Secure Orthogonal Transform Division Multiplexing (OTDM) Waveform for 5G and Beyond

In this letter, a secure waveform design for future 5G wireless system is proposed. The developed waveform referred to as secure orthogonal transform division multiplexing (OTDM) waveform, is designed to diagonalize the multi-path channel matrix of only the legitimate receiver (Bob), while degrading eavesdropper's reception. In particular, instead of using fixed exponential basis functions, generated by IFFT and FFT as in OFDM, orthogonal transform basis functions, which are extracted from the Bob's channel, are utilized to modulate and demodulate the data symbols securely. The simulation results prove that the proposed design provides a significant practical security gap between the Bob's and Eve's performance. The design is shown to be robust against channel imperfection, and it neither sacrifices communication resources nor considers any knowledge on the eavesdropper's channel. Besides security, the scheme results in a higher SNR, leading to a 3-5-dB gain over OFDM at BER = {10^{-3}} .