Is Ray-Tracing Viable for Millimeter-Wave Networking Studies?

The promise of millimeter-wave (mm-wave) frequencies for high capacity cellular networks depends on precise alignment of the narrow directional beams to either line-of-sight (LOS) or strong non-LOS links. Given this sensitivity of mm-wave communication to the spatial distribution of LOS/NLOS links, site-specific propagation data from ray-tracing simulations is an important tool for mm-wave networking studies. In this paper, we present the first detailed validation of mm-wave ray-tracing against large-scale outdoor measurements. We consider fine-grained angle-of-arrival (AoA), angle-of-departure (AoD) and received signal strength (RSS) data, using both horn and phased array antennas. We show that ray-tracing captures well the distribution of multipath clusters (MPCs) in terms of number of MPCs per receiver location, AoA, AoD and individual MPC structure. Moreover, our results indicate that ray-tracing provides accurate propagation data based on publicly available 3D building models which lack detailed material properties. Overall, our results show that individual propagation paths can be accurately identified in the ray-tracing data, with a median RSS prediction error within 5 dB of the measured RSS for all MPCs. This is an encouraging result which confirms the viability of ray-tracing propagation data as an input for mm-wave networking studies, on e.g. beam management protocols.