针对非正交多址接入(non-orthogonal multiple access,NOMA)系统在无线环境下传输速率较低的问题,利用智能反射面(intelligent reflecting surface,IRS)可以改变入射信号相移的特性,提出一种基于IRS辅助上行NOMA和速率最大化算法.首先,在满足每个用户功率、每个用户最小速率、IRS相位偏移的约束条件下,构建一个联合用户功率、IRS相移多变量优化模型;然后,通过问题公式的等效简化将原非凸问题转换为2 个容易处理的子问题;最后,通过交替方向乘子法(alternating direction method of multipliers,ADMM)、引入松弛变量等方法对子问题进行求解.仿真结果表明,相较于逐次凸逼近法(successive convex approxi-mation,SCA)所提出的算法平均提升了系统 0.4 bit/(s·Hz)的和速率,证明了基于ADMM的算法有效提高系统的和速率.
To address the problem of low transmission rate of non-orthogonal multiple access(NOMA)system in wireless environment,we propose an IRS-assisted uplink NOMA and rate maximization algorithm based on the property that intelligent reflecting surface(IRS)can change the phase shift of the incident signal.First,a joint user power and IRS phase shift multivariate optimization model is constructed under the constraints of per-user power,per-user minimum rate,and IRS phase shift.Then,the original nonconvex problem is converted into two easily handled subproblems by equivalent simplification of the problem formulation.Finally,the subproblems are solved by the alternating direction method of multipliers(ADMM)and the introduction of relaxation variables.The simulation results show that the proposed algorithm improves the sum rate of the system by 0.4 bit/(s·Hz)on average compared with the successive convex approximation(SCA),which proves that the ADMM-based algorithm is effective in improving the sum rate of the system.
维普
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