Controlling forward link traffic channel power

• US 20030081573A1
• Filed: 10/08/2002
• Published: 05/01/2003
• Est. Priority Date: 10/25/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Doerfler, Steve J., Malladi, Durga P., Anderson, Jon J.
• Granted Patent: US 7,266,103 B2
• Time in Patent Office: Days
• US Class Current: 370/333
• CPC Class Codes: H04B 7/18543 for adaptation of transmission parameters, e.g. power control for detecting or preventing errors in the information received H04L1/00
• CPC Class Codes: H04W 52/143 Downlink power control
• CPC Class Codes: H04W 52/16 Deriving transmission power values from another channel
• CPC Class Codes: H04W 52/20 using error rate
• CPC Class Codes: H04W 52/283 Power depending on the position of the mobile
• CPC Class Codes: H04W 52/48 during retransmission after error or non-acknowledgment

Abstract

Forward link transmission power to a user terminal in a wireless communications system having a plurality of beams is controlled by determining a baseline power level, P_baseline, from a received active pilot channel signal-to-noise ratio (SNR); determining a power margin, P_margin, from an identified interference susceptibility; determining a power level correction, P_correction, based on an identified packet error rate (PER); and setting P_transmit based on P_baseline, P_margin, and P_correction. For example, P_transmit may be set to a power level that is substantially equal to the sum of P_baseline, P_margin, and P_correction. The determination of each of P_baseline, P_margin, and P_correction may be performed in independently running control loops or processes.

Claims

1. A method of controlling forward link traffic channel transmission power, P_transmit, to a user terminal in a wireless communications system having a plurality of beams, comprising the steps of:

(a) receiving from the user terminal an active pilot channel signal to noise ratio (SNR);

(b) determining a baseline power level, P_baseline, from the received active pilot channel SNR;

(c) identifying a user terminal interference susceptibility;

(d) determining a power margin, P_margin, from the identified interference susceptibility;

(e) identifying a packet error rate (PER) associated with the user terminal;

(f) determining a power level correction, P_correction, based on the PER; and

(g) setting P_transmit based on P_baseline, P_margin, and P_correction.

2. The method of claim 1, wherein step (b) comprises:

(1) calculating a power level offset, P_o, according to P_o=E_bt/N_t+10log(R/W)−

E_cp/N_t, wherein E_bt/N_t is a desired forward link traffic channel SNR in decibels (dB), R is a forward link traffic channel data rate, W is a spreading bandwidth, and E_cp/N_t is the received active pilot channel SNR in dB; and

(2) adding P_o to a pilot channel transmit power level.

3. The method of claim 1, wherein step (c) comprises:

(1) receiving from the user terminal a plurality of signal power measurements, wherein each of the signal power measurements corresponds to one of a plurality of beams; and

(2) calculating the differences between a first of the signal power measurements and each of the other signal power measurements.

4. The method of claim 3, wherein step (1) comprises receiving a pilot strength measurement message (PSMM).

5. The method of claim 3, wherein step (d) comprises:

(1) setting P_margin to a first power level when the smallest of the calculated differences is greater than a predetermined threshold; and

(2) setting P_margin to a second power level when the smallest of the calculated differences is less than or equal to the predetermined threshold;

wherein the first power level is less than the second power level.

6. The method of claim 3, wherein step (d) comprises setting P_margin as a function of the smallest of the calculated differences.

7. The method of claim 1, wherein step (c) comprises determining the location of the user terminal within one of the plurality of beams.

8. The method of claim 7, wherein step (d) comprises:

(1) setting P_margin to a first power level when the identified location is within a beam crossover region; and

(2) setting P_margin to a second power level when the identified location is within a beam central region;

wherein the first power level is greater than the second power level.

9. The method of claim 1, wherein step (e) comprises:

(1) determining the number of negative acknowledgement (NAK) messages received over a data collection interval;

(2) determining the number of packets transmitted to the user terminal over the data collection interval; and

(3) calculating the packet error rate from the determined number of NAK messages and the determined number of transmitted packets.

10. The method of claim 1, wherein step (e) comprises:

(1) determining from a cyclical redundancy check whether a packet contains bit errors.

(2) incrementing a packet error counter when it is determined a packet contains errors; and

(3) calculating the ratio of counted packet errors to received errors.

11. The method of claim 1, wherein step (g) comprises setting P_transmit to a power level that is substantially equal to the sum of P_baseline, P_margin, and P_correction.

12. The method of claim 1, wherein step (f) comprises:

(1) increasing P_correction when the identified PER is greater than a desired PER; and

(2) decreasing P_correction when the identified PER is less than the desired PER.

13. A system for controlling forward link traffic channel transmission power, P_transmit, to a user terminal in a wireless communications system having a plurality of beams, comprising:

a selector adapted to determine a baseline power level, P_baseline, from a received active pilot channel SNR, a power margin, P_margin, from an identified interference susceptibility, and a power level correction, P_correction, from an identified packet error rate (PER); and

a transceiver adapted to set the forward link transmission power, P_transmit, based on P_baseline, P_margin, and P_correction.

14. The system of claim 13, wherein, said transceiver is further adapted to set P_transmit to a power level that is substantially equal to the sum of P_baseline, P_margin, and P_correction.

15. A system for controlling forward link traffic channel transmission power, P_transmit, to a user terminal in a wireless communications system having a plurality of beams, comprising:

means for receiving from the user terminal an active pilot channel signal to noise ratio (SNR);

means for determining a baseline power level, P_baseline, from the received active pilot channel SNR;

means for identifying a user terminal interference susceptibility;

means for determining a power margin, P_margin, from the identified interference susceptibility;

means for identifying a packet error rate (PER) associated with the user terminal;

means for determining a power level correction, P_correction, based on the PER; and

means for setting P_transmit based on P_baseline, P_margin, and P_correction.

16. The system of claim 15, wherein said means for determining a baseline power level comprises:

means for calculating a power level offset, P_o, according to P_o=E_bt/N_t+10log(R/W)−

E_cp/N_t, wherein E_bt/N_t is a desired forward link traffic channel SNR in decibels (dB), R is a forward link traffic channel data rate, W is a spreading bandwidth, and E_cp/N_t is the received active pilot channel SNR in dB; and

means for adding P_o to a pilot channel transmit power level.

17. The system of claim 15, wherein said means for identifying a user terminal interference susceptibility comprises:

means for receiving from the user terminal a plurality of signal power measurements, wherein each of the signal power measurements corresponds to one of a plurality of beams; and

means for calculating the differences between a first of the signal power measurements and each of the other signal power measurements.

18. The system of claim 17, wherein said means for receiving from the user terminal a plurality of signal power measurements comprises means for receiving a pilot strength measurement message (PSMM).

19. The system of claim 17, wherein said means for determining P_margin comprises:

means for setting P_margin to a first power level when the smallest of the calculated differences is greater than a predetermined threshold; and

means for setting P_margin to a second power level when the smallest of the calculated differences is less than or equal to the predetermined threshold;

wherein the first power level is less than the second power level.

20. The system of claim 17, wherein said means for determining P_margin comprises means for setting P_margin as a function of the smallest of the calculated differences.

21. The system of claim 15, wherein said means for identifying a user terminal interference susceptibility comprises means for determining the location of the user terminal within one of the plurality of beams.

22. The system of claim 21, wherein said means for determining P_margin comprises:

means for setting P_margin to a first power level when the identified location is within a beam crossover region; and

means for setting P_margin to a second power level when the identified location is within a beam central region;

wherein the first power level is greater than the second power level.

23. The system of claim 15, wherein said means for identifying a PER comprises:

means for determining the number of negative acknowledgement (NAK) messages received over a data collection interval;

means for determining the number of packets transmitted to the user terminal over the data collection interval; and

means for calculating the packet error rate from the determined number of NAK messages and the determined number of transmitted packets.

24. The system of claim 15, wherein said means for setting P_transmit comprises means for setting the forward link traffic channel transmission power to a power level that is equal to the sum of P_baseline, P_margin, and P_correction.

25. The system of claim 15, wherein said means for determining P_correction comprises:

means for increasing P_correction when the identified PER is greater than a desired PER; and

means for decreasing P_correction when the identified PER is less than the desired PER.

26. The system of claim 15, wherein said means for identifying a packet error rate (PER) comprises:

(1) means for determining from a cyclical redundancy check whether a packet contains bit errors;

(2) means for incrementing a packet error counter when it is determined a packet contains errors; and

(3) means for calculating the ratio of counted packet errors to received errors.