Multi-antenna Wireless Legitimate Surveillance Systems: Design and Performance Analysis

Abstract

To improve national security, government agencies have long been committed to enforcing powerful
surveillance measures on suspicious individuals or communications. In this paper, we consider a wireless
legitimate surveillance system, where a full-duplex multi-antenna legitimate monitor aims to eavesdrop
on a dubious communication link between a suspicious pair via proactive jamming. Assuming that the
legitimate monitor can successfully overhear the suspicious information only when its achievable data
rate is no smaller than that of the suspicious receiver, the key objective is to maximize the eavesdropping
non-outage probability by joint design of the jamming power, receive and transmit beamformers at the
legitimate monitor. Depending on the number of receive/transmit antennas implemented, i.e., single-input
single-output, single-input multipleoutput, multiple-input single-output and multiple-input multipleoutput
(MIMO), four different scenarios are investigated. For each scenario, the optimal jamming power is
derived in closedform and efficient algorithms are obtained for the optimal transmit/receive beamforming
vectors. Moreover, low-complexity suboptimal beamforming schemes are proposed for the MIMO case.
Our analytical findings demonstrate that by exploiting multiple antennas at the legitimate monitor, the
eavesdropping non-outage probability can be significantly improved compared to the single antenna case.