Effective channel perturbation based on cyclic delay for physical layer security in OFDM systems

Orthogonal frequency division multiplexing (OFDM) offers a promising solution for emerging high-data-rate services. Moreover, physical layer security was proposed as an alternative way to provide information security in wireless communications. In this work, we focus on improving physical layer security in OFDM systems. Our approach perturbs the effective channels observed at eavesdroppers by nonlinear distortion, while maintaining the same effective channel experienced at the intended receiver. At the transmitter, the perturbation on eavesdropper´s effective channel is random and can be changed on a symbol-by-symbol basis based on the known original channel state information (CSI). At the intended receiver, no additional information or information exchange with the transmitter is required for data detection. We derive the results of the proposed scheme for the multiple-input single-output single-antenna-eavesdropper (MISOSE) wiretap channel. According to simulations, the proposed scheme can severely degrade the receiving performance at eavesdroppers and outperform the artificial-noise-based approaches in the performance measure of BER.