Waveform Design of Low Complexity WR-OTFS System for the OOB Power Reduction

Abstract

Orthogonal time frequency space (OTFS) modulation is a recently proposed 2-D modulation technique that outperforms orthogonal frequency division multiplexing (OFDM), particularly in high-speed vehicle communications. However, the OTFS system has high out-of-band (OOB) power emission. A Novel PHY layer waveform candidate should be developed to overcome such issues for the next generation 5G and beyond 5G (B5G) mobile communication systems. In this paper, we propose a windowing and restructuring orthogonal time frequency space (WR-OTFS) system to reduce OOB power emission. In our proposed system, time-domain windowing is used at the transmitter to effectively reduce the OOB power emissions, and a very short window length is enough to meet the conventional spectral mask. Simulation results demonstrate that the proposed scheme significantly reduces OOB power emission compared to conventional OFDM and OTFS schemes. Moreover, we compare the uncoded BER performance among the different systems over AWGN and delay-Doppler channels for different user equipment (UE) speeds. The proposed scheme exhibits similar performance over AWGN and delay-Doppler channels as compared to the conventional OTFS system means without degradation of communication quality. Whereas, the OFDM performance completely breaks down in high-mobility scenarios. Simulation results show that the proposed WR-OTFS scheme can be reduced OOB power emission by 66 dB and achieved a gain of 10 dB over OFDM at BER of 1×10^-3.