In this work, the above-referenced 2D solver is extended to 3D, resulting in the first-ever full wave solver capable of analyzing large-scale and realistically loaded mine environments. Just like its 2D counterpart, the scheme divides long mine tunnels into short sections and separately analyzes EM wave propagation in each subdomain. To characterize tunnel sections of tens to hundreds of wavelengths long, the 3D scheme uses a parallel surface integral equation solver accelerated by both fast multipole and fast Fourier transform (Taboada et. al., IEEE Antennas Propag. Mag., 51(6), 20-28, 2009). To obtain a global inter-domain solution, the scheme introduces equivalent surface currents on the air interfaces between subdomains; these currents are derived from modal solutions for an unperturbed waveguide and constitute a reduced basis sets for characterizing EM wave propagation throughout the long tunnel. The method¹s efficiency and applicability will be demonstrated via the simulation of communication links inside realistic mine tunnels
