Excess delay spread detection method for multi-carrier communication systems
View Patent ↗A method for detecting a presence of an excess delay spread within a received signal is provided. First, a quantitative estimation of a similarity of two segments of the received signal is performed. Thereafter, the presence of the excess delay spread within the received signal based upon the quantitative estimation is determined. In determining the presence of an excess delay spread, the quantitative estimation can be compared to a detection threshold.
1. A method for operating a receiver in detecting a presence of an excess delay spread within a received signal, said method comprising:
calculating a quantitative estimation QE of a similarity of two segments of the received signal, wherein calculating the quantitative estimation QE comprises using a representation of a mean magnitude of a difference vector of length m samples beyond the beginning (L-N) samples of the received signal, wherein L is a symbol duration, N is a fast Fourier transform size, and m is a fraction of N; and
determining the presence or an absence of the excess delay spread in the received signal based upon the quantitative estimation.
2. The method of claim 1 , wherein a calculation of the quantitative estimation QE is according to:
QE
=
20
P
log
10
(
1
m
∑
n
=
1
m
S
(
L
-
N
+
n
)
-
S
(
L
-
(
N
/
2
)
+
n
)
P
1
m
∑
n
=
1
m
S
(
L
-
(
N
/
2
)
-
m
+
n
)
-
S
(
L
-
m
+
n
)
P
)
;
and
wherein L is a symbol duration, N is a fast Fourier transform size, m is a fraction of N, S are signal samples, and P is an integer.
3. The method of claim 1 , wherein a calculation of the quantitative estimation QE is according to:
QE
=
20
P
log
10
(
1
m
∑
n
=
1
m
S
(
L
-
(
N
/
2
)
-
m
+
n
)
-
S
(
L
-
m
+
n
)
P
1
m
∑
n
=
1
m
S
(
L
-
N
+
n
)
-
S
(
L
-
(
N
/
2
)
+
n
)
P
)
;
and
wherein L is a symbol duration, N is a fast Fourier transform size, m is a fraction of N, S are signal samples, and P is an integer.
4. The method of claim 1 , wherein a calculation of the quantitative estimation QE is according to:
QE
=
20
P
log
10
(
1
m
∑
n
=
1
m
S
(
L
-
(
N
/
2
)
-
m
+
n
)
-
S
(
L
-
m
+
n
)
P
+
S
(
L
-
N
+
n
)
-
S
(
L
-
(
N
/
2
)
+
n
)
P
1
m
∑
n
=
1
m
S
(
L
-
(
3
N
/
4
)
+
n
)
-
S
(
L
-
(
N
/
4
)
+
n
)
P
)
;
and
wherein L is a symbol duration, N is a fast Fourier transform size, m is a fraction of N, S are signal samples, and P is an integer.
5. A method of operating a receiver in detecting a presence of an excess delay spread within a received signal, said method comprising:
calculating a quantitative estimation of a similarity of two segments of the received signal, wherein calculating the quantitative estimation comprises using a representation of a mean magnitude of a difference vector of length m samples beyond the beginning (L-N) samples of the received signal, wherein L is a symbol duration, N is a fast Fourier transform size, and m is a fraction of N; and
determining the presence or an absence of the excess delay spread in the received signal based on a comparison of the quantitative estimation and a detection threshold.
6. The method of claim 5 , wherein a calculation of the quantitative estimation QE is according to:
QE
=
20
P
log
10
(
1
m
∑
n
=
1
m
S
(
L
-
N
+
n
)
-
S
(
L
-
(
N
/
2
)
+
n
)
P
1
m
∑
n
=
1
m
S
(
L
-
(
N
/
2
)
-
m
+
n
)
-
S
(
L
-
m
+
n
)
P
)
;
and
wherein L is a symbol duration, N is a fast Fourier transform size, m is a fraction of N, S are signal samples, and P is an integer.
7. The method of claim 5 , wherein a calculation of the quantitative estimation QE is according to:
QE
=
20
P
log
10
(
1
m
∑
n
=
1
m
S
(
L
-
(
N
/
2
)
-
m
+
n
)
-
S
(
L
-
m
+
n
)
P
1
m
∑
n
=
1
m
S
(
L
-
N
+
n
)
-
S
(
L
-
(
N
/
2
)
+
n
)
P
)
;
and
wherein L is a symbol duration, N is a fast Fourier transform size, m is a fraction of N, S are signal samples, and P is an integer.
8. The method of claim 5 , wherein a calculation of the quantitative estimation QE is according to:
QE
=
20
P
log
10
(
1
m
∑
n
=
1
m
S
(
L
-
(
N
/
2
)
-
m
+
n
)
-
S
(
L
-
m
+
n
)
P
+
S
(
L
-
N
+
n
)
-
S
(
L
-
(
N
/
2
)
+
n
)
P
1
m
∑
n
=
1
m
S
(
L
-
(
3
N
/
4
)
+
n
)
-
S
(
L
-
(
N
/
4
)
+
n
)
P
)
;
and
wherein L is a symbol duration, N is a fast Fourier transform size, m is a fraction of N, S are signal samples, and P is an integer.
9. A receiver, comprising:
means for calculating a quantitative estimation QE of a similarity of two segments of a received signal, wherein calculating the quantitative estimation QE comprises using a representation of a mean magnitude of a difference vector of length m samples beyond the beginning (L-N) samples of the received signal, wherein L is a symbol duration, N is a fast Fourier transform size, and m is a fraction of N; and
means for determining the presence or an absence of the excess delay spread in the received signal based upon the quantitative estimation.
10. A method for operating a first communication unit in detecting a presence of an excess delay spread in a communication channel between the first communication unit and a second communication unit, said method comprising:
receiving a signal over the communication channel from the second communication unit, the signal having a first segment and a second segment; and
determining the presence or an absence of the excess delay spread in the received signal based upon a quantitative estimation of a similarity of the first segment and the second segment, wherein the quantitative estimation is determined using a representation of a mean magnitude of a difference vector of length m samples beyond the beginning (L—N) samples of the received signal, wherein L is a symbol duration, N is a fast Fourier transform size, and m is a fraction of N.
11. The method of claim 10 , further comprising:
transmitting a message to the second communication unit upon a determination of presence of the excess delay spread in the received signal, the message indicating the presence of the excess delay spread in the communication channel.
12. The method of claim 10 , further comprising:
adapting the operation of the first communication unit in view a determination presence of the excess delay spread in the received signal.
13. A method for adapting a receiver in a communication unit, said method comprising:
receiving a signal which was transmitted with a first segment and a second segment;
determining a presence or an absence of an excess delay spread in the received signal based upon a quantitative estimation of a similarity of the first segment and the second segment, wherein the quantitative estimation is determined using a representation of a mean magnitude of a difference vector of length m samples beyond the beginning (L-N) samples of the received signal, wherein L is a symbol duration, N is a fast Fourier transform size, and m is a fraction of N; and
adapting the receiver based upon the detected presence of the excess delay spread in the signal in response to a determination of the presence of the excess delay spread in the received signal.
14. The method of claim 13 , wherein the act of adapting the receiver includes determining one or more coefficients of a channel estimation filter in the receiver.