Secure beamforming design in wiretap MISO interference channels

In this paper, we study the secrecy communication in two-user MISO interference networks where an eavesdropper is only interested in one of the transmitters, i.e., transmitter 1. We propose a generalized beamforming design to maximize the achievable secrecy rate of transmitter 1 while guaranteeing the quality of service (QoS) of the other destination. The non-convex problem can be transformed into a two-stage problem. The inner stage is a semidefinite program (SDP) problem based on the semidefinite relaxation (SDR) and the outer stage is a one dimensional line search problem. It is also shown in the proof that the SDR is always tight and yields a rank-one solution. Furthermore, we also propose a low-complexity null-space beamforming design scheme in which the beamforming vectors can be obtained by solving a second-order cone program (SOCP) problem. Simulation results show the effectiveness of the two proposed schemes in improving the secrecy rate performance.