Propagation modeling in complex tunnel environments: A comparison of vector parabolic equation and ray-tracing solutions

Radio-wave propagation in tunnel environments has been a topic of interest for decades. In this paper, a vector parabolic equation (VPE) solver together with an image-theory based ray-tracer is applied to deal with complex, realistic tunnel geometries. The comparison of the results of the two methods with each other and with the measured data leads to important observations with respect to the discretization errors in complex tunnel environments and the trade-offs between computational cost and accuracy, in both VPE and ray-tracing.