Evaluation of the security performance of artificial noise-aided STBC systems

In this paper, the security performance of artificial noise (AN)-aided space time block coding (STBC) systems in wiretap channel is evaluated. The security performance is estimated in terms of the secrecy rate, which is defined as the difference of mutual information of the legitimate receiver and illegal eavesdropper. We derive a generalized secrecy rate formula for the system utilizing AN-aided STBC, and also provide an expression for the approximated value with which the estimation time can be highly reduced. The simulation results reveal that the approximated formula well matches to the full estimation with a few orders of less complexity. In addition, it is proved that the maximum achievable secrecy rate for M-ary modulation scheme approaches to (Formula presented.) bps/Hz when AN power is extremely high, showing perfect security protection at the expense of power efficiency.