Method and apparatus for providing channel state information-reference signal (CSI-RS) configuration information in a wireless communication system supporting multiple antennas

1. A method for transmitting a Channel State Information-Reference Signal (CSI-RS) from a base station supporting multiple transmit antennas to a mobile station, the method comprising:

transmitting, at the base station, information of one or more CSI-RS configurations to the mobile station;

mapping, at the base station, CSI-RSs to resource elements of at least one downlink subframe based on the one or more CSI-RS configurations; and

transmitting, at the base station, the at least one downlink subframe mapped with the CSI-RSs to the mobile station,

wherein the one or more CSI-RS configurations include:

i) at least one CSI-RS configuration for which the mobile station assumes non-zero transmission power for the CSI-RS,

ii) at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS, or

iii) at least one CSI-RS configuration for which the mobile station assumes non-zero transmission power for the CSI-RS and at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS, and

wherein the CSI-RSs of the at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS are used for an interference measurement of CSI feedback.

2. The method according to claim 1 , wherein the one or more CSI-RS configurations indicate positions of the resource elements mapped with the CSI-RSs.

3. The method according to claim 1 , wherein the at least one downlink subframe mapped with the CSI-RSs is configured by at least one CSI-RS subframe configuration, each of the at least one CSI-RS subframe configuration indicating a predetermined period and a predetermined offset.

4. The method according to claim 3 , wherein the at least one CSI-RS subframe configuration is configured separately for CSI-RSs for which the mobile station assumes non-zero and zero transmission power.

5. The method according to claim 1 , wherein the CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS corresponds to positions of resource elements where CSI-RSs of neighbor base station are transmitted.

6. The method according to claim 1 , wherein the CSI-RSs are transmitted for one, two, four or eight antenna ports.

7. The method according to claim 1 , further comprising:

transmitting, at the base station through dedicated Radio Resource Control (RRC) signaling, an indication of a CSI-RS configuration used for CSI feedback by the mobile station among the one or more CSI-RS configurations.

8. The method according to claim 1 , wherein the CSI-RSs of the at least one CSI-RS configuration for which the mobile station assumes non-zero transmission power for the CSI-RS are used for a channel quality measurement of CSI feedback.

9. A method for transmitting Channel State Information (CSI) at a mobile station using a Channel State Information-Reference Signal (CSI-RS) from a base station supporting multiple transmit antennas, the method comprising:

receiving, at the mobile station, information of one or more CSI-RS configurations from the base station;

receiving, at the mobile station, at least one downlink subframe of which resource elements are mapped with CSI-RSs based on the one or more CSI-RS configurations from the base station; and

transmitting, at the mobile station, the CSI measured by using the CSI-RSs to the base station,

wherein the one or more CSI-RS configurations include:

i) at least one CSI-RS configuration for which the mobile station assumes non-zero transmission power for the CSI-RS,

ii) at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS, or

iii) at least one CSI-RS configuration for which the mobile station assumes non-zero transmission power for the CSI-RS and at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS, and

wherein the CSI-RSs of the at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS are used for an interference measurement of CSI feedback.

10. A base station for transmitting a Channel State Information-Reference Signal (CSI-RS) for multiple antennas transmission, the base station comprising:

a receiver configured to receive an uplink signal from a mobile station;

a transmitter configured to transmit a downlink signal to the mobile station; and

a processor configured to:

control the base station including the receiver and the transmitter,

transmit, via the transmitter, information of one or more CSI-RS configurations to the mobile station,

map CSI-RSs to resource elements of at least one downlink subframe based on the one or more CSI-RS configurations, and

transmit, via the transmitter, the at least one downlink subframe mapped with the CSI-RSs to the mobile station,

wherein the one or more CSI-RS configurations include:

i) at least one CSI-RS configuration for Which the mobile station assumes non-zero transmission power for the CSI-RS,

ii) at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS, or

iii) at least one CSI-RS configuration for which the mobile station assumes non-zero transmission power for the CSI-RS and at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS, and

wherein the CSI-RSs of the at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS used for an interference measurement of CSI feedback.

11. A mobile station for transmitting Channel State Information (CSI) using a Channel State Information-Reference Signal (CSI-RS) from a base station supporting multiple transmit antennas, the mobile station comprising:

a receiver configured to receive a downlink signal from the base station;

a transmitter configured to transmit an uplink signal to the base station; and

a processor configured to:

control the mobile station including the receiver and the transmitter,

receive, via the receiver, information of one or more CSI-RS configurations from the base station,

receive, via the receiver, at least one downlink subframe of which resource elements are mapped with CSI-RSs based on the one or more CSI-RS configurations from the base station, and

transmit, via the transmitter, the CSI measured by using the CSI-RSs to the base station,

wherein the one or more CSI-RS configurations include:

i) at least one CSI-RS configuration for which the mobile station assumes non-zero transmission power for the CSI-RS,

ii) at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS, or

iii) at least one CSI-RS configuration for which the mobile station assumes non-zero transmission power for the CSI-RS and at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS, and

wherein the CSI-RSs of the at least one CSI-RS configuration for which the mobile station assumes zero transmission power for the CSI-RS are used for an interference measurement of CSI feedback.