Channel state information feedback method and apparatus in a multi-node system

1. A method of feeding back channel state information of a user equipment (UE) in a multi-node system including a plurality of nodes and a base station connected to each of the plurality of nodes, the base station controlling the plurality of nodes, the method comprising:

receiving a reference signal of N nodes, wherein N is a natural number equal to or more than 2;

aligning the N nodes in an order of preferring the N nodes based on a result of measuring the reference signal;

generating channel state information for the aligned nodes; and

transmitting the generated channel state information to the base station, wherein the channel state information is generated with respect to N node combinations configured from the aligned nodes, and wherein the N node combinations are obtained by adding next highest-priority nodes to a first node combination one by one, the first node combination consisting a highest-priority node among the aligned nodes.

2. The method of claim 1 , wherein when N is 3, and node 1 , node 2 , and node 3 are aligned in an order of the node 1 , the node 2 , and the node 3 , the N node combinations include {node 1 }, {node 1 , node 2 }, and {node 1 , node 2 , and node 3 }.

3. The method of claim 1 , further comprising:

receiving channel state information (CSI) feedback node set information from the base station, the CSI feedback node set information indicating a node set to which the channel state information is generated, wherein the CSI feedback node set information directly indicates the N nodes or a value of N.

4. The method of claim 1 , further comprising:

receiving information on the maximum number of assignable nodes from the base station, wherein the information on the maximum number of assignable nodes indicates the maximum number of nodes to which the UE can generate the channel state information.

5. The method of claim 1 , wherein in channel state information for the N node combinations, channel state information for an n+1th node combination includes a differential value from channel state information for an nth node combination, wherein n is any one of 1 to N−1.

6. The method of claim 5 , wherein the number of bits of a field for transmitting the channel state information for the n+1 th node combination is equal to or less than the number of a field for transmitting the channel state information for the nth node combination.

7. The method of claim 1 , wherein in channel state information for the N node combinations, a differential value between channel state information for an n+1th node combination and channel state information for an nth node combination is configured as a predetermined table.

8. The method of claim 7 , wherein the channel state information for the n+1th node combination and the channel state information for the nth node combination are transmitted as index values in the predetermined table.

9. The method of claim 1 , wherein when the N nodes include a plurality of types, the UE selects as a highest-priority node any one of nodes having a signal characteristic of a predetermined threshold or more among a predetermined type of nodes of the plurality of types of nodes.

10. The method of claim 9 , wherein the plurality of types of nodes are distinguished from each other based on transmission power of the nodes.

11. The method of claim 10 , wherein the plurality of types of nodes include high-power nodes having relatively high transmission power and low-power nodes having relatively low transmission power, wherein the high-power nodes use a cell-specific reference signal common for all UEs in a cell, and the low-power nodes use a UE-specific reference signal applied to a particular UE.

12. The method of claim 1 , wherein the channel state information includes at least one of a channel quality indicator (CQI) indicating channel quality, a pre-coding matrix index (PMI) providing information on a pre-coding matrix in codebook-based pre-coding, or a rank indicator (RI) which is information on the number of layers recommended by the UE.

13. A user equipment (UE) comprising:

an RF unit configured to transmit and receive a wireless signal; and

a processor connected to the RF unit, the processor configured to receive a reference signal of N nodes, wherein N is a natural number equal to or more than 2, to align the N nodes in an order of preferring the N nodes based on a result of measuring the reference signal, to generate channel state information for the aligned nodes, and to transmit the generated channel state information to the base station, wherein the processor is configured to generate the channel state information with respect to N node combinations configured from the aligned nodes, and wherein the N node combinations are obtained by adding next highest-priority nodes to a first node combination one by one, the first node combination consisting a highest-priority node among the aligned nodes.