Mode selection for MIMO in wireless communication
View Patent ↗A method for transmission mode selection in a MIMO radio system between a spatial diversity (A-matrix) mode and a spatial multiplexing (B-matrix) mode comprises: obtaining a channel condition number; if the channel condition number is above a selected threshold, and a signal to interference plus noise ratio exceeds a predetermined threshold then selecting spatial multiplexing; and otherwise selecting spatial diversity.
1. A method for transmission mode selection in a MIMO radio system, the selection between a first mode of spatial diversity and a second mode of spatial multiplexing, the method carried out using an electronic processor the method comprising:
obtaining a channel condition number;
if the channel condition number is above a selected threshold, and a signal to interference plus noise ratio exceeds a predetermined threshold then selecting the mode of spatial multiplexing; and
otherwise selecting the mode of spatial diversity;
wherein said channel signal to interference plus noise ratio comprises effective Carrier interference noise ratio (ECINR), the method further comprising using Exponential Effective SINR Mapping (EESM) as a metric of said ECINR wherein said EESM metric is calculated from
EESM
=
-
β
ln
[
1
N
∑
n
=
1
L
∑
k
=
1
N
ⅇ
-
γ
k
,
n
/
β
]
wherein L is the number of spatial streams at the mobile station (MS) side, N is the number of occupied subcarrier groups, γ k,n is the CINR per subcarrier group computed by a receiving station
and β is a matching factor.
2. The method of claim 1 , wherein the first mode is the matrix A mode, and the second mode is the matrix B mode.
3. The method of claim 1 , wherein a channel condition number threshold is substantially 0.7.
4. A method for transmission mode selection in a MIMO radio system, the selection between a first mode of spatial diversity and a second mode of spatial multiplexing, the method being carried out on an electronic processor, the method comprising:
obtaining a channel condition number;
if the channel condition number is above a selected threshold, and a signal to interference plus noise ratio exceeds a predetermined threshold then selecting the mode of spatial multiplexing; and
otherwise selecting the mode of spatial diversity, wherein said channel signal to interference plus noise ratio comprises effective Carrier interference noise ratio (ECINR), comprising using post-processing physical CINR as a metric of said ECINR, wherein said post-processing physical CINR is
≈
10
log
10
1
NK
∑
k
=
1
K
∑
n
=
1
N
log
(
λ
n
,
k
)
-
10
log
10
1
K
∑
k
=
1
K
log
(
σ
k
2
)
.
5. The method of claim 1 , wherein said predetermined threshold is substantially 16 decibels.
6. A method for transmission mode selection in a MIMO radio system, the selection between a first mode of spatial diversity and a second mode of spatial multiplexing, the method being carried out on an electronic processor, the method comprising:
obtaining a channel condition number;
if the channel condition number is above a selected threshold, and a signal to interference plus noise ratio exceeds a predetermined threshold then selecting the mode of spatial multiplexing; and
otherwise selecting the mode of spatial diversity wherein said condition number is a ratio of respectively smaller and larger of channel singular values, the method comprising obtaining a channel matrix prior to obtaining said condition number by using a pilot signal, wherein said singular values are obtained by calculating a singular value decomposition (SVD) of said channel matrix, to produce a diagonal matrix having two non-zero elements, said non-zero elements being said singular values.
7. Apparatus for transmission mode selection in a MIMO radio system, the selection between a first mode of spatial diversity and a second mode of spatial multiplexing, the apparatus comprising:
a channel measurement and calculation unit for obtaining a broadband channel condition number;
and a mode selector associated with said channel measurement and calculation unit configured to either select the mode of spatial multiplexing if the broadband channel condition number is above a selected threshold 1 , and a channel signal to interference plus noise ratio exceeds a predetermined threshold, or otherwise to select the mode of spatial diversity; wherein said channel signal to interference plus noise ratio comprises effective Carrier interference noise ratio (ECINR), the method further comprising using Exponential Effective SINR Mapping (EESM) as a metric of said ECINR wherein said EESM metric is calculated from
EESM
=
-
β
ln
[
1
N
∑
n
=
1
L
∑
k
=
1
N
ⅇ
-
γ
k
,
n
/
β
]
wherein L is the number of spatial streams at the mobile station (MS) side, N is the number of occupied subcarrier groups, γ k,n is the CINR per subcarrier group computed by the receiving station
and β is a matching factor.
8. The apparatus of claim 7 , incorporated into one member of a group comprising a mobile station, a relay station and a base station.
9. The apparatus of claim 7 , wherein the first mode is the matrix A mode, and the second mode is the matrix B mode.
10. The apparatus of claim 7 , wherein the selector is configured such that a channel condition number is above a selected threshold.
11. The apparatus of claim 7 , configured to use post-processing physical CINR as a metric of said ECINR.
12. The apparatus of claim 11 , wherein said post-processing physical CINR is
≈
10
log
10
1
NK
∑
k
=
1
K
∑
n
=
1
N
log
(
λ
n
,
k
)
-
10
log
10
1
K
∑
k
=
1
K
log
(
σ
k
2
)
.
13. The apparatus of claim 7 , wherein said predetermined threshold is substantially 16 decibels.
14. The apparatus of claim 7 , wherein said condition number is a ratio of channel singular values.
15. The apparatus of claim 14 , comprising obtaining a channel matrix prior to obtaining said condition number by using a pilot signal.
16. The apparatus of claim 15 , wherein said singular values are obtained by calculating a singular value decomposition (SVD) of said channel matrix, to produce a diagonal matrix having two non-zero elements, said non-zero elements being said singular values.