Hangmei Rao Sa Xiao Shihao Yan Jianquan Wang 0002 Wanbin Tang Optimal Geometric Solutions to UAV-Enabled Covert Communications in Line-of-Sight Scenarios. 10633-10647 2022 21 IEEE Trans. Wirel. Commun. 12 https://doi.org/10.1109/TWC.2022.3185492 db/journals/twc/twc21.html#RaoXYWT22