Multi-antenna system as an eavesdropper for directional beams

The paper studies the use of multiple antenna systems for eavesdropping of line-of-sight directional communication. The eavesdropper’s antennas are scattered around a certain area outside of the location of the legitimate receiver and attempt to collude and use channel state information to extract the transmitted message. The attack involves cases with and without artificial noise being generated by the transmitter. It is demonstrated, that while the system remains secure if the area controlled by the eavesdropper is limited, it is capable of intercepting portions of communication as such area grows. For a limited number of cases, it is possible for the eavesdropper to outperform the legitimate receiver. Furthermore, the proposed attack using channel state information yields similar performance for cases with and without the use of artificial noise by the transmitter.