The present invention relates to providing control information within a search space for blind decoding in a multi-carrier communication system. In particular, the control information is carried within a sub-frame of the communication system, the sub-frame including a plurality of control channel elements. The control channel elements may be aggregated into candidates for blind decoding. The number of control channel elements in a candidate is called aggregation level. In accordance with the present invention, the candidates of lower aggregation levels are localized, meaning that the control channel elements of one candidate are located adjacently to each other in the frequency domain. Some candidates of the higher aggregation level(s) are distributed in the frequency.