This invention relates to signaling of resource assignments in cross-carrier scheduling scenarios. In order to enable cross-carrier scheduling in a mobile communication system using carrier aggregation while avoiding erroneous detection of assigned physical resources that could lead to HARQ soft buffer corruption/degradation of the system throughput, the invention suggests a scheme for explicitly indicating within downlink control information (DCI) including a resource assignment for the downlink (or uplink) the number of OFDM symbol(s) used for control signaling within a sub-frame on a component carrier on which resources are assigned by the DCI. In one exemplary implementation the number of OFDM symbol(s) used for control signaling is the PCFICH values signaled in a 3GPP LTE-A network. The indication of the OFDM symbol(s) within the sub-frame on the assigned component carrier may for example be jointly encoded with other control signaling information, e.g. with the carrier cation of the carrier indicator field.