Abstarct: This thesis utilizes UAV as data collector from ground sensors placed at distances from each other, making access difficult. The aim is to optimize the power, trajectory, and scheduling of user transmissions in the presence of an eavesdropper. Signal transmission occurs considering the mobility of the UAV in line-of-sight channels. Users receive the energy needed for data transmission from RF signals and, given that the positions of users and eavesdropper are fixed and the UAV can reach them, the UAV's trajectory must be designed for users to send data to it with the highest secrecy rate. Additionally, we employ sleep-wake cycling techniques for energy savings. The problem is tackled using the successive convex approximation (SCA) method and the Dinkelbach algorithm. Simulations are conducted using the CVX tool in MATLAB, which utilizes an iterative algorithm to solve the problem. The results indicate that the joint optimization of user scheduling, UAV transmission power, and flight trajectory has significantly improved the maximum energy efficiency of the system.