Building-To-Building Propagation Loss Measurements At 3.5 Ghz With Application To Micro Operators

Recently proposed micro operator concept aims at providing high quality services in specific locations such as hospitals, shopping malls, campuses, or factories, to complement traditional mobile network operators' (MNO) broadband offerings. Micro operators address reliable 5G service delivery with predefined quality guarantees through local small cell deployments especially inside buildings with locally issued spectrum access rights. To properly characterize the resulting interferences in this new 5G deployment scenario with potentially a large number of local indoor networks by different 5G micro operators, accurate propagation loss modeling between the micro operator networks in adjacent buildings is needed. So far there is only one path loss model from indoor small cell to a user equipment (UE) inside a different building proposed by 3GPP, which could be used to model the micro operator scenario. To verify the applicability of this model, we conducted building-to-building propagation loss measurements at University of Oulu campus in Finland in the 3.5 GHz band. Measurement results were compared to the ones obtained from the 3GPP model. Significant differences were found between measurements and model when the default model value for outer wall penetration loss was used. This leads to the conclusion that a single outer wall penetration loss value is insufficient but multiple penetration loss values are needed. Also, for campus scenario with mostly line-of-sight measurement cases, it may be more appropriate to use free space path loss instead of switching to a higher path loss exponent after a breakpoint distance. Finally, the measurements indicate that offset values relatively to the 3GPP-like model are needed for modeling the building-to-building propagation in campus environment, which are proposed in the paper.