In this paper the results of intensive measurement campaigns performed inside the buildings in two locations (Poznan, Poland and Barcelona, Spain) are presented and analyzed to investigate their potential in the generation of digital indoor radio environment maps. The existence of such detailed and stable maps will allow for further definition of the allowed transmit power of small cell transceivers operating within indoor heterogeneous networks and making use of TeleVision White Spaces (TVWS). The analysis concentrates on the stability and repeatability of the measured values both over time and location, as key elements enabling the creation of aforementioned digital maps. ; Peer Reviewed ; Postprint (published version)