USRE43791EExpiredUtility
Systems and methods for interference cancellation in a radio receiver system
Est. expiryMay 2, 2023(expired)· nominal 20-yr term from priority
Inventors:Ayman Mostafa
H04B 17/345
44
PatentIndex Score
0
Cited by
69
References
20
Claims
Abstract
A system and method for interference cancellation is provided to cancel/greatly reduce the interference of a wireless network. The interferers are separated from a desired signal using independent component analysis by hypothesizing the transmitting sequence. An optional whitening filter is used after the signal separation to improve the signal conditioning. The separated signal is processed by a second pass channel estimation to improve the signal channel estimation and is fed to a Maximum Likelihood Sequence Estimation (MLSE) algorithm, such as a Viterbi algorithm, for signal detection.
Claims
exact text as granted — not AI-modified1. A method for suppressing interference received by an antenna, comprising:
receiving a first received signal at the antenna;
hypothesizing a second received signal;
separating an interfering signal from a desired signal using the first received signal and the hypothesized second received signal; and
filtering the desired signal;
wherein the filtering step comprises filtering through a multi-stage adaptive predictive filter having a real component and an imaginary component, and wherein an output of the imaginary component also serves as an input into a subsequent stage of the real component and wherein an output of the real component also serves as an input into a subsequent stage of the imaginary component.
2. The method of claim 1 , wherein the second received signal is hypothesized using a training sequence code.
3. The method of clam 2 , further comprising:
estimating a channel response based on the first received signal; and
wherein the training sequence code has an expected value and the first signal has an observed training sequence code associated therewith and the estimating step is based on the expected value of the training sequence code and the observed training sequence code.
4. The method of claim 3 , wherein the estimating step comprises a convolution of a transmitted filter response, received filter response, and a media response in accordance with the following equation:
h eff (n)=tx(n)*C(n)*rx(n),
wherein tx(n) is the transmitter filter response, rx(n) is the receiver filter response, C(n) is the media response, and wherein h eff (n) is a channel impulse response.
5. The method of claim 1 , wherein the separating step comprises an application of the central limit theorem.
6. The method of claim 5 , wherein the central limit theorem is implemented in accordance with the following:
a next value of
s
p
(
m
+
1
)
=
s
p
(
m
+
1
)
-
∑
P
j
=
1
s
j
s
j
H
s
p
(
m
+
1
)
,
where s p (m+1) is an estimated vector, m, j, and p are integers, s j are previously found orthogonal vectors, and s j H is the conjugate transposeof s j .
7. The method of claim 1 , wherein the separating step is selectively performed according to a carrier to interference (C/I) ratio being below a predetermined level.
8. The method of claim 7 , further comprising selectively filtering the desired signal.
9. The method of claim 8 , wherein the separating step is selectively performed as a function of the C/I ratio as applied to an initial channel estimate and a weighted C/I ratio as determined in the filtering step.
10. The method of claim 8 , wherein the filtering step and the separating step are performed when C/I ratios fall below the predetermined level.
11. The method of claim 1 , wherein the hypothesized second received signal is hypothesized using an expected value of the first received signal.
12. The method of clam 11 , wherein the first signal has an observed value associated therewith and the estimating step is based on the expected value and the observed value.
13. A method for suppressing interference received by an antenna, comprising:
receiving a first received signal at the antenna;
hypothesizing a second received signal;
separating an interfering signal from a desired signal using the first received signal and the hypothesized second received signal;
selectively filtering the desired signal; and
wherein the filtering step comprises filtering through a multi-stage adaptive predictive filter having a real component and an imaginary component, and wherein an output of the imaginary component also serves as an input into a subsequent stage of the real component and wherein an output of the real component also serves as an input into a subsequent stage of the imaginary component.
14. The method of claim 13 , wherein the filtering step is selected based on a carrier to interference (C/I) ratio.
15. The method of claim 14 , wherein the filtering step is selected when the C/I ratio falls below a predetermined threshold.
16. The method of claim 13 , wherein the filtering step is selected based on a low C/I ratio as applied to a synchronized signal.
17. A method comprising:
receiving a transmitted signal at a receiver as a first received signal;
hypothesizing another received signal based at least in part on a predefined transmit sequence associated with the first received signal;
separating one or more interfering signals from the first received signal using the first received signal and the hypothesized other received signal; and
selectively filtering the desired signal through a multi-stage adaptive predictive filter supplying a real component and an imaginary component, and wherein previous values of imaginary components serve as an input in determination of a current real component and wherein previous values of real components serve as an input in determination of a current imaginary component.
18. The method as recited in claim 17 , wherein the predefined transmit sequence is associated with a training sequence code.
19. The method as recited in claim 17 wherein hypothesizing the other received signal comprises:
convolving data d(k) with an estimated channel response (h eff ) to form d(k)*h eff as the hypothesized other received signal.
20. The method as recited in claim 19 wherein hypothesizing the other received signal further comprises:
decoding data bits associated with the first received signal; and
interleaving and modulating the decoded data bits to form the data d(k) corresponding to transmitted data.Cited by (0)
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