METHOD FOR MAPPING HYBRID ARQ INDICATOR CHANNEL
The present invention relates to a method for mapping a hybrid ARQ indicator channel, which is transmitted to a downlink in a wireless communication system, to a frequency and a time resource.
1 . A method of mapping a hybrid Automatic Repeat reQuest (ARQ) indication channel based on a resource element unit, the method comprising:
setting, in a data area through which downlink data is transmitted, resource blocks where an Enhanced Physical Downlink Control CHannel (E-PDCCH) is set;
determining an index of a resource element group through which the hybrid ARQ indication channel is transmitted, based on the total number of available resource element groups of an E-PDCCH in the set resource blocks; and
mapping the hybrid ARQ indication channel to a resource element, based on the determined index.
2 . The method as claimed in claim 1 , wherein the resource element group is located in a predetermined Orthogonal Frequency Division Multiplexing (OFDM) symbol.
3 . The method as claimed in claim 2 , wherein, when a plurality of OFDM symbols, where the resource element group is located, exists, and the number of resource element groups located in each OFDM symbol is different from each other, determining the index comprises:
determining the index of the resource element group, based on a ratio of the number of resource element groups available in a symbol in which the hybrid ARQ indication channel is transmitted and the number of resource element groups available in a symbol in which a first resource element group is transmitted.
4 . The method as claimed in claim 2 , wherein determining the index comprises:
determining the index of the resource element group (REG) based on the following equation:
n
_
i
=
{
(
⌊
N
ID
cell
·
n
l
i
′
/
n
l
0
i
′
⌋
+
m
′
)
mod
n
l
i
′
i
=
0
(
⌊
N
ID
cell
·
n
l
i
′
/
n
l
0
i
′
⌋
+
m
′
+
⌊
n
l
i
′
/
3
⌋
)
mod
n
l
i
′
i
=
1
(
⌊
N
ID
cell
·
n
l
i
′
/
n
l
0
i
′
⌋
+
m
′
+
⌊
2
n
l
i
′
/
3
⌋
)
mod
n
l
i
′
i
=
2
,
wherein n i denotes an index of a resource element group through which each hybrid ARQ indication channel is transmitted, N ID cell ID denotes a cell ID, m′ denotes an index of each hybrid ARQ indication channel group, and n l′ i denotes the number of REGs usable for Enhanced Physical Hybrid ARQ Indicator CHannel (E-PHICH) transmission in an OFDM symbol l′ i , which is obtained through a product of the number of resource blocks to which an E-PDCCH is set, and 2 or 3.
5 . The method as claimed in claim 1 , wherein the resource element group is located in an entire extended control channel, excluding a resource to which a reference signal is set.
6 . The method as claimed in claim 5 , wherein determining the index comprises:
determining the index of the resource element group (REG) based on the following Equation:
n
_
i
=
{
n
′
mod
N
E
-
PHICH
REG
i
=
0
(
n
′
+
⌊
N
E
-
PHICH
REG
/
3
⌋
)
mod
N
E
-
PHICH
REG
i
=
1
(
n
′
+
2
·
⌊
N
E
-
PHICH
REG
/
3
⌋
)
mod
N
E
-
PHICH
REG
i
=
2
n
′
=
N
ID
cell
+
n
,
wherein n i denotes an index of a resource element group through which each hybrid ARQ indication channel is transmitted, N E-PHICH REG denotes the total number of available resource element groups of the E-PDCCH in the set resource blocks, N ID cell denotes a cell ID, and n denotes an index of each hybrid ARQ indication channel group.
7 . The method as claimed in claim 1 , wherein an index of each resource element group included in an identical hybrid ARQ indication channel group is distributed, being spaced apart at regular intervals.
8 . The method as claimed in claim 1 , wherein an index of each resource element group included in an identical hybrid ARQ indication channel group is contiguously distributed.
9 . The method as claimed in claim 6 , wherein the total number of available resource element groups of the E-PDCCH in the set resource blocks is determined based on a Cell-specific Reference Signal (CRS) antenna configuration, a Demodulation Reference Signal (DM-RS) and Channel State Information Reference Signal (CSI-RS) setting, a normal Cyclic Prefix (CP) or extended CP, and a control area.