Secrecy Sum Rate Analysis and Power Allocation with OSTBC and Artificial Noise for MIMO Systems

This paper examines and analyzes the secrecy sum rate and optimal power allocation for a multiple input multiple output (MIMO) system. The orthogonal space time block coding (OSTBC) is used to bring the power of each user closer to the optimal value. In addition to the OSTBC method, an artificial noise (AN) technique is used to increase system security. This type of noise is injected into the signal which is sent to users by the base station (BS). In this paper, an optimization problem is considered with a maximum power constraint for users and a minimum rate constraint of each user. The secrecy sum rate is equal to the difference of each user’s rate and the eavesdropper’s rate, which must be a positive value, otherwise it is considered to be zero. The constrained optimization problem becomes an unconstrained problem using the Lagrangian dual function to find the optimal power of each user. Simulation and numerical results are given to evaluate the system performance. These results show that the proposed scheme has a better performance than the equal power allocation scheme in various scenarios.