摘要
Reconfigurable intelligent surfaces(RISs)have the capability to change the wireless environment smartly Considering the attenuation of subchannels and crowding users involved in the wideband system,we introduce RISs into the multi-user multi-input single-output(MU-MISO)system with orthogonal frequency division multiplexing(OFDM)for performance enhancement.Maximizing the minimum rate of dense users in an MU-MISO-OFDM system assisted by RIS with an approximate practical model is formulated as the joint optimization problem involving subcarrier allocation,transmit precoding(TPC)matrices at the base station,and RIS passive beamforming.A coalition-game subcarrier allocation(CSA)algorithm is proposed to solve space–frequency resource allocation on subcarriers,which reforms the interference topology among dense users.Fractional programming and convex optimization method are used to optimize the TPC matrices and the RIS passive beamforming,which improves the spectral efficiency synthetically across all subchannels in the wideband system.Simulation results indicate that the CSA algorithm provides a significant gain for dense users.Besides,the proposed joint optimization method shows the considerable advantage of the RISs in the MU-MISO-OFDM system.
基金
Project supported by the Graduate Research and Innovation Foundation of Chongqing,China(No.CYB23050)
the National Natural Science Foundation of China(Nos.62271092,62001074)
the Fundamental Research Funds for the Central Universities,China(No.2023CDJXY-037)
the China Postdoctoral Science Foundation(No.2022M710534)
the Natural Science Foundation of Chongqing,China(Nos.CSTB2023NSCQMSX0933,CSTB2022NSCQMSX0327)
the Open Fund of the Shaanxi Key Laboratory of Information Communication Network and Security,China(No.ICNS202201)
the Opening Project of the Guangxi Wireless Broadband Communication and Signal Processing Key Laboratory,China(No.GXKL06230206)。
