The present invention provides for a method and related system and communication terminal devices, for assigning a radio resource allocation mode to a mobile radio communications device for device-to-device communication within a wireless communication network environment, the method including the step of identifying at the mobile radio communications device an initial radio resource allocation mode and further including the step of signalling from the network to the mobile radio communications device configuration data relating to an authorized radio resource allocation mode to be employed for the device-to-device communication and defining at least one operation requirement of the mobile radio communications device when employing the said authorized mode.