Method and apparatus for selectively applying interference cancellation in spread spectrum systems

A method for selecting signal paths for cancellation from a signal stream provided to a demodulating processor, comprising:

• in a first mode:
• determining that cancellation of a potentially interfering signal path does not increase a signal strength of a desired signal path;
• providing a raw signal stream to a first demodulating processor. in a second mode:
• determining that cancellation of a potentially interfering signal path does increase a signal strength of a desired signal path;
• and
• providing a signal stream from which said potentially interfering signal stream has been removed to said first demodulating processor.

A set of data structures for use in identifying a potentially interfering signal path, comprising:

• a demodulating finger identifier;
• a signal path assigned to each demodulating finger identifier;
• and
• a signal strength associated with each signal path.

A method for selectively enabling signal interference cancellation, comprising:

• identifying at least one signal path in a set of signal paths;
• for the at least one signal, determining an observed signal strength;
• and
• identifying at least one of said signal paths as a potential interferer based at least in part on the observed signal strength.

A method for selectively enabling signal interference cancellation, comprising:

• providing a set of signal paths comprising at least one desired signal path;
• identifying at least one signal path in the set of signal paths as a potential interferer with the desired signal path;
• determining whether removing the at least one signal path in the set of signal paths will improve a signal to noise ratio (SNR) of the desired signal path by at least a selected threshold;
• and
• when the SNR of the desired signal path is improved by at least the selected threshold, removing the at least one signal from the signal stream to form an interference canceled signal stream.

A method for selecting a signal path for interference cancellation, comprising:

• comparing a candidate to cancel list with a to cancel list, wherein each of the candidate to cancel list and to cancel list comprise at least a finger identifier and a signal identifier of an interfering signal path;
• replacing any entry on the to cancel list with each entry in the candidate to cancel list that is not on the to cancel list;
• and
• updating a signal strength of each entry on both the to cancel and candidate to cancel lists with a signal strength on the candidate to cancel list.

A method for selecting a signal path for interference cancellation, comprising:

• identifying at least one potentially interfering signal path;
• searching an interference cancelled signal stream, from which the potentially interfering signal path has been removed, for each PN offset having a corresponding signal path possessing at least one of (a) a strength above a selected threshold and (b) a signal-to-noise improvement above a selected threshold;
• and
• providing said interference cancelled signal stream to each demodulating finger assigned to each PN offset having at least one of (a) and (b).

A method for performing interference cancellation, comprising:

• providing a plurality of fingers, each finger corresponding to a unique signal path;
• providing a plurality of differing signal streams, at least some of which are interference cancelled;
• for each finger, determining which of the plurality of differing signal streams provides a strongest desired signal path;
• and
• directing the appropriate signal stream to each finger.

A communications apparatus comprising:

• means for receiving a raw signal stream;
• means for demodulating a plurality of signal paths included in said raw signal stream;
• means for canceling at least a first of said signal paths from said raw signal stream to form at least a first interference cancelled signal stream;
• and
• means for selectively providing one of said raw signal stream and said interference cancelled signal stream to said means for demodulating.

A receiver configured for processing a raw signal stream, comprising:

• a plurality of demodulation fingers;
• a cancellation controller operable to selectively provide either or both of the raw signal stream and at least one interference cancelled signal stream to the plurality of demodulation fingers;
• and
• at least one cancellation module configured with the cancellation controller and operable to remove at least one replica of an interfering signal path from the raw signal stream to generate one of the at least one interference cancelled signal streams.