Secure Transmission in OFDM Systems by Using Time Domain Scrambling

In order to improve the confidentiality and security of orthogonal frequency division multiplexing (OFDM) systems, a physical layer security enhancement scheme by using time domain scrambling techniques is proposed in this paper. The approach is based on secretly scrambling the sample sequence within each time domain OFDM symbol, which is equivalent to constellation transformation over each subcarrier in the frequency domain. Consequently, the unique signal characteristics of the standardized OFDM transmission can be removed. The efficacy of the security enhancement is analyzed by means of the secrecy capacity. Moreover, related simulation results under the AWGN and the Rayleigh channel models indicate that our proposed scheme can improve the system secrecy significantly and the corresponding system performance will not be degraded.