Method and system for an efficient channel quantization method for MIMO pre-coding systems
View Patent ↗A method and system for processing communication signals is provided and may comprise, quantizing a channel estimate at a MIMO receiver onto a codebook based on a cost function, wherein the codebook comprises a plurality of unitary matrices. A codebook index may be fed back from the MIMO receiver to a MIMO transmitter, wherein the codebook index is associated with one of the plurality of unitary matrices that minimizes the cost function. The cost function may be minimized by choosing a smallest scalar cost from a plurality of scalar costs, wherein each one of the scalar costs is generated from one or more sums and one or more products of elements of a product matrix, and wherein the product matrix is generated from one of the plurality of unitary matrices, a matrix comprising the channel estimate, and their respective Hermitian Transposes.
1. A method for processing communication signals, the method comprising:
quantizing a channel estimate at a MIMO receiver onto a codebook based on a cost function, wherein said codebook comprises a plurality of unitary matrices;
feeding back a codebook index from said MIMO receiver to a MIMO transmitter, wherein said codebook index is associated with one of said plurality of unitary matrices that minimizes said cost function;
minimizing said cost function by choosing a smallest scalar cost from a plurality of scalar costs, wherein each one of said scalar costs is generated from one or more sums and one or more products of elements of a product matrix, wherein said product matrix is generated from one of said plurality of unitary matrices, a matrix comprising said channel estimate, and their respective Hermitian Transposes; and
adjusting said codebook based on a plurality of said fed-back codebook indices.
2. The method according to claim 1 , wherein said matrix comprising said channel estimate is a matrix Ĥ.
3. The method according to claim 2 , wherein said cost function is defined by the following relationship:
V
q
=
arg
min
V
^
i
∈
C
f
(
V
^
i
H
·
H
^
H
·
H
^
·
V
^
i
)
where V q , {circumflex over (V)} i εC, and Ĥ are matrices of appropriate dimensions and C is said codebook.
4. The method according to claim 1 , wherein said scalar cost function comprises a function f(A), which is defined by the following relationship:
f
(
A
)
=
∑
i
=
1
N
∑
j
=
1
,
j
≠
i
N
a
i
,
j
2
where A is said product matrix of size N by N and a ij is element (i,j) of matrix A.
5. The method according to claim 1 , wherein said scalar cost function comprises a function f(A), which is defined by the following relationship:
f
(
A
)
=
∑
i
=
1
N
∑
j
=
1
,
j
≠
i
N
a
i
,
j
2
-
∑
i
=
1
N
a
i
,
i
where A is said product matrix of size N by N and a ij is element (i,j) of matrix A.
6. The method according to claim 1 , wherein a number of transmit antennas and a number of receive antennas is at least one each.
7. The method according to claim 1 , comprising linearly transforming a vector signal at said MIMO transmitter using said one of said plurality of unitary matrices that minimizes said cost function.
8. The method according to claim 1 , comprising adjusting said codebook dynamically.
9. A system for processing communication signals, said system comprising: one or more circuits operable to:
quantize a channel estimate at a MIMO receiver onto a codebook based on a cost function, wherein said codebook comprises a plurality of unitary matrices;
feed back a codebook index from said MIMO receiver to a MIMO transmitter, wherein said codebook index is associated with one of said plurality of unitary matrices that minimizes said cost function;
minimize said cost function by choosing a smallest scalar cost from a plurality of scalar costs, wherein each one of said scalar costs is generated from one or more sums and one or more products of elements of a product matrix, wherein said product matrix is generated from one of said plurality of unitary matrices, a matrix comprising said channel estimate, and their respective Hermitian Transposes; and
adjust said codebook based on a plurality of said fed-back codebook indices.
10. The system according to claim 9 , wherein said matrix comprising said channel estimate is a matrix Ĥ.
11. The system according to claim 10 , wherein said cost function is defined by the following relationship:
V
q
=
arg
min
V
^
i
∈
C
f
(
V
^
i
H
·
H
^
H
·
H
^
·
V
^
i
)
where V q , {circumflex over (V)} i εC, and H are matrices of appropriate dimensions and C is said codebook.
12. The system according to claim 9 , wherein said scalar cost function comprises a function f(A), which is defined by the following relationship:
f
(
A
)
=
∑
i
=
1
N
∑
j
=
1
,
j
≠
i
N
a
i
,
j
2
where A is said product matrix of size N by N and a ij is element (i,j) of matrix A.
13. The system according to claim 9 , wherein said scalar cost function comprises a function f(A), which is defined by the following relationship:
f
(
A
)
=
∑
i
=
1
N
∑
j
=
1
,
j
≠
i
N
a
i
,
j
2
-
∑
i
=
1
N
a
i
,
i
where A is said product matrix of size N by N and a ij is element (i,j) of matrix A.
14. The system according to claim 9 , wherein a number of transmit antennas and a number of receive antennas is at least one each.
15. The system according to claim 9 , wherein said one or more circuits linearly transform a vector signal at said MIMO transmitter using said one of said plurality of unitary matrices that minimizes said cost function.
16. The system according to claim 9 , wherein said one or more circuits adjust said codebook dynamically.