Satellite Communications with 5G, B5G, and 6G: Challenges and Prospects

Satellite communications, pivotal for global connectivity, are increasingly converging with cutting-edge mobile networks, notably 5G, B5G, and 6G. This amalgamation heralds the promise of universal, high-velocity communication, yet it is not without its challenges. Paramount concerns encompass spectrum allocation, the harmonization of network architectures, and inherent latency issues in satellite transmissions. Potential mitigations, such as dynamic spectrum sharing and the deployment of edge computing, are explored as viable solutions. Looking ahead, the advent of quantum communications within satellite frameworks and the integration of AI spotlight promising research trajectories. These advancements aim to foster a seamless and synergistic coexistence between satellite communications and next-gen mobile networks.

System Integration of Terrestrial Mobile Communication and Satellite Communication——The Trends, Challenges and Key Technologies in B5G and 6G

Mobile communication standards have been developed into a new era of B5G and 6G.In recent years,low earth orbit(LEO)satellites and space Internet have become hot topics.The integrated satellite and terrestrial systems have been widely discussed by industries and academics,and even are expected to be applied in those huge constellations in construction.This paper points out the trends of two stages towards system integration of the terrestrial mobile communication and the satellite communications:to be compatible with 5G,and to be integrated within 6G.Based on analysis of the challenges of both stages,key technologies are thereafter analyzed in detail,covering both air interface currently discussed in 3GPP for B5G and also novel network architecture and related transmission technologies toward future 6G.

The Spread Spectrum GFDM Schemes for Integrated Satellite-Terrestrial Communication System

Recently, integrated Satellite-Terrestrial(S-T) communication system, especially the integration of satellite communication with 5G/6G, is regarded as a research hotpot. Future integrated S-T communication systems are demanding a more compatible and robust physical layer waveform. Considering physical layer access waveform design, this paper proposed a novel Spread Spectrum Generalized Frequency Division Multiplexing(SS-GFDM) scheme for integrated S-T communication system. Traditional GFDM has many advantages such as excellent adaptability and low out-ofband(OOB) radiation. However, because of intrinsic inter carrier interference(ICI) and low signal-to-noise ratio(SNR), the multiple access performance is degraded. In this paper, we introduced CDMA technology into GFDM. Two different spread spectrum modes, Cyclic Code Shift Keying(CCSK) soft spread spectrum and Direct Sequence Spread Spectrum(DSSS), are considered and compared in this paper to illustrate the benefits of GFDM-CDMA in low SNR scenario. Moreover, this scheme integrates the slot-ALOHA protocol with GFDM-CDMA, which extends access freedom in frequency, time and code domain. The simulation and analysis results show that the proposed GFDM-CDMA scheme reduces the performance degradation caused by interference. It is effective in typical satellite channel with low complexity. Meanwhile, the peak-average-power-ratio(PAPR) and access performance has been enhanced significantly.

Covert Communication in Integrated High Altitude Platform Station Terrestrial Networks

In recent years,Internet of Things(IoT)technology has emerged and gradually sprung up.As the needs of largescale IoT applications cannot be satisfied by the fifth generation(5G)network,wireless communication network needs to be developed into the sixth generation(6G)network.However,with the increasingly prominent security problems of wireless communication networks such as 6G,covert communication has been recognized as one of the most promising solutions.Covert communication can realize the transmission of hidden information between both sides of communication to a certain extent,which makes the transmission content and transmission behavior challenging to be detected by noncooperative eavesdroppers.In addition,the integrated high altitude platform station(HAPS)terrestrial network is considered a promising development direction because of its flexibility and scalability.Based on the above facts,this article investigates the covert communication in an integrated HAPS terrestrial network,where a constant power auxiliary node is utilized to send artificial noise(AN)to realize the covert communication.Specifically,the covert constraint relationship between the transmitting and auxiliary nodes is derived.Moreover,the closed-form expressions of outage probability(OP)and effective covert communication rate are obtained.Finally,numerical results are provided to verify our analysis and reveal the impacts of critical parameters on the system performance.

Design and verification of a satellite-terrestrial integrated IP network model for the Global Energy Interconnection

In order to meet the pressing demand for wide-area communication required by the Global Energy Interconnection(GEI),accelerating the construction of satellite-terrestrial Integra怕d networks that can achieve network extension and seamless global coverage has become the focus of power communication tech no logy development.In this study,we propose a satellite-terrestrial integrated network model that can support interconnection and interoperation on the IP layer between the satellite system and the怕rrestrial segment of the existing power communication system.First,the composition and function of the satellite-terrestrial collaborative network are explained.Then,the IP-based protocol stack is described,and a typical applicati on experime nt is con ducted to illustrate the particular process of this protocol stack.Fin ally,a use case of IP interconn ection that depends on GEO satellite communication is detailed.The experime ntal study has showed that the satellite-terrestrial collaborative network can efficiently support various IP applications for the GEI.

Double-Edge Intelligent Integrated Satellite Terrestrial Networks

The efficient integration of satellite and terrestrial networks has become an important component for 6 G wireless architectures to provide highly reliable and secure connectivity over a wide geographical area.As the satellite and cellular networks are developed separately these years,the integrated network should synergize the communication,storage,computation capabilities of both sides towards an intelligent system more than mere consideration of coexistence.This has motivated us to develop double-edge intelligent integrated satellite and terrestrial networks(DILIGENT).Leveraging the boost development of multi-access edge computing(MEC)technology and artificial intelligence(AI),the framework is entitled with the systematic learning and adaptive network management of satellite and cellular networks.In this article,we provide a brief review of the state-of-art contributions from the perspective of academic research and standardization.Then we present the overall design of the proposed DILIGENT architecture,where the advantages are discussed and summarized.Strategies of task offloading,content caching and distribution are presented.Numerical results show that the proposed network architecture outperforms the existing integrated networks.

Topology Discovery Sub-Layer for Integrated Terrestrial-Satellite Network Routing Schemes

With the booming development of terrestrial network, scaling terrestrial network over satellite network to build Integrated Terrestrial-Satellite Network(ITSN) and meanwhile to provide the global Internet access, has become ever more attractive. Naturally, the widely and successfully used terrestrial routing protocols are the promising protocols to integrate the terrestrial and satellite networks. However, the terrestrial routing protocols, which rely on propagating routing messages to discover New Network Topology(NNT) in the terrestrial network with rare topology changes, will suffer from overly numerous routing messages in satellite network whose topology frequently changes as satellites move. In this paper, a Topology Discovery Sub-layer for ITSN Routing Schemes(TDS-IRS) is firstly proposed to avoid the propagation of numerous routing messages by taking advantage of the movement predictability of satellite and the requirements of routing schemes to discover NNT in advance of topology change. Secondly, a Weighted Perfect Matching based Topology Discovery(WPM-TD) model is designed to conduct the NNT discovery on the ground. Thirdly, this paper builds a testbed with real network devices and meanwhile interconnect that testbed with real Internet, to validate that RS-TDS can discover NNT immediately with the less on-board overhead compared with optimized routing schemes. Finally, different network scenarios are applied to validate the WPM-TD, i.e., the core module of TDS-IRS. Extensive experiments show WPM-TD can work efficiently, avoiding the invalid NNT discovery and decreasing 20% ~ 57% of potential topology changes, which can also improve up to 47% ~ 105% of network throughput.

The Impact of Delay in Software-Defined Integrated Terrestrial-Satellite Networks

Satellite communication networks have been evolving from standalone networks with ad-hoc infrastructures to possibly interconnected portions of a wider Future Internet architecture. Experts belonging to the fifth-generation(5 G) standardization committees are considering satellites as a technology to integrate in the 5 G environment. Software Defined Networking(SDN) is one of the paradigms of the next generation of mobile and fixed communications. It can be employed to perform different control functionalities, such as routing, because it allows traffic flow identification based on different parameters and traffic flow management in a centralized way. A centralized set of controllers makes the decisions and sends the corresponding forwarding rules for each traffic flow to the involved intermediate nodes that practically forward data up to the destination. The time to perform this process in integrated terrestrial-satellite networks could be not negligible due to satellite link delays. The aim of this paper is to introduce an SDN-based terrestrial satellite network architecture and to estimate the mean time to deliver the data of a new traffic flow from the source to the destination including the time required to transfer SDN control actions. The practical effect is to identify the maximum performance than can be expected.

Benefits Analysis of Beam Hopping in Satellite Mobile System with Unevenly Distributed Traffic

Satellite mobile system and space-airground integrated network have a prominent superiority in global coverage which plays a critical role in remote and non-land regions, as well as emergency communications. However, due to the gradual angle attenuations of the satellite antennas, it is difficult to achieve full frequency multiplex among different beams as terrestrial 5G network. Multi-color frequency reuse is widely adopted in both academic and industry. Beam hopping scheme has attracted the attention of researchers recently due to the allocation flexibility. In this paper, we focus on analyzing the performance benefits of beam hopping compared with multi-color frequency reuse scheme in non-uniform user and traffic distributions in satellite system. Aerial networks are also introduced to form a space-airground integrated network for coverage enhancement,and the capacity improvement is analyzed. Besides,additional improved techniques are provided to make comprehensive analysis and comparisons. Theoretical analysis and simulation results indicate that the beam hopping scheme has a prominent superiority in the system capacity compared with the traditional multicolor frequency reuse scheme in both satellite mobile system and future space-air-ground integrated network.

星地融合边云协同网络下的资源调度研究

通过边缘计算和云计算的优势互补,面向6G的星地融合网络能够实现资源的弹性分配和协同利用,满足数据处理的实时性和智能化要求。为了提升资源服务能力和用户体验质量,提出了星地融合边云协同网络架构。首先,阐述了三种不同边云协同模式下的资源调度方案,从时延、能耗和多目标优化的角度分析了不同场景下的资源调度策略。然后,对比了现有资源调度求解模型和算法的优势和局限性。最后,对基于边云协同的星地融合网络中的资源调度研究进行了总结与展望。

面向星地融合的6G云雾化自组网

低轨星座朝支持星上处理、功能可重构、星地协作和通信遥感导航控制等多任务一体化的方向演进,受限于星上信号处理和计算能力不足、星间链路容量不宽等瓶颈,迫切需要和具有强大云化处理与计算能力的陆地移动通信网络深度融合。为此,提出了面向星地融合的6G云雾化自组网的体系架构和协议体系,实现了低轨雾化卫星网络和陆地云化通信网络的协同融合,研究了基于星上雾化处理的通信遥感导航控制一体化波形和资源管理,以及云雾化协同的移动性管理和智能信息处理等关键技术,展望了未来的标准化工作和硬件试验。

卫星互联网星间激光通信的分析及建议

卫星通信和地面移动通信具有较强的互补性,卫星互联网是当前产业发展的热点,也是未来6G网络的重要组成部分。全球覆盖需要星间组网,但星间通信带宽需求与自由空间信道带来的不稳定性对空间承载网提出了新的挑战。对星间通信及其传输链路进行对比分析,提出了基于星间激光的光传送网络(OTN)承载方案,以充分发挥地面光通信的成熟产业链优势和规模经济优势,构建经济性、兼容性、扩展性强的星地一体化网络。最后展望了星间激光通信的技术演进方向,并提出了我国产业发展建议。

星地融合网络管控架构设计

星地融合网络的运行管控需要面向巨型星座和天地大尺度网络,实现对异构基础设施、分层立体网络、跨域多维资源、定制化业务服务的综合调度管理,管控对象多样,关系错综复杂,管控的协同性和高效性直接影响网络的服务能力。针对以上问题,基于网络为本、星网协同的理念,探索星座、网络、业务的协同管控机制,提出星地融合网络运行管控的总体架构,并详细设计管控中心功能,规划典型运行管理流程,分析其在巨型星座在轨管理和大尺度跨域网络管理等方面的适用性,为星地融合网络运行管控系统建设和系统运行管理提供技术支撑。

6G星地融合网络资源管理关键技术

卫星网络因具备弥补地面网络覆盖盲区的特性,成为6G网络实现泛在连接应用场景的关键技术之一。为了实现卫星网络和地面网络间高效的资源融合管理,首先简要介绍了星地融合网络的发展现状,总结了星地融合网络资源管理技术的研究现状以及面临的挑战。其次,对6G星地融合网络下的移动性管理、跨域多维资源管理和统一的空口协议设计等关键技术进行分析,并基于对现有研究的探讨给出解决方案。最后,对未来面向6G的星地融合网络资源管理的发展提出了新的展望。

面向天地一体化的确定性网络技术研究

卫星通信是未来通信领域的关键技术,低轨互联网星座是6G空天地海一体化网络的战略性基础设施,能够将当前通信网络扩展到全球近地区域。确定性网络技术是天基网络的重要技术之一,相比传统尽力而为的分组网络,确定性网络具有低时延、低抖动、低丢包率、高可靠的优势。概述了确定性网络当前的研究背景及现状,提出面向卫星通信的确定性网络架构,阐述了其关键技术,最后讨论了未来研究方向。

基于天基干扰绘图的星地一体化系统频谱共享研究

针对未来星地一体化系统中新入低轨道地球卫星(LEO)组件的用频需求和现任地面组件聚合干扰影响的问题,面向天基认知系统提出频谱感知和频谱数据库辅助的交织模式频谱共享方案。首先,针对低轨认知系统节点稀疏分布属性对频谱感知和干扰绘图带来的负面影响,提出“认知节点位置”概念。其次,研究低轨认知系统的双门限混合频谱感知和干扰绘图的机制,构建频谱数据库。最后,面向多状态虚拟网络模型,提出卫星组件上行频谱共享方案,实现LEO组件和地面组件之间的同频共存工作。仿真结果表明,所提双门限混合感知和干扰绘图能以较低密度的低轨认知节点实现高可靠性的频谱空间态势认知;所提基于频谱数据库和交织模式的LEO组件协作接入方案可以实现与地面组件的频谱共享,且不会显著增加LEO组件的端到端时延。

天地一体化新路径:手机直连卫星发展热点、挑战与关键技术

手机直连卫星作为未来实现天地一体化融合的一种潜在技术手段,得到了产业界和学术界的广泛关注。与传统的卫星移动通信相比,当前手机直连卫星技术存在诸多挑战。针对基于同步轨道卫星和非同步轨道卫星的两种手机直连技术路线,分析国内外发展现状、系统组成架构,并从空口侧、卫星侧、网络侧和终端侧梳理技术挑战,提出星地同步、星载超大阵面天线、星地异构网络漫游等若干解决方案,为手机直连卫星技术的发展提供技术支撑。最后对手机直连卫星的发展进行展望。

星地融合网络中基于无监督图学习的卫星切换方法研究

随着未来6G移动通信研究的快速发展,星地融合通信将是满足全域覆盖、泛在接入的重要技术。在星地融合网络中切换决策直接影响网络性能与服务持续性,现有切换算法主要通过实时监测候选卫星状态,计算权重进行切换判决,难以适应高动态星地网络中时空周期异步的切换决策。提出一种基于无监督图学习的卫星切换方法,引入卫星覆盖时空图表征网络连接关系,设计前向蚂蚁和后向蚂蚁发现并反馈的信息素感知机制,建立图学习模型,挖掘卫星覆盖时空图中卫星节点、用户节点与连接关系之间的隐式特征信息和拓扑信息,将切换决策问题转化为求解节点和边之间的连接关系概率,同步切换决策周期。仿真结果验证了所提卫星切换方法具有较快的收敛速度,切换时延降低20%。

空间信息网络时变图建模方法

空间信息网络是星地融合网络中一个重要组成部分,其拓扑具有时变性和可预测性。采用一个合适的时变图模型来表征时变的空间信息网络,对于空间信息网络性能分析至关重要。首先阐述了空间信息网络的特性,然后介绍了多种空间信息网络时变图模型的建模方法,包括快照序列图、时间扩展图、存储时间聚合图和多功能时间扩展图,并且分析了它们的特征和优缺点,为6G星地融合网络的研究奠定基础,为网络性能分析提供了理论支撑。

星地融合下的手机直连关键技术研究

当前,大众用户和行业用户对星地融合通信的需求不断演进,以实现无缝覆盖与随时随地接入,集成卫星和地面通信能力将是未来手机终端的发展方向。首先介绍了手机直连的应用场景、国内外发展路径和相关技术方案;其次,针对3GPP NTN标准化技术方案,分析了实现手机直连的组网架构和空口关键技术方案,并探讨了卫星通信场景下多模终端在天线能力、语音能力及节能方面的需求及潜在改进方案;最后阐述了手机直连频谱资源及挑战,为星地融合手机直连终端通信设计提供参考。