Artificial Noise Based Secure Transmission Scheme in Multiple Antenna Systems

We consider a secure transmission from a transmitter with multiple antenna to a desired receiver with a single antenna in the presence of an eavesdropper. In order to increase the secrecy rate performance, we propose an artificial noise (AR) based secure transmission scheme. Usually, in conventional schemes, transmission power reserved for the AR has been equally allocated to all orthonormal basis vectors composing of the null space of the desired channel vector between the transmitter and the desired receiver. However, in the proposed scheme, the whole AR transmission power is allocated to only one optimal vector among the basis vectors composing of the null space. The optimal vector is obtained by solving an optimization problem that maximizes the signal-tointerference plus noise ratio (SINR) at the desired receiver on the condition that the SINR at the eavesdropper should be lower than a given threshold. Through computer simulation, we show that higher secrecy rate performance can be obtained by allocating more power to the desired message transmission rather than the AR transmission. Also, the proposed scheme has higher secrecy rate performance than the conventional scheme for different number of transmit antennas and for various power allocation cases.