Reliability determination and combining of power control commands received in a wireless communication system

• US 20040166884A1
• Filed: 06/10/2003
• Published: 08/26/2004
• Est. Priority Date: 02/26/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sendonaris, Andrew, Kasturi, Nitin, Amerga, Messay, Subrahmanya, Parvathanathan, Riddle, Christopher C., Hsu, Chih-Ping, Oh, Hyukjun
• Granted Patent: US 7,340,268 B2
• Time in Patent Office: Days
• US Class Current: 455/522
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff
• CPC Class Codes: H04W 52/56 Detection of errors of TPC bits
• CPC Class Codes: H04W 52/58 Format of the TPC bits

Abstract

The reliability of transmit power control (TPC) commands received from a transmitter is determined based on a TPC target value. The TPC target value is derived based on a TPC threshold and possibly a weight, depending on the receiver implementation. A received TPC command is considered reliable if its absolute value exceeds the TPC target value. Received TPC commands deemed as unreliable are discarded and not used for power control. Multiple TPC target values, used for detecting UP and DOWN commands, may be derived with multiple scaling factors. For a receiver in soft handover and receiving TPC commands from multiple transmitters, a different TPC target value may be derived for each transmitter. The received TPC commands for each transmitter are compared against that transmitter'"'"'s TPC target value. Received TPC commands deemed as unreliable are discarded and not combined.

Claims

1. A device in a wireless communication system, comprising:

a computation unit operative to provide a transmit power control (TPC) target value used for determining reliability of received TPC commands; and

a detection unit operative to compare the received TPC commands against the TPC target value and provide detected TPC commands based on results of the comparison.

2. The device of claim 1, wherein the detection unit is operative to provide a detected TPC command for each of the received TPC commands, and wherein the detected TPC command indicates that the received TPC command is unreliable when an absolute value of the received TPC command is less than the TPC target value.

3. The device of claim 1, wherein the TPC target value is determined based on a TPC threshold.

4. The device of claim 3, wherein the TPC threshold is a function of signal-to-interference ratio (SIR) for the received TPC commands.

5. The device of claim 3, wherein the TPC threshold is a function of energy-per-chip-to-total-incoming-signal ratio (E_c/I_o) for a pilot and signal-to-interference ratio (SIR) for the received TPC commands.

6. The device of claim 3, wherein the TPC threshold is a function of energy-per-chip-to-total-noise-and-interference ratio (E_c/N_t) for a transmission received along with the received TPC commands.

7. The device of claim 3, wherein the TPC threshold is selected based on a tradeoff between probability of false alarm and probability of missed detection.

8. The device of claim 3, wherein the TPC target value is further determined based on a weight.

9. The device of claim 8, wherein the weight is a weighted total-noise-and-interference-to-total-incoming-signal ratio (N_t/I_o) estimate for a transmitter of the received TPC commands.

10. The device of claim 9, wherein the computation unit is operative to determine a weighted N_t/I_o estimate for each of a plurality of signal instances for the transmitter and to sum a plurality of weighted N_t/I_o estimates for the plurality of signal instances to obtain the weight.

11. The device of claim 1, wherein the computation unit is operative to provide first and second TPC target values, wherein the first TPC target value is used to determine whether the received TPC commands are UP commands, and wherein the second TPC target value is used to determine whether the received TPC commands are DOWN commands.

12. The device of claim 11, wherein the first and second TPC target values are determined based on first and second scaling factors, respectively.

13. The device of claim 1, wherein the wireless communication system is a Code Division Multiple Access (CDMA) system.

14. An integrated circuit, comprising:

a computation unit operative to provide a transmit power control (TPC) target value used for determining reliability of received TPC commands; and

a detection unit operative to compare the received TPC commands against the TPC target value and provide detected TPC commands based on results of the comparison.

15. An apparatus in a wireless communication system, comprising:

means for determining a transmit power control (TPC) target value used for determining reliability of received TPC commands;

means for comparing the received TPC commands against the TPC target value; and

means for providing a detected TPC command for each of the received TPC commands based on a result of the comparison, wherein the detected TPC command indicates that the received TPC command is unreliable when an absolute value of the received TPC command is less than the TPC target value.

16. A method of determining reliability of transmit power control (TPC) commands received from a transmitter in a wireless communication system, comprising:

determining a TPC target value used for determining reliability of received TPC commands;

comparing the received TPC commands against the TPC target value; and

providing a detected TPC command for each of the received TPC commands based on a result of the comparison, wherein the detected TPC command indicates that the received TPC command is unreliable when an absolute value of the received TPC command is less than the TPC target value.

17. The method of claim 16, wherein the determining includes

obtaining a weighted total-noise-and-interference-to-total-incoming-signal ratio (N_t/I_o) estimate for the transmitter, and

obtaining the TPC target value based on the weighted N_t/I_o estimate and a TPC threshold.

18. The method of claim 17, wherein the weighted N_t/I_o estimate is computed for each of a plurality of signal instances for the transmitter, and wherein a plurality of weighted N_t/I_o estimates for the plurality of signal instances are summed and used to obtain the TPC target value.

19. A processor readable media including instructions operable in a wireless communication device to:

determine a transmit power control (TPC) target value used for determining reliability of received TPC commands;

compare the received TPC commands against the TPC target value; and

provide a detected TPC command for each of the received TPC commands based on a result of the comparison, the detected TPC command indicating that the received TPC command is unreliable when an absolute value of the received TPC command is less than the TPC target value.

20. A device in a wireless communication system, comprising:

a computation unit operative to provide a transmit power control (TPC) target value for each of a plurality of transmitters;

a detection unit operative to compare the received TPC commands for each of the plurality of transmitters against the TPC target value for the transmitter to provide detected TPC commands for the transmitter; and

a TPC combiner operative to combine detected TPC commands for the plurality of transmitters to provide TPC decisions.

21. The device of claim 20, wherein the detection unit is operative to provide a detected TPC command for each received TPC command, and wherein the detected TPC command indicates that the received TPC command is unreliable when an absolute value of the received TPC command is less than the TPC target value used for the received TPC command.

22. The device of claim 21, wherein the TPC combiner is operative to discard detected TPC commands for received TPC commands deemed as unreliable.

23. The device of claim 20, wherein the detection unit provides a plurality of detected TPC commands for the plurality of transmitters for each power control period, and wherein the TPC combiner is operative to provide a TPC decision to decrease transmit power if any one of the plurality of detected TPC commands for the power control period indicates a decrease in transmit power.

24. The device of claim 20, wherein the TPC target value for each of the plurality of transmitters is determined based on a TPC threshold and a weight for the transmitter.

25. The device of claim 24, wherein the weight for each of the plurality of transmitter is a weighted total-noise-and-interference-to-total-incoming signal ratio (N_t/I_o) estimate for the transmitter.

26. The device of claim 20, further comprising:

a symbol combiner operative to combine data symbol estimates for at least one signal instance for each transmitter to provide the received TPC commands for the transmitter.

27. The device of claim 20, wherein the TPC combiner is operative to discard detected TPC commands for any one of the plurality of transmitters when a second signal quality estimate for the transmitter is below a predetermined threshold.

28. The device of claim 27, wherein the second signal quality estimate is an energy-per-chip-to-total-noise-and-interference ratio (E_c/N_t) estimate for a physical channel used to send the received TPC commands.

29. The device of claim 27, wherein the second signal quality estimate is an energy-per-chip-to-total-noise-and-interference ratio (E_c/N_t) estimate for the received TPC commands.

30. The device of claim 20, wherein the wireless communication system is a Code Division Multiple Access (CDMA) system.

31. An integrated circuit in a wireless communication system, comprising:

a computation unit operative to provide a transmit power control (TPC) target value for each of a plurality of transmitters;

a detection unit operative to compare received TPC commands for each of the plurality of transmitters against the TPC target value for the transmitter to provide detected TPC commands for the transmitter; and

a TPC combiner operative to combine detected TPC commands for the plurality of transmitters to provide TPC decisions.

32. An apparatus in a wireless communication system, comprising:

means for determining a transmit power control (TPC) target value for each of a plurality of transmitters;

means for comparing received TPC commands for each of the plurality of transmitters against the TPC target value for the transmitter to provide detected TPC commands for the transmitter; and

means for combining detected TPC commands for the plurality of transmitters to provide TPC decisions.

33. A method of combining transmit power control (TPC) commands received in a wireless communication system, comprising:

determining a TPC target value for each of a plurality of transmitters;

comparing received TPC commands for each of the plurality of transmitters against the TPC target value for the transmitter to provide detected TPC commands for the transmitter; and

combining detected TPC commands for the plurality of transmitters to provide TPC decisions.