Disclosed is a method comprising initiating, by an apparatus, an activation procedure for activating one or more positioning reference units for a positioning session of the apparatus; wherein the activation procedure is initiated via a small data transmission based on at least one of: a number of detected network nodes being above a first threshold value, or a number of detected positioning reference units being above a second threshold value; or wherein the activation procedure is initiated by transmitting an activation request to the one or more positioning reference units over sidelink based on the number of detected positioning reference units comprising at least the one or more positioning reference units.