同时透射与反射可重构智能表面(simultaneously transmitting and reflecting reconfigurable intelligent surface,STAR-RIS)具有同时透射与反射的特性,能够将传统RIS(conventional RIS,CRIS)的通信能力从半空间扩展至全空间.针对STAR-RIS辅助下的多用户多输入单输出(multiple-input single-output,MISO)通信系统,提出了一种基于时间切换(time switch,TS)模式的波束成形算法,以实现发射功率最小化.该算法首先通过最大比传输(maximum ratio transmission,MRT)得到基站初始发射波束,然后利用TS时隙正交性和信道增益最大化(channel gain maximum,CGM)将非凸优化问题解耦为恒模非凸问题和半正定规划(semi-definite programming,SDP)问题,最后利用流形优化与内点法联合求解.仿真结果表明,STAR-RIS相比CRIS可以有效降低发射功率;所提算法在相同信干噪比下,比主流算法具有更低的发射功率;TS模式在低信干噪比下相较于能量分裂(energy split,ES)模式具有更低的发射功率.
STAR-RIS assisted multi-user wireless system beamforming design in TS mode
Simultaneously transmitting and reflecting reconfigurable intelligent surface(STAR-RIS)has the capabil-ity of simultaneous transmission and reflection,extending the communication capacity of conventional RIS(CRIS)from half-space to full-space.For the multi-user multiple-input single-output(MISO)communication system assisted by STAR-RIS,a beamforming algorithm based on time switch(TS)mode was proposed to minimize transmission power.Firstly,maximum ratio transmission(MRT)was used to get the initial BS transmitting beamforming.Sec-ondly,TS slot orthogonality and channel gain maximum(CGM)were used to decouple the non-convex problem into the constant mode non-convex problem and the semi-definite programming(SDP)problem.Finally,manifold optimi-zation and interior point method were used to jointly solve these problems.The simulation results show that,STAR-RIS can effectively reduce the transmission power compared with conventional RIS.Under the same SINR(signal-to-noise ratio).The proposed algorithm has lower transmitting power than the mainstream algorithm.TS mode has lower transmitting power than energy splitting(ES)mode at low SINR.
STAR-RISmulti-userbeamformingminimize transmission power
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