It is assumed that reconfigurable intelligent surface(RIS)is a key technology to enable the potential of mmWave communications.The passivity of the RIS makes channel estimation difficult because the channel can only b...It is assumed that reconfigurable intelligent surface(RIS)is a key technology to enable the potential of mmWave communications.The passivity of the RIS makes channel estimation difficult because the channel can only be measured at the transceiver and not at the RIS.In this paper,we propose a novel separate channel estimator via exploiting the cascaded sparsity in the continuously valued angular domain of the cascaded channel for the RIS-enabled millimeter-wave/Tera-Hz systems,i.e.,the two-stage estimation method where the cascaded channel is separated into the base station(BS)-RIS and the RIS-user(UE)ones.Specifically,we first reveal the cascaded sparsity,i.e.,the sparsity exists in the hybrid angular domains of BS-RIS and the RIS-UEs separated channels,to construct the specific sparsity structure for RIS enabled multi-user systems.Then,we formulate the channel estimation problem using atomic norm minimization(ANM)to enhance the proposed sparsity structure in the continuous angular domains,where a low-complexity channel estimator via Alternating Direction Method of Multipliers(ADMM)is proposed.Simulation findings demonstrate that the proposed channel estimator outperforms the current state-of-the-arts in terms of performance.展开更多
Scholars are expected to continue enhancing the depth and breadth of theoretical research on reconfigurable intelligent surface(RIS)to provide a higher theoretical limit for RIS engineering applications.Notably,signif...Scholars are expected to continue enhancing the depth and breadth of theoretical research on reconfigurable intelligent surface(RIS)to provide a higher theoretical limit for RIS engineering applications.Notably,significant advancements have been achieved through both academic research breakthroughs and the promotion of engineering applications and industrialization.We provide an overview of RIS engineering applications,focusing primarily on their typical features,classifications,and deployment scenarios.Furthermore,we systematically and comprehensively analyze the challenges faced by RIS and propose potential solutions including addressing the beamforming issues through cascade channel decoupling,tackling the effects and resolutions of regulatory constraints on RIS,exploring the network-controlled mode for RIS system architecture,examining integrated channel regulation and information modulation,and investigating the use of the true time delay(TTD)mechanism for RIS.In addition,two key technical points,RIS-assisted non-orthogonal multiple access(NOMA)and RIS-based transmitter,are reviewed from the perspective of completeness.Finally,we discuss future trends and challenges in this field.展开更多
文摘It is assumed that reconfigurable intelligent surface(RIS)is a key technology to enable the potential of mmWave communications.The passivity of the RIS makes channel estimation difficult because the channel can only be measured at the transceiver and not at the RIS.In this paper,we propose a novel separate channel estimator via exploiting the cascaded sparsity in the continuously valued angular domain of the cascaded channel for the RIS-enabled millimeter-wave/Tera-Hz systems,i.e.,the two-stage estimation method where the cascaded channel is separated into the base station(BS)-RIS and the RIS-user(UE)ones.Specifically,we first reveal the cascaded sparsity,i.e.,the sparsity exists in the hybrid angular domains of BS-RIS and the RIS-UEs separated channels,to construct the specific sparsity structure for RIS enabled multi-user systems.Then,we formulate the channel estimation problem using atomic norm minimization(ANM)to enhance the proposed sparsity structure in the continuous angular domains,where a low-complexity channel estimator via Alternating Direction Method of Multipliers(ADMM)is proposed.Simulation findings demonstrate that the proposed channel estimator outperforms the current state-of-the-arts in terms of performance.
基金Project supported by the National Key Research and Development Program of China(No.2020YFB1807600)。
文摘Scholars are expected to continue enhancing the depth and breadth of theoretical research on reconfigurable intelligent surface(RIS)to provide a higher theoretical limit for RIS engineering applications.Notably,significant advancements have been achieved through both academic research breakthroughs and the promotion of engineering applications and industrialization.We provide an overview of RIS engineering applications,focusing primarily on their typical features,classifications,and deployment scenarios.Furthermore,we systematically and comprehensively analyze the challenges faced by RIS and propose potential solutions including addressing the beamforming issues through cascade channel decoupling,tackling the effects and resolutions of regulatory constraints on RIS,exploring the network-controlled mode for RIS system architecture,examining integrated channel regulation and information modulation,and investigating the use of the true time delay(TTD)mechanism for RIS.In addition,two key technical points,RIS-assisted non-orthogonal multiple access(NOMA)and RIS-based transmitter,are reviewed from the perspective of completeness.Finally,we discuss future trends and challenges in this field.
