Measurement-Based Millimeter-Wave Angular and Delay Dispersion Characteristics of Outdoor-to-Indoor Propagation for 5G Millimeter-Wave Systems

Most outdoor-to-indoor (O2I) propagation studies in millimeter-wave (mmWave) frequency bands have been focused on power loss characteristics such as building penetration and building entry losses. To provide robust traffic services, knowledge of the multipath propagation characteristics is required in the design and evaluation of mmWave 5G systems. In this paper, we investigate the multipath dispersion characteristics of O2I propagation in the angular and delay domains. This study is based on field measurement data conducted at 32 GHz in two different office building sites: traditional building and thermally-efficient building. To derive reliable statistics, we collected measurement data at as many points as possible throughout the building areas (including various environments such as open-space offices, conference rooms, classical closed-room offices, computer labs, halls, corridors, etc). By analyzing power angular and power delay profiles, we found that there were two dominant signal directions and we considered how this property can be utilized in mmWave beamforming. By comparing the angular and delay spreads, we found that the angular and delay statistics do not show any significant differences between the two building measurements. We believe that the property of dominant beam directions, as well as the dispersion statistics (angular and delay spreads), will be useful in the 5G system design.