Method and apparatus for selectively applying interference cancellation in spread spectrum systems
The present invention is directed to the selective provision of interference canceled signal streams to demodulating fingers in a communication receiver. According to the present invention, potential interferer signal paths are identified. Signal streams having one or more potential interferer signals removed or canceled are created, and a correlation is performed to determine whether the strength of a desired signal path increased as a result. If the correlation indicates that the strength of a desired signal path was increased by the signal cancellation, the interference canceled signal stream is provided to the demodulation finger assigned to track the desired signal path. If the correlation determines that the strength of the desired signal path did not increase as a result of performing interference cancellation, the raw or a different interference canceled signal stream is provided to the demodulation finger.
1. An apparatus comprising:
a plurality of demodulation fingers, wherein each of the plurality of demodulation fingers includes an input; and
a cancellation controller configured to selectively provide:
in a first mode, an interference-cancelled signal stream to the inputs of the plurality of demodulation fingers; and
in a second mode, a non-interference-cancelled signal stream to the inputs of the plurality of demodulation fingers.
2. The apparatus of claim 1 , further comprising:
a searcher finger, wherein the cancellation controller is configured to selectively provide one of the interference-cancelled signal stream or the non-interference-cancelled signal stream to the searcher finger.
3. The apparatus of claim 1 , wherein the cancellation controller comprises:
a channel determination module configured to provide at least one replica of an interfering signal path; and
a signal cancellation module operable to remove the at least one replica of the interfering signal path from another signal stream.
4. The apparatus of claim 3 , wherein the cancellation controller further comprises:
a plurality of channel determination modules, each of which is configured to provide the replica of the interfering signal path; and
a plurality of signal cancellation modules, each of which is configured to remove the at least one replica of the interfering signal path from another signal stream.
5. The apparatus of claim 4 , wherein the number of demodulation fingers is greater than the number of channel determination modules.
6. The apparatus of claim 4 , wherein the number of demodulation fingers, the number of channel determination modules, and the number of signal cancellation modules are equal.
7. The apparatus of claim 1 , wherein each of the plurality of demodulation fingers comprises a tracking module and a demodulation module.