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

Abstract

An interference-canceling receiver processes coded, multiple-access, spread-spectrum transmissions that propagate through frequency-selective communication channels from multiple transmit antennas to multiple receive antennas in a closed-loop transmit-diversity channel. The receiver provides for repeated use of symbol-estimate weighting, subtractive cancellation with a stabilizing step-size, and mixed-decision symbol estimation. Receivers may be designed, adapted, and implemented explicitly in software or programmed hardware, or implicitly in standard Rake-based hardware, either within a Rake receiver at the finger level or outside the Rake at the user or subchannel symbol level. The receiver may be employed in user equipment on the forward link or in a base station on the reverse link.

1 . 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 comprising,   a combiner configured 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 module configured for 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   a mixed-decision module configured for performing a mixed decision on each of the soft symbol estimates to produce initial symbol decisions.