A method for transmitting channel quality information for a downlink channel. The method according to one embodiment includes receiving, by a User Equipment (UE), configuration information on periodic channel state information (CSI) reporting by higher layer signaling; and determining, by the UE, a channel quality information index at least based on a UE-specific reference signal overhead. The UE-specific reference signal overhead is determined according to a rank value. The method according to the one embodiment further includes transmitting the determined channel quality information index to a base station. The channel quality information index is determined further based on an assumption of no resource element allocated for a Channel Status Information-Reference Signal (CSI-RS).