Full-Duplex Constant-Envelope Jamceiver and Self-interference Suppression by Highpass Filter: Experimental Validation for Wi-Fi Security

Unauthorized access to data has been a recognized risk of wireless systems for many decades. While security solutions in communications engineering have typically revolved around cryptography in the higher layers, a semi-recent development is the elevating interest into security in the physical layer, namely by utilizing jamming for protection. In this paper, we present an experimental study into a full-duplex jammer–receiver (i.e., “jamceiver”) that is able to simultaneously interfere with the same radio resources it is actively receiving from. The radio architecture is loosely based on frequency-modulated continuous-wave radars that are constant-envelope radio transceivers, which benefit from simple-but-efficient self-interference suppression in the analog baseband domain by using a passive highpass filter. Its limitation to constant-envelope transmission is not an issue for efficient jamming waveforms unlike it would be with conventional direct-conversion transceivers in full-duplex communications. To show the performance limits of a practical jamceiver, we present comprehensive measurement results from a laboratory environment as well as a jamming case study from an open park area with actual Wi-Fi signals. Especially, the experiments validate the feasibility of preventing eavesdropping with continuous low-power jamming in a large area around a full-duplex jamceiver that acts as an access point for simultaneously offering decent Wi-Fi service to an off-the-shelf laptop.