Millimeter-wave Channel Modelling and Ray-tracing Method Validation

Millimeter-wave bands have been adopted for the fifth generation of mobile communication (5G) mainly due to large available bandwidths. However, the electromagnetic wave propagation characteristics in the millimeter-wave bands differ from those of conventional sub-6 GHz wireless communication bands, for example in their higher transmission and penetration losses, lower contributions from reflection and diffraction waves. Although the research on millimeter-wave channels has been conducted for years, some results show large differences in millimeter-wave path loss. These results indicate that the millimeter-wave channels may be site-specific. A model based on measurement results in one environment cannot always be used in other environments. Therefore, the ray-tracing method is an appropriate alternative for millimeter-wave channel estimation, a major reason for this being that the real environment model is involved in the simulation, which reflects the actual channel characteristics of the environment. In this study, a time-domain automatic channel measurement system, which comprised a millimeter-wave radio channel sounding system and an automatic antenna mechanical scanning system, was constructed for millimeter-wave channel measurements. The automatic channel measurement system greatly reduce the time and manpower involved in measurement and improve channel measurement accuracy. This study performed numerous millimeter-wave indoor channel measurements. The results were used to develop or validate millimeter-wave channel models such as path loss models, diffraction effect models, and human-body blockage models, etc.. Measurement results from an indoor environment were compared with the results simulated using the ray-tracing method. The results of the comparison demonstrate that the ray-tracing method can effectively simulate the arrival times of major transmission rays but cannot accurately estimate the strength of the rays.