Multi-Antenna Signal Masking and Round-Trip Transmission for Privacy-Preserving Wireless Sensing

Due to the openness of wireless medium and the public structure of pilot signals, wireless sensing procedure is vulnerable to eavesdropping, which causes privacy concerns. In this paper, a novel physical layer obfuscation solution termed as multi-antenna signal masking is proposed to realize privacy-preserving sensing. The privacy protection is realized via controlling the phase difference between the sensing signals of different antennas. Considering the fact that the channel state information (CSI) variation caused by changes of the physical environment typically slowly varies with time, the phase difference is designed as a slowly-varying function with temporal-correlation such that the real variation pattern in CSI is masked and the eavesdropper is thus unable to perform sensing based on the measured CSI. Furthermore, we also devise a round-trip transmission method to avoid secret information exchange between legitimate users, hence realizing privacy-protection without additional overhead. Simulation results demonstrate the superiority of the proposed method in terms of sensing accuracy and privacy-protection capability compared with existing works.