On the use of artificial interference for secrecy with imperfect CSI

We study the use of artificial interference as a means of increasing the security of a multiple-input multiple-output (MIMO) wireless link against an eavesdropper when the CSI for the link is not precisely known. The presence of imperfect CSI will lead to interference leakage to the desired receiver, and a significant reduction in the secrecy rate of the channel. However, if the transmitter is aware of the second-order statistics of the CSI, a power adjustment can be made to reduce the interference at the receiver to a tolerable level, and still provide degradation to the eavesdropper. Surprisingly, simulations show that in some cases, only a small amount of artificial interference is necessary to achieve a significant gain in secrecy rate. However, if the CSI error is too large, there is little benefit to transmitting artificial noise.