Embodiments herein relate to a user equipment and a radio network node, as well as to methods therein. The method in the radio network node relates to the control of resource allocation for D2D communications in a communications network. The network comprises the network node, a first user equipment, UE, and a second UE, wherein at least one of the first and second UEs is a first D2D capable UE. The method comprises configuring the second UE to transmit a reference signal; transmitting configuration information relating to the second UE to the first UE; receiving a measurement result of the measurement being performed by the first UE on the transmitted reference signal; and performing one or more radio operation task for a D2D communication between the first D2D capable UE and a second D2D communication capable UE based on the measurement result.