Transmit power control maximizing coverage at a minimum interference

• US 8,599,744 B2
• Filed: 07/27/2011
• Issued: 12/03/2013
• Est. Priority Date: 07/27/2011
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Lee, Ji Woong, Desai, Vishal Satyendra
• Primary Examiner(s): Ly, Anh-Vu
• Assistant Examiner(s): LOPEZ-VARGAS, GUSTAVO E
• Application Number:
  US13/191,778
• Publication Number:
  US 20130028158A1
• Time in Patent Office: 860 Days
• Field of Search: 370/311, 370/338, 370/252, 370/329, 370/310, 370/315, 370/318, 370/328, 455/446, 455/452.1, 455/522, 455/13.4, 455/103, 455/561, 455/574
• US Class Current: 370/318
• CPC Class Codes: H04W 52/0206 in access points, e.g. base stations access point devices per se H04W88/08
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Techniques are provided to generate a transmit power plan comprising transmit powers to be used by wireless access point devices in a wireless network. A wireless network controller receives, from each of a plurality of wireless access point devices configured to provide wireless service in corresponding coverage areas to client devices, data indicating receive signal strength information with respect to signals received from others of the plurality of wireless access point devices. Overlap of coverage areas of wireless access point devices is computed from the received signal strength information. A plurality of candidate transmit power plans are generated each from a deterministic or random sequence of selections of wireless access point devices. One of the plurality of candidate transmit power plans is selected to achieve a desired amount of coverage area overlap while maximizing overall coverage by the plurality of wireless access point devices.

Claims

1. A method comprising:

receiving, from each of a plurality of wireless access point devices configured to provide wireless service in corresponding coverage areas to client devices, data indicating receive signal strength information with respect to signals received from others of the plurality of wireless access point devices;

computing overlap of coverage areas of wireless access point devices from the received signal strength information;

generating a plurality of candidate transmit power plans each from a deterministic sequence of selections of wireless access point devices or from a random sequence of selections of wireless access point devices; and

after generating the plurality of candidate transmit power plans, selecting one of the plurality of candidate transmit power plans to achieve a desired amount of coverage area overlap while maximizing overall coverage by the plurality of wireless access point devices.

2. The method of claim 1, wherein selecting one of the plurality of candidate transmit power plans comprises computing a quality metric from each of the plurality of candidate transmit power plans, comparing the quality metrics for the plurality of candidate transmit power plans, and selecting the candidate transmit power plan with the best quality metric.

3. The method of claim 1, wherein computing the quality metric comprises computing a total coverage area from a sum of the coverage areas for the plurality of wireless access point devices, computing a sum of overlapping coverage areas among the plurality of wireless access point devices, and subtracting the sum of overlapping coverage areas from the total coverage area.

4. The method of claim 3, wherein computing the sum of overlapping coverage areas comprises weighting with a first value overlapping coverage area between wireless access point devices that operate on a common radio frequency channel and weighting with a second value overlapping coverage area between wireless access point devices that operate on different radio frequency channels, wherein the first value and the second value are distinct, non-zero values.

5. The method of claim 1, wherein generating the plurality of candidate transmit power plans further comprises assigning transmit powers to wireless access point devices that are determined to have overlapping coverage areas, wherein the assigned transmit powers are based on a distance computed between pairs of wireless access point devices with overlapping coverage areas.

6. The method of claim 5, wherein generating the plurality of candidate transmit power plans comprises:

storing data representing a first set consisting of the plurality of wireless access point devices;

selecting one of the wireless access point devices from the first set and moving it to a second set, which consists of wireless access point devices moved from the first set;

storing data representing a third set consisting of one or more wireless access point devices in the first set that receive a signal from one or more wireless access point devices in the second set;

forming a pair of wireless access point devices by selecting a first wireless access point device from the third set and selecting a second wireless access point device from the second set;

determining a transmit power for the first wireless access point device and the second wireless access point device in the pair;

updating the second set by moving the first wireless access point device to the second set;

repeating the selecting, storing, forming, determining and updating operations until the first set is empty;

assigning a maximum transmit power to any wireless access point device that is determined not to receive a signal from any other wireless access point device in the plurality of wireless access point devices; and

storing data representing a candidate transmit power plan comprising transmit powers determined for or assigned to respective ones of the plurality wireless access point devices.

7. The method of claim 6, wherein forming comprises randomly selecting the first wireless access point device from the third set and randomly selecting the second wireless access point device from the second set.

8. The method of claim 6, wherein forming comprises selecting the first wireless access point device from the third set and the second wireless access point device from the second set such that the pair is a most distant pair among pairs consisting of a wireless access point device in the second set and a closest wireless access point device in the third set.

9. The method of claim 6, wherein determining the transmit power for the first wireless access point device and the second wireless access point device in the pair is based on whether a transmit power for one of the first and second wireless access point has already been determined.

10. The method of claim 9, wherein when the transmit power for the second wireless access point device has already been determined, computing a transmit power for the first wireless access point device based on the transmit power for the second wireless access point device using a first computation.

11. The method of claim 9, wherein when the transmit power for the first and second wireless access point devices in the pair are both not already determined, computing a transmit power for each of the first and second wireless access point devices using a second computation.

20. The method of claim 10, wherein the first computation comprises solving the equation:

P_rx=P_tx+G_tx+G_rx−

10n log d+20 log λ

−

20 log 4π

−

X_F

where

12. An apparatus comprising:

a network interface unit configured to enable communications over a network, including communications with a plurality of wireless access point devices configured to provide wireless service in corresponding coverage areas to client devices; and

a processor configured to;

receive from each of a plurality of wireless access point devices data indicating receive signal strength information with respect to signals received from others of the plurality of wireless access point devices;

compute overlap of coverage areas of wireless access point devices from the received signal strength information;

generate a plurality of candidate transmit power plans each from a deterministic sequence of selections of wireless access point devices or a random sequence of selections of wireless access point devices; and

after generation of the plurality of candidate transmit power plans, select one of the plurality of candidate transmit power plans to achieve a desired amount of coverage area overlap while maximizing overall coverage by the plurality of wireless access point devices.

13. The apparatus of claim 12, wherein the processor is configured to select one of the plurality of candidate transmit power plans by computing a quality metric from each of the plurality of candidate transmit power plans, comparing the quality metrics for the plurality of candidate transmit power plans, and selecting the candidate transmit power plan with the best quality metric.

14. The apparatus of claim 12, wherein the processor is configured to generate the plurality of candidate transmit power plans by assigning transmit powers to wireless access point devices that are determined to have overlapping coverage areas, wherein the assigned transmit powers are based on a distance computed between pairs of wireless access point devices with overlapping coverage areas.

15. The apparatus of claim 14, wherein the processor is configured to generate the plurality of candidate transmit power plans by:

storing data representing a first set consisting of the plurality of wireless access point devices;

selecting one of the wireless access point devices from the first set and moving it to a second set of wireless access point devices moved from the first set;

storing data representing a third set consisting of one or more wireless access point devices in the first set that receive a signal from one or more wireless access point devices in the second set;

forming a pair of wireless access point devices by selecting a first wireless access point device from the third set and selecting a second wireless access point device from the second set;

determining a transmit power for the first wireless access point device and the second wireless access point device in the pair;

updating the second set by moving the first wireless access point device to the second set;

repeating the selecting, storing, forming, determining and updating operations until the first set is empty;

assigning a maximum transmit power to any wireless access point device that is determined not to receive a signal from any other wireless access point device in the plurality of wireless access point devices; and

storing data representing a candidate transmit power plan comprising transmit powers determined for or assigned to respective ones of the plurality wireless access point devices.

16. One or more non-transitory computer readable storage media encoded with software comprising computer executable instructions and when the software is executed operable to:

receive, from each of a plurality of wireless access point devices configured to provide wireless service in corresponding coverage areas to client devices, data indicating receive signal strength information with respect to signals received from others of the plurality of wireless access point devices;

compute overlap of coverage areas of wireless access point devices from the received signal strength information;

generate a plurality of candidate transmit power plans each from a deterministic sequence of selections of wireless access point devices or a random sequence of selections of wireless access point devices; and

after generation of the plurality of candidate transmit power plans, select one of the plurality of candidate transmit power plans to achieve a desired amount of coverage area overlap while maximizing overall coverage by the plurality of wireless access point devices.

17. The computer readable storage media of claim 16, wherein the instructions that are operable to select one of the plurality of candidate transmit power plans comprise instructions operable to compute a quality metric from each of the plurality of candidate transmit power plans, compare the quality metrics for the plurality of candidate transmit power plans, and select the candidate transmit power plan with the best quality metric.

18. The computer readable storage media of claim 16, wherein the instructions that are operable to generate the plurality of candidate transmit power plans comprise instructions operable to assign transmit powers to wireless access point devices that are determined to have overlapping coverage areas, wherein the assigned transmit powers are based on a distance computed between pairs of wireless access point devices with overlapping coverage areas.

19. The computer readable storage media of claim 18, wherein the instructions that are operable to generate the plurality of candidate transmit power plans comprise instructions operable to:

store data representing a first set consisting of the plurality of wireless access point devices;

select one of the wireless access point devices from the first set and moving it to a second set;

store data representing a third set consisting of one or more wireless access point devices in the first set that receive a signal from one or more wireless access point devices in the second set of wireless access point devices moved from the first set;

form a pair of wireless access point devices by selecting a first wireless access point device from the third set and selecting a second wireless access point device from the second set;

determine a transmit power for the first wireless access point device and the second wireless access point device in the pair;

update the second set by moving the first wireless access point device to the second set;

repeat the select, store, form, determine and update operations until the first set is empty;

assign a maximum transmit power to any wireless access point device that is determined to not to receive a signal from any other wireless access point device; and

store data representing a candidate transmit power plan comprising transmit powers determined for or assigned to respective ones of the plurality wireless access point devices.