Successive interference canceling for CDMA

Details Successive interference canceling for CDMA Successive interference canceling for CDMA

2006-11-27

2009-10-06

Phu, Phuong (Department: 2611)

Pulse or digital communications

Spread spectrum

Direct sequence

C375S144000, C375S346000, C375S350000, C375S232000

Reexamination Certificate

active

07599423

ABSTRACT:
Successive interference canceling for CDMA. ICI may result from a signal's multi-path effects, or by filtering/suppression of some of the component energy of the signaling waveforms. Energy component attenuation destroys orthogonality of CDMA symbols thereby causing ICI. An ICF suppresses frequency domain portions(attenuates ingress), but also introduces ICI. Following the ICF, the signal is de-spread sliced, re-spread and convolved with the ICF echoes (except first tap echoes). Convolving re-spread hard decisions with delayed ICF taps is equivalent to partially re-modulating the first-pass hard decisions to efficiently “add-back-in” the signal energy which was blanked/subtracted by the ICF. Alternatively, parameter estimation de-rotates and re-rotates soft symbols and hard decisions, respectively, compensating for undesirable symbol rotation. The convolved signal is subtracted from a delayed version of the ICF output signal. If desired, this process may be repeated successively to enhance the accuracy of the obtained data decisions in the next stage.

REFERENCES:
patent: 5467368 (1995-11-01), Takeuchi et al.
patent: 5719852 (1998-02-01), Schilling et al.
patent: 6088383 (2000-07-01), Suzuki et al.
patent: 6363103 (2002-03-01), Buehrer et al.
patent: 7190710 (2007-03-01), Yousef et al.

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