Transmit filter and artificial noise aided physical layer security for OFDM systems

This paper considers the problem of physical layer security of a wireless orthogonal frequency division multiplexing (OFDM) communication system. We first develop a transmit filter-aided secure OFDM system scheme which can disturb eavesdropper's receptions by destroying the orthogonality of OFDM signals at the eavesdropper, while the quality of legitimate transmission is maintained. Then, in an effort to further improve the security performance, we also propose an artificial noise (AN)-aided secure OFDM system associated with the transmit filter-aided approach. AN is generated in the null space of the legitimate channel by making use of residual power after power allocation for subcarriers. Therefore, AN can only disrupt eavesdropper's receptions but not affect legitimate receiver. Simulation results are presented to illustrate the efficiency of the proposed transmit filter and AN-aided physical layer security designs in the OFDM wiretap system.