The aim of the present invention is to provide an efficient and reliable transmission/reception mechanisms for a communication system with multiple component carriers, each of which further includes physical resources such as transmission slot/symbol, subcarrier/frequency subband, code, or radiation pattern. Accordingly, the control signal of a component carrier comprises a scheduling assignment specifying for said component carrier a resource for transmission of a data signal, and an allocation map specifying that a scheduling assignment has been sent for another component carrier. Signalizing the allocation map enables detection of possibly missed scheduling assignments.