US 8,477,881 B2Granted

Method and apparatus for determining receiver beam forming vectors in multi-user MIMO systems

AssigneeKabushiki Kaisha Toshiba

InventorFengming Cao

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Abstract

According to one embodiment there is provided a method of determining receiver beam forming vectors for a plurality of receivers in a MIMO system. Each receiver comprises a plurality of receiver antennae. The MIMO system also comprises a plurality of transmitter antennae. The method comprises quantifying the properties of the channels of the MIMO system in a channel property matrix including interference between individual channels and performing Cholesky decomposition of the receiver property matrix row-by-row into a lower triangular matrix with unit elements along its diagonal, a diagonal matrix and the Hermitian transpose of said triangular matrix. Performing the Cholesky decomposition comprises determining, when performing a step of the Cholesky decomposition for a row, a receiver-beam forming vector associated with the row that maximises the component of the diagonal matrix in the row.

Claims11

Dependent claims

A method of determining receiver beam forming vectors for a plurality of receivers in a MIMO system, wherein each receiver comprises a plurality of receiver antennae and wherein the MIMO system comprises a plurality of transmitter antennae, the method comprising:

quantifying the characteristics of the channels of the MIMO system in a channel property matrix Ψ including interference between individual channels,
performing Cholesky decomposition of the channel property matrix row-by-row into a lower triangular matrix with unit elements along its diagonal, a diagonal matrix and the Hermitian transpose of the lower triangular matrix, comprising determining, when performing a step of the Cholesky decomposition for a row, a receiver beam forming vector associated with the row that maximises the component of the diagonal matrix in the row;
wherein the matrix quantifying the characteristics of said channel is:
H
i
⁢
H
i
H
+
γ
⁢
⁢
I
N
r
-
∑
j
=
1
i
-
1
⁢
s
ij
⁢
s
ij
H
⁢
q
j
for i rows/steps of the Cholesky decomposition for i>0, wherein Hi is the channel matrix of the receiver associated with a current row/step of the Cholesky decomposition, HiH is the Hermitian transpose of Hi, γ is the expectation of noise that will be received INr is an Nr ×Nr identity matrix, wherein Nr is the number of receiver antennae of the receiver, sij is
s
ij
=
{
H
i
⁢
h
⋒
i
H
q
1
if
⁢
⁢
j
=
1
(
H
i
⁢
h
⋒
j
H
-
∑
n
=
1
j
-
1
⁢
s
i
⁢
⁢
n
⁢
l
jn
*
⁢
q
n
)
q
j
if
⁢
⁢
j
>
1
ĥjH is the Hermitian transpose of rjHj, wherein rj is the receiver beam forming vector associated with the j-th element of the diagonal matrix, Hj is the channel matrix associated with the j-th element of the diagonal matrix, qi is:
q
i
=
Ψ
ii
-
∑
k
i
-
1
⁢
l
ik
⁢
l
ik
*
⁢
q
k
wherein:
l
ij
=
1
q
j
⁢
(
Ψ
ij
-
∑
n
j
-
1
⁢
l
i
⁢
⁢
n
⁢
l
jn
*
⁢
q
n
)
,
for
⁢
⁢
i
>
j
l
ij
=
1
,
for
⁢
⁢
i
=
j
l
ij
=
0
,
for
⁢
⁢
i
<
j
Ψ
ii
=
h
⋒
i
⁢
h
⋒
i
H
+
γ
⁢
⁢
and
⁢
⁢
⁢
Ψ
ij
=
h
⋒
i
⁢
h
⋒
j
H
h
⋒
i
=
r
i
⁢
H
i
sijH is the Hermitian transpose of sij, ljn* is the conjugate of ljn.

211 more elements

A device for determining receiver beam forming vectors for a plurality of receivers in a MIMO system, wherein each receiver comprises a plurality of receiver antennae and wherein the MIMO system comprises a plurality of transmitter antennae, the device comprising:

a quantifier for quantifying in a channel property matrix the characteristics of receiver channels of the MIMO system, including interference between individual channels,
a processor arranged to perform Cholesky decomposition of the channel property matrix in a row-by-row fashion into a lower triangular matrix with unit elements along its diagonal, a diagonal matrix and the Hermitian transpose of the lower triangular matrix, wherein the processor is further arranged to determine, when performing a step of the Cholesky decomposition for a row, a receiver beam forming vector associated with the row that maximises the component of the diagonal matrix in the row;
wherein the matrix quantifying the characteristics of said channel is:
H
i
⁢
H
i
H
+
γ
⁢
⁢
I
N
r
-
∑
j
=
1
i
-
1
⁢
s
ij
⁢
s
ij
H
⁢
q
j
for i rows/steps of the Cholesky decomposition for i>0, wherein Hi is the channel matrix of the receiver associated with a current row/step of the Cholesky decomposition, HiH is the Hermitian transpose of Hi, γ is the expectation of noise that will be received, INr is an Nr×Nr identity matrix, wherein Nr is the number of receiver antennae of the receiver, sij is
s
ij
=
{
H
i
⁢
h
⋒
j
H
q
1
if
⁢
⁢
j
=
1
(
H
i
⁢
h
⋒
j
H
-
∑
n
=
1
j
-
1
⁢
s
in
⁢
l
jn
*
⁢
q
n
)
q
j
if
⁢
⁢
j
>
1
ĥjH is the Hermitian transpose of rjHj, wherein rj is the receiver beam forming vector associated with the j-th element of the diagonal matrix, Hj is the channel matrix associated with the j-th element of the diagonal matrix, qi is:
q
i
=
Ψ
ii
-
∑
k
i
-
1
⁢
l
ik
⁢
l
ik
*
⁢
q
k
wherein:
l
ij
=
1
q
j
⁢
(
Ψ
ij
-
∑
n
j
-
1
⁢
l
in
⁢
l
jn
*
⁢
q
n
)
,
⁢
for
⁢
⁢
i
>
j
l
ij
=
1
,
⁢
for
⁢
⁢
i
=
j
l
ij
=
0
,
⁢
for
⁢
⁢
i
<
j
Ψ
ii
=
h
⋒
i
⁢
h
⋒
i
H
+
γ
⁢
⁢
and
⁢
⁢
Ψ
ij
=
h
⋒
i
⁢
h
⋒
j
H
h
^
i
=
r
i
⁢
H
i
sijH is the Hermitian transpose of sij, ljn* is the conjugate of ljn.

207 more elements

A device for determining a receiver beam forming vector for a receiver of a plurality of receivers in a MIMO system, wherein each receiver comprises plural receiver antennae, the device comprising:

a quantifier for quantifying in a matrix the characteristics of a channel of the receiver and interference said receiver experiences from other receivers for which a receiver beam forming vector had previously been determined,
wherein the matrix quantifying the characteristics of the said channel is:
H
i
⁢
H
i
H
+
γ
⁢
⁢
I
N
r
-
∑
j
=
1
i
-
1
⁢
s
ij
⁢
s
ij
H
⁢
q
j
for i rows/steps of the Cholesky decomposition for i>0, wherein Hi is the channel matrix of the receiver associated with a current row/step of the Cholesky decomposition, HiH is the Hermitian transpose of Hi, γ is the expectation of noise that will be received, INr is an Nr×Nr identity matrix, wherein Nr is the number of receiver antennae of the receiver, sij is
s
ij
=
{
H
i
⁢
h
⋒
i
H
q
1
if
⁢
⁢
j
=
1
(
H
i
⁢
h
⋒
j
H
-
∑
n
=
1
j
-
1
⁢
s
in
⁢
l
jn
*
⁢
q
n
)
q
j
if
⁢
⁢
j
>
1
ĥjH is the Hermitian transpose of rjHj, wherein rj is the receiver beam forming vector associated with the j-th element of the diagonal matrix, Hj is the channel matrix associated with the j-th element of the diagonal matrix, qi is:
q
i
=
Ψ
ii
-
∑
k
i
-
1
⁢
l
ik
⁢
l
ik
*
⁢
q
k
wherein:
l
ij
=
1
q
j
⁢
(
Ψ
ij
-
∑
n
j
-
1
⁢
l
in
⁢
l
jn
*
⁢
q
n
)
,
⁢
for
⁢
⁢
i
>
j
l
ij
=
1
,
⁢
for
⁢
⁢
i
=
j
l
ij
=
0
,
⁢
for
⁢
⁢
i
<
j
Ψ
ii
=
h
⋒
i
⁢
h
⋒
i
H
+
γ
⁢
⁢
and
⁢
⁢
Ψ
ij
=
h
⋒
i
⁢
h
⋒
j
H
h
⋒
i
=
r
i
⁢
H
i
sijH is the Hermitian transpose of sij, ljn* is the conjugate of ljn;
and
a processor arranged to determine the receiver beam forming vector, wherein the processor is arranged to determine a left singular vector of the matrix that corresponds to the maximal singular value of the matrix.
a processor arranged to perform Cholesky decomposition of the received matrix in a row-by-row fashion into a lower triangular matrix with unit elements along its diagonal, a diagonal matrix and the Hermitian transpose of the lower triangular matrix, wherein the processor is further arranged to determine, when performing a step of the Cholesky decomposition for a row, a receiver beam forming vector associated with the row that maximises the component of the diagonal matrix in the row.

209 more elements

Dependencies are inferred from the claim text.