## 4 Propagation Loss Calculation Using the Improved TWPE Model
### Effects of Different Land Covers
Therefore, the possibility of users receiving remote interference on the road section beyond the 45 km Shanghai-Wuxi link is small. If the road section undergoes urban renovation (biased towards the dark cyan line in URB,  
Figure 19: The PL using the improved TWPE with (**a**) BSV, (**b**) URB, (**c**) SAV LC, on Shanghai–Wuxi. (**a**) PL on S–W with BSV LC. (**b**) PL on S–W with URB LC. (**c**) PL on S–W with SAV LC. Figure 20: The MSE of PL using the improved TWPE between IGBP LC and different LCs, on Shanghai–Wuxi. (**a**) BSV-IGBP MSE of PL on S–W. (**b**) URB-IGBP MSE of PL on S–W. (**c**) SAV-IGBP MSE of PL on S–W. Figure 22), or vegetation green development (biased towards the dark yellow line in SAV, Figure 22), the propagation distances of the communication signal could vary according to the specific meteorological conditions and changes in the distribution of LC features. Therefore, according to the changes of the annual live updates of the LC types, the more finely the classification of LCs that may develop in the future, and the dielectric parameter values corresponding to the more accurate LC types, the reception range of communication signals could be estimated through a more accurate model. Figure 23 shows the PLs of over-the-horizon propagation on Jiaxing-Wuxi with three hypothetical LCs considering the joint effect of the tropospheric turbulence and duct. The parameters are the same as in the previous section. We used MSE to compare the PLs under three hypothetical LC types with the PLs under real IGBP LCs on the Jiaxing-Wuxi link, as shown in Figure 18a. The results are shown in Figure 24.  
On the path link of Jiaxing-Wuxi, the propagation distance was 93 km, but there was a high terrain fluctuation at 70 km. Figure 24 shows the MSE between the parameter conditions of the assumed single LC feature distribution and the real IGBP feature distribution. As can be seen from Figure 24, the MSE between the PL calculated on the assumed single LC type parameters and the PL calculated on the real LC parameters classified by IGBP started to grow from the top of the duct, which was also the energy leaking area at a distance of 70 km from Jiaxing. It was obvious that the MSE of PL at the antenna height was the smallest when the assumed LC was SAV, which was closely related to the distribution of LCs on the intercity link. According to IGBP terrain classification in Figure 9d, Jiaxing-Wuxi was mostly covered by water bodies, and also contained many types of landform switching. Figure 21: The propagation loss using the improved TWPE at a height of 60 m using different land covers, on Shanghai–Wuxi. (**a**) PL on S–W at different LCs at a antenna height of 60 m. (**b**) PL on S–W at a range of 20–40 km at different LCs. (**c**) PL on S–W at a range of 40–70 km at different LCs. (**d**) PL on S–W at a range of 70–115 km at different LCs. In order to clearly compare the influence of the PLs of the transmission signal in the ducting layer on Jiaxing-Wuxi link under the backgrounds of several different LC types, we compared the PLs of the link at a height of 60 m in the ducting layer, as shown in Figure 25.  
Figure 25 shows the range-dependent PL at the antenna height of 60 m on different LC types. As shown in Figure 21c, the PL increased sharply, which was around 200 dB. Therefore, the difference of the PL calculated using TWPE between a single LC and on IGBP LC was not obvious at 0-20 km. From the 20-40 km PL on the J-W of different LCs shown in Figure 25a, the over-the-horizon PL on IGBP LC was close to that on BSV LC, but higher than the results of the URB or SAV LC. The PL of IGBP LC was slightly smaller in the 0-20 km section of Jiaxing-Wuxi. The PL distribution of different LCs at 0-40 km on the antenna height layer was similar to that of the Shanghai-Wuxi link, which is helpful for the deployment of short-distance 5G base stations. The middle section at a range of 40-70 km was mainly affected by terrain fluctuations and ducts, and the PL was kept within a certain range.