Method for reporting channel state information and device using same
Provided are a method for reporting channel state information (CSI) and a device using the same. The device determines a CSI payload size in a CSI triggering subframe on which a CSI report is triggered. The device selects one of a plurality of physical uplink control channel (PUCCH) formats according to the CSI payload size.
1. A method for reporting channel state infatuation (CSI) in a wireless communication system, the method comprising:
receiving, by a wireless device, a configuration for a first physical uplink control channel (PUCCH) format and a second PUCCH format, the configuration including information regarding a first number of resource blocks (RBs) allocated to the second PUCCH format and a second number of RBs allocated to the second PUCCH format, the first number of RBs being smaller than the second number of RBs;
determining, by the wireless device, a payload size of at least one periodic CSI in a CSI triggering subframe in which the at least one periodic CSI is to be transmitted;
selecting, by the wireless device, one of the first PUCCH format and the second PUCCH format based on the payload size of the at least one periodic CSI report and a number of serving cells related to the at least one periodic CSI report; and
transmitting, by the wireless device, the at least one periodic CSI report through the selected PUCCH format in the CSI triggering subframe.
2. The method of claim 1 , wherein the CSI triggering subframe includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols, and
wherein the second PUCCH format uses two OFDM symbols for a demodulation reference signal (DM RS) among the plurality of OFDM symbols in the CSI triggering subframe.
3. The method of claim 2 , wherein the two OFDM symbols for the DM RS are a fourth OFDM symbol and an eleventh OFDM symbol of the plurality of OFDM symbols in the CSI triggering subframe.
4. The method of claim 1 , wherein the payload size of the second PUCCH format increases as the number of RBs allocated to the second PUCCH format increases.
5. The method of claim 1 , wherein one RB includes 12 subcarriers.
6. A device for reporting channel state information (CSI) in a wireless communication system, the device comprising:
a transceiver configured to transmit and receive a radio signal; and
a processor operatively coupled to the transceiver and configured to:
control the transceiver to receive a configuration for a first physical uplink control channel (PUCCH) format and a second PUCCH format, the configuration including information regarding a first number of resource blocks (RBs) allocated to the second PUCCH format and a second number of RBs allocated to the second PUCCH format, the first number of RBs being smaller than the second number of RBs;
determine a payload size of at least one periodic CSI report in a CSI triggering subframe in which the at least one periodic CSI report is to be transmitted;
select one of the first PUCCH format and the second PUCCH format based on the payload size of the at least one periodic CSI report and a number of serving cells related to the at least one periodic CSI report; and
control the transceiver to transmit the at least one periodic CSI report through the selected PUCCH format in the CSI triggering subframe.
7. The device of claim 6 , wherein the CSI triggering subframe includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols, and
wherein the second PUCCH format uses two OFDM symbols for a demodulation reference signal (DM RS) among the plurality of OFDM symbols in the CSI triggering subframe.
8. The device of claim 7 , wherein the two OFDM symbols for the DM RS are a fourth OFDM symbol and an eleventh OFDM symbol of the plurality of OFDM symbols in the CSI triggering subframe.
9. The device of claim 6 , wherein the payload size of the second PUCCH format increases as the number of RBs allocated to the extended PUCCH format increases.
10. The device of claim 6 , wherein one RB includes 12 subcarriers.
11. The method of claim 1 , wherein:
if there is only one periodic CSI report for one serving cell, the first PUCCH format is selected,
if there are periodic CSI reports for more than one serving cell and the payload size of the periodic CSI reports is equal to or less than the payload size of the second PUCCH format with the first number of RBs, the second PUCCH format with the first number of RBs is selected, and
if there are periodic CSI reports for more than one serving cell and the payload size of the periodic CSI reports is greater than the payload size of the second PUCCH format with the first number of RBs, the second PUCCH format with the second number of RBs is selected.
12. The device of claim 6 , wherein:
if there is only one periodic CSI report for one serving cell, the first PUCCH format is selected,
if there are periodic CSI reports for more than one serving cell and the payload size of the periodic CSI reports is equal to or less than the payload size of the second PUCCH format with the first number of RBs, the second PUCCH format with the first number of RBs is selected, and
if there are periodic CSI reports for more than one serving cell and the payload size of the periodic CSI reports is greater than the payload size of the second PUCCH format with the first number of RBs, the second PUCCH format with the second number of RBs is selected.