Research On Energy-efficient Secure Transmission Technology Of UAV Communication Systems With User Fairness

Owing to high probability line-of-sight link,strong mobility and flexible deployment,unmanned aerial vehicle(UAV)communication systems can effectively enhance communication network coverage and wireless channel capacity,compared to traditional terrestrial communication systems.However,due to the broadcast nature of wireless channels and the limited on-board energy of UAVs,the information security transmission and energy consumption problems become the bottleneck issues that need to be solved urgently in the UAV communication system.In addition,due to factors such as user location and communication environment,the wireless channel quality of different users is significantly different,resulting in the wireless communication system preferring rich users with better wireless channel quality and ignoring poor users with worse wireless channel quality,which cannot achieve the fairness of the entire communication network.Therefore,in this paper,based on fully considering the fairness of user communication,from the perspective of the balance between wireless communication security and energy efficiency,an energy-efficient and secure transmission method of UAV communication system based on user fairness is studied.The details of the research are as follows:(1)For the downlink multi-user UAV communication scenario,taking into account the secrecy energy efficiency fairness among users,the minimum user’s secrecy energy efficiency is maximized by jointly optimizing resource allocation and the UAV trajectory.Firstly,the signal model of the system is derived,the multi-user secrecy capacity model and the UAV flight power consumption model based on the waypoint discretization method are constructed,and the UAV communication system performance indicator based on the secrecy energy efficiency fairness among users is proposed.Then,a user-oriented secrecy energy efficiency maximization problem is formulated to maximize the minimum user’s secrecy energy efficiency subject to the UAV motion constraints and resource budgets.Due to the difficulty in solving this problem that arises from the fractional structure of objective function and the coupling characteristic of optimization variables,the original problem is transform into a convex one by exploiting the successive convex approximation(SCA),and an iterative algorithm with low complexity is proposed to enhance the computational accuracy and efficiency.Simulation results show that the proposed scheme substantially enhances secrecy energy efficiency fairness of users.(2)For the uplink multi-user UAV communication scenario with imperfect location information of the eavesdropper,from the user fairness perspective,an energy-efficient robust secure transmission scheme of full-duplex UAV uplink communication systems based on user fairness is proposed.Firstly,the signal model of the system is derived,the multi-user secrecy capacity model and the UAV flight power consumption model based on the time division multiple access protocol are constructed,and the UAV communication system performance indicator based on the secrecy energy efficiency fairness among users is proposed.Then,the robust user-oriented secrecy energy efficiency maximization problem is formulated under the probabilistic location error model and the bounded location error model,respectively.To solve those challenging non-convex problems,an iterative algorithm based on the SCA method,penalty function method and S-Procedure is proposed for the worst case while an iterative algorithm based on SCA method,penalty function method and Bernstein-type inequalities is proposed for the outage-constrained case.The proposed algorithms obtain effective suboptimal solutions to the corresponding problems.Simulation results confirm that the proposed schemes effectively improve the robustness of system secrecy energy efficiency.