Energy-Efficient and Secure Air-to-Ground Communication With Jittering UAV

Unmanned Aerial Vehicle (UAV)-enabled communication platform is recognized as a promising way for secure transmission in the air-to-air and air-to-ground (A2G) networks. However, the jitter feature of UAV platform due to the absence of fixed infrastructure, the inherent randomness of airflow, and the body vibration introduces non-negligible impact on establishing robust and energy-efficient secure communication links. In this paper, we investigate energy-saving and secure transmission in a downlink A2G wiretap system considering the impact of UAV jitter. Particularly, in order to minimize the total transmission power of UAV-mounted base station, a joint beamforming optimization of confidential signal and artificial noise signal is formulated with the constraints for secrecy performance of the worst scenario. Specifically, considering the impact of UAV jittering on the antenna array response, the worst scenario indicates the A2G wiretap system with the minimum legitimate data rate and the maximum eavesdropping data rate. The non-convex problem is then reformulated with linear approximation for the channel variations and linear matrix inequality alternation for the constraints. Then, semidefinite programming relaxation is adopted to obtain the optimal solutions for the reformulated problem. Furthermore, the problem and solution are extended to the multiuser downlink wiretap system. Finally, numerical results are provided to demonstrate the impact of key system parameters on power saving under the secure transmission constraints and the UAV jitter.