GNSS-Independent Uplink LEO Satellite Synchronization

In a nonterrestrial network (NTN) with low earth orbit (LEO) satellites, there could be substantial Doppler shifts due to the relative movement between the satellites and the user equipment (UE). If the UE does not have global navigation satellite system (GNSS) capability, pre-compensation of the Doppler shifts cannot be made. Thus, synchronization signals are required which could be detected subject to large frequency offsets. We propose superposed pairs of interleaved Zadoff-Chu (SPI-ZC) synchronization sequences, each ZC sequence being interleaved by a linear permutation polynomial (LPP). The LPP renders a large set of sequences and sequences with improved peak-to-sidelobe-ratio (PSR) in the periodic correlation function, which improves the probability of correct synchronization. Lower detection complexity can be achieved compared to prior synchronization methods.