1、1/120Executive SummaryWith the flourishing development of ground cellular communication technology,from 4G changing life to 5G changing society,ground mobile communication hasachieved fruitful results.However,due to the difficulty and cost of construction,80%of the land area and over 95%of the ocean

2、 area have not been able to achieve groundmobilecommunicationnetworkcoverage.Satellitecommunicationhastheadvantages of wide coverage and no limitations of terrain environment,which canprovide communication services for remote areas and effectively make up for the lackofterrestrialnetwork.Researching

3、theintegrationofsatelliteandgroundcommunication technology to form an integrated space-ground communicationsystem is a common demand for satellite communication and ground cellularcommunication.3GPP(3rdGenerationPartnershipProject,3GPP)officiallyintroduced Non Terrestrial Networks(NTN)as a supplemen

4、t to ground networks inRelease 17,and conducted further research and standardization work on 5G NTN.The freezing of 5G NTN standards has attracted high attention from the globalindustry,with research institutes,operators,equipment companies,chip companies,terminal companies,etc.actively conducting r

5、esearch and verification work on 5GNTN technology.In addition,as one of the pillar technologies and basic networkforms of 6G,the integrated space-ground aims to meet the needs of wide areaintelligent connection and global ubiquitous seamless access in ten years,establishintelligent connections for w

6、ide area objects,provide intelligent services,and provideglobal uninterrupted and consistent information services for humanity.This white paper mainly elaborates on our exploration and practical thinking onthe integrated air-space-ground communication system from six aspects,includingrequirements an

7、d vision,current development status of satellite communication andground cellular communication,key technologies of integrated space-ground based on5G NTN,development and practice of integrated air-space-ground industry based on2/1205G NTN,practical difficulties in integrated space-ground engineerin

8、g,and foresightfor the development of 6G integrated space-ground.(1)The demand and vision for integrated space-ground communicationSatellite communication has the characteristics of wide coverage,stronganti-interference ability,and flexible deployment,which can compensate for theshortcomings of grou

9、nd networks in coverage.Therefore,integrating groundnetworks and satellite communication can achieve an integrated space-groundcommunication system,providing users with higher quality,more reliable,and moreintelligent services.Driven by both industry demand and technological development,the integrat

10、ion of satellite communication and ground communication has become themainstream direction for the evolution of future mobile communication systems.Thefuture mobile communication system will integrate different levels such as services,spectrum,and system to build an integrated space-ground communica

11、tion system,achieving seamless three-dimensional coverage worldwide.(2)Current development status of satellite communication and ground cellularcommunicationSatellite communication has gone through four stages of development:satellitetesting,analog communication,digital communication,and broadband s

12、atellitecommunication.The rapid development of new satellite communication technologiessuch as multi beam antennas,onboard processing,and inter satellite links,as well asthe emergence of high-throughput and low orbit satellite giant constellations,haveushered in a new era of satellite communication.

13、For ground cellular communication,after more than 40 years of explosive growth,it has now penetrated into various fieldsof peoples lives and become one of the important driving forces for socialdevelopment.(3)Key Technologies of integrated space-ground based on 5G NTNThe key technologies for the int

14、egrated space-ground based on 5G NTN mainlyinvolvenetworkarchitecture,wirelesstransmissiontechnology,satelliteimplementationtechnology,terminalimplementationtechnology,andtestingtechnology.For network architecture,communication nodes are not limited to land,3/120but satellite nodes will play an incr

15、easingly important role,and the payload and signalprocessing capabilities of satellites will gradually improve.In addition to achievingtransparent forwarding and integrated networking with ground base stations,it alsoadds on board processing functions for base stations and core network;Wirelesstrans

16、mission technology mainly includes:time-frequency synchronization,timingmanagement,and mobility management technology,etc.;Satellite implementationtechnology mainly includes:satellite borne multi-beam antenna,satellite borne poweramplifier,inter satellite link technology,etc.;The terminal implementa

17、tion technologymainly includes antenna and RF front-end integration technology.(4)The development and practice of 5G NTN based integrated space-groundindustryThe development and practice of the 5G NTN based integrated space-groundindustry involve the industry chain,standard formulation,application s

18、cenarios,andpractical activities.Among them,the industrial chain includes satellite platforms,network equipment,terminals and applications,testing instruments,as well asservices and operations.For standard formulation,there are currently mainly 3GPPand the China Communications Standards Association(

19、CCSA)promoting theevolution of 5G integrated technologies from the standard level.The applicationscenarios mainly include direct connection of mobile phones to satellites,the Internetof Things,the Internet of Vehicles,and broadband access.For practical activities,major domestic and foreign operators

20、,research institutes,network equipmentmanufacturers,and chip terminal manufacturers have successively carried out NTNproduct research and testing to accelerate the landing of NTN products and promotethe integrated space-ground technology and industry.(5)Practical difficulties in the integrated space

21、-groundThe practice of the integrated space-ground engineering is a prerequisite for thecommercialization of the integrated space-ground.Considering the characteristics ofthe integrated space-ground,such as the dynamic changes of network nodes and largetransmission delays,the engineering practice of

22、 the integrated space-ground facesmany difficulties and challenges,mainly including:4/120-Rich communication scenarios,complex models,and difficult scale testing-Satellite communication and ground communication systems are vastlydifferent and difficult to communicate with each other-There are signif

23、icant differences in services management and operationmechanisms,and there are significant challenges in integrating operations(6)Foresight on the development of 6G integrated space-ground5G NTN can fully utilize the rich industrial chain foundation of ground networksto improve research and developm

24、ent efficiency,but there are still shortcomings suchas low interconnection and network collaboration efficiency,which have not trulyachieved the integrated design of NTN and TN.In the future,research on 6Gintegrated space-ground needs to be carried out from hardware technology,networktechnology,new

25、access technology,network security technology,and other aspects tomeet the needs and vision of 6G integrated space-ground.Hardware technologymainly includes satellite antenna technology,satellite processing capability,terminalantenna and RF technology,etc.Network technology mainly includes new netwo

26、rkarchitectures and networking technologies.New access technologies mainly include:waveform/modulation/multiple access technology,beam management technology,inter satellite cooperation technology,satellite ground cooperative transmissiontechnology,mobility enhancement,etc.5/120ContentsExecutive Summ

27、ary.11.Preface.72.Demands and Vision for Integrated Space-Ground Technology.92.1 Demands.92.2 Vision.103.Development Status of Integrated Space-Ground Network.113.1 Satellite Communication.113.1.1 Satellite Communication Systems.123.1.2 Satellite Communication Standards.203.1.3 Technical Paths of Sa

28、tellite Communication Systems.213.1.4 Operations of Satellite Systems.253.2 Ground Communication Standards.264.Key Technologies for Integrated Space-Ground Networks Based on 5G NTN.294.1 Network Architecture.294.2 Air Interface Transmission Technology.314.2.1 Synchronization Technology.314.2.2 Timin

29、g Management.334.2.3 Coverage.344.2.4 System Throughput Enhancement Technology.364.2.5 Beam Management.374.2.6 Mobility.394.3 Security Technology.404.4 Satellite Implementation Technology.414.5 Terminal Implementation Technology.454.6 Testing Technology.495.Development and Practice of Integrated Spa

30、ce-Ground Industry based on 5G NTN.515.1 5G Integrated Space-Ground Industry Chain.515.1.1 Satellite Platform.525.1.2 Network Equipment.545.1.3 Terminals and Applications.575.1.4 Testing Products.595.1.5 Integrated Space-Ground 5G Services and Operations.625.2 Integrated space-ground standards in 5G

31、.635.3 Integrated Space-Ground 5G Application Scenarios/Instances.665.3.1 Direct Connection between Mobile Phones and Satellites.675.3.2 Internet of Things.685.3.3 Internet of Vehicles.695.3.4 Broadband Access.695.4 Practical events of integrated space-ground in 5G.706.Practical Problems of Integrat

32、ed Space-Ground Engineering.766.1 Satellite Communication and Ground Communication Systems are Very Different andDifficult to Interconnect.766/1206.2 The Communication Scenario is Rich,the Model is Complex,and the Scale Test is Difficult776.3 Service Management Operation Mechanism is Different and t

33、he Integration Operation isDifficult.777.Forecast for the Development of Integrated Space-Ground 6G.787.1 5G NTN Limitations.797.2 Core Issues of Integrated Space-Ground 6G.807.3 Key Technologies of Integrated Space-Ground 6G.827.3.1 New Network Architecture.827.3.2 New Access Technologies.837.3.3 E

34、dge Collaboration Computing Technologies.947.3.4 Integration of Sensing and Communication.997.3.5 Network Safety.1017.3.6 Satellite Technology.1027.3.7 Terminal Technology.1037.3.8 Testing Technology.1047.4 Evolution Route Forecast of Integrated Space-Ground 6G Technology.1077.5 Forecast of Integrat

35、ed Space-Ground 6G Business Mode.1098.Summary.111Abbreviations.112References.114Acknowledgment.1197/1201.PrefaceAt present,research has been conducted in the industry on integratedspace-groundcommunicationtechnologies.3GPP hasincludednon-terrestrialnetworks(NTN)as a supplement to terrestrial network

36、s in its 5G network standard.Itactively promotes the formulation of technical specifications in 5G NTN networkarchitecture,air interface transmission technology,security technology,and otherrelated fields,and released the first 3GPP NTN standard in 2022.On one hand,satellite-borne multi-beam phased

37、array antennas,satellite-borne power amplifiers,inter-satellite links,and on-board fault-tolerant redundancy and other technologies arematuring.On the other hand,intensive research on low-cost phased array antennas,radio frequency(RF)integration,and energy-saving solutions for terminals isunderway.R

38、esearch institutes,operators,equipment companies,chip companies,terminalcompanies,and other organizations in the industry are actively carrying out fieldtesting and validation on 5G NTN.Several field validations on IOT-NTN satellitecommunication based on R17 IOT-NTN technology have been carried out,

39、whichverifies the technology implementation capabilities from architecture,protocols,equipment,services(including short messages and voice talk),and other aspects.NR-NTN technical validations are expected to be conducted in 2024 on a large scale.Integrated space-ground communication is developing ra

40、pidly though,it is alsofacing a series of engineering implementation problems.For example,it is difficult toconduct a large-scale test of all functions with too many use scenarios,complexmodels,and a long satellite launch cycle;It is difficult to support terminals in roamingand interactive communica

41、tion between different networks since the technicalstandards of satellite communication and terrestrial communication are quite different;It is difficult to build an integrated operation support system in service activation andmanagement since the operation systems of satellite communication and ter

42、restrialcommunication are very different.All this restricts the implementation of integratedspace-ground communication.8/120The 6G Recommendation of the International Telecommunication UnionRadiocommunications sector(ITU-R)expands the three major application scenarios of 5Ginto the six major applica

43、tion scenarios of 6G to cover all application scenarios.Inaddition to continuing to enhance and develop the original application scenarios of 5G,including immersive communication,ultra-reliable and low-latency communication,and large-scale communication,it also proposes to spawn new application scen

44、arios,including integrated sensing and communication,integrated AI and communication,and ubiquitous connectivity,to improve production efficiency and quality of life.Among such scenarios,ubiquitous connectivity needs to be based on integratedspace-ground technology.In other words,integrated space-gr

45、ound technology is oneof the pillar technologies and characteristic technologies of 6G in the future.9/1202.Demands and Vision for Integrated Space-Ground Technology2.1 Demands5G and satellite communications are two hot topics in the communications sectornow.5G features high speed,low latency,and hi

46、gh connection density,so it can meetthe requirements of various application scenarios.However,limited by factors such asgeographical environment and base station construction,it is difficult to cover vastlands and seas.In the future,intelligent systems,such as autonomous vehicles,unmanned logistics

47、systems,and remotely operated robots,will be widely deployedaround the world and play an important part in production and life1.By then,information interaction and collaborative work between these intelligent systems willbe common scenarios.However,due to limited coverage capabilities,5G terrestrial

48、communication systems is difficult to provide effective network services forwide-area intelligent systems to work collaboratively.Satellite communicationfeatures wide coverage,strong anti-interference ability,and flexible deployment,making up for 5G terrestrial communications shortcomings in coverag

49、e.However,limited by the satellites orbital altitude,spectrum resources and other factors,satellitecommunication is difficult to provide high-speed and low-latency services.Therefore,the integration of 5G and satellite communication enables an integrated space-groundcommunication system.Providing us

50、ers with better,smarter,and more reliableservices is the evolution trend of 5G and satellite communication technologies in thefuture.It is widely expected that after 2030,more consumers and more versatile deviceswill be connected to the information network in a new and smarter way.Terrestrialwireles

51、s networks,terrestrial wired networks and satellite networks will be deeplyintegrated to form the 6G mobile information network.The industry has reached apreliminary consensus on the typical characteristics of 6G,such as ubiquitousinterconnection,multi-dimensional sensing,full-area coverage,being gr

52、een andlow-carbon,and endogenous security.With the confirmation of ITU-Rs 6GRecommendation,designprinciplesof6Gareformallyproposed,suchas10/120sustainability,security,privacy,flexibility,ubiquity,intelligence,etc.Based on thesetypical characteristics and design principles,it can be predicted that 6G

53、 will be anevolutionary version of 5G,inherit and amplify the advantages of 5G,and integratewith other technologies to create a universal network2.As a major national scientific and technological innovation project,theintegrated space-ground information network is included in both the Outline of the

54、13th Five-Year Plan for National Economic and Social Development of the PeoplesRepublic of China and the National 13th Five-Year Scientific and TechnologicalInnovation Plan,and is listed among the new major projects of Sci-Tech Innovation2030.In addition,together with quantum communication,brain sci

55、ence,and deep-seaspace stations,it is also one of the first major projects launched by the Ministry ofScience and Technology during the 13th Five-Year Plan period.2.2 VisionDriven by industry demands and technological development,the integration ofsatellite communication and terrestrial communicatio

56、n has become the mainstreamdevelopment direction of the future mobile communication system.The future mobilecommunication system will integrate at different levels such as application,technicalsystem,spectrum,and system to build an integrated space-ground communicationsystem for global seamless thre

57、e-dimensional coverage.Asanimportantfeatureofthe6Gnetwork,integratedspace-groundcommunication aims to meet the needs of wide-area smart connectivity and globalubiquitous seamless access in ten years,so as to establish smart connectivity forwide-area objects,offer smart services,and provide uninterru

58、pted and consistentinformation service globally.Theintegratedspace-groundcommunicationsystemhasthreetypicalcharacteristics1:(1)Unified network architecture and interface protocol:Under a unified logicalarchitectureandimplementationarchitecture,satellitecommunication,spacecommunication and terrestria

59、l communication are integrated with the design,and11/120network functions are divided flexibly and reconstructed smartly,so the system canadapt to the limited satellite payload resources and dynamic changes in applicationneeds.(2)Unified air interface technology:Satellite communication and terrestri

60、alcommunication use air interface transmission technology under the same framework,so terminals can be connected in a minimalist and smart way.(3)Unified smart management and control:Through unified scheduling andcontrol of system resources,networks can be optimized globally,and green resourcescan b

61、e intensified.Thefutureintegratedspace-groundcommunicationnetworkwillbeathree-dimensional,hierarchical,integrated and collaborative network based onterrestrial networks and expanded by air-based networks and space-based networks.With satellite constellations(including those in high,medium,and low Ea

62、rth orbit),near-space platforms(such as hot air balloons and UAVs)and terrestrial nodes jointlyoffering multiple layers of coverage,the system is typified by heterogeneity,as shownin Figure 2-1.Figure 2-1 Schematic Diagram of the Integrated Space-Ground CommunicationNetwork3.Development Status of In

63、tegrated Space-Ground Network3.1 Satellite CommunicationSatellite communication uses satellite systems for information transmission,andrealizes wide-area coverage,long-distance transmission,and global connectivity.12/120Satellitecommunicationisimplementedbasedonsatelliteplatformsandcommunication pay

64、loads.Satellites in different orbital altitudes orbit at differentspeeds around the Earth,with different communication propagation losses andcommunication delays,so they can provide differentiated communication services tomeetthecommunicationneedsofdifferentapplicationscenarios.Satellitecommunicatio

65、nhasdevelopedthroughfourstages:satellitetesting,analogcommunication,digital communication,and broadband satellite communication.Withthe rapid development of new satellite communication technologies,such asmulti-beam antennas,on-board processing,and inter-satellite links,high-throughputLEO mega-const

66、ellations have emerged one after another,marking that the satelliteInternet has entered a new era.Countries around the world are actively researchingand building satellite systems.In terms of technical standards,GMR-1,S-UMTS,DVB-S/S2/RCS,Surfbeam2,3GPPNTNandothersatellitecommunicationtechnology stan

67、dards have been formed,and the integrated space-ground technologystandard is evolving;In terms of satellite system construction,China and othercountries have built and operated many satellite systems,such as Inmarsat,GlobalStar,Iridium,Starlink,OneWeb,Jupiter,Tiantong,and ChinaSat,to meet the satell

68、itecommunication needs of different scenarios.3.1.1 Satellite Communication Systems(1)Introduction to existing satellite communication systemsSatellite communication systems usually consist of three parts:the spacesegment,ground segment,and application segment.As shown in Figure 3-1,thespace segment

69、,consisting of one or more communication satellites,processes orforwards and amplifies signals;the ground segment mainly includes the gatewaystation,measurement and control station,operation control center,etc.;the applicationsegment comprises various types of connected satellite terminals and appli

70、cations.13/120Figure 3-1 Schematic Diagram of Satellite Communication SystemAccording to the satellites orbital altitude,satellite communication systems canbe divided into Geostationary Earth Orbit(GEO)satellite communication systems,Medium Earth Orbit(MEO)satellite communication systems,and Low Ear

71、th Orbit(LEO)satellite communication systems.The GEO satellite remains in a fixed positionrelative to the Earths surface,a single satellite can cover a large area.The GEOsatellite communication system can provide a communication rate of several hundredsKbps to meet the needs of voice messages,SMS,da

72、ta transmission,fax,and otherservices.In recent years,with the development of high-throughput satellites(HTS),beam hopping and other technologies,the GEO satellite communication system hasbeen enhancing its service capabilities.MEO satellites orbit between GEO orbit andLEO satellites orbits,so their

73、 communication transmission loss and delay are alsobetween those of GEO and LEO.At present,the typical MEO communication systemapplications are global navigation and positioning systems,such as the GlobalPositioning System(GPS)and the BeiDou Navigation Satellite System(BDS).LEOsatellites orbit at th

74、e lowest altitudes,so they have a short communicationtransmission distance,low communication transmission loss and delay,making iteasier to meet the needs of real-time communication and compact terminals.The LEOsatellite communication system can provide a communication rate of 50 to 500 Mbpsand an a

75、ir interface delay of several to a dozen milliseconds,and thus has become ahot research subject in the satellite communication field.14/120Table 3-1 Parameters of Satellites at Different AltitudesSatellite TypeOrbitalAltitude/kmTypical DelaySingle SatelliteCoverageGEO satellites36,000Hundreds ofmill

76、isecondsBigMEO satellites2,00036,000Tens of millisecondsMediumLEO satellites4002,000Millisecond levelSmallSatellite communication has developed through four main stages.The first stageis the experimental communication satellite stage before the 1980s,with typicalsatellite systems such as Sputnik-1 s

77、atellite and EarlyBird satellite.The second stageis the analog communication stage from 1980 to 1990,when GEO satellite systemswere mainly developed with global beams and a small single-satellite communicationcapacity,with typical systems including Inmarsat-1 and Inmarsat-2 satellites.Thethird stage

78、 is the digital communication stage from 1990 to 2000,when LEO satellitesystems emerged to provide narrow-band communication service,with typicalsystems including GlobalStar and Orbocomm.In this stage,the GEO satellitecommunication system used regional beams,frequency reuse and other technologiesto

79、increase single-satellite communication capacity,with typical systems includingInmarsat-3 satellites.The fourth stage is the broadband communication stage after2000,when new satellite communication technologies,such as multi-beam antennas,on-boardprocessing,andinter-satellite links,have beendevelopi

80、ngrapidly,high-throughput LEO mega-constellations are emerging one after another,and GEO,MEO,and LEO collaborative networking is underway,marking that the satelliteInternet has entered a new era.(2)Foreign satellite communication systemTypical constellations developed by foreign countries include In

81、marsat,Thuraya,Viasat,Iridium,Globalstar,OneWeb,Starlink,etc.15/120Table 3-2 Parameters of Different Foreign Satellite SystemsConstellationOwnerOrbitalAltitudeSatellitesin OrbitMaximumSingle SatelliteCapacityCommunicationStandardInmarsatInternationalMaritimeOrganization(IMO)GEO94.5 GbpsSL/S-UMTSThur

82、ayaUAEGEO313,750 channelsGMRViasatUSGEO2300 GbpsSurfbeamIridiumUS700 km66960 channelsPrivateGlobalStarMultiplecountries1,414 km562,800 channelsPrivateOnewebUK1,200 km61810 GbpsDVBStarlinkUS550 km387520 GbpsDVBThe Inmarsat satellite system is the earliest GEO satellite mobile communicationsystem.Mana

83、ged and operated by Inmarsat,it mainly provides global maritimesatellite communication service.The Inmarsat satellite system has evolved throughfive generations,with 9 satellites in orbit(including 5 spare satellites).The satellitescurrently in use are the third,fourth and fifth generations.The thir

84、d-generationsatellites are equipped with 1 global beam and 7 wide spot beams in the L frequencyband.The fourth-generation satellites are equipped with 1 global beam,19 wide spotbeams and 228 narrow spot beams.The fifth-generation satellites adopt spot beammode,including 72 fixed beams and 6 mobile b

85、eams,with a single satellite capacityof 4.5 Gbps.The Thuraya satellite system is operated by Thuraya TelecommunicationsCompany in the United Arab Emirates(UAE).It covers the Asia-Pacific region,Europe,Africa,the Middle East and other regions,and provides call and voicemessages,fax,data transmission,

86、SMS,Internet access,GPS positioning and otherservices.The Thuraya satellite system includes three GEO satellites,i.e.Thuraya-1,Thuraya-2 and Thuraya-3.With an antenna diameter of 12.25 meters,Thuraya-3 cangenerate 300 spot beams.With the on-board routing function,the Thuraya satellitesystem supports

87、 direct communication between satellites and phones through fixedphones,mobile phones,and satellite phones inside and outside the system.TheThuraya terminal is the worlds first smart satellite phone that integrates the satellite,GSM,and GPS functions and provides five services:voice messages,SMS,dat

88、a16/120transmission,fax,and GPS positioning,with the maximum shared access rate of 444Kbps and maximum dedicated access rate of 384 Kbps.The Viasat satellite system is jointly launched and operated by Viasat and othercompanies in the US.It covers the Americas,Europe,the Middle East and Africa,andpro

89、vides on-board WiFi service for commercial airplanes.The Viasat satellite systemincludes Viasat-1,Viasat-2,Viasat-3 and other satellites.Viasat-1 has a throughput of140 Gbps.Viasat-2 has a satellite capacity of 300 Gbps.ViaSat-3 consists of 3satellites,with a single satellite capacity of up to 1 Tbp

90、s.The first satellite waslaunched in 2023.As planned,the first two satellites will cover the Americas andEurope,the Middle East and Africa respectively,and the third satellite will cover theAsia-Pacific region,thus achieving global coverage.The Iridium satellite system is launched and operated by Ir

91、idium in the US.It isthe worlds first large-scale LEO mobile communication satellite system forcommercial use.The Iridium satellite system consists of 66 satellites in 6 orbits,witheach satellite weighing about 700 kg and orbiting at an altitude of about 780 km.Itcan provide voice messages,paging an

92、d data transmission for personal mobile phones,enablinghandheldsatellitecommunicationterminalsandglobalpersonalcommunication.The Globalstar satellite system is jointly launched and operated by companies inthe US,South Korea,the UK,Germany,Italy,France,and other countries.It consistsof 48 satellites

93、in 8 low-earth orbit planes,with a typical orbital altitude of 1,414 km,achieving full coverage between 70 degrees north and south latitudes of the Earth.Compatible with fixed networks and mobile networks,the Globalstar satellite systemcan provide services including call and voice messages,fax,data

94、transmission,SMS,positioning,etc.The OneWeb satellite system was proposed by OneWeb in the UK.According tothe plan,2,648 satellites will be launched in three stages.In the first stage,648Ku/Ka-band satellites will be launched in 18 orbits,with about 40 satellites deployedin each orbit at an altitude

95、 of about 1,200 km.With a constellation capacity of 7 Tbit/s,they can provide broadband service with a peak rate of 500 Mbit/s and a satellitedelay of about 50 ms.In the second stage,720 V-band satellites will be added at thesame orbital altitude,and the constellation capacity will reach 120 Tbit/s.

96、In the thirdstage,1,280 V-band satellites will be added in MEO orbits,with the constellation17/120capacity reaching 1,000 Tbit/s.Data shows that 618 satellites have been in orbit,providing a network speed of 50 Mbps and a latency of 20 ms.The Starlink satellite system is proposed by Space X in the U

97、S and is planned tobe deployed in two stages.In the first stage,4,408 LEO satellites and 7,518 VLEOsatellites will be launched.The LEO satellites orbit at an altitude of 550 km and usethe Ku and Ka frequency bands,with a single-satellite communication capacity ofabout 20 Gbps and an overall data thr

98、oughput of about 100 Tbps.The VLEO satellitesorbit at an altitude of 340 km and use the Ku,Ka and V frequency bands.In thesecond stage,about 30,000 satellites using the Ku,Ka,V,and E frequency bands willbe launched,with the bandwidth increased by three times to further improve systemcapacity.Data sh

99、ows that Starlink has more than 5,000 satellites in orbit and hasservices implemented in 36 countries.(3)Chinese satellite communication systemAfteryearsofdevelopment,Chinahasformedacompletesatellitecommunication industry chain and built many satellite communication systems.ThetypicalsystemsincludeT

100、iantong,ChinaSat,Tianqi,BeiDou,GlobalHTSCommunication System(APSTAR-6D),Geely Future Mobility Constellation,andGW.Table 3-3 Parameters of Different Chinese Satellite SystemsConstellationOrbital AltitudeSatellitesin OrbitMaximum SingleSatellite CapacityTechnicalStandardTiantongGEO3/GMR-1ChinaSatGEO3H

101、undreds of GbpsDVBTianqiGEO+LEO16/GMR-1BeiDouGEO+MEO55540,000 users/hourGMR-1APSTARGEO150 GbpsDVBFutureMobilityLEO9/GMR-1GWLEO/The Tiantong satellite system,operated by China Telecom,consists of three GEOsatellites(Tiantong-1 01,02,and 03).Tiantong-1 is a satellite mobile communicationsystem indepen

102、dently developed and built by China,with the user beam in the Sfrequency band and the Feed beam in the C frequency band.It covers Chinas18/120surrounding areas,the Middle East,Africa,the Belt and Road region,and most of thePacific and Indian Oceans.In May 2018,China Telecom officially released the 1

103、740phone number segment of the Tiantong-1 system for commercial use in QinghaiProvince.The Tiantong-1 satellite system can provide SMS,voice messages and dataservices for individuals,with terminal products including Tiantong+4G dual-modemobile phones,Tiantong single-mode mobile phones,Tiantong+AIS d

104、ual-modemobile phones for ships,Tiantong terminals for vehicles,Tiantong terminals forairplanes,Tiantong-1 satellite IoT terminals,etc.The ChinaSat satellite system is operated by ChinaSatcom,with threehigh-throughput satellites,ChinaSat 16,19 and 26,launched.ChinaSat 16 uses the Kafrequency band,wi

105、th a capacity of 20 Gbps and a single beam capacity of 1 Gbps.ChinaSat 19 uses the C,Ku and Ka frequency bands,with a capacity of 10 Gbps and asingle beam capacity of 0.35 Gbps.ChinaSat 26 is the first high-throughput satellitewith a capacity of above 100 Gbps.It uses the Ka frequency band and is eq

106、uippedwith 94 user beams and 11 gateway beams.At present,the ChinaSat satellite systemcan cover the entire territory of China and its surrounding areas,parts of Russia,Southeast Asia,Mongolia,Japan,Indonesia,India,the Indian Ocean,and other areas,and provide broadband access service for fixed termin

107、als,vehicle-mounted terminals,ship-mounted terminals,airborne terminals,etc.The Tianqi IoT satellite system is built and operated by Beijing Guodian Hightech Technology Co.,Ltd.It consists of 38 small satellites weighing about 50 kg,with36 satellites in 6 orbital planes at an altitude of 500-900 km

108、and 2 satellites in GEOorbits.The single satellite coverage of the Tianqi system can reach 2000 km.With 16satellites in orbit now,it has basically achieved global coverage.Mainly for globalIoT satellite applications,the system can collect information once every 1.5 hoursfrom any place in the middle

109、and low latitudes of the Earth.The duration of eachoverhead communication is about 10 minutes.The BeiDou Navigation Satellite System(BDS),built and operated in threestages,is a satellite navigation system independently developed by China.With 45satellites in orbit,it can provide high-precision and h

110、igh-reliability positioning,navigation,and timing services for all types of users around the world day and night,with the positioning accuracyat decimeterand centimeterlevels,a speedmeasurement accuracy of 0.2 m/s,and a timing accuracy of 10 ns.In addition,itoffers short message communication.19/120

111、The Global High-throughput Broadband Satellite Communication System islaunched and operated by APT Mobile Satcom Limited.Among the four GEOsatellites in plan,APSTAR-6D(Shenzhen Star)has already been launched into orbit.APSTAR-6D weighs 5,550 kg and can carry a payload of nearly 1,000 kg.It has moret

112、han 1,200 transponders on board,99 feeds(beams),and more than 1,900 waveguidesin total in and out of the cabin.With 90 Ku-band user beams and 8 Ka-band gatewaybeams,APSTAR-6D has a satellite communication capacity of 50 Gbps and a singlebeam capacity of more than 1 Gbps.With signals covering a wide

113、range of areasincluding Russia,Japan,South Korea,India,Australia,New Zealand,and Hawaii,APSTAR-6D provides high-speed broadband services for airplanes,ships,and remoteareas.The Geely Future Mobility Constellation is operated by Geespace,a subsidiaryof Geely.It plans to launch 72 satellites in the fi

114、rst stage,covering China and theAsia-Pacific region.There are 9 satellites in orbit now,with a single satellite weighingabout 100 kg at an orbital altitude of 600 km.The Geely Future MobilityConstellation mainly aims to meet satellite communication needs in the fields of smarttravel,consumerelectron

115、ics,unmannedsystems,smartcities,environmentalmonitoring,etc.It can provide high-precision positioning,remote sensing,navigation,broadband communication,and other services.The GW satellite system is planned,built,and operated by China SatelliteNetwork Group Co.,Ltd(CSCN),which was established in Apri

116、l 2021.According tothe constellation spectrum application submitted to the ITU by China SatelliteNetwork,12,992 satellites are planned in the mega-constellation,including twoconstellations:GW-A59Q and GW-2.GW-A59Q is planned to be in extremely loworbits at altitudes of below 600 km,including 3 sub-c

117、onstellations with a total of6,080 satellites;GW-2 is planned to be in the low-earth orbit of 1,145 km,including 4sub-constellations with a total of 6,912 satellites.20/120Table 3-4 Information about GW-A59 and GW-2 ConstellationsConstellationOrbitalAltitude(km)OrbitalInclinationNumber ofOrbital Pla

118、nesNumber ofSatellites in anOrbital PlaneNumber ofSatellitesGW-A5959085040502,0005085560603,600Subtotal6,080GW-21,1453048361,7281,1454048361,7281,1455048361,7281,1456048361,728Subtotal6,912Total number ofsatellites12,9923.1.2 Satellite Communication StandardsThe existing satellite communi

119、cation standards mainly include Digital VideoBroadcast(DVB)and GEO-Mobile Radio(GMR).At present,most commercial LEO satellites communication standards are basedonETSIsthirdgenerationdigitalsatellitetelevisionbroadcastingstandard(DVB-S2/S2X)345.DVB-S2 is updated on the basis of DVB to support interac

120、tiveInternet services,which can support Broadcasting satellite service(BSS)and Fixedsatellite service(FSS).However,DVB-S2 cant support mobile satellite service(MSS).DVB does not have mobility management function and core network function,and is similar to the ground fixed wireless access communicati

121、on,and the mobilecommunication service capability is poor.GMR6is used for GEO satellites MSS.GMR is based on the digital cellularstandard GSM and can connect to the GSM core network.GMR has three versions.GMR-1 only supports the circuit domain services of GEO MSS.GMR-2,namelyGPRS-1,is based on GPRS

122、and adds packet domain service on the basis of R1.GMR-3,namely GMR-1 3G,evolved from R2 to 3G and is compatible with UMTS.The GMR protocol is used for Thuraya Satellite Communications System,a regional21/120satellite mobile communications system that provides voice services to theAsia-Pacific region

123、.The existing satellite communication standards have greatly promoted thecommercial use of satellites and the development of satellite technology.However,the existing satellite communication system also has some limitations:(1)The existing standards are difficult to satisfy the requirements of satel

124、liteInternet in the future.DVB-S is mainly aimed at broadcasting service,and lacksupper-layer protocol and user management functions,so it is difficult to support largebandwidth and multi-access satellite Internet service.GMR standard spectrumefficiency is low and cant satisfy large capacity and hig

125、h speed requirements ofsatellite Internet.(2)Standards are incompatible with each other.The satellite industrial scale issmall,and the cost is high,so there is no economy advantage.For the futureintegrated space-ground,the satellite network and ground network should avoidindependent development and

126、competition,and should form a trend of integrateddevelopment and mutual assistance,and gradually become integration.(3)The forms of user equipment are complex and diverse,and it is difficult tounify.There are various forms of satellite communication equipment at home andabroad,and the standards adop

127、ted by user equipment in different countries are alsodifferent.It is urgent to formulate relevant standards to promote the consistency ofsatellite communication user equipment.3.1.3 Technical Paths of Satellite Communication SystemsSatellite communication technology has been developing constantly.As

128、 of now,it can be divided into three major technical paths:traditional satellite communication、3GPPNTNsatellitecommunicationand3GPPNTNsimilarsatellitecommunication.(1)Technical paths of traditional satellite communicationThe development and evolution of satellite communication technical standards is

129、a process to continuously improve transmission quality,increase transmission capacity,and expand the application scope.The traditional satellite communication technology22/120can be divided into narrow-band satellite mobile communication and broadbandsatellite mobile communication systems.Narrow-ban

130、d satellite mobile communication systems mainly use S,L and otherlow-frequency bands for communication to provide voice messages,SMS,andmedium-low speed data transmission services.Typical technical standards includeGMR-1,S-UMTS,etc.Narrow-band satellite mobile communication systems usuallyintegrate

131、satellite communication capabilities into smartphones.Featuring integrationof satellite coverage and terrestrial coverage,independent space networks,integrationof some satellite operators and terrestrial communication operators,integration ofsatellite terminals and terrestrial terminals,etc.,they ar

132、e suitable for scenarios such asdirect satellite connectivity to narrow-band phones and satellite IoT.Typical satellitesystems include Thuraya,Inmarsat,GlobalStar,etc.in foreign countries,andTiantong-1,BeiDou(short message communication),etc.in China.With the rapid increase in demand for broadband s

133、ervices and the continuousdevelopment of the technology,high-throughput satellite communication systemsbased on broadband data channels,forward single carriers,flexible configuration ofreturn carriers and other technologies have been maturing and widely deployed.Typical satellite systems include Sta

134、rlink,OneWeb,Jupiter,etc.in foreign countriesandChinaSat,APSTAR,etc.in China.TypicaltechnicalstandardsincludeDVB-S/S2/RCS,Surfbeam2,and so on.With global coverage,independent spacenetworks,independent satellite operators,and independent satellite terminals,thesehigh-throughput satellites are mainly

135、used for satellite broadband access.At present,as the global satellite communications industry is rapidly entering the satellite Internetstage,high-throughput mobile communication has become an important part of thesatellite Internet.(2)Evolution Route of 3GPP NTN technologyThe evolution route of 3G

136、PP NTN technology refers to the evolution plan forintegrated space-ground technology formulated by 3GPP and other terrestrial mobilecommunication organizations.Based on the 5G system and improved for satellitecommunication scenarios,this technical path expands network coverage to remote23/120and und

137、erserved areas where traditional ground-based infrastructure is scarce oreconomically unfeasible,thus eliminating the digital divide.The NTN standard iscompatible with terrestrial cellular systems and can offer integrated space-groundservice capabilities.It features integration and complementation o

138、f satellite coverageandterrestrialcoverage,integrationofsatelliteoperatorsandterrestrialcommunication operators,and integration of satellite terminals and terrestrialterminals.Contrarytothesilostandardpatternoftraditionalsatellitecommunicationtechnology,3GPP NTNtechnologyiscompletelyopenandtranspare

139、nt,which is conducive to the development of the ecosystem.This technicalevolution route has gradually become one of the most important developmentdirections of satellite communication technology.(3)Evolution route of 3GPP NTN similar technology3GPP NTN similar technology refers to a technical path t

140、hat adopts a technicalstandard similar to 3GPP NR-NTN(new radio-based NTN)technology and integratesthe characteristics of LEO satellite constellation communication for targeted technicaloptimization and improvement.3GPP NR-NTN similar technology is mainly used insatellite broadband application scena

141、rios.Based on LEO satellite constellations,it canwell provide low-latency,large-bandwidth broadband satellite services.By integratingcellular communication and terrestrial communication functions on the terminal side,3GPP NTN similar technology enables the integration and complementation ofsatellite

142、 coverage and terrestrial coverage.In addition,compared with 3GPP NTNtechnology,the similar technology has some private attributes,meeting the securityrequirements of national information infrastructure.This technical evolution route hasgradually become one of the most important development directio

143、ns of satellitecommunication technology.24/120Table 3-5 Technical Paths of Satellite CommunicationTechnicalPathCommunicationTypeTechnicalStandardTypicalSatelliteSystemsFeaturesApplicationScenariosLatestDevelopmentsTraditionalsatellitecommunicationBroadbandcommunicationDVB-S/S2/RCS orsimilarstandards

144、Starlink,OneWeb,Jupiter,ChinaSat 16,ChinaSat 19,APSTAR-6D,etc.,FlowerConstellations,Galaxy,O3bGlobalcoverage,independentspacenetworks,independentsatelliteoperators,andindependentsatelliteterminalsSatellitebroadbandaccessCost reductionand efficiencyimprovementPerformanceimprovementRepresentedby Space

145、XSurfbeam2ViasatNarrow-bandcommunicationGMR-1 orsimilarstandardsThuraya,TiantongsatellitesIntegrationandcomplementation ofsatellitecoverageandterrestrialcoverageDirectsatelliteconnectivityto phones,satellite IoTIntegratingsatellitecommunication capabilitiesintosmartphonesS-UMTSInmarsatsatellitesOthe

146、rprivatestandardsGlobalStar,Iridium Next,Orbcomm,GeespaceFutureMobilityConstellationsatellites,BeiDousatellites3GPP NTNtechnologyBroadbandcommunicationNR-NTN/Integrationandcomplementation ofsatellitecoverageandterrestrialcoverage;open andtransparenttechnicalstandards;Directsatelliteconnectivityto ph

147、ones,satellite IoTIndoor testingand validationand fieldtesting andvalidation onsatellites havebeensuccessivelyarranged andconducted.Narrow-bandcommunicationIoT-NTNTiantongsatellites,Inmarsatsatellites,Sateliot3GPP NTNsimilartechnologyBroadbandcommunicationSimilar toNR-NTN/Satellitebroadbandaccess,di

148、rectsatellite25/120TechnicalPathCommunicationTypeTechnicalStandardTypicalSatelliteSystemsFeaturesApplicationScenariosLatestDevelopmentsNTNsimilartechnologyhas someprivateattributes.connectivityto phones3.1.4 Operations of Satellite SystemsThe building of a satellite communication system involves a h

149、uge investment,soits operating model determines the lifespan of the entire system.At present,theoperating models of broadband communication satellite systems in the world fall intotwo types:closed and open commercial operations.Under closed commercialoperation,a company operates satellites,builds ga

150、teway stations,purchases terrestrialterminals,and then provides services to end users directly or through partners.According to different users,closed operation is divided into integrated operation anddistributor operation7.Under integrated operation,satellite operators are responsible for the compl

151、eteconstruction and operations of satellite systems,terrestrial networks and businesssystems,and provide satellite services directly to end users and charge relevant fees.As a B2C model,this model is suitable for countries and regions with a large numberof users of similar market nature(e.g.US and C

152、hina).Typical systems include Viasat,Starlink,and Tiantong-1.Under distributor operation,satellite operators build and operate satellite systems,terrestrial networks and business systems;Distributors participate in the building ofbusiness systems and provide local services to end users through their

153、 marketchannels and marketing networks.Typical distributors include ISP,telecom operators,VSAT,DTH operators,and other enterprises.As a B2B model,this model is suitablefor regions where markets are relatively dispersed,such as Europe andAfrica.Under open operation,satellite operators focus on the bu

154、ilding and operations ofsatellite systems and sell physical bandwidth to service providers,who buildterrestrial networks such as gateway stations,develop business systems,and provideservices to end users.Under this model,satellite operators and service providers share26/120business risks and interes

155、ts,but satellite operators are only responsible for satelliteoperations,while service providers are only responsible for providing local services.In this case,service providers can also provide business services more flexibly asneeded.To select the operating model,various factors,such as market disp

156、ersion,policies,and regulatory requirements,should be considered in a comprehensivemanner.Generally speaking,closed operation brings high throughput utilization andhigh returns with high risks;open operation generates a low return with small risksand a guaranteed income.In China,Tiantong-1,operated

157、by China Telecom,providesvoice messages,SMS,data transmission,fax,and other services.As an importantapplication platform for narrow-band satellite communication,it enhances theemergency communication capabilities of China.The ChinaSat satellites andAPSTAR satellites,operated by China Satcom,mainly p

158、rovide satellite radio andtelevision forwarding services for the radio and television industry,and providesatellite transponder lease services for government emergency,maritime,railway,andother organizations;BeiDou Satellite Communications provides BeiDou navigationand positioning,short message comm

159、unication and other services.3.2 Ground Communication StandardsFrom analog modulation to digital modulation,from voice service to data service,from narrowband to broadband,from simplex to full-duplex,mobile communicationtechnology experienced more than 40 years of explosive growth and has penetrated

160、into all areas of peoples lives,and become one of the important driving forces topromote social development.Figure 3-2 Schematic Diagram of Mobile Communication Development27/120In 1G,the Advanced Mobile Phone System(AMPS)of USA and the FullAccess Communication System(TACS)of UK are two main systems

161、 for analogmobile communication8,which use analog signals for transmission and processingand adopt FDMA access.Because different countries use different standards,differentfrequency bands and channel bandwidths,1G is a regional mobile communicationsystem.From 1G to 2G,modulation is changed from anal

162、og to digital,and the mainstandards of 2G include GSM and CDMA9.Services supported by 2G have alsoevolved from single voice services to voice,SMS,and data transmission(narrowband)services.From 2G to 3G,there is a unified standard-IMT-2000 radio interfacetechnology specification,including WCDMA,CDMA-

163、2000 and TD-SCDMA.TD-SCDMA is a standard proposed by China,which uses asynchronous TDD modeto effectively improve the utilization of frequency resources.3G can provide userswith a variety of broadband information services,such as images,music,webbrowsing,video conferencing,etc.3G is a true broadband

164、 multimedia global digitalmobile phone technology.4G follows the LTE technical specification,a global common standard developedby 3GPP,including TDD and FDD modes.4G is based on OFDM technology10,andthe downlink rate can reach 100Mbps and the uplink rate can reach 20Mbps.After thelarge-scale commerc

165、ial use of 4G,mobile broadband data services are still growingrapidly,and new applications and new communication technologies are constantlyupdated and iterated,bringing more diverse demands to the evolution of radionetworks,mainly including higher throughput,lower delay,higher reliability,lowerpowe

166、r consumption and support for more users.From the perspective of service andmarket development,mobile Internet and the Internet of Things are two importantdriving forces for the evolution of 5G communication.The evolution of 5G can besummarized into two branches,one is the mobile Internet broadband

167、service withlarge traffic,high speed and high mobility,the other is low-rate,wide-coverage,andhigh-capacity IoT services.ITU-R gives three scenarios of 5G,namely enhancedmobile broadband applied to the mobile Internet,massive machine communicationapplied to the Internet of Things,and ultra-reliable

168、low-delay communication11.28/120Meanwhile,ITU-R also gives the performance indicators of 5G system,which mainlyincludes the following performance indicators:(1)Traffic density:10 Tbit/(skm2)(2)Connection number density:106km2(3)Delay:1ms delay of the air interface(4)Mobility:500 km/h(5)Energy effici

169、ency:100 x improvement(compared to 4G)(6)User experience rate:0.11 Gbit/s(7)Spectrum efficiency:3x improvement(compared to 4G)(8)Peak rate:10 Gbit/s5G applications show a trend of vertical industry market and traditionalconsumer market going hand in hand.Countries around the world actively promote5G

170、 application landing,China,the United States,Europe,Japan and other leadingcountries and regions carry out 5G convergence application investments,explorationand demonstration in AR/VR,ultra-high-definition video,industrial Internet,smarttransportation,smart medical,public safety and emergency respon

171、se,military privatenetwork and other fields.In 2022,the global 5G market developed rapidly in terms ofnetwork population coverage,the number of base stations deployed,and the numberof 5G connections,and advanced countries in the world have initially completed theconstruction of the first batch of 5G

172、 commercial networks,with 5G networkscovering nearly one-third of the worlds population.The number of global 5Gconnections exceeded 1 billion,with a penetration rate of 12%,and the developmentspeed was much faster than that of 4G and 3G,and 5G has become the main mobilecommunication technology in th

173、e world.At present,3GPP has entered R19 stage.While vigorously developing 5.5G,countries have started the research of 6G.Europe,the United States,Japan and SouthKorea attach great importance to the development of 6G,through the formation ofresearch groups,the construction of public research faciliti

174、es,and the addition of 6Gresearch projects,increase capital investment in the field of 6G,and drive the researchof 6G advanced technologies in academia and industry,such as the U.S.Department29/120of Defense 6G Research and Development Center,the EU 6G flagship projectHexa-X-II,South Koreas 6G Resea

175、rch and Development Implementation Plan,Japans 6G research and development fund.At the same time,leading enterprises suchas Ericsson,Nokia,Samsung,and Deutsche Telekom further increase their investmentin 6G research and development and built joint testing and verification platforms.In China,the Cutt

176、ing-edge of 6G technology has reached a consensus at alllevels of government,6G has been written into the development plans of Beijing,Shanghai,Hebei,Guangdong and other provinces and cities.IMT-2030(6G)promotion group has promoted 6G research and innovation,and achieved batchresults.More than 20 en

177、terprises and universities have participated in the 6G keytechnology test of IMT-2030(6G)promotion group.The three major operators havesuccessively released the overall architecture of 6G network and key technologyresearch results,and the 6G research and development work of equipmentmanufacturers ha

178、s entered the stage of key technology concept prototype.4.Key Technologies for Integrated Space-Ground Networks Based on 5G NTN4.1 NetworkArchitectureBased on the integrated space-ground network architecture,communicationnodes in the future will no longer be limited to terrestrial nodes,but satellit

179、e nodeswill play an increasingly important role.With the evolution of 3GPP NTN technology,the payload and signal processing capability of satellites will be gradually improved,enabling transparent forwarding,base stations,core networks,and,by networkingwith terrestrial base stations,integrated space

180、-ground networks.In both R17 and R18 versions,3GPP NTN adopts a transparent forwardingarchitecture12,and satellites only enable radio frequency-related functions.So 3GPPNTN has low requirements on satellite capabilities,which is conducive to the rapidimplementation of NTN networking.As shown in Figu

181、re 4-1,the satellite serves asthe radio frequency processing unit between the terminal and NTN gateway to enabletransparent forwarding of radio signals.The baseband processing of signals is still30/120done in the terrestrial base station.Therefore,this network architecture has lowerrequirements on t

182、he payload and processing capability of satellites,facilitating rapiddeployment of networks.Figure 4-1 Transparent Forwarding Network Architecture3GPP has also studied the network architecture of regeneration mode,which isexpected to be implemented in future NTN evolution.In addition to the RF,some(

183、DU/CU)or all functions of the base station and some or all network elements of thecore networks(such as the user plane function)can be deployed on the satellite.In theregeneration mode,the service link uses the Uu interface,and the feeder linkimplements such interfaces as Xn,N1,N2,and N3,depending o

184、n the functions of thesatellite,as shown in Figure 4-2.Figure 4-2 Regeneration Mode Network ArchitectureWith the ability to decode and process packets on the satellite and supportinter-satellite links,satellite networks using regenerative transmission can offer betterperformance,greater flexibility,

185、and global coverage.Here are some potentialadvantages of deploying and implementing NG-RAN(+5GC)functions on satellites:(1)Reduced control/data plane latency;(2)Supporting low-latency services in areas without NTN gateways(notdeployed or temporarily not operated);(3)More flexible deployment of groun

186、d segment/NTN gateways;(4)Higher spectral efficiency of service links and feeder links.31/120In addition to access,satellites can also serve as backhaul links for base stationsto connect base stations and core networks.The 3GPP TS 23.501 standard formulatesthat satellites can be used as part of the

187、backhaul links between(R)AN and 5GC andsupport edge computing.If the access and mobility function(AMF)knows thatsatellite backhaul is used,it can report the satellite backhaul category and its changeto the session management function(SMF)in the Protocol Data Unit(PDU)sessionestablishment process.Whe

188、n the backhaul capability(such as latency and bandwidth)changes over time,the AMF needs to notify the SMF of the corresponding dynamicsatellite backhaul category;After receiving such information from the SMF,the policycontrol function(PCF)can apply for quality of service(QoS)monitoring of packetdela

189、y between the UE and the user plane function(UPF)to better support PDUsessions.4.2 Air Interface Transmission Technology4.2.1 Synchronization TechnologyNormal communication between terminals and base stations is based on strictuplink and downlink time-frequency synchronization between terminals and

190、basestations.In 5G NTN,due to a large distance and a high relative motion speed betweensatellites and terrestrial terminals,there is a transmission delay and Doppler shiftmuch higher than that of terrestrial systems,making it a challenge to reach uplink anddownlink time-frequency synchronization on

191、the terminal side.(1)Downlink synchronization technologyIn order to access the network,the UE must detect downlink synchronizationreference signals to complete time and frequency correction and cell ID detection.Inorder to address large frequency offset in NTN,the Doppler frequency shift on thefeede

192、r link can be compensated by the network side with the compensation valuetransparent to the terminal.The downlink Doppler frequency shift on the service linkcan also be pre-compensated by the network side with the pre-compensation valueoffered to the terminal.After the network compensates for the Do

193、ppler frequency shifton the service link,the most frequency offset is eliminated,and the residual frequency32/120offset is dependent on the cell size and elevation angle.In this case,for high-speedmoving LEO satellites,robust downlink synchronization performance can be achievedwith the existing sync

194、hronization reference signal designs.If the network side doesnot compensate for the downlink frequency offset on the service link,the UE needs toestimate the Doppler shift on all service links based on downlink synchronizationsignals,and the terminal receiver requires additional complexity for relia

195、ble initialdownlink synchronization performance12.(2)Uplink synchronization compensation technologyAs for uplink frequency synchronization,generally speaking,the terminal can,based on the terminal location and satellite ephemeris information,estimate andcalculate the Doppler frequency shift generate

196、d on the service link.Therefore,theterminal can calculate and pre-compensate by itself the Doppler frequency offsetvalue on the service link.The Doppler frequency offset value on the feeder link canbe post-compensated by the network side or the terrestrial gateway,with thecompensation value transpar

197、ent to the user.In addition,there may also be frequencyerrors when the satellite transmits data.The value of this error is also transparent tousers and the error can be compensated by the network side or directly by the satellite.As for uplink timing synchronization,the UE can calculate the round-tr

198、ippropagation delay between the UE and the satellite in real time based on its ownlocation and satellite ephemeris information,and perform timing advance on theservice link based on the round-trip delay time calculated(timing advance at the UElevel).As for the propagation delay on the feeder link,si

199、nce the terminal does notknow the location of the base station,the terminal is unable to calculate the round-trippropagation delay between the satellite and the base station in real time and performtiming advance on the feeder link.Therefore,to address the uplink timingsynchronization problem on the

200、 feeder link,one way is that the uplink timing advanceon the feeder link is completely handled by the network without the involvement ofthe UE.Another way is that the network indicates parameters about the timingadvance(known as public timing advance)on the feeder link,and then the UE can33/120deter

201、mine part or all of the timing advance on the feeder link in real time based on thepublic timing advance parameters provided by the network13.4.2.2 Timing ManagementIn terrestrial mobile communication systems,the signal propagation delay isusually less than 1 ms.On the contrary,compared with terrest

202、rial mobilecommunication systems,the signal propagation delay in satellite communicationsystems is very large.The propagation delay value is generally between tens tohundreds of milliseconds,depending on the satellite altitude and satellite payload type.Faced with such a large air interface delay,th

203、e terminal needs to apply a large timingadvance(ranging from tens to hundreds of milliseconds)to ensure uplinksynchronization when performing uplink transmission.As a result,there will be alarge offset in the uplink-downlink frame timing on the terminal side.The uplinktiming synchronization on the t

204、erminal faces the following two cases:Case 1:The terminal applies a complete timing advance(TA)when sendinguplink data,meaning that the public TA parameter indicated by the network is thetiming advance on the entire feeder link.In this case,the uplink and downlink frametimings on the base station si

205、de are aligned,while the uplink and downlink timings onthe terminal side are different with a gap of all timing advance,as shown in Figure4-3.Figure 4-3 The uplink and downlink frame timings on the base station side arealigned,while there is a large offset in the uplink and downlink frame timings on

206、 theterminal side.Case 2:The terminal applies part of the timing advance when sending uplinkdata,meaning that the public TA parameters indicated by the network are part of thetiming advance on the feeder link,and the remaining propagation delay needs to behandled by the base station.In this case,the

207、 uplink and downlink frame timings on34/120the base station side are not aligned,and the uplink and downlink timings on theterminal side are also different with a gap of a timing advance,as shown in Figure4-4.Figure 4-4 The uplink and downlink frame timings on the base station side are notaligned,wh

208、ile there is a small offset in the uplink and downlink frame timings on theUE side.In Case 1,since the UE compensates for the delay of the entire transmission link,the uplink and downlink frames on the base station side are aligned,while on the basestation side,the complexity will not increase witho

209、ut any other transmission timingproblems.In Case 2,since the terminal compensates only part of TA,the base stationside needs to handle part of the TA.Therefore,the uplink and downlink frames on thebase station side are not aligned with the increased complexity on the base stationside.Since the uplin

210、k and downlink timings on the terminal side are not aligned with alarge offset,timing needs to be enhanced if involving uplink and downlink timinginteraction.4.2.3 CoverageIn NTN communication systems,the satellite altitude can be hundreds to tens ofthousands of kilometers,so there is a large path l

211、oss between terminals and satellites.For example,in the GEO satellite scenario,the free-space route loss in the S band canreach 190.6 dB.In addition,there is shadow fading,polarization loss,atmosphericloss,and other losses in transmission between terminals and satellites.In order toensure uplink and

212、 downlink coverage,it can be achieved in general by increasing thepower of the transmitter,the sensitivity of the receiver,and the antenna gain on bothsides of the transmitter and receiver,and using directional antennas,narrow-bandtransmission,low-frequency transmission,etc.,as shown in Figure 4-5.3

213、5/120Figure 4-5 Route Loss in the NTN ScenarioIn the initial stage of 5G NTN,the terminal features are defined as follows12:(1)The transmit power of VSAT is 33 dBm,the antenna gain is 43.2 dBm,anddirectional antennas are used;(2)The transmit power of handheld terminals is 23 dBm,the antenna gain is

214、0dBm,and omnidirectional antennas are used;(3)The transmission power of IoT devices is 23/20 dBm,the antenna gain is 0dBm,and omnidirectional antennas are used.As can be seen from the above terminal features,in the initial stage of 5G NTN,there are special requirements for terminals on antenna gain

215、and transmit power.On the other hand,5G NTN has also higher requirements on satellite capabilities.Take the satellite parameter Set1 defined by 3GPP.For S-band GEO satellites,theuplink G/T value is 19 dB K-1,and the downlink EIRP is 59 dBW/MHz;For Ka-bandGEO satellites,the uplink G/T value is 28 dB

216、K-1,and the downlink EIRP is 40dBW/MHz.Based on the characteristics of 5G NTN terminals and satellites,low-frequency(e.g.,S band)and narrow-band transmission are required for uplink data transmissionfrom handheld and IoT terminals to meet link budget requirements.However,VSATscan utilize high-freque

217、ncy and broadband transmission for uplink to meet therequirements.Considering that typical smartphone antenna gains are as low as-5.5dBm,or even lower,which significantly deviates from the defined antenna gain forhandheld terminals in 5G NTN(0 dBm),research on coverage enhancement in the 5GNTN scena

218、rio is conducted in 3GPP R18 to enable smartphones to access 5G NTNfor VoIP and low-rate data transmission14.Furthermore,due to power limitations onthe satellite and the large number of beams within a single satellite coverage area(for36/120LEO satellites,the number of beams per satellite can exceed

219、 1,000),research on thedownlink coverage enhancement technology will continue in R19.4.2.4 System Throughput Enhancement TechnologyAir interface propagation with high delay affects both data transmission andsystem throughput.In the existing HARQ protocol,the sending terminal needs to waitfor feedbac

220、k from the receiving terminal before sending new data.In the case ofNACK,the sending terminal may need to resend data packets,introducing delays inthe communication protocol.In terrestrial networks,where round-trip latency istypically within 1 ms,the impact of the stop-and-wait mechanism introduced

221、byexisting HARQ transmission is relatively small.In the 5G NTN system,transmissionlatency is extremely high.According to the existing HARQ transmission protocolmechanism,after the network schedules downlink data using a certain HARQ process,it needs to receive HARQ-ACK feedback from the terminal bef

222、ore it can continue touse that HARQ process for new data scheduling or data retransmission.The timeelapsed from the base station sending downlink data to receiving feedback from theterminal may be several hundred milliseconds,as shown in Figure 4-6.Figure 4-6Schematic Diagram of HARQ FeedbackTherefo

223、re,the existing HARQ-ACK transmission mechanism severely limits thesystem throughput of 5G NTN.The following section provides three methods toimprove the data transmission rate of 5G NTN:37/120Method 1:Increase the number of supported HARQ processes in 5G NTN toensure sufficient scheduling of data o

224、n the network during propagation delay,therebyenhancing system throughput.Method 2:Deactivate the HARQ-ACK feedback for HARQ processes to avoidneeding a stop-and-wait mechanism on the network.Method 3:Use blind retransmission to enhance data transmission reliability,mitigating HARQ transmission late

225、ncy and boosting system throughput.In addition,existing data scheduling methods include dynamic scheduling andSemi-Persistent Scheduling(SPS).For dynamic scheduling,the terminal first receivesDownlink Control Information(DCI)issued by the network,and then receives andsends data according to the sche

226、duling instructions.For SPS,the networkpre-configures uplink and downlink data transmission resources through higher-layersignaling,and the terminal directly receives and sends data on these resources.Inscenarios with high delay,SPS transmission is more advantageous.4.2.5 Beam ManagementExistingterr

227、estrial5Gcommunicationsystemshaveestablishedbeammanagement mechanisms,including beam measurement reporting,beam selection,beam indication,and beam recovery processes.In satellite communication,satellitestypically provide coverage to the ground through multiple beams,sharing satellitebandwidth and po

228、wer resources among these beams.Compared to 5G NR,beammanagement in the satellite communication system has the following characteristics:(1)Satellites move rapidly,resulting in more frequent beam switches;(2)In scenarios with high Doppler shifts,accuracy issues arise when utilizingSSB or CSI-RS for

229、beam measurements;(3)Signal quality differences between different locations within the same cell areminimal,meaningthenear-fareffectislesspronouncedinthesatellitecommunication system;(4)In terrestrial fixed-beam scenarios,changes in beam coverage areas can leadto multiple UEs within the beam coverag

230、e area switching beams at the same time;38/120(5)Satellite movement follows predictable patterns,including beam switchtiming and sequence;(6)Significant propagation delay between base stations and UEs can lead totiming issues in beam measurement reporting and beam indication.Given these characterist

231、ics,the NTN system requires more efficient beamswitching mechanisms to mitigate issues such as frequent and unnecessary switches.The following section provides two types of beam management mechanisms12.(1)UE-driven beam switchingFor one approach,the network configures the timing and sequence of beam

232、switching for terminals based on satellite information,beam distribution patterns,andsatellite ephemeris data.To implement it,the network configures the sequence ofbeam switching and the service duration for each beam.When the service duration ofthe current beam expires,the terminal switches to the

233、next beam according to thepredetermined sequence,as shown in Figure 4-7.Alternatively,UEs autonomouslyswitch beams based on location information and beam distribution patterns,withlocation information uploaded to the network.Figure 4-7 Schematic Diagram of Satellite Trajectory(2)Network-controlled b

234、eam switchingIn the existing terrestrial 5G beam management,terminals report beammeasurement results,and the network controls terminal beam switching based onreported measurements.Considering minimal signal quality differences across celllocations in the satellite communication system,terminals can

235、report their location39/120information for network-controlled beamswitching.In terrestrial fixed-beamscenarios,where multiple UEs switch beams simultaneously within a beam coveragearea,UE group-level15beam switching mechanisms can reduce signaling overhead.In practical applications,there may be scen

236、arios where the communicationdemands on certain beams significantly exceed the available capacity,while in otherbeams,the demands fall below capacity.This mismatch results in unmet demand inhotspot areas and underutilized capacity in less active areas,posing challenges forsatellite operators and ser

237、vice providers16.Hence,the ability to flexibly allocatebeam resources within satellite coverage areas is becoming a necessity for futurebroadband multi-beam satellites.4.2.6 MobilityIn satellite communication networks,mobility management faces new challenges.For instance,in NTN cells,signal strength

238、 variations between the cell center and edgeare minimal,rendering existing mobility management based on wireless signal qualityinadequate.To address this,5G NTN proposes new mobility management policiesbased on terminal location and satellite coverage duration.(1)Conditional hand over(CHO)Based on t

239、erminal location,introduce location-based CHOs by setting thresholdsfor satellite reference points and terminal-to-reference point distances.Location-basedCHOs are triggered when the conditions are met.12.Based on satellite coverageduration,introduce time-based CHOs by providing information on when

240、the currentcell stops service and the candidate cell starts service.Cells broadcast the time whenthey stop covering an area through system information,which can help the UEreselect cells and determine an appropriate time for measuring neighbor cells.Time-based CHOs are triggered when the conditions

241、are met.(2)Cell selection and reselectionAssisted cell selection and reselection based on ephemeris information:Terminals predict when satellites will cover specific areas based on ephemerisinformation,allowing dynamic andaccurate searchfor available NTN cellinformation17,thus improving selection or

242、 reselection success rates.40/120(3)Tracking area managementRapid satellite movement necessitates frequent tracking area updates.Whilesatellites cover large cell areas,tracking areas expand,reducing update frequency butincreasing paging load.Therefore,striking a balance is crucial.In 3GPP R16,fixedT

243、racking Area Codes(TAC)are introduced on the ground while cells adjust tosatellite movements.In LEO scenarios,when the cell is scanning on the ground,thebroadcasted TAC will be changed as the cell reaches the next fixed tracking arealocation on Earth.This type of hard tracking area update reduces up

244、date frequency butposes challenges for system information updates and paging cycles.Therefore,R17proposes the soft tracking area update,where networks broadcast multiple TACs foreach Public Land Mobile Network(PLMN)in NR-NTN cells,allowing up to 12TACs to be broadcasted,controlled by the network.Add

245、itionally,if the currentlybroadcasted TAC matches the region where the UE is registered,the UE will notinitiate a mobility-triggered registration process18.4.3 Security TechnologyThe integrated space-ground communication system based on 5G NTN includesboth transparency and regeneration modes,implyin

246、g that some access network andcore network functions are located on satellites.This creates security scenariosdistinct from those in terrestrial networks.The inter-satellite links and the feeder links between satellites and gateways inthe integrated space-ground network are the wireless links,which

247、may be susceptibleto interference and eavesdropping,necessitating protection.On-board networkelements may be deployed on the same satellite or different satellites.When ondifferent satellites,security between network elements,such as trust relationships andcommunication security,can be ensured using

248、 distributed or centralized securitymechanisms.Due to the mobility of certain types of satellites,the networkingrelationships between on-board and terrestrial network elements may dynamicallychange,requiring enhanced security mechanisms.41/120In specific scenarios like store-and-forward,where end-to

249、-end links may bediscontinuous(e.g.,service or feeder links),ensuring authentication between satellitesand UEs without satellite connection to the terrestrial core network and establishingsecure connections between UEs and satellites is crucial.To address this,certainsecurity functions of the core n

250、etwork,such as authentication and key management,can be embedded in satellites.UE security context information can also be sharedamong satellites or between satellite and terrestrial networks.4.4 Satellite Implementation Technology(1)Components of communication satellitesCommunication satellites are

251、 composed of a satellite platform and payloads.Thesatellite platform,by carrying various payloads,enables the satellite to performdifferent functions.The satellite platform includes systems such as power supply,structure,propulsion,thermal control,attitude control,and data management(satellite-borne

252、computing platform),ensuring service support for the satellite payload.Figure 4-8 Components of the Satellite PlatformThe satellite payloads,also known as the specialized systems,are instruments,equipment,or systems directly related to the satellites mission.They typically includeantenna systems,tra

253、nsponder systems,and other metal or non-metal materials and42/120electronic components.Traditional communication payloads mainly consist of phasedarray antennas and transponders,while satellite internet payloads add inter-satellitelinks on top of traditional communication payloads.Figure 4-9 Communi

254、cation Payload Components(2)Satellite-borne Multi-beam Antenna TechnologySatellite-borne antennas are critical payloads of communication satellites.Theyinclude simple antennas(standard circular or elliptical beams),formed wirelessantennas(multiple-feed source beamforming and reflector forming),and m

255、ulti-beamantennas.Satellite-borne multi-beam antennas are favored due to their ability to meetthedemandsofhighgain,widecoverage,highdatarates,andterminalminiaturization,making them a current focus of research and application.Satellite-borne multi-beam antennas can be categorized into reflector-based

256、,lens-based,and phased array-based antennas.A comparison of various types ofmulti-beam antennas is shown in Table 4-1.Table 4-1Comparison of Three Types of Multi-beam AntennasAntennaTypeAdvantagesDisadvantagesReflectorMulti-beamAntennaLight weight,simple structure,mature design technology,excellent

257、performance,etc.Inferior wide-angle scanningperformance compared tophased array multi-beamantennas and requires biasedstructure to avoid blocking offeed array.LensMulti-beamAntennaGreater design flexibilitycompared to reflector multi-beamantennas,good rotationalsymmetry,excellent opticalcharacterist

258、ics,and no apertureblocking.High attenuation and signal lossin low-frequency bands,severely restrict theirapplicability in on-boardcommunications.43/120Phased ArrayMulti-beamAntennaWide scanning angles,lowprofile,low signal loss,lightweight,flexible multi-beam/beamforming,beam steering,and fluxcover

259、age.Feed network losses,narrowbandwidth,complex structure,and high cost.Currently,typical large-scale satellite-borne antenna arrays mainly consist ofreflector-based multi-beam antennas and phased array multi-beam antennas.Reflectorantennas offer advantages such as lightweight,simple structure,and m

260、ature designtechnology.With large aperture antennas,they can generate multiple high-gain,lowsidelobe spot beams.GEO satellites,located at high orbits with long transmissionroutes and high route losses,typically employ reflector multi-beam antennas,oftenwith apertures exceeding 10 meters.For example,

261、the American TeereStar-1 satelliteadopts an ultra-large S-band metal mesh reflector multi-beam antenna with a diameterof up to 18 meters,while the antenna aperture of the American SkyTerra-1/-2 reaches22 meters.Phased array multi-beam antennas feature wide scanning angles,low profile,lowsignal loss,

262、and light weight,enabling flexible multi-beam/beam forming,beamsteering,and flux coverage.LEO satellites,characterized by low orbits and wide fieldof view,generally opt for phased array configurations to meet the need for widescanning angles.(3)Satellite-borne power amplifier technologySatellite-bor

263、ne power amplifier is a crucial component of satellite-bornetransponders.The efficiency of power conversion directly affects on-board thermalmanagement and payload capacity,ultimately impacting satellite weight and volume,making it critical on-board equipment.The satellite-borne power amplifier cons

264、ists ofa Traveling-wave tube amplifier(TWTA)and Solid State PowerAmplifier(SSPA).Previously,the on-board power amplifier utilized the TWTA,which comprises atraveling-wave tube,protective circuits like the klystron,and a regulated powersupply.The TWTA operates within a frequency range of 300 MHz to 5

265、0 GHz,offering a power gain of approximately 40 dB to 70 dB.Particularly in high-powerand high-frequency scenarios,the TWTA can deliver significantly higher outputpower compared to the SSPA,ranging from a few watts to several megawatts(e.g.,rated output power of up to 2.25 kW in the 6 GHz band).The

266、TWTA is more44/120cost-effective in applications requiring high power over 200 W,primarily used inhigh-earth orbit and high-throughput satellite systems.The SSPA employs field-effect transistors(FETs)as the primary RF poweramplifier,operating at low voltages and being relatively easier to implement.

267、TheSSPA typically requires integrated power supplies.Due to its lower individual outputpower,the SSPA employs multiple power transistors connected in parallel to amplifypower.The SSPAmainly operates in L,S,and C frequency bands with low power andlow frequency,offering output powers below 200 W.Curre

268、ntly,the SSPA is widelyused in LEO communication satellite systems.(4)Inter-satellite link technologyThe inter-satellite link refers to the communication links between satellites,allowing multiple satellites to interconnect and exchange to exchange information.This setup forms a space communication

269、network with satellites as exchange nodes.Introducing inter-satellite links in LEO satellite mobile communication systemsreduces reliance on terrestrial networks.It enables flexible route selection andnetwork management,reduces the need for terrestrial gateway stations,and simplifiesdeployment while

270、 lowering costs.The core component of inter-satellite links is the communication terminal,whichrequires a small beam divergence angle,excellent resistance to interference,andinterceptionperformance,ensuringhighsystemsecurity.Currently,thekeytechnologies include terahertz and laser inter-satellite li

271、nks.Terahertz inter-satellitelinks offer up to 10 Gbps transmission rate with better confidentiality,while laserinter-satellite links are convenient as it doesnt require specific frequency bandallocation from the International Telecommunication Union(ITU).(5)On-board fault-tolerant redundancy techno

272、logyIn the space environment,radiation particles can affect digital signal processors(e.g.,FPGAs or DSPs)on satellite-borne platforms.This can alter the logicalconfiguration or storage of processing modules,resulting in temporary(soft errors)orpersistent processing faults.Commonly used satellite pay

273、load fault-tolerant protectionmeasures include hardware reinforcement,system-level protection,and circuit-levelfault tolerance.Hardware reinforcement involves using aerospace-grade devices with specialpackaging processes to improve system reliability.However,aerospace-grade devices45/120may not meet

274、 the demands of modern space applications.NASA has proposed usinglow-grade commercial or industrial-grade devices(collectively referred to as COTSdevices)to partially or completely replace aerospace-grade devices.While COTSdevices offer excellent performance,low cost,and readily available supply,the

275、y comewith higher failure risks and require fault-tolerant reinforcement based on redundantresources.System-level protection includes multi-machine backups,periodic fault detection,and reconfiguration to recover from failures.However,this approach is costly and haspoor real-time performance,making i

276、t unable to ensure continuous system operation.Circuit-level fault tolerance introduces redundancy(such as logic or timeredundancy)to ensure correct output from processing modules despite failures inlogical or storage units.The most common approach is Triple Modular Redundancy(TMR),which doubles cal

277、culation,storage,and power consumption overhead,posinga significant burden on space platforms and embedded systems with strict limitationson volume,weight,and power.4.5 Terminal Implementation TechnologyIntegratedspace-groundsatelliteinternetisaheterogeneousnetwork,characterized by highly dynamic sp

278、atial nodes and immense spatiotemporal scales.This demands higher requirements for terminal access capability,antenna gain,lowsignal-to-noise ratio(SNR)reception capability,size,and power consumption.(1)Miniaturization of antenna technologyTraditionalsatellitephonesrequirebulkyexternalantennasforsig

279、naltransmission and reception,limiting portability and aesthetics.For handheld terminalsin consumer applications,lightweight,compact,and aesthetically pleasing designs areessential.To enable satellite connectivity on smartphones,research is needed tointegrate satellite communication functionality in

280、to these devices,focusing onminiaturization and low power consumption.This requires significant advancementsin terminal antenna RF technology and baseband chip technology.Regarding antennas,research is ongoing to miniaturize terminal antennas,including micro-antenna and integrated antenna technologi

281、es.Furthermore,efforts arebeing made to overcome design constraints to develop high-gain antennas for satellitecommunication on smartphones.Continuous optimization of smartphone MIMO46/120antenna arrays is also necessary to improve antenna gain.To address low powerconsumption,research is underway to

282、 develop integrated baseband chips forintegrated space-ground communication,supporting standards like 5G NTN.Thisaims to reduce terminal size and minimize energy consumption from chip interactions.Additionally,efforts are focused on enhancing power amplifier efficiency to lowerpower consumption.(2)P

283、hased array antenna technology for LEO constellationsFor LEO satellite constellations,due to the rapid movement of satellites,maintaining stable and reliable links requires automated alignment and tracking ofsatellites and terrestrial terminals to account for constantly changing relative positions.T

284、raditional mechanically scanned terminal antennas face challenges meeting real-timerequirements.Phased array technology,with electronic scanning,offers fast responsetimes and flexible beamforming capabilities,making it increasingly popular formeeting various radiation pattern design needs.Phased arr

285、ay antennas are essential forintegrated space-ground terminals.By controlling signal phases,they can quicklytrack LEO satellites,allowing a single antenna to support multiple satellitessimultaneously.Currently,phased array mmWave RF chips are primarily based on GaAs andGaN technologies,offering good

286、 transmission performance and low receive noisefigures.However,due to each phased array antenna containing hundreds or thousandsof phased array chips,they account for over 60%of antenna costs.This makessilicon-based chips,which offer lower costs and higher integration levels,morepromising for civili

287、an markets.Silicon-based RF chips utilize CMOS,CMOS-SOI,and SiGe technologies.Considering the large antenna apertures in satellite communication applications andthe large-scale channels involved when using phased array technology,CMOS-basedRF chip technology is often preferred.Silicon-based CMOS chi

288、p technology benefitsfrom mature processes such as 65 nm,45 nm,and 28 nm,with high productioncapacity and yield rates.Utilizing advanced digital circuitry,multiple channels forreception,transmission,phase shifting,and attenuation control can be consolidatedinto a single chip.Moreover,digital control

289、 functions like serial-to-parallelconversion,temperature regulation,power detection,and self-testing can be integratedthrough RF SoC packaging,enabling highly integrated phased array antennas.Due tothe advantages of large-scale commercial low-cost production,silicon-based CMOS47/120chip technology i

290、s currently one of the mainstream technologies in the internationalsatellite terminal phased array antenna field.Looking towards future large-scale production,CMOS-based low-cost phasedarray antenna technology still needs to address challenges such as low chip efficiency,low power,and high noise fig

291、ures.Since the electron mobility of the silicon materialis low,achieving high chip efficiency with CMOS technologies is challenging.Currently,single-chip efficiency in the mmWave frequency band reaches 20%,significantly lower than the 40%efficiency of GaAs chips.Achieving high power ischallenging,wi

292、th single-chip power levels at only 50 mW compared to the 5W outputpower of GaAs chips.Additionally,achieving low noise figures remains difficult,withcurrent levels at 3 dB compared to the 1.5 dB of GaAs chips.(3)RF frontend integration technologyThe integrated space-ground terminals must cater to b

293、oth terrestrial cellular andsatellite communications.With various access networks utilizing different frequencybands,the same network also grapples with challenges like fragmented bandallocation due to historical spectrum management practices.Therefore,terminals needto support multiple communication

294、 standards and RF frequency bands to accessdifferent networks,which mainly relies on the baseband chip,RF chip,and RFfrontend.Compared to digital baseband chips and RF chips,supporting multiplemodes and frequency bands poses greater challenges for the RF frontend.The RFfrontend determines important

295、performance metrics such as communication modessupported,received signal strength,call stability,and transmit power,directlyimpacting user experience.The RF frontend consists of a series of analog devices,including switches,poweramplifiers,low-noise amplifiers,filters,and duplexers.Each communicatio

296、n standardand frequency band requires dedicated filters or duplexers,making it challenging toshare them.On one hand,as the supported frequency bands grow,so does the numberof devices.On the other hand,terminals,especially handheld ones,have stringent sizeconstraints.This limits the expansion of the

297、PCB area dedicated to the RF frontenddue to structural design requirements.Moreover,as RF communication standardsbecome more complex,the effectiveness of discrete solutions for debugging48/120diminishes rapidly.Under the constraints of space and time,modularizing RFfrontend devices has become a majo

298、r trend,reducing volume,enhancing performance,improving debugging efficiency,and cutting costs.The RF frontend module integrates several high-performance devices of differenttechnologies in a System In a Package(SiP)format,including RF switches,low-noiseamplifiers,filters,duplexers,power amplifiers,

299、and other discrete devices.One of thechallenges faced by RF frontend modules mainly comes from high-performancefilters.Sub-6 GHz is the prime frequency band for mobile communication,housingLTE,5G,GPS,2.4 GHz Wi-Fi,Bluetooth,and other network bands.With the rise ofsatellite communication,the RF front

300、end of terminals must accommodate numerousfrequency bands,demanding dozens or hundreds of filters,thus complicating RFfrontend design.High frequencies and wide bandwidths result in rapid semiconductortransistor characteristic degradation,challenging high performance achievement.Expanding bandwidth c

301、omplicates achieving passband filter flatness.Optimalfilters now demand Surface Acoustic Wave(SAW),Bulk Acoustic Wave(BAW),orMicro-electro-mechanical System(MEMS)technologies.As frequency rises,poweramplifier efficiency declines.GaAs or GaN technologies are essential for achievingoptimal efficiency

302、in power amplifiers.However,these device technologies areincompatible,posing challenges for heterogeneous integration of the RF frontend.Transferring chips from different technologies onto a common chip substrate facesissues like material mismatch,electrical interconnection,and thermal management.Co

303、ntinuous innovation is required in the terminal RF front-end to meet the needsof the integrated space-ground network.As CMOS RFIC integration advances,various SiP technologies become prominent.Chiplet technology introduces new ideasto the design of RF circuits and systems.With the growing complexity

304、 of futuresystems and the need for extensive collaboration,Chiplet technology can harnessdiverse materials or devices,enhancing the flexibility of RF communication systems.Moreover,the digital attributes of RF circuits are increasingly evident,enablingdigital RF design to address the limitations of

305、RF CMOS technology.49/1204.6 Testing TechnologyIn NTN scenarios,the height and speed of airborne or satellite-borne carriers,aswell as the resulting high propagation delay and Doppler shift,will bring thefollowing new challenges to NTN design and application.(1)High transmission latencyThe extended

306、distance between terrestrial stations or UEs and satellites leads tohigher transmission latency than in terrestrial cellular networks.In transparency mode,single-path transmission latency can reach several hundred milliseconds.(2)High Doppler shiftFor LEO satellite systems,the high-speed orbit intro

307、duces technical challengessuch as Doppler shift and timing variation.Doppler shifts in the range of tens ofkilohertz to megahertz must be addressed.(3)Low SNRSatellite communications face significant propagation losses due to longdistances and high frequencies,leading to low SNR issues exacerbated b

308、y payloaddevice limitations.(4)Complex mobility managementIn TN scenarios,cells are fixed,and only terminal mobility issues exist.However,in NTN scenarios,both cells and terminals are mobile,requiring a reevaluation ofmobility management processes such as cell reselection,handover,beam selection,and

309、 recovery.In typical NTN scenarios,the NTN communication testing technology systemmainly includes MIMO communication testing technology,microwave and mmWavecommunication testing technology,communication signaling simulation and modelingtechnology,network performance testing technology,and system-lev

310、el testing andvalidation technology.50/120Figure 4-10 NTN Communication Testing Technology System1)MIMO communication testing technologyMIMO is a key technology in NTN,aimed at increasing spectrum efficiency.This involves developing and testing MIMO mmWave NTN communication signalenvironments for co

311、re NTN components and NTN gateway stations,including MIMOsignal simulation,analysis,over-the-air(OTA)testing,comprehensive gatewaystation testing,and channel simulation.2)Microwave and mmWave communication testing technologyCarrier frequencies between airborne or satellite-borne platforms and UE spa

312、nthe entire range of 0.5 GHz to 100 GHz.mmWave channels possess unique propertiesdistinct from traditional channels,requiring measurement and validation of theirfeatures to enable real-time communication in mmWave systems.3)Communication signaling simulation testing technologyNTN communication simul

313、ator is crucial for new technology and productdevelopment.It employs instruments with terminal simulation capabilities to realizeterminal and gateway station solutions for the NTN air interface,validating key NTNtechnologies and system designs.The solutions involve NTN terminal simulation,NTN gatewa

314、y station simulation,and NTN communication terminal protocolsimulation testing based on Tree and Tabular Combined Notation(TTCN).4)Network performance testing technology51/120NTN networks employ a heterogeneous network architecture,where access layerdetermination and service cell selection are based

315、 on user requirements.For testing,simulating continuous coverage across frequency bands with multi-layer spectrumoverlay is crucial.Node simulation should provide real-time access to correspondinglayer cells,even amidst multi-layer interference.Complex transmission control andscheduling design are n

316、eeded based on business types.Network performance testingtechnology includes NTN air interface monitoring,analysis,and consistency protocolanalysis for heterogeneous networks.5)System-level testing and validation technologyNTN communication systems must meet the evolving needs of traffic growth,dela

317、yreduction,anddeviceconnectivity,supportingheterogeneousnetworkintegration and various business scenarios.The consistency testing system isnecessary for validating and developing NTN terminals or gateway stations.System-level testing and validation include RF consistency testing,wireless resourceman

318、agement consistency testing,protocol consistency testing,large-scale antennaarray testing and validation,and mmWave communication testing and validation.5.Development and Practice of Integrated Space-Ground Industry based on 5GNTN5.1 5G Integrated Space-Ground Industry ChainThe integrated space-grou

319、nd industry chain is extensive,including satellitemanufacturing,satellitelaunching,networkequipment,terminaldevicesandapplications,testing instruments,and integrated space-ground network operations.The integrated space-ground system,a novel B5G or 6G network architecture,drivesindustry-wide explorat

320、ion and innovation,experiencing robust industrial growth.52/120Figure 5-1 Schematic Diagram of the Integrated Space-Ground Industry Chain5.1.1 Satellite PlatformThe satellite platform consists of the satellite and its service support system,capable of hosting one or multiple payloads.With different

321、payloads,the platform canaccommodate various satellite configurations for different functions.(1)Major foreign satellite platformsMajor communication satellite platforms abroad include Boeing BSS-702,Lockheed Martin A2100,SSL 1300,Airbus Eurostar-E3000,Starlink,and Viasat.The Boeing BSS-702 series,d

322、eveloped by American Hughes Aircraft Company,ranges from 1,500 kg to 6,100 kg in mass,with an output power of 3 kW to 18 kW.Itcan accommodate approximately 100 high-power transponders,serving payloads forMEO and GEO orbits weighing between 500 kg and 1200 kg.The platform comprisesvarious sub-models

323、tailored for different purposes:BSS-702HP(13 kW to 18 kW)forhigh-power satellites,BSS-702MP(6 kW to 12 kW)for medium-power satellites,BSS-702GEM(12 kW to 18 kW)for mobile phone services,and BSS-702SP andBSS-702X for small satellites.The Eurostar-E3000 series satellite platform,developed by Airbus,in

324、cludesvariants like Eurostar-E3000/E3000S/E3000GM/E3000EOR/Neo.With a launch massof 6.4 T,it employs chemical or chemical and plasma electric propulsion.Its payloadof 15 kW supports up to 120 high-power transponders,making it Europes top choicefor communication satellite applications.The SSL 1300 se

325、ries satellite platform,developed by American SpaceSystems/Loral,measures 230 cm 200 cm 300 cm and supports S-bandcommunication.With a launch mass exceeding 6,500 kg,it utilizes xenon ion hallthrusters for in-orbit position maintenance and attitude control via electric propulsion.This platform cater

326、s to LEO,geostationary earth orbit,and various high-earth orbit53/120payloads,commanding more than 25%of the satellite platform market share.It usedto be one of the satellite platforms China has long procured.The Starlink satellite platform,launched by the American aerospace companySpaceX in 2015,is

327、 primarily focused on mega-constellations.It slashes costs insatellite manufacturing through flat-panel design,the use of krypton ion thrusters,andsingle-sided solar panels.It also reduces satellite launch costs via satellite massproduction,reusable rockets,and multiple-satellite launch technologies

328、.The Starlinksatellite platform rapidly evolves technologically and in capability.It has developedfive models including two experimental satellites known as Tintin A and Tintin B,V0.9,V1.0,V1.5,and V2.0.V0.9,V1.0,and V1.5 are classified as first-generationsatellites,measuring 3.2 meters in length.Th

329、ey feature a flat-panel design,fourhigh-throughput phased array antennas,and single-wing solar panels equipped withbuilt-in hall thrusters.V0.9 weighs 227 kg and supports Ku-band communication,V1.0 weighs 260 kg and adds support for Ka-band,while V1.5 weighs 295 kg andadds support for laser inter-sa

330、tellite links.V2.0,referred to as the second-generationsatellite,measures 7 meters in length,weighs 1.25 T,and offers approximately 10times the performance improvement.(2)Major satellite platforms in ChinaChina primarily relies on the Dongfanghong series of satellite platforms.Existing satellite pla

331、tforms include DFH-3,DFH-3B,DFH-4,DFH-4E,and DFH-5.The DFH-4 satellite platform is a large geostationary orbit satellite platform,knownfor its ample capacity and extended service life.It serves various purposes such ashigh-capacitycommunication/broadcast,video/audiobroadcasting,datarelay,regional mo

332、bile communication,and high-earth orbit remote sensing.The DFH-4Esatellite platform builds upon the DFH-4 platform,enhancing its capabilities withtechnologies such as electric propulsion,high-power distribution,multi-screencommunication cabins,large payload structures,efficient thermal control ofcom

333、munication cabins,and dual-antenna overlapping compression and deployment.The DFH-5 satellite platform features a modular solar array design and a truss-basedmain load-bearing structure,enhancing its adaptability to different payloads.Forpower supply and distribution,it adopts advanced 2D secondary deploymentsemi-rigid solar wings,high-energy lithium-ion batteries,and next-gen powercontrollers,boo