# US 10,237,109 B2 · Mitigating passive intermodulation interference in a wireless network > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,237,109 B2 - Document ID: US10237109B2 - Status: Granted - Kind: B2 - Application number: 15/485,083 - Filed: 2017-04-11 - Published: 2017-08-03 - Granted: 2019-03-19 - Earliest claimed: 2014-10-17 - Assignees: Aceaxis Limited - Applicants: AceAxis Limited - Inventors: Fiona Wilson; Simon Gale; David Damian Bevan - Web page: https://patentgrep.com/patent/US10237109B2 ## CPC - H04L 27/2688: {Resistance to perturbation, e.g. noise, interference or fading} - H04B 1/123: {using adaptive balancing or compensation means (adaptive filter circuits and algorithms H03H)} - H04L 25/0262: {Arrangements for detecting the data rate of an incoming signal} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## Abstract Interference (I1, I2) is mitigated in a waveform received at the input of a receiver in a wireless network, the interference comprising passive intermodulation PIM products of at least a first signal (C1). A first stream of time samples (5) is generated of a simulated first PFM product of at least the first signal (C1), and a second stream of time samples (6) is generated of the simulated first PIM product. The second stream has a delay with respect to the first stream. A replica (8) is generated of the interference by processing (7) at least the first stream and the second stream, the processing comprising reducing a degree of correlation between the first stream and the second stream, and the replica of the interference is combined with a stream of time samples of the received waveform (40) to reduce the interference in the received waveform. ## Claims ### Claim 1 A method of mitigating interference in a waveform received at the input of a receiver in a wireless network, the interference comprising passive intermodulation (PIM) products of at least a first signal, the method comprising: generating a first stream of time samples of a simulated first PIM product of at least the first signal, and generating a second stream of time samples of the simulated first PIM product, wherein the second stream has a delay with respect to the first stream; generating a replica of the interference by processing at least the first stream and the second stream, wherein said processing comprises determining a first weighting factor by correlating the first stream with a stream of time samples of the received waveform, and determining a second weighting factor by correlating the second stream with the stream of time samples of the received waveform, and weighting the first stream by a first weighting factor and weighting the second stream by a second weighting factor; and combining the replica of the interference with the stream of time samples of the received waveform, whereby to reduce the interference in the received waveform. ### Claim 2 (depends on 1) The method according to claim 1, wherein said processing further comprises reducing a degree of correlation between the first stream and the second stream comprising: determining a correlation between the first stream and the second stream; determining a third weighting factor in dependence on the correlation; weighting a sample of the first stream using the third weighting factor to produce a weighted sample of the first stream; and combining the weighted sample of the first stream with the second stream. ### Claim 3 (depends on 2) The method according to claim 2, comprising performing the step of reducing the degree of correlation between the first stream and the second stream in dependence on an analysis of the correlation between the first stream of time samples and the stream of time samples of the received waveform. ### Claim 4 (depends on 3) The method according to claim 3, wherein the analysis of the correlation between the first stream of time samples and the stream of time samples of the received waveform comprises determining a width of a correlation peak. ### Claim 5 (depends on 1) The method according to claim 1, wherein said generation and processing of the first stream and the second stream is at baseband. ### Claim 6 (depends on 1) The method according to claim 1, comprising: varying a value of the delay of the second stream with respect to the first stream to determine a delay value that increases a degree of cancellation of interference in the received waveform. ### Claim 7 (depends on 6) The method according to claim 6, comprising: determining the delay value on the basis of trial values of delay applied to stored data representing the first stream of time samples, the second stream of time samples, and the stream of time samples of the received waveform; and using the determined delay to generate the replica of the interference for use in cancelling the interference in the received waveform in real time. ### Claim 8 (depends on 1) The method according to claim 1, comprising forming the replica as a matrix, a first axis the matrix representing time and a second axis of the matrix representing a respective stream of time samples of a plurality of streams of time samples. ### Claim 9 (depends on 1) The method according to claim 1, wherein the simulated first PIM product relates to a first exponent value. ### Claim 10 (depends on 1) The method according to claim 1, comprising generating a plurality of streams of time samples comprising a first plurality of streams of time samples for a plurality of values of PIM product exponent and a second plurality of streams of time samples for the plurality of values of PIM product exponent, the second plurality of streams of time samples having a value of delay with respect to the first plurality of streams of time samples that is the same for each value of PIM product exponent. ### Claim 11 (depends on 10) The method according to claim 10, wherein the value of delay of the second plurality of streams of time samples with respect to the first plurality of streams of time samples is determined by varying a value of the delay to determine a delay value that increases a degree of cancellation of interference in the received waveform for the first value of PIM product exponent. ### Claim 12 Apparatus for mitigating interference in a waveform received at the input of a receiver in a wireless network, the interference comprising passive intermodulation (PIM) products of at least a first signal, the apparatus comprising a digital signal processor configured to: generate a first stream of time samples of a simulated first PIM product of at least the first signal, and generating a second stream of time samples of the simulated first PIM product, wherein the second stream has a delay with respect to the first stream; generate a replica of the interference by processing at least the first stream and the second stream, wherein said processing comprises determining a first weighting factor by correlating the first stream with a stream of time samples of the received waveform, and determining a second weighting factor by correlating the second stream with the stream of time samples of the received waveform, and weighting the first stream by a first weighting factor and weighting the second stream by a second weighting factor; and combine the replica of the interference with the stream of time samples of the received waveform, whereby to reduce the interference in the received waveform. ### Claim 13 (depends on 12) The apparatus according to claim 12, wherein the digital signal processor is configured to generate and process the first stream and the second stream at baseband. ### Claim 14 (depends on 12) The apparatus according to claim 12, wherein the digital signal processor is configured to vary a value of the delay of the second stream with respect to the first stream to determine a delay value that increases a degree of cancellation of interference in the received waveform. ### Claim 15 (depends on 14) The apparatus according to claim 14, wherein the digital signal processor is configured to: determine the delay value on the basis of trial values of delay applied to stored data representing the first stream of time samples, the second stream of time samples, and the stream of time samples of the received waveform; and use the determined delay to generate the replica of the interference for use in cancelling the interference in the received waveform in real time. ### Claim 16 (depends on 12) The apparatus according to claim 12, wherein the digital signal processor is configured to form the replica as a matrix, a first axis the matrix representing time and a second axis of the matrix representing a respective stream of time samples of a plurality of streams of time samples.