Method for allocating downlink electromagnetic power in wireless networks

• US 6,587,690 B1
• Filed: 02/12/1999
• Issued: 07/01/2003
• Est. Priority Date: 02/12/1999
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Di Huo, David, Pittampalli, Eshwar
• Primary Examiner(s): NGUYEN, DUC M
• Application Number:
  US09/249,313
• Time in Patent Office: 1,600 Days
• Field of Search: 455/446, 455/69, 455/522, 455/436, 455/67.1, 455/423, 455/422, 455/447, 455/424, 455/561, 370/244, 370/254, 370/318, 370/320, 370/329, 370/342, 370/335
• US Class Current: 455/446
• CPC Class Codes: H04W 52/143 Downlink power control
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment

Abstract

A method for allocating downlink power in a wireless network determines downlink transmit powers to permit a target performance goal to be satisfied for defined radio frequency coverage areas. Base stations transmit electromagnetic transmissions. Received signal parameters of the electromagnetic transmissions are measured at measurement locations within defined radio frequency coverage areas. A data processing system determines propagation factors associated with the electromagnetic transmissions as a function of the measurement locations. The data processing system determines a downlink transmit power for at least one of the base stations based upon at least one target performance goal for the coverage areas and the propagation factors.

Claims

1. A method for allocating downlink power in a wireless network comprising the steps of:

measuring received signal parameters, of electromagnetic transmissions from base stations, at measurement locations within defined radio frequency coverage areas, the measurement locations being geographical points where mobile stations may obtain wireless service from the wireless network;

determining propagation factors associated with the electromagnetic transmissions as a function of the measurement locations; and

determining a downlink transmit power for at least one of the base stations based upon the propagation factors and a target performance goal for the coverage areas.

2. The method according to claim 1 further comprising the step of:

calibrating the downlink transmit power to satisfy the target performance goal for the measurement locations with a defined reliability.

3. The method according to claim 2 wherein the calibrating step includes calibrating the initial downlink transmit power by considering a known maximum transmit power of each of the base stations.

4. The method according to claim 1 further comprising the step of:

calibrating the downlink transmit power to satisfy a target carrier-to-interference ratio as the target performance goal for the measurement locations with a defined reliability.

5. The method according to claim 4 wherein the calibrating step comprises establishing the defined reliability as a percentage of time in a coverage area during which the target-to-carrier interference ratio is met or exceeded.

6. The method according to claim 1 further comprising the step of:

calibrating the downlink transmit power to obtain a corresponding actual carrier-to-interference ratio meeting or minimally exceeding a target carrier-to-interference ratio as the target performance goal for the measurement locations with a defined reliability.

7. The method according to claim 1 wherein the measuring step further comprises measuring background noise associated with each of the measurement locations, the background noise being within a frequency range of the electromagnetic transmissions, and wherein the calculating step further comprises calculating the downlink transmit power for each of the base stations based upon the propagation factors, background noise and signal strengths as the measured signal parameters, and a target carrier-to-interference ratio as the target performance goal.

8. The method according to claim 1 wherein the determining of the propagation factors further comprises determining a propagation factor matrix including respective propagation factors for at least one propagational path between each measurement location and a corresponding base station.

9. The method according to claim 1 wherein the determining of the propagation factors further comprises determining a propagation factor matrix having columns representing uniform base station identifiers and rows representing uniform measurement locations.

10. The method according to claim 1 wherein the determining of the propagation factors is accomplished in accordance with the following equation:

$E_i<br><br>\left(x\right)=\frac{V_i<br><br>\left(x\right)-N<br><br>\left(x\right)}{y_i}$

wherein y_i is a known downlink power of base station i, V_i(x) is a received signal parameter as a function of measurement location x, and N(x) is a background noise power as a function of measurement location x.

11. The method according to claim 1 wherein the determining of the downlink transmit power includes the following steps:

constructing a vector z={z_i}ⁿ_i=1 and a matrix A={a_ij}ⁿ_i,j=1 in accordance with the following equations;

$z_i=C_i<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{\underset{k=1}{\stackrel{m}{\sum <br><br>}}<br><br>N<br><br>\left(x_k\right)<br><br>E_i<br><br>\left(x_k\right)}{\underset{k=1}{\stackrel{m}{\sum <br><br>}}<br><br>E_i^2<br><br>\left(x_k\right)}$$a_{\mathrm{ij}}=C_i<br><br>\frac{\underset{k=1}{\stackrel{m}{\sum <br><br>}}<br><br>E_i<br><br>\left(x_k\right)<br><br>E_j<br><br>\left(x_k\right)}{\underset{k=1}{\stackrel{m}{\sum <br><br>}}<br><br>E_i^2<br><br>\left(x_k\right)}$

 

wherein C_i represents a carrier-to-interference ratio for a defined coverage area i, E_i(x) is a propagation factor for first set of defined coverage areas i, E_j(x) is a propagation factor for a second set of defined coverage areas distinct from the first set, N(x_k) represents background noise, m is, the considered number of measurement locations x, k represents a particular measurement location, and n is the total number of the defined coverage areas within the first set and the second set

applying an iteration w⁽ⁿ⁾=w⁽⁰⁾+A*w<sup>(n−

1)</sup> to the foregoing equations starting with w⁽⁰⁾=z to solve for the vector w={w₁,w₂,w₃ . . . w_n}.

12. The method according to claim 1 wherein determining of the downlink transmit power is accomplished by using a local approximation in accordance with the following inter-related equations:

$y_i\approx <br><br>C_i·<br><br>\frac{N^{M,i}+\underset{j\ne <br><br>i}{\sum <br><br>}<br><br>E_j^{M,i}}{E_i^{m,i}}$$E_j^{M,k}=\underset{x\in <br><br>S_k}{\max }<br><br>E_j<br><br>\left(x\right)$$E_j^{m,k}=\underset{x\in <br><br>S_k}{\min }<br><br>E_i<br><br>\left(x\right)$$N^{M,i}=\underset{x\in <br><br>S_i}{\max }<br><br>N<br><br>\left(x\right)$

wherein y_i is a known downlink power of base station i, C_i represents a carrier-to-interference ratio for a defined coverage area, E_i(x) is a propagation factor for first set of defined coverage areas i, E_j(x) is a propagation factor for a second set of defined coverage areas distinct from the first set, N(x) represents background noise, m is the considered number of measurement locations x, k represents a particular measurement location, and S_i refers to the defined measurement locations x within the coverage area i.

13. The method according to claim 1 further comprising the step of:

adjusting downlink transmit-power settings of corresponding base stations to conform with a system-wide constellation of the downlink transmit powers selected to meet or minimally exceed the target performance goal.

14. A method for allocating downlink power in a wireless network comprising the steps of:

measuring received signal strengths, of electromagnetic transmissions from base stations, at measurement locations within geographic coverage areas, the measurement locations being geographical points where mobile stations may obtain wireless service from the wireless network;

determining propagation factors of the electromagnetic transmissions for at least one propagational path between each of said measurement locations and a corresponding base station;

calculating an initial downlink transmit power within a transmitter power interval for each of the base stations based upon the propagation factors and target carrier-to-interference ratios for the measurement locations; and

calibrating the initial downlink transmit power to obtain a resultant downlink transmit power satisfying the target carrier-to-interference ratios for the measurement locations with at least a minimum probability.

15. The method according to claim 14 further comprising the step of:

selecting the target carrier-to-interference ratios as generally uniform throughout a majority of the geographic coverage areas in the wireless network.

16. The method according to claim 14 further comprising the step of:

selecting the target carrier-to-interference ratios as different for different ones of the geographic coverage areas, wherein the geographic coverage areas comprise one or more sectors of a cell with different estimated traffic loadings.

17. The method according to claim 14 further comprising the step of:

adjusting downlink transmit powers of the base stations to conform to resultant downlink transmit powers selected to satisfy the target carrier-to-interference ratios for the corresponding measurement locations.

18. The method according to claim 14 wherein the resultant downlink transmit power comprises a resultant downlink transmit power meeting or minimally exceeding the target carrier-to-interference ratios for the corresponding measurement locations.

19. The method according to claim 14 further comprising the step of:

adjusting a downlink transmit power of a beacon channel of a first one of the base stations to conform to the resultant downlink transmit power.

20. The method according to claim 19 further comprising the step of:

adjusting a downlink transmit power of traffic channels of at least the first one based on a power control algorithm using the beacon channel as a reference signal power for a maximum permitted downlink transmit power of the traffic channels.

21. The method according to claim 14 wherein the calibrating step calculates a calibration factor by executing the following equation:

$\mathrm{\alpha <br><br>}=\underset{i=1}{\stackrel{n}{\min }}<br><br>\left\{\frac{y_i^M}{w_i},\underset{i=1}{\stackrel{n}{\max }}<br><br>\underset{x\in <br><br>S_i}{\max }<br><br>\frac{C_i·<br><br>N<br><br>\left(x\right)}{w_i<br><br>E_i<br><br>\left(x\right)-C_i<br><br>\underset{j=1}{\overset{n}{\sum <br><br>}}<br><br>w_j<br><br>E_j<br><br>\left(x\right)}\right\}$

wherein y_i is a known maximum downlink power of base station i, C_i represents a carrier-to-interference ratio for a defined coverage area, E_i(x) is a propagation factor for first set of defined coverage areas i, E_j(x) is a propagation factor for a second set of defined coverage areas distinct from the first set, N(x) represents background noise, x represents a measurement location, n represents a total number of the first set or the second set, w_i represents an initial downlink power for base station i within a power interval, and w_j represents a initial downlink power for base station j within a power interval.

22. The method according to claim 14 wherein the calibrating step establishes each resultant downlink power as a function of a calibration factor and a function of the target carrier-to-interference ratio as applied to the propagation factors.

23. The method according to claim 14 wherein the calibrating step establishes each resultant downlink power in accordance with the following equations:

$w_i=\frac{C_i}{\underset{x\in <br><br>S_i}{\min }<br><br>C_i<br><br>\left(x,1\right)}$$y_i=\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>w_i<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>i=1,2,\mathrm{\dots <br><br>n}.$

wherein C_i represents a carrier-to-interference ratio for a defined coverage area i, x represents a measurement location, w_i represents an initial downlink power for base station i within a power interval, S_i refers to defined measurement locations x within the coverage area i, α

is an attenuation factor, and y_i is a resultant downlink transmit power for base station i.

24. A system for allocating downlink power in a wireless network including base stations, the system comprising:

a test receiver for measuring received signal strengths, of electromagnetic transmissions from the base stations, at measurement locations within defined radio frequency coverage areas, the measurement locations being geographical points where mobile stations may obtain wireless service from the wireless network; and

a processing system including a determiner for determining propagation factors and a calculator for calculating initial downlink transmit powers for the base stations, the propagation factors being associated with the electromagnetic transmissions as a function of the measurement locations, the initial downlink transmit powers being within corresponding transmitter power intervals based upon the propagation factors and at least one target performance goal for the coverage areas.

25. The system according to claim 24 wherein the processing system further comprises:

a calibrator for calibrating the initial downlink transmit powers to obtain resultant downlink transmit powers satisfying a target carrier-to-interference ratio as the target performance goal for the measurement locations with a defined reliability.

26. The system according to claim 24 wherein the processing system further comprises:

a calibrator for calibrating the initial downlink transmit powers to obtain resultant downlink transmit powers with corresponding actual carrier-to-interference ratios meeting or minimally exceeding a target carrier-to-interference ratio as the target performance goal for the measurement locations with a defined reliability.

27. The system according to claim 24 wherein the processing system includes a calibrator for calibrating the initial downlink transmit powers by considering a known maximum transmit power of each of the base stations.

28. The system according to claim 24 wherein the processing system is adapted to establish the defined reliability as a percentage of time in a coverage area during which the target-to-carrier interference ratio is met or exceeded.

29. The system according to claim 24 wherein the test receiver is adapted to measure background noise associated with each of the measurement locations, the background noise being within a frequency range of the electromagnetic transmissions, and wherein the calculator is arranged to calculate the initial downlink transmit power for each of the base stations based upon the measured signal strengths, the measured background noise, the propagation factors, and a target carrier-to-interference ratio as the target performance goal.

30. The system according to claim 24 wherein the determiner is arranged to determine a propagation factor matrix including respective propagation factors for at least one propagational path between each measurement location and a corresponding base station.

31. The system according to claim 24 wherein the determiner is arranged to determine a propagation factor matrix having columns representing uniform base station identifiers and rows representing uniform measurement locations.