Method and apparatus for transmitting downlink reference signal in wireless communication system supporting multiple antennas
A method and apparatus for transmitting a downlink reference signal in a wireless communication system supporting multiple antennas is disclosed. A method for transmitting Channel State Information-Reference Signals (CSI-RSs) for eight or less antenna ports includes selecting one of a plurality of CSI-RS Resource Element (RE) groups defined on a data region of a downlink subframe and mapping CSI-RSs for the eight or less antenna ports to the selected CSI-RS RE group, and transmitting the downlink subframe in which the CSI-RSs for the eight or less antenna ports are mapped. The plurality of CSI-RS RE groups is defined such that a transmission diversity RE pair for data transmitted on the downlink subframe is not broken.
1. 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.
2. The method according to claim 1 , wherein one RE set candidate is shifted with respect to another RE set candidate in at least one of time domain and frequency domain.
3. The method according to claim 1 , wherein CSI-RSs for two antenna ports among the CSI-RSs for the eight or less antenna ports are multiplexed using a Code Division Multiplexing (CDM) scheme using orthogonal codes of a length of 2 over two contiguous OFDM symbols on the same subcarrier.
4. A method for measuring channel information from Channel State Information-Reference Signals (CSI-RSs) for eight or less antenna ports, the method comprising:
receiving the CSI-RSs in a downlink subframe; and
measuring the channel information based on the CSI-RSs for the eight or less antenna ports,
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.
5. The method according to claim 4 , wherein one RE set candidate is shifted with respect to another RE set candidate in at least one of time domain and frequency domain.
6. The method according to claim 4 , wherein CSI-RSs for two antenna ports among the CSI-RSs for the eight or less antenna ports are multiplexed using a Code Division Multiplexing (CDM) scheme using orthogonal codes of a length of 2 over two contiguous OFDM symbols on the same subcarrier.
7. A base station for transmitting Channel State Information-Reference Signals (CSI-RSs) for eight or less antenna ports, the base station comprising:
a reception module configured to receive an uplink signal from a user equipment;
a transmission module configured to transmit a downlink signal to the user equipment; and
a processor configured to control the base station including the reception module and the transmission module,
wherein the processor is further configured to transmit, using the transmission module, 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.
8. A user equipment for measuring channel information from Channel State Information-Reference Signals (CSI-RSs) for eight or less antenna ports, the user equipment comprising:
a reception module configured to receive a downlink signal from a base station;
a transmission module configured to transmit an uplink signal to the base station; and
a processor configured to control the user equipment including the reception module and the transmission module,
wherein the processor is further configured to receive, using the reception module, the CSI-RSs in a downlink subframe; and to measure the channel information based on the CSI-RSs for the eight or less antenna ports,
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.