PRN Sequence Deployment and Performance Evaluation of OTFS Modulation for LEO PNT

In recent years, low Earth orbit (LEO) broadband constellations have thrived and are expected to become a new reliable navigation source. Orthogonal time frequency space (OTFS) modulation has become a candidate modulation for the next generation of communication systems due to its superior performance in high-mobility channels. Therefore, in navigation modulation research based on broadband LEO constellations, the utilization of OTFS modulation to design navigation signals and provide performance evaluation is essential for satellite payload and ground receiver design. This work aims to investigate the typical variants and navigation performance of OTFS modulation for position, navigation and timing (PNT) services. By deriving analytical expressions for the power spectral density (PSD) and time domain signal, the navigation performance of OTFS is evaluated and compared with the major global navigation satellite system (GNSS) modulations. The results show that OTFS provides flexibility to adjust the periodicity and continuity by the deployment of pseudorandom noise (PRN) sequence on delay-Doppler grid, and has code tracking accuracy and compatibility advantages, anti-interference and anti-multipath performance is slightly better than that of the GNSS modulations with the same bandwidth. However, a disadvantage is the high complexity of signal tracking. Nevertheless, OTFS remains a valuable candidate for LEO PNT services.