智能反射面辅助的非正交多址系统协作多点传输方案研究

Cooperative transmission design for IRS-aided NOMA systems

智能反射面(Intelligent Reflection Surface,IRS)和非正交多址接入(Non-Orthogonal Multiple Access,NOMA)被认为是6G的关键创新型技术,将两者融合可以大幅提高通信系统的频谱效率与能量效率。文中针对IRS辅助的双小区协作多点与非正交多址接入融合系统展开研究,具体地,将IRS部署于两小区中间的小区边缘附近,用来提升边缘用户的信号质量。在考虑用户服务质量(Quality of Service,QoS)与基站发射功率限制的条件下,建立了最大化小区边缘用户可达速率的优化问题。由于该问题是非凸的,很难直接求解,将此问题分解为两个子优化问题,采用交替优化算法进行求解。具体地,采用二分法解决功率分配系数优化问题;采用均方误差(Mean-Square Error,MSE)方法将优化问题转化为等效形式,再通过最大最小化(Majorization-Minimization,MM)算法进一步解决相移优化问题。仿真结果显示,所提出的解决方案使得边缘用户可达速率明显高于其他基准方案。

Intelligent reflecting surface(IRS)and non-orthogonal multiple access(NOMA)are two of innovative and key technologies for 6G networks.The combination of IRS and NOMA is capable of boosting the spectral efficiency and the energy efficiency significantly.In this paper,we focus on the transmission scheme for IRS-assisted cooperative multi-point and NOMA systems.Specifically,the IRS is deployed at the edge of two cells to improve the signal quality of the cell-edge users.Given the constraints of each users quality of service(QoS)and the base station transmission power budget,a problem of maximizing the minimum achievable rate of cell-edge users is formulated.In order to solve this problem,the original problem is decomposed into two sub-problems,which is solved by the alternative optimization method.Particalarly,the power coefficient optimization problem is solved by the bisection method.Besides,the optimization problem is transformed into an equivalent one by a mean square error(MSE)based method,and then the phase shift optimization problem is solved by the majorization minimization(MM)algorithm.The simulation results show that the achievable rate of cell-edge users for the proposed solution is significantly higher than that of other benchmark schemes.