# US 2018/0026697 A1 · Method and apparatus for transmitting channel state information in wireless communication system

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- Number: US 2018/0026697 A1
- Document ID: US20180026697A1
- Status: Published application
- Kind: A1
- Application number: 15/721,068
- Filed: 2017-09-29
- Published: 2018-01-25
- Earliest claimed: 2013-04-29
- Assignees: LG Electronics Inc.
- Applicants: LG Electronics Inc.
- Inventors: Hyungtae KIM; Kijun KIM; Hyunho LEE
- Web page: https://patentgrep.com/patent/US20180026697A1

## CPC

- H04B 7/0626: {Channel coefficients, e.g. channel state information [CSI]}
- H04B 7/0481: {using subset selection of codebooks}
- H04B 7/0482: {Adaptive codebooks}
- H04B 7/0486: {taking channel rank into account}
- H04B 7/063: {Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection}
- H04B 7/0632: {Channel quality parameters, e.g. channel quality indicator [CQI]}
- H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection}
- H04L 1/0026: {Transmission of channel quality indication}
- H04L 1/0027: {Scheduling of signalling, e.g. occurrence thereof}
- H04L 5/0057: {Physical resource allocation for CQI}
- H04L 25/03898: {codebook-based design (selection of codebook or precoding matrix for MIMO diversity systems H04B7/0456)}
- H04W 72/21: in the uplink direction of a wireless link, i.e. towards the network
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

The present invention relates to a wireless communication system. According to one embodiment of the present invention, a method for transmitting, by a terminal, channel state information (CSI) in a wireless communication system comprises the steps of: subsampling a code book for four antenna ports; and feeding back the CSI on the basis of the subsampled code book, wherein the CSI includes a rank indicator (RI) reported together with a precoding type indicator (PTI), and if the RI is greater than 2, the PTI is set to one.

## Claims

### Claim at position 1

1-14. (canceled)

### Claim 15

A method for transmitting a channel state information (CSI) by a user equipment (UE) in a wireless communication system, the method comprising:
determining a precoding type indicator (PTI) and a precoding matrix indicator (PMI) based on a rank indicator (RI); and
reporting the CSI including the PTI, PMI and the RI to a base station (BS);
wherein if the RI is greater than 2, the PTI is equal to 1 and the PMI is restricted to use 4 precoding matrices out of 16 precoding matrices in a codebook, and
wherein the 4 precoding matrices are as follows:
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and
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.

### Claim 16 (depends on 15)

The method according to claim 15, wherein the CSI is transmitted using a physical uplink control channel mode 2-1.

### Claim 17 (depends on 15)

The method according to claim 15, wherein a payload size for reporting the PMI is 2 bits.

### Claim 18 (depends on 15)

The method according to claim 15, wherein each of the 4 precoding matrices is a 4 by 4 matrix.

### Claim 19 (depends on 15)

The method according to claim 15, wherein when the RI is 3 or 4, a final PMI is determined as the PMI, and
wherein when the RI is 1 or 2, a final PMI is determined using the PMI and another PMI.

### Claim 20

A user equipment for transmitting a channel state information (CSI) in a wireless communication system, the user equipment comprising:
a radio frequency (RF) unit; and
a processor operably coupled with the RF unit and configured to:
determine a precoding type indicator (PTI) and a precoding matrix indicator (PMI) based on a rank indicator (RI); and
report the CSI including the PTI, PMI and the RI to a base station (BS);
wherein if the RI is greater than 2, the PTI is equal to 1 and the PMI is restricted to use 4 precoding matrices out of 16 precoding matrices in a codebook, and
wherein the 4 precoding matrices are as follows:
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0
=
1
2
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1
1
1
1
1
1
-
1
-
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]
,
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]
,
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1
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1
1
]
,
and
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10
=
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2
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-
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-
1
1
-
1
1
-
1
1
-
1
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1
1
1
1
1
1
]
.

### Claim 21 (depends on 20)

The user equipment according to claim 20, wherein the CSI is transmitted using a physical uplink control channel mode 2-1.

### Claim 22 (depends on 20)

The user equipment according to claim 20, wherein a payload size for reporting the PMI is 2 bits.

### Claim 23 (depends on 20)

The user equipment according to claim 20, wherein each of the 4 precoding matrices is a 4 by 4 matrix.

### Claim 24 (depends on 20)

The user equipment according to claim 20, wherein when the RI is 3 or 4, a final PMI is determined as the PMI, and
wherein when the RI is 1 or 2, a final PMI is determined using the PMI and another PMI.