Downlink power control with limit to dynamic range using detection of downlink transmit power

• US 20050083999A1
• Filed: 07/29/2004
• Published: 04/21/2005
• Est. Priority Date: 07/30/2003
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Shin, Sung-Hyuk, Koo, Chang-Soo, Cuffaro, Angelo
• Granted Patent: US 7,616,677 B2
• Time in Patent Office: Days
• US Class Current: 375/148
• CPC Class Codes: H04W 52/12 Outer and inner loops
• CPC Class Codes: H04W 52/143 Downlink power control
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/362 Aspects of the step size
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range

Abstract

An apparatus and method is provided for dynamic range power control of a wireless downlink communication signal, such that target signal quality adjustments are held temporarily when it is apparent that transmit power control commands will not produce the desired response at the transmitting station. Comparisons of measured received signals to thresholds are performed to determine whether the transmitting station has either reached the maximum or minimum transmit power, in which case the target signal quality adjustment is controlled accordingly. When normal transmit power is detected, the target signal quality adjustments are allowed to resume as usual.

Claims

1. In a wireless receiver, a method for downlink transmit power detection of a base station that limits the power control dynamic range, where transmit power control adjustments occur in step size increments responsive to received signal quality measurements compared to an adjustable target signal quality, the method comprising the steps:

a) setting minimum and maximum thresholds for received signal quality measurements;

b) measuring a delta power change of received signal quality measurements for a downlink channel over a first interval;

c) estimating transmit power step size at the receiver;

d) calculating an aggregate power change based on said delta power change and the estimated transmit power step size;

e) comparing the aggregate power value to the minimum and maximum thresholds; and

f) sending a control signal for adjustment of transmit power control, where target signal quality adjustments are deactivated if the aggregate power value is within a predetermined proximity to either the maximum or minimum thresholds, and target signal quality adjustments are activated if the aggregate power value is not within said predetermined proximity to either the maximum or minimum thresholds; and

g) repeating steps (a) through (f) over successive intervals.

2. The method of claim 1 wherein the transmit power step sizes adjusted at the base station are predetermined as an actual set of k possible sizes, and step (c) further comprises:

calculating a temporary transmit power step size as the ratio of the aggregate power value and observation window size;

comparing the temporary transmit power step size to each of k possible step sizes and using the closest possible step size as the estimated transmit power step size.

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

calculating a temporary step size as the ratio of the aggregate power value and observation window size;

measuring the difference between estimated transmit power step size and the temporary step size; and

using the estimated transmit power step size if the measured difference is less than a predetermined value.

4. The method of claim 3 wherein the estimating in step (c) is calculated as the estimate of the transmit step size of the prior increment factored by a predetermined factor alpha plus the temporary step size factored by (1-alpha).

5. The method of claim 1 wherein the downlink channel comprises a dedicated physical channel (DPCH) and a common pilot channel (CPICH), the received signal quality measurements include a received signal code power (RSCP) of the DPCH and CPICH, and the adjustable signal target quality is a target signal to interference ratio (SIR).

6. The method of claim 5 wherein the measuring of step (b) includes determining a delta power change of the DPCH (Δ

DPCH_RSCP) and a delta power change of the CPICH (Δ

CPICH_RSCP), and the calculating of step (d) is based on (Δ

DPCH_RSCP-ACPICH_RSCP) plus or minus the transmit step size estimate of step (c).

7. The method of claim 1 wherein the downlink channel comprises a dedicated physical channel (DPCH) and a common pilot channel (CPICH), the received signal quality measurements include a signal to interference ratio (SIR) of the DPCH and of the CPICH, and the adjustable signal target quality is a target SIR.

8. The method of claim 7 wherein the measuring of step (b) includes determining a delta power change of the DPCH (Δ

DPCH_SIR) and a delta power change of the CPICH (Δ

CPICH_SIR), and the calculating of step (d) is based on (Δ

DPCH_SIR-Δ

CPICH_SIR) plus or minus the transmit step size estimate of step (c).

9. A wireless receiver that performs downlink transmit power detection of a base station, where transmit power control adjustments occur in step size increments responsive to received signal quality measurements compared to an adjustable target signal quality, the receiver comprising:

a RAKE receiver for detecting a received wireless signal and determining signal quality parameters;

a signal to interference (SIR) measurement device configured to determine SIR and signal quality values based on the signal quality parameters from the RAKE receiver;

an inner loop power control device for determining a transmit power control command for the base station to increase or decrease transmit power;

an outer loop power control device for calculating the adjustable target signal quality; and

a dynamic range limiting device configured to control the outer loop power control device based on whether the base station has reached the maximum or minimum transmit power or whether the base station did not properly decode the transmit power control command due to poor signal quality.

10. The wireless receiver of claim 9, wherein the dynamic range limiting device is further configured to set minimum and maximum thresholds for received signal quality measurements;

measure a delta power change of received signal quality measurements for a downlink channel over a first interval;

estimate transmit power step size;

calculate an aggregate power change based on said delta power change and the estimated transmit power step size;

compare the aggregate power value to the minimum and maximum thresholds; and

send a control signal for adjustment of transmit power control;

where target signal quality adjustments are deactivated if the aggregate power value is within a predetermined proximity to either the maximum or minimum thresholds, and target signal quality adjustments are activated if the aggregate power value is not within said predetermined proximity to either the maximum or minimum thresholds.

11. The receiver of claim 10 wherein the downlink channel comprises a dedicated physical channel (DPCH) and a common pilot channel (CPICH), the received signal quality measurements include a received signal code power (RSCP) of the DPCH and CPICH, and the adjustable signal target quality is a target signal to interference ratio (SIR).

12. The receiver of claim 11 wherein the measuring of a delta power change of received signal quality measurements includes determining a delta power change of the DPCH (Δ

DPCH_RSCP) and a delta power change of the CPICH (Δ

CPICH_RSCP), and the calculating of the aggregate power value is based on (Δ

DPCH_RSCP-Δ

CPICH_RSCP) plus or minus the transmit power step size estimate.

13. The receiver of claim 10 wherein the downlink channel comprises a dedicated physical channel (DPCH) and a common pilot channel (CPICH), the received signal quality measurements include a signal to interference ratio (SIR) of the DPCH and of the CPICH, and the adjustable signal target quality is a target SIR.

14. The receiver of claim 13 wherein the measuring of a delta power change of received signal quality measurements includes determining a delta power change of the DPCH (Δ

DPCH_SIR) and a delta power change of the CPICH (Δ

CPICH_SIR), and the calculating of the aggregate power value is based on (Δ

DPCH_RSCP-Δ

CPICH_RSCP) plus or minus the transmit power step size estimate.

15. A method of transmission power control of a transmitting wireless transmit receive unit (WTRU) that transmits data signals in first and second forward channels where the transmitting WTRU is configured to make first forward channel power adjustments as a function of target metrics computed at a receiving WTRU based on the data signals as received over the first forward channel, the method comprising:

receiving data signals from the transmitting WTRU on the first forward channel;

receiving data signals from the transmitting WTRU on the second forward channel;

computing a power differential between data signals received on the first forward channel and data signals received on the second forward channel;

computing target metrics for the transmitting WTRU'"'"'s first forward channel power adjustments based on the computed power differential; and

sending first forward channel transmission power adjustment signals to the transmitting WTRU on a reverse channel transmission based on the computed target metrics and contingent upon the computed power differential.

16. The method of claim 15 where the transmitting WTRU transmits data signals on dedicated and common channels wherein:

the receiving data signals on the first forward channel comprises receiving downlink data signals on a dedicated channel;

the receiving data signals on the second forward channel comprises receiving downlink data signals on a common channel; and

the transmitting first forward channel transmission power adjustment signals on a reverse channel comprises transmitting transmission power adjustment signals for the dedicated downlink channel on an uplink channel.

17. The method of claim 15 where the sending the first forward channel transmission power adjustment signals is contingent on the computed power differential is within a predetermined proximity to either a predetermined maximum or predetermined minimum threshold.

18. The method of claim 17 further comprising estimation of a transmit power control step size at the receiving WTRU and using the step size estimation when computing the power differential.

19. A receiving wireless transmit receive unit (WTRU) for implementing transmission power control for a transmitting WTRU that transmits data signals in first and second forward channels where the transmitting WTRU is configured to make first forward channel transmission power adjustments as a function of target metrics computed by the receiving WTRU, the receiving WTRU comprising:

a receiver configured to receive data signals from a transmitting WTRU on a first forward channel and data signals from the transmitting WTRU on a second forward channel;

a processor configured to compute target metrics for implementing first forward channel transmission power adjustments in the transmitting WTRU based on the detection of predetermined error conditions in the data signals received on the first forward channel;

said processor configured to compute a power differential between data signals received on the first forward channel and data signals received on the second forward channel; and

a transmitter operatively associated with said processor and configured to transmit first forward channel transmission power adjustment signals on a reverse channel responsive to target metric computations made by said processor and contingent upon a power differential computed by said processor.

20. The WTRU of claim 19 where the transmitting WTRU is a base station that transmits data signals on dedicated and common channels wherein:

the receiver is configured to receive downlink data signals on a dedicated channel as the first forward channel received signals and to receive downlink data signals on a common channel as the second forward channel received signals; and

the transmitter of the receiving WTRU is configured to transmit transmission power adjustment signals for the dedicated downlink channel on an uplink channel.