## 4 Propagation Loss Calculation Using the Improved TWPE Model
### Joint Effects of tropospheric Turbulence and Duct  
The same parameters as the previous section are used in this section to simulate the situation of Shanghai-Wuxi and Jiaxing-Wuxi without considering tropospheric turbulence.  
It can be seen from the comparison in Figures 15b and 16b of the range-dependent PL at the antenna level (60 m) that the non-uniform turbulence in the troposphere mainly affected the middle and rear sections of the intercity link. When considering the joint effect  
Figure 14: The (**a**) DEM and (**b**) propagation loss with tropospheric scattering, IGBP LC, and DEM were considered on Nanjing–Wuxi. (**a**) DEM from Nanjing to Wuxi. (**b**) Propagation Loss on Nanjing–Wuxi.  
Figure 13: The (**a**) DEM and (**b**) propagation loss with tropospheric scattering, IGBP LC, and DEM considered on Hangzhou–Wuxi. (**a**) DEM form Hangzhou to Wuxi. (**b**) Propagation loss on Hangzhou–Wuxi.  
of the tropospheric inhomogeneous turbulence and the duct, in the range of 0-40 km, the tropospheric turbulence made no obvious effects on ducting propagation. At the end of the intercity link of 40-70 km, the tropospheric turbulence effect reduced the PL of the duct. After 70 km of the intercity link, the joint effect of tropospheric inhomogeneous turbulence and ducting on PL was reduced relative to the middle part compared with the ducting-only propagation situation.  
Based on this, it can be concluded that the non-uniform turbulence model superimposed on the non-uniform tri-fold four-parameter hybrid duct has a boosting effect on the inter-city propagation at 40 km and further. This may lead to the fact that, on the urban link from surrounding cities to Wuxi, such as the Shanghai-Wuxi link, the downlink signal of the remote base station will likely interfere with the uplink signal at the first 20-60 km of the link, affecting the random uplink access user. After 60 km, or due to sudden changes in terrain, or being too far away, the PL of the two links at the antenna height of 60 m exceeds 160 dB, which means the sensitivity that can be distinguished by the receiver. Therefore, the possibility of remote interference is not considered, but simulated by the improved scattering PE model, the PL of this middle section of the path link is reduced, the signal of the transmitting section may propagate to the user area of this section, and remote interference may still occur. When considering the farthest distance that useful  
Figure 16: The PL on Shanghai–Wuxi (**a**) in space (**b**) at a height of 60 m. (**a**) PL on Shanghai–Wuxi without the troposcatter. (**b**) PL on S–W at a height of 60 m with or without the troposcatter.  
Figure 15: The PL on Jiaxing–Wuxi (**a**) in space (**b**) at a height of 60 m. (**a**) PL on Jiaxing–Wuxi without the troposcatter. (**b**) PL on J–W at a height of 60 m with or without the troposcatter.  
signals can propagate between intercity links, the PL calculated by adding the influencing factors of tropospheric turbulence in this section also shows that it is possible to deploy base stations as precise as possible based on ensuring accurate communications and no remote interference. For example, a base station relay can be set up at 20 km where similar terrain and LCs are distributed, such as Shanghai-Wuxi, and a base station relay can be assumed at 60 km where similar terrain and LCs are distributed, such as Jiaxing-Wuxi link. In addition, because the two intercity links are close together, if Wuxi receives a useful signal from the Jiaxing link under the influence of a stronger duct, it may also receive a remote signal from Jiaxing at the same time, causing user communication interference. It could be concluded that the influence of tropospheric turbulence has an important reference value for deploying base stations and avoiding remote interference between base stations.