the present invention relates to a base station arrangement in a communications system supporting high speed packet data communication , comprising a base station protocol entity for a protocol handling high speed control signalling and physical resource allocation for high speed data communication , quality handling means adapted to receive and handle channel condition related information from mobile user stations , encoding means for encoding data packets to be transmitted to mobile user station , and transmission control means comprising a scheduling means communicating with a hybrid automatic retransmission system and being adapted to control transmission of data packets using said channel condition related information and data packet buffering means . the base station protocol entity further comprises a control plane entity supporting an extended control plane for control plane signalling messages comprising specific control messages handling means , adapted to provide a specific probing or information control message and to send said message to a mobile user station .