Covert Communication of Terahertz Communication Systems With Ambient Backscattering

In this paper, we study the covert communication in terahertz (THz) communication systems with ambient backscattering, which involves a legitimate user and an eavesdropper. Specifically, we model the THz channel with multipath fading, path gain, and pointing errors, and characterize the multipath fading using the$\alpha -\mu$fading model. Based on this model, we derive the expressions for the probability density function (PDF) and cumulative distribution function (CDF) of some intermediate variables to facilitate the derivation of the final expressions. Moreover, we derive the asymptotic expressions for the outage probability (OP) and intercept probability (IP), as well as the closed-form expression for the covert rate (CR). By comparing the simulation results with the theoretical derivations, the correctness of the theory is verified. The results show that both multipath fading and pointing errors have a significant impact on the performance.