Method and apparatus for controlling reverse link interference rise and power control instability in a wireless system
View Patent ↗A system and a method for reverse link power control in a wireless communications network generates power adjust commands for mobiles being served by a network base station in a centralized manner by considering overall system performance when an increased interference condition is detected. In one implementation, a base station power control processor adopts a modified reverse inner loop power control (RILPC) and/or a reverse outer loop power control (ROLPC) algorithm when an increased interference condition is detected. According to the modified RILPC algorithm, a percentage of power-up adjust commands which would normally be generated when E b /N o measurements for served mobiles do not meet target E b /N o levels are converted to power down-adjust commands, thereby forcing some mobiles to reduce transmit power, at least temporarily, to constrain interference. When the increased interference condition persists, the percentage of power-up adjust commands which are converted to power-down commands may be changed. According to the modified ROLPC algorithm, the power control processor adjusts target E b /N o levels in a centralized manner based on an overall system state so that only a limited number of target E b /N o levels are allowed to increase when frame erasures occur. By preventing a percentage of target E b /N o level increases, at least temporarily, when frame erasures occur, a percentage of power up-adjust commands are avoided. Therefore, a similar effect to that achieved by the modified RILPC is achieved. In accordance with still a further implementation of the present invention, the modified RILPC algorithm may be used in combination with the modified ROLPC algorithm to provide greater resistance to increased interference conditions.
1. A power control system for generating transmit power adjust commands in a wireless communications network, comprising:
detection means for detecting interference conditions; and
generating means for generating power adjust commands when said detection means detects an increased interference condition; and
converting means for converting power up-adjust commands to power down-adjust commands when the detection means detects an increased interference condition and a duration of said detected increased interference condition does not exceed a first time threshold.
2. The power control system of claim 1 , further configured for:
comparing a signal-to-interference measurement for a mobile with a target signal-to-interference level for the mobile;
generating a power down-adjust command when the signal-to-interference measurement for the mobile is greater than the target signal-to-interference level for the mobile; and
determining whether to generate a power down-adjust command when the signal-to-interference measurement for the mobile is less than the target signal-to-interference level for the mobile.
3. The power control system of claim 2 , further configured for:
judging whether an erasure frame has been received for the mobile; and
determining whether to adjust the target signal-to-interference level for the mobile when an erasure frame has been received for the mobile.
4. The power control system of claim 2 , wherein said power control system determines whether to generate a power down-adjust command when the signal-to-interference measurement for the mobile is less than the target signal-to-interference level for the mobile based on a statistical probability.
5. The power control system of 4 , wherein the statistical probability is variable.
6. The power control system of claim 1 , further configured for:
generating a power adjust command based on a comparison of a signal-to-interference measurement for the mobile and a target signal-to-interference level for the mobile;
judging whether an erasure frame has been received for the mobile; and
determining whether to adjust the target signal-to-interference level for the mobile when an erasure frame has been received for the mobile.
7. The power control system of claim 6 , wherein said power control system determines whether to adjust the target signal-to-interference level for the mobile when an erasure frame has been received for the mobile based on a statistical probability.
8. The power control system of claim 7 , wherein the statistical probability is variable.
9. The power control system of claim 1 , wherein said detection means monitors changes in total reverse link signal strength.
10. The power control system of claim 1 , wherein said detection means monitors a ratio of power up-adjust commands to power down-adjust commands.
11. The power control system of claim 1 , wherein said detection means monitors signal-to-interference levels for a plurality of mobiles.
12. The power control system of claim 1 , wherein said detection means monitors total reverse link signal strength.
13. The power control system of claim 1 , wherein the converting means is configured to convert a percentage of the power up-adjust commands to power down-adjust commands and dynamically modify the percentage.
14. The power control system of claim 13 , wherein the converting means is configured to modify a number of the power up-adjust commands converted to power down-adjust commands when the duration of the detected increased interference condition exceeds the first time threshold and does not exceed a second time threshold.
15. The power control system of claim 13 , wherein the power control system is configured to perform one of (i) a handdown operation and (ii) switching to a different transmit/receive frequency channel when the duration of the detected increased interference condition exceeds a second time threshold.
16. The power control system of claim 1 , wherein the detection means for detecting interference conditions uses the first time threshold and a second time threshold.
17. A method for generating transmit power adjust commands in a wireless communications network comprising:
detecting interference conditions;
selecting a first power control scheme when said detecting step does not detect an increased interference condition;
selecting a second power control scheme when said detecting step detects an increased interference condition; and
generating power adjust commands based on the selected power control scheme; and
converting power up-adjust commands to power down-adjust commands when detecting an increased interference condition and a duration of said detected increased interference condition does not exceed a first time threshold.
18. The method of claim 17 , wherein the second power control scheme is a modified reverse inner loop power control scheme.
19. The method of claim 17 , wherein the second power control scheme is a modified reverse outer loop power control scheme.
20. The method of claim 17 , further comprising:
modifying a number of the power up-adjust commands converted to power down-adjust commands in the converting step when the duration of the detected increased interference condition exceeds the first time threshold and does not exceed a second time threshold.
21. The method of claim 20 , further comprising:
performing one of (i) a handdown operation and (ii) switching to a different transmit/receive frequency channel when the duration of the detected increased interference condition exceeds the second time threshold.
22. The method of claim 17 , wherein the detecting step detects interference conditions using the first time threshold and a second time threshold.
23. A power control system for generating power adjust commands in a wireless communications network, comprising:
detection means for detecting interference conditions;
selecting means for selecting a first power control scheme when said detection means does not detect an increased interference condition and selecting a second power control scheme when said detection means detects an increased interference condition;
generating means for generating power adjust commands based on the power control scheme selected by said selecting means; and
converting means for converting power up-adjust commands to power down-adjust commands when detecting an increased interference condition and a duration of said detected increased interference condition does not exceed a first time threshold.
24. The power control system of claim 23 , wherein the second power control scheme is a modified reverse inner loop power control scheme.
25. The power control system of claim 23 , wherein the second power control scheme is a modified reverse outer loop power control scheme.
26. The power control system of claim 23 , wherein the converting means is configured to convert a percentage of the power up-adjust commands to power down-adjust commands and dynamically modify the percentage.
27. The power control system of claim 26 , wherein the converting means is configured to modify a number of the power up-adjust commands converted to power down-adjust commands when the duration of the detected increased interference condition exceeds the first time threshold and does not exceed a second time threshold.
28. The power control system of claim 26 , wherein the power control system is configured to perform one of (i) a handdown operation and (ii) switching to a different transmit/receive frequency channel when the duration of the detected increased interference condition exceeds the second time threshold.
29. The method of claim 23 , wherein the detection means for detecting interference conditions uses the first time threshold and a second time threshold.
30. A method for generating transmit power adjust commands in a wireless communication network comprising:
detecting interference conditions; and
converting power up-adjust commands to power down-adjust commands when detecting an increased interference condition and a duration of said detected increased interference condition does not exceed a first time threshold.
31. The method of claim 30 , wherein the converting is based upon statistical probabilities.
32. The method of claim 30 , wherein the converting converts a percentage of power up-adjust commands to power down-adjust commands.
33. The method of claim 30 , wherein the percentage of power up-adjust commands converted to power down-adjust commands is predetermined.
34. The method of claim 32 , further comprising:
dynamically modifying the percentage.
35. The method of claim 34 , wherein the dynamically modifying comprises: adjusting the percentage based upon at least one of (i) a level of the increased interference condition and (ii) a duration of the increased interference condition.
36. The method of claim 30 , further comprising:
modifying a number of the power up-adjust commands converted to power down-adjust commands in the converting step when the duration of the detected increased interference condition exceeds the first time threshold and does not exceed a second time threshold.
37. The method of claim 36 , wherein the number is a percentage value and the modifying step comprises:
adjusting the percentage value based upon at least one of (i) a level of the increased interference condition and (ii) a duration of the increased interference condition.
38. The method of claim 36 , further comprising:
performing one of (i) a handdown operation and (ii) switching to a different transmit/receive frequency channel when the duration of the detected increased interference condition exceeds the second time threshold.
39. The method of claim 30 , wherein the detecting step detects interference conditions using the first time threshold and a second time threshold.
40. The method of claim 30 , further comprising:
comparing a signal-to-interference measurement for a mobile with a target signal-to-interference level for the mobile;
generating a power down-adjust command when the signal-to-interference measurement for the mobile is greater than the target signal-to-interference level for the mobile; and
determining whether to generate a power down-adjust command when the signal-to-interference measurement for the mobile is less than the target signal-to-interference level for the mobile.
41. The method of claim 40 , wherein said determining step determines whether to generate a power down-adjust command when the signal-to-interference measurement for the mobile is less than the target signal-to-interference level for the mobile based on a statistical probability.
42. The method of claim 41 , wherein the statistical probability is variable.
43. The method of claim 40 , comprising:
judging whether an erasure frame has been received for the mobile; and
determining whether to adjust the target signal-to-interference level for the mobile when an erasure frame has been received for the mobile.
44. The method of claim 30 , further comprising:
generating power adjust commands based on a comparison of a signal-to-interference measurement for a mobile and a target signal-to-interference level for the mobile;
judging whether an erasure frame has been received for the mobile; and
determining whether to adjust the target signal-to-interference level for the mobile when an erasure frame has been received for the mobile.
45. The method of claim 44 , wherein said determining step determines whether to adjust the target signal-to-interference level for the mobile when an erasure frame has been received for the mobile based on a statistical probability.
46. The method of claim 45 , wherein the statistical probability is variable.
47. The method of claim 30 , wherein said detecting step monitors changes in total reverse link signal strength at a base station.
48. The method of claim 30 , wherein said detecting step monitors absolute total reverse link signal strength.
49. The method of claim 30 , wherein said detecting step monitors a ratio of power up-adjust commands to total power adjust commands.
50. The method of claim 30 , wherein said detecting step monitors signal-to-interference levels for a plurality of mobiles.