面向用户最大覆盖的多空中基站布局方法

以无人机为平台的空中基站(unmanned aerial vehicle base station, UAV-BS)部署灵活、通视较好，在应急通信场景中具有独特优势，但是UAV-BS位置对通信组网效能具有重要影响，如何优化UAV-BS部署位置，特别是多UAV-BS位置布局是一个关键问题。本文考虑对地面终端用户最大化的覆盖且尽可能降低基站发射功率，提出多UAV-BS定位模型。首先，基于通信区域视线(line-of-sight, LoS)和非视线(non-line-of-sight, NLoS)传输统计特性计算最大覆盖半径及相应UAV-BS定位的高度。在此基础上，将基站水平定位布局视为多圆覆盖问题，构建覆盖用户数最多的非线性约束优化模型，并在保持用户覆盖最大化的前提下，进一步优化各UAV-BS发射功率。然后，基于最小覆盖圆问题和遗传算法对定位模型进行求解，计算具有低阶多项式的时间复杂度。最后，通过仿真验证了所提方法的有效性，结果表明所提方法能够实现UAV-BS组网3D布局，并能最大化用户覆盖和降低基站功率。

Multi-UAV-BS layout approach for maximum coverage of users

Unmanned aerial vehicle base station (UAV-BS) is flexible in deployment and has a better air-to-ground transmission environment. It has unique advantages in emergency communication scenarios. However, the location of UAV-BSs has an important impact on the efficiency of communication networking. How to optimize the deployment location of UAV-BSs, especially the location of multi-UAV-BSs is a key issue. This paper considers the maximum coverage of ground terminals and reduces the base station transmission power as much as possible, and proposes a multi-UAV-BSs position model. First, the maximum coverage radius and the corresponding UAV-BS positioning altitude are calculated by the line-of-sight (LoS) and non-line-of-sight (NLoS) transmission statistics of the area. On this basis, the horizontal positioning layout of the base station is regarded as a multi-circle coverage problem, and a nonlinear constrained optimization model is proposed in order to cover the largest number of users. In addition, the transmission power of each UAV-BS is further optimized while maintaining the maximum coverage of users. Then a new algorithm based on the minimum covering circle problem and genetic algorithm is designed to solve the positioning model with low-order polynomial time complexity. Finally, the effectiveness of the proposed approach is verified by simulations, and the results show that the approach can realize 3D positioning in UAV-BSs networking, maximize user coverage and reduce base station power.