Modeling of Millimeter-Wave Propagation in Tunnels with Split-Step Parabolic Equation Method

Radio wave propagation modeling in tunnels plays an important role in the deployment of modern train communication systems. The parabolic equation method has proven to be a powerful numerical technique for propagation modeling in long guiding structures. However, its computational efficiency is significantly compromised at millimeter-wave frequencies. This paper presents a split-step Fourier transform based parabolic equation model, which can achieve superior performance at the millimeter-wave bands. Numerical results are validated against analytical solutions in a waveguide example, as well as experimental measurements in an actual tunnel.