Iterative interference canceller for wireless multiple-access systems employing closed loop transmit diversity

A method of canceling interference from signals in a plurality of receive antennas received from a plurality of transmit antennas in a system wherein closed loop transmit waveform shaping is employed, the method comprising:

• providing for determining a set of dominant beamforming weights for transmit antennas of each of a plurality of transmit sources, wherein providing for determining the set of dominant beamforming weights comprises:
• providing for combining signals from the plurality of receive antennas for each of the plurality of transmit sources for producing a plurality of combined signals,
• providing for despreading by employing the set of dominant beamforming weights and resolving the plurality of combined signals onto a signal basis for the plurality of transmit sources to produce soft symbol estimates, and
• providing for performing a mixed decision on each of the soft symbol estimates to produce initial symbol decisions.

A system configured for canceling interference from signals in a plurality of receive antennas received from a plurality of transmit antennas wherein closed loop transmit waveform shaping is employed, the system comprising:

• a calculation means configured for determining a set of dominant beamforming weights for transmit antennas of each of a plurality of transmit sources, the calculation means comprising:
• a combining means for combining signals from the plurality of receive antennas for each of the plurality of transmit sources for producing a plurality of combined signals,
• a despreading means configured for employing the set of dominant beamforming weights to resolve the plurality of combined signals onto a signal basis for the plurality of transmit sources to produce soft symbol estimates, and
• a mixed-decision means for performing a mixed decision on each of the soft symbol estimates to produce initial symbol decisions.

An interference canceller coupled to a plurality of receive antennas configured for receiving signals from a plurality of transmit antennas in a system wherein closed loop transmit waveform shaping is employed, the interference canceller comprising:

• a front-end module configured for determining a set of dominant beamforming weights for transmit antennas of each of a plurality of transmit sources, the front-end module further configured for generating initial symbol decisions, and
• a sequence of interference-cancellation units configured for processing the initial symbol decisions;
• each of the sequence of interference-cancellation units comprising:
• a weighting module configured for applying weights to a plurality of input symbol decisions to produce weighted symbol decisions,
• a synthesis block configured for processing the weighted symbol decisions and the set of dominant beamforming weights for generating synthesized constituent signals for each of the plurality of receive antennas,
• a subtraction module configured for subtracting the synthesized constituent signals from the received signal to produce residual signals,
• a step-size module configured for scaling the residual signals by a stabilizing step size for producing scaled residual signals,
• a combining module configured for combining the synthesized constituent signals with the scaled residual signals to produce interference-cancelled constituents,
• a despreading module configured for employing the set of dominant beamforming weights and resolving the interference-cancelled constituents onto a signal basis for the plurality of transmit sources to produce soft symbol estimates, and
• a mixed-decision module configured for performing a mixed decision on each of the soft symbol estimates to produce updated symbol decisions.

An interference cancellation method for processing signals from a plurality of receive antennas configured for receiving signals from a plurality of transmit antennas in a system wherein closed loop transmit waveform shaping is employed, the method comprising:

• providing for determining a set of dominant beamforming weights for transmit antennas of each of a plurality of transmit sources, and generating initial symbol decisions, and
• providing for sequential interference cancellation for processing the initial symbol decisions;
• whereby providing for sequential interference cancellation comprises:
• providing for applying weights to a plurality of input symbol decisions to produce weighted symbol decisions,
• providing for processing the weighted symbol decisions and the set of dominant beamforming weights for generating synthesized constituent signals for each of the plurality of receive antennas,
• providing for subtracting the synthesized constituent signals from the received signal to produce residual signals,
• providing for scaling the residual signals by a stabilizing step size for producing scaled residual signals,
• providing for combining the synthesized constituent signals with the scaled residual signals to produce interference-cancelled constituents,
• providing for despreading by employing the set of dominant beamforming weights and resolving the interference-cancelled constituents onto a signal basis for the plurality of transmit sources to produce soft symbol estimates, and
• providing for performing a mixed decision on each of the soft symbol estimates to produce updated symbol decisions.

An interference cancellation system for processing signals from a plurality of receive antennas configured for receiving signals from a plurality of transmit antennas in a system wherein closed loop transmit waveform shaping is employed, the system comprising:

• a calculation means configured for determining a set of dominant beamforming weights for transmit antennas of each of a plurality of transmit sources, and generating initial symbol decisions, and
• a sequential interference cancellation means configured for processing the initial symbol decisions;
• sequential interference cancellation means comprising:
• a weighting means configured for applying weights to a plurality of input symbol decisions to produce weighted symbol decisions,
• a synthesizing means configured for processing the weighted symbol decisions and the set of dominant beamforming weights for generating synthesized constituent signals for each of the plurality of receive antennas,
• a subtraction means configured for subtracting the synthesized constituent signals from the received signal to produce residual signals,
• a stabilizing step size means configured for scaling the residual signals by a stabilizing step size for producing scaled residual signals,
• a combining means configured for combining the synthesized constituent signals with the scaled residual signals to produce interference-cancelled constituents,
• a despreading means configured for employing the set of dominant beamforming weights and resolving the interference-cancelled constituents onto a signal basis for the plurality of transmit sources to produce soft symbol estimates, and
• a mixed-decision means configured for performing a mixed decision on each of the soft symbol estimates to produce updated symbol decisions.

An interference canceller coupled to a plurality of receive antennas configured for receiving signals from a plurality of transmit antennas in a system wherein closed loop transmit waveform shaping is employed, the interference canceller comprising:

• a front-end module configured for determining a set of dominant beamforming weights for transmit antennas of each of a plurality of transmit sources, the front-end module further configured for generating initial symbol decisions, and
• a sequence of interference-cancellation units configured for processing the initial symbol decisions;
• each of the sequence of interference-cancellation units comprising:
• a weighting module configured for applying soft weights to a plurality of input symbol decisions,
• a mixed decision module configured for performing mixed decisions on soft symbol estimates, and
• a step-size module configured to scale a residual signal with a stabilizing step size, the step-size module further configured to produce the stabilizing step size with a magnitude representing how far the input symbol decisions are from desired interference-cancelled symbol decisions in a step of iterative interference cancellation.

A method for canceling interference in signals from a plurality of receive antennas configured for receiving transmissions from a plurality of transmit antennas in a system wherein closed loop transmit waveform shaping is employed, the method comprising:

• providing for front-end processing for determining a set of dominant beam forming weights for transmit antennas of each of a plurality of transmit sources, and generating initial symbol decisions, and
• providing for performing sequential interference cancellation on the initial symbol decisions;
• performing sequential interference cancellation comprising:
• providing for applying soft weights to a plurality of input symbol decisions for producing soft symbol estimates,
• providing for performing mixed decisions on the soft symbol estimates, and
• providing for scaling a residual signal with a stabilizing step size, the step-size having a magnitude representing how far the input symbol decisions are from desired interference-cancelled symbol decisions in a step of iterative interference cancellation.

A system configured for canceling interference in signals from a plurality of receive antennas receiving transmissions from a plurality of transmit antennas in a system wherein closed loop transmit waveform shaping is employed, the system comprising:

• a front-end processing means configured for determining a set of dominant beamforming weights for transmit antennas of each of a plurality of transmit sources and generating initial symbol decisions, and
• a sequential interference cancellation means configured for operating on the initial symbol decisions;
• the sequential interference cancellation means comprising:
• a soft-weighting means configured for applying soft weights to a plurality of input symbol decisions for producing soft symbol estimates,
• a mixed-decision means configured for performing mixed decisions on the soft symbol estimates, and
• a stabilizing step size means configured for scaling a residual signal with a stabilizing step size, the step-size having a magnitude representing how far the input symbol decisions are from desired interference-cancelled symbol decisions in a step of iterative interference cancellation.