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The inheritance of the wireless broadcasting property leaves it exposed to eavesdropper attacks. The classical method to protect a wireless network’s upper layer is by using cryptography, but this method has not been proven as a rigid technique against passive eavesdropper’s attacks. Thus, a physical layer of security may be utilized to add built-in protection to the orthogonal frequency division multiplexing (OFDM) at no cost. The physical layer of security would allow communicating parties to exchange confidential information over a wireless medium, leaving an intruder nothing to hearing but noise. One of the goals of the next generation of mobile communications is to support different multiple-access schemes (Kumar & Gupta, 2018). Undoubtedly, the orthogonal frequency division multiple access (OFDMA) would be one of these schemes due to its high spectral efficiency (Lightfoot et al, 2009). OFDM is a form of multicarrier modulation which divides a high data rate modulating stream into multi-carrier lower modulated data rate streams using a different kind of digital modulation method (Zhang, 2010). Since the nodes are small, have no complex computational ability, are low in cost, and have limited power, it is not practical to have the OFDM transceiver built inside the node. Thus, the authors propose a new design to apply the OFDM system in IoT networks.
Unfortunately, the OFDM does not provide any security in its internal structure, which means that it’s physical layer can be intercepted by adversaries, making the OFDM vulnerable to eavesdropping attacks. Therefore, comprehensive research has been conducted to investigate the secrecy in multicarrier communication and OFDM (Jeong & Kim, 2011; Renna et al, 2010); Renna et al, 2011; Vishwakarma & Chockalingam, 2014). However, only a few research efforts have investigated the OFDM secrecy in IoT (Choi, 2017; Olfat & Bengtsson, 2017). Recently, research has been done to combine the frequency hopping (FH) technique with OFDM to add anti-jamming and anti-perception capabilities to the new systems (Lightfoot et al, 2009; Sari et al, 1997).