Non-Orthogonal Waveform (NOW) for 5G Evolution and 6G

High frequency bands with large bandwidth (e.g., millimeter-wave and terahertz frequencies) is promising for 5G Evolution and 6G, but the system design is restricted by the non-linearity of power amplifier (PA). Multi-carrier waveform of orthogonal frequency division multiplexing with cyclic prefix (CP-OFDM) may not be suitable for 5G Evolution and 6G due to its high peak to average power ratio (PAPR). Single carrier waveform represented by discrete fourier transform spreading OFDM (DFT-s-OFDM) with low PAPR could be a promising candidate waveform for 5G Evolution and 6G. Considering the extreme high data rate requirement of 5G Evolution and 6G, how to keep the low PAPR of DFT-s-OFDM and improve its spectral efficiency (SE) will be the challenge especially when high-order modulation is not applicable. In this paper, we propose a non-orthogonal waveform (NOW) to improve the SE of DFT-s-OFDM and derive the optimal time domain compression factor in terms of SNR based lossless compression. Furthermore, we investigate the impact of different compression factors to the system performance of throughput and PAPR. Simulation results demonstrate that the proposed scheme can achieve both throughput gain and PAPR gain over the traditional orthogonal waveforms DFT-s-OFDM and CP-OFDM, by flexibly adjusting the compression factor. When the compression factor is smaller than the optimal value, SNR loss to different extent may be observed.