As compared to the conventional cloud computing, the wireless offloading feature of the recently advocated mobile-edge computing (MEC) imposes a new risk of disclosing possibly private and sensitive user data to eavesdroppers. Physical-layer security approaches built on information theoretic methods are believed to provide a stronger notion of privacy than cryptography, and therefore, may be more suitable for defending eavesdropping in MEC. Nonetheless, incorporating a physical-layer security technique may fundamentally change the mobile users' offloading decisions. This suggests a compelling need for new judiciously designed offloading schemes that can jointly reap the benefits of both physical-layer security and MEC. With this consideration, a novel physical-layer assisted privacy-preserving offloading scheme is proposed in this work, in which the edge server proactively broadcasts jamming signals to impede eaves-dropping and leverages full-duplex communication technique to effectively suppress the self-interference. Finding the optimal jamming power of the edge server and the corresponding optimal offloading ratio of the mobile user turns out to be a challenging bilevel optimization problem. By exploiting the structure of the considered problem, two efficient algorithms are developed for delay optimal and energy optimal privacy-preserving offloading, respectively. Numerical results are presented to validate the effectiveness of the proposed schemes.
