# US 6,735,264 B2 · Compensation for non-linear distortion in a modem receiver > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,735,264 B2 - Document ID: US6735264B2 - Status: Granted - Kind: B2 - Application number: 09/943,697 - Filed: 2001-08-31 - Published: 2003-05-01 - Granted: 2004-05-11 - Earliest claimed: 2001-08-31 - Assignees: Rainmaker Technologies, Inc. - Inventors: William J. Miller - Web page: https://patentgrep.com/patent/US6735264B2 ## CPC - H04L 27/0004: {using wavelets} - H04L 25/03343: {Arrangements at the transmitter end} - H04L 25/14: Channel dividing arrangements {, i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## 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. ## Claims ### Claim 1 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. ### Claim 2 (depends on 1) The method of claim 1, wherein the filtering step comprises calculating the coefficients from wavelet inner products at a first value of phase shift as between the one band and the adjacent band, and the defining step comprises defining a weighting function based upon a measured value of the phase shift as between the one band and the adjacent band. ### Claim 3 (depends on 1) The method of claim 1, wherein the filtering step comprises calculating the coefficients from wavelet inner products at a first value of time shift as between the one band and the adjacent band, and the defining step comprises defining a weighting function based upon a measured value of the time shift as between the one band and the adjacent band. ### Claim 4 (depends on 1) The method of claim 1, wherein defining a weighting function comprises defining sin(x) as the weighting function, where x is the differential variance in the selected metric. ### Claim 5 (depends on 1) The method of claim 1, wherein measuring the value of the differential variance in the selected metric is achieved by empirically measuring the value of the differential variance. ### Claim 6 (depends on 1) The method of claim 1, wherein measuring the value of the differential variance in the selected metric is achieved through the use of an adaptive combiner associated with the receiver. ### Claim 7 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. ### Claim 8 (depends on 7) The method of claim 7, wherein filtering the rotated signal comprises filtering the rotated signal through a filter bank having coefficients resulting from the inner product of respective wavelets at a predetermined value of phase shift as between adjacent band components and establishing an actual value comprises establishing an actual value of phase shift. ### Claim 9 (depends on 7) The method of claim 7, wherein filtering the rotated signal comprises filtering the rotated signal through a filter bank having coefficients resulting from the inner product of respective wavelets at a predetermined value of time delay as between adjacent band components and establishing an actual value comprises establishing an actual value of time delay. ### Claim 10 (depends on 7) The method of claim 7, wherein the step of weighting comprises applying a sine function of x to the result of the filtering step, where x is the value of variance in the first metric as between the adjacent band components. ### Claim 11 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. ### Claim 12 (depends on 11) The receiver of claim 11, wherein the metric is selected from the group consisting of time and phase.