Power control avoiding outer loop wind-up

• US 7,734,309 B2
• Filed: 05/18/2007
• Issued: 06/08/2010
• Est. Priority Date: 02/04/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Kasturi, Nitin, Subrahmanya, Parvathanathan, Shiu, Da-Shan, Chi, Richard
• Primary Examiner(s): Tran; CongVan
• Application Number:
  US11/750,938
• Publication Number:
  US 20070218935A1
• Time in Patent Office: 1,117 Days
• Field of Search: 455/522, 455/68, 455/69, 455/70, 455/67.11, 455/67.13, 455/422.1, 455/13.4, 370/318
• US Class Current: 455/522
• CPC Class Codes: H04W 52/12 Outer and inner loops
• CPC Class Codes: H04W 52/20 using error rate
• CPC Class Codes: H04W 52/221 using past power control commands
• CPC Class Codes: H04W 52/228 using past power values or information
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/248 where transmission power control commands are generated based on a path parameter
• CPC Class Codes: H04W 52/36 with a discrete range or set of values, e.g. step size, ramping or offsets

Abstract

Techniques for power control that avoids outer loop wind-up are disclosed. In one aspect, wind-up of a target power level is detected, and the target power level is modified in response. In another aspect, unwinding of the target power level is detected, after which the target power level is determined without considering wind-up. Various other aspects are also presented, including wind-up and unwinding detection procedures, and target power level modification procedures. These aspects have the benefit of reducing the time that transmit power exceeds that which is necessary, thus increasing system capacity and performance, and mitigating misallocation of system resources.

Claims

1. A. method of power control comprising:

sending power control commands to adjust a transmit power of a remote station, the power control commands based on a target power parameter;

detecting a condition wherein a measured power parameter does not track the target power parameter in response to a sent power control command, wherein detecting the condition comprises comparing the target power parameter with a filtered measured power parameter;

operating an outer power control loop according to one of a normal mode or a wind-up mode based on whether the condition is detected; and

modifying the target power parameter when the condition is detected.

2. A method comprising:

sending power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

during a normal state, setting the outer loop target according to a normal outer loop power control scheme, detecting a wind-up condition in response to a sent power control command, and, upon such detection, exiting the normal state and entering a wind-up state; and

during the wind-up state, setting the outer loop target according to a wind-up scheme;

the detecting the wind-up condition comprising determining if the outer loop target exceeds a measured signal-to-interference ratio by a threshold.

3. The method of claim 2, further comprising filtering the measured signal-to-interference ratio before determining if the outer loop target exceeds a measured signal-to-interference ratio by a threshold.

4. The method of claim 2, wherein setting the outer loop target according to the wind-up scheme comprises capping a target Signal to Interference Ratio (SIR) as a function of a measured SIR value.

5. The method of claim 2, wherein setting the outer loop target according to the wind-up scheme comprises freezing a. target Signal to Interference Ratio (SIR) to a pre-determined level.

6. The method of claim 2, wherein setting the outer loop target according to the wind-up scheme comprises modifying a step size associated with a power control command relative to a step size in the normal state.

7. The method of claim 6, further comprising setting a higher target error rate than is used in the normal state.

8. The method of claim 2, wherein setting the outer loop target according to the wind-up scheme comprises limiting a slew rate of changes to the outer rate target.

9. The method of claim 2, further comprising detecting an unwind state when in the wind-up state and exiting the wind-up state and returning to the normal state.

10. A method comprising:

sending power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

during a normal state, setting the outer loop target according to a normal outer loop power control scheme, detecting a wind-up condition in response to a sent power control command, and, upon such detection, exiting the normal state and entering a wind-up state; and

during the wind-up state, setting the outer loop, target according to a wind-up scheme;

the detecting the wind-up condition comprising testing, against a threshold, a received energy per chip over interference ratio.

11. A method comprising:

sending power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

during a normal state, setting the outer loop target according to a normal outer loop power control scheme, detecting a wind-up condition in response to a sent power control command, and, upon such detection, exiting the normal state and entering a wind-up state; and

during the wind-up state, setting the outer loop target according to a wind-up scheme;

the wind-up scheme comprising decreasing the outer loop target by a first step size when a frame is incorrectly received, and decreasing the outer loop target by a second step size when a frame is correctly received, the second step size being larger than the first step size.

12. A method comprising:

sending power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

during a normal state, setting the outer loop target according to a normal outer loop power control scheme, detecting a wind-up condition in response to a sent power control command, and, upon such detection, exiting the normal state and entering a wind-up state; and

during the wind-up state, setting the outer loop target according to a wind-up scheme;

the normal outer loop power control scheme comprising increasing the outer loop target by a first step size when a frame is incorrectly received, and decreasing the outer loop target by a second step size when a frame is correctly received;

the wind-up scheme comprising increasing the outer loop target by a third step size when a frame is incorrectly received, and decreasing the outer loop target by a fourth step size when a frame is correctly received, the ratio of the third step size to the fourth step size being larger than the ratio of the first step size to the second step size.

13. A wireless communication device, operable with a second wireless communication device to perform closed-loop power control, comprising:

a wind-up detector for detecting wind-up of a target power level;

an outer loop power control loop for generating a target power level according to one of a normal mode or a wind-up mode and modifying the target power level in response to wind-up detection in the wind-up detector,

the wind-up detection comprising measuring an error rate over a predetermined period and comparing the error rate with an error rate threshold.

14. A wireless communication device, operable with a second wireless communication device to perform closed-loop power control, comprising:

a wind-up detector for detecting wind-up of a target power level;

an outer loop power control loop for generating a target power level and modifying it according to a wind-up scheme in response to wind-up detection in the wind-up detector;

the wind-up scheme comprising decreasing the outer loop set-point by a first step size when a frame is incorrectly received, and decreasing the outer loop set-point by a second step size when a frame is correctly received, the second step size being larger than the first step size.

15. A wireless communication device, operable with a second wireless communication device to perform closed-loop power control, comprising:

a wind-up detector for detecting wind-up of a target power level;

an outer loop power control loop for generating a target power level according to a normal outer loop power control scheme, and modifying the target power level according to a wind-up scheme in response to wind-up detection in the wind-up detector;

the normal outer loop power control scheme comprising increasing the outer loop target by a first step size when a frame is incorrectly received, and decreasing. the outer loop target by a second step size when a frame is correctly received;

the wind-up scheme comprising increasing the outer loop set-point by a third step size when a frame is incorrectly received, and decreasing the outer loop set-point by a fourth step size when a frame is correctly received, the ratio of the third step size to the fourth step size being larger than the ratio of the first step size to the second step size.

16. A communication system comprising:

a wind-up detector for detecting wind-up of a target power level;

an outer loop power control loop for generating a target power level according to one of a normal mode or a wind-un mode, and modifying it in response to wind-up detection in the wind-up detector;

the wind-up detection comprising measuring an error rate over a predetermined period and comparing the error rate with an error rate threshold.

17. A communication system comprising:

a wind-up detector for detecting wind-up of a target power level;

an outer loop power control loop for generating a target power level according to one of a normal mode or a wind-up mode, and modifying it in response to wind-up detection in the wind-up detector;

the wind-up detection comprising measuring a Signal to Interference Ratio (SIR) and comparing a sum of the measured SIR with a wind-up detection margin to a target SIR.

18. A computer program product including a computer readable medium having instructions for causing a computer to:

send power control commands to adjust a transmit power of a remote station, the power control commands based on a target power parameter;

detect a condition wherein a measured power parameter does not track the target power parameter in response to a sent power control command;

operate an outer power control loon according to one of a normal mode or a wind-up mode based on whether the condition is detected; and

modify the target power parameter when the condition is detected, wherein the causing the computer to detect the condition comprises causing the computer to measure an error rate over a predetermined period and to compare the error rate with an error rate threshold.

19. A computer program product including a computer readable medium having instructions for causing a computer to:

send power control commands to adjust a transmit power of a remote station, the power control commands based on a target power level;

detect a wind-up condition; and

limit a power control slew rate in the wind-up condition to limit number of target power level increases to a pre-determined maximum number within a period of pre-determined length.

20. A communication system comprising:

means for sending power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

means for setting the outer loop target, during a normal state, according to a normal outer loop power control scheme;

means for detecting a wind-up condition in response to a sent power control command, and, upon such detection, exiting the normal state and entering a wind-up state; and

means for setting the outer loop target, during the wind-up state, according to a wind-up scheme;

the means for detecting the wind-up condition comprising means for determining if the outer loop target exceeds a measured signal-to-interference ratio by a threshold.

21. A communication system comprising:

means for sending power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

means for setting the outer loop target, during a normal state, according to a normal outer loop power control scheme;

means for detecting a wind-up condition in response to a sent power control command, and, upon such detection, exiting the normal state and entering a wind-up state; and

means for setting the outer loop target, during the wind-up state, according to a wind-up scheme;

the means for detecting the wind-up condition comprising means for testing, against a threshold, a received energy per chip over interference ratio.

22. A communication system comprising:

means for sending power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

means for setting the outer loop target, during a normal state, according to a normal outer loop power control scheme;

means for detecting a wind-up condition in response to a sent power control command, and, upon such detection, exiting the normal state and entering a wind-up state; and

means for setting the outer loop target, during the wind-up state, according to a wind-up scheme;

the wind-up scheme comprising decreasing the outer loop target by a first step size when a frame is incorrectly received, and decreasing the outer loop target by a second step size when a frame is correctly received, the second step size being larger than the first step size.

23. A communication system comprising:

means for sending power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

means for setting the outer loop target, during a normal state, according to a normal outer loop power control scheme;

means for detecting a wind-up condition in response to a sent power control command, and, upon such detection, exiting the normal state and entering a wind-up state; and

means for setting the outer loop target, during the wind-up state, according to a wind-up scheme;

the normal outer loop power control scheme comprising increasing the outer loop target by a first step size when a frame is incorrectly received, and decreasing the outer loop target by a second step size when a frame is correctly received;

the wind-up scheme comprising increasing the outer loop target by a third step size when a frame is incorrectly received, and decreasing the outer loop target by a fourth step size when a frame is correctly received, the ratio of the third step size to the fourth step size being larger than the ratio of the first step size to the second step size.

24. A computer program product including a computer readable medium having instructions for causing a computer to:

send power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

during a normal state, set the outer loop target according to a normal outer loop power control scheme, detect a wind-up condition in response to a sent power control command, and, upon such detection, exit the normal state and enter a wind-up state; and

during the wind-up state, set the outer loop target according to a wind-up scheme;

wherein detecting the wind-up condition comprises determining if the outer loop target exceeds a measured signal-to-interference ratio by a threshold.

25. A computer program product including a computer readable medium having instructions for causing a computer to:

send power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

during a normal state, set the outer loop target according to a normal outer loop power control scheme, detect a wind-up condition in response to a sent power control command, and, upon such detection, exit the normal state and entering a wind-up state; and

during the wind-up state, set the outer loop target according to a wind-up scheme;

wherein detecting the wind-up condition comprises testing, against a threshold, a received energy per chip over interference ratio.

26. A computer program product including a computer readable medium having instructions for causing a computer to:

send power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

during a normal state, set the outer loop target according to a normal outer loop power control scheme, detect a wind-up condition in response to a sent power control command, and, upon such detection, exit the normal state and entering a wind-up state; and

during the wind-up state, set the outer loop target according to a wind-up scheme;

the wind-up scheme comprising decreasing the outer loop target by a first step size when a frame is incorrectly received, and decreasing the outer loop target by a second step size when a frame is correctly received, the second step size being larger than the first step size.

27. A computer program product including a computer readable medium having instructions for causing a computer to:

send power control commands to adjust a transmit power of a remote station, the power control commands based on an outer loop target;

during a normal state, set the outer loop target according to a normal outer loop power control scheme, detect a wind-up condition in response to a sent power control command, and, upon such detection, exit the normal state and entering a wind-up state; and

during the wind-up state, set the outer loop target according to a wind-up scheme;

the normal outer loop power control scheme comprising increasing the outer loop target by a first step size when a frame is incorrectly received, and decreasing the outer loop target by a second step size when a frame is correctly received;

the wind-up scheme comprising increasing the outer loop target by a third step size when a frame is incorrectly received, and decreasing the outer loop target by a fourth step size when a frame is correctly received, the ratio of the third step size to the fourth step size being larger than the ratio of the first step size to the second step size.