Compensation for non-linear distortion in a modem receiver
AssigneeRainmaker Technologies, Inc.
InventorWilliam J. Miller
Life of this patent
Estimating the term…
Abstract
A method and modem for communicating serial input data over a transmission link are disclosed. Serial input data is partitioned into parallel data elements prior to rotation by an invertible linear mapping. Computationally efficient multi-rate wavelet filter banks are employed in a receiver for analyzing a received signal. Self-interference components are calculated in the receiver per sub-band and tap-weights for the filter banks are derived as a function over the range of self-interference values. A weighted sum is formed and subtracted from the delayed, received signal to eliminate the interference, and is removed from the recovered signal.
Claims12
A method of compensating for self-interference in a signal received at a receiver, the receiver comprised of a multi-rate filter bank having wavelet functions as filter coefficients, the signal comprised of plural, wavelet-encoded sub-bands overlapping in time and in frequency, the method comprising:
- receiving the signal at the receiver;
- rotating the received signal by passing the received signal through the multi-rate filter bank to produce a rotated signal set comprised of plural bands;
- filtering the rotated signal set through a second filter bank having respective band coefficients each calculated from wavelet inner products at a first value of differential variance in a selected metric as between one band and an adjacent band, the second filter bank providing a measure of self-interference for each band;
- defining a weighting function based upon a measured value of the differential variance in the selected metric as between the one band and the adjacent band;
- applying the weighting function to the measure of self-interference for each band to produce a correction factor for each band;
- and
- subtracting the correction factor for each band from the received signal.
In a receiver having a multi-rate filter bank for analyzing a received signal comprised of plural wavelets overlapping in time and frequency, each modulated by a data symbol, a method of compensating for non-linear distortion introduced into the received signal, comprising:
- analyzing the received signal using the multi-rate filter bank to produce a rotated signal set comprised of plural band components;
- filtering the rotated signal through a filter bank having coefficients resulting from the inner product of respective wavelets at a predetermined value of variance in a first metric as between adjacent band components;
- establishing an actual value of variance in the first metric as between the adjacent band components;
- weighting the result of the filtering step based upon a pre-defined function of the actual value of variance in the first metric in order to define a distortion offset;
- and
- subtracting the distortion offset from the received signal.
A receiver for a wavelet transmission system comprising:
- a multi-rate filter bank for analyzing a received signal comprised of wavelet-encoded sub-bands;
- a filtration circuit for determining wavelet inner products for adjacent sub-bands as a function of a pre-defined value of distortion in a first metric;
- a distortion detection circuit for empirically detecting a degree of distortion in the metric between the adjacent sub-bands;
- a weighting circuit for applying a pre-determined weighting function to outputs of the distortion detection circuit for generating a distortion offset, wherein the pre-determined weighting function is a function of the detected distortion in the metric between the adjacent sub-bands;
- and
- a subtraction circuit for subtracting the distortion offset from the received signal.
Dependencies are inferred from the claim text.