## 4 Solutions
### Algorithm Structure
(2023) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Joint power and 3D trajectory optimization for UAV-enabled wireless powered communication networks with obstacles. _IEEE Trans. Commun._**2023**, _71_, 2364-2380. [CrossRef]
* [PERSON] et al. (2023) [PERSON]; [PERSON]; [PERSON]; [PERSON] A novel UAV path planning approach: Heuristic crossing search and rescue optimization algorithm. _Expert Syst. Appl._**2023**, _215_, 119243. [CrossRef]
* [PERSON] et al. (2023) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Robust computation offloading and trajectory optimization for multi-UAV-assisted mec: A multi-agent DRL approach. _IEEE Internet Things J._**2023**, _11_, 4775-4786. [CrossRef]
* [PERSON] et al. (2023) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Energy efficiency maximization for WPT-enabled UAV-assisted emergency communication with user mobility. _Phys. Commun._**2023**, _61_, 102200. [CrossRef]
* [PERSON] et al. (2023) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Energy-efficient multi-UAVs cooperative trajectory optimization for communication coverage: An MADRL approach. _Remote Sens._**2023**, _15_, 429. [CrossRef]
* [PERSON] et al. (2022) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Sustainable wireless services with UAV swarms tailored to renewable energy sources. _IEEE Trans. Smart Grid_**2022**, _14_, 3296-3308. [CrossRef]
* [PERSON] et al. (2018) [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON] Comprehensive energy consumption model for unmanned aerial vehicles, based on empirical studies of battery performance. _IEEE Access_**2018**, \(6\), 58383-58394. [CrossRef]
* [PERSON] et al. (2017) [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON] 3D placement of an unmanned aerial vehicle base station (UAV-BS) for energy-efficient maximal coverage. _IEEE Wirel. Commun. Lett._**2017**, \(6\), 434-437. [CrossRef]
* [PERSON] et al. (2019) [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON] A survey of air-to-ground propagation channel modeling for unmanned aerial vehicles. _IEEE Commun. Surv. Tutorials_**2019**, _21_, 2361-2391. [CrossRef]
* [PERSON] (1998) [PERSON]; [PERSON] [PERSON] Reinforcement learning: An introduction. _IEEE Trans. Neural Netw._**1998**, \(9\), 1054. [CrossRef]* [PERSON] et al. (2017) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Proximal policy optimization algorithms. _arXiv_**2017**, arXiv:1707.06347. * [PERSON] et al. (2021) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] The surprising effectiveness of PPO in cooperative, multi-agent games. _arXiv_**2021**, arXiv:2103.01955. * [PERSON] et al. (2021) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Leveraging UAVs for coverage in cell-free vehicular networks: A deep reinforcement learning approach. _IEEE Trans. Mob. Comput._**2021**, _20_, 2835-2847. [CrossRef]

**Disclaimer/Publisher's Note:** The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.