## 2 NS Communication, Navigation, and TT&C Integrated Frequency Selection
Therefore, through the above two points of analysis, the perspective of the design of the integrated communication, navigation, and TT&C system itself can be seen. Currently, increasing the operating frequency band is the only positive and effective measure to resist the plasma sheath and the blackout phenomenon. According to relevant information, it has been clearly demonstrated that the higher the frequency band, the better the effect of overcoming the blackout [57]. Therefore, from the perspective of overcoming the blackout, it is very advantageous to use the K/Ka high-frequency band, it has the advantages of high bandwidth, good beam directivity, few interference sources, and stable propagation, and is suitable for applications requiring high-speed and large-capacity data transmission. (5)  
Maturity of equipment development  
At present, the K/Ka band TT&C equipment is very mature, and its price is comparable to that of devices in other frequency bands; there are not too many difficulties in system design and equipment development. The new generation of geostationary communication satellites in the United States, Japan, Canada, China, and other countries basically use the K/Ka band for communication and transmission [58; 59]. The typical representatives of TT&C systems operating in the Ka band include TDRSS, NASA DSN, and ESA DSN [60; 61; 62]. In addition, the Q/V band has been rarely used, mainly due to problems such as immature technology and the need to develop key devices from the bottom up [63]. Combined with the current development trend, most countries encourage the application of higher frequency bands such as K/Ka for TT&C to meet the TT&C mission requirements of complex systems such as large-scale constellations in the future [64]. Combining the analysis of parts (1) to (5) in this subsection and the research references, the K/Ka frequency bands have great potential advantages compared with the traditional L/S/C frequency bands, as shown in Table 2; considering all the above factors, the K/Ka band is suitable for NS communication, navigation, and TT&C, but the Q/V band can be used as a backup/emergency band. Therefore, this paper focuses on the K/Ka band to analyze the impact of NS physical characteristics on its communication, navigation, and TT&C integration. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Comparison Items** & **K/Ka Frequency Band** & **L/S/C Frequency Bands** \\ \hline Frequency band distribution & K: 18–27 GH & L: 1–2 GHz \\  & Ka: 27–40 GHz & S: 2–4 GHz \\  & & Extremely large bandwidth, and supports high-speed data & C: 4–8 GHz \\ Comparison of transmission & Bandwidth & Extremely large bandwidth, and supports high-speed data & The bandwidth is relatively narrow, and the data rate is limited. \\ Comparison of transmission & Bandwidth & Typical values: 500–2000 MHz. & Typical values: 20–100 MHz. \\ characteristics & Atmospheric attenuation & It is significantly affected by rain attenuation and the absorption of oxygen/water vapor. & The attenuation is relatively low. \\  & & Typical values: 0.3 dB/km & Typical values: 0.02 dB/km–0.1 dB/km. \\  & & (sumny)–10 dB/km (torrential rain). & Strong penetrability (especially in the L frequency band, which is suitable for urban and indoor coverage). \\  & & It has relatively abundant spectrum resources and relatively less interference. & Typical values: \\  & & Short wavelength and a small antenna size & The antenna size is relatively large. \\ Equipment and cost & Antenna size & & Typical values: 1–5 m. \\  & The cost of & The cost of high-frequency devices is & The cost of mature silicon-based devices is low. \\  & & high. & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparative statistics of the advantages and disadvantages between K/Ka bands and traditional L/S/C bands.