Downlink Synchronization for OTFS-Based Cellular Systems in High Doppler Environments

This paper proposes a downlink synchronization and cell identity (CID) estimation technique for cellular systems based on orthogonal time-frequency space (OTFS). In the proposed technique, each base station (BS) transmits one detection preamble (DP) two OTFS symbols (pilot secondary-CID (SCID) signal (SS)). The DP linear frequency-modulated (LFM) waveform, called proposed-LFM (pLFM), carries primary-CID (PCID) symbol timing (ST) synchronization, whereas SS Zadoff-Chu (ZC) sequence mapped in delay-Doppler domain SCID. pLFM is obtained by discretizing LFM increasing frequency sweeping parameter beyond limit of operational bandwidth, incorporating PCID into waveform. autocorrelation cross-correlation functions are analyzed to examine its correlation properties under influence high Doppler shift. To reduce undesirable (side peak time ambiguity), receiver processing (RP) scheme developed pLFM. It found that with RP suitable design because it can provide an accurate ST high-mobility scenarios. addition, modulation ZC derived low-complexity algorithm message passing applied detect SCID at user equipment. simulation results demonstrate CID techniques OTFS-based high-Doppler environments.