Method and apparatus for determining the closed loop power control set point in a wireless packet data communication system

• US 7,088,957 B2
• Filed: 08/28/2003
• Issued: 08/08/2006
• Est. Priority Date: 08/06/1999
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Black, Peter J., Ling, Fuyun
• Primary Examiner(s): Nguyen, Simon
• Application Number:
  US10/651,834
• Publication Number:
  US 20040062225A1
• Time in Patent Office: 1,076 Days
• Field of Search: 455/69, 455/522, 455/67.11, 455/13.4, 370/318, 370/335, 370/342
• US Class Current: 455/67.11
• CPC Class Codes: H04W 52/12 Outer and inner loops
• CPC Class Codes: H04W 52/20 using error rate
• CPC Class Codes: H04W 52/225 Calculation of statistics, e.g. average, variance
• CPC Class Codes: H04W 52/282 taking into account the speed of the mobile
• CPC Class Codes: H04W 52/286 during data packet transmission, e.g. high speed packet access [HSPA]
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

According to one aspect of the invention, a method for determining a power control set point is provided. In one embodiment, the power control set point is determined based on one or more factors including a first factor corresponding to a pilot bit error rate, a second factor corresponding to a normalized signal variance, and a third factor corresponding to an average number of fingers in lock.

Claims

1. A method for determining a power control set point, comprising:

receiving a pilot signal;

calculating a pilot bit error rate based on the received pilot signal;

calculating a normalized signal variance based on the received pilot signal;

calculating an average number of fingers in lock based on the received pilot signal; and

calculating the power control set point based one or more factors including a first factor corresponding to the pilot bit error rate, a second factor corresponding to the normalized signal variance, and a third factor corresponding to the average number of fingers in lock.

2. The method of claim 1 wherein calculating the pilot bit error rate includes:

despreading the received pilot signal to generate despread pilot samples;

demodulating the despread pilot samples to generate demodulated pilot samples;

generating demodulated pilot symbols based on the demodulated pilot samples; and

comparing the demodulated pilot symbols to a first predetermined threshold value.

3. The method of claim 2 wherein calculating the normalized signal variance includes:

computing a first value corresponding to an average of the squared energy of the demodulated pilot symbols;

computing a second value corresponding to a square of the average energy of the demodulated pilot symbols; and

computing the normalized signal variance based on the first value corresponding to the average of the square energy of the demodulated pilot symbols and the second value corresponding to the square of the average energy of the demodulated pilot symbols.

4. The method of claim 1 wherein calculating the power control set point includes:

generating a metric as a function of the first, second, and third factors; and

determining an error rate based on the metric and a second predetermined threshold value.

5. The method of claim 1 wherein calculating the average number of fingers in lock comprises:

determining, for each demodulated finger, whether the respective demodulated finger is in lock based on a signal strength of the respective demodulated finger and a third predetermined threshold value.

6. The method of claim 4 wherein the metric is modified by one or more scaling factors corresponding to a linear function of the average number of fingers in lock.

7. The method of claim 6 wherein the metric is generated according to the following formula:

η

(n)=PBER(n−

1)+α

₁ρ

(n−

1)+α

₂N_f(n−

1),

where η

(n) represents the metric for a current (nth) frame, PBER(n−

1) represents the pilot bit error rate for a previous ((n−

1)th) frame, ρ

(n−

1) represents the pilot signal variance for the previous ((n−

1)th) frame, N_f(n−

1) represents the average number of fingers in lock in the previous frame, and α

₁ and α

₂ represents first and second scaling factors.

8. An apparatus for determining a power control set point, comprising:

means for receiving a pilot signal;

means for calculating a pilot bit error rate based on the received pilot signal;

means for calculating a normalized signal variance based on the received pilot signal;

means for calculating an average number of fingers in lock based on the received pilot signal; and

means for calculating the power control set point based one or more factors including a first factor corresponding to the pilot bit error rate, a second factor corresponding to the normalized signal variance, and a third factor corresponding to the average number of fingers in lock.

9. The apparatus of claim 8 wherein means for calculating the pilot bit error rate includes:

means for despreading the received pilot signal to generate despread pilot samples;

means for demodulating the despread pilot samples to generate demodulated pilot samples;

means for generating demodulated pilot symbols based on the demodulated pilot samples; and

means for comparing the demodulated pilot symbols to a first predetermined threshold value.

10. The apparatus of claim 9 wherein means for calculating the normalized signal variance includes:

means for computing an average of the squared energy of the demodulated pilot symbols;

means for computing a square of the average energy of the demodulated pilot symbols; and

means for computing the normalized signal variance based on the average of the squared energy of the demodulated pilot symbols and the square of the average energy of the demodulated pilot symbols.

11. The apparatus of claim 8 wherein means for calculating the power control set point includes:

means for generating a metric as a function of the first, second, and third factors; and

means for determining an error rate based on the metric and a second predetermined threshold value.

12. The apparatus of claim 8 wherein means for calculating the average number of fingers in lock comprises:

means for determining, for each demodulated finger, whether the respective demodulated finger is in lock based on a signal strength of the respective demodulated finger and a third predetermined threshold value.

13. The apparatus of claim 11 wherein the metric is modified by a scaling factor corresponding to a linear function of the average number of fingers in lock.

14. The apparatus of claim 13 wherein the metric is generated according to the following formula:

η

(n)=PBER(n−

1)+α

₁ρ

(n−

1)+α

₂N_f(n−

1),

where η

(n) represents the metric for a current (nth) frame, PBER(n−

1) represents the pilot bit error rate for a previous ((n−

1)th) frame, ρ

(n−

1) represents the pilot signal variance for the previous ((n−

1)th) frame, N_f(n−

1) represents the average number of fingers in lock in the previous frame, and α

₁ and α

₂ represents first and second scaling factors.

15. An apparatus for determining a power control set point, comprising:

a receiver to receive a pilot symbol stream comprising one or more pilot symbols;

one or more metric calculators coupled to the receiver, each metric calculator to demodulate the received pilot symbols to generate demodulated pilot symbols, compute energy of the received pilot symbols, and determine whether a finger corresponding to the respective metric calculator is in lock;

an error detector unit to determine a pilot bit error rate based on the demodulated pilot symbols and a predetermined pilot symbol sequence;

a variance calculator to compute a normalized signal variance based on the energy of the received pilot symbols; and

a set point calculator to calculate the power control set point based on a first factor corresponding to the pilot bit error rate, a second factor corresponding to the normalized signal variance, and a third factor corresponding to an average number of fingers in lock.

16. The apparatus of claim 15 wherein each calculator comprises:

a demodulator to demodulate the received pilot symbols;

an energy calculator to compute the energy of the received pilot symbols; and

a lock detector to determine whether the finger corresponding to the respective metric calculator is in lock.

17. The apparatus of claim 15 wherein the power control set point is calculated based on a metric corresponding to a function of the first, second, and third factors.

18. The apparatus of claim 17 wherein the metric is modified by a scaling factor corresponding to a linear function of the average number of fingers in lock.

19. The apparatus of claim 15 wherein the metric is generated according to the following formula:

η

(n)=PBER(n−

1)+α

₁ρ

(n−

1)+α

₂N_f(n−

1),

where η

(n) represents the metric for a current (nth) frame, PBER(n−

1) represents the pilot bit error rate for a previous ((n−

1)th) frame, ρ

(n−

1) represents the pilot signal variance for the previous ((n−

1)th) frame, N_f(n−

1) represents the average number of fingers in lock in the previous frame, and α

₁ and α

₂ represents first and second scaling factors.