Method and apparatus for transmitting or receiving an additional demodulation reference signal based on a channel state information reference signal resource pattern

1. A method in a downlink subframe with an extended cyclic prefix (CP), in which a resource to which a first resource pattern for mapping a first demodulation reference signal (DM-RS) is configured, through a first set of antenna ports in a wireless communication system, the method for transmitting a second DM-RS which is mapped to different resources to which the first DM-RS is mapped, the second DM-RS being added to support a second set of antenna ports to a user equipment (UE), the method comprising:

specifying subframe(s) in which a channel state information reference signal (CSI-RS) is not transmitted and positions of resources to which the CSI-RS is mapped in subframe(s) in which the CSI-RS is transmitted based on CSI-RS configuration information;

selecting a second resource pattern for mapping the second DM-RS from among resources, corresponding to the specified positions of the resources, in the subframe(s) in which the CSI-RS is not transmitted; and

mapping the second DM-RS to the second resource pattern in the subframe(s) in which the CSI-RS is not transmitted.

2. The method according to claim 1 , further comprising transmitting the second resource pattern or CSI-RS configuration information indicating the second resource pattern to the UE.

3. The method according to claim 1 , further comprising transmitting information on a number of antenna ports in the second set used to transmit the second DM-RS to the UE.

4. The method according to claim 1 , wherein the selecting of the second resource pattern comprises selecting a resource having a subcarrier index different from a subcarrier index of a resource to which a cell-specific reference signal is allocated.

5. The method according to claim 1 , wherein the mapping of the second DM-RS comprises applying a length-4 orthogonal cover code (OCC) to complex-valued modulation symbol(s) for the first DM-RS and complex-valued modulation symbol(s) for the second DM-RS in a direction of a time domain.

6. The method according to claim 1 , wherein the second resource pattern is composed of as many resource elements as a number of resource elements constituting the first resource pattern.

7. The method according to claim 1 , wherein the mapping of the second DM-RS comprises:

dividing each of the first resource pattern and the second resource pattern into a first sub-pattern and a second sub-pattern; and

mapping a complex-valued modulation symbol for the first DM-RS to the first sub-pattern of the first resource pattern;

mapping a complex-valued modulation symbol for a third DM-RS, transmitted through a third set of antenna ports having as many antenna ports as a number of antenna ports in the first set, to the second sub-pattern of the first resource pattern,

mapping a complex-valued modulation symbol for the second DM-RS to the first sub-pattern of the second resource pattern; and

mapping a complex-valued modulation symbol for a fourth DM-RS, transmitted through a fourth set of antenna ports having as many antenna ports as a number of antenna ports in the second set, to the second sub-pattern of the second resource pattern,

wherein the first resource pattern is divided into the first sub-pattern and the second sub-pattern such that the first sub-pattern and the second sub-pattern have a same frequency domain density and the second resource pattern is divided into a first sub-pattern and a second sub-pattern such that the first sub-pattern and the second sub-pattern of the second resource pattern have a same frequency domain density.

8. The method according to claim 1 , wherein the second resource pattern includes at least one of resource element (RE) pairs positioned at (3x+k′, 4) and (3x+k′, 5) in each slot of a physical resource block (PRB) pair in the subframe, wherein x=0, 1, 2 and 3, k′=0 or 2 if n s mod 2=0, k′=0 or 1 if n s mod 2=1, n s denotes a slot index, and (m, n)=(subcarrier index, orthogonal frequency division multiplexing (OFDM) symbol index) in each slot of the PRB pair.

9. A method in a downlink subframe with an extended cyclic prefix (CP), in which a resource to which a first resource pattern for mapping a first demodulation reference signal (DM-RS) is mapped is configured, through a first set of antenna ports in a wireless communication system, the method for receiving a second DM-RS which is mapped to different resources to which the first DM-RS is mapped, the second DM-RS being added to support a second set of antenna ports, the method comprising:

receiving the second DM-RS on a resource corresponding to a second resource pattern,

wherein the second resource pattern is selected for mapping the second DM-RS from resources, corresponding to positions of the resources, in subframe(s) in which a channel state information reference signal (CSI-RS) is not transmitted, and

wherein the subframe(s) in which the CSI-RS is not transmitted and the positions of the resources to which the CSI-RS is mapped in subframe(s) in which the CSI-RS is transmitted are specified based on CSI-RS configuration information.

10. An evolved Node-B (eNB), in a downlink subframe with an extended cyclic prefix (CP), in which a resource to which a first resource pattern for mapping a first demodulation reference signal (DM-RS) is mapped is configured, through a first set of antenna ports in a wireless communication system, the eNB configured to transmit a second DM-RS which is mapped to different resources to which the first DM-RS is mapped, the second DM-RS being added to support a second set of antenna ports to a user equipment (UE), the eNB comprising:

a memory; and

a processor connected to the memory and configured to:

specify subframe(s) in which a channel state information reference signal (CSI-RS) is not transmitted and positions of resources to which the CSI-RS is mapped in subframe(s) in which the CSI-RS is transmitted based on CSI-RS configuration information,

select a second resource pattern for mapping the second DM-RS from among resources, corresponding to the specified positions of the resources, in the subframe(s) in which the CSI-RS is not transmitted, and

map the second DM-RS to the second resource pattern in the subframe(s) in which the CSI-RS is not transmitted.

11. A user equipment (UE), in a downlink subframe with an extended cyclic prefix (CP), in which a resource to which a first resource pattern for mapping a first demodulation reference signal (DM-RS) is mapped is configured, through a first set of antenna ports in a wireless communication system, the UE configured to receive a second DM-RS which is mapped to different resources to which the first DM-RS is mapped, the second DM-RS being added to support a second set of antenna ports, the UE comprising:

a memory; and

a processor connected to the memory and configured to:

receive the second DM-RS on a resource corresponding to a second resource pattern,

wherein the second resource pattern is selected for mapping the second DM-RS from among resources, corresponding to positions of the resources, in subframe(s) in which a channel state information reference signal (CSI-RS) is not transmitted, and

wherein the subframe(s) in which the CSI-RS is not transmitted and the positions of the resources to which the CSI-RS is mapped in subframe(s) in which the CSI-RS is transmitted are specified based on CSI-RS configuration information.