Hybrid type channel estimation method and system for mobile environment

• US 20050286406A1
• Filed: 04/18/2005
• Published: 12/29/2005
• Est. Priority Date: 06/28/2004
• Status: Active Grant

• Current Assignee: Korea Electronics Technology Institute (Government of South Korea)
• Original Assignee: Korea Electronics Technology Institute (Government of South Korea)
• Inventors: Kim, Dong Sun, Seo, Jeong Wook, Wee, Jung Wook, Jeon, Won Gi, Lee, Youn Sung
• Granted Patent: US 7,649,830 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 1/208 involving signal re-encoding
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 25/0236 using estimation of the other symbols
• CPC Class Codes: H04L 25/025 using least-mean-square [LMS] method
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

Disclosed herein is a hybrid channel estimation method and system for an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system. The hybrid channel estimation method includes the steps of acquiring a first channel coefficient using decision-directed channel estimation; acquiring a second channel coefficient using pilot-symbol-aided channel estimation; and calculating the final channel coefficient of a received signal by multiplying the first and second coefficients by first and second multiplication coefficients, respectively, and adding the multiplication results. The step of acquiring the first channel coefficient using the decision-directed channel estimation includes the steps of acquiring an initial channel coefficient by processing a long training symbol using a Least Square (LS) method; generating data by equalizing, demodulating and modulating a fast Fourier transformed new symbol using a previously estimated channel coefficient; and acquiring a new channel coefficient by dividing the new symbol by the data.

Claims

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

acquiring a first channel coefficient using decision-directed channel estimation;

acquiring a second channel coefficient using pilot-symbol-aided channel estimation; and

calculating a final channel coefficient of a received signal by multiplying the first and second coefficients by first and second multiplication coefficients, respectively, and adding the multiplication results.

2. The hybrid channel estimation method as set forth in claim 1, wherein the step of acquiring the first channel coefficient using the decision-directed channel estimation comprises the steps of:

acquiring an initial channel coefficient by processing a long training symbol using a Least Square (LS) technique;

generating data by equalizing, demodulating and modulating a fast Fourier transformed new symbol using a previously estimated channel coefficient; and

acquiring a new channel coefficient by dividing the new symbol by the data.

3. The hybrid channel estimation method as set forth in claim 2, further comprising the step of reducing noise by processing the new channel coefficient using a Linear Minimum Mean Square Error (LMMSE) technique.

4. The hybrid channel estimation method as set forth in claim 2, wherein the new channel coefficient is calculated using the previously estimated channel coefficient.

5. The hybrid channel estimation method as set forth in claim 1, wherein the step of acquiring the second channel coefficient using the pilot-symbol-aided channel estimation comprises the steps of:

acquiring a channel coefficient at a location of a pilot symbol of the received signal using an LS technique; and

acquiring a channel coefficient by processing a following pilot symbol using the LS technique, and accumulating and averaging the channel coefficient and the previously estimated channel coefficient.

6. The hybrid channel estimation method as set forth in claim 4, further comprising the step of acquiring a channel coefficient by performing linear interpolation at a location of a data symbol of the received signal.

7. The hybrid channel estimation method as set forth in claim 1, wherein the first multiplication coefficient, by which the first channel coefficient acquired by the decision-directed channel estimation is multiplied, is an estimated level value of the received signal, and the second multiplication coefficient, by which the second channel coefficient acquired by the pilot-symbol-aided channel estimation is multiplied, is a constant value determined according to constellation of the signal.

8. A hybrid channel estimation system for an OFDM wireless communication, comprising:

a Fast Fourier Transform (FFT) processor for performing a fast Fourier transform on a received signal;

a decision-directed channel estimator;

a pilot-symbol-aided channel estimator;

two multipliers for multiplying each output of the channel estimators by predetermined coefficients, respectively; and

an adder for adding results of the two multipliers.

9. The hybrid channel estimation system as set forth in claim 8, wherein the decision-directed channel estimator performs the steps of:

acquiring an initial channel coefficient by processing a long training symbol using an LS method;

generating data by equalizing, demodulating and modulating a fast Fourier transformed new symbol using a previously channel estimated coefficient; and

acquiring a new channel coefficient by dividing the new symbol by the data.

10. The hybrid channel estimation system as set forth in claim 9, wherein the decision-directed channel estimator further performs the step of reducing noise by processing the new channel coefficient using an LMMSE method.

11. The hybrid channel estimation system as set forth in claim 8, wherein the pilot-symbol-aided estimator performs the steps of:

acquiring a channel coefficient at a location of a pilot symbol of the received signal using an LS method; and

acquiring a channel coefficient by processing a following pilot symbol using the LS method, and accumulating and averaging the channel coefficient and the previously estimated channel coefficient.

12. The hybrid channel estimation system as set forth in claim 11, wherein the pilot-symbol-aided channel estimator further performs the step of acquiring a channel coefficient by performing linear interpolation at a location of a data symbol of the received signal.

13. The hybrid channel estimation system as set forth in claim 8, further comprising a Viterbi decoder positioned to be adjacent to the decision-directed channel estimator.

14. The hybrid channel estimation system as set forth in claim 8, wherein the first multiplication coefficient, by which the first channel coefficient acquired by the decision-directed channel estimation is multiplied, is an estimated level value of the received signal, and the second multiplication coefficient, by which the second channel coefficient acquired by the pilot-symbol-aided channel estimation is multiplied, is a constant value determined according to constellation of the signal.