The present document relates to radio transmission. In particular, it relates to the mapping of frames in a GSM EDGE Radio Access Network (GERAN). A GERAN base station comprising a transceiver is described. The base station is operable to communicate with a first mobile station via a first VAMOS channel; to communicate with a second mobile station via a second corresponding VAMOS channel; and to use a control channel of the second VAMOS channel which is offset by 4 or 8 TDMA frames with respect to a control channel of the corresponding first VAMOS channel.