Challenges for Volumetric Measurements Toward Radio Environment Map Construction for UAV Communications

The incorporation of unmanned aerial vehicles (UAVs) based nodes into upcoming and future wireless communications has recently become a substantial field of research. Consequently, problems related to spectrum utilization optimization and network coexistence have also gathered attention. Radio Environment Maps (REM) have been established as an important tool for spectrum usage analysis, and thus, their construction via UAVs has been explored by a number of influential studies. This paper provides a review of these works, on the basis of which, it describes the relevant challenges and procedures of performing real-time volumetric (i.e. in three-dimensional space) UAV-based measurements for aerial communications, and analysis of the gathered data in the temporal, frequency and spatial domains. These guidelines facilitate the construction of REMs as well as the further investigation for simulation-based spectrum management algorithms.