Secrecy Performance of Backscatter Communications With Multiple Self-Powered Tags

Backscatter communication (BackCom) networks are vulnerable to eavesdropping, while its secrecy performance has not been sufficiently studied. In this letter, we propose a tag selection strategy to optimize the ergodic secrecy capacity (ESC) and the secrecy outage probability (SOP) simultaneously for a multi-tag self-powered BackCom network in the presence of an eavesdropper. Concretely, an adaptive power reflection coefficient scheme is first designed to maximize the instantaneous secrecy capacity per tag, based on which the one with the highest secrecy capacity is selected to backscatter message. To evaluate the resulting secrecy performance, we first obtain the exact cumulative distribution function of the instantaneous secrecy capacity under independent but non-identically distributed Nakagami- $m$ fading channels, and then derive the ESC and the SOP, respectively. Simulation results validate the theoretical analyses and demonstrate that the proposed strategy is superior to the existing strategies.