Method for feeding back antenna shuffling information in a multiple-input multiple-output system using a multiple space-time block coding technique
View Patent ↗In a method for feeding back combination information of transmitted signals in a multiple-input multiple-output (MIMO) system using a multiple space-time block coding technique, mean square error values are computed in relation to the combination information pieces of the transmitted signals. An index of a combination having a minimum mean square error value from among the mean square error values is fed back.
1. A method for feeding back antenna shuffling information of transmitted signals in a multiple-input multiple-output (MIMO) system, comprising the steps of:
receiving, through two reception antennas, signals transmitted from four transmit antennas;
computing mean square error values of the received signals in relation to antenna shuffling information indices of the transmitted signals; and
feeding back an index of an antenna shuffling having a minimum mean square error value from among the mean square error values,
wherein the index of the antenna shuffling is determined using channel matrix S, where
S
=
[
h
1
,
1
h
1
,
2
h
1
,
3
h
1
,
4
h
1
,
2
*
-
h
1
,
1
*
h
1
,
4
*
-
h
1
,
3
*
h
2
,
1
h
2
,
2
h
2
,
3
h
2
,
4
h
2
,
2
*
-
h
2
,
1
*
h
2
,
4
*
-
h
2
,
3
*
]
,
and
h i,j is a channel gain value between a j-th Tx antenna and an i-th Rx antenna.
2. The method of claim 1 , wherein the mean square error values are computed in relation to a predetermined number of antenna shuffling information indices from among the antenna shuffling information indices.
3. The method of claim 1 , wherein the number of antenna shuffling information indices are determined based on a number of transmit antennas.
4. The method of claim 1 , wherein the minimum mean square error value associated with the antenna shuffling information indices of the transmitted signals is determined by:
λ
q
,
l
=
ZF
min
[
diag
{
(
S
q
,
k
_
l
H
S
q
,
k
_
l
)
-
1
}
]
=
MMSE
min
[
diag
{
(
S
q
,
k
_
l
H
S
q
,
k
_
l
+
σ
2
I
)
-
1
}
]
,
q
∈
{
1
,
2
,
…
,
Q
}
,
l
∈
{
0
,
1
,
…
,
L
-
1
}
where diag denotes a diagonal matrix, S denotes the channel matrix, L=T/B, L denotes the number of layers, T denotes the number of transmit antennas, B denotes an STBC block size, Q denotes the number of combinations of the transmitted signals, H denotes a Hermitian transpose, ZF denotes zero forcing, and MMSE denotes a minimum mean square error.
5. The method of claim 1 , wherein the index of the antenna shuffling having the minimum mean square error value from among the computed mean square error values is determined by:
select
antenna
shuffling
index
q
s
.
t
.
min
q
(
min
[
diag
{
(
S
q
,
k
_
0
H
S
q
,
k
_
0
)
-
1
}
]
)
,
(
ZF
)
∀
q
min
q
(
min
[
diag
{
(
S
q
,
k
_
0
H
S
q
,
k
_
0
+
σ
2
I
)
-
1
}
]
)
,
(
MMSE
)
∀
q
where diag denotes a diagonal matrix, S denotes the channel matrix, ZF denotes zero forcing, and MMSE denotes a minimum mean square error.
6. The method of claim 1 , wherein the index of the antenna shuffling having the minimum mean square error value from among the computed mean square error values is determined by:
select
antenna
shuffling
index
q
s
.
t
.
min
q
(
max
λ
l
[
min
[
diag
{
(
S
q
,
k
_
l
H
S
q
,
k
_
l
)
-
1
}
]
]
)
,
(
ZF
)
∀
q
,
∀
l
min
q
(
max
λ
l
[
min
[
diag
{
(
S
q
,
k
_
l
H
S
q
,
k
_
l
+
σ
2
I
)
-
1
}
]
]
)
,
(
MMSE
)
∀
q
,
∀
l
where diag denotes a diagonal matrix, S denotes the channel matrix, ZF denotes zero forcing, and MMSE denotes a minimum mean square error.
7. The method of claim 6 , wherein q denotes a value stored in advance in transmitting and receiving terminals, and denotes an index value of antenna shuffling information of the transmitted signals.
8. The method of claim 1 , wherein an index of combination information of the transmitted signals is determined by:
select
antenna
shuffling
index
q
s
.
t
.
min
q
(
abs
[
det
{
(
H
q
,
1
)
+
det
{
(
H
q
,
2
)
}
]
)
,
(
ZF
)
∀
q
where abs denotes an absolute value, det denotes determinant, and ZF denotes zero forcing.
9. An apparatus for transmitting signals in a multiple-input multiple-output (MIMO) system, comprising:
a shuffling unit for receiving an antenna shuffling index of transmitted signals from a receiving terminal and combining signals to be transmitted according to the antenna shuffling index and assigning the combined signals to antennas; and
a MIMO detector for computing mean square error values in relation to antenna shuffling information indices of the transmitted signals, and feeding back an index of an antenna shuffling having a minimum mean square error value from among the mean square error values
wherein the index of the antenna shuffling is determined using channel matrix S, where
S
=
[
h
1
,
1
h
1
,
2
h
1
,
3
h
1
,
4
h
1
,
2
*
-
h
1
,
1
*
h
1
,
4
*
-
h
1
,
3
*
h
2
,
1
h
2
,
2
h
2
,
3
h
2
,
4
h
2
,
2
*
-
h
2
,
1
*
h
2
,
4
*
-
h
2
,
3
*
]
,
and
h i,j is a channel gain value between a j-th Tx antenna and an i-th Rx antenna.
10. The apparatus of claim 9 , further comprising a memory for storing combination information of the transmitted signals corresponding to the antenna shuffling index in advance in a transmitting terminal.
11. The apparatus of claim 9 , wherein the minimum mean square error value associated with the antenna shuffling information indices of the transmitted signals is determined by:
λ
q
,
l
=
ZF
min
[
diag
{
(
S
q
,
k
_
l
H
S
q
,
k
_
l
)
-
1
}
]
=
MMSE
min
[
diag
{
(
S
q
,
k
_
l
H
S
q
,
k
_
l
+
σ
2
I
)
-
1
}
]
,
q
∈
{
1
,
2
,
…
,
Q
}
,
l
∈
{
0
,
1
,
…
,
L
-
1
}
where diag denotes a diagonal matrix, S denotes the channel matrix, L=T/B, L denotes the number of layers, T denotes the number of transmit antennas, B denotes an STBC block size, Q denotes the number of combinations of the transmitted signals, H denotes a Hermitian transpose, ZF denotes zero forcing, and MMSE denotes a minimum mean square error.
12. The apparatus of claim 9 , wherein the index of the antenna shuffling having the minimum mean square error value from among the computed mean square error values is determined by:
select
antenna
shuffling
index
q
s
.
t
.
min
q
(
min
[
diag
{
(
S
q
,
k
_
0
H
S
q
,
k
_
0
)
-
1
}
]
)
,
(
ZF
)
∀
q
min
q
(
min
[
diag
{
(
S
q
,
k
_
0
H
S
q
,
k
_
0
+
σ
2
I
)
-
1
}
]
)
,
(
MMSE
)
∀
q
where diag denotes a diagonal matrix, S denotes the channel matrix, ZF denotes zero forcing, MMSE denotes a minimum mean square error, and q denotes the number of combinations of the transmitted signals.
13. The apparatus of claim 9 , wherein the index of the antenna shuffling having the minimum mean square error value from among the computed mean square error values is determined by:
select
antenna
shuffling
index
q
s
.
t
.
min
q
(
max
λ
l
[
min
[
diag
{
(
S
q
,
k
_
l
H
S
q
,
k
_
l
)
-
1
}
]
]
)
,
(
ZF
)
∀
q
,
∀
l
min
q
(
max
λ
l
[
min
[
diag
{
(
S
q
,
k
_
l
H
S
q
,
k
_
l
+
σ
2
I
)
-
1
}
]
]
)
,
(
MMSE
)
∀
q
,
∀
l
where diag denotes a diagonal matrix, S denotes the channel matrix, ZF denotes zero forcing, MMSE denotes a minimum mean square error, q denotes the number of combinations of the transmitted signals, and l denotes the number of layers determined by the number of transmit antennas and the number of the receive antennas.
14. The apparatus of claim 9 , wherein an index of antenna shuffling information of the transmitted signals is determined by:
select
antenna
shuffling
index
q
s
.
t
.
min
q
{
abs
[
det
(
H
q
,
1
)
+
det
(
H
q
,
2
)
]
}
,
(
ZF
)
∀
q
where abs denotes an absolute value, det denotes determinant, ZF denotes zero forcing, and q denotes the number of combinations of the transmitted signals.