Method of precoding with a codebook for a wireless system
View Patent ↗A quantized multi-rank beamforming scheme for multiple-antenna systems such as a multiple-input-multiple-output (MIMO) wireless downlink. User equipment (UE) estimates downlink channel and transmit power and determines rank and power allocations. A quantized beamforming matrix is then determined by the UE using successive beamforming. The UE also determines channel quality indices (CQI) which it feeds-back to the wireless downlink base station along with the index of the quantized beamforming matrix. The base station uses the CQI information to select a UE for scheduling of downlink transmission and the quantized beamforming matrix index received from the selected UE to beamform the downlink transmission to the UE. Base station overhead and is minimized while providing near-optimal performance given the constraints of a limited feed-back channel and computational complexity of the UE.
1. A transmitter used in a wireless communications system, the transmitter comprising:
a precoding unit to precode data with a precoding matrix selected from a codebook comprising matrices that are expressed as
V
=
[
v
1
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
v
2
]
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
Φ
(
v
1
2
)
HH
(
v
2
Φ
(
v
1
2
)
-
e
1
M
-
1
)
[
0
v
3
]
]
,
…
]
,
where the transmitter has M transmit antennas, e 1 N =[1, 0, . . . , 0] T εC N (N=M, M−1, . . . ), C N being N-dimensional complex space, v a denotes a column vector, v b a denotes the b th element of vector v a ,
Φ
(
v
b
a
)
=
v
b
a
||
v
b
a
||
,
and
HH
(
w
)
=
{
I
-
2
ww
H
||
w
||
2
if
w
≠
0
I
if
w
=
0
is the house-holder transformation of vector w; and
a transmission unit to transmit the precoded data to a receiver.
2. The transmitter as in claim 1 , wherein the transmitter comprises a base station and the receiver comprises a user equipment.
3. The transmitter as in claim 1 , wherein the transmission is downlink transmission.
4. The transmitter as in claim 1 , wherein v a is selected from a set V a where
V 1 ={v i 1 εC M } i=1 N 1 , V 2 ={e 1 M-1 }, V 3 ={e 1 M-2 }, . . . .
5. The transmitter as in claim 1 , wherein the number of transmit antennas is 2.
6. The transmitter as in claim 1 , wherein the number of transmit antennas is 4.
7. The transmitter as in claim 1 , wherein the precoding matrix is formed by selecting one or more columns of matrix V.
8. The transmitter as in claim 7 , wherein the number of selected columns to form the precoding matrix is less than the number of transmit antennas.
9. A receiver used in a wireless communications system, the receiver comprising:
a receiving unit to receive, from a transmitter, data precoded with a precoding matrix selected from a codebook comprising matrices that are expressed as
V
=
[
v
1
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
v
2
]
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
Φ
(
v
1
2
)
HH
(
v
2
Φ
(
v
1
2
)
-
e
1
M
-
1
)
[
0
v
3
]
]
,
…
]
,
where the transmitter has M transmit antennas, e 1 N =[1, 0, . . . , 0] T εC N (N=M, M−1, . . . ), C N being N-dimensional complex space, v a denotes a column vector, v b a denotes the b th element of vector v a ,
Φ
(
v
b
a
)
=
v
b
a
||
v
b
a
||
,
and
HH
(
w
)
=
{
I
-
2
ww
H
||
w
||
2
if
w
≠
0
I
if
w
=
0
is the house-holder transformation of vector w.
10. The receiver as in claim 9 , wherein the transmitter comprises a base station and the receiver comprises a user equipment.
11. The receiver as in claim 9 , wherein the reception is downlink reception.
12. The receiver as in claim 9 , wherein v a is selected from a set V a where
V 1 ={v i 1 εC M } i=1 N 1 , V 2 ={e 1 M-1 }, V 3 ={e 1 M-2 }, . . . .
13. The receiver as in claim 9 , wherein the number of transmit antennas is 2.
14. The receiver as in claim 9 , wherein the number of transmit antennas is 4.
15. The receiver as in claim 9 , wherein the precoding matrix is formed by selecting one or more columns of matrix V.
16. The receiver as in claim 15 , wherein the number of selected columns to form the precoding matrix is less than the number of transmit antennas.
17. A receiver used in a wireless communications system, the receiver comprising:
a feedback unit to provide feedback information for transmission in order for a transmitter to select a precoding matrix from a codebook comprising matrices that are expressed as
V
=
[
v
1
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
v
2
]
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
Φ
(
v
1
2
)
HH
(
v
2
Φ
(
v
1
2
)
-
e
1
M
-
1
)
[
0
v
3
]
]
,
…
]
,
where the transmitter has M transmit antennas, e 1 N =[1, 0, . . . , 0] T εC N (N=M, M−1, . . . ), C N being N-dimensional complex space, v a denotes a column vector, v b a denotes the b th element of vector v a ,
Φ
(
v
b
a
)
=
v
b
a
||
v
b
a
||
,
and
HH
(
w
)
=
{
I
-
2
ww
H
||
w
||
2
if
w
≠
0
I
if
w
=
0
is the house-holder transformation of vector w.
18. The receiver as in claim 17 , wherein the transmitter comprises a base station and the receiver comprises a user equipment.
19. The receiver as in claim 17 , wherein the transmission is downlink transmission.
20. The receiver as in claim 17 , wherein v a is selected from a set V a where
V 1 ={v i 1 εC M } i=1 N 1 , V 2 ={e 1 M-1 }, V 3 ={e i M-2 }, . . . .
21. The receiver as in claim 17 , wherein the number of transmit antennas is 2.
22. The receiver as in claim 17 , wherein the number of transmit antennas is 4.
23. The receiver as in claim 17 , wherein the precoding matrix is formed by selecting one or more columns of matrix V.
24. The receiver as in claim 23 , wherein the number of selected columns to form the precoding matrix is less than the number of transmit antennas.
25. The receiver as in claim 17 , wherein the feedback information includes at least one of a rank, a precoding matrix index, quantization power control, and a Signal to Interference and Noise Ratio (SINR).
26. A wireless communications system comprising:
a transmitter to precode data with a precoding matrix selected from a codebook comprising matrices that are expressed as
V
=
[
v
1
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
v
2
]
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
Φ
(
v
1
2
)
HH
(
v
2
Φ
(
v
1
2
)
-
e
1
M
-
1
)
[
0
v
3
]
]
,
…
]
,
where the transmitter has M transmit antennas, e 1 N =[1, 0, . . . , 0] T εC N (N=M, M−1, . . . ), C N being N-dimensional complex space, v a denotes a column vector, v b a denotes the b th element of vector v a ,
Φ
(
v
b
a
)
=
v
b
a
||
v
b
a
||
,
and
HH
(
w
)
=
{
I
-
2
ww
H
||
w
||
2
if
w
≠
0
I
if
w
=
0
is the house-holder transformation of vector w; and
a receiver to receive the precoded data from the transmitter.
27. The wireless communications system as in claim 26 , wherein the transmitter comprises a base station and the receiver comprises a user equipment.
28. The wireless communications system as in claim 26 , wherein the transmission is downlink transmission.
29. A wireless communications system comprising:
a transmitter to receive feedback information for transmission; and
a receiver to provide the feedback information in order for the transmitter to select a precoding matrix from a codebook comprising matrices that are expressed as
V
=
[
v
1
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
v
2
]
,
Φ
(
v
1
1
)
HH
(
v
1
Φ
(
v
1
1
)
-
e
1
M
)
[
0
Φ
(
v
1
2
)
HH
(
v
2
Φ
(
v
1
2
)
-
e
1
M
-
1
)
[
0
v
3
]
]
,
…
]
,
where the transmitter has M transmit antennas, e i N =[1, 0, . . . , 0] T εC N (N=M, M−1, . . . ), C N being N-dimensional complex space, v a denotes a column vector, v b a denotes the b th element of vector v a ,
Φ
(
v
b
a
)
=
v
b
a
||
v
b
a
||
,
and
HH
(
w
)
=
{
I
-
2
ww
H
||
w
||
2
if
w
≠
0
I
if
w
=
0
is the house-holder transformation of vector w.
30. The wireless communications system as in claim 29 , wherein the transmitter comprises a transmitter and the receiver comprises a receiver.
31. The wireless communications system as in claim 29 , wherein the transmission is downlink transmission.