# US 8,787,473 B2 · Method and apparatus for noise estimation in orthogonal frequency division multiplexing (OFDM) system

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- Number: US 8,787,473 B2
- Document ID: US8787473B2
- Status: Granted
- Kind: B2
- Application number: 13/505,309
- Filed: 2010-05-20
- Published: 2012-08-30
- Granted: 2014-07-22
- Earliest claimed: 2009-11-10
- Assignees: Zte Corporation
- Applicants: Junling Zhang
- Inventors: Junling Zhang
- Web page: https://patentgrep.com/patent/US8787473B2

## CPC

- H04L 25/022: {of frequency response}
- H04L 25/0224: {using sounding signals}
- H04L 27/2647: {Arrangements specific to the receiver only (equalisation H04L27/01)}
- H04L 25/03299: {with noise-whitening circuitry}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

The present invention discloses a method and apparatus for performing noise estimation in an OFDM system. The method comprises: a channel estimation coefficient generation module generating a channel estimation coefficient wk, where k is an integer between - N tap 2 ⁢ ⁢ and ⁢ ⁢ N tap 2 , and Ntap is a positive integer greater than 1, 0<wk<1; a channel estimation module calculating a channel estimation based on a received signal on a subcarrier of an OFDM symbol and the channel estimation coefficient wk; a noise estimation calculation module calculating a noise estimation based on the received signal on the subcarrier of the orthogonal frequency division multiplexing symbol and the channel estimation; a correction factor calculation module calculating a correction factor β based on the channel estimation coefficient wk generated by the channel estimation coefficient generation module; and a correction module correcting the noise estimation output by the noise estimation calculation module based on the correction factor β.

## Claims

### Claim 1

An apparatus for performing noise estimation in an orthogonal frequency division multiplexing system comprising: a channel estimation coefficient generation module, a channel estimation module and a noise estimation calculation module connected to each other in sequence, a correction factor calculation module connected to an output of the channel estimation coefficient generation module, and a correction module connected to both the correction factor calculation module and noise estimation calculation module; wherein
the channel estimation coefficient generation module is configured to generate a channel estimation coefficient wk, where k is an integer between
-
N
tap
2
⁢
⁢
and
⁢
⁢
N
tap
2
,
and Ntap is a positive integer greater than 1, 0<|wk|<1;
the channel estimation module is configured to calculate a channel estimation based on a received signal on a subcarrier of an orthogonal frequency division multiplexing symbol and the channel estimation coefficient wk;
the noise estimation calculation module is configured to calculate a noise estimation based on the received signal on the subcarrier of the orthogonal frequency division multiplexing symbol and the channel estimation;
the correction factor calculation module is configured to calculate a correction factor β based on the channel estimation coefficient wk generated by the channel estimation coefficient generation module, wherein the correction factor β is obtained based on the following formula: β=1+|w0|2−(w0*+w0)+α, where w0* is a conjugate value of w0, and α is a residual noise correction factor, 0<α<1; and
the correction module is configured to correct the noise estimation output by the noise estimation calculation module based on the correction factor β.

### Claim 2 (depends on 1)

The apparatus according to claim 1, wherein
the correction module is configured to use a ratio of the noise estimation to the correction factor as the corrected noise estimation.

### Claim 3 (depends on 2)

The apparatus according to claim 2, wherein
the noise estimation calculation module comprises a cache unit configured to calculate the noise estimation after caching the received signal on the subcarrier of the orthogonal frequency division multiplexing symbol.

### Claim 4

A method for performing noise estimation in an orthogonal frequency division multiplexing system comprising:
generating, by a channel estimation coefficient generation module, a channel estimation coefficient wk, where k is an integer between
-
N
tap
2
⁢
⁢
and
⁢
⁢
N
tap
2
,
and Ntap is a positive integer greater than 1,0<|wk|<1;
calculating, by a channel estimation module, a channel estimation based on a received signal on a subcarrier of an orthogonal frequency division multiplexing symbol and the channel estimation coefficient wk;
calculating, by a noise estimation calculation module, a noise estimation based on the received signal on the subcarrier of the orthogonal frequency division multiplexing symbol and the channel estimation;
calculating, by a correction factor calculation module, a correction factor β based on the channel estimation coefficient wk generated by the channel estimation coefficient generation module, wherein the correction factor β is obtained based on the following formula: β=1+|w0|2−(w0*+w0)+α, where w0* is a conjugate value of w0, and α is a residual noise correction factor, 0<α<1; and
correcting, by a correction module, the noise estimation output by the noise estimation calculation module based on the correction factor β.

### Claim 5 (depends on 4)

The method according to claim 4, wherein
in the step of correcting the noise estimation, the correction module uses a ratio of the noise estimation to the correction factor as the corrected noise estimation.

### Claim 6 (depends on 4)

The method according to claim 4, wherein
in the step of calculating the noise estimation, the noise estimation calculation module calculating the noise estimation after caching the received signal on the subcarrier of the OFDM symbol.