As a new communication technology, Intelligent Reflecting Surface (IRS) can
intelligently reconfigure the wireless propagation environment by integrating many passive/active reflective elements on the plane. According to
the characteristics that IRS can adjust the propagation channel
intelligently, this paper applies IRS to wireless security communication,
and studies how to make the security rate reach the optimal security
capacity from the perspective of optimization technology. In this paper,
two schemes of passive/active IRS are considered, and the corresponding
safety rate maximization algorithm is proposed. In view of the non convexity
of the objective function, on the one hand, in the passive IRS scheme, the
Dinkelbach method is used to transform the objective function into a form
that is easy to handle, and the original problem is transformed into a
convex problem through the continuous convex approximation method; On the
other hand, under the active IRS scheme, aiming at the complexity of the
original problem, the first order Taylor expansion is used to obtain the
lower bound of the optimization problem, and a minimax optimization
algorithm is proposed. Finally, the performance of the proposed algorithm is
verified by simulation. The simulation results show that the algorithm
designed with active IRS has better security rate than the algorithm
designed with passive IRS under the same parameter settings.