下行RIS-NOMA系统交替优化波束形成方法

Alternate Optimization Beamforming Method for Downlink RIS-NOMA

为了最大化可重构智能反射面(RIS)辅助多输入单输出非正交多址(NOMA)通信系统中的加权和速率,提出了一种分式规划和连续凸逼近结合交替优化主被动波束形成的方法。首先,利用分式规划将加权和速率问题转化成分式问题并解耦信号和噪声功率;然后,分别利用拉格朗日乘子法和连续凸逼近交替优化主被动波束形成,从而将非凸最大化加权和速率问题分解成多个凸优化问题迭代求解;最后,获得主动波束形成的最优解和被动波束形成的次优解。仿真结果表明,所提方法有效地解决了RIS-NOMA通信系统中的波束形成问题,并且用户能够获得理想的速率提升。

In order to maximize the weighted sum rate of the multi-input single-output non-orthogonal multiple access(NOMA)communication system assisted by the reconfigurable intelligent surface(RIS),a method combining fractional programming and successive convex approximation is proposed to alternatively optimize active and passive beamforming.First,the weighted sum rate problem is transformed into a fractional problem by fractional programming and the signal and noise power are decoupled.Then,the active and passive beamforming are alternately optimized by the Lagrange multiplier method and successive convex approximation,respectively.Thus,the nonconvex problem of maximizing the weighted sum rate is decomposed into multiple convex optimization problems.Finally,the optimal solution of active beamforming and the suboptimal solution of passive beamforming are obtained.The simulation results show that the proposed method can effectively solve the beamforming problem in the RIS-NOMA communication system and users can obtain an ideal rate increase.