A novel interference signal superposition algorithm for providing secrecy to subcarrier number modulation-based orthogonal frequency division multiplexing systems.

Orthogonal Frequency Division Multiplexing with Subcarrier Number Modulation (OFDM-SNM) is a transmission scheme that aims to convey additional data bits by exploiting the number of active subcarriers. Even though OFDM-SNM creates many advantages, such as low bit error rate (BER), high spectral efficiency, and high reliability, it suffers from the security vulnerabilities against eavesdroppers and malicious wire-tappers. The reason why OFDM-SNM is vulnerable against security threats is that the nature of subcarrier number-based additional data transmission differs from the conventional data modulation techniques, which makes the existing physical layer security (PLS) applications to be inapplicable for OFDM-SNM. Therefore, novel PLS techniques must be developed for OFDM-SNM to secure the data that is transmitted by exploiting the number of subcarriers. In this paper, a novel interference signal superposition security algorithm for OFDM-SNM is proposed at the physical level to overcome its security vulnerabilities. The proposed security application aims to provide the data secrecy by embedding an artificial interference signal into the data that are meant to be conveyed by the active subcarriers. This artificial interference signal is created by exploiting the channel state information of the legitimate user, and deliberately included into the transmitted data to create a confusion for those who try to infiltrate the communication system, such as eavesdroppers or malicious wire-tappers. In this paper, the transmission of data for both the legitimate user and eavesdropper is operated by M-ary PSK/QAM modulation over a Rayleigh fading channel. The theoretical calculations and simulation results prove that the proposed security application for OFDM-SNM is a strong candidate to provide the security requirements of such cases in future wireless networks, where providing data secrecy is among the top priorities.