## 8 Conclusions  
This paper investigates the navigation potential of OFDM-based LEO broadband constellations and demonstrates that it can achieve a 5.61 cm 3D positioning accuracy. We assume the satellites transmit a 5G NR signal and introduce the structure of NR, focusing on reference signals applicable for navigation service such as SSB, DMRS, and CSI-RS, along with CP OFDM modulation. The PSD of NR reference signals is derived and used for the theoretical analysis of tracking performance. Subsequently, the workflow of the LEO NR navigation system is outlined, encompassing the transmitter, channel, and navigation receiver. A ZPC is proposed for the tracking loop to eliminate CP and inter-carrier interference, ensuring that navigation performance remains unaffected by CP and communication data. Based on the tracking loop, an EKF positioning algorithm is developed. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Mean**} & \multicolumn{3}{c}{**Std**} \\  & & **North** & **East** & **Down** & **3D** & **North** & **East** & **Down** & **3D** \\ \hline \multirow{5}{*}{Position error (m)} & Noise & \(-\)0.0184 & 0.0252 & \(-\)0.0454 & 0.0561 & 0.0055 & 0.0050 & 0.0096 & 0.0059 \\  & Noise and clock & \(-\)0.0184 & 0.0252 & \(-\)0.0454 & 0.0561 & 0.0055 & 0.0050 & 0.0096 & 0.0059 \\  & Noise, clock, & \(-\)1.2169 & \(-\)0.1098 & 1.8210 & 2.1951 & 0.0135 & 0.0928 & 0.0537 & 0.0445 \\  & Noise, clock, & \(-\)1.7307 & 1.7201 & 5.1643 & 5.7143 & 0.0540 & 0.1142 & 0.1938 & 0.1591 \\  & ION, and TRO [2] & \(-\)1.7307 & 1.7201 & 5.1643 & 5.7143 & 0.0540 & 0.1142 & 0.1938 & 0.1591 \\ \hline \multirow{5}{*}{Velocity error (m/s)} & Noise & \(0.0005\) & \(-\)0.0039 & 0.0069 & 0.0487 & 0.0169 & 0.0267 & 0.0459 & 0.0281 \\  & Noise and clock & \(0.0005\) & \(-\)0.0039 & 0.0069 & 0.0487 & 0.0169 & 0.0267 & 0.0459 & 0.0281 \\ \cline{1-1}  & Noise, clock, & \(-\)0.0184 & \(-\)0.0055 & 0.0502 & 0.0696 & 0.0170 & 0.0268 & 0.0460 & 0.0341 \\ \cline{1-1}  & ION, and TRO & \(-\)0.0199 & \(-\)0.0279 & 0.0857 & 0.1024 & 0.0172 & 0.0274 & 0.0461 & 0.0347 \\ \hline \hline \end{tabular}  
* ION denotes ionospheric; 2 TRO denotes tropospheric.  
\end{table} 
Table 6: Position and velocity error statistics for different error components. Figure 17: Position and velocity error with different error components. We validate the interference-free property of ZPC and compare ZPC with conventional SSB and CON receivers in tracking performance. The experiment results demonstrate that the ZPC receiver has a significant improvement in tracking accuracy. The comprehensive analysis evaluates navigation performance impacted by NR signal bandwidth, spectral allocation, reference signal proportion, and replica signal combinations. This parametric investigation provides theoretical support for tracking accuracy enhancement of the LEO NR system. A LEO satellite motion scenario is simulated to characterize channel properties. Based on the EKF, the positioning performance of the LEO NR system and the impacts of error sources are systematically evaluated. The simulation results provide configuration recommendations for implementing opportunity navigation in LEO broadband constellations. This study proposes a low-cost, repeatable, and efficient methodology for analyzing LEO navigation performance through software simulation. As LEO broadband constellations are primarily designed for communication services, future research should focus on developing integrated communication and navigation receivers. Conceptualization and original draft preparation, L.D. and X.Q. ; theory and methodology, Y.Y. and H.L. ; validation and data analysis, L.D. and J.M. ; data curation and supervision, L.D. and T.W. ; project administration, Y.Y. All authors have read and agreed to the published version of the manuscript. This research was funded by \"Key Laboratory of Intelligent Space TTC&O (Space Engineering University), Ministry of Education, NO. CYK2024-01-01\", and Grant \"50903020401\".