Wireless base station device for handling wireless communication, e.g. DECT, between a plurality of associated wireless terminals and an IP network. The base station device has a radio transceiver, a network interface, and a processor with communication application and a communication session management software. The communication session management is arranged to control a communication session with an associated wireless terminal (upper layer management), while wireless communication with said associated wireless terminal involved with said communication session (lower layer) is handled by another base station device. Thus, the base station can manage separate operation of its upper and lower layer, thereby enabling e.g. hand-over of a session to and from other base stations. This allows self contained single casing base station devices to operate in a network without the need for at central server, and still such network is easy to extend by adding base stations.