Velocity estimation apparatus in mobile communication environments

• US 20050282499A1
• Filed: 06/02/2005
• Published: 12/22/2005
• Est. Priority Date: 06/04/2004
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd., Yonsei University
• Original Assignee: Samsung Electronics Co. Ltd., Yonsei University
• Inventors: Kim, Eung-Sun, Lee, Jong-Hyeuk, Hong, Dae-Sik, Lee, Ye-Hoon, Cho, Myeon-Gyun, Park, Goo-Hyun
• Granted Patent: US 7,515,902 B2
• Time in Patent Office: Days
• US Class Current: 455/67.11
• CPC Class Codes: G01S 11/10 using Doppler effect
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination

Abstract

Disclosed is a method for estimating the velocity of a mobile station in Rician fading environments in which a direct wave exists. Cellular mobile communication environments include two environments, Rician fading environments in which a direct wave exists and Rayleigh fading environments in which a direct wave does not exist. Generally, many methods for estimating the velocity of a mobile station have been known in Rayleigh fading environments. However, in Rician fading environments in which a direct wave exists, many errors occurs in estimating the velocity of a mobile station due to difficulty in estimation of a Rician coefficient K and an incident angle θ₀. According to the invention, a method is provided wherein error is mostly eliminated in estimating the velocity of a mobile station by obtaining a maximum Doppler frequency of the mobile station, even without directly obtaining a Rician coefficient K and an incident angle θ₀.

Claims

1. A velocity estimation apparatus in a communication system including a transmitter for transmitting signals through radio channels and a receiver for receiving the signals and restoring data, the apparatus comprising:

a pilot separation unit for separating a pilot signal from the received signal;

a maximum Doppler frequency estimator for estimating a maximum Doppler frequency by means of the pilot signal output from the pilot separation unit; and

a velocity information generator for converting an estimated value of the maximum Doppler frequency estimated by the maximum Doppler frequency estimator into velocity information.

2. The velocity estimation apparatus as claimed in claim 1, wherein the maximum Doppler frequency estimator comprises:

an auto-covariance calculation unit for outputting auto-covariance values by means of the pilot signal; and

a maximum Doppler frequency calculation unit for obtaining the maximum Doppler frequency by means of the auto-covariance values output from the auto-covariance calculation unit.

3. The velocity estimation apparatus as claimed in claim 2, wherein the auto-covariance calculation unit comprises:

a first auto-covariance module for performing an auto-covariance operation having a predetermined time difference for the pilot signal, thereby outputting a first auto-covariance value;

a second auto-covariance module for performing an auto-covariance operation without the time difference for the pilot signal, thereby outputting a second auto-covariance value;

a third auto-covariance module for performing an auto-covariance operation without the time difference for a square value of the pilot signal, thereby outputting a third auto-covariance value; and

a fourth auto-covariance module for performing an auto-covariance operation having the predetermined time difference for the square value of the pilot signal, thereby outputting a fourth auto-covariance value.

4. The velocity estimation apparatus as claimed in claim 3, wherein the second auto-covariance module comprises:

an instantaneous power calculation unit for calculating an instantaneous power value of the pilot signal; and

a first accumulator for accumulating an output value of the instantaneous power calculation unit a predetermined number of times, thereby outputting the second auto-covariance value.

5. The velocity estimation apparatus as claimed in claim 3, wherein the third auto-covariance module comprises:

an instantaneous power calculation unit for calculating an instantaneous power value of the pilot signal;

a second accumulator for accumulating a square value of an output value of the instantaneous power calculation unit a predetermined number of times; and

a third auto-covariance calculation unit for outputting the third auto-covariance value by means of the second auto-covariance value and an output value of the second accumulator.

6. The velocity estimation apparatus as claimed in claim 3, wherein the fourth auto-covariance module comprises:

an instantaneous power calculation unit for calculating an instantaneous power value of the pilot signal;

a third accumulator for accumulating a value a predetermined number of times, which is obtained by squaring difference between an output value of the instantaneous power calculation unit and a value having a predetermined time difference for the output value; and

a fourth auto-covariance calculation unit for obtaining the fourth auto-covariance value by means of an output value of the third accumulator and the third auto-covariance value.

7. The velocity estimation apparatus as claimed in claim 2, wherein the auto-covariance calculation unit comprises:

a first auto-covariance module for performing an auto-covariance operation having a predetermined time difference for the pilot signal, thereby outputting a first auto-covariance value;

a second auto-covariance module including an instantaneous power calculation unit for calculating an instantaneous power value of the pilot signal, and a first accumulator for outputting a second auto-covariance value by accumulating an output value of the instantaneous power calculation unit a predetermined number of times;

a third auto-covariance module including the instantaneous power calculation unit for calculating the instantaneous power value of the pilot signal, a second accumulator for accumulating a square value of an output value of the instantaneous power calculation unit a predetermined number of times, and a third auto-covariance calculation unit for outputting a third auto-covariance value by means of the second auto-covariance value and an output value of the second accumulator; and

a fourth auto-covariance module including a third accumulator for accumulating a value a predetermined number of times, which is obtained by squaring difference between an output value of the instantaneous power calculation unit and a value having a predetermined time difference for the output value, and a fourth auto-covariance calculation unit for obtaining a fourth auto-covariance value by means of an output value of the third accumulator and the third auto-covariance value.

8. A velocity estimation method in a communication system including a transmitter for transmitting signals through radio channels and a receiver for receiving the signals and restoring data, the method comprising the steps of:

separating a pilot signal from the received signal; and

calculating a movement velocity of the receiver by means of the separated pilot signal.

9. The velocity estimation method as claimed in claim 8, wherein the step of calculating the movement velocity by means of the pilot signal comprises:

estimating a maximum Doppler frequency by means of the pilot signal; and

converting the estimated maximum Doppler frequency into velocity information.

10. The velocity estimation method as claimed in claim 9, wherein the step of estimating the maximum Doppler frequency comprises the sub-steps of:

performing an auto-covariance operation for the pilot signal; and

obtaining the maximum Doppler frequency by means of auto-covariance values calculated through the auto-covariance operation.

11. The velocity estimation method as claimed in claim 10, wherein the step of calculating the auto-covariance values comprises:

performing an auto-covariance operation having a predetermined time difference for the pilot signal, thereby calculating a first auto-covariance value;

performing an auto-covariance operation without the time difference for the pilot signal, thereby calculating a second auto-covariance value;

performing an auto-covariance operation without the time difference for a square value of the pilot signal, thereby calculating a third auto-covariance value; and

performing an auto-covariance operation having the predetermined time difference for the square value of the pilot signal, thereby calculating a fourth auto-covariance value.

12. The velocity estimation method as claimed in claim 11, wherein the step of calculating the first auto-covariance value uses a real part and an imaginary part of the pilot signal.

13. The velocity estimation method as claimed in claim 11, wherein the step of calculating the second auto-covariance value comprises:

calculating an instantaneous power value of the pilot signal; and

accumulating the instantaneous power value of the pilot signal a predetermined number of times, thereby obtaining an auto-covariance value without the time difference for the pilot signal.

14. The velocity estimation method as claimed in claim 13, wherein the step of calculating the third auto-covariance value comprises:

calculating the instantaneous power value of the pilot signal;

accumulating the instantaneous power value of the pilot signal a predetermined number of times; and

obtaining the third auto-covariance value by means of the second auto-covariance value and a result value from the accumulation of the instantaneous power value,

wherein the third auto-covariance value is an auto-covariance value without the time difference for a square value of the pilot signal.

15. The velocity estimation method as claimed in claim 11, wherein the step of calculating the fourth auto-covariance value comprises:

calculating an instantaneous power value of the pilot signal;

accumulating a value a predetermined number of times, which is obtained by squaring difference between the instantaneous power value and a power value having a predetermined time difference for the instantaneous power value; and

obtaining the fourth auto-covariance value by means of the third auto-covariance value and a result value from the accumulation of the value,

wherein the fourth auto-covariance value is an auto-covariance value having the predetermined time difference for a square value of the pilot signal.

16. The velocity estimation method as claimed in claim 10, wherein the step of calculating the auto-covariance values:

obtaining a first auto-covariance value by performing an auto-covariance operation having a predetermined time difference by means of a real part and an imaginary part of the pilot signal;

obtaining a second auto-covariance value, which is an auto-covariance value without the time difference for the pilot signal, by calculating an instantaneous power value of the pilot signal and accumulating a received power value of the pilot signal a predetermined number of times;

obtaining a third auto-covariance value, which is an auto-covariance value without the time difference for a square value of the pilot signal, by accumulating a square value of the instantaneous power value a predetermined number of times and by using the second auto-covariance value and an output value from the accumulation; and

obtaining a fourth auto-covariance value, which is an auto-covariance value having the predetermined time difference for the square value of the pilot signal, by accumulating a predetermined value a predetermined number of times and using the third auto-covariance value and an output value from the accumulation, the predetermined value being obtained by squaring difference between the instantaneous power value and a power value having a predetermined time difference for the instantaneous power value.

17. The velocity estimation method as claimed in claim 9, wherein the maximum Doppler frequency is calculated by an below

$f_m=\frac{1}{2}$

π

τ

⁢

J 0 - 1 ⁡

( c x ⁡

( τ

) - c x 2 ⁡

( τ

) - c 

x 

2 ⁡

( τ

) c x ⁡

( 0 ) - c x 2 ⁡

( 0 ) - c 

x 

2 ⁡

( 0 ) ) ,

wherein ƒ

_m represents the maximum Doppler frequency, J₀( ) represents a zero order Bessel function of a first kind, c_x(0) represents an auto-covariance value without a time difference for a received signal, c_x(τ

) represents an auto-covariance value having a time difference τ

for the received signal, c_|x|2(0) represents an auto-covariance value without a time difference for a square value of the received signal, and c_|x|2(τ

) represents an auto-covariance value having the time delay τ

for the square value of the received signal.