Simplified narrowband excision

Abstract

An improved ingress cancellation filter comprising a Fast Fourier Transform circuit which replaces the analysis filter bank of the prior art to break the incoming signal down into sub bands, an ingress cancellation filter that weights each sub band based upon the probability that the sub band is corrupted by noise, and an inverse Fast Fourier Transform circuit to put the weighted sub bands back together into an output signal and replacing the synthesis filter bank of the prior art. Also, an improved predictor filter which can be used with CDMA circuitry by initializing the predictor filter at the beginning of each spreading interval using the samples received on the first L unused codes of the spreading interval.

1 . A process for using a predictor filter to help eliminate noise from received samples in code division multiple access circuits, comprising the steps: 
 A) receiving a new sample in a predictor filter used in a code division multiple access circuit to predict the noise in the next received sample having an index beyond the index of samples in a first in, first out memory (FIFO) which comprise the state of said prediction filter, and throwing out the oldest sample;    B) determining if said new sample represents signal received on the first code of a new spreading interval as compared to the spreading interval of the next previous sample received;    C) if said new sample is from the same spreading interval, processing the sample to do a prediction of noise in a future sample and using said prediction to reduce noise in said future sample;    D) if said sample is from a new spreading interval, initializing said FIFO in said predictor filter with samples corresponding to the first L unused codes of the new spreading interval;    E) calculating the inner product of the state vector defined by the contents of said FIFO with a coefficients vector defined by coefficients of said predictor filter to produce an estimation of the noise that will be in the next sample of said new spreading interval and subtracting said noise estimate from the value of said next sample prior to inputting said next sample into a slicer;    F) using a slicer error that results from processing by said slicer of said next sample to adapt said predictor filter coefficients using any adaptation method designed to adapt said predictor filter coefficients so as to reduce slicer error;    G) updating the state of said predictor filter by storing the most recently received interference sample and throwing away the oldest interference sample;    H) determining if said next sample just processed in said slicer is the last sample in said new spreading interval;    I) if said next sample just processed in said slicer is the last sample in said new spreading interval, returning to step D and continuing processing of newly received samples starting from step D;    J) if said next sample just processed in said slicer is not the last sample in said new spreading interval, returning to step E and continuing processing of newly received samples starting from step E.    
   
   
       2 . An apparatus comprising: 
 A) means for receiving a new sample in a predictor filter used in a code division multiple access circuit to predict the noise in the next received sample having an index beyond the index of samples in a first in, first out memory (FIFO) which comprise the state of said prediction filter, and for throwing out the oldest sample stored in said FIFO;    B) means for determining if said new sample represents signal received on the first code of a new spreading interval as compared to the spreading interval of the next previous sample received;    C) means for processing said new sample to do a prediction of noise in a future sample and using said prediction to reduce noise in said future sample if said new sample is from the same spreading interval;    D) means for initializing said FIFO in said predictor filter with samples corresponding to the first L unused codes of a new spreading interval if said new sample is from a new spreading interval;    E) means for calculating the inner product of the state vector defined by the contents of said FIFO with a coefficients vector defined by coefficients of said predictor filter to produce an estimation of the noise that will be in the next sample of said new spreading interval and subtracting said noise estimate from the value of said next sample prior to inputting said next sample into a slicer;    F) means for using a slicer error that results from processing by said slicer of said next sample to adapt said predictor filter coefficients using any adaptation method designed to adapt said predictor filter coefficients so as to reduce slicer error;    G) means for updating the state of said predictor filter by storing the most recently received interference sample and throwing away the oldest interference sample;    H) means for determining if said next sample just processed in said slicer is the last sample in said new spreading interval;    I) means for returning to step D and continuing processing of newly received samples starting from step D if said next sample just processed in said slicer is the last sample in said new spreading interval;    J) means for returning to step E and continuing processing of newly received samples starting from step E if said next sample just processed in said slicer is not the last sample in said new spreading interval.