## 2 A Multi-Source Real Data Model for Intercity Link Communication Propagation Computing
### Data Extraction of Land Cover Distribution Types of Intercity Links from MODIS
#### 2.3.1 Land Cover Type Distribution on Intercity Links of East China
After consulting a large number of literature studies, we chose to use the test results in the literature to solve the simulation in this paper. The land types involved in several intercity links selected in this paper mainly include: 9 Savannas, 10 grasslands, 11 permanent wetlands, 12 croplands, 13 urban and built-ups, 15 snow and ice, 16 barren or sparsely vegetated, 17 water bodies. According to [24], we chose the following experimental results: the permittivity of 18.2 + 4.5i of sandy loam from a frequency of 3 GHz and water content of 0.3 g/cm\({}^{3}\) as the permittivity of barren or sparsely vegetated; the no. 16 classification in the IGBP land cover (LC) rule. Silty clay in Figure 10 was selected as the no. 11 classification in the IGBP LC rule when the frequency was 1.4 GHz and the water content \(m_{\
u}=0.45\); that is, the permittivity of the permanent wetland WET was assumed as \(26.5+1.2\)i. By referring to Reference [25], the crops with large soil fertility contribution rates distributed in the selected area (north China region) were mainly rice. The dielectric permittivities of rice leaves of 50 rice growth days of were selected as the permittivities of crops (CRO) in the IGBP classification (i.e., 4.0 + 10.93). Moreover, the permittivity of  
Figure 9: Land Cover types of IGBP on intercity links from four different cities to Wuxi. (**a**) LC distribution on Hangzhou–Wuxi. (**b**) LC distribution on Nanjing–Wuxi. (**c**) LC distribution on Shanghai–Wuxi. (**d**) LC distribution on Jiaxing–Wuxi. rice straw grown for 10 days was taken as the permittivity of the savanna (SAV) in IGBP classification, which was 2.85 + i0.33. According to Reference [26], combined with the test results, the permittivity of asphalt in the oil-generating area was generally \(\epsilon^{\prime}=5\)\(\sim\)15, \(\epsilon^{\prime\prime}=0.070\)\(\sim\)0.30. Then we chose the dielectric permittivity of the asphalt of the intermediate state as the permittivity of urban and built-up (URB) areas in the IGBP classification, which was 5 + i0.070. In Reference [27], from the relationship that the complex dielectric permittivity of wet snow versus water content or frequency at natural conditions (as shown in Figure 11), we choose the snow and ice (SNO, 15 th classification in IGBP LC) dielectric permittivity 15.8 - i1.8, when the frequency was 3 GHz, the water content was 0.3, and the temperature was \(-\)5 \({}^{\circ}\)C.  
The reference dielectric permittivity values used for the land cover types ultimately involved in this paper are listed in Table 3.  
This paper used the WRF database source, MCD12Q1 land cover classification from MODIS, terrain relief from the DEM to model the over-the-horizon propagation of communication signals at a sub-6 frequency band, comprehensively considering atmospheric ducts and tropospheric inhomogeneous turbulence. The schematic diagram of the over-the-horizon propagation of intercity links is shown in Figure 12.  
Figure 11: Dielectric permittivity of snow at different volumetric moisture/frequencies. (**a**) Dielectric constant vs. Volumetric moisture. (**b**) Dielectric constant vs. Frequency. Figure 10: Dielectric permittivity of wet soil at different volumetric moisture or frequencies. (**a**) Dielectric constant vs. Volumetric Moisture. (**b**) Dielectric constant vs. frequency. Scattering Parabolic Equation Algorithm for Irregular Terrain and Inhomogeneous Turbulent Atmosphere  
When 5G signals are transmitted between cities, irregular terrain relief and dielectric roughness exist on the lower boundary of the atmospheric duct. At the same time, there may be non-uniform turbulence in the duct layer and even its upper and lower boundaries. This paper considers the actual situation and studies the radio wave propagation based on the complex meteorological environment when ducting and turbulence occurs. Compared with many existing terrain models, after research and comparison, a wide-angle shift-map (WASM) algorithm was determined in the terrain boundary processing of the WAPE model.