Iterative interference cancellation for MIMO-OFDM receivers
First Claim
1. An iterative interference canceller comprising:
- a soft-weighting module configured for applying soft weights to each of a plurality of input symbol estimates for an initial iteration, and to each of a plurality of updated symbol estimates for at least one subsequent iteration for producing a plurality of weighted symbol estimates,a channel-mapping module configured for synthesizing constituent signals from the plurality of weighted symbol estimates, and producing a combined signal therefrom,a subtraction module configured for subtracting the combined signal from a received signal to produce an error signal,a stabilizing step size module configured for scaling the error signal by a stabilizing step size to produce a scaled error signal,a channel-matching module configured for resolving the scaled error signal onto user space-frequency channel mapping functions to produce interference-cancelled symbol estimates, anda mixed-decision module configured for performing a mixed decision comprising a hard decision or a soft decision on each of the interference-cancelled symbol estimates to produce the plurality of updated symbol estimates;
wherein the canceller is employed in a space-time multiplexed receiver whereby a plurality of streams of independently encoded data in a received signal employing a common set of transmit antennas and temporal subbands are separated, andwhereby the channel-mapping module and the channel-matching module are further configured to process frequency correlations introduced by transmitter space-frequency mapping.
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Abstract
An OFDMA-MIMO receiver performs a recursive interference cancellation across several correlated subbands and several receive antenna elements to demodulate complex source symbols for several users that have been coded across several subbands and transmit antennas. The iterative parallel interference canceller (PIC) is configured to work in the presence of both spatial and frequency structure introduced by the transmitter space-frequency mapping and the actual frequency selective wireless channel. The interference canceller uses mixed decisions, confidence weights, and stabilizing step sizes in a PIC receiver, which may be used with a successive decoding architecture in a receiver that employs a combination of modulation level interference cancellation with successive decoding.
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Citations
30 Claims
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1. An iterative interference canceller comprising:
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a soft-weighting module configured for applying soft weights to each of a plurality of input symbol estimates for an initial iteration, and to each of a plurality of updated symbol estimates for at least one subsequent iteration for producing a plurality of weighted symbol estimates, a channel-mapping module configured for synthesizing constituent signals from the plurality of weighted symbol estimates, and producing a combined signal therefrom, a subtraction module configured for subtracting the combined signal from a received signal to produce an error signal, a stabilizing step size module configured for scaling the error signal by a stabilizing step size to produce a scaled error signal, a channel-matching module configured for resolving the scaled error signal onto user space-frequency channel mapping functions to produce interference-cancelled symbol estimates, and a mixed-decision module configured for performing a mixed decision comprising a hard decision or a soft decision on each of the interference-cancelled symbol estimates to produce the plurality of updated symbol estimates; wherein the canceller is employed in a space-time multiplexed receiver whereby a plurality of streams of independently encoded data in a received signal employing a common set of transmit antennas and temporal subbands are separated, and whereby the channel-mapping module and the channel-matching module are further configured to process frequency correlations introduced by transmitter space-frequency mapping. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 16)
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9. An iterative interference cancellation method comprising:
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providing for applying a soft weight to each of a plurality of input symbol estimates for an initial iteration, and to each of a plurality of updated symbol estimates for at least one subsequent iteration for producing a plurality of weighted symbol estimates, providing for channel mapping the plurality of weighted symbol estimates to synthesize constituent signals, and producing a combined signal therefrom, providing for subtracting the combined signal from a received signal to produce an error signal, providing for scaling the error signal by a stabilizing step size to produce a scaled error signal, providing for channel matching the scaled error signal onto user space-frequency channel mapping functions to produce interference-cancelled symbol estimates, and providing for performing a mixed decision comprising a hard decision or a soft decision on each of the interference-cancelled symbol estimates to produce the plurality of updated symbol estimates, whereby providing for channel mapping and providing for channel matching further comprises processing frequency correlations introduced by transmitter space-frequency mapping. - View Dependent Claims (10, 11, 12, 13, 14)
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15. An iterative interference cancellation method comprising:
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providing for applying a soft weight to each of a plurality of input symbol estimates for an initial iteration, and to each of a plurality of updated symbol estimates for at least one subsequent iteration for producing a plurality of weighted symbol estimates, providing for channel mapping the plurality of weighted symbol estimates to synthesize constituent signals, and producing a combined signal therefrom, providing for subtracting the combined signal from a received signal to produce an error signal, providing for scaling the error signal by a stabilizing step size to produce a scaled error signal, providing for channel matching the scaled error signal onto user space-frequency channel mapping functions to produce interference-cancelled symbol estimates, and providing for performing a mixed decision comprising a hard decision or a soft decision on each of the interference-cancelled symbol estimates to produce the plurality of updated symbol estimates, wherein the method is employed with a plurality of streams of independently encoded data in a received space-time multiplexed signal employing a common set of transmit antennas and temporal subbands and wherein said streams of independently encoded data are separated, whereby providing for channel mapping and providing for channel matching further comprises processing spatial and temporal structure introduced by a transmitter space-time mapping and a frequency-selective wireless channel. - View Dependent Claims (17, 18)
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19. A space-frequency receiver configured to separate a plurality of streams of independently encoded data in a received signal employing a common set of transmit antennas and frequency subbands, the space-frequency receiver comprising:
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an iterative interference canceller configured to process an input signal comprising a plurality of independently encoded data streams, the iterative interference canceller comprising; a soft-weighting module configured for applying soft weights to each of a plurality of input symbol estimates for an initial iteration, and to each of a plurality of updated symbol estimates for at least one subsequent iteration for producing a plurality of weighted symbol estimates, a channel-mapping module configured for synthesizing constituent signals from the plurality of weighted symbol estimates, and producing a combined signal therefrom, a subtraction module configured for subtracting the combined signal from the received signal to produce an error signal, a stabilizing step size module configured for scaling the error signal by a stabilizing step size to produce a scaled error signal, a channel-matching module configured for resolving the scaled error signal onto user space-frequency channel mapping functions to produce interference-cancelled symbol estimates, and a mixed-decision module configured for performing a mixed decision comprising a hard decision or a soft decision on each of the interference-cancelled symbol estimates to produce the plurality of updated symbol estimates, and a successive decoder, comprising; a demapper and a decoder configured to process the plurality of updated symbol estimates for producing an estimated data stream for one of the plurality of independently encoded data streams, a synthesis module configured for re-encoding and remapping the estimated input information sequence for producing its estimated contribution to the received signal, and a second subtraction module configured for subtracting the estimated contribution from the received signal for producing an updated input signal comprising one less than the plurality of independently encoded data streams, for coupling back to the iterative interference canceller, wherein the iterative interference canceller is configurable for processing the updated input signal until the updated input signal comprises only one independently encoded data stream. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A space-time receiver configured to separate a plurality of streams of independently encoded data in a received signal employing a common set of transmit antennas and temporal subbands, the space-time receiver comprising:
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an iterative interference canceller configured to process an input signal comprising a plurality of independently encoded data streams, the iterative interference canceller comprising; a soft-weighting module configured for applying soft weights to each of a plurality of input symbol estimates for an initial iteration, and to each of a plurality of updated symbol estimates for at least one subsequent iteration for producing a plurality of weighted symbol estimates, a channel-mapping module configured for synthesizing constituent signals from the plurality of weighted symbol estimates, and producing a combined signal therefrom, a subtraction module configured for subtracting the combined signal from the received signal to produce an error signal, a stabilizing step size module configured for scaling the error signal by a stabilizing step size to produce a scaled error signal, a channel-matching module configured for resolving the scaled error signal onto user space-time channel mapping functions to produce interference-cancelled symbol estimates, and a mixed-decision module configured for performing a mixed decision comprising a hard decision or a soft decision on each of the interference-cancelled symbol estimates to produce the plurality of updated symbol estimates, and a successive decoder, comprising; a demapper and a decoder configured to process the plurality of updated symbol estimates for producing an estimated data stream for one of the plurality of independently encoded data streams, a synthesis module configured for re-encoding and remapping the estimated input information sequence for producing its estimated contribution to the received signal, and a second subtraction module configured for subtracting the estimated contribution from the received signal for producing an updated input signal comprising one less than the plurality of independently encoded data streams, for coupling back to the iterative interference canceller, wherein the iterative interference canceller is configurable for processing the updated input signal until the updated input signal comprises only one independently encoded data stream. - View Dependent Claims (26, 27, 28, 29, 30)
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Specification