Method for mapping physical hybrid automatic repeat request indicator channel
A method for mapping a physical hybrid automatic repeat request indicator channel (PHICH) is described. The method for mapping a PHICH includes determining an index of a resource element group transmitting a repetitive pattern of the PHICH, according to a ratio of the number of available resource element groups in a symbol in which the PHICH is transmitted and the number of available resource element groups in a first or second OFDM symbol, and mapping the PHICH to the symbol according to the determined index. In transmitting the PHICH, since efficient mapping is performed considering available resource elements varying with OFDM symbols, repetition of the PHICH does not generate interference between neighbor cell IDs and performance is improved.
1. A method for mapping a physical hybrid automatic repeat request indicator channel (PHICH) to one or more orthogonal frequency division multiplexing (OFDM) symbols, each OFDM symbol comprising one or more resource element groups, the method comprising:
determining indexes of one or more resource element groups in which the PHICH is transmitted; and
mapping the PHICH to the one or more OFDM symbols according to the determined indexes,
wherein the indexes are determined according to ratio n′ l′i /n′ 0 or ratio n′ l′i /n′ 1 in an OFDM symbol with index l′ i , wherein n′ l′i is the number of available resource element groups in the OFDM symbol with index l′ i , wherein n′ 0 is the number of available resource element groups in an OFDM symbol with index 0 in a sub-frame, wherein n′ 1 is the number of available resource element groups in an OFDM symbol with index 1 in the sub-frame, and
wherein the number of available resource element groups in a specific OFDM symbol is defined as the number of resource element groups to which a physical control format indicator channel (PCFICH) is not allocated among a total resource element groups in the specific OFDM symbol.
2. The method of claim 1 , wherein when the PHICH is mapped to two OFDM symbols in the sub-frame, the OFDM symbol index l′ i is defined as ( └ m′/2 ┘ +i+1)mod 2,
where i denotes an integer of 0 to 2 and m′ denotes an index related to a PHICH group in which the PHICH is included.
3. The method of claim 1 , wherein when the PHICH is mapped to one OFDM symbol in the sub-frame, the OFDM symbol index 1′ i is defined as 0,
where i denotes an integer of 0 to 2.
4. The method of claim 1 , wherein the PHICH is transmitted in units of a PHICH group including a plurality of PHICHs, and
wherein each of the resource element groups consists of two or four resource elements.
5. The method of claim 1 , wherein when the PHICH is mapped to one or three OFDM symbols in the sub-frame, the indexes of the resource element groups in which the PHICH is repeatedly transmitted three times are determined using the following equation:
n
_
i
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
n
l
i
1
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
2
n
l
i
1
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
where N ID cell denotes a cell ID, i denotes an index of the repetition of the PHICH, and m′ denotes an index related to a PHICH group in which the PHICH is included.
6. The method of claim 1 , wherein when the PHICH is mapped to two OFDM symbols in the sub-frame, the indexes of the resource element groups in which the PHICH is repeatedly transmitted three times are determined using the following equation:
n
_
i
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
2
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
where N ID cell denotes a cell ID, i denotes an index of the repetition of the PHICH, and m′ denotes an index related to a PHICH group in which the PHICH is included.
7. A base station for transmitting ACK/NACK (acknowledgement/negative acknowledgement) information through a physical hybrid automatic repeat request indicator channel (PHICH) mapped to one or more orthogonal frequency division multiplexing (OFDM) symbols,
each OFDM symbol comprising one or more resource element groups,
the base station comprising:
a processor configured to determine indexes of one or more resource element groups in which the PHICH is transmitted, map the PHICH to the one or more OFDM symbols according to the determined indexes, and transmit the ACK/NACK through the mapped PHICH,
wherein the indexes are determined according to ratio n′ l′i /n′ 0 or ratio n′ l′i /n′ 1 in an OFDM symbol with index l′ i ,
wherein n′ l′i is the number of available resource element groups in the OFDM symbol with index l′ i , wherein n′ 0 is the number of available resource element groups in an OFDM symbol with index 0 in a sub-frame, wherein n′ 1 is the number of available resource element groups in an OFDM symbol with index 1 in the sub-frame, and
wherein the number of available resource element groups in a specific OFDM symbol is defined as the number of resource element groups to which a physical control format indicator channel (PCFICH) is not allocated among a total resource element groups in the specific OFDM symbol.
8. The base station of claim 7 , wherein when the PHICH is mapped to two OFDM symbols in the sub-frame, the OFDM symbol index l′ i is defined as ( └ m′/2 ┘ +i+1)mod 2,
where i denotes an integer of 0 to 2 and m′ denotes an index related to a PHICH group in which the PHICH is included.
9. The base station of claim 7 , wherein when the PHICH is mapped to one OFDM symbol in the sub-frame, the OFDM symbol index l′ i is defined as 0,
where i denotes an integer of 0 to 2.
10. The base station of claim 7 , wherein the PHICH is transmitted in units of a PHICH group including a plurality of PHICHs, and
wherein each of the resource element groups consists of two or four resource elements.
11. The base station of claim 7 , wherein when the PHICH is mapped to one or three OFDM symbols in the sub-frame, the indexes of the resource element groups in which the PHICH is repeatedly transmitted three times are determined using the following equation:
n
_
i
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
n
l
i
1
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
2
n
l
i
1
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
where N ID cell denotes a cell ID, i denotes an index of the repetition of the PHICH, and m′ denotes an index related to a PHICH group in which the PHICH is included.
12. The base station of claim 7 , wherein when the PHICH is mapped to two OFDM symbols in the sub-frame, the indexes of the resource element groups in which the PHICH is repeatedly transmitted three times are determined using the following equation:
n
_
i
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
2
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
where N ID cell denotes a cell ID, i denotes an index of the repetition of the PHICH, and m′ denotes an index related to a PHICH group in which the PHICH is included.
13. A mobile station for receiving ACK/NACK (acknowledgement/negative acknowledgement) information through a physical hybrid automatic repeat request indicator channel (PHICH) mapped to one or more orthogonal frequency division multiplexing (OFDM) symbols,
each OFDM symbol comprising one or more resource element groups,
the mobile station comprising:
a processor configured to determine indexes of one or more resource element groups in which the PHICH is transmitted, decode the PHICH mapped to the one or more OFDM symbols according to the determined indexes, and receive the ACK/NACK through the mapped PHICH,
wherein the indexes are determined according to ratio n′ l′i /n′ 0 or ratio n′ l′i /n′ 1 in an OFDM symbol with index l′ i ,
wherein n′ l′i is the number of available resource element groups in the OFDM symbol with index l′ i , wherein n′ 0 is the number of available resource element groups in an OFDM symbol with index 0 in a sub-frame, wherein n′ 1 is the number of available resource element groups in an OFDM symbol with index 1 in the sub-frame, and
wherein the number of available resource element groups in a specific OFDM symbol is defined as the number of resource element groups to which a physical control format indicator channel (PCFICH) is not allocated among a total resource element groups in the specific OFDM symbol.
14. The mobile station of claim 13 , wherein when the PHICH is mapped to two OFDM symbols in the sub-frame, the OFDM symbol index l′ i is defined as ( └ m′/2 ┘ +i+1)mod 2,
where i denotes an integer of 0 to 2 and m′ denotes an index related to a PHICH group in which the PHICH is included.
15. The mobile station of claim 13 , wherein when the PHICH is mapped to one OFDM symbol in the sub-frame, the OFDM symbol index l′ i is defined as 0,
where i denotes an integer of 0 to 2.
16. The mobile station of claim 13 , wherein the PHICH is transmitted in units of a PHICH group including a plurality of PHICHs, and
wherein each of the resource element groups consists of two or four resource elements.
17. The mobile station of claim 13 , wherein when the PHICH is mapped to one or three OFDM symbols in the sub-frame, the indexes of the resource element groups in which the PHICH is repeatedly transmitted three times are determined using the following equation:
n
_
i
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
n
l
i
1
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
2
n
l
i
1
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
where N ID cell denotes a cell ID, i denotes an index of the repetition of the PHICH, and m′ denotes an index related to a PHICH group in which the PHICH is included.
18. The mobile station of claim 13 , wherein when the PHICH is mapped to two OFDM symbols in the sub-frame, the indexes of the resource element groups in which the PHICH is repeatedly transmitted three times are determined using the following equation:
n
_
i
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
2
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
where N ID cell denotes a cell ID, i denotes an index of the repetition of the PHICH, and m′ denotes an index related to a PHICH group in which the PHICH is included.