Joint Artificial Noise and Repetition Coding for Secure Wireless Communications in TDD Systems

In this letter, we study the secure transmission in the wireless single-antenna time division duplexing (TDD) system when there is a passive eavesdropper. A joint artificial noise and repetition coding scheme is designed, in which the artificial noise can be removed only by the legitimate receiver instead of the eavesdropper. We prove that by using the proposed scheme, the capacity of the wiretap channel is limited by an upper bound, and the achievable secrecy rate can be maximized by power allocation. Finally, simulation results are supplied to corroborate the theoretical analysis.