Parallel interference cancellation for CDMA applications
First Claim
1. A method of decoding a spread spectrum composite signal, said composite signal comprising plural user signals that have been spread with plural respective codes, wherein each user signal is despread, filtered to produce a signal value, analyzed to produce a tentative decision value, respread, summed with other respread signals to produce combined interference signals, said method comprising:
- scaling one of said combined interference signals with a weighting factor to produce a scaled combined interference signal;
scaling said composite signal with said weighting factor to produce a scaled composite signal;
scaling one of said signal value by the complement of said weighting factor to produce a leakage signal; and
combining said scaled composite signal with a scaled combined interference signal and a corresponding leakage signal to produce an estimate of a respective user signal.
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Abstract
The present invention provides a method of decoding a spread spectrum composite signal, the composite signal comprising plural user signals that have been spread with plural respective codes, wherein each coded signal is despread, averaged to produce a signal value, analyzed to produce a tentative decision, respread, summed with other respread signals to produce combined interference signals, the method comprising scaling the combined interference signals with a weighting factor to produce a scaled combined interference signal, scaling the composite signal with the weighting factor to produce a scaled composite signal, scaling the signal value by the complement of the weighting factor to produce a leakage signal, combining the scaled composite signal, the scaled combined interference signal and the leakage signal to produce an estimate of a respective user signal.
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Citations
35 Claims
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1. A method of decoding a spread spectrum composite signal, said composite signal comprising plural user signals that have been spread with plural respective codes, wherein each user signal is despread, filtered to produce a signal value, analyzed to produce a tentative decision value, respread, summed with other respread signals to produce combined interference signals, said method comprising:
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scaling one of said combined interference signals with a weighting factor to produce a scaled combined interference signal; scaling said composite signal with said weighting factor to produce a scaled composite signal; scaling one of said signal value by the complement of said weighting factor to produce a leakage signal; and combining said scaled composite signal with a scaled combined interference signal and a corresponding leakage signal to produce an estimate of a respective user signal. - View Dependent Claims (2)
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3. A method of decoding a spread spectrum composite signal in successive stages, said composite signal comprising plural user signals that have been spread with plural respective codes, wherein in each of said stages each user signal is despread, filtered to produce a signal value, analyzed to produce a tentative decision value, respread, summed with other respread signals to produce combined interference signals, said method carried out in each of said successive stages comprising:
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scaling one of said combined interference signals with a weighting factor to produce a scaled combined interference signal; scaling said composite signal with said weighting factor to produce a scaled composite signal; scaling one of said signal values by the complement of said weighting factor to produce a leakage signal; and combining said scaled composite signal with a scaled combined interference signal and a corresponding leakage signal to produce an estimate of a respective user signal. - View Dependent Claims (4, 5)
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6. A method of decoding a spread spectrum composite signal, said composite signal comprising plural user signals that have been spread with plural respective codes, said method comprising a plurality of interference cancellation steps performed in succession, wherein each step comprises the performance for each one of said user signals of the following substeps:
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despreading said composite signal to produce a despread signal corresponding to each user signal; filtering each despread signal to produce a signal value for each user signal; analyzing each signal value to produce an information signal for each user signal; respreading each information signal to produce an interference signal for each user signal; summing at least the interference signals corresponding to user signals other than said one user signal to produce a combined interference signal; scaling said combined interference signal with a weighting factor to produce a scaled combined interference signal; scaling said composite signal with said weighting factor to produce a scaled composite signal; scaling said signal value by the complement of said weighting factor to produce a leakage signal; and combining said scaled composite signal, said scaled combined interference signal and said leakage signal to produce an estimate of said one user signal. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of decoding a spread spectrum composite signal, said composite signal comprising plural user signals that have been spread with plural respective codes, wherein each user signal is despread, filtered to produce a signal value, analyzed to produce a tentative decision value, respread, summed with all other respread signals to produce combined interference signals, comprising:
combining a portion of each signal value with one of said combined interference signals and said composite signal to produce an estimate of a respective user signal whereby to preserve information contained in said user signal. - View Dependent Claims (17, 18, 19)
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20. An apparatus for decoding a spread spectrum composite signal, said composite signal comprising plural user signals that have been spread with plural respective codes, wherein each user signal is despread, filtered to produce a signal value, analyzed to produce a tentative decision value, respread, summed with other respread signals to produce combined interference signals, comprising:
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means for scaling one of said combined interference signals with a weighting factor to produce a scaled combined interference signal; means for scaling said composite signal with said weighting factor to produce a scaled composite signal; means for scaling one of said signal value by the complement of said weighting factor to produce a leakage signal; and means for combining said scaled composite signal with scaled combined interference signal and a corresponding leakage signal to produce an estimate of a respective user signal. - View Dependent Claims (21)
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22. An apparatus for decoding a spread spectrum composite signal in successive stages, said composite signal comprising plural user signals that have been spread with plural respective codes, wherein in each of said stages each user signal is despread, filtered to produce a signal value, analyzed to produce a tentative decision value, respread, summed with other respread signals to produce combined interference signals, each of said successive stages comprising:
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means for scaling one of said combined interference signals with a weighting factor to produce a scaled combined interference signal; means for scaling said composite signal with said weighting factor to produce a scaled composite signal; means for scaling one of said signal value by the complement of said weighting factor to produce a leakage signal; and means for combining said scaled composite signal with a scaled combined interference signal and a corresponding leakage signal to produce an estimate of a respective user signal. - View Dependent Claims (23, 24)
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25. An apparatus for decoding a spread spectrum composite signal, said composite signal comprising plural user signals that have been spread with plural respective codes, said apparatus comprising a plurality of successive interference cancellation stages, wherein each stage comprises for each one of said user signals:
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means for despreading said composite signal to produce a despread signal corresponding to each user signal; means for filtering said despread signal to produce a signal value for each user signal; means for analyzing each signal value to produce an information signal for each user signal; means for respreading each information signal to produce an interference signal for each user signal; means for summing at least the interference signals corresponding to user signals other than said one user signal to produce a combined interference signal; means for scaling said combined interference signal with a weighting factor to produce a scaled combined interference signal; means for scaling said composite signal with said weighting factor to produce a scaled composite signal; means for scaling said signal value by the complement of said weighting factor to produce a leakage signal; and means for combining said scaled composite signal, said scaled combined interference signal and said leakage signal to produce an estimate of said one user signal. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. An apparatus for decoding a spread spectrum composite signal, said composite signal comprising plural user signals that have been spread with plural respective codes, wherein each user signal is despread, filtered to produce a signal value, analyzed to produce a tentative decision value, respread, summed with all other respread signals to produce combined interference signals, comprising:
a combiner for combining a portion of each signal value with said combined interference signals and said composite signal to produce an estimate of a respective user signal whereby a portion of information contained in said user signal is preserved.
Specification