Achieving Secrecy of MISO Fading Wiretap Channels via Jamming and Precoding With Imperfect Channel State Information

In this letter, we consider physical layer security in multiple-input single-output (MISO) fading wiretap channels, where the transmitter utilizes a jamming-aided precoding transmission strategy to maximize the achievable secrecy rate of the channel. The instantaneous channel state information of the eavesdropper's channel is considered unavailable at the transmitter. We derive the closed-form expression of the ergodic secrecy rate, based on which we find that there exists an optimal power allocation ratio between the information signal and the jamming signal. Asymptotic analysis shows that the optimal power ratio depends on the number of antennas as well as the available transmit power at Alice.