6G and Beyond: Synchronization Challenges and Solutions with OTFS Modulation using SDR

Orthogonal Time Frequency Space (OTFS) is a capable candidate to provide reliable communication in high mobility scenarios due to its resilience to high Doppler and multipath effects. Due to its close relation with Orthogonal Frequency Division Multiplexing (OFDM), it also has some synchronization challenges. In this paper, we discuss the impact of a specific synchronization challenge i.e. fractional Sampling Time Offset (STO), faced by OTFS modulation when implemented on a Software Defined Radio (SDR). Firstly, we discuss the impact of fractional STO on an OTFS frame, which appears like false multipath components in the Delay-Doppler domain. Then we propose a solution based on the interpolation of an already sampled waveform. We experimentally tested our OTFS system at 2.4 GHz carrier frequency in an office environment. With our proposed method, in the presence of fractional STO, the experimental results show significant improvements in Error Vector Magnitude (EVM).