Transmit power control time delay compensation in a wireless communications system

• US 6,493,541 B1
• Filed: 07/02/1999
• Issued: 12/10/2002
• Est. Priority Date: 07/02/1999
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Gustafsson, Fredrik, Gunnarsson, Fredrik, Wiberg, Niclas
• Primary Examiner(s): Vo, Nguyen T.
• Assistant Examiner(s): Ly, Nghi H.
• Application Number:
  US09/346,316
• Time in Patent Office: 1,257 Days
• Field of Search: 455/69, 455/522, 455/63, 455/67.1, 455/67.3, 375/346
• US Class Current: 455/69
• CPC Class Codes: H04W 52/221 using past power control commands
• CPC Class Codes: H04W 52/223 predicting future states of the transmission

Abstract

The present invention compensates for transmit power control time delays between a radio transmitter and receiver that adversely affect the transmit power control process. A time delay associated with a power control loop is compensated for by adjusting a detected signal quality value of a received signal, e.g., signal-to-interference ratio (SIR), based on one or more previous power control commands already sent but whose effect has not yet been experienced. Because the determined signal quality value of the received signal is adjusted based on one or more power control commands already sent but yet to take effect, the transmit power level control command is appropriately determined so that it also takes into account a power control loop time delay. The delay compensation value may be determined based on the output power of a single, previously generated transmit power control command, or on plural previously generated transmit power control commands, depending upon the length of the time delay. If the adjusted signal quality parameter exceeds the target signal quality parameter, the generated power control command directs a decrease in transmit power, and the compensation factor causes a decrease in the subsequently determined signal quality parameter. If the adjusted signal quality parameter is less than the target signal quality parameter, the generated power control command directs an increase in transmit power, and the compensation factor causes an increase in the subsequently determined signal quality parameter.

Claims

1. A method for use in controlling a transmit power of a radio transmitter, comprising:

determining a signal-to-interference ratio (SIR) of a signal received from the transmitter;

determining an SIR adjustment using one or more previously-transmitted power commands;

adjusting the determined SIR using the SIR adjustment; and

generating a power control command using the adjusted SIR.

2. The method in claim 1, wherein the SIR adjustment is determined using the one or more previously transmitted power commands and an incremental transmit power.

3. The method in claim 2, wherein the incremental transmit power may be negative or positive.

4. The method in claim 2, wherein the adjusted SIR equals a measured SIR added to a product of an incremental power increase or decrease value and a sign of a most recent transmit power command.

5. The method in claim 4, wherein the incremental value is a fixed constant or a variable.

6. The method in claim 1, further comprising:

comparing the adjusted SIR to a target SIR,

wherein the power control command is generated in response to the comparison.

7. The method in claim 1, wherein if the adjusted SIR exceeds the target SIR, the generated power control command directs a decrease in transmit power.

8. The method in claim 1, wherein if the adjusted SIR is less than the target SIR, the generated power control command directs an increase in transmit power.

9. The method in claim 1, wherein the SIR adjustment compensates for a time delay associated with controlling the transmit power of the radio transmitter.

10. The method in claim 9, wherein as a delay associated with the power control command decreases, a number of power control commands used to determine the SIR adjustment decreases, and as a delay associated with the power control command increases, the number of power control commands used to determine the SIR adjustment increases.

11. The method in claim 1 implemented in a base station used to control a transmit power level of the radio transmitter in a mobile station.

12. The method in claim 1 implemented in a mobile station used to control a transmit power level of the radio transmitter in a base station.

13. Apparatus for use in controlling a transmit power of a radio transmitter, comprising:

means for determining a signal-to-interference ratio (SIR) of a signal received from the transmitter;

means for determining an SIR adjustment using one or more previously-transmitted power commands;

means for adjusting the determined SIR using the SIR adjustment; and

means for generating a power control command using the adjusted SIR.

14. The apparatus in claim 13, wherein the SIR adjustment is determined using the one or more previously transmitted power commands and an incremental transmit power.

15. The apparatus in claim 14, wherein the incremental transmit power may be negative or positive.

16. The apparatus in claim 14, wherein the adjusted SIR equals a measured SIR added to a product of an incremental power increase or decrease value and a sign of a most recent transmit power command.

17. The apparatus in claim 16, wherein the incremental value is a fixed constant or a variable.

18. The apparatus in claim 13, further comprising:

comparing the adjusted SIR to a target SIR,

wherein the power control command is generated in response to the comparison.

19. The apparatus in claim 13, wherein the SIR adjustment compensates for a time delay associated with controlling the transmit power of the radio transmitter.

20. The apparatus in claim 19, wherein as a delay associated with the power control command decreases, a number of power control commands used to determine the SIR adjustment decreases, and as a delay associated with the power control command increases, the number of power control commands used to determine the SIR adjustment increases.

21. A radio station for use in a mobile radio communications system, comprising:

a radio transmitter for transmitting power control commands to another radio station;

a radio receiver for receiving a signal transmitted by the other radio station;

a detector for detecting a signal-to-interference (SIR) associated with the received signal;

a processor configured to;

predict an effect of a power control command on the detected SIR assuming the power control command had already taken effect,

adjust the detected SIR using the predicted effect, and

generate a transmit power control command taking into account the predicted effect,

wherein the prediction and the adjustment compensate for a time delay associated with controlling the transmit power of the radio transmitter.

22. The radio station in claim 21, wherein the processor is configured to predict the effect plural power control commands would have assuming plural power control commands had already been received and implemented in the transmitter.

23. The radio station in claim 21, wherein the generated power control command includes a first command for increasing the transmit power level by an incremental value and a second command for decreasing the transmit power level by an incremental value.

24. The radio station in claim 23, wherein the incremental value is a fixed constant.

25. The radio station in claim 23, wherein the incremental value is a variable.

27. The radio station in claim 21, wherein the generated power control command includes a new transmit power level value.

28. The radio station in claim 21, wherein if the adjusted SIR exceeds the target SIR, the generated power control command directs a decrease in transmit power.

29. The radio station in claim 21, wherein if the adjusted SIR is less than the target SIR, the generated power control command directs an increase in transmit power.

31. The radio station in claim 21, wherein the radio station is a base station and the other radio station is a mobile station.

32. The radio station in claim 21, wherein the radio station is a mobile station and the other radio station is a base station.

33. The radio station in claim 21, wherein the prediction of the effect of the power control commands accounts for limitations to transmit output power of the other radio station.

26. A radio station for use in a mobile radio communications system, comprising:

a radio transmitter for transmitting power control commands to another radio station;

a radio receiver for receiving a signal transmitted by the other radio station;

a detector for detecting a signal-to-interference (SIR) associated with the received signal;

a processor configured to;

predict an effect of a power control command on the detected SIR assuming the power control command had already taken effect,

generate a transmit power control command taking into account the predicted effect, and

adjust the detected SIR using a prior SIR, a previously-transmitted power command, and an incremental transmit power.

30. A radio station for use in a mobile radio communications system, comprising:

a radio transmitter for transmitting power control commands to another radio station;

a radio receiver for receiving a signal transmitted by the other radio station;

a detector for detecting a signal-to-interference (SIR) associated with the received signal;

a processor configured to;

predict an effect of a power control command on the detected SIR assuming the power control command had already taken effect,

generate a transmit power control command taking into account the predicted effect, and

adjust the detected SIR using the predicted effect and wherein the generated power control command is generated based on the adjusted SIR,

wherein as a delay associated with the power control command decreases, a number of power control commands used to determine the adjusted SIR decreases, and as a delay associated with the power control command increases, the number of power control commands used to determine the adjusted SIR increases.

34. Amended) A method for use in a mobile radio communications system, comprising:

transmitting from a first radio station to a second radio station power control commands;

receiving a signal transmitted by the second radio station;

detecting a signal-to-interference (SIR) associated with the received signal;

predicting an effect of the transmitted power control command on the detected SIR assuming the transmitted power control command had already taken effect;

adjusting the detected SIR using the predicted effects, and

generating the power control command taking into account the predicted effect,

wherein the prediction and the adjustment compensate for a time delay associated with controlling the transmit power of the radio transmitter.

35. The method in claim 34 further comprising:

predicting the effect plural power control commands would have assuming plural power control commands had already been received and implemented in the transmitter.

36. A radio station for sending information over a radio channel in a mobile radio communications system, comprising:

a radio transmitter for transmitting power control commands to another radio station;

a radio receiver for receiving a signal transmitted by the other radio station;

a detector for detecting a signal-to-interference (SIR) associated with the received signal;

a predictor for predicting an SIR of a future received signal including a power control model for modeling parameters that influence a power control process and for generating a predicted SIR;

a delay for delaying the predicted SIR and providing a delayed predicted SIR;

a differencer for determining a difference between the predicted SIR and the delayed SIR;

a first summer for summing the difference with the predicted SIR to produce an SIR compensation factor;

a second summer for summing the SIR compensation factor with the detected SIR to produce a compensated SIR; and

a power control command generator for generating a power control command using the compensated SIR.

37. The radio station in claim 36, wherein the predictor is a digital filter.

38. The radio station in claim 36, wherein the predictor is configured to model the SIR detector, a radio channel, and the power control command generator.

39. The radio station in claim 36, wherein the other radio station determines its transmission power based on the received power control command.

40. A method for sending information over a radio channel in a mobile radio communications system, comprising:

transmitting power control commands from a first radio station to a second radio station;

receiving a signal transmitted by the second radio station;

detecting a signal-to-interference (SIR) associated with the received signal;

predicting an SIR of a future received signal including a power control model for modeling parameters that influence a power control process and for generating a predicted SIR;

delaying the predicted SIR and providing a delayed predicted SIR;

determining a difference between the predicted SIR and the delayed SIR;

summing the difference with the predicted SIR to produce an SIR compensation factor;

summing the SIR compensation factor with the detected SIR to produce a compensated SIR; and

generating a power control command using the compensated SIR.

41. The method in claim 40, wherein the predicting includes modeling the SIR detector, a radio channel, and the power control command generator.

42. The method in claim 40, wherein the second radio station determines its transmission power based on the received power control command.