Enhancement of Physical Layer Security in Alamouti OFDM Systems over Nakagami-m Fading Channels

In this work, we have combined an Alamouti spacetime block coded orthogonal frequency division multiplexing (OFDM) system with signal space diversity (SSD) in order to improve the physical layer security of a communication network under a Nakagami-m fading channel. Coordinate interleaving (CI) operation of the SSD technique is realized over the OFDM subcarriers. It is shown that various CI strategies can be used to make the correlation coefficients between the OFDM subcarrier channel gains equal to zero. The simulation results reveal that the legitimate user has a much better bit error rate performance than the eavesdropper even under the worst-case scenario where the eavesdropper somehow captures the CI strategy used between the transmitter and authorized receiver.