Interpolation Accuracy Evaluation for 3D Radio Environment Maps Construction

The characterization of the wireless spectrum in modern and future communications has been established as an important field of research, particularly in view of the increasing densification of terrestrial and aerial network nodes. Radio Environment Maps (REMs) have been prominently utilized for volumetric spectrum occupancy analysis and the design of algorithms for resource allocation but their construction relies on interpolation methods due to the limited availability of measurements. This paper evaluates four such estimators for two datasets collected in real-world environments in three-dimensional (3D) space - indoor through an automated measuring tool, and outdoor through a UAV-based sensor. The process of calibration of the interpolation methods is described, and their performance is assessed, reaching a minimum error of -7 dB. The influence of the distance between the measurement points and the estimated ones, on the accuracy, is analyzed. The findings in this work facilitate the further analysis in 3D signal propagation and REM prediction.