Method for transceiving channel state information and apparatus therefor in multiple-antenna wireless communication system
A method and an apparatus for transmitting and receiving channel state information in a multi-antenna wireless communication system are disclosed. Specifically, a method for reporting channel state information (CSI), by a User Equipment (UE), in a multi-antenna wireless communication system, the method comprising receiving, from a base station, configuration information for single CSI reporting in which a non-precoded CSI-RS based CSI reporting and a beamformed CSI-RS based CSI reporting are combined, reporting a first Precoding Matrix Indicator (PMI) and/or a first Rank Indicator (RI) derived based on a non-precoded CSI-RS to the base station, and reporting a Channel Quality Indicator (CQI), a second PMI, and a second RI based on a beamformed CSI-RS to the base station, wherein a value of the first RI is determined as only a value belonging to a previously determined set.
1. A method for reporting channel state information (CSI), by a User Equipment (UE), in a multi-antenna wireless communication system, the method comprising:
receiving, from a base station, configuration information for single CSI reporting in which a non-precoded CSI-RS based CSI reporting and a beamformed CSI-RS based CSI reporting are combined;
reporting information derived based on the non-precoded CSI-RS to the base station,
wherein the information comprises a first Precoding Matrix Indicator (PMI); and
reporting a Channel Quality Indicator (CQI), a second PMI, and a second Rank Indicator (RI) based on the beamformed CSI-RS to the base station,
wherein, when the information further comprises a first RI, a value of the first RI is determined as only a value belonging to a previously determined set, and
wherein whether or not the first RI is reported is determined depending on a maximum number of layers supported by the UE.
2. The method of claim 1 , wherein when the maximum number of layers supported by the UE is 2 layers, the first RI is not reported to the base station.
3. The method of claim 1 , wherein when the maximum number of layers supported by the UE exceeds 2 layers, the first RI is reported to the base station at 1-bit.
4. The method of claim 3 , wherein when the maximum number of layers supported by the UE exceeds 2 layers, the first RI is determined as a value belonging to a set {1, 3}.
5. The method of claim 1 , wherein a set of precoding matrixes is determined by the first PMI selected in a previously determined codebook, and the beamformed CSI-RS is applied to a precoding matrix belonging to the set of precoding matrixes.
6. The method of claim 5 , wherein the first PMI is selected in a codebook for an antenna port or some antenna ports of one dimension in a 2-dimensional antenna port array of the base station.
7. The method of claim 5 , wherein the first PMI is selected in a codebook without co-phasing.
8. The method of claim 5 , wherein the first PMI is selected in a codebook composed of only precoding matrixes for forming an orthogonal beam.
9. The method of claim 8 , wherein a precoding matrix corresponding to the number of reported RIs is selected in the codebook to constitute the set of precoding matrixes.
10. The method of claim 9 , wherein a precoding matrix for an antenna port, that is not mapped to the set of precoding matrixes in an antenna port array of the base station, is derived by a linear combination of precoding matrixes belonging to the set of precoding matrixes.
11. The method of claim 9 , wherein a precoding matrix for an antenna port, that is not mapped to the set of precoding matrixes in an antenna port array of the base station, is determined as one of precoding matrixes belonging to the set of precoding matrixes.
12. The method of claim 5 , wherein an oversampling factor for configuring the codebook is limited to a smaller value among oversampling factors for antenna ports of each dimension in a 2-dimensional antenna port of the base station.
13. The method of claim 5 , wherein a spacing between sets of the precoding matrixes in the codebook is limited to an exponentiation power of 2.
14. A User Equipment (UE) for reporting channel state information (CSI) in a multi-antenna wireless communication system, the UE comprising:
a Radio Frequency (RF) unit for transmitting and receiving a radio signal; and
a processor for controlling the RF unit,
wherein the processor is configured to:
receive, from a base station, configuration information for single CSI reporting in which a non-precoded CSI-RS based CSI reporting and a beamformed CSI-RS based CSI reporting are combined;
report information derived based on the non-precoded CSI-RS to the base station,
wherein the information comprises a first Precoding Matrix Indicator (PMI); and
report a Channel Quality Indicator (CQI), a second PMI, and a second Rank Indicator (RI) based on the beamformed CSI-RS to the base station,
wherein, when the information further comprises a first RI, a value of the first RI is determined as only a value belonging to a previously determined set, and
wherein whether or not the first RI is reported is determined depending on a maximum number of layers supported by the UE.