Method for transmitting channel state information in wireless access system and terminal therefor
Disclosed is a method for transmitting channel state information (CSI) in a wireless access system supporting carrier aggregation/multiple cells and a terminal therefor. Specifically, the method comprises the steps of: if a collision occurs between starting points of periodic CSI reports for first and second cells, calculating the number of resource elements using the biggest bit size among CSI bit sizes for first and second cells; adjusting the bit of the CSI with the highest priority among the CSIs of the first and second cells to match the biggest bit size; transmitting, to the base station, the adjusted bits of the CSI with the highest priority, which have been mapped to the calculated resource element.
1. A method of transmitting a channel state information (CSI) in a wireless access system supporting multiple cells, the method comprising:
calculating a number of resource elements (REs) using a maximum bit size among a bit size of the CSI for a first cell and a bit size of the CSI for a second cell, when a timing of a periodic CSI report for the first cell and a timing of a periodic CSI report for the second cell collide with each other;
adjusting bits of the CSI having a higher priority between the CSI for the first cell and the CSI for the second cell to match the maximum bit size; and
transmitting the adjusted bits of the CSI having the higher priority to a base station in a manner of mapping the adjusted bits to the calculated REs,
wherein the calculating the number of the REs includes calculating a number (Q′) of the REs by a formula,
wherein the formula is represented as follows:
Q
′
=
min
(
⌈
(
O
+
L
)
·
M
sc
PUSCH
-
initial
·
N
symb
PUSCH
-
initial
·
β
offset
PUSCH
∑
r
=
0
C
(
x
)
-
1
K
r
(
x
)
⌉
,
M
sc
PUSCH
·
N
symb
PUSCH
-
Q
RI
Q
m
)
,
〈
Formula
〉
and
wherein O indicates a bit number of the CSI, L indicates a cyclic redundancy check (CRC) bit number, β offset PUSCH is determined depending on a number of transmitted codewords for a corresponding uplink cell to consider an signal to noise ratio (SNR) difference between data and uplink control information (UCI), M sc PUSCH represents a bandwidth assigned for a physical uplink shared channel (PUSCH) transmission in a current subframe for a transport block as a subcarrier, N symb PUSCH indicates a number of single-carrier frequency-division multiple access (SC-FDMA) symbols in a subframe in which a current PUSCH is transmitted, N symb PUSCH-initial indicates a number of SC-FDMA symbols per subframe for an initial PUSCH transmission for a same transport block, M sc PUSCH-initial indicates a number of subcarriers, x in K r (x) indicates an index of a transport block having a highest modulation and coding scheme (MCS) designated by a UL grant, Q m is a modulation order of a given transport block, and Q RI is a number of coded bits for the CSI.
2. The method of claim 1 , the adjusting comprising:
adjusting the bits of the CSI having the higher priority to match the maximum bit size in a manner of padding bits amounting to a difference from the maximum bit size before and after the bits of the CSI having the higher priority.
3. The method of claim 1 , the adjusting comprising:
adjusting the bits of the CSI having the higher priority to match the maximum bit size in a manner of copying a portion of the bits of the CSI having the higher priority by a difference between the bits of the CSI having the higher priority and the maximum bit size and then adding the copied portion to the bits of the CSI having the higher priority.
4. The method of claim 1 , the transmitting comprising:
transmitting the CSI having the higher priority on the PUSCH or a physical uplink control channel (PUCCH).
5. The method of claim 1 , wherein the priority is determined depending on which information selected from the group consisting of a channel quality indication (CQI), a precoding matrix indication (PMI), a rank indication (RI) and a precoder type indication (PTI) is included in the periodic CSI report.
6. A user equipment for transmitting a channel state information (CSI) in a wireless access system supporting multiple cells, the user equipment comprising:
a transceiver configured to transceive a wireless signal; and
a processor which is configured to:
calculate a number of resource elements (REs) using a maximum bit size among a bit size of the CSI for a first cell and a bit size of the CSI for a second cell, when a timing of a periodic CSI report for the first cell and a timing of a periodic CSI report for the second cell collide with each other,
adjust bits of the CSI having a higher priority between the CSI for the first cell and the CSI for the second cell to match the maximum bit size, and
transmit the adjusted bits of the CSI having the higher priority to a base station in a manner of mapping the adjusted bits to the calculated REs,
wherein the processor calculates the number (Q′) of the REs by a formula,
wherein the formula is represented as follows:
Q
′
=
min
(
⌈
(
O
+
L
)
·
M
sc
PUSCH
-
initial
·
N
symb
PUSCH
-
initial
·
β
offset
PUSCH
∑
r
=
0
C
(
x
)
-
1
K
r
(
x
)
⌉
,
M
sc
PUSCH
·
N
symb
PUSCH
-
Q
RI
Q
m
)
,
〈
Formula
〉
and
wherein O indicates a bit number of the CSI, L indicates a cyclic redundancy check (CRC) bit number, β offset PUSCH is determined depending on a number of transmitted codewords for a corresponding uplink cell to consider an signal to noise ratio (SNR) difference between data and uplink control information (UCI), M sc PUSCH represents a bandwidth assigned for a physical uplink shared channel (PUSCH) transmission in a current subframe for a transport block as a subcarrier, N symb PUSCH indicates a number of single-carrier frequency-division multiple access (SC-FDMA) symbols in a subframe in which a current PUSCH is transmitted, N symb PUSCH-initial indicates a number of SC-FDMA symbols per subframe for an initial PUSCH transmission for a same transport block, M sc PUSCH-initial indicates a number of subcarriers, x in K r (x) indicates an index of a transport block having a highest modulation and coding scheme (MCS) designated by a UL grant, Q m is a modulation order of a given transport block, and Q RI is a number of coded bits for the CSI.
7. The user equipment of claim 6 , wherein the processor adjusts the bits of the CSI having the higher priority to match the maximum bit size in a manner of padding bits amounting to a difference from the maximum bit size before and after the bits of the CSI having the higher priority.
8. The user equipment of claim 6 , wherein the processor adjusts the bits of the CSI having the higher priority to match the maximum bit size in a manner of copying a portion of the bits of the CSI having the higher priority by a difference between the bits of the CSI having the higher priority and the maximum bit size and then adding the copied portion to the bits of the CSI having the higher priority.
9. The user equipment of claim 6 , wherein the processor transmits the CSI having the higher priority on the PUSCH or a physical uplink control channel (PUCCH).
10. The user equipment of claim 6 , wherein the priority is determined depending on which information selected from the group consisting of a channel quality indication (CQI), a precoding matrix indication (PMI), a rank indication (RI) and a precoder type indication (PTI) is included in the periodic CSI report.