On the channel estimation of low-PAPR waveform for 5G Evolution and 6G

In order to mitigate the high peak-to-average power ratio (PAPR) of the uplink waveform, the frequency domain spectrum shaping (FDSS) and pi/2 BPSK modulation are adopted to DFT spread orthogonal frequency-division multiplexing (DFTs-OFDM) for both data and pilot transmission in 5G new radio (NR). However, generating such pilot sequences with acceptable orthogonality and reduced PAPR causes a computationally intensive search. This paper introduces the constant envelope (CE) OFDM waveform for both pilot and data transmitting with a PAPR of 0dB. Especially, an modified channel estimation scheme with the optimized selection of modulation index is proposed to overcome the non-flat power spectral density caused by phase modulation in CE-OFDM. Numerical results prove the superiority of the proposed low-PAPR waveform over the classical NR signal in terms of both PAPR and BER performance.