Method and arrangement in wireless communications system

Patent metadata

Field	Value
Publication number	US-9001935-B2
Application number	US-201013880900-A
Country	US
Kind code	B2
Filing date	Oct 25, 2010
Priority date	Oct 25, 2010
Publication date	Apr 7, 2015
Grant date	Apr 7, 2015

Abstract

The present invention relates to a receiving node, and to a related method of adjusting a frequency domain channel estimate in a receiving node of a wireless communication system using Orthogonal Frequency Division Multiplexing. The method comprises estimating ( 210 ) a phase rotation of the frequency domain channel estimate, and compensating ( 220 ) for the estimated phase rotation in the frequency domain channel estimate. It also comprises transforming ( 230 ) the compensated frequency domain channel estimate into a time domain channel estimate, filtering ( 240 ) the time domain channel estimate to suppress noise, transforming ( 250 ) the filtered time domain channel estimate back into a noise suppressed frequency domain channel estimate, and adding ( 260 ) the estimated phase rotation in the noise suppressed frequency domain channel estimate to achieve an adjusted and improved frequency domain channel estimate.

First claim

The invention claimed is:

1. A method of adjusting a frequency domain channel estimate in a receiving node of a wireless communication system using Orthogonal Frequency Division Multiplexing, the method comprising:
estimating a phase rotation of the frequency domain channel estimate;
compensating for the estimated phase rotation in the frequency domain channel estimate;
transforming the compensated frequency domain channel estimate into a time domain channel estimate;
filtering the time domain channel estimate to suppress noise;
transforming the filtered time domain channel estimate into a noise suppressed frequency domain channel estimate; and
adding the estimated phase rotation to the noise suppressed frequency domain channel estimate to achieve an adjusted frequency domain channel estimate.

2. The method according to claim 1 , wherein the frequency domain channel estimate comprises a number of frequency domain channel taps, and wherein estimating the phase rotation comprises calculating a phase of each of said frequency domain channel taps, and estimating the phase rotation based on said calculated phases.

3. The method according to claim 2 , wherein said calculated phases are indexed in a sequence order of said frequency domain channel taps, and wherein estimating the phase rotation comprises calculating a phase difference for each pair of said calculated phases with a defined index interval, and estimating the phase rotation based on a mean value of said calculated phase differences and the defined index interval.

4. The method according to claim 2 , wherein estimating the phase rotation is based on a polynomial approximation using said calculated phases as input.

5. The method according to claim 1 , wherein the compensated frequency domain channel estimate is transformed into the time domain channel estimate based on an inverse discrete Fourier transform.

6. The method according to claim 1 , wherein filtering the time domain channel estimate comprises:
determining a peak power tap position of the time domain channel estimate;
setting a noise threshold for the time domain channel estimate;
suppressing taps with a power that falls below the noise threshold and that are positioned within a predetermined channel length from the determined peak power tap position; and
suppressing taps that are not positioned within the predetermined channel length from the determined peak power tap position, while leaving the tap at the peak power tap position unchanged.

7. The method according to claim 1 , wherein the filtered time domain channel estimate is transformed into the noise suppressed frequency domain channel estimate based on a discrete Fourier transform.

8. A receiving node for a wireless communication system using Orthogonal Frequency Division Multiplexing, the receiving node configured to adjust a frequency domain channel estimate and comprising a processing circuit configured to:
estimate a phase rotation of the frequency domain channel estimate;
compensate for the estimated phase rotation in the frequency domain channel estimate;
transform the compensated frequency domain channel estimate into a time domain channel estimate;
filter the time domain channel estimate to suppress noise;
transform the filtered time domain channel estimate into a noise suppressed frequency domain channel estimate; and
add the estimated phase rotation to the noise suppressed frequency domain channel estimate to achieve an adjusted frequency domain channel estimate.

9. The receiving node according to claim 8 , wherein the frequency domain channel estimate comprises a number of frequency domain channel taps, and wherein the processing circuit is configured to calculate phases of each of said frequency domain channel taps, and to estimate the phase rotation based on said calculated phases.

10. The receiving node according to claim 9 , wherein said calculated phases are indexed in a sequence order of said frequency domain channel taps, and the processing circuit is configured to calculate a phase difference for each pair of said calculated phases with a defined index interval, and to estimate the phase rotation based on a mean value of said calculated phase differences and the defined index interval.

11. The receiving node according to claim 9 , wherein the processing circuit is configured to estimate the phase rotation based on a polynomial approximation using said calculated phases as input.

12. The receiving node according to claim 8 , wherein the processing circuit is configured to transform the compensated frequency domain channel estimate into a time domain channel estimate based on an inverse discrete Fourier transform.

13. The receiving node according to claim 8 , wherein the processing circuit is configured to determine a peak power tap position of the time domain channel estimate, set a noise threshold for the time domain channel estimate, suppress taps with a power that falls below the noise threshold and that are positioned within a predetermined channel length from the determined peak power tap position, and suppress taps that are not positioned within the predetermined channel length from determined peak power tap position, while leaving the tap at the peak power tap position unchanged.

14. The receiving node according to claim 8 , wherein the processing circuit is configured to transform the filtered time domain channel estimate into the noise suppressed frequency domain channel estimate based on a discrete Fourier transform.

15. The receiving node according to claim 8 , wherein the receiving node is a radio base station or a user equipment in an E-UTRAN.

Assignees

• Guo Zhiheng
• Zhang Ruiqi
• Wang Hai
• Ericsson Telefon Ab L M

Inventors

• Guo Zhiheng
• Zhang Ruiqi
• Wang Hai

Classifications

• H04L25/0232

  by interpolation between sounding signals · CPC title

• H04L25/0204

  of multiple channels · CPC title

• H04L27/2647

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

• H04L25/022

  of frequency response · CPC title

• H04L25/0212 Primary

  of impulse response · CPC title