A method and apparatus of monitoring a physical downlink control channel (PDCCH) is disclosed. A starting location of a search space in a control region of a subframe k is acquired. The search space is defined by a set of PDCCHs at each aggregation level. The set of PDCCHs from the starting location in the search space at the each aggregation level is monitored. The starting location is defined by the multiple of the aggregation level in the control region.