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1、 The 6th Generation of Fixed Networks(F6G)-Space-Ground Integrated Optical Networks White Paper V1.1 State Key Laboratory of Information Photonics and Optical Communications(IPOC)Nov.4,2023 Abstract The trajectory towards the 6th generation of fixed networks(F6G)is forecasted to dramatically reshape

2、 the digital connectivity terrain,inaugurating a new era of space-ground integrated optical networks.This white paper ventures into the complexities of the inherent challengessuch as ensuring comprehensive coverage,robust survivability,seamless connectivity,advanced intelligence,and stringent securi

3、ty.It conducts an in-depth assessment of core requirements and cutting-edge technologies within five crucial domains:access,transport,networking,sensing,and display.Tackling these challenges directly,the document outlines strategies to attain all-encompassing coverage that overcomes geographic limit

4、ations,fortifies network resilience to withstand potential service interruptions,leverages Artificial Intelligence(AI)for anticipatory network governance,and maintains the integrity and confidentiality of a digital infrastructure thats growing increasingly exposed to threats.The white paper probes i

5、nto pioneering developments poised to surmount these obstaclesspanning from broadening access capabilities and refining transport protocols to optimizing networking configurations and enhancing sensing and display apparatus.Projected applications of F6G are set to be game-changers,offering round-the

6、-clock,global connectivity that catalyzes international engagement.The document forecasts the future influence of holographic communications,enabling profoundly immersive exchanges irrespective of distance;the harmonization of virtual and tangible realities,melding digital and physical realms;and th

7、e nexus of intelligent systems,nurturing a predictive,responsive,and autonomous AI-driven environment.In summary,this white paper acts as a manifesto for the upcoming F6G epochmerging the anticipated challenges,technological breakthroughs,and prospective applications into a unified framework.It pres

8、ents a roadmap for stakeholders to commence their journey as they steer through and contribute to the ever-expanding universe of ubiquitous connectivity.I CONTENTS 1.INTRODUCTION OF FIXED NETWORKS.1 1.1.FIXED NETWORK EVOLUTION HISTORY.1 1.1.1.Traditional Fixed Networks.1 1.1.2.F5G and F5G Advanced.2

9、 1.1.3.F6G.4 1.2.CHALLENGES FOR FIXED NETWORKS.5 1.2.1.Coverage.5 1.2.2.Survivability.6 1.2.3.Connectivity.7 1.2.4.Intelligence.8 1.2.5.Security.9 2.REQUIREMENTS FOR SPACE-GROUND INTEGRATED OPTICAL NETWORKS.10 2.1.HIGH-SPEED UNIVERSAL ACCESS.10 2.1.1.Wide Coverage.10 2.1.2.Large Bandwidth.11 2.2.LAR

10、GE CAPACITY AND SECURED TRANSMISSION.12 2.2.1.Large Capacity.12 2.2.2.High Security.13 2.3.HIGH-DYNAMIC INTELLIGENT NETWORKING.14 2.3.1.Empowering Networks with Strong Intelligence.15 2.3.2.High Reliability.16 2.4.MULTIMODAL ACTIVE SENSING.17 2.4.1.Integrated Sensing and Communication.17 2.4.2.Activ

11、e Sensing.18 2.5.HYPERSPATIOTEMPORAL HOLOGRAPHIC DISPLAY.18 2.5.1.Naked-eye 3D Display.19 2.5.2.Cooperative Communication and Display.20 3.ENABLING TECHNOLOGIES FOR SPACE-GROUND INTEGRATED OPTICAL NETWORKS21 3.1.ACCESS TECHNOLOGIES.21 3.1.1.Fixed Access.21 II 3.1.2.Wireless Access.22 3.2.TRANSMISSIO

12、N TECHNOLOGIES.23 3.2.1.Multi-dimension Multiplexing.23 3.2.2.Free-space Laser Communication.26 3.2.3.Physical-layer Security.27 3.3.NETWORKING TECHNOLOGIES.28 3.3.1.Intelligent Control Architecture and Protocols.28 3.3.2.Optical-Electrical Hybrid Switching.30 3.3.3.Resilience and Survivability.31 3

13、.3.4.Digital-twin System.33 3.4.SENSING TECHNOLOGIES.34 3.4.1.Integrated Sensing and Communication.34 3.4.2.Networked Intelligent Sensing.36 3.5.DISPLAY TECHNOLOGIES.36 3.5.1.Content Acquisition and Processing.37 3.5.2.3D Rendering and Display.38 4.F6G APPLICATIONS.40 4.1.ANY-TIME ANY-WHERE CONNECTI

14、VITY.40 4.2.HOLOGRAPHIC COMMUNICATION.41 4.3.VIRTUAL-REAL INTERACTION.42 4.4.CONNECTED INTELLIGENT SYSTEMS.44 APPENDIX I:ABBREVIATIONS.46 APPENDIX II：CONTRIBUTORS.47 1 The 6th Generation of Fixed Network White Paper V1.1 1.Introduction of Fixed Networks The Fixed network refers to a network that est

15、ablishes a fixed connection between communication devices via wired or wireless means,providing users with services such as voice,data,multimedia,and more.Through a century of development,the Fixed Networks have continuously evolved towards broader bandwidth,integration,IP-based technology,intellige

16、nce,and convergence.These networks bear the responsibility of transmitting vast amounts of information.They are critical national information infrastructures and form the foundational systems underpinning societys digital transformation.1.1.Fixed Network Evolution History Driven by computer and inte

17、rnet technologies,the Fixed Network has seen rapid development over the past three decades.1900-2000,the Fixed Network primarily handled voice services.It relied on copper-line infrastructure,utilizing PSTN/ISDN technologies,with a typical bandwidth of 64kbit/s.2000-2006,the Fixed Network mainly han

18、dled web services.The characteristic technology of this period was xDSL,which provided broadband capabilities below 20MHz.2006-2012,the Fixed Network mainly carried video streaming services.Depending on VDSL technology and fiber optic access,FTTB and PON+LAN access technologies allowed the fixed net

19、work to progressively offer 30-100MHz home broadband.2012-2020,the Fixed Network gained the capacity to support 4K ultra-high-definition video streams.The widely adopted PON+LAN could provide transmission bandwidth services of 100 megabits per second or even higher.With the advancement of technologi

20、es like cloud computing and the Internet of Things(IoT),new types of services demand higher quality standards.This has placed more stringent requirements on the bandwidth,latency,and reliability of the Fixed Network.As a result,the industry began to define the development path for fixed networks in

21、terms of generational divisions,introducing the concept of the 5th Generation of Fixed Networks(F5G).1.1.1.Traditional Fixed Networks From the inception of the telephone network to the end of the 20th century,the Fixed Network primarily serviced voice communications.Dial-up access and ISDN developed

22、 at a 2 The 6th Generation of Fixed Network White Paper V1.1 rather slow pace,only supporting audio services and dial-up calls.This period saw the establishment of a relatively complete telephone network infrastructure.Its network architecture and control signals were well-suited to the global netwo

23、rk,marking the onset of telecom globalization.The access network technology during this phase was PSTN/ISDN,and the corresponding transmission network used PDH technology,with a baseband rate of 2Mbps and fiber optic line rates primarily at 140Mbps.From the end of the 20th century to the beginning o

24、f the 21st,with the promotion of the Internet and ADSL technology,the fixed network entered a rapid development phase.The broadband era officially began,mainly servicing web applications.The widespread use of personal computers and browsers propelled the swift growth of the internet.Fixed network ap

25、plications expanded from telephony to include email,search engines,and web browsing.The access network was represented by ADSL technology(10Mbps),and the corresponding transmission network adopted Synchronous Digital Hierarchy(SDH)technology,with fiber optic line rates primarily at 2.5Gbps and 10Gbp

26、s.From 2005,driven by multimedia services,there were significant changes in both the services and the network architecture of the Fixed Network.Traditional ADSL technology and the existing telephone network architecture couldnt support broadband services,leading to the introduction of VDSL technolog

27、y(30Mbps200Mbps).The corresponding transmission network used MSTP technology,which,based on SDH technology,added the capability to handle Ethernet data services.From 2012,with the emergence of 4K high-definition signals,a fixed network of no less than 100Mbit/s became necessary.Optical access networ

28、ks represented by GPON technology achieved uplink aggregate rates of 1-2.5Gbps.With high bandwidth,stability,simplified structure,and long-term development potential,it garnered the attention of operators.The mainstream transmission technology adopted was Optical Transport Network(OTN),combining the

29、 advantages of Wavelength Division Multiplexing(WDM)and SDH technologies.It achieved comprehensive speed upgrades in optical fiber lines,with a single-wave rate reaching 100Gbps.A single optical fiber could simultaneously transmit 80 wave signals,achieving line rates of 80 x100Gps.1.1.2.F5G and F5G

30、Advanced In February 2020,the European Telecommunications Standards Institute(ETSI)announced the establishment of the F5G Industry Working Group to a global audience.They 3 The 6th Generation of Fixed Network White Paper V1.1 introduced an industry vision of moving from fiber to the home to fiber co

31、nnecting everything,marking the official start of the F5G era.By February 2020,major global operators,equipment manufacturers,industry associations,and research institutions had joined the working group.F5G has three main features:Enhanced Fixed BroadBand(eFBB),Full-Fiber Connection(FFC),and Guarant

32、eed Reliable Experience(GRE).In September 2022,the ETSI Fifth-Generation Fixed Network Industry Working Group released a white paper titled F5G Advanced and Beyond.The white paper outlined the driving factors,capability dimensions,and key enabling technologies for the evolution from F5G to F5G Advan

33、ced(also known as F5.5G).Broadly speaking,F5.5G enhances and expands on F5G in the following perspectives:eFBB:With more advanced fixed network technology,network bandwidth capacity can be increased by more than tenfold,achieving symmetrical upstream and downstream bandwidth capacities.This facilita

34、tes gigabit homes,ten-gigabit buildings,and hundred-gigabit parks.Using next-generation technologies such as Wi-Fi 7,50G PON,and 800G,user bandwidth experience can be elevated from 1Gbps to 10Gbps everywhere.FFC:Through comprehensive coverage of fiber optic infrastructure,fiber is extended to every

35、room,every desktop,and every machine,fully expanding vertical industry applications.Service scenarios expand by more than tenfold,and the number of connections increases by more than a hundredfold,achieving coverage of 100,000 connections per square kilometer.This forms the digital foundation for sm

36、art homes/business collaboration/full-fiber digital parks.GRE:Supports zero packet loss,microsecond latency,and 99.999%availability.Paired with AI-powered intelligent operations,it meets the ultimate service experience demands of home and business users.In terms of guaranteed experience,autonomous d

37、riving upgrades from L3 to L4.Home broadband transitions from visual positioning to experience self-optimization,while dedicated lines/network computing achieves rapid intelligent connections.Furthermore,F5.5G expands in three directions:Real-time Resilient Link(RRL):In industrial scenarios,RRL meet

38、s the requirements of microsecond-level latency and six-nines(99.9999%)availability.Optical Sensing and Visualization(OSV):Focuses on building optical communication sensing integration and digital operational capabilities.GAO:OTN to Every Site,aiming for one-hop direct access,enhancing site efficien

39、cy by tenfold.4 The 6th Generation of Fixed Network White Paper V1.1 Fig.1:Evolution History of Fixed Networks 1.1.3.F6G Although F5G and F5.5G can satisfy a variety of terrestrial service requirements,ground-based fixed networks face challenges in terms of coverage area and construction costs.The r

40、apidly evolving space-based communication system,anchored by satellites,is set to deeply integrate with ground-based Fixed Networks.Together,they aim to provide broadband communication services for consumer-grade internet service,forming the 6th generation fixed network(F6G).The development path is

41、illustrated in Fig.1.Space-ground integrated optical networks(SGION)are the primary composition of future F6G network architecture research.The backbone network,formed by satellites,ensures that users across the globe can access high-speed broadband wireless services anytime,anywhere.This overcomes

42、geographical challenges,enabling high-speed communication between any two points on Earth,be it on the ground,in high-altitude platforms,or anywhere in between,achieving global seamless coverage.F6G aims to realize the interconnection of satellite networks and terrestrial fiber networks,constructing

43、 SGION.This satisfies the varying demands of different industries for the next-generation network,significantly enhancing user experience,promoting the digital transformation of society,and fostering high-quality growth in the digital economy.The shift towards integrating space and ground networks i

44、snt just a technological evolution,and it represents a fundamental reimagining of how we approach global connectivity.The F6G vision encapsulates the aspiration for a truly interconnected world,where everyone,5 The 6th Generation of Fixed Network White Paper V1.1 no matter their location,can access

45、high-quality digital services.The fusion of ground-based fiber-optic networks with the ubiquity of satellite coverage is an exciting step forward in the world of telecommunications.1.2.Challenges for Fixed Networks The 2021 China Internet Development Report highlights that the development of the Int

46、ernet has entered the phase of IoT,with new applications posing more stringent challenges to Fixed Networks.To support the future demands of IoT,F6G will focus on enhancing network capabilities to address challenges in areas of coverage,survivability,connectivity,intelligence,and security,as shown i

47、n Fig.2.Fig.2:The Challenges for F6G 1.2.1.Coverage The traditional terrestrial Fixed Network excels in its high data transfer speed,low latency,and massive connectivity capacity.However,its coverage is limited,making construction and operation in remote and uninhabited areas difficult and costly.Cu

48、rrently,over 70%of the Earths geographic space,encompassing 3 billion people,remains without internet coverage.To support the communication needs of emerging services like digitized management of uninhabited areas and interconnection of spatial intelligent entities in the future,terrestrial networks

49、 need to merge with space satellite networks.This will create a space-ground integrated backbone network,pushing the traditional network to shift from human-centric to thing-centric coverage,providing universal broadband connectivity for global users.SGION will face the following coverage challenges

50、:6 The 6th Generation of Fixed Network White Paper V1.1 Coverage Speed:Terrestrial fixed networks can achieve access speeds of up to 10Gbps,and this will further evolve to 100G based on 50G-PON.However,the current satellite networks access speed is still relatively limited.Elevating the access speed

51、 of satellite networks in covered regions is a pivotal challenge.Coverage Latency:Sub-millisecond latency will become a comprehensive demand for SGION.Supporting applications with sub-millisecond,millisecond,and ten-millisecond latency coverage is a paramount challenge.Coverage Density:As we transit

52、ion from human-centric to thing-centric coverage,applications such as ubiquitous smart connectivity,direct mobile connection,and aerial-terrestrial interconnection will significantly enhance demands for network accessibility,reliability,and coverage density.Compared to traditional networks,the devic

53、e density per unit area of the next-generation network will surge by 100 to 1000 times.Efficiently increasing coverage density is another pivotal challenge.1.2.2.Survivability Network survivability refers to the ability of a network to handle failures,playing a crucial role in ensuring the network o

54、perates smoothly.Statistics show that the average repair time for optical fiber network failures can range from 5-10 hours.Insufficient survivability can severely affect service quality and user experience.Traditional fixed network survivability mechanisms focus mainly on small-scale failures,ensuri

55、ng a degree of self-recovery in the face of such malfunctions.However,they often fall short when confronted with regional-scale failures.SGION broadens the coverage scale of the network,which in turn increases the range of potential failure risks.In the future,dynamically operating satellite network

56、s will face potential threats from space debris,laser weapons,etc.,which might lead to large-scale node or link failures.To address wide-scale failure risks,the survivability of SGION needs to evolve from self-healing to self-organizing.Dynamically scheduling and configuring satellite nodes and inte

57、r-satellite links,will support the intelligent self-organizing of terrestrial space networks,thereby enhancing their resilience and survivability against large-scale failures.SGION will face the following challenges of survivability:Dynamic Service Management:Given the dynamic nature of SGION,especi

58、ally the satellite-ground link component,real-time sensing of the status and connection of inter-satellite/satellite-ground laser links is fundamental for ensuring service survivability.The pivotal 7 The 6th Generation of Fixed Network White Paper V1.1 challenge lies in realizing the dynamic monitor

59、ing and management of wide-area services.Space-ground Collaboration:Due to constraints in the current network transmission systems and operation methods,the terrestrial and satellite layers of the network essentially adopt a domain-specific governance model.The key challenge for cross-domain service

60、s is how to realize the collaborative linkage of multi-domain resources to complete path integration and end-to-end resource coordination.Self-organizing Resilience:Traditional service survivability mechanisms rely on real-time acquisition of a given topology for service path calculations.However,in

61、 F6G scenarios,the mobility and randomness of paths in satellite platforms are accentuated.Therefore,the central challenge for ensuring service survivability in F6G scenarios lies in how to realize self-organizing resilience and survivability.1.2.3.Connectivity With the deepening development of soci

62、etys digital transformation,various internet applications emerge endlessly.Rapid growth in internet traffic has brought immense load-bearing pressure to optical communication networks.In the face of continuously increasing service traffic,current communication networks are actively exploring new con

63、nection technologies with higher bandwidth and lower latency.However,with the development of AR/VR,the metaverse,and AI,SGION landscape of the future will see more interactive applications characterized by intelligent entity interconnection.To adapt to the high dynamics of space networks and intelli

64、gent entity terminals,besides providing basic connection capabilities,the network also needs to precisely manage the positions of high-dynamic networks and terminals.The service model of the network will evolve from static connections to dynamic connections,thereby providing highly reliable network

65、connections for rapidly moving intelligent entities.SGION will face the following challenges in managing dynamic connectivity:Dynamic Channel Maintenance:Within SGION,inter-satellite links move rapidly as satellites orbit.The length,position,and other attributes of these links display high dynamic c

66、haracteristics.Adapting to these dynamic attributes by adjusting channel parameters and maintaining the communication capability of the channel is one of the key challenges in realizing the dynamic connection of SGION.High-speed Connection Handover:The rapid movement of satellites also leads to 8 Th

67、e 6th Generation of Fixed Network White Paper V1.1 frequent switching of Earth-satellite links,affecting the continuity of the services carried.Ensuring seamless handover in high-dynamic scenarios to guarantee uninterrupted and stable end-to-end service capabilities is a pivotal challenge in creatin

68、g the dynamic connection capabilities of SGION.Precision Positioning and Tracking:In the future,communication between satellites,and between satellites and high-altitude platforms,will mainly depend on laser links,which have extremely high directionality requirements.In such a high-dynamic network,p

69、recisely positioning and tracking between satellites and high-altitude platforms is one of the critical challenges for managing the dynamic connection of SGION.1.2.4.Intelligence As the development of AI progresses,the level of intelligence in the Fixed Networks has significantly improved,marking a

70、transformation from manual control and software control to AI-assisted control.However,due to the complexity of network structures and protocols,network management still heavily relies on professional knowledge and skills.The intelligence features currently seen in traditional optical fiber communic

71、ation networks(such as AI-based traffic prediction and fault diagnosis)often only serve as auxiliary functions,making it difficult to fully automate and intelligently control the network.The scale and dynamism of SGION bring significant challenges,and the effectiveness of traditional decision-making

72、 intelligence to aid decisions may also be suppressed.To cope with the high dynamism in controlling the future SGION and to enhance the level of network intelligence,intelligent control technology for this SGION will evolve from decision-based intelligence to generative intelligence.This will levera

73、ge generative AI to understand network problems and autonomously create network control schemes,greatly enhancing network automation.SGION faces the following challenges of intelligence:Large Models for Network Operations:Integrating network operations with professional large models can effectively

74、enhance general intelligence levels.However,constructing these large models requires vast model scales,high storage and computation costs,and complex model tuning and optimization.This represents a significant challenge in building large models for SGION.Autonomous Control based on Generative AI:Bui

75、lding on professional large models,generative AI for SGION needs to be multimodal and knowledgeable across all domains.It also 9 The 6th Generation of Fixed Network White Paper V1.1 demands strict accuracy and appropriateness.How to develop robust control applications based on generative intelligenc

76、e is key to harnessing intelligent capabilities.Collaboration between AI and Humans:While AI applications assist humans in intelligent control,they also inevitably bring errors and risks due to automated operations.How to ensure effective collaboration between AI and humans during the intelligence p

77、rocess and avoid risks caused by mis-operations is a key technical challenge.1.2.5.Security Currently,the security technology standards and applications in Fixed Networks are mature,relying mainly on classical cryptography to encrypt information and ensure its protection.However,with the continuous

78、advancements in quantum computing and the widespread application of AI,the security system based on source encryption is facing threats such as store now,decrypt later attacks.Specifically,the future SGION will deploy a large number of satellite nodes in public space.The open communication channels

79、will face many unknown security threats and challenges.As a result,there is a need to further promote the security architecture upgrade of SGION,enhancing the security system from data security to channel security.By utilizing physical channel-level security measures,the confidentiality and security

80、 of information transmission can be improved.SGION faces the following security challenges:Physical Channel Encryption:In SGION,the transmission performance of satellite-to-ground communication is affected by factors such as transmission power,tracking errors,and various interferences.Satellites are

81、 expensive to deploy and require coordinated management with ground stations.Designing a low-power,highly compatible physical channel encryption solution to achieve high transmission and security performance is a significant challenge.High-speed Key Negotiation:SGION relies on free-space lasers.With

82、 long link distances and an open-space transmission medium,securely distributing keys among various nodes becomes complex.How to distribute keys within SGION is a key challenge.Security Risk Detection:Compared to traditional fixed networks,the dynamism and complexity of SGION make it difficult to ac

83、curately perceive and assess overall security risks.The vast number of interconnected components,including satellites,ground stations,and control centers,increases the attack surface and potential risks.Actively perceiving security risks is a key challenge.10 The 6th Generation of Fixed Network Whit

84、e Paper V1.1 2.Requirements for Space-ground Integrated Optical Networks For future high-dynamic,interactive network applications,the F6G network based on terrestrial-space integration will exhibit new demands and development trends in aspects of access,transmission,networking,sensing and display,as

85、 shown in Fig.3.Fig.3:Space-ground Integrated Fixed Optical Networks Technology Category 2.1.High-speed Universal Access Currently,the population coverage of terrestrial communication services is approximately 80%.However,limited by economic costs and other factors,it only covers about 20%of the lan

86、d area,which is less than 6%of the earths surface area.In the future,the space-based satellite network will become the second network outside the ground fixed network.While providing broad coverage capability,it will also serve as a supplement to the ground fixed network,carrying an increasing amoun

87、t of Internet traffic,as shown in Fig.4.The access capability of traditional ground fixed optical communication networks within the coverage range is already considerable,while the access capability within the coverage range of satellite communication networks is still relatively limited.The develop

88、ment of an SGION needs to focus on improving coverage and access capabilities.2.1.1.Wide Coverage Satellite optical communication terrestrial optical communication technologies complement each other,paving the way for a globally encompassing SGION.For coverage capabilities,fiber optic access network

89、s efficiently serve densely populated terrestrial regions,drawing on the immense capacity of passive optical networks.In contrast,satellite network with free space optical communication technology shines in its ability to cover remote and uninhabited areas,leveraging its inherent broad reach.AccessN

90、etworkingSensingDisplayTransmissionGround-basedOptical CommunicationsSpace-basedOptical Communications 11 The 6th Generation of Fixed Network White Paper V1.1 Enhancing Ground Network Coverage:Emphasis should be placed on advancing FTTR(Fiber to The Room)and FTTM technologies.FTTR seeks to replace e

91、xisting network cabling systems with indoor optical fibers in every room.When integrated with next-generation WiFi or terahertz access technologies,it promises a broader coverage footprint.Transitioning to FTTM will augment this access networks coverage even further.The terrestrial optical access ne

92、tworks scope will extend beyond conventional home broadband,encompassing novel broadband optical access scenarios like all-optical parks,all-optical factories,and all-optical campuses.This will be a significant stride toward a large-scale,all-optical IoT.Fig.4:The Global Coverage of SGION Augmenting

93、 Space Network Coverage:Beyond merely increasing satellite counts,a stratified communication network can be designed using satellites in high,medium,and low Earth orbits,thereby broadening global coverage.The spatial networks coverage primarily hinges on its network architecture and communication te

94、chnologies.Regarding network architecture,better coverage can be realized by fine-tuning satellite constellation orbits and network topologies.In the realm of communication technologies,space networks lean heavily on inter-satellite laser communication.Satellite-to-ground communication predominantly

95、 employs millimeter-wave and ultra-high-frequency transmissions,collectively bolstering the networks satellite-to-ground link management and coverage.2.1.2.Large Bandwidth Traditional satellite communication technology is primarily focused on data communication and relay,mainly serving professional

96、applications with a small number of 12 The 6th Generation of Fixed Network White Paper V1.1 services and low access rates,belonging to the space-based narrowband communication system in terms of access capability.The future low earth orbit satellite communication network will face a large number of

97、smart network terminals and various Internet services,requiring the provision of broadband access capabilities at the scale of Gbps.To enhance the access capability of SGION,it is necessary to achieve coordinated access between high and low Earth orbit satellites and the ground and to realize flexib

98、le scheduling of space,ground,and base resources to support the complementary advantages of the space-ground access system.This will promote the current access capability from ground-based broadband+space-based narrowband to ground-based broadband+space-based broadband.Enhancing the access capabilit

99、y of SGION also relies on the theory of optoelectronic information and the integration of high-bandwidth communication,high-precision detection and remote sensing technology.Considering forward-looking application scenarios such as deep space exploration relay,ocean information fusion,and Earth grav

100、ity field measurement,the user side needs to develop high-performance,multimode,miniaturized,and low-power new satellite intelligent information terminals.This will further support the deep integration of the F6G network and realize intelligent elastic access and seamless handover.2.2.Large Capacity

101、 and Secured Transmission With the integration of space and earth networks,connectivity will span across the sky,land,and sea,achieving full-time,omnipresent interconnection.The number of connected terminals and the volume of data they carry will dramatically increase.At the same time,inter-satellit

102、e and satellite-to-earth communication links,which traverse open space,face risks of interception and intrusion.In the future,SGION needs to possess a high-capacity secure transmission capability,as illustrated in Fig.5,to ensure secure and high-speed connectivity.2.2.1.Large Capacity Traditional ne

103、twork capacity is focused on a single network scenario,with the primary objective of meeting its service traffic requirements.However,it does not support the traffic demands of SGION.To address the rapid growth of traffic caused by SGION,it is necessary to upgrade a large capacity in both the transm

104、ission and switching aspects of the network.Multi-band Transmission:By expanding the spectral bandwidth of optical transmission systems,the capacity can be increased.Mainstream optical transmission systems are typically 13 The 6th Generation of Fixed Network White Paper V1.1 based on the C band(span

105、ning from 1530nm to 1565nm,encompassing approximately 35nm of fiber optic spectrum).However,it should be noted that the low-loss window of standard single-mode fiber is much larger than 35nm.Other bands(such as the O,E,S,L,and U bands)may exhibit slightly higher fiber loss compared to the C band,but

106、 these bands remain within the low-loss range of 0.4dB/km and can be effectively utilized.This signifies a strong potential for capacity expansion through the utilization of these alternative bands.Fig.5:High-capacity and Secure Transmission of SGION All-optical Switching:With its high bandwidth,low

107、 latency,low energy consumption,and reconfigurable features,this technology stands as a key enabler for achieving large-capacity switching.By employing optical switches for network interconnection,connections can be established for diverse service flows,thus bypassing electronic bottlenecks and fulf

108、illing the requirements for both low latency and energy efficiency in large-scale networks.2.2.2.High Security Traditional networks encrypt data at the upper layer using encryption algorithms based on mathematical complexity and achieve network security through techniques such as firewalls and media

109、 access control.The transmission system in the physical layer only provides transparent transmission services.To address the security risks brought by the open space of SGION,the network will upgrade the security system at the physical layer.SGION will shift 14 The 6th Generation of Fixed Network Wh

110、ite Paper V1.1 from data security to channel security.The channel security in the physical layer is based on the physical channel characteristics to achieve key distribution and data encryption.It also can identify potential attack behaviors by monitoring physical layer characteristics.Physical-laye

111、r Channel Encryption:The openness,high coverage,and broadcasting characteristics of SGION provide natural eavesdropping conditions for eavesdroppers,making information transmission easy to eavesdrop and interfere with,and giving more space for malicious attackers to hide,so the physical layer channe

112、l encryption is needed to resist these attacks.Physical layer channel encryption greatly improves the difficulty of intrusion and interception by illegals by using the uniqueness,time variability,and spatial de-correlation of the channel,and thus guarantees the reliability of the communication of SG

113、ION.Physical-layer Key Negotiation:In SGION,different devices and systems need to communicate and exchange data with each other.Only devices or parties with the corresponding secure keys can encrypt communication data,thereby ensuring data security during transmission.Regular key updates and effecti

114、ve key management are crucial to maintaining the security of communication and data transmission.The secure key distribution system should be capable of achieving secure and efficient key updates.Cyber Threats Detection:SGION cover vast areas and face significant security threats,especially attacks

115、occurring at the physical layer,such as eavesdropping and interference.In SGION scenario,theres a need for low-cost,high-coverage channel attack detection methods to continuously monitor SGION and promptly pinpoint any network attacks.2.3.High-dynamic Intelligent Networking SGION exhibit profound dy

116、namism.Space-based networks,constantly in motion relative to terrestrial aggregation points and user terminals,present unique challenges.Similarly,the satellites within these networks are in perpetual high-speed motion relative to each other.Addressing this swift movement necessitates the evolution

117、of networking technologies.High-Dynamic Intelligent Networking leverages cutting-edge,dynamic-responsive control technologies.This approach ensures the adaptive management of network endpoints,links,and topologies,enabling SGION to offer consistent,end-to-end services,as shown in Fig.6.15 The 6th Ge

118、neration of Fixed Network White Paper V1.1 Fig.6:Highly Dynamic Networking of SGION 2.3.1.Empowering Networks with Strong Intelligence The term intelligence in networking often alludes to the enhancement of automated network controls using AI.While AIs role in traditional networks has been substanti

119、al-mainly focusing on tasks like traffic prediction and fault diagnosis-the demands from SGION are far greater.The heightened scale and dynamism call for more advanced AI applications,emphasizing the need for generative AI-driven approaches to empower the network with enhanced intelligence.Intellige

120、nt Topology Management:In these dynamic network environments,relying on conventional passive topology management is no longer viable.Their limitations become pronounced,necessitating the development of AI-driven proactive topology management solutions.These solutions offer precision in predicting ne

121、twork topology shifts,ensure adaptive link adjustments,and guarantee seamless transitions between satellite and terrestrial links,catering to the demands of ever-evolving topologies.Intelligent Traffic Scheduling:Within SGION framework,communication traffic patterns are profoundly influenced by netw

122、ork dynamics.Addressing these variable traffic 16 The 6th Generation of Fixed Network White Paper V1.1 patterns demands the inception of intelligent traffic scheduling mechanisms tailored for such dynamism.Implementing these mechanisms will enable dynamic traffic distribution modeling,ensuring diffe

123、rentiated service quality,adaptive load distribution,and synchronized satellite-ground connectivity.2.3.2.High Reliability The traditional network survivability emphasized service recovery.However,SGION confronts more intricate challenges,especially when considering potential large-scale infrastruct

124、ure failures in space-based networks.The self-organizing capabilities enable network nodes to make informed decisions,like orbital adjustments and topological reconstructions,promoting a robust self-healing network environment.Network Self-organizing Protocol:Building a truly autonomous SGION requir

125、es self-organizing protocols for expansive space networks.Such protocols allow for real-time network state monitoring,adaptive link restructuring,and ensuring the networks resilience to maintain superior service quality even in the wake of unexpected disruptions.Adaptive Link Management:Beyond just

126、topological reconfigurations,ensuring communication link availability is crucial.This underscores the need for adaptive link management strategies.By dynamically adjusting link attributes-like modulation and coding schemes-based on real-time data,these strategies ensure the networks communication ca

127、pacity remains optimal even during unforeseen challenges.Fig.7:Multimodal Sensing Capability of SGION 17 The 6th Generation of Fixed Network White Paper V1.1 2.4.Multimodal Active Sensing SGION effectively enhances multimodal sensing capabilities.The sensing based on the wide-area network allows for

128、 the acquisition of multimodal information such as location,speed,and distance data,as shown in Fig.7.Moreover,multimodal sensing can elevate the networks intelligence level.Through multimodal sensing,comprehensive detection and analysis of network parameters and the environment can drive the realiz

129、ation of adaptive networking,dynamic routing,and intelligent scheduling.The multimodal sensing capabilities will become a key technology catalyst for enabling new network applications.2.4.1.Integrated Sensing and Communication Integrated sensing and communication refer to the native design of integr

130、ating sensing and communication functions through means such as spectrum or hardware sharing,enabling communication networks to perceive multimodal information while transmitting information.Integrated sensing and communication systems,through methods like detection,tracking,recognition,and imaging,

131、have already provided crucial technological support for fields such as human-machine interaction and smart cities.The development of SGION will further enhance the demand for intelligent communication networks and multimodal fusion sensing,thereby improving the comprehensive service capability of co

132、mmunication systems.Intelligent Communication Networks:Traditional communication networks cannot adaptively adjust network configurations based on channel conditions,device conditions,environmental factors,and other factors.In large-scale and highly dynamic SGION,there is a need for adaptive network

133、 configuration adjustments.These adjustments should be highly reliable and possess fault-tolerance capabilities.This is crucial for providing better service quality,improving resource utilization efficiency,ensuring network stability and reliability,and establishing an intelligent communication netw

134、ork system.Multimodal Fusion Sensing:Multimodal fusion sensing involves the fusion of data from various types of sensors to provide users with richer,more accurate,and more intelligent services.Furthermore,given the expansive architecture and substantial capacity demands of SGION,it is imperative to

135、 investigate the development of streamlined,low-complexity next-generation communication-sensing systems.These systems should aim to enhance sensing performance while facilitating data sharing and collaborative efforts.This is done while ensuring communication quality and meeting sensing requirement

136、s to support new applications.18 The 6th Generation of Fixed Network White Paper V1.1 2.4.2.Active Sensing Active sensing refers to the systems ability to proactively acquire and process various sensory information to achieve a more comprehensive sensing.Classical optical sensing technology typicall

137、y operates in a passive mode,relying on models that associate sensor system parameters with patterns of environmental change and achieving passive sensing of the external environment through real-time monitoring of sensor parameters.The demand for active sensing includes the need for active probing-

138、type sensing devices and a unified sensor management platform.Active probing devices can proactively collect sensing information,while the unified management platform can coordinate and integrate multimodal sensory data,offering users and applications a more comprehensive and efficient perceptual ex

139、perience and digital management capability.Active Probing Sensing Devices:The realization of active sensing capability heavily relies on probing-type sensing devices.These devices possess the ability to sense in multiple modes,enabling them to collect various sensory elements on-demand,including vis

140、ual,auditory,tactile,and more.This capability provides critical support for future innovative interactive network applications.The versatility and programmability of these sensing devices allow them to adapt flexibly to various scenarios,meeting diverse requirements from users and applications.Senso

141、r Digital Management Platform:Active sensing capability also depends on a unified management platform for sensors to ensure the collaboration of sensing devices,the coordination and integration of data,and the efficient management of multimodal sensory elements.Within SGION,this management platform

142、establishes unified standards and protocols for sensory devices on a global scale,ensuring interoperability between devices and facilitating seamless transmission and centralized management.2.5.Hyperspatiotemporal Holographic Display With the progress of the content industry and the development of t

143、he consumer economy,the demand for 3D displays in various industries has been increasing year by year.However,to achieve a new type of 3D display technology with high realism and immersion,it is necessary for 3D display devices to have characteristics such as large amounts of light field data and st

144、rong real-time interaction,which leads to a high demand for communication networks in this technology.With the help of large capacity and low latency wide area information transmission capabilities,combined with new 3D display technology,future communication networks will 19 The 6th Generation of Fi

145、xed Network White Paper V1.1 provide ultra-realistic display capabilities that seamlessly connect time and space,providing users with immersive scenes and experiences,as shown in Fig.8.In SGION,the hyper-temporal display capability will fully connect people and objects in three-dimensional space,end

146、owing users with richer interaction and exploration capabilities,and supporting remote games,education,medical,and other activities.Fig.8:Spatiotemporal Capability of SGION 2.5.1.Naked-eye 3D Display Naked-eye 3D display refers to the ability to achieve 3D scenes for naked eyes in the space-ground i

147、ntegrated F6G,such as telemedicine teaching and remote meetings so that viewers can more accurately capture relevant information and make accurate on-site judgments.Compared to traditional 2D image transmission pixel information,the precise transmission of voxel information in 3D image information h

148、as increased the transmission demand by about three orders of magnitude,and the existing network transmission capacity cannot support the large-scale application of naked-eye 3D.Based on the traditional video image display,the high realism and immersion brought by the communication terminal of naked

149、-eye 3D display and the real-time characteristics of communication put forward higher requirements for the network.Compared with traditional high-definition and 3D virtual video,streaming media for naked-eye 3D display will require Gbps level bandwidth.Moreover,with the increase in sensor 20 The 6th

150、 Generation of Fixed Network White Paper V1.1 resolution and the number of viewpoints,higher network bandwidth will be required at higher resolutions and frame rates,especially with the application of high-precision quantum sensors.The naked-eye 3D display requires first acquiring object information

151、 through the acquisition device,calculating and processing it,encoding and compressing it for network transmission,decoding and rendering it on the terminal side,and displaying the 3D image.To reduce the overall latency,the processing nodes need to have high computing power,and the network itself ne

152、eds to further reduce the transmission latency.2.5.2.Cooperative Communication and Display Traditional communication networks provide pipeline-style data transfer capabilities to provide data support for the display end.The amount of information collected by the 3D display is extremely large,and the

153、 transmission of multi-dimensional information over long distances requires high synchronization.Its communication protocol is also difficult to meet the real-time interaction requirements of existing 3D display technology.Future applications of hyper-space display will place more stringent requirem

154、ents on the performance of communication and display systems,and promote the cooperation of communication and display systems.Compared to the traditional networks independent service approach of communication and display,communication and display cooperation will realize the mutual sensing and inter

155、active writing of communication and display systems,further accurately controlling the effectiveness and fidelity of display.All-dimension Synchronization:in the process of transmission,quite strict synchronization needs to be maintained between various concurrent media streams from different sensor

156、s and dimensions.In addition,it is also necessary to intelligently control multidimensional information.Interactive Communication Protocols:to achieve connected and perceived video transmission and intelligent communication,such cooperation relies on more intelligent and efficient coding and decodin

157、g technologies to alleviate the control information delay and jitter in the process of multi-dimensional resource linkage.21 The 6th Generation of Fixed Network White Paper V1.1 3.Enabling Technologies for Space-Ground Integrated Optical Networks When confronted with the technological challenges of

158、SGION,the subsequent technologies will form the backbone of its future evolution,catering to the emerging needs in connectivity,data transmission,network architecture,sensing,and visualization.3.1.Access Technologies 3.1.1.Fixed Access The next-generation PON technology refers to the next generation

159、 of higher speed,larger capacity,more flexible,and broader coverage-related optical access networks used to transmit optical signals to households or enterprises.With the vigorous development of emerging services such as the next-generation Internet,cloud computing,IoT,5G/6G,and 4K/8K high-definitio

160、n video,the fiber access network,as the last mile connecting people,things,and cloud interconnection,is undergoing a profound transformation toward higher speed,larger capacity,more flexibility,and broader coverage.Currently,ITU-T has already released the standards for 50G PON,and research on access

161、 networks beyond 50G PON is also ready to be launched.For the post-50G PON era access network,the single-wavelength rate is expected to develop towards 100G or even 200G.For such high transmission rates,it is challenging for traditional direct detection schemes to meet the power budget requirements

162、of the access network.Coherent technology with higher spectral efficiency and higher receiver sensitivity is gradually penetrating short-distance applications.To meet the power budget requirements of the access network,coherent technology in access network has attracted more and more attention from

163、researchers.The key technologies for the next-generation PON are as below:Coherent Algorithms for High-Speed Transmission:In coherent detection,it mainly involves reducing the number of high-speed devices,bandwidth,and linearity by advanced linear and nonlinear algorithm.In terms of coherent access

164、infrastructure and multiplexing methods,new point-to-multipoint coherent access architectures such as FDM or TFDM can be introduced.In addition,one major challenge in time-division multiplexing systems is burst-mode coherent reception upstream.Unlike traditional continuous coherent detection,new eff

165、icient signal processing methods,such as burst-mode coherent reception,are urgently needed.Burst-Mode Coherent Reception and Multi-dimensional Multiplexing:For fronthaul and broadband optical access of F6G,all-optical parks,and industrial Internet scenarios,it is 22 The 6th Generation of Fixed Netwo

166、rk White Paper V1.1 essential to focus on solving the problems of limited sensitivity and dynamic range of the next generation of super 100G or 200G optical access.To achieve rate-adaptive flexible coherent optical access,relevant key enabling technologies include 200G+coherent multiple access techn

167、ology with new point-to-multipoint,low-cost,low-complexity,flexible access,multidimensional multiplexing,multidimensional multiple access coherent optical access architecture,ultra-large dynamic range optical access and flexible optical access technology based on constellation shaping.Access rates c

168、an be further improved by combining linear and non-linear ISI equalization using end-to-end optimization based on machine learning.High performance,flexibility,and intelligence in bidirectional transmission can be achieved through multidimensional coherent access with breakthroughs in multidimension

169、al multiplexing mechanisms for time,frequency,and power domains.3.1.2.Wireless Access In the SGION,satellite networks will no longer be just a complement to terrestrial networks,but will be further integrated with terrestrial networks.Wireless access technology will play a pivotal role in SGION.On o

170、ne hand,wireless access technologies facilitate the connection of mobile terminals to the network.On the other hand,they also bridge satellite and ground networks.Unlike the wireless access technologies of terrestrial networks,those intended for SGION will evolve along the lines of multi-technology

171、integration and multi-band sharing.Relevant technologies include space-ground integrated 5G/6G and high-capacity microwave.Space-Ground Integrated 5G/6G Cellular Access:This is an extension of traditional wireless communication technologies toward SGION,aiming to upgrade satellite communication tech

172、nology to provide direct satellite connections for terrestrial consumer terminals.There are two main challenges that this technology is currently facing.Firstly,for satellites to perform the role of cellular base stations,they must overcome the distance transmission challenges of 5G/6G frequency sig

173、nals.Mobile communication technologies using large antennas at lower frequencies can mitigate long-distance transmission attenuation,potentially becoming an effective solution for 5G/6G phones to connect directly to satellites.Secondly,satellite base stations and ground base stations must have colla

174、borative service capabilities.The main challenge lies in the intelligent and agile management of SGION,especially when addressing the access and switching needs of high-speed mobile terminals.Centralized control in a large-scale network may face significant signaling delay issues,necessitating distr

175、ibuted signaling and control mechanisms between space and earth stations.23 The 6th Generation of Fixed Network White Paper V1.1 High-Capacity Microwave Access:This can support both broadband access for dedicated satellite terminals and high-speed interconnections between ground stations and satelli

176、te networks.There are two main challenges that this technology is currently facing.Firstly,the frequencies used for satellite microwave communication are limited.To meet the growing demands of satellite communication,its essential to delve into higher frequencies like Ka and V bands.However,higher f

177、requencies are more susceptible to atmospheric attenuation,requiring innovative compensation technologies.Secondly,traditional communication satellites have limited capacity,making them unsuitable for consumer internet traffic demands.High-throughput satellite technologies,using methods like spot be

178、am technology and frequency reuse,can significantly reduce interference between channels,thereby achieving higher data rates.Radio over Fiber:This technology boasts advantages such as long transmission distances,resistance to interference,large capacity,and low distortion.It is particularly suited f

179、or broadband access in satellite terminals and the high-speed interconnection between ground signal stations and satellite networks.The technology primarily faces challenges in two areas:on the one hand,transmitting satellite signals in the optical domain subjects them to noise and link nonlinearity

180、 effects,potentially limiting the dynamic range of the entire link.There is a need for enhanced research in nonlinear compensation of the system link in the future,aiming to expand the links dynamic range,subsequently improving system performance and signal quality.On the other hand,the use of analo

181、g transmission systems is susceptible to signal impairment issues such as noise and distortion,which could lead to a decline in signal quality in applications that demand high-quality signals in optical communications and satellite networks.The employment of high-quality optoelectronic devices and s

182、ignal processing technologies is essential to reduce noise and distortion.Moreover,the utilization of appropriate signal error correction and modulation techniques can also enhance signal reliability.3.2.Transmission Technologies 3.2.1.Multi-dimension Multiplexing In the context of F6G,the annual co

183、mpound growth rate of global traffic is expected to reach as high as 30-40%.The maximum transmission capacity of a single traditional single-mode optical fiber is limited to 100Tb/s.However,the existing OTN infrastructure in current optical communication systems will be insufficient to meet the dema

184、nds of global information flow.The transmission technology in optical fiber communication needs a transition from the 24 The 6th Generation of Fixed Network White Paper V1.1 sole WDM to multi-dimensional multiplexing within multiple-band and Spatial Division Multiplexing(SDM).With multi-band multipl

185、exing,we can make full use of the S-band,U-band,and other spectral resources beyond C and L band,to achieve the single-fiber 100 Tb/s transmission capacity.Within spatial-division multiplexing,mature solutions include various pathways such as multicore and few-mode optical fibers,as well as their co

186、mbinations.These approaches transform traditional single-mode optical fibers into parallel pathways,significantly increasing the transmission capacity of optical fibers.This has the potential to approach Pb/s-level capacity within the integrated F6G optical network.Although significant progress has

187、been made in the fabrication of multicore and few-mode optical fibers and in the technology for ultra-high-capacity spatial-division multiplexing transmission systems,there are still substantial challenges to be addressed before the deployment of spatial-division multiplexing in the F6G optical netw

188、ork.Key technologies that underpin the realization of spatial-division multiplexing optical transmission include the design and fabrication of novel spatial-division multiplexing optical fibers,the design and fabrication of large-scale spatial-division multiplexing devices,and low-power,high-perform

189、ance damage mitigation for optoelectronic-coordinated large-scale parallel channels.New Band Optical Amplifiers:Emerging band optical amplifiers,such as S-band thulium-doped,bismuth-doped optical fiber amplifiers,U/E-band bismuth-doped optical fiber amplifiers,and ultra-wideband semiconductor optica

190、l amplifiers,represent recent research focal points and constitute pivotal technologies to be surmounted for spectrum expansion.The development of new band optical amplifiers hinges on novel doping element formulations,advanced doping fiber fabrication techniques,and innovative optical amplifier arc

191、hitectures.Bismuth ions exhibit unique wide-spectrum luminescent properties,making bismuth-doped optical fibers a promising component in future ultra-wideband optical amplifier devices.Nevertheless,the underlying near-infrared emission mechanisms related to bismuth ions necessitate further explorati

192、on.Semiconductor optical amplifiers,on the other hand,require investigation into new compositions and control mechanisms to mitigate nonlinear distortions,enhance saturation power,and reduce noise figures.New SDM Optical Fibers:These primarily include multicore and few-mode optical fibers,and their

193、optimal designs must be determined from a global optimization perspective,considering variables such as crosstalk,mode coupling,multi-path interference,and attenuation.Weakly coupled spatial division multiplexing multicore optical fibers can significantly reduce the complexity of DSP equalization at

194、 the receiving end and are likely to be deployed in the 25 The 6th Generation of Fixed Network White Paper V1.1 F6G optical network.Additionally,there is a need to focus on optimizing the differential mode group delay(DMGD)in few-mode transmission,and this can be achieved by leveraging the character

195、istics of novel weakly coupled multicore and few-mode optical fibers with low DMGD,which have the potential to approach Pb/s-level transmission capacity.Furthermore,ongoing advancements in the preform preparation and drawing processes of specialty optical fibers,as well as the development of low-cos

196、t methods for the mass production of multicore and few-mode optical fibers,are critical for driving the commercial adoption of spatial division multiplexing transmission technology within the F6G optical network.New Optical Communication Devices:The large-scale parallelism of SDM demands more from c

197、urrent commercial optical devices.This includes receiver and transmitter arrays,cost-effective multiplexing and demultiplexing components,amplifiers for multiple modes and multiple cores,and precise connectors.The fabrication challenges are as complex as SDM optical fibers.Receiver and transmitter a

198、rrays can benefit from established technologies like silicon-based and thin-film lithium niobate,increasing product quality and integration for spatial division multiplexing.For multicore/mode coupling,creating passive components like multiplexers,demultiplexers,and connectors presents challenges.Te

199、chniques like optical fiber bundle tapering,planar waveguides,and new meta surface structures for phase control require further research.Amplifying multicore and multi-mode signals are crucial.Separate amplification increases system size and power use.Balancing crosstalk and gain are vital.Combining

200、 specialty gain fibers and integrating attenuation control waveguides helps optimize these aspects.Nonlinear Equalization Algorithms:Nonlinear equalization and compensation for intra-channel and inter-channel interference within modes/cores are essential at the receiving end.Traditional optical fibe

201、r communication technologies rely on the utilization of Multiple Input Multiple Output(MIMO)digital signal processing techniques to address such impairments.In the context of ultra-high-capacity transmission,the scale of MIMO is expected to increase significantly,imposing more stringent demands on t

202、he fabrication process of the receiving ASIC chips.Opto-electronic cooperation offers an effective solution to the high fabrication requirements of MIMO algorithms for ASIC chips,while significantly reducing the power consumption of these chips.The fundamental approach involves compensating for a po

203、rtion or the entirety of interference between cores/modes through optical information processing,thereby notably reducing the scale of MIMO algorithms and the tap length of equalization filters.The challenge lies in achieving fast optical information processing for damage compensation.26 The 6th Gen

204、eration of Fixed Network White Paper V1.1 With in-depth research in the field of optical computing and the advancement of integrated photonics technology,there is potential to combine optical computing methods to achieve all-optical on-chip MIMO demultiplexing operations,enabling low-power,high-perf

205、ormance damage equalization in large-scale parallel channels through opto-electronic cooperation.3.2.2.Free-space Laser Communication Free-space Laser Transmission Technology refers to a technique that utilizes laser beams as carriers to directly transmit information in the space.The application of

206、free-space laser transmission for inter-satellite communication and communication between satellites and ground stations plays a pivotal role in achieving high-capacity satellite-to-satellite communication and satellite-to-ground communication within integrated space and ground networks.The demand f

207、or higher data rates and capacity in space,sky,and ground integrated networks,such as F6G networks,has stretched the limitations of traditional microwave-based communication systems,making it challenging to further enhance their capacity.Free-space laser transmission offers several advantages,includ

208、ing wide bandwidth,high capacity,high data rates,compact antenna size and weight,and low power consumption.Leveraging free-space laser transmission technology,the capacity of space-based satellite networks can be enhanced from the current 15 Gbps to well beyond 100 Gbps,significantly boosting the ca

209、pacity of space-based internet connectivity.This technology encompasses high-quality optical system design,high-precision capture and tracking targeting techniques,atmospheric impact compensation for space-to-ground links,high-power transmission,and high-sensitivity reception techniques.Atmospheric

210、Impact Compensation for Space-to-Ground Links:When laser beams propagate through the atmosphere,they are subject to the effects of atmospheric channels.Atmospheric absorption and scattering result in laser energy attenuation,thereby affecting laser power.Atmospheric turbulence scintillation and atmo

211、spheric turbulence flicker can influence laser quality,leading to phenomena like drift in the center of the laser spot and wavefront distortion.These conditions can impact the effectiveness of free-space laser communication,and in severe cases,result in communication breakdown.Hence,it is necessary

212、to employ atmospheric impact compensation technology for space-to-ground links to reduce the fundamental impact of the atmosphere on laser beam wavefront phase,power fluctuations,and enhance the usability of free-space laser communication.The challenge in atmospheric impact compensation lies in the

213、spatial and temporal randomness of atmospheric effects due to the 27 The 6th Generation of Fixed Network White Paper V1.1 stochastic nature of atmospheric channels.Atmospheric impact compensation technology encompasses adaptive optics,spatial diversity in transmission and reception,mode diversity re

214、ception,and special beam techniques.High-Power Transmission and High-Sensitivity Reception:Free-space laser communication often involves long distances without relay stations,leading to significant signal attenuation after long-distance transmission.This results in a sharp degradation of the SNR at

215、the receiving end,posing challenges for communication transmission and reception.On one hand,compensating for the losses incurred during long-distance,non-relayed transmission is achieved by increasing the transmission power at the sending end.On the other hand,at the receiving end,high-sensitivity

216、reception technology is employed to reduce the required received power,thereby enhancing the signal-to-noise ratio of the received signal.This ensures that the laser communication system maintains sufficient link margin.High-power transmission technology is primarily achieved through high-power acti

217、ve optical fiber amplification,while high-sensitivity reception technology encompasses modulation techniques with high energy efficiency and precise digital signal processing techniques.3.2.3.Physical-layer Security In SGION,spatial laser links are highly vulnerable to eavesdropping and interception

218、 by attackers,which will lead to the leakage of sensitive information.This imposes a critical demand for the security of SGION.To enhance the security of SGION,the development of physical layer security protection technology based on spatial laser intrinsic security is a crucial part of the future S

219、GION.Unlike traditional network security technologies,spatial laser endogenous security technology does not rely on additional external key distribution and security monitoring.It can provide endogenous security protection for data transmission by the communication system itself.The characteristics

220、of spatial laser endogenous security technology can be summarized as“integrating the encryption and defense with transmission”.Spatial laser endogenous security communication can simultaneously achieve secure transmission and key negotiation based on a unified spatial channel.It also can monitor the

221、 security state of the laser link.Core technologies include encrypted transmission,key negotiation,and proactive detection of network attacks.Encrypted Transmission:Encryption transmission is one of the most important secure transmission techniques.Through the use of encryption algorithms,the signal

222、s in the channel are transformed,and the legitimate can only restore the original signals by possessing the key,28 The 6th Generation of Fixed Network White Paper V1.1 to ensure that the signals cannot be read by unauthorized illegals in the transmission process.The communication network model in SG

223、ION has the characteristics of a large spatial span,long time extension,and fewer channel feedback link channels,and the physical layer encryption requires efficient algorithms to reduce the impact on the transmission performance while maintaining high security.This problem can be solved by choosing

224、 fully verified and optimized encryption algorithms,using data compression and optimization techniques to reduce the amount of encrypted data,designing better compilation codes,and designing better modulation schemes.Secret Key Negotiation:The process of generating and distributing a shared key betw

225、een legitimate parties.The purpose of key negotiation is to enable authorized parties to encrypt and decrypt using the same key,thereby facilitating encrypted communication.One of the challenges of key negotiation lies in generating highly consistent and secure keys among authorized parties.Using ph

226、ysical layer characteristics such as bit error rate,light intensity,and phase in classical channels can extract highly consistent secure keys.These methods primarily depend on the influence of environmental changes in free space on laser transmissions,offering high compatibility and speed.However,th

227、ere is a slight deficiency in security and consistency.Privacy amplification is an effective method to improve key consistency.It typically employs error-correcting codes to rectify inconsistent keys and discards keys that might have been compromised due to information exchange.Channel Anomaly Detec

228、tion:In SGION,channel anomaly detection is used to detect and recognize malicious attack activities for enhancing communication security.It closely associates data security with the physical characteristics of communication.When the network experiences an attack,it often leads to abnormalities in th

229、e signal state,such as irregular signal strength,phase fluctuations,or changes in spectral features and propagation delay.These anomalies can be monitored by using methods like machine learning in the entire network.It means this technology offers broader coverage without the needs of additional har

230、dware,which reduces the costs of detection.Therefore,channel anomaly detection in SGIO enables it to effectively handle various network attacks.3.3.Networking Technologies 3.3.1.Intelligent Control Architecture and Protocols Satellite optical communication networks surpass terrestrial in terms of te

231、mporal and 29 The 6th Generation of Fixed Network White Paper V1.1 spatial distribution scales.The rapid movement of satellite nodes results in dynamic changes in satellite connectivity and network topology,rendering the control system architecture of terrestrial optical communication networks inapp

232、ropriate.Furthermore,the temporal and spatial distribution,bandwidth and latency of space network differ significantly from those of terrestrial network.Thus,theres a need to explore different network control mechanisms to support SGION.It is imperative to design efficient control architectures and

233、protocols for highly dynamic,large-scale networks.The technologies involved include centralized and distributed collaborative control architectures,rapid routing and signaling protocols,dynamic network self-organization,and seamless switching protocols.Centralized and Distributed Collaborative Contr

234、ol:This new architecture manages the integrated large-scale,high-dynamic communication infrastructure of space and ground.It combines the strengths of centralized and distributed controls,balancing global network and service management efficiency with the reliability of distributed collaboration in

235、high-dynamic environments.One of the challenges is finding the right balance between centralized and distributed functionalities.Centralized systems should not become bottlenecks or single points of failure,while still granting distributed nodes enough autonomy to respond to real-time changes.For in

236、tegrated optical networks,control architectures will involve multiple levels of centralized and distributed collaboration.In centralized aspects,massive networks can undergo hierarchical centralized collaboration through domain-specific control.Meanwhile,peer centralized control units need high-avai

237、lability backups.In distributed aspects,network devices can perform distributed cooperation.In this new collaborative architecture,advanced AI will play a significant role,enhancing prediction abilities for network dynamics,failures,and traffic attributes,and leveraging generative capabilities to bo

238、ost network automation and maintenance.Fast Routing and Signaling:These are foundational protocols supporting the topology,resource,and service management of SGION.The dynamic nature of satellites means network topology will continuously update.Traditional routing will constantly flood the network i

239、n response to connectivity changes,severely impacting network availability.Furthermore,the long transmission distance of large-scale networks increases signaling delay,reducing service efficiency.Fast routing and signaling aim to overcome aforementioned challenges,enabling quick route convergence an

240、d signaling transmission.Predictive routing update technology based on AI will aid rapid route convergence,while deterministic signaling technology ensures signaling message priority during forwarding,compressing forwarding delay and compensating for additional propagation delay to achieve low-laten

241、cy signaling.30 The 6th Generation of Fixed Network White Paper V1.1 Self-organizing and Switchover Protocols:These are crucial for automatically responding to physical node and link availability changes in high-dynamic networks to maintain continuous communication capabilities.Given the dynamic env

242、ironment of integrated networks,satellite nodes face the risk of timely faults while their dynamics cause connectivity changes with ground stations.AI predictive technology can forecast imminent switches,establishing connections with the next node before the current link disconnects.Buffer synchroni

243、zation during switching caches essential data,ensuring data continuity.3.3.2.Optical-Electrical Hybrid Switching Inter-satellite networks enable real-time data communication among different types of application satellites and support cross-regional connectivity.The backbone information network of sp

244、ace-based satellites needs to provide stable and reliable data-forwarding services to various types of users.It is also necessary to develop a multi-type,multi-level hybrid network.Efficient forwarding on satellites is one of the key enabling technologies.Therefore,to meet the networking and informa

245、tion transmission requirements of future space-ground integration,research is needed on comprehensive coverage in space,air,and ground domains,as well as the characteristics of multi-system data transmission and multimodal exchange in scenarios involving the hybrid networking of microwave and laser

246、inter-satellite links.This research should focus on high-speed data forwarding and switching technologies,such as on-board optical switching,microwave channelization optical switching,and digital switching.The goal is to achieve efficient data forwarding and exchange on satellites under constraints

247、of volume,weight,and power consumption.Satellite Switching:The space resources on satellite payload platforms are limited,thus there is an urgent demand for compact,low-power,and lightweight optical switching matrix modules.Additionally,for the composite transmission of large-granularity services th

248、rough inter-satellite laser links,it is necessary to combine wavelength-division multiplexing technology with wavelength-based optical switching technology.The complex application environment in space requires high signal isolation between different channels in the optical switching matrix module to

249、 ensure signal quality and achieve high-throughput lossless data switching.Furthermore,the optical switching matrix module needs to possess the characteristic of non-blocking full switching to enable flexible channel configuration and versatile deployment of services.31 The 6th Generation of Fixed N

250、etwork White Paper V1.1 Digital Switching:For space-based optical communication,it is necessary to store and forward user service packets,and to demodulate the optical signals sent by the all-optical switchboard.Therefore,digital switching technology is required to group and exchange the demodulated

251、 all-optical switching data frames based on the specific forwarding table on the satellite,and finally modulate the grouped data into optical signals to be sent to the all-optical switchboard.Digital switching requires functions such as service adaptation,all-optical switching virtual channel cross-

252、connection,label forwarding information table,traffic scheduling,internal cache,automatic protection switching,etc.At the same time,digital switching needs to support small-granularity packet service transmission,and combined with all-optical switching to achieve service aggregation and distribution

253、,unified carrying and forwarding,to adapt to more types of channel access and mixed-granularity service switching.Microwave Optical Channelization Switching:To meet the different needs of on-board users,it is necessary to achieve arbitrary switching of multiple frequency bands and make single-freque

254、ncy bands flexible and tunable.Therefore,microwave optical channelization switching technology is required,which can achieve low-complexity,high-capacity satellite switching.This technology achieves the integration and reconstruction of multiple narrow-band signals with different bandwidths through

255、channel allocation,channel cutting,and signal reconstruction,thus completing the entire process of microwave optical channelization switching.The process of microwave optical channelization switching needs to be realized by switching the optical carrier instead of the payload signal.It guarantees th

256、e SNR without reducing the signal power and requires small independent modules to be integrated,based on arbitrary wavelength selection as the core technology,to achieve scalable,multi-channel microwave optical switching.3.3.3.Resilience and Survivability Since an SGION is surrounded by a space envi

257、ronment,atmospheric environment,and ground environment,the network reliability is easily affected by a complex environment.In the ground environment,communication equipment and fiber links are extremely vulnerable to natural disasters and man-made damage,such as earthquakes,construction,floods,heavy

258、 rainfall,typhoons,landslides,debris flows,wildfires,tornadoes,hail,flash floods,blizzards,etc.In the atmospheric environment,atmospheric turbulence,cloud cover,rain attenuation,snow attenuation,etc.,affect communication quality and even lead to the interruption of the satellite-ground link.In the s

259、pace environment,satellite eclipses,sun outages,plasma,solar 32 The 6th Generation of Fixed Network White Paper V1.1 activity,meteoroids,space debris,and geomagnetic fields can cause satellite failure or lead to the interruption of satellite-ground links and inter-satellite links.How to accurately e

260、valuate the reliability of SGION and reduce the occurrence or probability of failures from the beginning of network design is the first task to ensure the reliability of SGION.In addition,for SGION with a huge scale,failures are inevitable,so it is urgently needed to provide reliable services in the

261、 case of failures.Reliability Evaluation:Reliability evaluation of SGION.Compared to the fixed node-link connection relationship of the ground optical networks,the positions of satellite nodes and the relative distances between satellite nodes in the satellite network are functions of time as a vari

262、able,and the topological relationship of the network changes periodically.Aiming at the space environment,the atmospheric environment,and the ground environment of each factor caused by the decline in the performance of SGION failure of quantitative indicators to describe and establish the mathemati

263、cal connection between the environmental factors and the reliability of SGION,the formation of reliability evaluation index system for SGION.Simultaneously,the state-transfer relationship of SGION is established due to the influence of the space environment,atmospheric conditions,and ground surround

264、ings.The state-transfer relationship of a unified SGION is defined,and the transfer probability between states is calculated,forming the reliability evaluation model for SGION.Anti-Destruction:For the SGION,the satellite network is in the space environment,the satellite-ground link is in the atmosph

265、eric environment,and the ground network is in the ground environment.The satellite network has relative disaster independence from the ground network;hence,the satellite network and the ground network can cooperate to achieve space-ground integrated anti-destruction networking.Since the capacity of

266、the satellite laser link is smaller than that of the ground fiber link,the performance of the laser link is lower than that of the fiber link,and the cost of the laser link is also higher than that of the fiber link,the construction of space-ground integrated anti-destruction requires to carry out t

267、he comprehensive trade-offs in the aspects of anti-destruction ability,expenditure,network performance and transmission quality,which is necessary to ensure acceptable cost,network performance,and transmission quality while improving network resilience.Intelligent Construction and Assurance:SGION is

268、 affected by multiple environments,e.g.,space environment,atmospheric environment,and ground environment,and it is difficult to predict the transmission performance degradation caused by device aging,air pressure,temperature and humidity changes,etc.The accuracy of sudden multi-fault locations cause

269、d by 33 The 6th Generation of Fixed Network White Paper V1.1 extreme environments is low,and real-time adaptive network adjustment cannot be realized,which makes it difficult to guarantee the transmission quality and system performance of the SGION and affects the carrying capacity and service quali

270、ty of the SGION.The agent construction and assurance method use AI to achieve optimal integrated coverage and realizes accurate prediction of the transmission quality of the optical signal and adaptive adjustment of the modulation format by perceiving the space environment and atmospheric environmen

271、t,to ensure the stability of SGION.3.3.4.Digital-twin System For SGION,large-scale network failures can lead to significant interruptions in internet services,resulting in enormous losses.This sets an extremely high bar for the stability and reliability of the optical network.To enhance the sensing,

272、monitoring,and optimization capabilities of complex optical networks,its imperative to establish an intelligent optical network.A knowledge and data-driven digital twin system at the physical layer will be its foundational pillar.Digital twin technology creates multi-dimensional,multi-disciplinary,a

273、nd multi-physical-quantity dynamic virtual models of physical entities.These models simulate and depict the status,behaviors,and rules of physical entities in real-world conditions.As a comprehensive technology that integrates data,models,algorithms,and multiple disciplines,digital twins bridge the

274、physical and digital worlds,offering effective means for their interaction and integration.Distinct from the static modeling of the traditional optical network physical layer,digital twins synchronize and map each physical component and transmission link based on real-time data from sensing units.Th

275、is offers precise real-time key physical layer information and dynamic mapping models for network control.Based on this foundation,the system can monitor,simulate,extrapolate,analyze,and optimize automatically throughout its entire lifecycle.The digital twin system tailored for SGION requires breakt

276、hroughs in ubiquitous sensing,dynamic modeling,and automatic optimization:Ubiquitous Network Status Sensing:The data aspect is foundational for digital twins,demanding comprehensive data across all elements and life cycles.Only with data gathered from the physical space can a numerical model be cons

277、tructed and operational in the digital space.Optical networks can collect massive amounts of diverse data,from the physical layer to the network layer,encompassing historical data,initial data,real-time updates,and other associated data.However,the distinct characteristics,operational methods,storag

278、e mechanisms,and processing algorithms of these data need to be harmonized.As such,data fusion 34 The 6th Generation of Fixed Network White Paper V1.1 technologies are essential to synthesize,filter,and analyze diverse data sources,ensuring uniformity,standardization,and compatibility.High-fidelity

279、Mirror Modeling:The mirror model lies at the heart of the digital twin system,establishing near real-time connections between the physical and digital realms.To ensure an open,decoupled optical network operates healthily,stably,and efficiently,multi-dimensional coordinated modeling of optical device

280、s and transmission systems is required.Data-driven grey-box twin models can bridge the accuracy issues of traditional models(white-box)and the generalization issues of machine learning models(black-box).These models should be designed considering the characteristics of optical fiber links and should

281、 encompass key modules like fibers,optical amplifiers,wavelength-selective switches,and optical transceivers.By merging traditional models based on unique physical properties with machine learning models,we can achieve high precision and generalization.Moreover,to meet the demands of network control

282、 speeds,model complexity should be reduced.Optimal compromises between complexity and accuracy are vital.Automatic Network Performance Optimization:The optimization strategy is the functional application of digital twins to enhance network performance and ensure stable operation.As optical transmiss

283、ion is dynamic,real-time,precise optimization capabilities are often lacking in current systems.Hence,the digital twin system must smartly formulate precise,matched optimization strategies in the digital space using the twin model and feed them back to the physical space for system optimization.The

284、strategies should be built on continuously updated mirror models,with online learning potentially utilizing transfer learning algorithms to dynamically and real-time update the models.Furthermore,by employing time-series analysis techniques,future system performance can be extrapolated.Ultimately,wi

285、th the constantly updated mirror models as a foundation,intelligent control systems can formulate precise feedback strategies,optimizing optical transmission systems in a cost-effective,efficient,and intelligent manner,maximizing the potential of SGION.3.4.Sensing Technologies 3.4.1.Integrated Sensi

286、ng and Communication In SGION,the large-scale deployment of sensing and communication equipment introduces significant device and spectrum resource overhead.To achieve an efficient and simplified optical network and maximize the utilization of hardware and spectrum resources,35 The 6th Generation of

287、 Fixed Network White Paper V1.1 promoting communication-sensing integration technology is a key element.Through the sharing of hardware,spectrum,signal processing,and nodes for sensing and communication,the integrated network can further enhance coverage capabilities,transmission efficiency,security

288、,and intelligence levels.Key technologies required for communication-sensing integration in the context of SGION include multimodal optical sensing,optical transmission for multimodal information,and the design of communication-sensing integrated systems.Multimodal Optical Sensing:This technology em

289、ploys optical methods to perceive and process various types of information such as images,depth,spectra,polarization,and more.Multimodal information optical sensing technology enhances the quality and dimension of sensory data,improving the understanding and redisplay of scenes.It provides new solut

290、ions for fields like cloud services,holographic communication,intelligent interaction,remote sensing,and more.To meet the demand for efficient and fast multimodal sensing methods,research focuses on new information acquisition theories,designing hybrid sensing methods based on single or multiple sen

291、sors to achieve rapid and high-quality multimodal information optical sensing.Additionally,to fulfill the requirement for accurate reconstruction of various information,data-driven approaches are explored,and deep learning-based network models are designed to achieve high-quality and rapid reconstru

292、ction of multidimensional information.Multimodal Optical Transmission:This entails employing lasers as the information carriers to achieve high-speed,secure,and low-latency transmission of multimodal data through space or optical fibers.To meet the demand for efficient multimodal transmission,high-p

293、erformance,low-complexity,and scalable communication-sensing integration coding modulation and signal processing methods are designed.Additionally,adaptive or machine learning-based channel impairment compensation algorithms are proposed to improve the service transmission capacity and transmission

294、distance of optical transmission systems.Sensing and Communication Integration:By sharing hardware,spectrum,signal,or node,an integrated system with multimodal information optical sensing and transmission functions is designed to reduce the cost and power consumption of the integrated optical networ

295、k.According to the commonness of sensing and communication for hardware requirements,reasonable and reliable hardware architecture and layout are designed to realize the functional reuse of sensing and communication.According to the performance requirements of different application scenarios,a syste

296、m architecture suitable for sensing and communication is designed based on the analysis of spectrum efficiency,transmission distance,sensing resolution,and other indicators.36 The 6th Generation of Fixed Network White Paper V1.1 3.4.2.Networked Intelligent Sensing SGION will achieve seamless global

297、communication coverage,merging satellite and ground networks to provide high-speed intelligent services to users.With the continuous improvement of communication frequency bands and the expansion of network scale,F6G faces significant challenges in areas such as security monitoring and network colla

298、borative control.There is an urgent need to establish a widely covered,highly dynamic,distributed network sensing information collection and fusion architecture.It should be based on network-wide shared sensing information to obtain higher security assurance and more intelligent control decisions at

299、 the system level.Intelligent sensing technology can collect real-time network performance data,detect anomalies,and provide warnings,thus reducing network downtime and increasing service reliability.Network intelligent sensing for SGION requires breakthroughs in key technologies for full-spectrum s

300、ensing and decision control.Full-Spectrum Sensing:Full-spectrum sensing technology encompasses the comprehensive sensing and comprehension of the physical world across all dimensions and the entire spectrum.It involves the use of high-precision,multidimensional sensing devices for the multidimension

301、al and multispectral data collection in the target area,coupled with data calibration and encoding procedures aimed at enhancing data quality and transmission efficiency.Leveraging techniques such as multi-task learning,transfer learning,and reinforcement learning,it combines and scrutinizes data fr

302、om various modalities,spectra,and spatial dimensions to unearth essential features and pertinent information,thus enabling precise identification and comprehension of the target area.Moreover,to meet the low-latency requirements of upcoming applications,it is imperative to research low-complexity in

303、tegrated sensing technology for the provision of cost-effective,high-reliability solutions.Distributed Sensing Collaboration:AI play a vital role in supporting distributed intelligent sensing and collaborative control of future networks and achieving the objective of global network condition control

304、.The core of this technology roadmap involves research on high-performance deep learning models,efficient data collection and transmission,and intelligent security guarantees.At the same time,to realize the comprehensive deployment of intelligent collaborative control,it is necessary to reduce the c

305、omplexity of large-scale systems and ensure data privacy and security.3.5.Display Technologies 37 The 6th Generation of Fixed Network White Paper V1.1 3.5.1.Content Acquisition and Processing Three-dimensional holographic communication technology offers users a heightened sense of reality and immers

306、ion.SGION provide high-speed,high-bandwidth,and low-latency data transmission,aligning with the data-intensive and real-time requirements of three-dimensional holographic communication.Three-dimensional holographic communication necessitates initial content acquisition and real-time,efficient conten

307、t processing,followed by display on naked-eye 3D displays through three-dimensional rendering techniques,providing users with an immersive visual experience.The dynamic three-dimensional content essential for three-dimensional holographic display is referred to as volumetric video.Volumetric video a

308、cquisition methods can be categorized into pure color camera arrays(RGB)and depth camera+color camera arrays(RGBD)acquisition.Pure color camera array acquisition employs dozens or even hundreds of color cameras to capture individuals and performances from multiple angles,often utilizing a green scre

309、en for subsequent data extraction convenience.During shooting,a time controller synchronously triggers the camera array.Depending on application scenarios and requirements,color camera arrays can be further classified as partial surround or 360 surround.As opposed to using pure color camera arrays,t

310、he prevailing approach presently incorporates depth cameras alongside color camera arrays to enhance the precision and detail redisplay of generated three-dimensional human data.Notably,this results in more distinct three-dimensional effects in facial features,enabling the clear depiction of details

311、 like nose height and lip contours.Three-dimensional reconstruction algorithms can be categorized into two major classes based on the two acquisition methods,RGB array,and RGBD array:passive reconstruction using pure color camera arrays and active reconstruction using depth cameras in conjunction wi

312、th color cameras.Passive 3D Reconstruction:It directly relies on 2D image information without the need for emitting signals to reconstruct objects.These passive algorithms entail the intricate task of precise disparity calculation and stereo-matching to recover three-dimensional information,making t

313、hem computationally intensive.They encounter significant challenges when dealing with regions affected by occlusion and shadows.Passive three-dimensional reconstruction algorithms,such as Structure from Motion(SfM),primarily focus on the reconstruction of point clouds.SfM is an automated offline cam

314、era calibration algorithm that takes a series of unordered image sets as input and estimates camera parameter matrices,producing sparse point clouds as output.Given that the point clouds obtained by SfM are sparse,further processing,38 The 6th Generation of Fixed Network White Paper V1.1 such as the

315、 Multi-View Stereo algorithm,is necessary to convert them into dense point clouds.Active 3D Reconstruction:It involves emitting signals toward objects using sensors and reconstructing the objects by analyzing the returned signals.These active algorithms require high-performance capture devices to ob

316、tain precise depth information,as noise and errors in in-depth data can impact the results of three-dimensional reconstruction.Representative active three-dimensional reconstruction algorithms include structured light and Time-of-Flight(TOF).Taking the example of infrared structured light,it relies

317、on an infrared projector to project encoded infrared light onto the object being captured.An infrared camera then captures the changes in the encoded infrared light on the object,which are transformed into depth information to obtain the three-dimensional contour of the object.The TOF method continu

318、ously sends light pulses toward the target using a projector and calculates the distance to the target based on the time or phase difference of the received backscattered light.Active algorithms such as structured light and TOF can accurately construct 3D models,but both require relatively precise s

319、ensors.3.5.2.3D Rendering and Display The large-scale image data acquired by capture devices,efficiently transmitted via an SGION,ensures data quality and low latency,laying the foundation for subsequent content processing and rendering.Following algorithmic content processing,the generated data mod

320、els are presented on display devices using rendering techniques.Rendering methods primarily encompass multi-view stereoscopic rendering technology and multi-plane image technology.Multi-view stereoscopic rendering technology is predominantly utilized in image rendering for virtual reality(VR)devices

321、.When images are presented to the human eye through VR headsets or similar devices,the quality of the displayed content significantly influences the users viewing experience.In these devices,graphics hardware manufacturers continually strive to enhance aspects such as field of view,distortion reduct

322、ion,and graphic quality,introducing a series of technologies and solutions.Multi-plane image rendering technology is a method for rendering complex,real-world scenes based on image rendering environments.It is particularly effective when rendering challenging scenes with occlusion or mirror-like ref

323、lections,as compared to traditional 3D grid rendering.Multi-plane images(MPI)can represent geometric shapes and textures,including occluding elements.They can also handle partially reflective or transparent objects and soft boundaries using alpha channels.Increasing the number of planes allows for a

324、 broader depth range in MPI redisplay and enables more significant camera 39 The 6th Generation of Fixed Network White Paper V1.1 movement.Additionally,generating new viewpoints from MPI rendering is highly efficient and supports real-time applications.Future mainstream naked-eye holographic display

325、 technologies include volumetric three-dimensional technology based on the reconstruction of three-dimensional light fields in space and light field stereoscopic display technology.Volumetric 3D Display:It is a novel technique for presenting three-dimensional images.It involves stimulating materials

326、 located within the display space in a controlled manner,resulting in the creation of numerous volume pixels(voxels)through the generation,absorption,or scattering of visible radiation.However,most existing applicable volumetric three-dimensional display technologies rely on mechanical screen format

327、ion methods,such as vibration or rotation.The high-acceleration mechanical components associated with these methods endure significant stress and are prone to safety incidents,necessitating robust protective enclosures.Volumetric three-dimensional display technology presents images that resemble rea

328、l three-dimensional objects,aligning with the characteristics of how humans perceive conventional three-dimensional images.It can provide multi-user,multi-angle,naked-eye viewing simultaneously.Light Field 3D Display:It utilizes directional beams of light to construct the light field of spatial thre

329、e-dimensional objects.Any three-dimensional object in space can be considered as composed of an infinite number of luminescent points,each emitting light rays carrying their unique characteristics in various directions within the space.By designing the structure of light-control units and systematic

330、ally encoding images loaded on 2D display devices,the direction of light emitted from the controlled light units,carrying three-dimensional scene information,is modulated to converge in space.This creates and builds volume pixels projecting distinct spatial information in different directions.Howeve

331、r,single-layer light-control units are challenging to effectively eliminate imaging aberrations.Multiple-layer stacking of light-control units is required to control imaging aberrations,reducing interference between presented volume pixels.These volume pixels simulate the luminescent points of real

332、objects,providing a more realistic and natural 3D image to the human eye.40 The 6th Generation of Fixed Network White Paper V1.1 4.F6G Applications 4.1.Any-time Any-where Connectivity With the advent of the era of IoT,information communication networks are constantly expanding in temporal and spatia

333、l dimensions.The anytime anywhere access network will become a critical infrastructure under future international competition.As shown in Fig.9,ubiquitous optical connectivity is a core application scenario for future F6G networks.It serves as the foundation for realizing the Internet of Everything.The system employs terrestrial networks,airborne networks,and space-based networks(terrestrial-air-s