Security and Energy Efficiency: Breaking the Barriers of High Peak-to-Average Power Ratio and Disguised Jamming in NextG IoT System Design

As a popular modulation technique in wireless communications, OFDM has two major disadvantages-one is its high peak-to-average power ratio (PAPR), which causes nonlinear distortion, lower power efficiency and performance losses; the other is its fragility under hostile jamming attacks, where the authorized user's signal is deliberately interfered by the adversary, leading to communication failures. In this paper, first, we reintroduce the IFFT-Relocated OFDM (IR-OFDM), which is essentially a single-carrier system with frequency domain equalization. By relocating the IFFT block in OFDM from the transmitter to receiver, IR-OFDM can completely liberate OFDM from the barriers of high PAPR while achieving the same spectral efficiency. Second, to combat hostile jamming, especially disguised jamming, where the jamming is highly correlated with the authorized signal, we propose a securely precoded IR-OFDM (SP-IR-OFDM). By integrating AES into IR-OFDM transceiver design, we obtain a random (or dynamic) constellation. The shared secure randomness introduced by AES breaks the symmetry between the authorized signal and the jamming interference, and hence ensures reliable performance of the system under disguised jamming. The efficiency and robustness of IR-OFDM and SP-IR-OFDM are demonstrated through simulation examples. It is shown that IR-OFDM can deliver comparable or better performances than OFDM under multipath propagation, and SP-IR-OFDM can achieve strong resistance under disguised jamming while enjoying low PAPR and relatively high spectral efficiency. Our result indicates that, potentially, SP-IR-OFDM can serve as a promising modulation candidate for next generation secure and energy-efficient high-speed communications, especially for the resource-constrained IoT networks.