The invention relates to a new structure of a control channel region within a sub-frame of a 3GPP-based based communication system using OFDM in the downlink. This new structure of a control channel region is inter alia particularly suitable for conveying physical downlink control channel information from a donor eNodeB to a relay node. The control channel region is divided in CCEs that have equal size irrespective of the presence of further cell-specific and/or UE-specific reference signals within the control channel region. This is achieved by dividing the control channel region in plural sub-CCEs that are combined to CCEs all having equal size (in terms of resource elements that can be used for the signaling of control information). The control channel region is divided in the frequency domain and/or time domain in a FDM respectively TDM fashion in order to obtain the sub-CCEs.