The proposed technology generally relates to radio resource management in wireless communication systems, which operate based on directive beams for serving one or more wireless user devices (120). A basic idea is to process image information obtained from one or more image sensors (115) to predict a change in radio propagation characteristics between a network node (110) of the wireless communication system and a user device (120), and to control a mobility reference signal for at least one directive beam in the wireless communication system and/or configure measurements of the mobility reference signal and/or configure reporting and/or processing of measurement results from measurements of the mobility reference signal, based on the predicted change in radio propagation characteristics.