Systems and methods for adaptive averaging in frequency domain equalization systems

Patent metadata

Field	Value
Publication number	US-10505573-B2
Application number	US-201816216818-A
Country	US
Kind code	B2
Filing date	Dec 11, 2018
Priority date	Jul 23, 2014
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

Abstract

An example system comprises a first antenna and a modem. The first antenna is configured to receive a signal from a transmitting radio frequency unit. The signal includes data and a known sequence. The modem is configured to retrieve the known sequence from the signal, transform the known sequence and the data into a frequency domain, calculate averages of groups of neighboring frequency points in the frequency domain to reduce the effect of nonlinear noise in the signal, the neighboring frequency points corresponding to the preamble in the frequency domain, compare the calculated averages to an expected frequency response in the frequency domain, determine a correction filter to apply to the data based on the comparison, apply the correction filter on the data in the frequency domain to create corrected data, transform the corrected data from the frequency domain to the time domain, and provide the data.

First claim

The invention claimed is:

1. A system comprising:
an antenna configured to receive a signal from a transmitting radio frequency unit, the signal including a preamble containing bits for a known sequence of a predetermined length; and
a modem configured to:
retrieve the preamble from the signal;
transform the preamble from a time domain into a frequency domain, the transforming the preamble into the frequency domain causing generation of preamble-based frequency points in the frequency domain;
group neighboring frequency points of the preamble-based frequency points in the frequency domain to generate one or more groups of neighboring preamble-based frequency points, each group of neighboring preamble-based frequency points including a particular number of neighboring preamble-based frequency points, the particular number being based on an amount of error in the signal;
generate a representative point in the frequency domain for each group of neighboring preamble-based frequency points;
compare each representative point to an expected frequency response in the frequency domain, the expected frequency response being based on the known sequence of the predetermined length in the frequency domain, the comparison to be used to determine an effect of nonlinear noise in the signal;
determine a correction filter based on the comparison to apply to data received by the antenna, the correction filter configured to reduce the effect of the nonlinear noise on the data;
transform the data received by the antenna from the time domain to the frequency domain;
apply the correction filter to the data in the frequency domain to create corrected data in the frequency domain;
transform the corrected data from the frequency domain back to the time domain; and
provide the corrected data for processing.

2. The system of claim 1 , further comprising a second correction filter configured to adjust the signal to correct for known hardware imperfections of a receiver.

3. The system of claim 1 , wherein the modem is further configured to identify and retrieve a cyclic prefix from the signal.

4. The system of claim 1 , wherein at least some of the nonlinear noise is generated by components of the transmitting radio frequency unit.

5. The system of claim 1 , wherein at least some of the nonlinear noise is generated by components of a receiving radio frequency unit.

6. The system of claim 1 , wherein the correction filter is configured to apply an inverse function based on a difference between each representative point and the expected frequency response in the frequency domain to the data.

7. The system of claim 1 , wherein the modem is further configured to select the correction filter from a plurality of preexisting correction filters based on the comparison of each representative point to the expected frequency response.

8. The system of claim 1 , wherein the expected frequency response is generated by transforming a reference signal to the frequency domain, the reference signal comprising a same sequence of symbols as the known sequence, the reference signal having not been transmitted from the transmitting radio frequency unit to the antenna.

9. The system of claim 1 , wherein the modem is a part of a microwave receiving radio frequency unit coupled to the antenna.

10. The system of claim 9 , wherein the transmitting radio frequency unit transmits the signal to the microwave receiving radio frequency unit via line of sight propagation.

11. A method performed by a communication device, the method comprising:
receiving a signal from a transmitting radio frequency unit, the signal including a preamble containing bits for a known sequence of a predetermined length;
transforming the preamble from a time domain into a frequency domain, the transforming the preamble into the frequency domain causing generation of preamble-based frequency points in the frequency domain;
grouping neighboring frequency points of the preamble-based frequency points in the frequency domain to generate one or more groups of neighboring preamble-based frequency points, each group of neighboring preamble-based frequency points including a particular number of neighboring preamble-based frequency points, the particular number being based on an amount of error in the signal;
generating a representative point in the frequency domain for each group of neighboring preamble-based frequency points;
comparing each representative point to an expected frequency response in the frequency domain, the expected frequency response being based on the known sequence of the predetermined length in the frequency domain, the comparison to be used to determine an effect of nonlinear noise in the signal;
determining a correction filter based on the comparison to apply to data received by an antenna, the correction filter configured to reduce the effect of the nonlinear noise on the data;
transforming the data received by the antenna from the time domain to the frequency domain;
applying the correction filter to the data in the frequency domain to create corrected data in the frequency domain;
transforming the corrected data from the frequency domain back to the time domain; and
providing the corrected data for processing.

12. The method of claim 11 , further comprising filtering the signal with a second correction filter configured to adjust the signal to correct for known hardware imperfections of a receiver.

13. The method of claim 11 , further comprising identifying and retrieving a cyclic prefix from the signal.

14. The method of claim 11 , wherein at least some of the nonlinear noise is generated by components of the transmitting radio frequency unit.

15. The method of claim 11 , wherein at least some of the nonlinear noise is generated by components of a receiving radio frequency unit.

16. The method of claim 11 , wherein the correction filter is configured to apply an inverse function based on a difference between each representative point and the expected frequency response in the frequency domain to the data.

17. The method of claim 11 , wherein the correction filter is selected from a plurality of preexisting correction filters based on the comparison of each representative point to the expected frequency response.

18. The method of claim 11 , wherein the expected frequency response is generated by transforming a reference signal to the frequency domain, the reference signal comprising a same sequence of symbols as the known sequence, the reference signal having not been transmitted from the transmitting radio frequency unit to the antenna.

19. The method of claim 11 , wherein a microwave receiving radio frequency unit is configured to receive the signal from the transmitting radio frequency unit.

20. The method of claim 19 , wherein the transmitting radio frequency unit transmits the signal to the microwave receiving radio frequency unit via line of sight propagation.

21. A non-transitory computer readable medium comprising instructions executable by a processor to perform a method, the method comprising:
receiving a signal from a transmitting radio frequency unit, the signal including a preamble containing bits for a known sequence of a predetermined length;
transforming the preamble from a time domain into a frequency domain, the transforming the preamble into the frequency domain causing generation of preamble-based frequency points in the frequency domain;
grouping neighboring frequency points of the preamble-based frequency points in t

Assignees

• Aviat Us Inc

Inventors

• Plevel Sreco

Classifications

• H04J4/005

  Transmultiplexing · CPC title

• H04L27/366

  Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator · CPC title

• H04L27/2647

  Arrangements specific to the receiver only (equalisation H04L27/01) · CPC title

• H04L25/0228

  with direct estimation from sounding signals · CPC title

• H04L25/03159

  operating in the frequency domain (H04L25/03165, H04L25/03178 take precedence) · CPC title