Abstract:

Facing the higher demands for communication and sensing in upcoming Dual-Function Radar Communication （DFRC） systems， a DFRC system model was proposed that combines multi-cluster Non-Orthogonal Multiple Access （NOMA） technology and Reconfigurable Intelligent Surface （RIS）. In the proposed model， the superimposed multi-cluster NOMA signals were utilized by the DFRC base stations to achieve target perception and the virtual line-of-sight links established by RIS reflection were used to enhance the communication performance of users in multi-cluster NOMA. Based on the proposed model， with the goal of maximizing weighted sum of the system sum rate and the sensing power， a non-convex objective function with multiple constraints and coupled variables was constructed. To solve this objective function， an optimization scheme for joint beamforming and power allocation was proposed. In the proposed scheme， firstly， the original optimization problem was decomposed into three subproblems. Subsequently， methods such as Successive Convex Approximation （SCA） and SemiDefinite Relaxation （SDR） were employed to transform the original non-convex optimization subproblems into convex optimization subproblems. Finally， the Alternating Optimization （AO） method was applied to solve the subproblems， thereby achieving joint beamforming （including active and passive beamforming） and intra-cluster power allocation coefficient optimization. Simulation results indicate that the proposed scheme has good performance of communication and sensing， and compared with the Orthogonal Multiple Access （OMA） scheme， it has the system sum rate improved by about 1 bit/（s·Hz） with high target perception performance， achieving a good compromise between communication performance and perception performance.

Key words: Integrated Sensing And Communication (ISAC), Non-Orthogonal Multiple Access (NOMA), Reconfigurable Intelligent Surface (RIS), Successive Convex Approximation (SCA), SemiDefinite Relaxation (SDR), Alternating Optimization (AO)

摘要：

面对未来双功能雷达通信（DFRC）系统对通信与感知性能的更高要求，结合非正交多址（NOMA）和可重构智能表面（RIS）技术，提出一种RIS辅助的融合多簇NOMA的DFRC系统模型。在所提模型中，DFRC基站利用叠加的多簇NOMA信号实现目标感知，并借助RIS反射建立的虚拟视距链路提升多簇NOMA中的用户通信性能。基于所提模型，以最大化系统和速率与感知功率的加权和为目标，构建受多条件约束且包含多变量耦合的非凸目标函数。为求解该目标函数，提出一种联合波束成形与功率分配的优化方案。在所提方案中，首先，将原优化问题分解为3个非凸优化子问题；其次，采用连续凸逼近（SCA）和半正定松弛（SDR）等方法将原非凸优化子问题转换为凸优化子问题；最后，采用交替优化（AO）方法对这些子问题进行迭代求解，从而实现联合波束成形（包括主动波束成形和被动波束成形）和簇内功率分配系数的优化。仿真实验结果表明，所提方案具有良好的通信性能与感知性能，与正交多址（OMA）方案相比，系统和速率的提升约为1 bit/（s·Hz），同时保持较高的目标感知性能，在通信性能和感知性能之间取得较好的折中。

关键词: 通感一体化, 非正交多址, 可重构智能表面, 连续凸逼近, 半正定松弛, 交替优化