Method for determining fading correction factor in a communication system

• US 6,256,338 B1
• Filed: 11/30/1998
• Issued: 07/03/2001
• Est. Priority Date: 11/30/1998
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Yousef, Nabil, Jalloul, Louay
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): Nguyen, Phuongchau Ba
• Application Number:
  US09/201,185
• Time in Patent Office: 946 Days
• Field of Search: 370/335, 370/342, 375/140, 375/142, 375/144, 375/150, 455/10, 455/504, 455/506
• US Class Current: 375/142
• CPC Class Codes: H04B 1/7113 Determination of path profile
• CPC Class Codes: H04B 1/7117 Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers
• CPC Class Codes: H04B 17/364 Delay profiles
• CPC Class Codes: H04B 17/391 Modelling the propagation channel
• CPC Class Codes: H04B 7/005 Control of transmission; Equalising

Abstract

A method for determining a fading correction factor to be used for correcting a sample of a power delay profile of a received signal in a communication system, the fading correction factor associated with a fading channel characteristic through which the received signal propagates, includes estimating a number (N) of complex samples, obtaining fading channel autocorrelation sequence (R(n)) of the fading channel for a plurality (n) of complex samples, the number of the plurality (n) of complex samples corresponding to the number (N) of complex samples, and computing the fading correction factor based on the number (N) of complex samples, autocorrelation sequence (R(n)), and the number of the plurality (n) of complex samples.

Claims

1. A method for determining a fading correction factor to be used for correcting a sample of a power delay profile of a received signal in a communication system, said fading correction factor associated with a fading channel characteristic through which said received signal propagates, comprising the steps of:

estimating a number (N) of complex samples;

obtaining fading channel autocorrelation sequence (R(n)) of said fading channel for a plurality (n) of complex samples, the number of said plurality (n) of complex samples corresponding to said number (N) of complex samples;

computing said fading correction factor based on said number (N) of complex samples, said autocorrelation sequence (R(n)), and the number of said plurality (n) of complex samples wherein said computing, said fading correction factor is computed according to an equation $N·<br><br>{\left[R<br><br>\left(0\right)+\underset{n=1}{\overset{N-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>2<br><br>\left(N-n\right)<br><br>R<br><br>\left(n\right)/N\right]}^{-1}.$

3. The method as recited in claim 1 wherein said estimating said number (N) of complex samples includes estimating an optimum number (Nopt) of complex samples, and substituting said (Nopt) for said (N).

4. The method as recited in claim 3 wherein said estimating said optimum number (Nopt) of complex samples including:

a. estimating an initial number (Nint) of complex samples;

b. obtaining fading channel autocorrelation sequence (R(n)) corresponding to said initial number (Nint) of complex samples;

c. computing a constant (K) based on said autocorrelation sequence (R(n)) and the number of said plurality (n) of complex samples;

d. substituting said initial number (Nint) of complex samples for said optimum number (Nopt) of complex samples if said constant (K) is equal or substantially equal to zero.

5. The method as recited in claim 4 further comprising the steps of:

repeating steps “

a-d”

until said constant (K) is computed to be equal or substantially equal to zero in said computing step, wherein each time a different said initial number (Nint) of complex samples is used in said computing step;

substituting a final said initial number (Nint) of complex samples in said repeating step for said optimum number (Nopt) of complex samples.

6. The method as recited in claim 4 wherein said computing, said constant (K) is computed according to:

$\underset{n=1}{\overset{\mathrm{Nint}-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{nR}<br><br>\left(n\right)=K.$

7. The method as recited in claim 1 wherein said obtaining fading channel autocorrelation sequence (R(n)) includes estimating a maximum Doppler frequency.

11. The method as recited in claim 1 further comprising the step of demodulating said received signal prior to said computing step.

12. The method as recited in claim 1 wherein said communication system is a code division multiple access communication system.

2. A method for determining a fading correction factor to be used for correcting a sample of a power delay profile of a received signal in a communication system, said fading correction factor associated with a fading channel characteristic through which said received signal propagates, comprising the steps of:

estimating a number (N) of complex samples;

obtaining fading channel autocorrelation sequence (R(n)) of said fading channel for a plurality (n) of complex samples, the number of said plurality (n) of complex samples corresponding to said number (N) of complex samples;

computing said fading correction factor based on said number (N) of complex samples, said autocorrelation sequence (R(n)), and the number of said plurality (n) of complex samples, wherein said computing, said fading correction factor is computed according to an equation $N·<br><br>{\left[R<br><br>\left(0\right)+\underset{n=1}{\overset{N-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>2<br><br>\left(N-n\right)<br><br>R<br><br>\left(n\right)/N\right]}^{-1};<br><br>$

and

scaling said sample of said power delay profile of said received signal proportional to said fading correction factor to produce a corrected sample of said power delay profile of said received signal.

8. The method as recited in claim 2 further comprising the steps of:

estimating a noise factor based on said received signal;

in addition to said scaling proportional to said fading correction factor, scaling said sample of power delay profile of said received signal proportional to said noise factor to produce said corrected sample of said power delay profile of said received signal.

9. The method as recited in claim 8 wherein said estimating said noise factor is based on said number (N) of complex samples.

10. The method as recited in claim 2 further comprising the step of producing said power delay profile of said received signal including at least one corrected sample of said power delay profile of said received signal.