This paper investigates the performance of downlink non-orthogonal multiple access (NOMA) communication in unmanned aerial vehicle (UAV) networks enhanced by partitionable reconfigurable intelligent surfaces (RISs). We analyze three types of links between base station (BS) and UAVs: direct, RIS-only indirect, and composite links, under both Line-of-Sight (LoS) and Non-LoS (NLoS) propagation. The RIS-only indirect link and direct link are modeled using double Nakagami-m and Nakagami-m fading, respectively, while the composite link follows a combined fading channel model. Closed-form expressions for the cumulative distribution function (CDF) of the received signal-to-noise ratio (SNR) are derived for all links, enabling tractable outage probability analysis. Then, we formulate a fairness-efficiency bilevel optimization problem to minimize the maximum outage probability among UAVs while minimizing the total number of required RIS reflecting elements. Accordingly, an RIS-assisted UAV Outage Minimization (RUOM) algorithm is proposed, which fairly allocates the NOMA power coefficients while minimizing the total number of RIS reflecting elements required, subject to NOMA-defined constraints, RIS resource limitations, and maximum allowable outage threshold. Simulation results validate the analytical models and demonstrate that the proposed RUOM algorithm significantly improves fairness and efficiency in BS-UAV communication.

翻译：本文研究了由可分区重构智能表面增强的无人机网络中下行非正交多址通信的性能。我们分析了基站与无人机之间在视距与非视距传播条件下的三种链路类型：直接链路、仅RIS间接链路以及复合链路。其中，仅RIS间接链路与直接链路分别采用双Nakagami-m与Nakagami-m衰落模型，而复合链路遵循组合衰落信道模型。本文推导了所有链路接收信噪比累积分布函数的闭式表达式，从而实现了可处理的断连概率分析。随后，我们构建了一个公平性与效率的双层优化问题，旨在最小化无人机间的最大断连概率，同时最小化所需RIS反射单元的总数。据此，提出了一种RIS辅助的无人机断连最小化算法，该算法在满足非正交多址定义的约束条件、RIS资源限制及最大允许断连阈值的前提下，公平分配非正交多址功率系数，同时最小化所需RIS反射单元总数。仿真结果验证了分析模型，并表明所提出的RUOM算法显著提升了基站-无人机通信的公平性与效率。