A method is described for receiving a physical signal by a communication apparatus in a wireless communication system supporting carrier aggregation of a first component carrier and a second component carrier. The communication apparatus receives a physical downlink control channel (PDCCH) signal on the first component carrier. The communication apparatus also receives a physical downlink shared channel (PDSCH) signal corresponding to the PDCCH signal on the second component carrier. The first component carrier is different from the second component carrier. A starting orthogonal frequency division multiplexing (OFDM) symbol for receiving the PDSCH signal is determined according to information received via a radio resource control (RRC) signal.