs,performprecise time synchronization and real-time and dynamic alloca
118、tion of RAN resources.Besides,6G will not only achieve native determinacy but also adapt to externalvertical industry protocols to guarantee the needs of deterministic scenarios in everyaspects.2.2.7 Intelligent networkAs the rapid development of future network on 2B/2C service,network designand mai
119、ntenance will become very complicated,its more and more difficult to usethetraditionalcommunicationnetworkoptimizationmethodtofulfilltherequirements of future network.To break through the bottleneck for traditionalcommunication network,the fusion between AI/ML technology and traditionalcommunication
120、 network seems to be one of the trends of the future networkdevelopment.Comparedwiththetraditionalcommunicationnetwork,AI/MLenabledintelligent network can use diverse information including inputs from environment,the available resources from the network,the services provided by the network,theservic
121、e object and so on.These inputs are valuable to improve the performance of24communication network and the target is to create a self-organized and self-optimizedcommunication network in the future.Intelligent network not only emphasizes the intelligence empowered networkoptimization,but also pays at
122、tention on the role of terminals in the intelligent network.In traditional communication system,terminals usually passively accept networkmanagement.When it comes to intelligence empowered network,we believeterminals can actively participate in the management of the entire intelligent networkthrough
123、 real-time/near-real-time interaction with the network,intelligent network canbetter provide personalized services for terminals.2.2.8 User Native NetworkingIn the future 6G era,the user experiences in communication,Sensing,computing,and intelligence will be greatly boosted,and the degree of persona
124、lized services willbe fully satisfied.The new 6G networking should not only support user-centriccapabilities in terms of radio signals,resources,functions,and services,but alsosupport the new architecture and networking mechanism to meet the requirements ofusers for self-development,self-initiative,
125、customization,privacy,and personalization.In the traditional IMT mobile unicast system,each user and terminal areconsidered as independent serving object entities.Each terminal establishes itsindependent communication connections with the network through random access,core network authentication,ses
126、sion establishment,and radio access network resourceallocation processes etc.The logical functions of UE are obviously lower and lesspowerful than those of the network side,which seems extremely asymmetric andunfair,and UEs are relatively in passive and served roles.With the continuousstatus promoti
127、on of 6G users and the continuous improvement of UE capabilities,thelogical function and status of UE in the new 6G system will be gradually improvedfrom passive to active role,from simply being served to providing services.In the user native networking scenario,several UEs can establish a subnetwor
128、k25of UEs locally based on specific subscription requirements,and then any member UEin the subnetwork can access the 6G network through one or more primary UEs as theaccess interfaces.The UEs in the sub network can directly or indirectly communicatewith the 6G network.Such application scenario inclu
129、des:On a user,several wearablecommunication devices can be connected to the 6G network together at the same time,multiple user groups associated with the same services can be connected to thenetworkatthesametime,andseveraldistributedcommunicationdevicescollaborating in the same tasks can be connecte
130、d to the network at the same time.2.2.9 Multi-parties Native NetworkingIn the future 6G era,the new 6G network should be able to provide morepowerful,comprehensive and intelligent services in the traditional ToC and ToB fields.In addition,it should be able to differentiate serving subject groups in
131、moregranularities and make full use of certain features of these serving subject groups,inorder to provide services in more economical and customized manner.Each servingsubject group can be identified and effectively served by new 6G networks due to itsnatural association e.g.in physical distributio
132、n,user profile,service requirements orsocialrelations,thusformingmoretargetedclassificationandhierarchicaloptimization.In the traditional IMT mobile systems,the network topology is relatively simple,focusing on the centralized cell topology with more emphasis on wireless coveragecontinuity.Network p
133、lanning and optimization of mobile operators used to care lessabout different levels of serving subject groups.They could only customize and adaptnetworking by network slicing,parameter set optimization,and other lower-levelmeans,which results in poor performances in terms of coverage and costs.With
134、 theintroduction of more 6G networking modes,such as de-cellularizaiton,distributedsubnet,multi-hop relay,and drone/satellite aiming for large coverage,6G is expectedto further optimize the overall wireless coverage solution.26In the multi-parties native networking scenarios,new 6G network can be di
135、videdinto different levels of serving subject groups in accordance with their associationcharacteristics of different granularities and serving objects.Taking advantages ofthose features,the new 6G networking can optimize the networks to provide morecustomized classified services.In addition to abov
136、e ToC and ToB,such applicationscenario also includes:ToH which is oriented to family life,ToG which is oriented togovernment office,ToI which is oriented to industrial production and ToS which isoriented to social governance.2.2.10 The energy and cost-prioritized networking mechanismsIn the future 6
137、G era,new 6G network must not only evolve towards higher KPIsand ultimate system performances,but should also support energy and cost-prioritizedarchitecture and networking mechanisms.The vision of a new 6G networkarchitecture has two basic principles:Compatibility and simplicity.Therefore,the new6G
138、 network should be compatible with some simplified,low-energy-consumption,and low-cost coverage wireless solutions to meet the basic service requirements inspecific scenarios.This is very important to support Chinas dual-carbon and greensustainable development strategies in the future.During the evo
139、lution of traditional IMT mobile systems,each generation ofsystems have been increasingly seeking better KPIs.The system becomes more andmore complicated,and the system kernel is becoming much heavier.The protocolinterface specifications turnsto be more complicated,while systemenergyconsumption and
140、cost turns to be higher.Despite the reduction in energy consumptionand costs by using AI and various narrowband technologies,the overall situationremains grim and unsustainable.If such trend would continue,the successfulcommercial usage of new 6G networks will face great non-technical bottlenecks an
141、dobstacles.The energy and cost-prioritized networking means that,on the premise of27satisfying the basic service requirements in specific scenarios,the new 6G networkshould be compatible with those simpler,lower energy consumption and lower costwireless solutions.In addition,when the network traffic
142、 amount is zero,the systemenergy consumption and operation cost will tend to be zero as well,i.e.Scale-to-zero.Such application scenarios include special vertical industry coverage scenarios,massive concurrent transmission scenarios of small data packets in broadband systems,and narrowband services
143、in narrowband systems.2.2.11 The multi-band aggregated networkingIn the future 6G era,new 6G networks will face more brand-new scenarios andservices,and the technologies of integrating and utilizing higher frequency band,multi-band,andfull-bandresources(hereinafterreferredtoasmulti-bandtechnologies)
144、will be one of the important means to overcome the above challenges.The multi-band technology can achieve more efficient aggregation of a wider rangeor discrete wireless spectrum resources.In addition,the physical advantages of eachsub-band can be utilized to achieve complementary performances.This
145、can supportnew 6G services,for example,holographic communication,digital twin,to improvenetwork resource utilization,to reduce cost and increase efficiency.In the traditional IMT mobile systems,due to the limited cellular topology mode,the joint usage of multi-frequency resources is static and segme
146、nted.Althoughexisting mainstream technologies such as CA and DC have been applied,theirefficiency and flexibility have been proved to be not so satisfactory in practice.Forexample,CA regards each component carrier as an independent cell,and implementsresource maintenance,system information message p
147、rocessing,and synchronizationindependently,which causes redundancy and waste of scheduler resources.Thehandover delay between PCell and SCells is long,and the benefits of carrieraggregation in idle mode need to be improved.In a multi-band aggregated network,air interface carrier resources will be de
148、eply28virtualized and cloudified,and will no longer be used in traditional static and fixedmanner.Radio carrier resources,corresponding to RF carriers,can be decoupled fromand mapped to baseband carriers,and each physical channel can flexibly aggregateand utilize lower-layer multi-band resources.Suc
149、h usage scenario includes:Operatorswith a large number of discrete spectrum resources,carrier resources shared bymultiple operators or multiple RATs,and so on.2.2.12 Technical challenges for 6G communicationFrom the law of network reform,there are three main driving forces.First,withthe continuous e
150、mergence of new services,new applications and new requirements,the requirements for network capability are also more stringent.Typical applicationscenarios in the 6G era,such as digital twin,holographic communication,super-powered transportation,integration of communication and sensing,nativeintelli
151、gence,and integration of ground,air,space and sea,require the network to havebetter service capability.The requirements of performance indicators in the 6G eramay include extreme user experience rate,ultra-low latency,ultra-high data rate,ultra-high security,integrated coverage of ground,air,space a
152、nd sea,etc.Second,thefuture 6G network needs to face up to the problems and challenges faced by thecurrent network,such as high energy consumption,high cost and low operation andmaintenance efficiency.These problems should be fundamentally changed whendesigning the future network and protocol stack.
153、Third,driven by new technologies,such as cloud computing,big data and AI technology,6G network architecture shouldinclude and make rational use of new technologies,and new technologies shouldpromote the development of 6G network architecture in a more efficient andlower-cost direction.The difficulti
154、es and challenges that 6G network and protocol stack may face inthe evolution process may come from the following aspects.The first aspect is that the solidified protocol structure has led to a ceiling of29network performance.For 5G wireless network,the protocol structure is hierarchical,and all ser
155、vices need to be processed by layers.However,the processing of each layerwill introduce a specific delay,resulting in the delay bottleneck of servicetransmission.Moreover,a large number of signaling interactions are required toimplement a specific service network,which also leads to a certain consum
156、ption ofnetwork resource.Therefore,the design of 6G network needs to consider thelightweight network architecture,so as to simplify the protocol stack structure andenhance the function as much as possible.The second aspect is how to transform AI ability from plug-in design to nativedesign.For exampl
157、e,there are already many schemes that use AI and big data toimplement intelligent air interface,resource management,slicing and intelligentnetwork operation and maintenance.However,since the initial network design did notfully consider the support for these functions,it is difficult to make majorbre
158、akthroughs and innovations from the entire network structure.Patch-based AIfunction enhancement is difficult to meet various service requirements of 6G supportfor the whole society,the whole industry and the whole ecology.Instead,it leads tomore complex network scale and functions.The third aspect i
159、s that the single network structure leads to high cost and highpower consumption.For example,the basic deployment of 5G is a full-functiondeployment based on the base station,that is,a full-function base station is configuredwherever it needs to be covered,which will inevitably lead to higher networ
160、kconstruction cost.In the 6G era,open and customized capabilities are essential.Weshould provide industry customers with more agile and friendly services through openinterfaces and flexible network deployment,so as to better meet customerson-demand network configuration and customized applications.T
161、he fourth aspect is that the future network needs to have a unified accesscontrol management technology.The future 6G network is integrated with ground,air,space and sea access,with the ability to support various access modes.Therefore,6G30network should be a lightweight network,which can ensure rel
162、iable mobilitymanagement and fast service access through unified signaling coverage,ensure usersservice experience and delay,and dynamically load data access through plug and play.Patched and incremental function enhancements are difficult to meet the servicerequirements of 6G to support all scenari
163、os,but instead lead to more rigid networkfunctions and more complex network structure.In the early stage of 6G research,building a new protocol stack with powerful functions and native intelligence,designing a network architecture with deep integration of computing power,data andnetwork,and building
164、 a multi-dimensional,full-scene access and multi-networksymbiotic integration system will be the key to 6G research.3.The next generation protocol stack architecture3.1Potential features of future protocol stacksThroughout the history of the development of mobile communication,thenetwork form has be
165、en constantly changing and evolving with the development ofmobile communication technologies and service requirements.From 2G voice era,3Gtext era,4G data era to 5G Internet of Everything era,the network architecture andprotocol stack function are also evolving as the requirements change.Considering
166、 theubiquitous connection of all scenarios and the introduction of various new services,the diversification of 6G services and application scenarios further aggravates thecomplexity of the network.In order to solve this problem,6G network may have thecharacteristics of on-demand fulfillment,lite,sof
167、t,native intelligence,native securityand digital twin.The future 6G society will face more new services,new scenarios and new userrequirements,which will tend to be diversified and personalized.Therefore,6Gnetwork should perform on-demand function deployment,parameter configuration31and resource con
168、figuration,which requires the network to have dynamic fine-grainedservice capability supply to provide users with personalized on-demand fulfillment.LiteThe 6G network will face the challenges of new differentiated scenarios such asubiquitous network connection and integration of ground,air and spac
169、e in the future,and the existing protocol architecture will inevitably lead to increased complexity.The 6G network needs a lite and unified protocol system to reduce the logicalconstraints when supporting various services.Through the integrated communicationprotocol and communication access technolo
170、gy,the unified protocol architecture,function design and process framework are adopted to realize the unified access of avariety of air interface technologies,so that new network functions and services canbe introduced in a plug-and-play manner,achieving the purpose of unifying thenetwork protocol s
171、ystem.The lite design greatly reduces the number of protocols andsignaling interactions required for 6G network communication,thereby reducing thecomplexity of the network,while making it have the characteristics of powerfulfunction,toughness,security and reliability.SoftThe future network will be a
172、n end-to-end software-definable network that canrealize rapid service deployment,automatic update and iteration of functionalsoftware versions,and self-evolution of network functions.With soft features,thenetwork can realize end-to-end micro servitization functions,support independentnetwork element
173、 functions,support elastic scaling and evolution of services,as wellas efficient iteration and flexible deployment of the network,so as to truly realizenetwork automation and intelligence.NativeAIThe AI capability of the network in the 6G era will be an native capability thattruly realizes internal
174、and external coordination.Internal AI can realize the on-demandsupply of network capabilities and support distributed AI.And it can introduce the32capabilities of external AI into the network through the intelligent platform to providecorresponding new services and support.It is also possible to sha
175、re external data withthe network,bringing further improvement of data efficiency and enrichment of datacontent.At the same time,the networks own data and capabilities can also be openedto external partners as a capability to provide services and corresponding support forthe outside world.Modular pro
176、cessing is one of the key features of traditional protocol stack,thefunctions among different protocol sub-layer are relatively independent.With thecontinuous development of intelligent network,the future protocol stack should havethe characteristics of intelligence,compare to traditional protocol s
177、tack structure,intelligence empowered protocol stack in the future emphasis on the coordinationbetween protocol stack modules and joint optimization can be easily achieved for anyservice and any procedure.Digital twinThe fifth characteristic is by digital twin.A dual world architecture will beformed
178、 through digital twin,that is,a real physical world and a virtual world as anextension of the real world,corresponding to the needs of the real world,and realizingthe mapping of the real world in the virtual world.Through digital twin,the networkcan monitor and predict the status of each network ele
179、ment,base station and even userservice in real time,so as to reserve resources in advance or avoid accidents,toimprove the efficiency of the whole network operation and service.At the same time,some new functions can be verified in advance to accelerate the introduction of newfunctions and realize t
180、he self-evolution of the network.Native securityNative security is also a very important feature for 6G network.After thenetwork has strong ability of native intelligence,AI will become an engine of 6Gsecurity in the future.Driven by AI,the network can efficiently realize the intelligentconsensus of
181、 information,the intelligent defense against attacks,the self-immunity of33the network and the self-evolution of network security strategies.Reconfigurable unified wireless interface designDesign the protocol stack in the unified approach.By flexibly configuring thefunctions of the unified protocol
182、stack,we can obtain various protocol stacks suitablefor scenarios with different traffic characteristics.In this way,one unified protocolstack can satisfy different requirement for the wireless network,e.g.unified design forD2D air interface and the cellular air interface.On the other hand,5G only r
183、ealized the virtualization of 5G core network,but itis possible to achieve the end-to-end network virtualization for 6G.Thereconfigurable unified wireless interface design is beneficial to realize wirelessaccess network virtualization,and enable the end-to-end network virtualizationfurthermore.Nativ
184、e well-matched with vertical industry communication protocols5Gintroducedadditionalenhancementtomatchtheverticalindustrycommunication protocols after the first version of protocol stack is completed,such asEthernet header compression function for industrial Internet.6G can take theadaptation for ver
185、tical industry communication protocols into account at the initialstage of wireless protocol stack design.Moreover,the maximum data length and themaximum number of radio bear supported by the protocol may need be extended.Flexible network with higher frequency bands6G will move to higher bands.Multi
186、ple-hop radio access network is a possibleway to extend the network coverage at higher bands.The radio access networkprotocol and interface need support various data relaying requirements.Differentkinds of relay nodes,e.g.IAB node,sidelink UE relay,smart repeater,and relayprotocol architectures are
187、designed in 5G,but still not deployed widely.Consideringthe costs of 6G deployment at higher bands,it is likely to have large-scale deploymentof multiple-hop radio network.34On the other hand,in order to cope with the increased power consumptioncaused by the wider high-frequency bandwidth,6G radio a
188、ccess network should becapable of flexible and dynamic adjustment to make the wireless access points denseror sparser according to traffic changes in the network.Integrated sensing and communicationIn the future,the protocol stack will expand from a single communication servicetomulti-dimensionalser
189、vicessuchascommunicationandsensing,etc.Correspondingly,theprotocolfunctionalsoneedstosupportsensingandcommunicationintegration.Sensingandcommunicationintegrationcanbecomprehensively considered from the aspects of waveform design,parameterestimation,interference cancellation and architecture design.3
190、.2The architecture of the next-generation protocol stack3.2.1 Next generation cell model,Meta-cellThe traditional cell model cannot well meet the needs of customizable capability,elasticallyscalablecapability,andgrayscaleevolutionforfuturemobilecommunication networks,due to its tightly coupling betw
191、een services and resources,and tightly coupling between resources and resources.Furthermore,it is constraint forthe future network form and industry ecology.The future cell model needs on-demandorchestration of resources and services,and flexible networking.The next-generation cell model,Meta-cell(m
192、eta-cell implies source of the cell,essence of the cell,abstraction of the cell,or it can be understood as the futurecell model)in which radio resources and services are decoupled and able to beflexibly orchestrated,supports flexible scaling and smooth evolving of network.Full-band converged network
193、ing,user and multi-parties native networking,energyand cost-prioritized networking,etc can be achieved by Meta-cell.The network formand networking with Meta-cell can adapt to different business scenarios,differentservice types,and achieve higher performance indicators(KPIs)and low-carbon35sustainabl
194、e development goals.Meta-cell divides resources and services into different levels,and resources orservices at the same level are decoupled.Resources between different levels,servicesbetween different levels,and resources and services from different levels can beflexible mapped.It can customize effi
195、cient network forms and networking modes,andeven can give birth to a new business ecological models to orchestrate resources,andservices in Meta-cell,according to business scenarios and requirements.The networkbased on Meta-cell not only is adapted to various business scenarios,but also attachesimpo
196、rtance to efficiency and energy consumption of network and terminal.Figure 9(the right half of figure)shows the architecture of Meta-cell,which is divided frombottom to top into:carrier resource layer,channel resource layer,service layer,wherein channel layer can be further divided into transmission
197、 channel resourcesublayer and physical channel resource sublayer.CarrierLayerChannelLayerServiceLayerCarrierL2/L3serviceTransmissionchannelPhysicalchannelCarrierL2/L3serviceTransmissionchannelPhysicalchannelCarrierL2/L3serviceTransmissionchannelPhysicalchannelFigure 9 From traditional cell to meta-c
198、ell:on-demand multi-layer cell modelMeta-cell for multi-band converged networkingMeta-cell supports on-demand combination and orchestration of spectrumresources or carrier resources,which are in the same frequency band,or crossdifferent frequency bands,or in the same or different Frequency Range(FR1
199、/FR2),or36cross different Frequency Ranges.The combination or orchestration includes:carrierconcatenation to form a larger bandwidth spectrum resources for large throughputrequirements;carrierselectionaccordingtodifferentelectromagneticwavecharacteristics for large-capacity or wide-coverage.The abov
200、e-mentioned fullspectrum portfolio orchestration in Meta-cell,on the one hand,efficiently utilizesspectrum resources,and on the other hand,adapts to different business scenarios byflexible orchestration of spectrum resources.Spectrum portfoliosensingcommunicationFigure 10 Meta-celll:Service-oriented
201、 full spectrum portfolio orchestrationTo achieve the above goals,Meta-cell supports the decoupling of basebandprocessing and radio frequency processing,including that:multiple scattered radiofrequency carriers are aggregated and correspond a continuous baseband carrier.Network with baseband processi
202、ng in Meta-cell based on a continuous basebandcarrier will achieve low complexity and workload of network management,lowworkload of network management,network planning and network optimization.Carrierconcatenation(multipleradiofrequencycarriersareaggregatedandcorrespond a baseband carrier)in Meta-ce
203、ll improves the utilization efficiency ofscattered spectrum(such as re-farming FDD spectrum or TDD spectrum),andexpands bandwidth for physical channel(such as PDSCH/PUSCH)transmission,which increases the flow rate and reduces the overhead of configuration,scheduling,37and feedback.Figure 11 Meta-cel
204、l:Multiple RF carriers are aggregated into one baseband carrierFor full-band converged networking,Meta-cell supports the decoupling andaggregation of uplink and downlink to achieve on-demand orchestration andcombination of uplink carriers and downlink carriers,which improves coverage andperformance
205、of network.For example,large bandwidth uplink is urgently needed inTo B scenario.Meta-cell can support the aggregation of multiple uplink carriers or theaggregation of more uplink carriers than downlink carriers for To B scenario.Figure 12 Uplink and downlink decoupling and service-oriented orchestr
206、ation and38combinationMeta-cell supports decoupling of transmission channels to physical channels andon-demand mapping from transmission channels to physical channels.In thetraditional cell(such as NR cell),large XR data packets are put in a large TB(transport block)containing multiple CBs(coding bl
207、ocks),and any CB occuring errorwill cause that the entire TB cannot be delivered,resulting in lager latency for datatransmission.In the Meta-cell,the original TB is split into multiple TBs(multipletransmission channels)so that error in any TB will have no affect on delivery of otherTBs.Thereby it wi
208、ll greatly improve the performance of large-bandwidth andlow-latency services,such as XR.Figure 13 Meta-cell:Decoupling and aggregation between transmission channels andphysical channelsMeta-cell for user and multi-parties native networkingIn the future 6G era,in order to meet the requirements of us
209、er initiative andcustomization,it is necessary to consider user-centric networking,and it should beable to differentiate serving subject groups in more granularities,by using theirsimilar features to implement optimal stereoscopic network between users and users,39users and terminals,users and multi
210、ple parties,which is called user and terminalnative networking and multi-parties native networking.User and terminal native networking and multi-parties native networking has thefollowing forms:single-center mode(advanced and low-cost terminals collocation)and multi-center mode(peer terminals).Netwo
211、rking between terminals are based onD2D-like technologies.The network provides the cloud native DevOps environmentfor users and third parties.And users and third parties can deploy their applications inthe above environment to select and use the corresponding functions as required.Theapplications co
212、uld be application layer application(e.g.WeChat,SMS or clouddesktop)or a communication layer application.for example,an application on theRRC layer.The application of the RRC layer can arrange the networking betweenterminals and collaborate with the RRC application of the Mobile Operator(MO)toconstr
213、uct a cubic network.The advantage of the stereoscopic networking is to greatlyimprovethedegreesoffreedom:supportingmeshconnection,UC-MIMO(user-coordinated MIMO),improving the air interface KPIs(coverage,throughput,deterministic and positioning accuracy)and solving the problem of high-frequencycovera
214、ge.xNB NetworkingArchitectureTerminal NetworkArchitectureFigure 14 Meta-cell:multi-parties native and user native networkingMeta-cell for energy and cost-prioritized networkingMeta-Cell supports the construction network form and networking mode bymicro-kernelapproach,whichcanminimizeresourceoverhead
215、andenergyconsumption.The micro-kernel approach can be expressed as SSB resembling40connectionless on the air interface.It can be used as a micro-kernel-stylefunction/service to only transmit and receive SSB.By superimposing morefunctions/services,it can be extended successively to the system message
216、 SIfunction/service,access to the AC(Access)function/service,paging function/Services,and CA/DC functions/services,etc.Since the micro-kernel approach canminimize in greatest degree the functions/services that the terminal needs to support,the extremely low-cost and extremely low-energy terminals ca
217、n participate innetworking in the the micro-kernel approach.SSBSIACCA/DCPagingxSSBxSIxACxCA/DCxPagingXG evolution service modelbased on xSSB micro-kernel5G Service ModelBased on the SSB Micro-kernelFigure 15 Meta-cell:micro-kernel to support networking with energy priority and costpriorityMeta-cell
218、supports system message(SI)aggregation,that is,SIBs for multiplecarriers can are aggregated and transmitted on one carrier,so that other carriers neednot transmit SI and have a longer time“sleep”.Thereby it reduce the energyconsumption and the workload of network for SI transmitting,configuration an
219、dscheduling,and simplify network operation and maintenance.41Figure 16 Meta-cell:Aggregation of system informationAfter receiving the aggregated system information(SI)by Meta-cell,the terminal willreceive the multiple access channel(RACH)resource configurations.The accesschannels will correspond to
220、different spectrum resources.The terminal can select thebest spectrum for access according to coverage,frequency,and air interface quality.The optimal selection of RACH can improve the certainty(low-latency andhigh-reliability)of access,and quickly build connections in a frequency band with thebest
221、coverage/energy efficiency.Figure 17 Meta-cell:Aggregation of system information SI,aggregation or optimizedselection of RACH3.2.2 OrchestratableStack-Free Component-basedpacket forwarding protocolThe current wireless communication protocol stack architecture is designedbased on OSI seven layer mode
222、l.The functions contained in each layer are fixed andthe order is unchanged.This tightly coupled protocol stack greatly limits thedevelopment of 6G network architecture.Facing the new requirements,new scenarios42and new services of 6G,the forwarding plane function needs to meet the requirementsof fl
223、exible orchestration,customization,generalization andprocessing abilityimprovement.Therefore,6GneedstointroduceOrchestratableStack-FreeComponent-based packet forwarding protocol(OSFC).Facing the future user native and multi-parties native networking,and meetingthe requirements of different scenarios
224、,different service types and the pursuit ofhigher performance,the forwarding plane related protocols will develop in thedirection of componentization and parallelization of basic functions,including basicpackaging(concatenation/segmentation),reliability assurance,security assurance,flowsplittingandf
225、lowcontrol,routingandmapping,etc.Basedonthecomponentization of the basic functions of forwarding plane processing,anorchestrable stack-free component-based packet forwarding protocol(OSFC)isformed by flexibly orchestrating and configuring relevant components.The packetforwarding protocol has the cha
226、racteristics of componentization,vectorization andparallelization.Function componentization:The architecture of the forwarding plane of thetraditional communication system is very rigid.Introducing new functions orchanging a function will bring a chain reaction to all parts of the architecture,and t
227、he same functions of different layer cannot reuse the same process.In orderto reduce the coupling and redundancy between various functional modules of theforwarding plane,the component-based design principle of independence,noredundancy and free combination is very applicable.By componentizing thefu
228、nctions of the forwarding plane,the inherent function order of the originalprotocolt can be broken,the order of functional components can be changed,thecomponents can be on/off or added/deleted dynamically,and the customizationcan be carried out according to personalized requirements.At the same tim
229、e,thecomponentizedfunctionisextractedcommoncomponentsandcommonprocesses,so as to reduce the complexity of the protocol.In the new forwardingplane,independent components converge to form a component database.Through43theconfiguration,orchestrationandmanagementofcomponentsinthecomponent database,the f
230、orwarding plane can adapt to build a data transmissionchain according to various personalized needs.The component-based designprovides the possibility for the flexible arrangement of serial mode,parallel modeand serial-parallel mixing mode.This ensures that the components can beorchestrated flexibly
231、 and scaled elasticly on demand in 6Gs complex andchangeable scenarios.Vector Packet Processing(VPP):In the field of IT,in order to quickly buildswitching and routing functions,an extensible and high-performance packetprocessing framework vectorized packet processing(VPP)is introduced.Themain idea o
232、f VPP is to vectorize the continuous packets with the samecharacteristics for batch process,which is much better than the traditional singlepacket quantization.VPP design is introduced into the forwarding plane tovectorize the data packets,and batch process the continuous data packets ofperforming t
233、he same operation,which can significantly improve the processingspeed of data packets.Based on the componentization of forwarding plane,thegranularity of packet vectorization can be changed flexibly.For example,packetvectorization can be performed on a component,or packet vectorization can beperform
234、ed on one or several steps within a componentComponentparallelization(PC):Onthebasisofcomponentization,theforwarding plane can also realize multi-component parallel processing for asingle packet.These parallel components have the characteristics of independenceand statelessness,and the change of com
235、ponents order does not affect theprocessing of data packets.Components with these characteristics can beorchestrated in parallel to reduce data processing delay.The parallelization ofcomponents increases the dimension of component orchestration,enablescomponents to form a variety of combinations suc
236、h as serial,parallel and serialparallel hybrid,and increases the flexibility of forwarding plane.In generalscenarios,it is more common to use the mixed orchestration of component44parallel and component serial.In OSFC,componentization decouples the forwarding plane functions to form astack-free prot
237、ocol structure.Flexible component orchestration and packet vectorquantization realize the dynamic adaptive matching of traffic requirements in 6Gscenarios.According to the specific traffic scenario characteristics,packet types,component functions and other needs,the protocol architecture can be flex
238、iblyorchestrated into many forms,such as multi-component serial,multi-component serial+VPP,multi-component parallel,multi-component parallel+VPP,multi-componentserial parallel hybrid and multi-component serial parallel hybrid+VPP.The protocolalso supports cross domain or multi-hop deployment,which i
239、s very friendly to theadaptability of multi-level deployment,mesh networking and other scenarios.Theorchestrablestack-freecomponent-basedpacketforwardingprotocolOSFCfundamentally breaks the hierarchical concept of protocol stack and deepens thecooperation between components.It is key to improve the
240、data forwarding andprocessing ability of 6G network,and plays an important role in building aservice-orientedadaptiveflexiblenetwork.Moreover,throughtheintelligentconfiguration,intelligent orchestration and intelligent management of the forwardingplane components,the forwarding plane can introduce b
241、ig data and AI algorithms tofurther improve the intelligent level.Figure 18 multi-component orchestration with VPP45Figure 19 Single-hop OSFC with VPPFigure 20 Multi-hop OSFC with VPP3.2.3 Cloud native service based networkThe design of the 5G core network architecture adopts the cloud native SBA id
242、eain IT field,but the access network still retains the original layered architecture.Thesetwo different architectures make it difficult for the core network and access networkto mutual invocation,co-deployment,and O&M.With the commercial use of 5G,Thedemand for 6G network flexibility and ICDT integr
243、ation put cloud native 6G wirelessaccess network on the agenda.And the cloud native wireless access networkarchitecture also accelerates the integration of core network and access network.Cloud native concepts includes containerization,micro-service,DevOps,Conwayslaw,etc.These concepts run through t
244、he whole process of cloud native architecturedesign of wireless access network.By further enhancing the ability of rapidintegration,customization,orchestration,configuration,and extended iteration,the46next generation network extends the service-based architecture for core network toEnd-to-End Servi
245、ce-based Architecture(E2E-SBA).For the purpose,the radio accessnetwork should be refactored with SBA to support SBA-RAN.It should be noted thatwhile the UE and radio interface will also be redesigned in certain aspects with thebasic guideline of SBA.From the efficiency perspective,it is not suitable
246、 to copy theservice-based interface to the radio interface.Functions of real-time requirement stillneed to use original layered architecture).Refer to the concept of cloud native,tool chains,and domain-driven design,thecloud native architecture decouples domains with different life-cycles and formsf
247、unction sets based on independent life-cycles and service logic.Each domain has itsown life-cycle management.So that the next generation network can carry outindependent iterative update,grayscale evolution and cross domain CI/CD in differentdomains.Figure 21 Domain-Driven Design(DDD)Based on differ
248、ent service logic and life-cycles,cloud native service basednetwork is divided into PHY domain,PKT(packet)domain and HUB(control hub)47domain.Each domain can be partitioned according to functions attributes intoenforcement plane,control plane,storage plane,intelligence plane and OAM plane.For exampl
249、e,the PHY field is divided into five functional planes:PHY-E,PHY-C,PHY-S,PHY-I and PHY-O.With such design,functions with different attributes canhave different implementation platforms and deployment locations.They can be alsoorchestrated scalably on-demand.In addition,the control plane,data plane,a
250、ndintelligent plane can be flexibly orchestrated.Driven by their evolved requirementsfor further enhancement and evolution.All functions can be continuously orchestrated,customized,configured,and integrated into a network system.Figure 22 Two dimensional division of service network architectureThe c
251、loud native service based network not only reshapes future infrastructureecology,but also provides a deployable,multi-parties collaborative environment torealize domain level/function level interconnection.And the cloud native servicebased network can flexibly support the multi-parties native networ
252、king,user nativenetworking and the integration networking of communication,sensing,computing inthe future 6G network.483.2.4 The generalized QoS framework6G network supports new forms and new technical features in multi-partiesnative and user native networking,and the integration networking of commu
253、nication,sesing,computing,intelligence and trust.The traditional QoS framework ofcommunication system can not adapt to the new development of 6G,so it is verynecessary to introduce a new generalized QoS framework.The new generalized QoSsystem adopts a generalized perception engine including intentio
254、n,business,user,environment and scene perception,and uses the project-oriented principle forintelligent orchestration.The workflow formed by the orchestration is used to controlthe work decomposition and execution in different domains such as communication,sesing,computing,intelligence and security
255、domain.The project-oriented frameworkcan realize the entire closed-loop and whole process control of demand,delivery andsettlement,and form an traffic framework of value guidance and deterministicmanagement.The project oriented generalized QoS framework decomposes theproject into services in various
256、 domains ofcommunication,sesing,computing,intelligence and security,and carries out cross domain coordination of QoS anddeterministic guarantee of QoS in each link.Each link has QoS control correspondingto this link,relating the QoS of all links to ensure the overall end-to-end QoSrequirements.In th
257、e generalized QoS framework,it supports external input,QoSworkflow orchestration,QoS configuration at all levels,and policy schedulingaccording to QoS requirements at all levels.This new project oriented generalizedQoS framework forms a workflow through flexible orchestration on demand,realizesthe w
258、hole process and value chain closed loop of information flow,decision flow,execution flow and feedback flow,and can meet various service needs and qualityassurance.The generalized QoS framework covers the domains of communication,computing power,sesing,AI and the big data.There are different in metr
259、ics fordifferent domains,and the metrics can not be simply aggregated and stacked and49should be comprehensively considered in generalized QoS.That is,the metrics of thegeneralized QoS framework need to consider the integration after communication,sesing,computing power,AI and data at the beginning.
260、For example,in thecommunication traffic scheduling,in order to ensure the communication performance,the computing power needs to be guaranteed with deterministic;In AI and big data,the balance between computing power cost and power consumption needs to beconsidered.Based on multi-domain integration,
261、generalized QoS needs to determinethe weight of various metrics,establish a evaluation mechanism,and form acomprehensive metrics system that takes into account not only KPI(Key PerformanceIndicator)but also KVI(Key Value Indicator).3.3Review on 3.0 protocol stack functionThe Next Generation Protocol
262、 Stack White Paper 2.0 analyzes the mainproblems faced by the network and important scenarios for future networkdeployment,and explores better protocol stack architecture and functions.One of themain issues discussed in the Next Generation Protocol Stack White Paper 2.0 is howto ensure the high reli
263、ability of data transmission and the ultra-low delay requirementof a single service while meeting the low transmission resource cost.A variety ofsolutions proposed in The Next Generation Protocol Stack White Paper 2.0 includemulti-connection simultaneous transmission,single-link multi-transmission,M
264、ACand PHY protocol layer solutions.The Next Generation Protocol Stack White Paper 3.0 further studies the protocolstack architecture and protocol layer functions,and analyzes some existing problemsin the network.For example,there are deficiencies in cloud CU/DU.The strongbinding between CU/DU and pr
265、otocol stack function hinders the flexible on-demanddeployment of the protocol stack,resulting in limited network opening capacity andthe inability to achieve accurate opening and cloudification of network capacity.Inaddition,the problems faced by core network slicing and access network slicing are5
266、0also studied.According to the requirements of customers in the vertical industry,network slicing needs to refine the SLA requirements of end-to-end network slicing,decompose them into core network,wireless and transmission domains,and selectproper templates for slicing instantiation.In order to eff
267、ectively define SLA and carryout quality assurance,there is still a lack of end-to-end monitoring and dynamicadjustment mechanism for closed-loop operation of network slice.The next generation protocol stack white paper 3.0 analyzes the next generationprotocol stack from three directions:servitizati
268、on,componentization,and intelligence.For servitization,with the continuous expansion of service scenarios and deploymentscenarios,the requirements of network architecture for adaptability,includingflexibility,soft,scalability,evolution and recoverability,in addition to the traditionalefficiency requ
269、irements,continue to improve.In view of this,the service-orientedarchitecture with better adaptability naturally borrows from IT to CT:5G corenetwork innovatively adopts a service-based architecture that takes into accountadaptability and efficiency.However,from a global perspective,an end-to-end se
270、rvicearchitecture can fully meet the requirements of overall network adaptability.Forcomponentization,the function of the forwarding plane must first meet the basicrequirements of security,efficiency,reliability,QoS control,etc.In order to supportthe rich requirements of MEC,vertical industries,inte
271、gration of ground,air and space,integration of access and backhaul,dual connectivity,CA,URLLC,interoperabilityand other scenarios for the forwarding plane,the forwarding plane also needs to meetthe advanced requirements of universality,independence,compatibility,scalability,portability,openness,etc.
272、Therefore,the forwarding plane needs to adopt acomponent-based design idea,and comprehensively consider the basic and advancedrequirements of the forwarding plane to split the protocol stack into orchestrablemodular components,in order to achieve the balance between the basic requirementssuch as eff
273、iciency and reliability and the high-level requirements such as compatibility,scalability and openness.For intelligence,intelligence is one of the important drivingforces and enablers of the next generation access network architecture.Its influence51can provide micro empowerment in all functions of
274、the access network architecture,or provide meso empowerment beside these functions,and can also surpass allfunctions of the current access network to provide macro empowerment.The existingmobile communication systems combined with AI are mostly cloud-based centralizedlearning methods,that is,a large
275、 number of training data are transmitted to the cloud,and the corresponding decision-making model is distributed after deep learning.Thisnot only brings the problem of delay,but also has high requirements for transmissionbandwidth,which can not meet the real-time requirements of service.In the futur
276、e,with the significant increase of computing resources on the edge access side and theevolving network demand of differentiated services,AI and access network willcontinue to be deeply integrated.It can be seen that although different types of services or user requirementsemerge at different stages,
277、the network may face similar problems at different stages,and some functions need to be continuously enhanced.The enhancement of networkarchitecture and protocol stack functions is a spiraling and continuous process.4.Next-generation protocol stack enhancement4.1Space-Air-Ground-Sea Integrated Netwo
278、rkThe Space-Air-Ground-Sea integrated network is not a simple interconnection ofsatellites,various types of aircraft,and cellular network facilities on their originalbasis.It is necessary to fully integrate multiple access types in the system level,whichachieve deep mergein terms of architecture,pro
279、tocols,services,and terminals.And itcanprovideuserswithcontinuous,non-switch-aware,flexibleubiquitouscommunication services.Satellite communication network:Considering both the network coverage andservice quality at the same time,the satellite-ground integrated network architecture is52the key resea
280、rch direction for the construction of the SAGS integrated communicationsystem.The industry has proposed a variety of integration architectures includingsatellite as non-3GPP access and 3GPP RAT access.Among them,the former onlyconnects satellites to the 6G core network,while the latter is a deep int
281、egration ofsatellite network and terrestrial cellular network.In Rel-17,3GPP has started thestandardization work related to satellite communication mechanism enabled by 5G.The air interface adopts the 3GPP enhanced protocol,however it only focuses on thedeployment structure based on the transparent
282、mode,i.e.the satellite is used as aforwarding relay.Only the most basic functions are supported in Rel-17,performanceoptimization will be considered in subsequent release,including support for dualconnectivity and carrier aggregation,coverage enhancement,IoT terminals,etc.Meanwhile,new functions wil
283、l be introduced,including network-based positioning,support for terminals without GNSS positioning capabilities,broadcast and multicastservices,etc.With the advancement of related research and technology,6G basestation and even core network function can be deployed on the space-based network.This wi
284、ll require regenerative payloads on board the satellites and the inter-satellitelinks(ISLs)connecting them.In the future,it is very beneficial to comprehensivelyconsider the architecture design of the satellite-ground integration network accordingto the different integration architectures of the sat
285、ellite network and the terrestrialnetwork.Marinecommunicationnetwork:Themarineeconomy,especiallythecommunication involving marine machines,is receiving more and more attentionfrom all parties.The sea surface and underwater communication coverage areexpected to be solved in the 6G era.Marine communic
286、ation networks mainly includeshore-basedmobilecellularcommunicationsystems,maritimewirelesscommunicationsystems,satellitecommunicationsystems,andunderwatercommunication systems.At present,each system is independent of the other,theinterconnection and information transmission are not smooth,which can
287、not meet theneeds of new marine applications.How to coordinate multiple platform resources and53provide unified network architecture support is an urgent problem.We must ensurethe universal connection from the coast to the ocean,data transmission and relay canbe carried out between ships,ships and s
288、atellites,and various offshore platforms toensure the continuity of maritime services.At the same time,it is necessary tointegratecapabilitiesincludingnavigation,datamonitoring,andemergencycommunications to build an integrated ocean communication perception network andimprove the comprehensive level
289、 of marine informatization.Space-Air-Ground-Sea Integrated Network:In essence,SAGS integratednetwork is a layered and heterogeneous structure.Different access modes inintegrated network have their advantages and disadvantages in terms of coverage,transmission delay,throughput,mobility,reliability,et
290、c.In order to achieve the realsystem fusion networking,it is necessary to adopt effective air interface and networkmanagement technologies,including dynamic spectrum sharing and interferencecoordination,intelligent access and mobility management,as well as intelligentmanagement and scheduling of cro
291、ss-domain resources,etc.Specifically,as anessential part of SAGS integrated network,satellite systems have a series ofcharacteristics such as complex heterogeneity,time-varying topology,and limitednode resources,which brings huge difficulties to network management and resourceallocation.Based on the
292、 above discussion,an intelligent,simplified and universalprotocol that enables cross-network data transmission,though highly desirable,becomes a major challenge.SRv6 based on IPv6 and segment routing technologysimplifies network protocol types and has the advantages of strong scalability andprogramm
293、ability,as well as supporting large-scale networks.It has good applicationprospects and can be used as a candidate possible solution.Another point of interest isto simultaneous introduce new technologies such as artificial intelligence to helpimprove the efficiency of routing mobility management,com
294、plete rapid networking ina dynamic environment,and satisfy the needs of integrated slice management at thenetwork layer level.Furthermore,the combination of SRv6 and Software DefinedNetwork(SDN)technology,which can achieve the elastic reconfiguration of the54network and carry out flexible and effici
295、ent resource scheduling.The SDN controllercan maintain an integrated space-air-ground-sea network topology structure,andperform real-time network resource scheduling,routing strategy selection,as well asprotocol stack segmentation as its dynamic changes.4.2Intelligence based RAN5G raido network reso
296、urce allocation,resource management and scheduling arenetwork-centric.In the future,massive smart devices and sensors,greater connectiondensity,more diversified user requirements,more frequent intelligent interactions andpotentially high network energy consumption bring great challenges to 6G.6G nee
297、dsto study user demand centered and intelligence based dynamic self-organizingwireless access network technology.6G will be aware of user demands,servicerequirements and spectrum usage state changes in real time,and self-adapt thereal-time changing user demands,service requirements and spectrum dema
298、nds,inorder to achieve flexible usage of the end-to-end virtual resources,physical resourcesand spectrum resources for dynamically shaped wireless access network topology.The 6G spectrum is rich and diverse.Dynamic and intelligent spectrumselectioncan match the appropriate operation spectrum for spe
299、cific users and specificservices through intelligent perception of spectrum usage and analysis of frequencyband propagation characteristics suitable for service requirements,make full use ofthe available spectrum resources and control the interference in the network.Intelligent spectrum sensing tech
300、nology and intelligent spectrum sharing technologywill be important supporting technologies.The full-duplex technology can enableDynamic and intelligent spectrum selection to utilize spectrum resources moreflexibly.6G radio access points are diverse and the wireless propagation environment iscomplex
301、.Dynamic and intelligent routing selectioncan match suitable access points,fixed relay nodes,mobile relay nodes,or even reconfigurable smart surface panels for55specific users and services based on the intelligent perception and prediction of thedynamic wireless environment and node load,select the
302、best transmission path,reduce the wireless network congestion and interference,improve network coverageand ensure user experience.The 6G network topology is complex and the access points are denselydistributed.With the smart sensing and prediction of user demands and servicedemands distribution in t
303、ime and space,Dynamic and intelligent topology selectioncan identify the access points that need to be activated or hibernated and dynamicallyadjustwirelessnetworktopologyandnetworkconfigurationwithartificialintelligence technology.Real-time awareness of the quality of user experience andquality of
304、service are also important input for the Dynamic and intelligent topologyselection.At the same time,the sharp increase in the number of 6G access pointsand users makes the amount of data and signaling to be transmitted on the back linkincrease sharply.Thus,it is necessary to study the efficient wire
305、less backhaulmechanism with high capacity.Figure 23An example of intelligence based RAN scenarioUser demand may change in time and space.Dynamic self-organizing wireless56access network technology can integrate the network resources that are scattered indifferent geographical or logical locations to
306、 provide users with timely and effectiveservices.In the pursuit of wider and better coverage,support the universal existenceof artificial intelligence,at the same time it can control the growth of network energyconsumptionandimprovenetworkenergyefficiencytoachievesustainabledevelopment.4.3Adaptive p
307、rotocol stack for new architecture to support RANnodes cooperation4.3.1 New architecture to support RAN nodes cooperationIn“The next-generation protocol stack v3.0”,we proposed two types of newRAN architecture:HTC support architecture and separation of user and UEs.In HTCsupport architecture,an anch
308、or UE can trigger multi-network node to transmitservices cooperatively,according to the location information of the anchor UE.Inseparation of user and UEs architecture,multiple UEs serve one or a group of users.The two types of architecture can be combined as architecture to support RAN nodescoopera
309、tion.With the introduction of new services,applications and scenarios,RAN nodesincluding gNBs and UEs should work together to satisfy the QoS requirement of aspecific service,such as Holographic Communication service;or improve systemperformance in specific scenario,such as multiple devices in proxi
310、mity belonging toone user.For Holographic service,different profiles could be presented by different nodes,especially in large scale activity.The end points could be gNB(s)and/or UE(s).Anddifferent flows belonging to one holographic service should be transmitted tocorresponding end points via separa
311、te interfaces including wired and wirelessinterface such as Uu and sidelink.In this architecture,the functions and relationships57of RAN nodes should be redefined and remodelled,such as introducing L2 protocolarchitecture for multiple nodes cooperation.More detailed,RAN procedures such asaccess cont
312、rol containing participating node(s),system information,paging,andmobility should be studied considering multiple participated RAN nodes.In userplane,QoS satisfaction for coherent flows of specific service(s)/application(s)whichcould be transmitted/received in multiple terminals should be studied,su
313、ch assynchronization among the coherent flows.With the cooperation among gNBs andUEs,the new upcoming holographic service can be served in communication systempractically.For the scenario that a user owns multiple devices,UEs can be cooperated inRAN higher layer or physical layer.Service continuity
314、should be guaranteed indifferent terminals.Thinner protocol stack and diversified controlling mechanismover air interface are applicable.Other technologies for UE cooperation/aggregationinclude security for a group of UEs,connection control for the UE group,capabilitycoordination and etc.With UE coo
315、peration/aggregation,adaptive network deploymentcan be realized by adding/deleting UEs in a UE group dynamically while keepingservice continuity;uplink transmission can be enhanced to improve systemperformance.4.3.2 Flexible RAN node splitIn 5G R15 IAB SI,various proposals had been raised to split t
316、he RAN NW node,namely into one“Central Unit(CU)”and one or more“Distributed Units(DUs)”.These methods were captured in 3GPP TR 38.801,numbered according to the UPlayer whence the RAN node is split.At that time the SDAP layer was not introducedyet and thus not mentioned during the discussion.Finally,
317、option 2 is adopted thatPDCP is located in CU and other L2 sublayers are located in DU.58Figure 24 Candidates of CU-DU split in 5G SIThe motivation of flexible RAN node split for all of the splitting approachesstudied in TR 38.801 still persists.It can be a good direction to consider whendesigning t
318、he 6G network.The ideal way is to make every module flexible to deploy and configured,e.g.one RAN node can decide to use Option 2 for one radio bearer(i.e.utilisingRLC/MAC/PHY of another node for this radio bearer),whereas to use Option 3 foranother radio bearer(i.e.offloading the RLC/MAC/PHY but ho
319、lding the ARQfunction)and Option 6 for another more(i.e.offloading only the PHY toward anothernode).With the development of inherent AI and cloud computing in distributed RANnodes,flexible RAN node split can be adapted dynamically with or withoutpre-deployment and applied with flexible wireless link
320、 selection(Uu,sidelink,or IAB,UE relay,etc.).To apply flexible RAN node split,security of multi-CU-UP connection should bereconsidered.Taking gNB-CU-CP/UP split in 5G as an example(Figure 25),one gNBmay contain one gNB-CU-CP and one or more gNB-CU-UPs.It is a commonunderstanding that different gNB-C
321、U-UPs which are designed to provide differentservices(typically of different slices)are deployed at different positions.However,thesecurity architecture for 5G RAN still forces all the DRBs serving a given UE to usethe same algorithm keys for encryption and integrity protection respectively.And onth
322、e other hand,there is another common understanding(i.e.security isolation)thatone security key should not be used in multiple“security domains”.As the result,italmost prevents utilising multiple types of gNB-CU-UPs to serve one UE,and further59hinders the use of slicing in RAN.Figure 25 Overall arch
323、itecture for separation of gNB-CU-CP and gNB-CU-UPThis problem is widely acknowledged but left without any solution,mainly dueto its low cost-effectivity,i.e.it is not worthy to make any big change on RANsecurity structure once the 5G network is already taken in to use.For 6G,as the entire security
324、architecture will be designed from the beginning.Itis very beneficial to take multiple-CU-UP connectivity into consideration whendesigning the 6G security architecture,so that CU-UPs are unaware of the securitykey used its peers even if they are serving one UE,thus facilitate the virtualisation ande
325、nhance deployment flexibility of RAN UP functions.In flexible RAN node split,even with different L2 protocol(s)adopted in different DUs,the security algorithmand/or key(s)will be applied.4.3.3 L2 protocol split/aggregationIn the new architecture supporting RAN nodes cooperation,L2 protocol can bespl
326、itted or aggregated in both gNB side and UE side based on RAN node split andservice flow characteristics(such as co-flow requirements).DependsonflexibleRANnodesplitinsection4.3.2,L2protocolsplit/aggregation can be:-SDAP split/aggregation;60-PDCP split/aggregation;-RLC split/aggregation;-L1 split/agg
327、regation.Moreover,considering the multi-stream transmission in HTC,L2 protocolsplit/aggregation should be applied in SDAP sublayer or PDCP sublayer.And PDCPsplit/aggregation or split/aggregation in other sublayers can be applied to the scenariothat multiple UEs belonging to one or more users.Some ex
328、amples of L2 protocol split/aggregation are shown below:-SDAP split/aggregationAssuming different gNBs transmit part of sub-flow(s)of a HTC(or XR)serviceto one UE,SDAP split is performed by gNBs and SDAP aggregation is performed byUE.Figure 26 An example of SDAP split/aggregation61-PDCP aggregationF
329、or the scenario that multiple UEs belonging to one user or HTC serviceassociated to multiple RAN nodes,PDCP aggregation can be used.For example,multiple UEs can transmit same or different subflow(s)to gNB,and gNB canaggregate the transmissions by PDCP aggregation as in 29.Figure 27An example of PDCP
330、 aggregation4.4Integrated sensing and communicationIn terms of mobile network standardization,UE-oriented positioning has beenstandardized as a generalized sensing service in the 3GPP Rel-16 9,and will befurther improved in subsequent releases.In terms of WiFi standardization,the IEEE802.11 bf worki
331、ng group is defining standards based on WLAN to support high-valueuse cases and solve interoperability issues 10.For the scenarios of integratedsensing and communication,the sensing target can be UE in the wireless network,non-communication device(e.g.obstacle)or geographic area.Therefore,it isneces
332、sary to further enhance the protocol stack design for different integrated sensingand communication scenarios in order to meet the requirements from bothcommunication and sensing at the same time.According to the sensing signal sending node and the receiving node,it is62divided into the following 6
333、types of sensing links,as shown in the Figure 28.We justtake one sending node and one receiving node as an example in the Figure.More thanone sending nodes or receiving nodes can be used according to the sensingrequirements.During the sensing process,we can also use single sensing links ormore than one sensing links in different scenarios.According to the existing securityand privacy rules,the sen