Iterative Channel Estimation for OTFS Using ZC Sequence with Low Peak-to-Average Power Ratio

For low earth orbit (LEO) satellite communications, the robustness to high mobility and the low peak-to-average power ratio (PAPR) are two essential requirements. Orthogonal time frequency space (OTFS) modulation outperforms orthogonal frequency division multiplexing (OFDM) in high-mobility scenarios with doubly selective channels. However, the existing channel estimation schemes for OTFS usually contain high-power pilots, which cause high PAPR, while the current PAPR reduction schemes for OTFS usually ignore the impacts on channel estimation. This work proposes a novel channel estimation scheme utilizing a Zadoff-Chu (ZC) sequence as the pilot, with which the PAPR can be effectively reduced by proper pilot alignment. Then, an iterative ZC-sequence-based estimation algorithm is proposed, which adopts a correlation-based algorithm and a message passing (MP) algorithm to detect the pilot and data alternately. Simulation results show that the proposed scheme has a significantly lower PAPR in the time domain and superior channel estimation performance.