Power Allocation in a Wireless System with Base Stations Having Antenna Arrays

• US 20120201283A1
• Filed: 02/04/2011
• Published: 08/09/2012
• Est. Priority Date: 02/04/2011
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Inventors: Ashikhmin, Alexei, Marzetta, Thomas
• Granted Patent: US 8,620,373 B2
• Time in Patent Office: Days
• US Class Current: 375/224
• 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 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/243 taking into account interferences

Abstract

Provided is a method and apparatus for allocating transmit power in a wireless network. The method includes determining powers at which a base station transmits downlink signals to each active user equipment associated with the base station such that each of the downlink signals is associated with a different active user and the base station is permitted to transmit downlink signals with different powers to the associated active user equipments. The method further includes transmitting the associated downlink signals, by the base station, to the active user equipments at the determined powers.

Claims

1. A method for allocating transmit power in a wireless network, the method comprising:

determining powers at which a base station transmits downlink signals to each active user equipment associated with the base station such that each of the downlink signals is associated with a different active user and the base station is permitted to transmit downlink signals with different powers to the associated active user equipments; and

transmitting the associated downlink signals, by the base station, to the active user equipments at the determined powers.

2. The method of claim 1, wherein the determined powers are based on a power associated with the associated active user equipments and a signal to interference ratio for user equipment associated with another base station.

3. The method of claim 2, wherein the signal to interference ratios are based on downlink signals transmitted by the another base station and on the transmitted associated downlink signals.

4. The method of claim 3, wherein the signal to interference ratio is reduced between the transmitted associated downlink signals and the downlink signals transmitted by the another base station sharing a same pilot sequence.

5. The method of claim 3, wherein the signal to interference ratio is based on fading coefficients associated with the transmitted associated downlink signals and fading coefficients associated with downlink signals transmitted by the another base station.

6. The method of claim 5, wherein

7. The method of claim 1, wherein the determining powers at which a base station transmits downlink signals step includes,

calculating a variable based on a maximum signal to interference ratio and a minimum signal to interference ratio, and

determining a minimum power solution of a linear power function subject to a constraint based on the variable.

8. The method of claim 7, wherein

s=(SIR_max−

SIR_min)/2 under the constraint of

9. The method of claim 1, further comprising:

dropping an active user equipment having a highest determined power if a number of active user equipments associated with the wireless network is greater than a percentage of users.

10. The method of claim 9, wherein the percentage of users is based on a number of active user equipments having a relatively low signal to interference ratio and a number of active user equipments having a relatively high signal to interference ratio.

11. A controller, comprising:

a processor configured to,

determine powers at which a base station transmits downlink signals to each active user equipment associated with the base station such that each of the downlink signals is associated with a different active user and the base station is permitted to transmit downlink signals with different powers to the associated active user equipments.

12. The controller of claim 11, wherein the processer determines the powers based on a power associated with the associated active user equipments and a signal to interference ratio for user equipment associated with another base station.

13. The controller of claim 12, wherein the signal to interference ratios are based on downlink signals transmitted by the another base station and on the transmitted associated downlink signals.

14. The controller of claim 13, wherein the signal to interference ratio is reduced between the transmitted associated downlink signals and the downlink signals transmitted by the another base station sharing a same pilot sequence.

15. The controller of claim 13, wherein the signal to interference ratio is based on fading coefficients associated with the transmitted associated downlink signals and fading coefficients associated with downlink signals transmitted by the another base station.

16. The controller of claim 15, wherein

17. The controller of claim 11, wherein the processor determines powers at which the base station transmits downlink signals by,

calculating a variable based on a maximum signal to interference ratio and a minimum signal to interference ratio, and

determining a minimum power solution of a linear power function subject to a constraint based on the variable.

18. The controller of claim 17, wherein

s=(SIR_max−

SIR_min)/2 under the constraint of

19. The controller of claim 11, wherein the processor drops an active user equipment having a highest determined power if a number of active user equipments associated with the wireless network is greater than a percentage of users.

20. The controller of claim 19, wherein the percentage of users is based on a number of active user equipments having a relatively low signal to interference ratio and a number of active user equipments having a relatively high signal to interference ratio.