PHICH transmission in time division duplex systems
A method is provided for communication in a wireless telecommunication system. The method comprises multiplexing, by a network element, at least one symbol of a PHICH onto at least one resource element of a PCFICH.
1. A method for communication in a wireless telecommunication system, the method comprising:
multiplexing, by a network element, at least one symbol of a physical HARQ (hybrid automatic repeat request) indicator channel (PHICH) onto at least one resource element of a physical control format indicator channel (PCFICH), wherein the at least one resource element is shared by the PHICH and the PCFICH,
wherein extra PHICH resources are created in a control region of a subframe by multiplexing the at least one PHICH symbol onto the at least one PCFICH resource element such that up to six acknowledgement/negative acknowledgement (ACK/NACK) signals can be carried using the extra PHICH resources, wherein the at least one PHICH symbol is orthogonal to at least one PCFICH symbol.
2. The method of claim 1 , wherein the at least one PHICH symbol is mapped to a physical uplink shared channel (PUSCH) by the following equation:
n PHICH seq =( I PRB _ RA lowest _ index +n DMRS )mod N
where N is 6 for a normal cyclic prefix and N is 2 for an extended cyclic prefix.
3. The method of claim 2 , wherein explicit signaling is used to define the mapping between the PUSCH and the at least one PHICH symbol.
4. The method of claim 1 , wherein channel coding for the PHICH generates a total of 16 coded bits with four repeated sections, each section having a length of four for normal cyclic prefix mode and a length of two for extended cyclic prefix mode, and wherein each PHICH acknowledgement/negative acknowledgement (ACK/NACK) bit is repeated 16 times and then binary phase shift keying (BPSK) modulated, scrambled, and cover-coded with the PHICH orthogonal sequence.
5. The method of claim 4 , wherein, for a given PHICH sequence, the resulting symbols are given by:
d
(
PHICH
)
(
k
)
=
{
1
2
w
k
(
seqldx
)
(
1
-
2
·
b
(
HI
,
seqldx
)
(
k
)
)
·
(
1
-
2
·
b
(
CFI
)
(
2
k
)
)
·
(
1
-
2
·
c
(
2
k
)
)
,
if
w
k
(
seqldx
)
is
real
1
2
w
k
(
seqldx
)
(
1
-
2
·
b
(
HI
,
seqldx
)
(
k
)
)
·
(
1
-
2
·
b
(
CFI
)
(
2
k
+
1
)
)
·
(
1
-
2
·
c
(
2
k
+
1
)
)
,
otherwise
where w k (seqIdx) is the k-th element in the four-times-repeated orthogonal sequence with sequence index seqIdx; b (HI,seqIdx) (k) is a HI bit (for ACK/NACK) associated with sequence index seqIdx; b (CFT) (i)∈{0,1} for i=2k and 2k+1 denotes the i-th bit in a Control Format Indicator (CFI) sequence for a given CFI value; and c(k) is a cell-specific scrambling sequence that is the same as that used for PCFICH generation.
6. The method of claim 4 , wherein the four-times-repeated orthogonal sequence is formed by repeating the complex orthogonal Walsh sequence [w(0) . . . w(N SF PHICH −1)] four times and concatenating the sequences together.
7. The method of claim 1 , wherein power on the PCFICH is increased to overcome performance degradation caused by the multiplexing of the PHICH and the PCFICH.
8. The method of claim 1 , wherein the network element includes, in an uplink grant to a transmitting entity, a new data indicator capable of assuming one of two different values, wherein the network element changes the value of the new data indicator when the network element requests a new data transmission from the transmitting entity, and wherein the network element does not change the value of the new data indicator when the network element requests a retransmission from the transmitting entity.
9. The method of claim 1 , further comprising the network element including a new data indicator in an uplink grant to a transmitting entity when the number of PHICH bits to be transmitted is greater than the number of PHICH bits that can be multiplexed onto the PCFICH.
10. The method of claim 1 , wherein the network element is a primary cell in a wireless telecommunication system that employs carrier aggregation.
11. A network element in a wireless telecommunication system, the network element comprising:
a processor configured such that the network element multiplexes at least one symbol of a physical HARQ (hybrid automatic repeat request) indicator channel (PHICH) onto at least one resource element of a physical control format indicator channel (PCFICH), wherein the at least one resource element is shared by the PHICH and the PCFICH,
wherein extra PHICH resources are created in a control region of a subframe by multiplexing the at least one PHICH symbol onto the at least one PCFICH resource element such that up to six acknowledgement/negative acknowledgement (ACK/NACK) signals can be carried using the extra PHICH resources, wherein the at least one PHICH symbol is orthogonal to at least one PCFICH symbol.
12. The network element of claim 11 , wherein the at least one PHICH symbol is mapped to a physical uplink shared channel (PUSCH) by the following equation:
n PHICH seq =( I PRB _ RA lowest _ index +n DMRS )mod N
where N is 6 for a normal cyclic prefix and 2 for an extended cyclic prefix.
13. The network element of claim 12 , wherein explicit signaling is used to define the mapping between the PUSCH and the at least one PHICH symbol.
14. The network element of claim 11 , wherein channel coding for the PHICH generates a total of 16 coded bits with four repeated sections, each section having a length of four for normal cyclic prefix mode and a length of two for extended cyclic prefix mode, and wherein each PHICH acknowledgement/negative acknowledgement (ACK/NACK) bit is repeated 16 times and then binary phase shift keying (BPSK) modulated, scrambled, and cover-coded with the PHICH orthogonal sequence.
15. The network element of claim 14 , wherein, for a given PHICH sequence, the resulting symbols are given by:
d
(
PHICH
)
(
k
)
=
{
1
2
w
k
(
seqldx
)
(
1
-
2
·
b
(
HI
,
seqldx
)
(
k
)
)
·
(
1
-
2
·
b
(
CFI
)
(
2
k
)
)
·
(
1
-
2
·
c
(
2
k
)
)
,
if
w
k
(
seqldx
)
is
real
1
2
w
k
(
seqldx
)
(
1
-
2
·
b
(
HI
,
seqldx
)
(
k
)
)
·
(
1
-
2
·
b
(
CFI
)
(
2
k
+
1
)
)
·
(
1
-
2
·
c
(
2
k
+
1
)
)
,
otherwise
where w k (seqIdx) is the k-th element in the four-times-repeated orthogonal sequence with sequence index seqIdx; b (HI,seqIdx) (k) is a HI bit (for ACK/NACK) associated with sequence index seqIdx; b (CFT) (i)∈{0,1} for i=2k and 2k+1 denotes the i-th bit in a Control Format Indicator (CFI) sequence for a given CFI value; and c(k) is a cell-specific scrambling sequence that is the same as that used for PCFICH generation.
16. The network element of claim 14 , wherein the four-times-repeated orthogonal sequence is formed by repeating the complex orthogonal Walsh sequence [w(0) . . . w(N SF PHICH −1)] four times and concatenating the sequences together.
17. The network element of claim 11 , wherein power on the PCFICH is increased to overcome performance degradation caused by the multiplexing of the PHICH and the PCFICH.
18. The network element of claim 11 , wherein the network element includes, in an uplink grant to a transmitting entity, a new data indicator capable of assuming one of two different values, wherein the network element changes the value of the new data indicator when the network element requests a new data transmission from the transmitting entity, and wherein the network element does not change the value of the new data indicator when the network element requests a retransmission from the transmitting entity.
19. The network element of claim 11 , wherein the network element includes a new data indicator in an uplink grant to a transmitting entity when the number of PHICH bits to be transmitted is greater than the number of PHICH bits that can be multiplexed onto the PCFICH.
20. The network element of claim 11 , wherein the network element is a primary cell in a wireless telecommunication system that employs carrier aggregation.