A prevalent theory circulating among the non-scientific community is that the intensive deployment of base stations over the territory significantly increases the level of electromagnetic field (EMF) exposure and affects population health. To alleviate this concern, in this work, we propose a network architecture that introduces tethered unmanned aerial vehicles (TUAVs) carrying green antennas to minimize the EMF exposure while guaranteeing a high data rate for users. In particular, each TUAV can attach itself to one of the possible ground stations at the top of some buildings. The location of the TUAVs, transmit power of user equipment and association policy are optimized to minimize the EMF exposure. Unfortunately, the problem turns out to be mixed-integer non-linear programming (MINLP), which is non-deterministic polynomial-time (NP) hard. We propose an efficient low-complexity algorithm composed of three submodules. Firstly, we propose an algorithm based on the greedy principle to determine the optimal association matrix between the users and base stations. Then, we offer two approaches, a modified K-mean and shrink and realign (SR) process, to associate each TUAV with a ground station. Finally, we put forward two algorithms based on the golden search and SR process to adjust the TUAV's position within the hovering area over the building. After that, we consider the dual problem that maximizes the sum rate while keeping the exposure below a predefined value, such as the level enforced by the regulation. Next, we perform extensive simulations to show the effectiveness of the proposed TUAVs to reduce the exposure compared to various architectures. Eventually, we show that TUAVs with green antennas can effectively mitigate the EMF exposure by more than 20% compared to fixed green small cells while achieving a higher data rate.
翻译:在非科学界中流传的一个普遍理论是,基地站在领土上空的密集部署大大增加了电磁场接触量和影响人口健康。为了减轻这一关切,我们提议了一个网络结构,引入带有绿色天线的系内无人驾驶飞行器(TUAVs),以尽量减少电磁天线接触量,同时保证用户使用高数据率。特别是,每个TUAV可以附着在某些建筑物顶部的一个可能的地面站。TUAVs的位置、用户设备和关联政策的传输能力将最大限度地减少电磁场接触量。不幸的是,问题变成了非线性混合内编程(MINLP),这是非非非定式的多式天线天线天线式飞行器(TUAVs),我们建议一个高效的低兼容性算法,由三个子模块组成。首先,我们提议基于贪婪原则的算法,以确定用户和基站之间的最佳关联矩阵矩阵。然后,我们提出两种方法,一个经过修改的K-移动和调整的 EMMFLP(SR) 相对于下一个电路段,一个不固定水平,一个比我们固定天际电路路路段的系统,一个比,最后显示每个方向结构,一个我们用来的螺路路路段,一个比,一个比,一个我们用来显示。