Interference cancellation method and apparatus
First Claim
1. Apparatus for processing an interference-corrupted signal representing a plurality of data signal values, said interference-corrupted signal having a frequency spectrum Y(ω
- )=|Y(ω
)|ejθ
.sbsp.Y.sup.(.omega.), said apparatus comprisingmeans for generating in response to said interference-corrupted signal a phase-compensated signal whose frequency spectrum is a function of |Y(ω
)| and is substantially independent of θ
Y (ω
),canceller means for forming in response to a stream of tentative decisions as to said signal values a cancellation signal representing the interference in said phase-compensated signal, said tentative decisions having been formed in response to said interference-corrupted signal, andmeans for forming a stream of final decisions as to said signal values in response to said phase-compensated and cancellation signals.
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Accused Products
Abstract
Weighted sums of samples of an interference-corrupted data signal are generated to form phase-compensated, symbol-spaced samples. The interference-corrupted signal is at the same time subjected to conventional adaptive equalization and is otherwise processed so as to form tentative decisions as to the transmitted data. Cancellation signals representing the interference components of the phase-compensated samples are generated by forming respective weighted sums of the tentative decisions and each cancellation signal is combined with a respective phase-compensated sample to provide cancelled samples from which final data decisions are made. The weighting coefficients used to form the phase-compensated samples and the cancellation signals are adaptively updated in response to error signals derived from the difference between each cancelled sample and the corresponding final decision.
40 Citations
47 Claims
-
1. Apparatus for processing an interference-corrupted signal representing a plurality of data signal values, said interference-corrupted signal having a frequency spectrum Y(ω
- )=|Y(ω
)|ejθ
.sbsp.Y.sup.(.omega.), said apparatus comprisingmeans for generating in response to said interference-corrupted signal a phase-compensated signal whose frequency spectrum is a function of |Y(ω
)| and is substantially independent of θ
Y (ω
),canceller means for forming in response to a stream of tentative decisions as to said signal values a cancellation signal representing the interference in said phase-compensated signal, said tentative decisions having been formed in response to said interference-corrupted signal, and means for forming a stream of final decisions as to said signal values in response to said phase-compensated and cancellation signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- )=|Y(ω
-
10. Apparatus for processing an interference-corrupted signal representing a plurality of data signal values, said apparatus comprising
means for generating baseband phase-compensated samples each of which is equal to a baseband weighted combination of samples derived from said interference-corrupted signal, means for forming in response to said interference-corrupted signal a plurality of tentative decisions as to said data signal values, canceller means for forming cancellation signals each of which is equal to a weighted combination of said tentative decisions, and means for forming a plurality of final decisions as to said data signal values in response to said baseband phase-compensated samples and said cancellation signals.
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16. Apparatus for processing a signal received from a transmission channel, said signal representing a plurality of data signal values, and said signal including interference resulting from phase and amplitude distortion in said channel, said apparatus comprising
means for generating samples of said received signal from which the interference due to said phase distortion has been substantially removed, canceller means for forming in response to tentative decisions as to said data signal values cancellation signals each of which is substantially equal to the interference in a respective one of said phase-distortion-removed samples, and means for forming final decisions as to said data signal values in response to said phase-distortion-removed samples and said cancellation signals.
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22. Apparatus for processing an interference-corrupted passband signal representing a plurality of complex signal values transmitted at a T-second baud rate and with a carrier frequency ω
-
o, said apparatus comprising
means for forming in response to said interference-corrupted signal complex tentative decisions Am-M as to said signal values, m being an index which advances at the baud rate and M being a selected integer, cancelled sample forming means for forming complex cancelled samples Pm substantially given by Pm =(Um -Vm), where ##EQU9## the Wk (m)'"'"'s are a first ensemble of complex weighting coefficients, the Y2m-k '"'"'s are samples derived from said received signal, L is a selected integer, θ
m is a carrier phase estimate, and the Ck (m)'"'"'s are a second ensemble of complex weighting coefficients, andmeans for forming final decisions Am as to said signal values in response to said cancelled samples. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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26. The invention of claim 22, 23, 24 or 25 wherein said cancelled sample forming means generates the values of the Ck (m)'"'"'s in response to error signals which are functions of said cancelled samples and selected ones of said tentative and final decisions.
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27. The invention of claim 24 or 25 wherein said cancelled samples forming means generates the values of the Ck (m)'"'"'s in accordance with ##EQU11## where α
- is a selected step size, δ
1 is a selected leakage term, the ε
m '"'"'s are complex error signals and d1 is a selected integer including zero.
- is a selected step size, δ
-
28. The invention of claim 27 wherein said error signals ε
-
m are substantially equal to
space="preserve" listing-type="equation">ε
.sub.m =±
(P.sub.m -A.sub.m).
-
m are substantially equal to
-
o, said apparatus comprising
-
29. A method for processing an interference-corrupted signal representing a plurality of data signal values, said interference-corrupted signal having a frequency spectrum Y(ω
- )=|Y(ω
)|ejθ
.sbsp.Y.sup.(.omega.), said method comprising the steps ofgenerating in response to said interference-corrupted signal a phase-compensated signal whose frequency spectrum is a function of |Y(ω
)| and is substantially independent of θ
Y (ω
),forming in response to a plurality of tentative decisions as to said signal values a cancellation signal representing the interference in said phase-compensated signal, said tentative decisions having been formed in response to said interference-corrupted signal, and forming a plurality of final decisions as to said signal values in response to said phase-compensated and cancellation signals. - View Dependent Claims (30, 31)
- )=|Y(ω
-
32. The invention of claim 32 wherein said weighting coefficients are updated in accordance with a stochastic gradient criterion.
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33. A method for processing an interference-corrupted signal representing a plurality of data signal values, said method comprising the steps of
generating baseband phase-compensated samples each of which is equal to a baseband weighted combination of samples derived from said interference-corrupted signal, forming in response to said interference-corrupted signal tentative decisions as to said data signal values, forming cancellation signals each of which is equal to a weighted combination of said tentative decisions, and forming final decisions as to said data signal values in response to said baseband phase-compensated samples and said cancellation signals.
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36. A method for processing a signal received from a transmission channel, said signal representing a plurality of data signal values, and said signal including interference resulting from phase and amplitude distortion in said channel, said method comprising the steps of
generating samples of said received signal from which the interference due to said phase distortion has been substantially removed, forming in response to tentative decisions as to said data signal values cancellation signals each of which is substantially equal to the interference in a respective one of said phase-distortion-removed samples, and forming final decisions as to said data signal values in response to said phase-distortion-removed samples and said cancellation signals.
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41. A method for processing an interference-corrupted passband signal representing a plurality of complex signal values transmitted at a T-second baud rate and with a carrier frequency ω
-
o, said method comprising the steps of
forming in response to said interference-corrupted signal complex tentative decisions Am-M as to said signal values, m being an index which advances at the baud rate and M being a selected integer, forming complex cancelled samples Pm substantially given by Pm =(Um -Vm), where ##EQU12## the Wk (m)'"'"'s are a first ensemble of complex weighting coefficients, the Y2m-k '"'"'s are samples derived from said received signal, L is a selected integer, θ
m is a carrier phase estimate, and the Ck (m)'"'"'s are a second ensemble of complex weighting coefficients, andforming final decisions Am as to said signal values in response to said cancelled samples. - View Dependent Claims (42, 43, 44, 45, 46, 47)
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45. The invention of claim 41, 42, 43 or 44 wherein the values of the Ck (m)'"'"'s are generated in response to error signals which are functions of said cancelled samples and selected ones of said tentative and final decisions.
-
46. The invention of claim 43 or 44 wherein the values of the Ck (m)'"'"'s are generated in accordance with ##EQU14## where α
- is a selected step size, δ
1 is a selected leakage term, the ε
m '"'"'s are the complex error signals and d1 is a selected integer including zero.
- is a selected step size, δ
-
47. The invention of claim 46 wherein said error signals ε
-
m are substantially equal to ε
m =±
(Pm -Am).
-
m are substantially equal to ε
-
o, said method comprising the steps of
Specification