Multiantenna UAV-Assisted Secure Data Collection from Untrusted Backscattering Tags

Unmanned aerial vehicles (UAVs) are now being used to efficiently collect data from passive backscattering tags and support existing terrestrial links in the Internet of Things (IoT) when these links become overloaded. However, securing UAV-aided backscatter communication (BSC) in non-terrestrial networks is challenging due to the hardware limitations of passive tags. This paper introduces a secure BSC system utilizing a UAV for radio frequency (RF) signal transmission and data collection. Batteryless tags or backscatter devices (BDs) harness these RF signals to communicate with the UAV, even under untrusted scenarios where the BDs are mutually untrusted. We enhance the uplink fair-secrecy rate of the BDs by jointly optimizing the transmit and received beamforming vectors, artificial noise (AN), and power allocation while achieving the energy harvesting requirements and UAV flight constraints. Block coordinate descent (BCD) and fractional programming (FP) algorithms are used to address the non-convexity and obtain a fast converging solution. Simulation results verify the analysis, provide valuable insights, and demonstrate the substantial performance gains of our design for UAV-aided secure BSC in improving the fair-secrecy rate. Specifically, our proposed design achieves 0.19%, 2.08%, and 69.78% higher performance compared to three benchmarks.