Patent ID: 8494006

Claim:
A method for transmitting Channel State Information-Reference Signals (CSI-RSs) for eight or less antenna ports, the method comprising: transmitting the CSI-RSs in a downlink subframe, wherein the CSI-RSs are mapped to one Resource Element (RE) set among a plurality of RE set candidates, and one RE set includes a plurality of REs, wherein a number of the plurality of RE set candidates for eight antenna ports is five, wherein, in a resource region defined by 14 Orthogonal Frequency Division Multiplexing (OFDM) symbols and 12 subcarriers in the downlink subframe, the five RE set candidates for eight antenna ports include: a first CSI-RS RE group defined by third, fourth, ninth and tenth subcarriers on sixth and seventh OFDM symbols; a second CSI-RS RE group defined by first, second, seventh and eighth subcarriers on tenth and eleventh OFDM symbols; a third CSI-RS RE group defined by third, fourth, ninth and tenth subcarriers on tenth and eleventh OFDM symbols; a fourth CSI-RS RE group defined by fifth, sixth, eleventh and twelfth subcarriers on tenth and eleventh OFDM symbols; and a fifth CSI-RS RE group defined by third, fourth, ninth and tenth subcarriers on thirteenth and fourteenth OFDM symbols, wherein a plurality of RE set candidates for two antenna ports and a plurality of RE set candidates for four antenna ports are defined as a subset of the plurality of RE set candidates for the eight antenna ports.