Orthogonal time frequency space(OTFS)modulation has been widely considered for high-mobility scenarios.Satellite-to-ground communications have recently received much attention as a typical high-mobility scenario and f...Orthogonal time frequency space(OTFS)modulation has been widely considered for high-mobility scenarios.Satellite-to-ground communications have recently received much attention as a typical high-mobility scenario and face great challenges due to the high Doppler shift.To enable reliable communications and high spectral efficiency in satellite mobile communications,we evaluate OTFS modulation performance for geostationary Earth orbit and low Earth orbit satellite-to-ground channels at sub-6-GHz and millimeter-wave bands in both lineof-sight and non-line-of-sight cases.The minimum mean squared error with successive detection(MMSE-SD)is used to improve the bit error rate performance.The adaptability of OTFS and the signal detection technologies in satellite-to-ground channels are analyzed.Simulation results confirm the feasibility of applying OTFS modulation to satellite-to-ground communications with high mobility.Because full diversity in the delay-Doppler domain can be explored,different terminal movement velocities do not have a significant impact on the performance of OTFS modulation,and OTFS modulation can achieve better performance compared with classical orthogonal frequency division multiplexing in satellite-to-ground channels.It is found that MMSE-SD can improve the performance of OTFS modulation compared with an MMSE equalizer.展开更多
Channel prediction is critical to address the channel aging issue in mobile scenarios.Existing channel prediction techniques are mainly designed for discrete channel prediction,which can only predict the future channe...Channel prediction is critical to address the channel aging issue in mobile scenarios.Existing channel prediction techniques are mainly designed for discrete channel prediction,which can only predict the future channel in a fixed time slot per frame,while the other intra-frame channels are usually recovered by interpolation.However,these approaches suffer from a serious interpolation loss,especially for mobile millimeter-wave communications.To solve this challenging problem,we propose a tensor neural ordinary differential equation(TN-ODE)based continuous-time channel prediction scheme to realize the direct prediction of intra-frame channels.Specifically,inspired by the recently developed continuous mapping model named neural ODE in the field of machine learning,we first utilize the neural ODE model to predict future continuous-time channels.To improve the channel prediction accuracy and reduce computational complexity,we then propose the TN-ODE scheme to learn the structural characteristics of the high-dimensional channel by low-dimensional learnable transform.Simulation results show that the proposed scheme is able to achieve higher intra-frame channel prediction accuracy than existing schemes.展开更多
This paper presents an analysis and validation by advanced system simulation of compact and low-cost six-port transceivers for future wireless local area networks （WLANs） operating at millimeter-wave frequencies. To...This paper presents an analysis and validation by advanced system simulation of compact and low-cost six-port transceivers for future wireless local area networks （WLANs） operating at millimeter-wave frequencies. To obtain realistic simulation results, a six-port model based on the measurement results of a fabricated V-band hybrid coupler, the core component, is used. A frequency-division multiplexing scheme is used by introducing four quadrature phase-shift keying （QPSK） channels in the wireless communication link. The data rate achieved is about 4 Gbit/s. The operating frequency is in the 60-64 GHz unlicensed band. Bit error rate （BER） results are presented, and a comparison is made between single-carrier and multicarrier architectures. The proposed wireless system can be considered an efficient candidate for millimeter-wave communication systems operating at quasi-optical data rates.展开更多
This paper provides a comprehensive survey of the impact of the emerging communication technique, non-orthogonal multiple access （NOMA）, on future wireless networks. Particularly, how the NOMA principle affects the ...This paper provides a comprehensive survey of the impact of the emerging communication technique, non-orthogonal multiple access （NOMA）, on future wireless networks. Particularly, how the NOMA principle affects the design of the generation multiple access techniques is introduced first. Then the applications of NOMA to other advanced communication techniques, such as wireless caching, multiple-input multiple-output techniques, millimeter-wave communications, and cooperative relaying, are discussed. The impact of NOMA on communication systems beyond cellular networks is also illustrated, through the examples of digital TV, satellite communications, vehicular networks, and visible light communications. Finally, the study is concluded with a discussion of important research challenges and promising future directions in NOMA.展开更多
Hybrid precoding is a cost-effective approach to support directional transmissions for millimeter-wave(mmWave)communications,but its precoder design is highly complicated.In this paper,we propose a new hybrid precoder...Hybrid precoding is a cost-effective approach to support directional transmissions for millimeter-wave(mmWave)communications,but its precoder design is highly complicated.In this paper,we propose a new hybrid precoder implementation,namely the double phase shifter(DPS)implementation,which enables highly tractable hybrid precoder design.Efficient algorithms are then developed for two popular hybrid precoder structures,i.e.,the fully-and partially-connected structures.For the fully-connected one,the RF-only precoding and hybrid precoding problems are formulated as a least absolute shrinkage and selection operator problem and a low-rank matrix approximation problem,respectively.In this way,computationally efficient algorithms are provided to approach the performance of the fully digital one with a small number of radio frequency(RF)chains.On the other hand,the hybrid precoder design in the partially-connected structure is identified as an eigenvalue problem.To enhance the performance of this cost-effective structure,dynamic mapping from RF chains to antennas is further proposed,for which a greedy algorithm and a modified K-means algorithm are developed.Simulation results demonstrate the performance gains of the proposed hybrid precoding algorithms over existing ones.It shows that,with the proposed DPS implementation,the fully-connected structure enjoys both satisfactory performance and low design complexity while the partially-connected one serves as an economic solution with low hardware complexity.展开更多
Abstract:Ubiquitous broadband Internet access is one of the major goals of the next generation of wireless communications.However,there are still some locations where this is diffcult to achieve.This is the case on mo...Abstract:Ubiquitous broadband Internet access is one of the major goals of the next generation of wireless communications.However,there are still some locations where this is diffcult to achieve.This is the case on moving vehicles and,particularly,on trains.Among the possible solutions to this problem,RoF(Radio-over-Fiber)architectures have been proposed as low-latency,cost-e ective candidates.Two elements are introduced to extend the RoF approach.First,the carrier frequency is raised into the W-band(75-110 GHz)to increase the available capacity.Second,a mechanical beam-steering solution based on a Stewart platform is adopted for the transmitter antenna to allow it to follow a moving receiver along a known path,thereby enhancing the coverage area.The performance of a system transmitting a 2.5 Gbit/s non-return-to-zero signal generated by photonic up-conversion over a wireless link is evaluated in terms of real-time BER(Bit Error Rate)measurements.The receiver is situated in di erent positions,and the orientation of the transmitter is changed accordingly.Values below the forward error correction limit for 7%overhead are obtained over a range of 60 cm around a center point situated 2 m away from the transmitter.展开更多
美国国防高级研究计划局(Defense Advanced Research Projects Agency,DARPA)采用E频段通信,设计、建立并验证了移动设备与机载平台间的自组织、可扩展的数据回传网络及稳健的、大容量骨干网络。对美军E频段通信的发展情况进行了梳理,...美国国防高级研究计划局(Defense Advanced Research Projects Agency,DARPA)采用E频段通信,设计、建立并验证了移动设备与机载平台间的自组织、可扩展的数据回传网络及稳健的、大容量骨干网络。对美军E频段通信的发展情况进行了梳理,针对“移动热点”与“100 Gb/s”两个典型项目从应用场景、性能指标、进度安排、关键技术等方面进行了分析,最后给出了对我国相关领域技术创新的启示与思考。展开更多
Unmanned aerial vehicle(UAV)has been widely used in many fields and is arousing global attention.As the resolution of the equipped sensors in the UAV becomes higher and the tasks become more complicated,much higher da...Unmanned aerial vehicle(UAV)has been widely used in many fields and is arousing global attention.As the resolution of the equipped sensors in the UAV becomes higher and the tasks become more complicated,much higher data rate and longer communication range are required in the foreseeable future.As the millimeter-wave(mm Wave)band can provide more abundant frequency resources than the microwave band,much higher achievable rate can be guaranteed to support UAV services such as video surveillance,hotspot coverage,and emergency communications,etc.The flexible mm Wave beamforming can be used to overcome the high path loss caused by the long propagation distance.In this paper,we study three typical application scenarios for mm Wave-UAV communications,namely communication terminal,access point,and backbone link.We present several key enabling techniques for UAV communications,including beam tracking,multi-beam forming,joint Tx/Rx beam alignment,and full-duplex relay techniques.We show the coupling relation between mm Wave beamforming and UAV positioning for mm Wave-UAV communications.Lastly,we summarize the challenges and research directions of mm Wave-UAV communications in detail.展开更多
为了解决毫米波无线通信中模数转换器(analog to digital converter,ADC)无法在接收信号上实现高倍的过采样以及多径影响所导致的定时跟踪问题,该文基于2倍过采样数据,根据相关波形,利用Farrow插值给出2种适用于多径信道的定时跟踪方案...为了解决毫米波无线通信中模数转换器(analog to digital converter,ADC)无法在接收信号上实现高倍的过采样以及多径影响所导致的定时跟踪问题,该文基于2倍过采样数据,根据相关波形,利用Farrow插值给出2种适用于多径信道的定时跟踪方案,分别在频域均衡之前和之后进行误差精补偿。仿真结果表明:在Rummler信道下,定时频偏为时钟频率的20×10^(-6)、误比特率为10^(-5)时,这2种方案的信噪比(signal-to-noise ratio,SNR)与无定时频偏时的只相差2.5dB左右,说明这2种方案在多径信道下具有良好的定时跟踪性能。展开更多
基金Project supported by the National Key R&D Program of China(No.2020YFB1806903)the National Natural Science Foundation of China(Nos.61922012,62001519,52042201,U1834210,and 61961130391)+2 种基金the State Key Laboratory of Rail Traffic Control and Safety,China(Nos.RCS2020ZT008,RCS2019ZZ007,and RCS2020ZT010)the Teaching Reform Project,China(No.134811522)the Fundamental Research Funds for the Central Universities,China(Nos.2020JBZD005 and I20JB0200030)。
文摘Orthogonal time frequency space(OTFS)modulation has been widely considered for high-mobility scenarios.Satellite-to-ground communications have recently received much attention as a typical high-mobility scenario and face great challenges due to the high Doppler shift.To enable reliable communications and high spectral efficiency in satellite mobile communications,we evaluate OTFS modulation performance for geostationary Earth orbit and low Earth orbit satellite-to-ground channels at sub-6-GHz and millimeter-wave bands in both lineof-sight and non-line-of-sight cases.The minimum mean squared error with successive detection(MMSE-SD)is used to improve the bit error rate performance.The adaptability of OTFS and the signal detection technologies in satellite-to-ground channels are analyzed.Simulation results confirm the feasibility of applying OTFS modulation to satellite-to-ground communications with high mobility.Because full diversity in the delay-Doppler domain can be explored,different terminal movement velocities do not have a significant impact on the performance of OTFS modulation,and OTFS modulation can achieve better performance compared with classical orthogonal frequency division multiplexing in satellite-to-ground channels.It is found that MMSE-SD can improve the performance of OTFS modulation compared with an MMSE equalizer.
基金supported in part by the National Key Research and Development Program of China(Grant No.2020YFB1805005)in part by the National Natural Science Foundation of China(Grant No.62031019)in part by the European Commission through the H2020-MSCA-ITN META WIRELESS Research Project under Grant 956256。
文摘Channel prediction is critical to address the channel aging issue in mobile scenarios.Existing channel prediction techniques are mainly designed for discrete channel prediction,which can only predict the future channel in a fixed time slot per frame,while the other intra-frame channels are usually recovered by interpolation.However,these approaches suffer from a serious interpolation loss,especially for mobile millimeter-wave communications.To solve this challenging problem,we propose a tensor neural ordinary differential equation(TN-ODE)based continuous-time channel prediction scheme to realize the direct prediction of intra-frame channels.Specifically,inspired by the recently developed continuous mapping model named neural ODE in the field of machine learning,we first utilize the neural ODE model to predict future continuous-time channels.To improve the channel prediction accuracy and reduce computational complexity,we then propose the TN-ODE scheme to learn the structural characteristics of the high-dimensional channel by low-dimensional learnable transform.Simulation results show that the proposed scheme is able to achieve higher intra-frame channel prediction accuracy than existing schemes.
文摘This paper presents an analysis and validation by advanced system simulation of compact and low-cost six-port transceivers for future wireless local area networks （WLANs） operating at millimeter-wave frequencies. To obtain realistic simulation results, a six-port model based on the measurement results of a fabricated V-band hybrid coupler, the core component, is used. A frequency-division multiplexing scheme is used by introducing four quadrature phase-shift keying （QPSK） channels in the wireless communication link. The data rate achieved is about 4 Gbit/s. The operating frequency is in the 60-64 GHz unlicensed band. Bit error rate （BER） results are presented, and a comparison is made between single-carrier and multicarrier architectures. The proposed wireless system can be considered an efficient candidate for millimeter-wave communication systems operating at quasi-optical data rates.
基金Project supported by the UK EPSRC(No.EP/N005597/1)the H2020-MSCA-RISE-2015(No.690750)+1 种基金the National Natural Science Foundation of China(No.61728101)the U.S.National Science Foundation(Nos.CNS-1702808 and ECCS-1647198)
文摘This paper provides a comprehensive survey of the impact of the emerging communication technique, non-orthogonal multiple access （NOMA）, on future wireless networks. Particularly, how the NOMA principle affects the design of the generation multiple access techniques is introduced first. Then the applications of NOMA to other advanced communication techniques, such as wireless caching, multiple-input multiple-output techniques, millimeter-wave communications, and cooperative relaying, are discussed. The impact of NOMA on communication systems beyond cellular networks is also illustrated, through the examples of digital TV, satellite communications, vehicular networks, and visible light communications. Finally, the study is concluded with a discussion of important research challenges and promising future directions in NOMA.
基金supported in part by the Hong Kong Research Grants Council under Grant No.16210216 and in part by the Alexander von Humboldt Foundation.
文摘Hybrid precoding is a cost-effective approach to support directional transmissions for millimeter-wave(mmWave)communications,but its precoder design is highly complicated.In this paper,we propose a new hybrid precoder implementation,namely the double phase shifter(DPS)implementation,which enables highly tractable hybrid precoder design.Efficient algorithms are then developed for two popular hybrid precoder structures,i.e.,the fully-and partially-connected structures.For the fully-connected one,the RF-only precoding and hybrid precoding problems are formulated as a least absolute shrinkage and selection operator problem and a low-rank matrix approximation problem,respectively.In this way,computationally efficient algorithms are provided to approach the performance of the fully digital one with a small number of radio frequency(RF)chains.On the other hand,the hybrid precoder design in the partially-connected structure is identified as an eigenvalue problem.To enhance the performance of this cost-effective structure,dynamic mapping from RF chains to antennas is further proposed,for which a greedy algorithm and a modified K-means algorithm are developed.Simulation results demonstrate the performance gains of the proposed hybrid precoding algorithms over existing ones.It shows that,with the proposed DPS implementation,the fully-connected structure enjoys both satisfactory performance and low design complexity while the partially-connected one serves as an economic solution with low hardware complexity.
基金This work is supported by the Marie Sk lodowska-Curie Innovative Training Network CELTA supported by the European Union's Horizon 2020 research and innovation programme(No.675683)the Innovative Training Network FiWiN5G project founded by the European Union's Horizon 2020 research and innovation programme(No.642355).
文摘Abstract:Ubiquitous broadband Internet access is one of the major goals of the next generation of wireless communications.However,there are still some locations where this is diffcult to achieve.This is the case on moving vehicles and,particularly,on trains.Among the possible solutions to this problem,RoF(Radio-over-Fiber)architectures have been proposed as low-latency,cost-e ective candidates.Two elements are introduced to extend the RoF approach.First,the carrier frequency is raised into the W-band(75-110 GHz)to increase the available capacity.Second,a mechanical beam-steering solution based on a Stewart platform is adopted for the transmitter antenna to allow it to follow a moving receiver along a known path,thereby enhancing the coverage area.The performance of a system transmitting a 2.5 Gbit/s non-return-to-zero signal generated by photonic up-conversion over a wireless link is evaluated in terms of real-time BER(Bit Error Rate)measurements.The receiver is situated in di erent positions,and the orientation of the transmitter is changed accordingly.Values below the forward error correction limit for 7%overhead are obtained over a range of 60 cm around a center point situated 2 m away from the transmitter.
文摘Unmanned aerial vehicle(UAV)has been widely used in many fields and is arousing global attention.As the resolution of the equipped sensors in the UAV becomes higher and the tasks become more complicated,much higher data rate and longer communication range are required in the foreseeable future.As the millimeter-wave(mm Wave)band can provide more abundant frequency resources than the microwave band,much higher achievable rate can be guaranteed to support UAV services such as video surveillance,hotspot coverage,and emergency communications,etc.The flexible mm Wave beamforming can be used to overcome the high path loss caused by the long propagation distance.In this paper,we study three typical application scenarios for mm Wave-UAV communications,namely communication terminal,access point,and backbone link.We present several key enabling techniques for UAV communications,including beam tracking,multi-beam forming,joint Tx/Rx beam alignment,and full-duplex relay techniques.We show the coupling relation between mm Wave beamforming and UAV positioning for mm Wave-UAV communications.Lastly,we summarize the challenges and research directions of mm Wave-UAV communications in detail.
文摘为了解决毫米波无线通信中模数转换器(analog to digital converter,ADC)无法在接收信号上实现高倍的过采样以及多径影响所导致的定时跟踪问题,该文基于2倍过采样数据,根据相关波形,利用Farrow插值给出2种适用于多径信道的定时跟踪方案,分别在频域均衡之前和之后进行误差精补偿。仿真结果表明:在Rummler信道下,定时频偏为时钟频率的20×10^(-6)、误比特率为10^(-5)时,这2种方案的信噪比(signal-to-noise ratio,SNR)与无定时频偏时的只相差2.5dB左右,说明这2种方案在多径信道下具有良好的定时跟踪性能。
