CHANNEL ESTIMATION METHOD OF AN ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SYSTEM AND RECEIVING APPARATUS

• US 20110228868A1
• Filed: 06/02/2011
• Published: 09/22/2011
• Est. Priority Date: 12/03/2008
• Status: Active Grant

• Current Assignee: Honor Device Company Limited
• Original Assignee: Huawei Device Company Limited (Huawei Investment & Holding Co., Ltd.)
• Inventors: Wu, Gengshi, Jiao, Shurong, Hua, Meng, Tang, Bing
• Granted Patent: US 8,335,270 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0232 by interpolation between sounding signals

Abstract

A channel estimation method of an Orthogonal Frequency Division Multiplexing (OFDM) system and a corresponding receiving apparatus are provided. The technical solutions use the receiving apparatus to firstly perform channel estimation in time dimension on received signals, obtain channel information of pilot points from an effective sub-carrier frequency band on a frequency domain of each OFDM symbol, obtain information of the pilot points on frequency bands outside the effective sub-carrier frequency band by adding the information of the pilot points, and then perform Inverse Fast Fourier Transform (IFFT), windowing, zero-padding, and Fast Fourier Transform (FFT) to obtain a channel frequency response, so as to obtain a channel estimation result. The technical solutions can achieve goals of restraining an edge effect and improving accuracy of the channel estimation.

Claims

1. A channel estimation method of an Orthogonal Frequency Division Multiplexing (OFDM) system, the method comprising:

receiving signals sent by a sending apparatus;

performing channel estimation in time dimension on the signals;

obtaining pilot signals from an effective sub-carrier frequency band on bandwidth of an OFDM symbol obtained after the channel estimation;

adding channel information of pilot points on frequency bands outside the effective sub-carrier frequency band on the bandwidth of the OFDM symbol according to the obtained pilot signals;

performing Inverse Fast Fourier Transform (IFFT) on the obtained pilot signals and the added channel information of the pilot points;

windowing a time-domain response obtained after the IFFT according to preset windowing information;

zero-padding the windowed time-domain response according to a number of sub-carriers of the OFDM symbol;

performing Fast Fourier Transform (FFT) on the zero-padded time-domain response; and

obtaining a channel frequency response with a length being a number of effective sub-carriers in the effective sub-carrier frequency band from the channel frequency response obtained after the FFT.

2. The method according to claim 1, wherein the adding the channel information of the pilot points on the frequency bands outside the effective sub-carrier frequency band on the bandwidth of the OFDM symbol according to the obtained pilot signals comprises:

mirroring M pilot points in the effective sub-carrier frequency band by using two pilot points of outermost ends of the effective sub-carrier frequency band as a “

mirror”

.

3. The method according to claim 2, wherein channel information of the mirrored pilot points and the channel information of the pilot points in the effective sub-carrier frequency band have a linear relationship.

4. The method according to claim 1, wherein the windowing the time-domain response obtained after the IFFT according to the preset windowing information comprises:

adding windows with lengths being L+K and K to the time-domain response obtained after the IFFT according to information of preset windowing lengths being respectively L and K,

wherein the added window with the length being K comprises a rectangular window with the length being K or a triangular window with the length being K.

5. The method according to claim 4, wherein the zero-padding the windowed time-domain response according to the number of the sub-carriers of the OFDM symbol comprises:

zero-padding between two groups of time-domain signals with lengths being L+K and K obtained after the windowing according to the number of the sub-carriers of the OFDM symbol.

6. A receiving apparatus, comprising:

a receiving unit, configured to receive signals sent by a sending apparatus;

a time-domain estimation unit, configured to perform channel estimation in time dimension on the signals;

a pilot extracting unit, configured to obtain pilot signals from an effective sub-carrier frequency band on bandwidth of an Orthogonal Frequency Division Multiplexing (OFDM) symbol obtained after the channel estimation;

a pilot adding unit, configured to add channel information of pilot points on frequency bands outside the effective sub-carrier frequency band on the bandwidth of the OFDM symbol according to the obtained pilot signals;

an Inverse Fast Fourier Transform (IFFT) unit, configured to perform IFFT on the obtained pilot signals and the added channel information of the pilot points;

a time-domain windowing unit, configured to window a time-domain response obtained after the IFFT according to preset windowing information;

a zero-padding unit, configured to zero-pad the windowed time-domain response according to a number of sub-carriers of the OFDM symbol;

a Fast Fourier Transform (FFT) unit, configured to perform FFT on the zero-padded time-domain response; and

an obtaining unit, configured to obtain a channel frequency response with a length being a number of effective sub-carriers in the effective sub-carrier frequency band from the channel frequency response obtained after the FFT.

7. The receiving apparatus according to claim 6, wherein the pilot adding unit comprises:

a pilot adding mirroring unit, configured to mirror M pilot points in the effective sub-carrier frequency band by using two pilot pilots of outermost ends of the effective sub-carrier frequency band as a “

mirror”

, wherein channel information of the mirrored pilot points and the channel information of the pilot points in the effective sub-carrier frequency band have a linear relationship.

8. The receiving apparatus according to claim 6, wherein the time-domain windowing unit comprises:

a first windowing unit, configured to add windows with lengths being L+K and K to the time-domain response obtained after the IFFT according to information of preset windowing lengths being respectively L and K, wherein the added window with the length being K comprises a rectangular window with the length being K or a triangular window with the length being K.

9. The receiving apparatus according to claim 8, wherein the zero-padding unit comprises:

a first zero-padding unit, configured to zero-pad between two groups of time-domain signals with lengths being L+K and L obtained after the windowing according to the number of the sub-carriers of the OFDM symbol.