Circulant Shift-based Beamforming for Secure Communication with Low-resolution Phased Arrays

Authors: Kartik Patel, Nitin Jonathan Myers, Robert W. Heath Jr.
Submitted to Transactions on Wireless Communications



Millimeter wave (mmWave) technology can achieve high-speed communication due to the large available spectrum. Furthermore, the use of directional beams at mmWave provides a natural defense against physical layer security (PLS) attacks. In practice, however, the beams are imperfect due to mmWave hardware limitations such as the low-resolution of the phase shifters. The imperfections in the beam pattern introduce an energy leakage that can be exploited by an eavesdropper. To defend against such eavesdropping attacks, we propose a directional modulation-based defense technique where the transmitter applies random circulant shifts of a beamformer. We show that the use of random circulant shifts together with appropriate phase adjustment induces artificial phase noise (APN) in the directions different from that of the target receiver. Our method corrupts the phase at the eavesdropper without affecting the communication link of the target receiver. We also experimentally verify the APN induced due to circulant shifts, using channel measurements from a fully reconfigurable 2-bit mmWave phased array testbed. Using simulations, we study the performance of the proposed defense technique against a greedy eavesdropping strategy in a mobile vehicle-to-infrastructure (V2I) scenario. The proposed technique achieves better defense than the antenna subset modulation technique, without compromising on the communication link with the target receiver.

Additional results

AirSpy attack on 1-bit phased arrays (Refer to Sec. VI.B in paper)

AirSpy attack on 2-bit phased arrays (Refer to Sec. VI.B in paper)