Interference cancellation using non-linear filtering

Patent metadata

Field	Value
Publication number	US-10069712-B2
Application number	US-201615266944-A
Country	US
Kind code	B2
Filing date	Sep 15, 2016
Priority date	Sep 17, 2015
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

To process received wireless signals received in a receiver, a noise and interference estimate is generated by subtracting the component from the received OFDM signal, a normalized noise signal by whitening the noise and interference estimate is produced, interference estimation information is computed from the normalized noise signal, a non-linear frequency domain filtering operation is performed on an output of the interference estimation to generate a frequency domain filtered signal, and a non-linear time domain filtering operation is performed on the frequency domain filtered signal to generate an estimate of an unwanted component of the received OFDM signal. The non-linear filtering may be performed using a median filter or an adaptive median filter or an adaptive hybrid median filter.

First claim

What is claimed is what is described and illustrated, including:

1. A method of wireless signal processing performed at a receiver in a wireless cellular communication network, comprising:
receiving, by a wireless receiver, an orthogonal frequency division multiplexing (OFDM) signal;
estimating, a component of the received OFDM signal corresponding to a serving cell transmission;
generating a noise and interference estimate by subtracting the component from the received OFDM signal;
producing a normalized noise signal by whitening the noise and interference estimate;
computing interference estimation information from the normalized noise signal;
performing a non-linear frequency domain filtering on an output of the interference estimation to generate a frequency domain filtered signal; and
performing non-linear time domain filtering on the frequency domain filtered signal to generate an estimate of an unwanted component of the received OFDM signal.

2. The method of claim 1 , wherein the performing the non-linear frequency domain filtering comprises:
filtering the output of the interference estimation using a non-linear filter.

3. The method of claim 1 , wherein the OFDM signal is characterized by a transmission time interval, and wherein the non-linear time domain filtering is performed in the frequency domain filtered signal and a delayed version of the frequency domain filtered signal delayed by an integer number of transmission time interval values.

4. The method of claim 3 , wherein the non-linear lime domain filtering comprises an adaptive median filter.

5. The method of claim 4 , further comprising:
measuring variations in the received signal; and
adapting a characteristic of the adaptive median filter based on the measured variations in the received signal.

6. The method of claim 5 , wherein the characteristic of the adaptive median filter comprises a window of operation of the adaptive median filter.

7. The method of claim 5 , wherein the measuring variations in the received signal includes:
updating, for each sample of the received signal, a median value of the received signal; and
comparing a difference between the sample and the median value with a predetermined threshold.

8. The method of claim 1 , wherein the non-linear frequency domain filtering is performed using a median filter, the method further comprising:
estimating a statistical parameter of the received signal; and
changing a length of the median filter based on the statistical parameter.

9. The method of claim 8 , wherein the estimating the statistical parameter comprises estimating an outlier signal value that varies from an expected signal value by more than a threshold.

10. A wireless receiver apparatus, comprising:
a receiver circuit that receives an orthogonal frequency division multiplexing (OFDM) signal; and
a processor that processes the received OFDM signals by:
estimating, a component of the received OFDM signal corresponding to a serving cell transmission;
generating a noise and interference estimate by subtracting the component from the received OFDM signal;
producing a normalized noise signal by whitening the noise and interference estimate;
detecting interference estimation information from the normalized noise signal;
performing a non-linear frequency domain filtering on an output of the interference estimation to generate a frequency domain filtered signal; and
perforating non-linear time domain filtering on the frequency domain filtered signal to generate an estimate of an unwanted component of the received OFDM signal.

11. The apparatus of claim 10 , wherein the processor performs the non-linear frequency domain filtering by:
filtering the output of the interference estimation using a non-linear filter.

12. The apparatus of claim 10 wherein the OFDM signal is characterized by a transmission time interval, and wherein the processor performs the non-linear time domain filtering on the frequency domain filtered signal and a delayed version of the frequency domain filtered signal delayed by an integer number of transmission time interval values.

13. The apparatus of claim 12 , wherein the non-linear time domain filtering comprises an adaptive median filter.

14. The apparatus of claim 13 , wherein the processor further:
measures variations in the received signal; and
adapts a characteristic of the adaptive median filter based on the measured variations in the received signal.

15. The apparatus of claim 14 , wherein the characteristic of the adaptive median filter comprises a window of operation of the adaptive median filter.

16. The apparatus of claim 14 , wherein the processor measures variations in die received signal by:
updating, for each sample of the received signal, a median value of the received signal; and
comparing a difference between the sample and the median value with a predetermined threshold.

17. The apparatus of claim 10 , wherein the processor performs the non-linear frequency domain filtering by:
implementing a median filter;
estimating a statistical parameter of the received signal; and
changing a length of the median filter based on the statistical parameter.

18. A non-transitory computer-readable program medium storing computer-executable instructions, which when executed by a processor, causing the processor to implement a method of wireless signal processing that comprises:
receiving, by a wireless receiver, an orthogonal frequency division multiplexing (OFDM) signal;
estimating, a component of the received OFDM signal corresponding to a serving cell transmission;
generating a noise and interference estimate by subtracting the component from the received OFDM signal;
producing a normalized noise signal by whitening the noise and interference estimate;
computing interference estimation information from the normalized noise signal;
performing a non-linear frequency domain filtering on an output of the interference estimation to generate a frequency domain filtered signal; and
performing non-linear time domain filtering on the frequency domain filtered signal to generate an estimate of an unwanted component of the received OFDM signal.

19. The non-transitory computer-readable program medium of claim 18 , wherein the performing the non-linear frequency domain filtering comprises:
filtering the output of the interference estimation using a non-linear filter.

20. The non-transitory computer-readable program medium of claim 18 wherein the OFDM signal is characterized by a transmission time interval, and wherein the non-linear time domain filtering is performed in the frequency domain filtered signal and a delayed version of the frequency domain filtered signal delayed by an integer number of transmission time interval values.

21. The non-transitory computer-readable program medium of claim 20 , wherein the non-linear time domain filtering comprises an adaptive median filter.

22. The non-transitory computer-readable program medium of claim 18 , wherein the method further comprises:
measuring variations in the received signal; and
adapting a characteristic of the adaptive median filter based on the measured variations in the received signal.

23. The non-transitory computer-readable program medium of claim 22 , wherein the characteristic of the adaptive median filter comprises a window of operation of the adaptive median filter.

24. The non-transitory computer-readable pr

Assignees

• Zte Corp
• Zte Canada Inc

Inventors

• Qian Xing
• Chen Yu

Classifications

• H04L5/00

  Arrangements affording multiple use of the transmission path · CPC title

• H04L43/16 Primary

  Threshold monitoring · CPC title

• H04L27/2691 Primary

  involving interference determination or cancellation · CPC title

• H04L27/2601

  Multicarrier modulation systems · CPC title

• H04L27/2655 Primary

  Synchronisation arrangements · CPC title