Patent ID: RE44928

Claim:
A method of transmitting downlink control channels at a base station of an orthogonal frequency division multiplexing (OFDM) system, the method comprising: transmitting first information indicating related to a size m of a first region through a broadcast channel, wherein the first region is defined by m OFDM symbol(s) starting from a beginning of a subframe and the first region is used for first control channels that carry hybrid automatic repeat request (HARQ) ACK/NACKs; transmitting second information indicating related to a size n of a second region through a physical control format indicator channel (PCFICH), wherein the second region is defined by n OFDM symbol(s) starting from the beginning of the subframe and the second region is used for second control channels that carry downlink control information; and transmitting the HARQ ACK/NACKs and the downlink control information through the first control channels and second control channels, respectively, wherein first resources for the first control channels are identified from the first information, and second resources for the second control channels are identified from remaining resources excluding other than the first resources within the second region, and wherein the second control channels are physical downlink control channels (PDCCHs).