Method and apparatus for determining components of a channel impulse response for use in a SAIC equalizer
View Patent ↗A method of operation of a receiver of a mobile station or a base station of a radio access network and corresponding equipment, the method for especial use in providing interference cancellation according to a single antenna interference cancellation (SAIC) algorithm. The method includes a step ( 22 ) in which a channel estimator ( 12 ) estimates channel impulse response components for use by a SAIC equalizer ( 14 ); in estimating the channel impulse response components, the channel estimator ( 12 ) minimizes a special cost function (J ch (h)) with respect to the components of the channel impulse response h. In some embodiments, the method uses an iterative least mean squares procedure to minimize the cost function (J ch (h)).
1. A method for use by a receiver in wirelessly receiving over a communication channel a radio transmission burst of a number of symbols including a known training sequence of symbols, the communication channel having a channel response to a transmitted symbol, the receiver using an equalizer having taps based on estimated values of components of a channel impulse response characterizing the response of the communication channel to a transmitted symbol, the method comprising:
receiving and sampling the radio transmission burst; and
minimizing, with respect to possible values of the channel impulse response components, a cost function indicating a cumulative difference magnitude between power associated with estimated interference samples and an average interference power, wherein the interference samples are estimated as a difference between samples of the received radio transmission burst and the corresponding channel response to the known training sequence.
2. A method as in claim 1 , wherein the cost function is given by:
J
ch
(
h
)
=
∑
k
=
1
P
y
k
-
∑
n
=
0
L
m
k
-
n
h
n
r
-
e
_
r
s
,
in which,
e
_
r
≡
1
P
∑
k
=
1
P
y
k
-
∑
n
=
0
L
m
k
-
n
h
n
r
,
where r and s are positive integers, and where y k is a sample of the received radio transmission burst corresponding to a transmitted symbol but distorted by the communication channel, where m k−n is a symbol included in the training sequence symbols, where h n is a component of the channel impulse response, where P is the number of symbols in the transmitted training sequence, and where L+1 is the number of taps in a transversal filter used to model the communication channel.
3. A method as in claim 2 , wherein in determining estimates for the components of the channel impulse response that minimize the cost function, a least squares method is used.
4. A method as in claim 3 , wherein iteration is used in the least squares method, and after an initial value for channel impulse response is made, each next step in the iteration provides a next best estimate of the channel impulse response according to:
h
^
(
k
+
1
)
=
h
^
(
k
)
-
μ
ⅆ
ⅆ
h
J
ch
(
h
^
(
k
)
)
,
where
ⅆ
ⅆ
h
denotes the gradient vector with respect to the channel impulse response h, and μ is a step size.
5. A method as in claim 4 , wherein the initial value for channel impulse response is made using:
ĥ (0) =( M H M ) −1 M H y,
where M is a matrix constructed from the P training sequence symbols, and the y are corresponding received samples.
6. A method as in claim 2 , wherein in determining estimates for the components of the channel impulse response that minimize the cost function, a recursive least squares method is used.
7. A method as in claim 2 , wherein in determining estimates for the components of the channel impulse response that minimize the cost function, a Kalman filter is used.
8. A receiver for wirelessly receiving over a communication channel a radio transmission burst of a number of symbols including a known training sequence of symbols, the communication channel having a channel response to a transmitted symbol, the receiver using an equalizer having taps based on estimated values of components of a channel impulse response characterizing the response of the communication channel to a transmitted symbol, the receiver comprising:
means for receiving and sampling the radio transmission burst; and
means for minimizing, with respect to possible values of the channel impulse response components, a cost function indicating a cumulative difference magnitude between power associated with estimated interference samples and an average interference power, wherein the interference samples are estimated as a difference between samples of the received radio transmission burst and the corresponding channel response to the known training sequence.
9. A receiver as in claim 8 , wherein the receiver is part of a mobile station.
10. A receiver as in claim 8 , wherein the receiver is part of a base station of a radio access network of the wireless communication system.
11. A system, comprising a mobile station and a base station used as part of or with a wireless communication system, wherein both the mobile station and the base station include a receiver, wherein at least one of the receivers is as in claim 8 .
12. A receiver as in claim 8 , wherein the cost function is given by:
J
ch
(
h
)
=
∑
k
=
1
P
y
k
-
∑
n
=
0
L
m
k
-
n
h
n
r
-
e
_
r
s
,
in which,
e
_
r
≡
1
P
∑
k
=
1
P
y
k
-
∑
n
=
0
L
m
k
-
n
h
n
r
,
where r and s are positive integers, and where y k is a sample of the received radio transmission burst corresponding to a transmitted symbol but distorted by the communication channel, where m k−n is a symbol included in the training sequence symbols, where h n is a component of the channel impulse response, where P is the number of symbols in the transmitted training sequence, and where L+1 is the number of taps in a transversal filter used to model the communication channel.
13. A receiver for wirelessly receiving over a communication channel a radio transmission burst of a number of symbols including a known training sequence of symbols, the communication channel having a channel response to a transmitted symbol, the receiver using an equalizer having taps based on estimated values of components of a channel impulse response characterizing the response of the communication channel to a transmitted symbol, the receiver comprising:
a receiver filter, for receiving and sampling the radio transmission burst; and
a channel estimator, for minimizing, with respect to possible values of the channel impulse response components, a cost function indicating a cumulative difference magnitude between power associated with estimated interference samples and an average interference power, wherein the interference samples are estimated as a difference between samples of the received radio transmission burst and the corresponding channel response to the known training sequence.
14. A receiver as in claim 13 , wherein the cost function is given by:
J
ch
(
h
)
=
∑
k
=
1
P
y
k
-
∑
n
=
0
L
m
k
-
n
h
n
r
-
e
_
r
s
,
in which,
e
_
r
≡
1
P
∑
k
=
1
P
y
k
-
∑
n
=
0
L
m
k
-
n
h
n
r
,
where r and s are positive integers, and where y k is a sample of the received radio transmission burst corresponding to a transmitted symbol but distorted by the communication channel, where m k−n is a symbol included in the training sequence symbols, where h n is a component of the channel impulse response, where P is the number of symbols in the transmitted training sequence, and where L+1 is the number of taps in a transversal filter used to model the communication channel.
15. A receiver as in claim 14 , wherein in determining estimates for the components of the channel impulse response that minimize the cost function, a least squares method is used.
16. A receiver as in claim 15 , wherein iteration is used in the least squares method, and the channel estimator is configured so that after an initial value for channel impulse response is made, each next step in the iteration provides a next best estimate of the channel impulse response according to:
h
^
(
k
+
1
)
=
h
^
(
k
)
-
μ
ⅆ
ⅆ
h
J
ch
(
h
^
(
k
)
)
,
where
ⅆ
ⅆ
h
denotes the gradient vector with respect to the channel impulse response h, and μ is a step size.
17. A receiver as in claim 16 , wherein the channel estimator is configured so that the initial value for channel impulse response is made using:
ĥ (0) =( M H M ) −1 M H y,
where M is a matrix constructed from the P training sequence symbols, and the y are corresponding received samples.
18. A receiver as in claim 14 , wherein in determining estimates for the components of the channel impulse response that minimize the cost function, a recursive least squares method is used.
19. A receiver as in claim 14 , wherein in determining estimates for the components of the channel impulse response that minimize the cost function, a Kalman filter is used.