## 3 Results and Discussion
### Simulation Analysis of the Skywave OTH Channel Characteristics at 12:00 PM
It can be observed that at different times, the channel loss at midnight is greater than at noon, with the maximum attenuation (loss) reaching \(-134.43\) dB, fluctuating mostly around \(-119\) dB. The maximum attenuation (loss) fluctuates primarily around \(-119\) dB. The maximum channel delay can reach \(14.5\) ms, with most values fluctuating around \(6\) ms, while the minimum delay typically fluctuates around \(4\) ms. The maximum Doppler for the channel fluctuates around \(450\) Hz, and the lowest Doppler is \(0\) Hz, with most values fluctuating around \(150\) Hz. Figure 21 shows the range of channel characteristic parameter values for all path channels. It can be observed that at different times, the channel loss at midnight is greater than at noon, with the maximum attenuation (loss) reaching \(-134.43\) dB, fluctuating mostly around \(-119\) dB. The maximum attenuation (loss) fluctuates primarily around \(-119\) dB. The maximum channel delay can reach \(14.5\) ms, with most values fluctuating around \(6\) ms, while the minimum delay typically fluctuates around \(4\) ms. The maximum Doppler for the channel fluctuates around \(450\) Hz, and the lowest Doppler is \(0\) Hz, with most values fluctuating around \(150\) Hz. Figure 21 shows the range of channel characteristic parameter values for all path channels. It can be observed that at different times, the channel loss at midnight is greater than at noon, with the maximum attenuation (loss) reaching \(-134.43\) dB, fluctuating mostly around \(-119\) dB. The maximum attenuation (loss) fluctuates primarily around \(-119\) dB. The maximum channel delay can reach \(14.5\) ms, with most values fluctuating around \(6\) ms, while the minimum delay typically fluctuates around \(4\) ms. The maximum Doppler for the channel fluctuates around \(450\) Hz, and the lowest Doppler is \(0\) Hz, with most values fluctuating around \(150\) Hz. Figure 21 shows the range of channel characteristic parameter values for all path channels. It can be observed that at different times, the channel loss at midnight is greater than at noon, with the maximum attenuation (loss) reaching \(-134.43\) dB, fluctuating mostly around \(-119\) dB. The maximum attenuation (loss) fluctuates primarily around \(-119\) dB. The maximum attenuation (loss) fluctuates primarily around \(-119\) dB. The maximum channel delay can reach \(14.5\) ms, with most values fluctuating around \(6\) ms, while the minimum delay typically fluctuates around \(4\) ms. The maximum Doppler for the channel fluctuates around \(450\) Hz, and the lowest Doppler is \(0\) Hz, with most values fluctuating around \(150\) Hz. Figure 21 shows the range of channel characteristic parameter values for all path channels. It can be observed that at different times, the channel loss at midnight is greater than at noon, with the maximum attenuation (loss) reaching \(-134.43\) dB, fluctuating mostly around \(-119\) dB. The maximum attenuation (loss) fluctuates primarily around \(-119\) dB. The maximum attenuation (loss) fluctuates primarily around \(-119\) dB. The maximum channel delay can reach \(14.  
values for the main path (1 st path). It can be observed that at different times, the loss of the main path at midnight is greater than that at noon, and its delay is also higher. Due to the high elevation angle of the main path at midnight, its Doppler shift is smaller than that at noon. Figure 22 illustrates the characteristics of multipath numbers. It can be observed that compared with the stable four multipath numbers at noon, the number of multipaths varies significantly at midnight, ranging from a maximum of six to a minimum of four. Figure 19: Characteristic parameters of the multipath channel during re-entry in winter at 12:00 p.m.: (**a**) loss; (**b**) delay; (**c**) Doppler. Figure 20: The maximum and minimum values of the channel characteristic parameters for all paths at different times: (**a**) loss; (**b**) delay; (**c**) Doppler.