GPI-Based Secrecy Rate Maximization Beamforming Scheme for Wireless Transmission With AN-Aided Directional Modulation

In a directional modulation network, a general power iterative (GPI) based beamforming

scheme is proposed to maximize the secrecy rate (SR), where there are two optimization variables required to

be optimized. The ?rst one is the useful precoding vector of transmitting con?dential messages to the desired

user while the second one is the arti?cial noise (AN) projection matrix of forcing more AN to eavesdroppers.

In such a secure network, the paramount problem is how to design or optimize the two optimization variables

by different criteria. To maximize the SR (Max-SR), an alternatively iterative structure (AIS) is established

between the AN projection matrix and the precoding vector for con?dential messages. To choose a good

initial value of iteration process of GPI, the proposed Max-SR method can readily double its convergence

speed compared to the random choice of initial value. With only four iterations, it may rapidly converge to

its rate ceil. From simulation results, it follows that the SR performance of the proposed AIS of GPI-based

Max-SR is much better than those of conventional leakage-based and null-space projection methods in the

medium and large signal-to-noise ratio (SNR) regions, and its achievable SR performance gain gradually

increases as SNR increases.