The application of Non-Orthogonal Multiple Access(NOMA) technology into satelliteaerial-ground integrated networks can meet the requirements of ultra-high rate and massive connectivity for the Sixth-Generation(6G) com...The application of Non-Orthogonal Multiple Access(NOMA) technology into satelliteaerial-ground integrated networks can meet the requirements of ultra-high rate and massive connectivity for the Sixth-Generation(6G) communication systems. We consider an uplink NOMA scenario for such a satellite-aerial-ground integrated network where multiple users communicate with satellite under the help of an Unmanned Aerial Vehicle(UAV) as an aerial relay equipped with a phased array. Supposing that buffer-aided decode-and-forward protocol is adopted at the UAV relay, we first formulate an optimization problem to maximize Ergodic Sum Rate(ESR) of the considered system subject to individual power constraint and quality-of-service constraint of each user.Then, with known imperfect channel state information of each user, we propose a joint power allocation and robust Beam Forming(BF) iterative algorithm to maximize ESR for the user-to-UAV link. Besides, to take the advantages of Free-Space Optical(FSO) and millimeter Wave(mmWave)communications, we present a switch-based hybrid FSO/mmWave scheme and a robust BF algorithm for the UAV-to-satellite link to achieve higher rate. Moreover, a closed-form ESR expression is derived. Finally, the effectiveness and correctness of the proposed solutions are verified by numerical simulations, and the performance evaluation results show that the proposed solutions not only achieve performance enhancement and robustness, but also outperform the orthogonal multiple access significantly.展开更多
For the sake of meeting the demand of data rates at terabit(Tbit)per second scale in future networks,the terahertz(THz)band is widely accepted as one of the potential key enabling technologies for next generation wire...For the sake of meeting the demand of data rates at terabit(Tbit)per second scale in future networks,the terahertz(THz)band is widely accepted as one of the potential key enabling technologies for next generation wireless communication systems.With the progressive development of THz devices,regrading THz communications at system level is increasing crucial and captured the interest of plenty of researchers.Within this scope,THz channel modeling serves as an indispensable and fundamental element.By surveying the latest literature findings,this paper reviews the problem of channel modeling in the THz band,with an emphasis on molecular absorption loss,misalignment fading and multipath fading,which are major influence factors in the THz channel modeling.Then,we focus on simulators and experiments in the THz band,after which we give a brief introduction on applications of THz channel models with respects to capacity,security,and sensing as examples.Finally,we discuss some key issues in the future THz channel modeling.展开更多
In the upcoming sixth-generation(6G)era,the demand for constructing a wide-area time-sensitive Internet of Things(IoT)continues to increase.As conventional cellular technologies are difficult to directly use for wide-...In the upcoming sixth-generation(6G)era,the demand for constructing a wide-area time-sensitive Internet of Things(IoT)continues to increase.As conventional cellular technologies are difficult to directly use for wide-area time-sensitive IoT,it is beneficial to use non-terrestrial infrastructures,including satellites and unmanned aerial vehicles(UAVs).Thus,we can build a non-terrestrial network(NTN)using a cell-free architecture.Driven by the time-sensitive requirements and uneven distribution of IoT devices,the NTN must be empowered using mobile edge computing(MEC)while providing oasisoriented on-demand coverage for devices.Nevertheless,communication and MEC systems are coupled with each other under the influence of a complex propagation environment in the MEC-empowered NTN,which makes it difficult to coordinate the resources.In this study,we propose a process-oriented framework to design communication and MEC systems in a time-division manner.In this framework,large-scale channel state information(CSI)is used to characterize the complex propagation environment at an affordable cost,where a nonconvex latency minimization problem is formulated.Subsequently,the approximated problem is provided,and it can be decomposed into sub-problems.These sub-problems are then solved iteratively.The simulation results demonstrated the superiority of the proposed process-oriented scheme over other algorithms,implied that the payload deployments of UAVs should be appropriately predesigned to improve the efficiency of using resources,and confirmed that it is advantageous to integrate NTN with MEC for wide-area time-sensitive IoT.展开更多
Intent-Based Networks(IBNs),which are originally proposed to introduce Artificial Intelligence(AI)into the sixth-generation(6G)wireless networks,can effectively solve the challenges of traditional networks in terms of...Intent-Based Networks(IBNs),which are originally proposed to introduce Artificial Intelligence(AI)into the sixth-generation(6G)wireless networks,can effectively solve the challenges of traditional networks in terms of efficiency,flexibility,and security.IBNs are mainly used to transform users’business intent into network configuration,operation,and maintenance strategies,which are prominent for designing the AI-enabled 6G networks.In particular,in order to meet the massive,intelligent service demands and overcome the time-varying radio propagation,IBNs can continuously learn and adapt to the time-varying network environment based on the massive collected network data in real-time.From the aspects of both the core network and radio access network,this article comprehensively surveys the architectures and key techniques of IBNs for 6G.In particular,the demonstration platforms of IBNs,such as the Apstra Operating System,Forward Networks Verification Platform,and One Convergence Service Interaction Platform,are presented.Moreover,the industrial development of IBNs is elaborated,including the emerging new products and startups to solve the problems of open data platforms,automated network operations,and preemptive network fault diagnosis.Finally,several open issues and challenges are identified as well to spur future researches.展开更多
Aerial access networks have been envisioned as a promising 6G solution to enhance the ground communication systems in both coverage and capacity. To better utilize the spectrum and fully explore different channel char...Aerial access networks have been envisioned as a promising 6G solution to enhance the ground communication systems in both coverage and capacity. To better utilize the spectrum and fully explore different channel characteristics, this paper constructs an integrated network comprising the High Altitude Platform(HAP) and Unmanned Air Vehicles(UAVs) with the NonOrthogonal Multiple Access(NOMA) technology. In order to improve the transmission quality of images and videos, a power management scheme is proposed to minimize the distortion of the transmissions from the HAP and UAVs to the terminals. The power control is formulated as a non-convex problem constrained by the maximal transmit power and the minimal terminal rate requirements. The variable substitution and the first-order Tailor’s expansion is used to transform it into a sequence of convex problems, which are subsequently solved through the gradient projection method. Simulation demonstrates the signal distortion and error rate improvement achieved by the proposed algorithm.展开更多
This paper presents a co-time co-frequency fullduplex(CCFD)massive multiple-input multiple-output(MIMO)system to meet high spectrum efficiency requirements for beyond the fifth-generation(5G)and the forthcoming the si...This paper presents a co-time co-frequency fullduplex(CCFD)massive multiple-input multiple-output(MIMO)system to meet high spectrum efficiency requirements for beyond the fifth-generation(5G)and the forthcoming the sixth-generation(6G)networks.To achieve equilibrium of energy consumption,system resource utilization,and overall transmission capacity,an energy-efficient resource management strategy concerning power allocation and antenna selection is designed.A continuous quantum-inspired termite colony optimization(CQTCO)algorithm is proposed as a solution to the resource management considering the communication reliability while promoting energy conservation for the CCFD massive MIMO system.The effectiveness of CQTCO compared with other algorithms is evaluated through simulations.The results reveal that the proposed resource management scheme under CQTCO can obtain a superior performance in different communication scenarios,which can be considered as an eco-friendly solution for promoting reliable and efficient communication in future wireless networks.展开更多
Unmanned aerial vehicles(UAVs),characterized by their low cost and operational flexibility,have been increasingly deployed across civilian,military,and commercial applications.To improve the coverage and connectivity,...Unmanned aerial vehicles(UAVs),characterized by their low cost and operational flexibility,have been increasingly deployed across civilian,military,and commercial applications.To improve the coverage and connectivity,UAVs can be utilized to realize the comprehensive spatial coverage for the sixth-generation mobile networks.However,the private data in UAV networks is easy to be exposed due to the light-of-sight links and openness of wireless transmission.Covert communication as an emerging technique has shown its superiority in hiding the transmission behavior,which can further enhance the security of UAV networks compared with the traditional physical-layer security.Therefore,in this article,we present a survey on the recent advanced research about covert UAV communications.First,the roles of UAVs for covert communications are described.Then,the covert UAV communications with different uncertainties are introduced.Moreover,the wireless techniques for covert UAV communications are explored.In addition,we point out the applications in covert UAV communications.Finally,the open research issues concerning practical scenarios and promising applications are highlighted.展开更多
The sixth-generation(6G)wireless communication system is envisioned be cable of providing highly dependable services by integrating with native reliable and trustworthy functionalities.Zero-trust vehicular networks is...The sixth-generation(6G)wireless communication system is envisioned be cable of providing highly dependable services by integrating with native reliable and trustworthy functionalities.Zero-trust vehicular networks is one of the typical scenarios for 6G dependable services.Under the technical framework of vehicle-and-roadside collaboration,more and more on-board devices and roadside infrastructures will communicate for information exchange.The reliability and security of the vehicle-and-roadside collaboration will directly affect the transportation safety.Considering a zero-trust vehicular environment,to prevent malicious vehicles from uploading false or invalid information,we propose a malicious vehicle identity disclosure approach based on the Shamir secret sharing scheme.Meanwhile,a two-layer consortium blockchain architecture and smart contracts are designed to protect the identity and privacy of benign vehicles as well as the security of their private data.After that,in order to improve the efficiency of vehicle identity disclosure,we present an inspection policy based on zero-sum game theory and a roadside unit incentive mechanism jointly using contract theory and subjective logic model.We verify the performance of the entire zero-trust solution through extensive simulation experiments.On the premise of protecting the vehicle privacy,our solution is demonstrated to significantly improve the reliability and security of 6G vehicular networks.展开更多
Simultaneously transmitting and reflecting reconfigurable intelligent surfaces(STAR-RISs)have been attracting significant attention in both academia and industry for their advantages of achieving 360°coverage and...Simultaneously transmitting and reflecting reconfigurable intelligent surfaces(STAR-RISs)have been attracting significant attention in both academia and industry for their advantages of achieving 360°coverage and enhanced degrees-of-freedom.This article first identifies the fundamentals of STAR-RIS,by discussing the hardware models,channel models,and signal models.Then,three representative categorizing approaches for STAR-RISs are introduced from the phase-shift,directional,and energy consumption perspectives.Furthermore,the beamforming design of STAR-RISs is investigated for both independent and coupled phase-shift cases.As a recent advance,a general optimization framework,which has high compatibility and provable optimality regardless of the application scenarios,is proposed.As a further advance,several promising applications are discussed to demonstrate the potential benefits of applying STAR-RISs in sixth-generation wireless communication.Lastly,a few future directions and research opportunities are highlighted.展开更多
Russian writer Nicholas Tempered （1934） provided generations Ostrovski＇s novel How the Steel Was of Chinese youth with a widely admired role model： a young devoted communist soldier, Pawel Korchagin, whose image o...Russian writer Nicholas Tempered （1934） provided generations Ostrovski＇s novel How the Steel Was of Chinese youth with a widely admired role model： a young devoted communist soldier, Pawel Korchagin, whose image occupied a prominent place in the orthodoxy revolutionary education and literary imagination during Mao＇s era. Over the past decade, Pawel Korchagin has regained his popularity in Chinese media, his name and image have been appropriated by numerous artists and filmmakers to help in portrayals of the new generation＇s self-fashioning. The various （unorthodox） interpretations recently attached to Pawel＇s heroic story reveal a huge gap between Maoist ideology and the post-Mao ideas. This paper looks into the intricate relationships between Pawel Korchagin＇s revolutionary past and his varied contemporary representations. By doing so, I hope to gain a better understanding of the cultural politics of appropriating Mao＇s legacy to create new meanings for a changing Chinese society One example on which this paper focuses is the sixth-generation director Lu Xuechang＇s film Becoming a Man （1997）, which rewrites the revolutionary Bildungsroman of Pawel in a startling different context.展开更多
基金co-supported by the Key International Cooperation Research Project,China(No.61720106003)Jiangsu Province Science and Technology Project,China(No.BE2021031)+4 种基金the Shanghai Aerospace Science and Technology Innovation Foundation,China(No.SAST2019-095)NUPTSF(No.NY220111)the Research Project of Science and Technology on Complex Electronic System Simulation Laboratory,China(No.DXZT-JC-ZZ-2019-009)the National Natural Science Foundation of China(No.61801234)the Postgraduate Research and Practice Innovation Program of Jiangsu Province,China(No.KYCX210739)。
文摘The application of Non-Orthogonal Multiple Access(NOMA) technology into satelliteaerial-ground integrated networks can meet the requirements of ultra-high rate and massive connectivity for the Sixth-Generation(6G) communication systems. We consider an uplink NOMA scenario for such a satellite-aerial-ground integrated network where multiple users communicate with satellite under the help of an Unmanned Aerial Vehicle(UAV) as an aerial relay equipped with a phased array. Supposing that buffer-aided decode-and-forward protocol is adopted at the UAV relay, we first formulate an optimization problem to maximize Ergodic Sum Rate(ESR) of the considered system subject to individual power constraint and quality-of-service constraint of each user.Then, with known imperfect channel state information of each user, we propose a joint power allocation and robust Beam Forming(BF) iterative algorithm to maximize ESR for the user-to-UAV link. Besides, to take the advantages of Free-Space Optical(FSO) and millimeter Wave(mmWave)communications, we present a switch-based hybrid FSO/mmWave scheme and a robust BF algorithm for the UAV-to-satellite link to achieve higher rate. Moreover, a closed-form ESR expression is derived. Finally, the effectiveness and correctness of the proposed solutions are verified by numerical simulations, and the performance evaluation results show that the proposed solutions not only achieve performance enhancement and robustness, but also outperform the orthogonal multiple access significantly.
基金supported by Zhejiang Lab(no.2020LC0AD01 and no.2020LC0AA03)the National Key Research and Development Program of China(2020YFB1805700,2018YFB1801500&2018YFB2201700)+1 种基金the National Natural Science Foundation of China under Grant 61771424the Natural Science Foundation of Zhejiang Province under Grant LZ18F010001.
文摘For the sake of meeting the demand of data rates at terabit(Tbit)per second scale in future networks,the terahertz(THz)band is widely accepted as one of the potential key enabling technologies for next generation wireless communication systems.With the progressive development of THz devices,regrading THz communications at system level is increasing crucial and captured the interest of plenty of researchers.Within this scope,THz channel modeling serves as an indispensable and fundamental element.By surveying the latest literature findings,this paper reviews the problem of channel modeling in the THz band,with an emphasis on molecular absorption loss,misalignment fading and multipath fading,which are major influence factors in the THz channel modeling.Then,we focus on simulators and experiments in the THz band,after which we give a brief introduction on applications of THz channel models with respects to capacity,security,and sensing as examples.Finally,we discuss some key issues in the future THz channel modeling.
基金the National Key R&D Program of China(2018YFA0701601 and 2020YFA0711301)the National Natural Science Foundation of China(61771286,61941104,and 61922049)the Tsinghua University-China Mobile Communications Group Co.,Ltd.Joint Institute.
文摘In the upcoming sixth-generation(6G)era,the demand for constructing a wide-area time-sensitive Internet of Things(IoT)continues to increase.As conventional cellular technologies are difficult to directly use for wide-area time-sensitive IoT,it is beneficial to use non-terrestrial infrastructures,including satellites and unmanned aerial vehicles(UAVs).Thus,we can build a non-terrestrial network(NTN)using a cell-free architecture.Driven by the time-sensitive requirements and uneven distribution of IoT devices,the NTN must be empowered using mobile edge computing(MEC)while providing oasisoriented on-demand coverage for devices.Nevertheless,communication and MEC systems are coupled with each other under the influence of a complex propagation environment in the MEC-empowered NTN,which makes it difficult to coordinate the resources.In this study,we propose a process-oriented framework to design communication and MEC systems in a time-division manner.In this framework,large-scale channel state information(CSI)is used to characterize the complex propagation environment at an affordable cost,where a nonconvex latency minimization problem is formulated.Subsequently,the approximated problem is provided,and it can be decomposed into sub-problems.These sub-problems are then solved iteratively.The simulation results demonstrated the superiority of the proposed process-oriented scheme over other algorithms,implied that the payload deployments of UAVs should be appropriately predesigned to improve the efficiency of using resources,and confirmed that it is advantageous to integrate NTN with MEC for wide-area time-sensitive IoT.
基金This work was supported in part by the State Major Science and Technology Special Project(Grant No.2018ZX03001002-004 and 2018ZX03001023)the National Natural Science Foundation of China under No.61921003,61925101,61831002,and 61901044+1 种基金the Beijing Natural Science Foundation under No.JQ18016and the National Program for Special Support of Eminent Professionals.
文摘Intent-Based Networks(IBNs),which are originally proposed to introduce Artificial Intelligence(AI)into the sixth-generation(6G)wireless networks,can effectively solve the challenges of traditional networks in terms of efficiency,flexibility,and security.IBNs are mainly used to transform users’business intent into network configuration,operation,and maintenance strategies,which are prominent for designing the AI-enabled 6G networks.In particular,in order to meet the massive,intelligent service demands and overcome the time-varying radio propagation,IBNs can continuously learn and adapt to the time-varying network environment based on the massive collected network data in real-time.From the aspects of both the core network and radio access network,this article comprehensively surveys the architectures and key techniques of IBNs for 6G.In particular,the demonstration platforms of IBNs,such as the Apstra Operating System,Forward Networks Verification Platform,and One Convergence Service Interaction Platform,are presented.Moreover,the industrial development of IBNs is elaborated,including the emerging new products and startups to solve the problems of open data platforms,automated network operations,and preemptive network fault diagnosis.Finally,several open issues and challenges are identified as well to spur future researches.
基金supported by the National Natural Science Foundation of China(61901115,62171188)。
文摘Aerial access networks have been envisioned as a promising 6G solution to enhance the ground communication systems in both coverage and capacity. To better utilize the spectrum and fully explore different channel characteristics, this paper constructs an integrated network comprising the High Altitude Platform(HAP) and Unmanned Air Vehicles(UAVs) with the NonOrthogonal Multiple Access(NOMA) technology. In order to improve the transmission quality of images and videos, a power management scheme is proposed to minimize the distortion of the transmissions from the HAP and UAVs to the terminals. The power control is formulated as a non-convex problem constrained by the maximal transmit power and the minimal terminal rate requirements. The variable substitution and the first-order Tailor’s expansion is used to transform it into a sequence of convex problems, which are subsequently solved through the gradient projection method. Simulation demonstrates the signal distortion and error rate improvement achieved by the proposed algorithm.
基金supported by the Ph.D.Student Research and Innovation Fund of the Fundamental Research Funds for the Central Universities(3072020GIP0803)Heilongjiang Province Key Laboratory Fund of High Accuracy Satellite Navigation and Marine Application Laboratory(HKL-2020-Y01)+2 种基金the National Natural Science Foundation of China(61571149)the Initiation Fund for Postdoctoral Research in Heilongjiang Province(LBH-Q19098)the Key Laboratory of Advanced Marine Communication and Information Technology,Ministry of Industry and Information Technology。
文摘This paper presents a co-time co-frequency fullduplex(CCFD)massive multiple-input multiple-output(MIMO)system to meet high spectrum efficiency requirements for beyond the fifth-generation(5G)and the forthcoming the sixth-generation(6G)networks.To achieve equilibrium of energy consumption,system resource utilization,and overall transmission capacity,an energy-efficient resource management strategy concerning power allocation and antenna selection is designed.A continuous quantum-inspired termite colony optimization(CQTCO)algorithm is proposed as a solution to the resource management considering the communication reliability while promoting energy conservation for the CCFD massive MIMO system.The effectiveness of CQTCO compared with other algorithms is evaluated through simulations.The results reveal that the proposed resource management scheme under CQTCO can obtain a superior performance in different communication scenarios,which can be considered as an eco-friendly solution for promoting reliable and efficient communication in future wireless networks.
基金supported by the National Natural Science Foundation of China(Nos.U23A20271 and 62325103).
文摘Unmanned aerial vehicles(UAVs),characterized by their low cost and operational flexibility,have been increasingly deployed across civilian,military,and commercial applications.To improve the coverage and connectivity,UAVs can be utilized to realize the comprehensive spatial coverage for the sixth-generation mobile networks.However,the private data in UAV networks is easy to be exposed due to the light-of-sight links and openness of wireless transmission.Covert communication as an emerging technique has shown its superiority in hiding the transmission behavior,which can further enhance the security of UAV networks compared with the traditional physical-layer security.Therefore,in this article,we present a survey on the recent advanced research about covert UAV communications.First,the roles of UAVs for covert communications are described.Then,the covert UAV communications with different uncertainties are introduced.Moreover,the wireless techniques for covert UAV communications are explored.In addition,we point out the applications in covert UAV communications.Finally,the open research issues concerning practical scenarios and promising applications are highlighted.
基金supported in part by the National Key R&D Program of China (No.2020YFB1807802)the National Natural Science Foundation of China (Grant Nos.61971148,U22A2054).
文摘The sixth-generation(6G)wireless communication system is envisioned be cable of providing highly dependable services by integrating with native reliable and trustworthy functionalities.Zero-trust vehicular networks is one of the typical scenarios for 6G dependable services.Under the technical framework of vehicle-and-roadside collaboration,more and more on-board devices and roadside infrastructures will communicate for information exchange.The reliability and security of the vehicle-and-roadside collaboration will directly affect the transportation safety.Considering a zero-trust vehicular environment,to prevent malicious vehicles from uploading false or invalid information,we propose a malicious vehicle identity disclosure approach based on the Shamir secret sharing scheme.Meanwhile,a two-layer consortium blockchain architecture and smart contracts are designed to protect the identity and privacy of benign vehicles as well as the security of their private data.After that,in order to improve the efficiency of vehicle identity disclosure,we present an inspection policy based on zero-sum game theory and a roadside unit incentive mechanism jointly using contract theory and subjective logic model.We verify the performance of the entire zero-trust solution through extensive simulation experiments.On the premise of protecting the vehicle privacy,our solution is demonstrated to significantly improve the reliability and security of 6G vehicular networks.
基金Project supported by CHIST-ERA(SUNRISE CHIST-ERA-20-SICT-005)the Engineering and Physical Sciences Research Council(No.EP/W035588/1)the PHC Alliance Franco-British Joint Research Programme(No.822326028)。
文摘Simultaneously transmitting and reflecting reconfigurable intelligent surfaces(STAR-RISs)have been attracting significant attention in both academia and industry for their advantages of achieving 360°coverage and enhanced degrees-of-freedom.This article first identifies the fundamentals of STAR-RIS,by discussing the hardware models,channel models,and signal models.Then,three representative categorizing approaches for STAR-RISs are introduced from the phase-shift,directional,and energy consumption perspectives.Furthermore,the beamforming design of STAR-RISs is investigated for both independent and coupled phase-shift cases.As a recent advance,a general optimization framework,which has high compatibility and provable optimality regardless of the application scenarios,is proposed.As a further advance,several promising applications are discussed to demonstrate the potential benefits of applying STAR-RISs in sixth-generation wireless communication.Lastly,a few future directions and research opportunities are highlighted.
文摘Russian writer Nicholas Tempered （1934） provided generations Ostrovski＇s novel How the Steel Was of Chinese youth with a widely admired role model： a young devoted communist soldier, Pawel Korchagin, whose image occupied a prominent place in the orthodoxy revolutionary education and literary imagination during Mao＇s era. Over the past decade, Pawel Korchagin has regained his popularity in Chinese media, his name and image have been appropriated by numerous artists and filmmakers to help in portrayals of the new generation＇s self-fashioning. The various （unorthodox） interpretations recently attached to Pawel＇s heroic story reveal a huge gap between Maoist ideology and the post-Mao ideas. This paper looks into the intricate relationships between Pawel Korchagin＇s revolutionary past and his varied contemporary representations. By doing so, I hope to gain a better understanding of the cultural politics of appropriating Mao＇s legacy to create new meanings for a changing Chinese society One example on which this paper focuses is the sixth-generation director Lu Xuechang＇s film Becoming a Man （1997）, which rewrites the revolutionary Bildungsroman of Pawel in a startling different context.
