Secrecy rate region of independent parallel multiple-carrier two-way secure communications with secure feedback

In this paper, the secrecy rate region of independent parallel multiple-carrier two-way secure communications with secure feedback is investigated. The legitimate user securely feeds back the secret key to the other legitimate user via secure feedback link in the presence of a passive eavesdropper, and the latter legitimate user encrypts confidential message with the received secret key. It is first proved that the scheme of joint subcarrier has larger secrecy rate region than the one of subcarrier-by-subcarrier in the multiple-carrier system. With the scheme of joint subcarrier, the secrecy rate region is obtained, and the optimal power allocation is proved to be water-filling. Numerical results further show that the optimal power allocation outperforms uniform power allocation.