The present invention relates to an arrangement supporting dual mode operation or communication with a core network node using a first and a second mode via a first and a second interface respectively. It comprises parameter handling means adapted to collect or receive first parameters comprising configurable traffic load related parameters and second parameters comprising current network traffic dependent parameters. It also comprises selecting means comprising calculating means adapted to use the configurable parameters and the current parameters of the parameter handling means to select the first or the second mode as operation mode for a connection of a mobile station to the core network.