Method and system for optimal receive diversity combining
The present invention discloses a method and system for receive signal diversity combining that achieves the high effective SNR and high coding gain. The receive signal diversity combining method combines two or more received diversified signals of a predetermined original message and employs a Maximum Likelihood (ML) detection method to process the diversified signals to generate Log-Likelihood Ratio (LLR) data to exploit the available signal diversity and coding gain of each bit and to help the channel decoder to correctly determine the predetermined original message.
1 . A method for receive diversity combining, the method comprising:
receiving two or more diversified signals of a predetermined original message;
down-converting the diversified signals;
processing the down converted diversified signals by employing a maximum likelihood (ML) detection to generate a log-likelihood ratio (LLR) data; and
decoding the LLR data to determine the original message.
2 . The method of claim 1 , wherein the diversified signals are time diversity signals.
3 . The method of claim 1 , wherein the diversified signals are spatial diversity signals.
4 . The method of claim 1 , wherein the diversified signals are frequency diversity signals.
5 . The method of claim 1 , wherein the diversified signals includes at least two or more diversity signals of at least one type (i.e. time, spatial or frequency).
6 . The method of claim 1 , wherein the employing the Maximum Likelihood (ML) detection further includes obtaining a probability when a kth bit of the transmitted symbol s is equal to bε{0, 1} wherein a mathematical representation is
λ
k
(
y
1
,
…
,
y
N
,
b
)
=
log
∑
x
∈
S
k
,
b
Pr
(
y
1
,
…
,
y
N
s
,
h
1
,
…
,
h
N
)
≡
log
∑
x
∈
S
k
,
b
exp
(
-
1
2
σ
2
∑
i
=
1
N
y
i
-
h
i
x
2
)
;
where a first vector set
(h 1 , h 2 , . . . , h N ) includes a fading channel coefficient of each channel carrying the diversified signal, and a second vector set (y 1 , y 2 , . . . , y N ) including down-converted signals of the channels carrying the diversified signals.
7 . The method of claim 5 , wherein employing the Maximum Likelihood (ML) detection further includes generating a LLR data Γ k when the LLR of the kth bit of the transmitted symbol s is equal to the difference of λ k for the two choices of b wherein a mathematical representation is:
Γ k ( y )=λ k ( y 1 , . . . , y N , 0)−λ k ( y 1 , . . . , y N , 1)
8 . A method for receive signal diversity combining, the method comprising:
receiving two or more diversified signals of a predetermined original message;
down-converting the diversified signals;
processing the down converted diversified signals by employing a maximum likelihood (ML) detection to generate a log-likelihood ratio (LLR) data; and
decoding the LLR data to determine the original message,
wherein the employing the Maximum Likelihood (ML) detection further includes obtaining a probability when a kth bit of the transmitted symbol s is equal to bε{0, 1} wherein a mathematical representation is:
λ
k
(
y
1
,
…
,
y
N
,
b
)
=
log
∑
x
∈
S
k
,
b
Pr
(
y
1
,
…
,
y
N
s
,
h
1
,
…
,
h
N
)
≡
log
∑
x
∈
S
k
,
b
exp
(
-
1
2
σ
2
∑
i
=
1
N
y
i
-
h
i
x
2
)
;
where a first vector set
(h 1 , h 2 , . . . , h N ) includes a fading channel coefficient of each channel carrying the diversified signal, and a second vector set (y 1 , y 2 , . . . , y N ) includes down-converted signals of the channels carrying the diversified signals, and
wherein the employing the Maximum Likelihood (ML) detection further includes generating a LLR data Γ k when the LLR of the kth bit of the transmitted symbol s is equal to the difference of λ k for the two choices of b wherein a mathematical representation is
Γ k ( y )=λ k ( y 1 , . . . , y N , 0)−λ k ( y 1 , . . . , y N , 1)
9 . The method of claim 7 , wherein the diversified signals are time diversity signals.
10 . The method of claim 7 , wherein the diversified signals are spatial diversity signals.
11 . The method of claim 7 , wherein the diversified signals are frequency diversity signals.
12 . The method of claim 7 , wherein the diversified signals include at least two or more diversity signals of at least one type (i.e. time, spatial or frequency).
13 . A receive diversity combining system comprising:
one or more antennas for receiving two or more diversified signals based on an original message;
one or more RF and pre-baseband processing modules associated with the antennas for processing the received diversified signals;
at least one optimal receive diversity combining module for employing Maximum Likelihood (ML) detection to process the diversified signals to generate a Log-Likelihood Ratio (LLR) data; and
at least one decoder for decoding the LLR data to determine the original message.
14 . The system of claim 11 , wherein the diversified signals are received with one or more antennas placed apart in space.
15 . The system of claim 11 , wherein the RF and pre-baseband processing modules down-convert the received diversified signals.
16 . The system of claim 11 , wherein the optimal receive diversity module employing the Maximum Likelihood (ML) detection further obtains a probability when a kth bit of the transmitted symbol s is equal to bε{0, 1} wherein a mathematical representation is:
λ
k
(
y
1
,
…
,
y
N
,
b
)
=
log
∑
x
∈
S
k
,
b
Pr
(
y
1
,
…
,
y
N
s
,
h
1
,
…
,
h
N
)
≡
log
∑
x
∈
S
k
,
b
exp
(
-
1
2
σ
2
∑
i
=
1
N
y
i
-
h
i
x
2
)
;
where a first vector set
(h 1 , h 2 , . . . , h N ) includes a fading channel coefficient of each channel carrying the diversified signal, and a second vector set (y 1 , y 2 , . . . , y N ) including down-converted signals of the channels carrying the diversified signals, and
wherein employing the Maximum Likelihood (ML) detection further includes generating a LLR data Γ k when the LLR of the kth bit of the transmitted symbol s is equal to the difference of λ k for the two choices of b wherein a mathematical representation is:
Γ k ( y )=λ k ( y 1 , . . . , y N , 0)−λ k ( y 1 . . . ., y N , 1)