Uplink precoding method in 4-Tx system
A method for a user equipment to precode and transmit an uplink signal efficiently in a 4-antenna system and a method for a base station to receive the transmitted signal efficiently are disclosed. Four antennas of a user equipment can be grouped by a 2-antenna unit. In consideration of this antenna group, it is able to perform precoding using antenna selection/DFT matrix of the antenna group unit. Moreover, a rank-3 codebook can be configured to include a precoding matrix of a type in consideration of power balance per antenna and a precoding matrix including one non-zero component only in one row for maintaining a good CM property.
1. A method of transmitting a signal by a user equipment using 4 antennas, the method comprising:
obtaining transmission rank information;
generating a precoded signal by precoding layer signals using a specific precoding matrix that corresponds to the transmission rank information,
transmitting the generated precoded signal,
wherein the specific precoding matrix is selected from a 4-antenna codebook, the 4-antenna codebook including a first type precoding matrix defined as a 4-by-3 matrix type that includes 2 non-zero components in each row and 2 zero components in first and second columns for a rank of 3,
wherein a number of the precoded layer signals corresponds to the transmission rank information,
wherein the first type precoding matrix has a type resulting from multiplying
W
N
t
×
3
n
=
[
1
0
1
ⅇ
jθ
1
0
-
ⅇ
jθ
1
0
1
1
0
ⅇ
jθ
2
-
ⅇ
jθ
2
]
or
W
N
t
×
3
n
=
[
1
0
1
-
ⅇ
jθ
1
0
ⅇ
jθ
1
0
ⅇ
jθ
2
ⅇ
jθ
2
0
-
ⅇ
jθ
3
ⅇ
jθ
3
]
by a normalization coefficient,
wherein N t is 4, wherein θ 1 , θ 2 meet a condition of
θ
1
,
θ
2
∈
{
2
π
N
i
,
i
=
0
,
…
,
N
-
1
}
,
and
wherein N is set to 4 or 8.
2. The method of claim 1 , wherein the 4-antenna codebook further includes a second type precoding matrix defined as a 4-by-3 matrix type that includes one non-zero component in each row.
3. The method of claim 2 , wherein the second type precoding matrix has a type resulting from multiplying
W
N
t
×
3
n
=
[
1
0
0
0
1
0
0
0
1
0
0
ⅇ
jθ
]
by a normalization coefficient,
wherein Nt is 4,
wherein θ meets a condition of
θ
∈
{
2
π
N
i
,
i
=
0
,
…
,
N
-
1
}
,
and
wherein N is set to 4 or 8.
4. The method of claim 3 , wherein the second type precoding matrix has a type multiplied by either a coefficient for inter-antenna power normalization or inter-layer power normalization.
5. A method of receiving a signal at a base station using 4 antennas, the method comprising:
receiving a reception signal;
obtaining a transmission rank and precoding matrix identification information used for reception of signal transmission; and
performing reverse processing of precoding on the reception signal by selecting a specific precoding matrix that corresponds to the transmission rank and precoding matrix identification information from a 4-antenna codebook, the 4-antenna codebook including a first type precoding matrix defined as a 4-by-3 matrix type that includes 2 non-zero components in each row and 2 zero components in first and second columns for a rank of 3,
wherein the first type precoding matrix has a type resulting from multiplying
W
N
t
×
3
n
=
[
1
0
1
ⅇ
jθ
1
0
-
ⅇ
jθ
1
0
1
1
0
ⅇ
jθ
2
-
ⅇ
jθ
2
]
or
W
N
t
×
3
n
=
[
1
0
1
-
ⅇ
jθ
1
0
ⅇ
jθ
1
0
ⅇ
jθ
2
ⅇ
jθ
2
0
-
ⅇ
jθ
3
ⅇ
jθ
3
]
by a normalization coefficient,
wherein Nt is 4, wherein θ 1 ,θ 2 meet a condition of
θ
1
,
θ
2
∈
{
2
π
N
i
,
i
=
0
,
…
,
N
-
1
}
,
and
wherein N is set to 4 or 8.
6. The method of claim 5 , wherein the 4-antenna codebook further includes a second type precoding matrix defined as a 4-by-3 matrix type that includes one non-zero component in each row.
7. A user equipment comprising:
a memory configured to store a 4-antenna codebook that includes a first type precoding matrix defined as a 4-by-3 matrix type that includes 2 non-zero components in each row and 2 zero components in first and second columns for a rank of 3;
a precoder configured to generate a precoded signal by precoding layer signals using a specific precoding matrix that corresponds to a transmission rank; and
four antennas configured to transmit the precoded signal,
wherein a number of the precoded layer signals corresponds to the transmission rank,
wherein the specific precoding matrix is selected from the 4-antenna codebook
wherein the first type precoding matrix has a type resulting from multiplying
W
N
t
×
3
n
=
[
1
0
1
ⅇ
jθ
1
0
-
ⅇ
jθ
1
0
1
1
0
ⅇ
jθ
2
-
ⅇ
jθ
2
]
or
W
N
t
×
3
n
=
[
1
0
1
-
ⅇ
jθ
1
0
ⅇ
jθ
1
0
ⅇ
jθ
2
ⅇ
jθ
2
0
-
ⅇ
jθ
3
ⅇ
jθ
3
]
by a normalization coefficient,
wherein Nt is 4, wherein θ 1 ,θ 2 meet a condition of
θ
1
,
θ
2
∈
{
2
π
N
i
,
i
=
0
,
…
,
N
-
1
}
,
and
wherein N is set to 4 or 8.
8. The user equipment of claim 7 , wherein the 4-antenna codebook further includes a second type precoding matrix defined as a 4-by-3 matrix type including one non-zero component in each row.
9. A base station comprising:
an antenna configured to receive a reception signal;
a memory configured to store a 4-antenna codebook that includes a first type precoding matrix defined as a 4-by-3 matrix type that includes 2 non-zero components in each row and 2 zero components in first and second columns for a rank of 3; and
a precoder configured to perform reverse processing of precoding on the reception signal by selecting at least a precoding matrix that corresponds to a transmission rank or precoding matrix identification information from the stored 4-antenna codebook,
wherein the first type precoding matrix has a type resulting from multiplying
W
N
t
×
3
n
=
[
1
0
1
ⅇ
jθ
1
0
-
ⅇ
jθ
1
0
1
1
0
ⅇ
jθ
2
-
ⅇ
jθ
2
]
or
W
N
t
×
3
n
=
[
1
0
1
-
ⅇ
jθ
1
0
ⅇ
jθ
1
0
ⅇ
jθ
2
ⅇ
jθ
2
0
-
ⅇ
jθ
3
ⅇ
jθ
3
]
by a normalization coefficient,
wherein Nt is 4, wherein θ 1 ,θ 2 meet a condition of
θ
1
,
θ
2
∈
{
2
π
N
i
,
i
=
0
,
…
,
N
-
1
}
,
and
wherein N is set to 4 or 8.
10. The base station of claim 9 , wherein the 4-antenna codebook further includes a second type precoding matrix defined as a 4-by-3 matrix type that includes one non-zero component in each row.