Patent ID: 8675589

Claim:
A method for transmitting channel state information-reference signals (CSI-RSs) for 8 or fewer antenna ports at a base station, the method comprising: transmitting the CSI-RSs for the 8 or fewer antenna ports, wherein the CSI-RSs are mapped according to a predetermined pattern to a data region of a downlink subframe having an extended cyclic prefix (CP) configuration, wherein the predetermined pattern is defined such that the CSI-RSs for the 8 or fewer antenna ports are mapped to two consecutive orthogonal frequency division multiplexing (OFDM) symbols in the data region of the downlink subframe and are mapped to one or more of four subcarrier locations in each of the two consecutive OFDM symbols, in one resource block pair, wherein the two consecutive OFDM symbols are OFDM symbols to which User Equipment (UE)-specific reference signals are allowed to be mapped, and wherein the four subcarrier locations are defined in the predetermined pattern and include “n”-th subcarrier index, “n+3”-th subcarrier index, “n+6”-th subcarrier index, and “n+9”-th subcarrier index.