双智能反射面辅助的NOMA系统下行速率最大化研究  

Sum Rate Maximization Design for Double-IRS-aided Downlink NOMA System

作　　者：刘泽宇 王鸿 LIU Zeyu;WANG Hong(School of Communications and Information Engineering,Nanjing University of Posts and Telecommunications,Nanjing 210003,China)

机构地区：[1]南京邮电大学通信与信息工程学院,江苏南京210003

出　　处：《无线电工程》2024年第12期2865-2871,共7页Radio Engineering

基　　金：国家自然科学基金面上项目(62171237)。

摘　　要：由无源器件构成的智能反射面(Intelligent Reflecting Surface,IRS)是未来无线通信的关键技术之一,可以有效地提高频谱效率与降低硬件成本。非正交多址接入(Non-Orthogonal Multiple Access,NOMA)技术可有效地提高频谱效率,也被认为是未来6G的潜在关键技术。针对多IRS辅助的下行多天线NOMA系统开展速率最大化研究。通过求解总用户组合信道强度最大化问题,得到IRS反射面的初始相移矩阵,并据此得到用户的解码顺序;利用拉格朗日对偶变化(Lagrangian Dual Transforming,LDT)以及二次转化(Multidimensional Complex Quadratic Transform,MCQT)将原本复杂的问题简化为分式优化;利用交替优化方法设计最优的波束成形矢量与相移矩阵。在优化相移时,对每个IRS进行单独优化,将原问题转化为秩的形式进行求解;求解最优波束成形时,可通过二分法获得最优解。仿真结果表明,提出的设计方案显著提升了系统的和速率性能。Intelligent Reflecting Surface(IRS)with passive elements,which can effectively improve the spectral efficiency and reduce the hardware cost,is treated as one of the key technologies for future wireless communications.Besides,Non-Orthogonal Multiple Access(NOMA)technology can improve spectral efficiency effectively and is also viewed as the promising technique for the sixth generation mobile networks.The rate maximization problem of multi-IRS-assisted downlink multi-antenna NOMA system is studied.Firstly,the phase-shift matrix of IRS is obtained by solving the maximization problem of combined channel of total users,and then the decoding order of users is obtained accordingly.By using Lagrangian Dual Transformating(LDT)and Multidimensional Complex Quadratic Transform(MCQT),the original complicated problem is simplified to the fraction programming.The optimal beamforming vector and phase shift matrix are designed by alternating optimization method.Specifically,when optimizing the phase shifts,each IRS is optimized individually,and the original problem is converted into the form of rank.For achieving the optimal beamforming,the optimal solution can be obtained by dichotomy.Simulation results indicate that the proposed design can notably enhance the sum rate performance.

关 键 词：智能反射面 非正交多址接入 和速率 相位偏移 波束成形 

分 类 号：TN928[电子电信—通信与信息系统]