## 5 Conclusions and Future Works
### Future Work  
Based on the conclusions of this study, the field of NS ICNT in the future is expected to achieve breakthroughs and development in the following key directions:  
1. In-depth research and extended application of frequency bands. Although the advantages of the K/Ka frequency bands in the current ICNT in the NS have been clarified, in the future, it is still necessary to conduct in-depth research on their long-term stability and reliability in complex environments. For example, during the peak period of solar activity, the impact mechanism of ionospheric disturbances on K/Ka frequency band signals is not yet fully clear, and further exploration and the formulation of countermeasures are required. In addition, with the progress of technology, the possibility of using the K/Ka frequency bands in coordination with other emergingfrequency bands such as the terahertz frequency band can be explored to expand the communication bandwidth and application scenarios in NS and meet the growing demand for high-speed and large-capacity data transmission.
2. Innovation in signal loss mitigation technologies. Given the characteristics of the signal loss of the K/Ka frequency bands that change with factors such as frequency and elevation angle, efforts should be made in the follow-up to develop targeted anti-loss technologies. On the one hand, at the hardware level, by optimizing the antenna design, improving the antenna gain and pointing accuracy, the path loss and the influence of atmospheric scintillation can be reduced. On the other hand, in terms of signal processing algorithms, develop adaptive coding and modulation technologies, and dynamically adjust the coding and modulation methods according to the real-time signal loss situation to ensure the reliable transmission of signals.
3. Enhancement of adaptability to extreme environments. Rainfall attenuation has a significant impact on K/Ka frequency band signals. In the future, it is necessary to strengthen the research on signal transmission in extreme rainfall environments. By establishing a more accurate rainfall attenuation model and combining meteorological forecast data, early warning and compensation for rainfall attenuation can be achieved. At the same time, study comprehensive technical solutions to ensure stable signal transmission in extreme environments where complex interference factors such as the plasma sheath, multipath, Doppler effect, and noise coexist. For example, develop new signal processing algorithms to resist multipath interference and synchronization technologies that can effectively suppress the influence of Doppler frequency shift.  
In addition, the solution of the NS modulation signal based on hybrid modulation is a viable design solution for near-space ICNT, which is expected to meet the existing communication, navigation, and telemetry mission requirements for hypersonic vehicles entering the atmosphere. However, carrying out specific integrated signal design based on the K/Ka frequency band and the integrated signal design around higher frequency band signals such as the Q/V frequency band will also be key research directions in the future.  
Conceptualization, L.Y.; methodology, L.Y.; software, S.C.; validation, S.C. and L.Y.; formal analysis, L.Y., S.C. and Z.G.; investigation, Z.G., D.P., B.C., X.W., K.S. and Y.Y.; resources, S.C.; data curation, L.Y.; writing--original draft preparation, L.Y.; writing--review and editing, L.Y.; visualization, L.Y.; project administration, S.C.; funding acquisition, L.Y. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the China Project Management Center (Grant Nos. 80903010202, Funder. S.C.), Science and Technology on Electromechanical Dynamic Control Laboratory fund (Grant Nos. 9140A17060115 BQ42242, 6142601190210, Funder. S.C.).  
Not applicable.  
Data Availability Statement: Data is contained within the article.  
The authors declare no conflicts of interest.