A wireless transmit/receive unit (WTRU) receives a downlink subframe having multiple component carriers, each component carrier having control information encoded in a physical downlink control channel (PDCCH). The WTRU performs a blind decoding of control information in a first PDCCH located within a first component carrier to obtain a location of a second PDCCH located within a second component carrier, where the location of the second PDCCH is relative to a location of the first PDCCH as control channel element offset. The WTRU decodes the second PDCCH at the obtained location.