# A Novel Signal Design and Performance Analysis in NavCom Based on LEO Constellation
## 5 Conclusions and Outlook  
Based on the S-band LEO constellation, this article designs a signal scheme suitable for NavCom. It uses CE-OFDM-PM (2) for modulation. At the same time, the signal generation system and process are described in this paper. After simulation experiments, via comparing different signal systems, we found that it has excellent accuracy potential, better compatibility, excellent anti-multipath ability, and outstanding anti-narrowband interference performance. Additionally, it has impressive communication link tradeoff indicators, such as BER, \(C/N\), and \(E^{b}/N_{0}\) etc. From a theoretical viewpoint, it provides a brand-new perspective for the integration of the NavCom of LEOs.  
At the same time, the flexibility of CE-OFDM-PM (2) in the signal system also has the potential to achieve interconnection and intercommunication with many wireless terminals. It has significant signal application and engineering application prospects for the larger-scale integration of NavCom and PNTs in the future.  
The theoretical feasibility and simulation accuracy of the scheme proposed in this study will provide a foundation for subsequent work on LEO satellite networking, verification work for different types of carriers, and performance testing at different frequencies.  
In the future, we will focus our work on the adaptability of spread spectrum-modulated signals in multi-orbit constellations. This will be a core step in the process of CE-OFDM-PM from design to engineering and implementation. On the one hand, we will consider the Doppler effect caused by the relative motion between the receiver and the transmitter. On the other hand, we will also combine various vehicles for use in verification. This will be the main work of our team in the future. Our work will also provide a foundation for a comprehensive roadmap to be made for the PNTRC scheme.  
Figure 23: Downlink parameters via STK. According to the above simulation constraints, the received power (Rcvd. Iso. Power), carrier-to-noise ratio (C/N), and bit-to-noise ratio (Eb/N0) of a single satellite signal received on the ground are \(-136.507\) to \(-125.752\) dBW, \(7.0514\) to \(17.8062\) dB, and \(13.072\) to \(23.827\) dB, and the bit error rate (BER) is from \(1\times 10^{-30}\) to \(9.47\times 10^{-11}\). The power of the receiver is obviously lower than the power level of the communication receiver. At the same time, the carrier-to-noise ratio tolerance and signal quality are maintained at an extremely high level. Considering that the actual low-orbit satellites will be completely covered by multiple constellations, the rate of bit errors will be further reduced, and a remarkable level will be maintained.  
**Author Contributions:** [PERSON], [PERSON] and [PERSON] researched and designed the signal scheme in NavCom. [PERSON], [PERSON] and [PERSON] performed the experiments. [PERSON], [PERSON] and [PERSON] analyzed the data. [PERSON] and [PERSON] wrote the manuscript. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was funded by the Technological Innovation Project (Major Program) of Hube Province under Grant 2019 AAA025. And supported by National Key Research and Development Program under Grant SQ2021 YFB3900243, Jiangxi Province Key R&D Program under Grant 20181 ACE50027, and the Jiangxi Province 03 Special Project and 5G Project under Grant 20193 ABC03A006.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.