公平性驱动的RSMA-SDMA预编码设计

Design of fairness-driven RSMA-SDMA precoding

针对在发射功率受限时系统最小用户速率与系统公平性问题,提出了一种联合速率分拆多址接入(RSMA)和空分多址接入(SDMA)的用户接入方式选择传输策略,并建模了最大化系统公平性预编码设计问题。为解决建模所形成的离散非凸优化问题,将其分解为求解外层用户接入方式选择与内层最优预编码设计2个非凸子问题。针对预编码设计优化,利用二次变换的多比率分式规划将预编码设计问题转化为双层轮换问题,对用户接入方式逐次优化,得到了外层用户接入方式选择最优解的闭式表达式;以凸优化解决内层预编码设计问题,逐次优化用户接入方式选择传输策略,提出基于分式优化的预编码设计算法,利用二次变换的多比率分式规划设计最优预编码向量,求解功率受限下最大化最小用户速率。仿真结果表明,相比于RSMA、SDMA等传输策略,公平性驱动的RSMA-SDMA预编码设计提升了系统最小用户速率,保障了系统公平性。

In view of the minimum user rate and system fairness when the transmit power was limited,a user access mode selection transmission strategy by joint rate-splitting multiple access(RSMA) and space division multiple access(SDMA) was proposed.The precoding design problem of maximizing system fairness was modeled.In order to solve the discrete non-convex optimization problem formed,it was decomposed into two non-convex sub-problems,such as the user access mode selection and the inner optimal precoding design.For the precoding design,a quadratic transform of multidimensional and complex FP was used to transform the precoding design into double rotation,and the closed-form expression of the optimal solution for the outer user access mode selection was obtained.Convex optimization was used to solve the inner precoding design problem,and successively optimize the user access mode selection.An algorithm based on fractional optimization was proposed for the problem,and the optimal precoding vector was designed using the quadratic transform of multidimensional and complex FP to maximize the minimum user rate under power constraints.The simulation results prove that compared with RSMA,SDMA and other transmission strategies,the fairness-driven RSMA-SDMA precoding design improves the minimum user rate of the system and guarantees the system fairness.