In this paper, we investigate the application of the non-orthogonal multiple access (NOMA) technique into the unmanned aerial vehicle (UAV) aided relay networks. Specifically, we first incorporate the NOMA protocol with the decode-and-forward (DF) relay protocol to enhance the performance of the cell edge users in a macrocell network. Theoretical analysis indicates that the NOMA-DF-relay protocol outperforms the conventional orthogonal multiple access (OMA) based DF-relay protocol in terms of data rate. To fully exploit the advantages of the proposed protocol, we formulate a joint UAV height optimization, channel allocation, and power allocation problem with the objective to maximize the total data rate of the cell edge users under the coverage of the UAV. For solving the formulated problem effectively, we first analyze its property and employ the golden section method to propose a general framework to obtain the optimal height of the UAV. Then, we design a low-complexity iterative algorithm to solve the joint channel-and-power allocation problem based on the matching theory and the Lagrangian dual decomposition technique. Finally, simulation results demonstrate that the NOMA-DF-relay protocol is superior to the OMA-DF-relay protocol even when the system parameters are not optimized, and the proposed algorithms can further significantly improve the network performance in comparison with the other schemes.

中文翻译：

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NOMA增强型无人机辅助中继网络的高度优化和资源分配

在本文中，我们研究了非正交多路访问（NOMA）技术在无人机（UAV）辅助中继网络中的应用。具体来说，我们首先将NOMA协议与解码转发（DF）中继协议相结合，以增强宏小区网络中小区边缘用户的性能。理论分析表明，在数据速率方面，NOMA-DF中继协议优于传统的基于正交多址（OMA）的DF中继协议。为了充分利用建议协议的优势，我们制定了联合无人机高度优化，信道分配和功率分配问题，目的是在无人机覆盖范围内最大化小区边缘用户的总数据速率。为了有效解决提出的问题，我们首先分析其性质，并采用黄金分割法提出一个通用框架，以获取无人机的最佳高度。然后，基于匹配理论和拉格朗日对偶分解技术，设计了一种低复杂度的迭代算法来解决联合信道和功率分配问题。最后，仿真结果表明，即使不优化系统参数，NOMA-DF-relay协议也优于OMA-DF-relay协议，并且与其他方案相比，该算法可以进一步显着提高网络性能。我们基于匹配理论和拉格朗日对偶分解技术，设计了一种低复杂度的迭代算法来解决联合信道和功率分配问题。最后，仿真结果表明，即使不优化系统参数，NOMA-DF-relay协议也优于OMA-DF-relay协议，并且与其他方案相比，该算法可以进一步显着提高网络性能。我们基于匹配理论和拉格朗日对偶分解技术，设计了一种低复杂度的迭代算法来解决联合信道和功率分配问题。最后，仿真结果表明，即使不优化系统参数，NOMA-DF-relay协议也优于OMA-DF-relay协议，并且与其他方案相比，该算法可以进一步显着提高网络性能。