Overhead-Free Channel Estimation based on Phase-domain Injected Training for FM-OFDM

Frequency-Modulated Orthogonal Frequency-Division Multiplexing (FM-OFDM) is a novel constant envelope multi-carrier waveform proposed to be exploited in high-mobility scenarios, which is a typical case to be coped in the 6G. Moreover, it also exhibits a strong robustness to phase noise and carrier frequency offsets. However, it assumes that the channel estimates are perfectly given. In this paper, phase injected training (PIT) is proposed in order to obtain accurate enough channel estimates with a zero overhead for the case of FM-OFDM, since the pilot symbols are embedded in the phase component of the data symbols. Theoretical expressions and numerical results prove the feasibility of FM-OFDM using a realistic channel estimation method.