Sum Rate Maximization Design for Double-IRS-aided Downlink NOMA System
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.
万方数据
维普
