Advanced OTFS communication system with compact spectrum and power efficiency improvement

Abstract

Orthogonal time frequency space (OTFS) modulation technique is one-step more precoded system of the conventional orthogonal frequency division multiplexing (OFDM) system, i.e., a double precoded system. The OTFS system was suggested especially for the robust and reliable high-speed vehicle communications and massive multiple-input multiple-output (MIMO) systems. Nevertheless, this basic OTFS system has serious problems: high out-of-band (OOB) power emission and high peak-to-average power ratio (PAPR). This high OOB power spectrum requires a very wide guard band that can produce a great loss of frequency utilization efficiency, and the power efficiency becomes very poor due to this high PAPR problem. Therefore, in this paper, in order to mitigate these drawbacks, an advanced OTFS communication system is proposed to show the compact OOB power spectrum and power efficiency improvement.This system can be designed by discrete Fourier transform (DFT)-spread windowing and restructuring-OTFS (DFT-Spread WR-OTFS) scheme that can reduce PAPR by 2.1 dB, 0.5 dB, 1.7 dB, and 1.8 dB compared to the conventional OFDM, DFT-Spread OFDM, basic OTFS and WR-OTFS schemes, respectively. Consequently, the efficiency of the high power amplifier (HPA) is improved due to the low PAPR of the proposed system. In addition, we comprehensively evaluate the impact of PAPR reduction performance on the OOB power spectrums and bit error rate (BER) performance of each system in HPA linear and nonlinear environments. Simulation results verify that the power spectrums and the BER performance of the proposed system are better than the conventional schemes in HPA nonlinear environments.