US 7,330,519 B2Granted

Method for decoding linear space-time codes in a multiple-antenna wireless transmission system and decoder therefor

AssigneeComsis

InventorPhilippe Leclair

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Abstract

An iterative method and a decoder for decoding space-time codes in a communication system with multiple transmission and reception antennae, strikes a compromise between techniques based on interference cancellation algorithms such as BLAST, which show faulty performance concerning error rate based on signal-to-noise ratio and techniques based on maximum likelihood algorithms which are optimal in terms of performance, but highly complex in implantation such as the sphere decoder. Therefor the method includes using a first matrix product between the received signal (Y) and a shaping matrix (Bl), and a second matrix product between a subtraction matrix (Dl) and the vector of the estimated symbols (S1−l) during the preceding iteration. The estimated symbols during the current iteration are generated by a subtractor (9) receiving the results (rl,zl) of the two matrix products. The role of the matrix Dl is to subtract from the current information symbol Sl the interference caused by the other information symbols.

Claims13

Dependent claims

An iterative method for decoding a signal vector Y obtained from N sampled signals in a space-time communication system with M transmission antennae and N receiving antennae, with N and M being integers and N greater than or equal to M, with a view to obtaining an estimation of symbols of signals transmitted;

characterized in that each iteration comprises the following steps:
Pre-processing of the vector Y in order to maximize a signal to noise+interference ratio in order to obtain a signal {tilde over (r)}l,
Subtraction from the signal {tilde over (r)}l of a signal {circumflex over (z)}l by means of a subtractor, the signal {circumflex over (z)}l being obtained by reconstruction post-processing of an interference between symbols of an iteration in progress from symbols estimated during a preceding iteration,
Detection of a signal generated by the subtractor in order to obtain, for the iteration in progress, an estimation of the symbols of the signals transmitted;
and in that, the N signals being processed by time intervals T corresponding to a time length of a linear space-time code associated with the signals transmitted, the pre-processing step utilizes a matrix B in order to maximize the signal to noise+interference ratio, a transfer function of which is:
B
l
=
Diag
(
1
ρ
l
-
1
2
⁢
A
i
l
+
N
0
E
s
)
⁢
⁢
1
≤
i
≤
MT
·
C
H
⁢
V
l
with
⁢
⁢
V
l
=
[
1
-
ρ
l
-
1
2
N
0
E
s
·
C
·
C
H
+
Id
N
]
-
1
;
A
l
=
diag
⁡
(
C
H
·
V
l
·
C
)
;
wherein Λ:
iteration index;
ρ:
standardized correlation coefficient between real symbols and estimated symbols;
N0:
noise variance;
Es:
mean energy of a symbol;
C:
extended channel matrix;
IdN:
identity matrix of size N;
CH:
conjugate transpose of C;
i:
index ranging from 1 to MT;
and in that a post-processing step involves a matrix D for the reconstruction of the interference between symbols, a transfer function of which is:
D
l
=
B
l
·
C
·
ρ
l
-
1
-
Diag
(
1
ρ
l
-
1
2
⁢
A
i
l
+
N
0
E
s
)
⁢
1
≤
i
≤
MT
.

136 more elements

A space-time decoder for decoding a signal vector Y obtained from N sampled signals in a space-time communication system with M transmission antennae and N receiving antennae, with N and M being integers and N greater than or equal to M, with a view to obtaining an estimation of symbols of signals transmitted, characterized in that it comprises:

a pre-processing module of the vector Y for maximizing a signal to noise+interference ratio in order to obtain a signal {tilde over (r)}l,
a post-processing module for reconstruction of an interference between symbols from symbols estimated during a preceding iteration in order to generate the signal {circumflex over (z)}l,
a subtractor for subtracting a signal {circumflex over (z)}l from the signal {tilde over (r)}l,
a threshold detector for detecting a signal generated by the subtractor in order to obtain, for an iteration in progress, an estimation of the symbols of the signals transmitted;
and in that the N sampled signals being processed by intervals of time T corresponding to a time length of a linear space-time code associated with the signals transmitted, the pre-processing module utilizes a matrix B for maximizing the signal to noise+interference ratio, a transfer function of which is:
B
l
=
Diag
(
1
ρ
l
-
1
2
⁢
A
i
l
+
N
0
E
s
)
⁢
1
≤
i
≤
MT
·
C
H
⁢
V
l
with
⁢
⁢
V
l
=
[
1
-
ρ
l
-
1
2
N
0
E
S
·
C
·
C
H
+
Id
N
]
-
1
;
A
l
=
diag
⁡
(
C
H
·
V
l
·
C
)
;
wherein l:
iteration index;
ρ:
standardized correlation coefficient between the real symbols and the estimated symbols;
N0:
noise variance;
Es:
mean energy of a symbol;
C:
extended channel matrix;
IdN:
identity matrix of size N;
CH:
conjugate transpose of C;
i:
index ranging from 1 to MT;
and in that the post-processing module consists of a matrix D for the reconstruction of the interference between symbols, a transfer function of which is:
D
l
=
B
l
·
C
·
ρ
l
-
1
-
Diag
(
1
ρ
l
-
1
2
⁢
A
i
l
+
N
0
E
S
)
⁢
1
≤
i
≤
MT
.

135 more elements

Dependencies are inferred from the claim text.