With the commercialization of the fifth generattion(5G)of wireless networks in 2019,the development of the next generation of wireless standards is currently under discussion.To cope with the target 1000x improvement ...With the commercialization of the fifth generattion(5G)of wireless networks in 2019,the development of the next generation of wireless standards is currently under discussion.To cope with the target 1000x improvement of system capacity,5G wireless standards have adopted massive MIMO as a key enabling physical layer technology to boost the spectral efficiency.展开更多
Severe doubly selective channel fading,or the time- and frequency-selective fading,prevailing in highspeed train(HST) communications,has been a critical issue that hinders the improvement of system efficiency and reli...Severe doubly selective channel fading,or the time- and frequency-selective fading,prevailing in highspeed train(HST) communications,has been a critical issue that hinders the improvement of system efficiency and reliability.In this paper,a relay-assisted HST communication system is considered,and a low-complexity but effective scheme is proposed to cooperatively exploit the joint multipath–Doppler diversity of both the direct link and the relay link and thus to mitigate the negative effect of channel fading and improve the system reliability.In particular,using a special precoding structure followed by two-dimensional Fourier transform,the transmit signal is generated which in effect parallelizes the doubly selective fading channel.As a result,in the transform domain,pointwise combining and equalization,which are of linear complexity,become feasible and diversity gain is obtained.The maximal diversity order is then analyzed under the amplify-and-forward relay settings,which reveals that by cooperative relaying the joint multipath–Doppler diversity of both links can be well exploited.Simulation results verified our analysis.展开更多
Owing to the inherent central information processing and resource management ability,the cloud radio access network(C-RAN)is a promising network structure for an intelligent and simplified sixth-generation(6G)wireless...Owing to the inherent central information processing and resource management ability,the cloud radio access network(C-RAN)is a promising network structure for an intelligent and simplified sixth-generation(6G)wireless network.Nevertheless,to further enhance the capacity and coverage,more radio remote heads(RRHs)as well as high-fidelity and low-latency fronthaul links are required,which may lead to high implementation cost.To address this issue,we propose to exploit the intelligent reflecting surface(IRS)as an alternative way to enhance the C-RAN,which is a low-cost and energy-efficient option.Specifically,we consider the uplink transmission where multi-antenna users communicate with the baseband unit(BBU)pool through multi-antenna RRHs and multiple IRSs are deployed between the users and RRHs.RRHs can conduct either point-to-point(P2P)compression or Wyner-Ziv coding to compress the received signals,which are then forwarded to the BBU pool through fronthaul links.We investigate the joint design and optimization of user transmit beamformers,IRS passive beamformers,and fronthaul compression noise covariance matrices to maximize the uplink sum rate subject to fronthaul capacity constraints under P2P compression and Wyner-Ziv coding.By exploiting the Arimoto-Blahut algorithm and semi-definite relaxation(SDR),we propose a successive convex approximation approach to solve non-convex problems,and two iterative algorithms corresponding to P2P compression and Wyner-Ziv coding are provided.Numerical results verify the performance gain brought about by deploying IRS in C-RAN and the superiority of the proposed joint design.展开更多
文摘With the commercialization of the fifth generattion(5G)of wireless networks in 2019,the development of the next generation of wireless standards is currently under discussion.To cope with the target 1000x improvement of system capacity,5G wireless standards have adopted massive MIMO as a key enabling physical layer technology to boost the spectral efficiency.
基金supported in part by the National Key Basic Research Program of China(2012CB316104)National Hi-Tech R&D Program(2014AA01A702)+1 种基金Zhejiang Provincial Natural Science Foundation of China(LR12F01002)the National Natural Science Foundation of China(61371094)
文摘Severe doubly selective channel fading,or the time- and frequency-selective fading,prevailing in highspeed train(HST) communications,has been a critical issue that hinders the improvement of system efficiency and reliability.In this paper,a relay-assisted HST communication system is considered,and a low-complexity but effective scheme is proposed to cooperatively exploit the joint multipath–Doppler diversity of both the direct link and the relay link and thus to mitigate the negative effect of channel fading and improve the system reliability.In particular,using a special precoding structure followed by two-dimensional Fourier transform,the transmit signal is generated which in effect parallelizes the doubly selective fading channel.As a result,in the transform domain,pointwise combining and equalization,which are of linear complexity,become feasible and diversity gain is obtained.The maximal diversity order is then analyzed under the amplify-and-forward relay settings,which reveals that by cooperative relaying the joint multipath–Doppler diversity of both links can be well exploited.Simulation results verified our analysis.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China(Nos.LY21F010008 and LD21F010001)the National Natural Science Foundation of China(No.62171412)the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University,China(No.2020D10)。
文摘Owing to the inherent central information processing and resource management ability,the cloud radio access network(C-RAN)is a promising network structure for an intelligent and simplified sixth-generation(6G)wireless network.Nevertheless,to further enhance the capacity and coverage,more radio remote heads(RRHs)as well as high-fidelity and low-latency fronthaul links are required,which may lead to high implementation cost.To address this issue,we propose to exploit the intelligent reflecting surface(IRS)as an alternative way to enhance the C-RAN,which is a low-cost and energy-efficient option.Specifically,we consider the uplink transmission where multi-antenna users communicate with the baseband unit(BBU)pool through multi-antenna RRHs and multiple IRSs are deployed between the users and RRHs.RRHs can conduct either point-to-point(P2P)compression or Wyner-Ziv coding to compress the received signals,which are then forwarded to the BBU pool through fronthaul links.We investigate the joint design and optimization of user transmit beamformers,IRS passive beamformers,and fronthaul compression noise covariance matrices to maximize the uplink sum rate subject to fronthaul capacity constraints under P2P compression and Wyner-Ziv coding.By exploiting the Arimoto-Blahut algorithm and semi-definite relaxation(SDR),we propose a successive convex approximation approach to solve non-convex problems,and two iterative algorithms corresponding to P2P compression and Wyner-Ziv coding are provided.Numerical results verify the performance gain brought about by deploying IRS in C-RAN and the superiority of the proposed joint design.
