The broadcast nature of air-to-ground line-of-sight (LoS) wireless channel imposes a great challenge in secure unmanned aerial vehicle (UAV) communications. To address this issue, this paper investigates UAV-ground communications from the physical-layer security perspective. Specifically, the investigated scenario includes a UAV serving as the base station (BS) that transmits confidential signals to a legitimate ground user, and there are multiple eavesdroppers on the ground with unknown position information. To further enhance the secrecy performance of the UAV-ground communications, an idle UAV can be employed to serve as a friendly jammer, which can transmit jamming signals to confuse the eavesdroppers. In our proposed strategy, the flying trajectory and the transmit power for both the UAVs are jointly optimized by maximizing the worst-case secrecy rate (WCSR) of the system. Considering the intractability of the formulated non-convex problem, we further provide a block coordinate descent-based iterative optimization method. Simulations verify that our proposed algorithm can significantly improve the average WCSR in comparison with the existing works.
Bibliographical noteFunding Information:
This work was supported in part by the National Science and Technology Major Program of the Ministry of Science and Technology under Grant 2018ZX03001031, in part by the Key Program of Beijing Municipal Natural Science Foundation under Grant L172030, in part by the Beijing Municipal Science & Technology Commission Project under Grant Z171100005217001, in part by the Key Project of State Key Laboratory of Networking and Switching Technology under Grant NST20170205, in part by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China under Grant 2012BAF14B01, in part by the National Key Research and Development Project under Grant 2017YFE0119300, and in part by the China Scholarship Council (CSC) under Grant 201806470003.
- UAV communications
- Worst case secrecy rate
- physical layer security