Apparatus and method for estimating a Doppler frequency and a moving velocity of a wireless terminal

• US 7,529,328 B2
• Filed: 06/27/2005
• Issued: 05/05/2009
• Est. Priority Date: 06/28/2004
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Ryu, Kil-Hyen
• Primary Examiner(s): Payne; David C
• Assistant Examiner(s): NGUYEN, LEON VIET Q
• Application Number:
  US11/167,833
• Publication Number:
  US 20050286666A1
• Time in Patent Office: 1,408 Days
• Field of Search: 375/150, 375/340, 375/350
• US Class Current: 375/350
• CPC Class Codes: H04B 7/002 Reducing depolarization effects
• CPC Class Codes: H04L 2027/0065 Frequency error detectors H04L2027/0067 takes precedence
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657

Abstract

An apparatus and method for estimating a Doppler frequency and a moving velocity of a wireless terminal are disclosed. The Doppler frequency estimator includes a filter bank, a non-coherent accumulator, and a maximum value detector. The filter bank filters demodulated signals with respect to frequency bands to provide a plurality of filtered signals. The non-coherent accumulator executes a non-coherent accumulation on each of the filtered signals to provide accumulated signals. The maximum value detector detects a signal having a largest value of the accumulated signals to provide a center frequency of a band corresponding to the detected signal as a Doppler frequency.

Claims

1. A Doppler frequency estimator, comprising:

a band-pass filter unit configured to perform a band-pass filtering operation on demodulated signals with respect to a modulo-2 search band to provide filtered signal pairs;

a non-coherent accumulator configured to execute a non-coherent accumulation on each of the filtered signal pairs to provide non-coherent accumulated signal pairs;

a comparator configured to compare the non-coherent accumulated signal pairs with each other to provide a larger one of the non-coherent accumulated signal pairs as a detection signal; and

a search control unit configured to iteratively generate control signals for a predetermined number of search periods to provide the control signals to the band-pass filter unit, and configured to determine that a detection signal detected at a final search period is a Doppler frequency, wherein the control signals narrow a search band by setting an initial modulo-2 search band during an initial search period and setting a modulo-2 search band of a next search period,

wherein the modulo-2 search band of the next search period is the initial modulo-2 search band divided in accordance with the detection signal such that a bandwidth of the modulo-2 search band of the next search period is less than a bandwidth of the initial modulo-2 search band.

2. The Doppler frequency estimator of claim 1, wherein the band-pass filter unit includes FIR-type filters.

3. The Doppler frequency estimator of claim 1, wherein the band-pass filter unit includes IIR-type filters.

4. The Doppler frequency estimator of claim 1, wherein the non-coherent accumulator comprises:

a square operation unit configured to execute a square operation on each of the filtered signal pairs to provide squared signal pairs; and

an accumulation unit configured to execute an accumulation operation on each of the squared signal pairs in data blocks inputted into the accumulation unit for a predetermined time to provide the accumulated signal pairs.

5. The Doppler frequency estimator of claim 1, wherein the modulated signals correspond to signals generated from one of demodulating incoming signals through an antenna and demodulating pilot signals.

6. The Doppler frequency estimator of claim 1, further comprising:

a velocity calculation unit for estimating a moving velocity of a wireless terminal.

7. The Doppler frequency estimator of claim 6, wherein the moving velocity of the wireless terminal is calculated using Vd=fd/fc×

C, where Vd denotes the moving velocity of the terminal, fd denotes the Doppler frequency, fc denotes a carrier frequency, and C denotes a velocity of an electromagnetic wave.

8. A method of calculating a Doppler frequency, comprising:

performing in a band-pass filter unit a band-pass filtering operation on demodulated signals with respect to a modulo-2 search band to provide filtered signal pairs;

executing a non-coherent accumulation on each of the filtered signal pairs to provide non-coherent accumulated signal pairs;

comparing the non-coherent accumulated signal pairs with each other to provide a larger one of the non-coherent accumulated signal pairs as a detection signal;

generating control signals for a predetermined number of search periods to provide the control signals to a the band-pass filter unit; and

determining that a detection signal detected at a final search period is a Doppler frequency, wherein the control signals narrow a search band by setting an initial modulo-2 search band during an initial search period and setting a modulo-2 search band of a next search period,

wherein the modulo-2 search band of the next search period is the initial modulo-2 search band divided in accordance with the detection signal such that a bandwidth of the modulo-2 search band of the next search period is less than a bandwidth of the initial modulo-2 search band.

9. The method of claim 8, wherein the accumulated signals are provided by:

executing a square operation on each of the filtered signals to provide squared signals; and

executing an accumulation operation on each of the squared signals in data blocks inputted for a predetermined time to provide the accumulated signals.

10. The method of claim 8, further comprising:

estimating a moving velocity of a wireless terminal, wherein the moving velocity of the wireless terminal is calculated using Vd=fd/fc×

C, where Vd denotes the moving velocity of the terminal, fd denotes the Doppler frequency, fc denotes a carrier frequency, and C denotes a velocity of an electromagnetic wave.