Physical Layer Anonymous Communications

In the era of the big data, anonymity is recognized as an important attribute in privacy-preserving communications. The existing anonymous authentication, encryption, routing and protocols are applied at higher layers of networks, and ignore the fact that physical layer (PHY) also contains privacy-critical information, such as the signalling patterns and the inherent characteristics of channel fading. These can be used to identify traffic patterns and reveal users' identities, inflicting an unprecedented vulnerability to potential anonymity-violating behavior. Hence, privacy threats start from the acquisition of data, which necessitates complementary privacy solutions that reside at PHY. In this paper, we introduce the concept of PHY anonymity, and reveal the fact that the receiver is able to unmask the sender's identity by only analysing the PHY information. We first propose a novel sender detection strategy at the receiver, and then we develop a corresponding anonymous precoding design to address sender's anonymity while guaranteeing high receive signal-to-interference-plus-noise ratio (SINR) for communications. Simulation verifies that the proposed anonymous precoder is able to preserve anonymity and simultaneously guarantee high receive performance for communication purpose, opening a new dimension on anonymous designs at PHY.