With the rapid development of the fifth-generation (5G) mobile communication technology,the application of each frequency band has reached the extreme,causing mutual interference between different modules.Hence,there is a re-quirement for detecting filtering and preventing interference.In the troposphere,over-the-horizon propagation occurs in atmospheric ducts and turbulent media.The effects of both ducting and turbulence can increase the probability of occur-rence of long-distance co-channel interference (CCI),in turn,severely affecting the key performance indicators such as system access,handover and drop.In the 5G era,to ensure communication channels and information security,CCI must be reduced.This paper introduces a scattering parabolic equation algorithm for calculating signal propagation in atmospheric ducts on irregular terrain boundaries.It combines Hitney\'s radio physical optical model and Wagner\'s nonuniform turbu-lent scattering model for calculating the tropospheric scattering in an evaporation duct or a surface-based duct.The new model proposes a tropospheric scattering parabolic equation algorithm for various tropospheric duct environments.Finally,as a specific case,the topographical boundaries between several cities in the East China Plain were considered,and the over-the-horizon propagation loss was simulated for various ducting and turbulent environments.The simulation results were used to evaluate whether CCI would occur between cities in a specific environment.