Inter-symbol interference cancellation for wireless multiple access
First Claim
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1. An interference canceller for cancelling inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal, comprising:
- a post-cursor ISI synthesis module configured for synthesizing an estimated post-cursor ISI signal from post-cursor symbol estimates;
a post-cursor ISI cancellation module and a resolving module configured for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal;
an interference cancellation module configured for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and
a feedback loop configured for coupling the post-cursor symbol estimates to the post-cursor ISI synthesis module,whereby the post-cursor ISI synthesis module is further configured to receive as input a plurality of symbol estimates in a predetermined number of post-cursor symbol intervals, the post-cursor ISI synthesis module comprising;
a weighting module configured for weighting the plurality of symbol estimates according to symbol-estimate merits to produce weighted symbol estimates;
a code-waveform modulator configured for modulating the weighted symbol estimates onto corresponding code waveforms for producing modulated code waveforms and summing the modulated code waveforms to generate an estimated transmit signal; and
a channel emulator configured for imparting multipath delays and gains to the estimated transmit signal.
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Abstract
An interference-canceling receiver is configured for cancelling inter-symbol interference due to both inter- and intra-channel interference in coded, multiple-access, spread spectrum transmissions that propagate through frequency-selective communication channels. The receiver mitigates the effects of post-cursor inter-symbol interference using feedback of previously estimated symbols, and mitigates pre-cursor inter-symbol interference using an interference canceller, such as an iterative interference canceller.
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Citations
42 Claims
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1. An interference canceller for cancelling inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal, comprising:
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a post-cursor ISI synthesis module configured for synthesizing an estimated post-cursor ISI signal from post-cursor symbol estimates; a post-cursor ISI cancellation module and a resolving module configured for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal; an interference cancellation module configured for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and a feedback loop configured for coupling the post-cursor symbol estimates to the post-cursor ISI synthesis module, whereby the post-cursor ISI synthesis module is further configured to receive as input a plurality of symbol estimates in a predetermined number of post-cursor symbol intervals, the post-cursor ISI synthesis module comprising; a weighting module configured for weighting the plurality of symbol estimates according to symbol-estimate merits to produce weighted symbol estimates; a code-waveform modulator configured for modulating the weighted symbol estimates onto corresponding code waveforms for producing modulated code waveforms and summing the modulated code waveforms to generate an estimated transmit signal; and a channel emulator configured for imparting multipath delays and gains to the estimated transmit signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An interference canceller for cancelling inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal, comprising:
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a post-cursor ISI synthesis module configured for synthesizing an estimated post-cursor ISI signal from post-cursor symbol estimates; a post-cursor ISI cancellation module and a resolving module configured for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal; an interference cancellation module configured for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and a feedback loop configured for coupling the post-cursor symbol estimates to the post-cursor ISI synthesis module, whereby the interference cancellation module comprises, a symbol-estimation module configured for generating initial symbol estimates; a sequence of interference cancellation units, the sequence configured to receive the initial symbol estimates, each of the sequence of interference cancellation units configured to weight input symbol estimates with soft weighting, apply stabilizing step sizes to a difference signal, and perform mixed decisions to produce updated, interference-cancelled symbol estimates; and a partitioning module configured to output final updated, interference-cancelled symbol estimates for an on-cursor symbol interval. - View Dependent Claims (11, 12)
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13. An interference canceller for cancelling inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal, comprising:
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a post-cursor ISI synthesis module configured for synthesizing an estimated post-cursor ISI signal from post-cursor symbol estimates; a post-cursor ISI cancellation module and a resolving module configured for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal; an interference cancellation module configured for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and a feedback loop configured for coupling the post-cursor symbol estimates to the post-cursor ISI synthesis module, whereby the interference cancellation module is further configured for performing iterative pre-cursor ISI cancellation at the symbol level by employing a one-step matrix update equation, comprising an explicit matrix representation of a received-signal correlation matrix over multiple symbol intervals, an implementation matrix over multiple symbol intervals, a soft-weighting matrix, a scalar stabilizing step size, and a mixed decision symbol estimator. - View Dependent Claims (14)
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15. A method whereby inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal are cancelled, the method comprising:
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providing for synthesizing an estimated post-cursor ISI signal from post-cursor symbol estimates; providing for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal in which post-cursor ISI has been removed from the received signal; providing for performing interference cancellation for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and providing for feeding back the post-cursor symbol estimates to the step of providing for synthesizing an estimated post-cursor ISI signal, whereby providing for synthesizing is further configured to receive as input a plurality of symbol estimates in a predetermined number of post-cursor symbol intervals, providing for synthesizing comprising; providing for weighting the plurality of symbol estimates according to symbol-estimate merits to produce weighted symbol estimates; providing for modulating the weighted symbol estimates onto corresponding code waveforms for producing modulated code waveforms and summing the modulated code waveforms to generate an estimated transmit signal; and providing for performing channel emulation to impart multipath delays and gains to the estimated transmit signal. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. A method whereby inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal are cancelled, the method comprising:
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providing for synthesizing an estimated post-cursor ISI signal from post-cursor symbol estimates; providing for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal in which post-cursor ISI has been removed from the received signal; providing for performing interference cancellation for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and providing for feeding back the post-cursor symbol estimates to the step of providing for synthesizing an estimated post-cursor ISI signal, whereby providing for performing interference cancellation comprises, providing for generating initial symbol estimates; providing for a sequence of interference cancellation steps, the sequence configured to receive the initial symbol estimates, each of the sequence of interference cancellation steps configured to weight input symbol estimates with soft weighting, apply stabilizing step sizes to s difference signal, and perform mixed decisions to produce updated, interference-cancelled symbol estimates; and providing for outputting final updated, interference-cancelled symbol estimates for an on-cursor symbol interval. - View Dependent Claims (25, 26)
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27. A method whereby inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal are cancelled, the method comprising:
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providing for synthesizing an estimated post-cursor ISI signal from post-cursor symbol estimates; providing for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal in which post-cursor ISI has been removed from the received signal; providing for performing interference cancellation for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and providing for feeding back the post-cursor symbol estimates to the step of providing for synthesizing an estimated post-cursor ISI signal, whereby providing for performing interference cancellation is further configured for performing iterative pre-cursor ISI cancellation at the symbol level by employing a one-step matrix update equation, comprising an explicit matrix representation of a received-signal correlation matrix over multiple symbol intervals, an implementation matrix over multiple symbol intervals, a soft-weighting matrix, a scalar stabilizing step size, and a mixed decision symbol estimator. - View Dependent Claims (28)
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29. A system whereby inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal are cancelled, the system comprising:
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a post-cursor ISI synthesis means for synthesizing as estimated post-cursor ISI signal from post-cursor symbol estimates; a post cursor ISI cancellation means and a resolving means for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal; an interference cancellation means for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and a feedback means for coupling the post-cursor symbols estimates to the post-cursor ISI synthesis means, whereby the post-cursor ISI synthesis means is configured to receive as input a plurality of symbols estimates in a predetermined number of post-cursor symbol intervals, the post-cursor ISI synthesis means comprising; a weighting means for weighting the plurality of symbol estimates according to symbol-estimates merits to produce weighted symbol estimates; a code-waveform modulation means for modulation the weighted symbol estimates onto corresponding code waveforms for producing modulated code waveforms and summing the modulated code waveforms to generate an estimated transmit signal; and a channel-emulation means for imparting multipath delays and gains to the estimated transmit signal. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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38. A system whereby inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal are cancelled, the system comprising:
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a post-cursor ISI synthesis means for synthesizing as estimated post-cursor ISI signal from post-cursor symbol estimates; a post cursor ISI cancellation means and a resolving means for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal; an interference cancellation means for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and a feedback means for coupling the post-cursor symbols estimates to the post-cursor ISI synthesis means, whereby the interference cancellation means comprises, a symbol-estimation means for generating initial symbol estimates; a sequential interference cancellation means for receiving the initial symbol estimates, the sequential interference cancellation means configured to weight input symbol estimates with soft weighting, apply stabilizing step sizes to a difference signal, and perform mixed decisions to produce updated, interference-cancelled symbol estimates; and a partitioning means configured for outputting final updated, interference-cancelled symbol estimates for an on-cursor symbol interval. - View Dependent Claims (39, 40)
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41. A system whereby inter-symbol interference (ISI), intra-cell interference, and inter-cell interference in a multiple-access communication signal are cancelled, the system comprising:
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a post-cursor ISI synthesis means for synthesizing as estimated post-cursor ISI signal from post-cursor symbol estimates; a post cursor ISI cancellation means and a resolving means for processing the estimated post-cursor ISI signal and the received signal to produce a first interference-canceled signal; an interference cancellation means for cancelling pre-cursor inter-symbol interference, intra-cell interference, and inter-cell interference from the first interference-cancelled signal for producing interference-cancelled symbol estimates and the post-cursor symbol estimates; and a feedback means for coupling the post-cursor symbols estimates to the post-cursor ISI synthesis means, whereby the interference cancellation means is further configured for performing iterative pre-cursor ISI cancellation at symbol level by employing a one-step matrix update equation, comprising an explicit matrix representation of a received-signal correlation matrix over multiple symbol intervals, an implementation matrix over multiple symbol intervals, a soft-weighting matrix, a scalar stabilizing step size, and a mixed symbol estimator. - View Dependent Claims (42)
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Specification