A Polar Coded OFDM System With Artificial Noise for Covert Communication
Hiroki Fukada, Hideki Ochiai · 2023
In this work, we introduce a covert communication system based on the superposition of polar-coded OFDM and artificial noise (AN) where the OFDM signal is used for information transmission. We show that the use of OFDM signaling makes the warden difficult to detect the signal from the received samples in the time domain due to the Gaussian nature of OFDM signals. On the other hand, when the warden is able to detect the samples in the frequency domain, we should rely on AN to increase the detection error probability of the warden. The price is its reduced effective SNR for the legitimate receiver. Therefore, we propose a use of polar codes with their code rate adjusted such that the desirable block error rate is achievable. The importance of frozen bit randomization is also discussed by analyzing the time-domain property of the resulting OFDM signals.