Artificial Perturbation-Based OTFS Fractional Delay Estimation Approach for NavCom Signals

With the rapid development of low-orbit (LEO) satellites, the design of NavCom signals has increasingly become a focal point of research. Among this the orthogonal time-frequency space (OTFS) modulation operates in the Delay-Doppler (DD) domain, effectively mitigating the challenges of highly dynamic channels. Furthermore, the channel estimates obtained can be directly utilized for positioning. However, traditional OTFS is limited to integer delay estimation, which can introduce errors of nearly 100 meters. Most existing approaches have concen-trated on refining the solution algorithms, with accuracy levels approaching their theoretical limits. In this paper, an innovative method is proposed, which superimposes an artificial perturbation on the transmitter signal, causing the values at the receiver to follow a specific distribution and enabling fractional channel estimation after simple processing. This approach expands the theoretical limits of conventional channel estimation by increasing Fisher Information. Moreover, it can be integrated with other algorithms to achieve exceptional performance as an independent enhancement.