Patent ID: 8315324

Claim:
A method for transmitting downlink control information by a base station, the method comprising: receiving feedback information including at least one precoding matrix index (PMI) from user equipment (UE); applying precoding to a downlink signal; transmitting precoding information having a predetermined number of bits, wherein the predetermined number of bits is defined according to a number of antenna ports and a transmission mode of the base station; and transmitting the precoded downlink signal, wherein the precoding information of a specific transmission mode includes confirmation information, wherein the confirmation information indicates that the precoding to the downlink signal for a specific resource block (RB) in n th subframe is according to a latest PMI received from the UE on or before n−x th subframe, wherein “x” is a predetermined integer or an integer determined by upper layer signaling higher than a physical layer, and wherein the confirmation information is used only for PMI received via a Physical Uplink Shared Channel (PUSCH), except for PMI piggy-backed in a PUSCH.