This work focuses on maximizing the minimum user’s security energy efficiency(SEE)in an unmanned aerial vehicle-mounted reconfigurable intelligent surface(UAV-RIS)enhanced short-packet communication(SPC)system.The ba...This work focuses on maximizing the minimum user’s security energy efficiency(SEE)in an unmanned aerial vehicle-mounted reconfigurable intelligent surface(UAV-RIS)enhanced short-packet communication(SPC)system.The base station(BS)provides short packet services to ground users using the non-orthogonal multiple access(NOMA)protocol through UAV-RIS,while preventing eavesdropper attacks.To optimize SEE,a joint optimization is performed concerning power allocation,UAV position,decoding order,and RIS phase shifts.An iterative algorithm based on block coordinate descent is proposed for mixed-integer non-convex SEE optimization problem.The original problem is decomposed into three sub-problems,solved alternately using successive convex approximation(SCA),quadratic transformation,penalty function,and semi-definite programming(SDP).Simulation results demonstrate the performance of the UAV-RIS-enhanced short-packet system under different parameters and verify the algorithm’s convergence.Compared to benchmark schemes such as orthogonal multiple access,long packet communication,and sum SEE,the proposed UAV-RIS-enhanced short-packet scheme achieves the higher minimum user’s SEE.展开更多
This paper investigates the reconfigurable intelligent surface(RIS)-aided MIMO covert communications in high-speed railway(HSR)scenario.In the scenario,RIS controls the phases of reflection elements dynamically to sen...This paper investigates the reconfigurable intelligent surface(RIS)-aided MIMO covert communications in high-speed railway(HSR)scenario.In the scenario,RIS controls the phases of reflection elements dynamically to send the signal in the desired direction,which facilitates the covert communication between base station(BS)and train mobile relay(MR)in the existence of a watchful warden(Willie).To protect the desired transmission,it is assumed that MR sends out jamming signals with a varying power to confuse the Willie.Considering the Doppler spread caused by the time-varying wireless channel,the joint optimization problem of the BS beamforming matrix,MR beamforming matrix,and the RIS phase shifts is established to maximize the covert throughput.An alternating optimization(AO)method for handling non convex problems is proposed based on coupling effects and the constraints of constant modulus,and a semidefinite relaxation method is provided.Finally,we achieve the optimal solutions of the multi-objective optimization problem by interior-point method.The simulation results demonstrate that the proposed algorithm exhibits the superior robustness and covert performances in high-speed railway scenarios.展开更多
A Reconfigurable Intelligent Surface(RIS)can relay signals from the transmitter to the receiver.In this regard,RISs operate similarly to traditional relays.We design a Multiple-Input-Multiple-Output(MIMO)system with a...A Reconfigurable Intelligent Surface(RIS)can relay signals from the transmitter to the receiver.In this regard,RISs operate similarly to traditional relays.We design a Multiple-Input-Multiple-Output(MIMO)system with a hybrid network of RIS and Half-Duplex(HD)Amplify-and-Forward(AF)relay.We model the system’s signal propagation and propose a new algorithm to get the system’s Achievable Rate(AR)value.We complete simulations to evaluate the performance of the RIS and HD-AF relay hybrid network system compared to the system assisted by either the RIS or HD-AF relay.The simulations indicate that many factors can considerably influence the system performance.Selecting an optimal placement for the RIS and relay can result in the best performance for the RIS and HD-AF relay hybrid network system in situations where the direct link between the receiver and transmitter is absent.展开更多
New communication systems require high spectral and energy efficiencies to meet the growing demand for services in future networks.In this paper,an efficient multiple parallel reconfigurable intelligent surfaces(RIS)-...New communication systems require high spectral and energy efficiencies to meet the growing demand for services in future networks.In this paper,an efficient multiple parallel reconfigurable intelligent surfaces(RIS)-assisted multiuser(MU) multiple input-multiple output(MIMO) double quadrature spatial modulation(DQSM) downlink transmission system is presented.In the transmitter,the proposed N-RIS-MU-MIMO-DQSM system uses a modified block diagonalization technique and a genetic algorithm(GA) to jointly design the precoding signals required at the base station(BS) and the optimal phase changes required at multiple RISs.A reduced detection complexity and improved bit error rate(BER) performance are achieved by incorporating spatial modulation.The proposed system is compared under the same conditions and parameters with two reference systems,considering blind and optimized RISs approaches over correlated Rayleigh fading channels.Results show that compared with a similar system that does not use RISs,the proposed system has up to30 dB gain in BER performance.Compared with a similar system based on conventional quadrature amplitude modulation(QAM),the proposed system has gains of up to 2-3 dB in BER performance and up to 55.8% lower detection complexity for the analyzed cases.展开更多
基金co-supported by the National Natural Science Foundation of China(Nos.U23A20279,62271094)the National Key R&D Program of China(No.SQ2023YFB2500024)+2 种基金the Science Foundation for Youths of Natural Science Foundation of Sichuan Provincial,China(No.2022NSFSC0936)the China Postdoctoral Science Foundation(No.2022M720666)the Open Fund of Key Laboratory of Big Data Intelligent Computing,Chongqing University of Posts and Telecommunications,China(No.BDIC-2023-B-002).
文摘This work focuses on maximizing the minimum user’s security energy efficiency(SEE)in an unmanned aerial vehicle-mounted reconfigurable intelligent surface(UAV-RIS)enhanced short-packet communication(SPC)system.The base station(BS)provides short packet services to ground users using the non-orthogonal multiple access(NOMA)protocol through UAV-RIS,while preventing eavesdropper attacks.To optimize SEE,a joint optimization is performed concerning power allocation,UAV position,decoding order,and RIS phase shifts.An iterative algorithm based on block coordinate descent is proposed for mixed-integer non-convex SEE optimization problem.The original problem is decomposed into three sub-problems,solved alternately using successive convex approximation(SCA),quadratic transformation,penalty function,and semi-definite programming(SDP).Simulation results demonstrate the performance of the UAV-RIS-enhanced short-packet system under different parameters and verify the algorithm’s convergence.Compared to benchmark schemes such as orthogonal multiple access,long packet communication,and sum SEE,the proposed UAV-RIS-enhanced short-packet scheme achieves the higher minimum user’s SEE.
基金supported by the National Natural Science Foundation of China(62161016)the Key Research and Development Project of Lanzhou Jiaotong University(ZDYF2304)the Beijing Engineering Research Center of High-Speed Railway Broadband Mobile Communications(BHRC-2022-1),Beijing Jiaotong University.
文摘This paper investigates the reconfigurable intelligent surface(RIS)-aided MIMO covert communications in high-speed railway(HSR)scenario.In the scenario,RIS controls the phases of reflection elements dynamically to send the signal in the desired direction,which facilitates the covert communication between base station(BS)and train mobile relay(MR)in the existence of a watchful warden(Willie).To protect the desired transmission,it is assumed that MR sends out jamming signals with a varying power to confuse the Willie.Considering the Doppler spread caused by the time-varying wireless channel,the joint optimization problem of the BS beamforming matrix,MR beamforming matrix,and the RIS phase shifts is established to maximize the covert throughput.An alternating optimization(AO)method for handling non convex problems is proposed based on coupling effects and the constraints of constant modulus,and a semidefinite relaxation method is provided.Finally,we achieve the optimal solutions of the multi-objective optimization problem by interior-point method.The simulation results demonstrate that the proposed algorithm exhibits the superior robustness and covert performances in high-speed railway scenarios.
文摘A Reconfigurable Intelligent Surface(RIS)can relay signals from the transmitter to the receiver.In this regard,RISs operate similarly to traditional relays.We design a Multiple-Input-Multiple-Output(MIMO)system with a hybrid network of RIS and Half-Duplex(HD)Amplify-and-Forward(AF)relay.We model the system’s signal propagation and propose a new algorithm to get the system’s Achievable Rate(AR)value.We complete simulations to evaluate the performance of the RIS and HD-AF relay hybrid network system compared to the system assisted by either the RIS or HD-AF relay.The simulations indicate that many factors can considerably influence the system performance.Selecting an optimal placement for the RIS and relay can result in the best performance for the RIS and HD-AF relay hybrid network system in situations where the direct link between the receiver and transmitter is absent.
文摘New communication systems require high spectral and energy efficiencies to meet the growing demand for services in future networks.In this paper,an efficient multiple parallel reconfigurable intelligent surfaces(RIS)-assisted multiuser(MU) multiple input-multiple output(MIMO) double quadrature spatial modulation(DQSM) downlink transmission system is presented.In the transmitter,the proposed N-RIS-MU-MIMO-DQSM system uses a modified block diagonalization technique and a genetic algorithm(GA) to jointly design the precoding signals required at the base station(BS) and the optimal phase changes required at multiple RISs.A reduced detection complexity and improved bit error rate(BER) performance are achieved by incorporating spatial modulation.The proposed system is compared under the same conditions and parameters with two reference systems,considering blind and optimized RISs approaches over correlated Rayleigh fading channels.Results show that compared with a similar system that does not use RISs,the proposed system has up to30 dB gain in BER performance.Compared with a similar system based on conventional quadrature amplitude modulation(QAM),the proposed system has gains of up to 2-3 dB in BER performance and up to 55.8% lower detection complexity for the analyzed cases.
