A traffic concentrator (40) aggregates traffic in a radio access network. The traffic concentrator comprises an Asynchronous Transfer Mode (ATM) switch (42) and a control node (44) associated with the ATM switch. The Asynchronous Transfer Mode (ATM) switch which performs a switching operation for switching unspecified bit rate (UBR) virtual channels (VCs) carrying user traffic between plural virtual paths (VPs). The user traffic is transported as ATM Adaptation Layer 2 (AAL2) connections over the unspecified bit rate (UBR) virtual channels (VCs). The control node is arranged to process AAL2 signaling messages which concern the AAL2 connections included in the VCs for which the ATM switch performs the switching operation. The AAL2 signaling messages are carried in virtual channels which do not carry the user traffic and which are either originated or terminated at the control node. In one example implementation, the traffic concentrator aggregates traffic of plural base stations of the radio access network.