Pinning and Cascading Avoidance in Dynamic Channel Assignment for Wireless LANS

• US 20100238871A1
• Filed: 03/17/2009
• Published: 09/23/2010
• Est. Priority Date: 03/17/2009
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Shetty, Sandeep Jay, Tosic, Predrag, Chan, Douglas
• Granted Patent: US 8,289,901 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/16 Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Techniques are provided to determine channel assignments for wireless access point (AP) devices in a wireless local area network (WLAN). From each of a plurality of AP devices operating at least one of a plurality of channels in the WLAN, wireless activity data is received that represents activity in each channel associated with signals of devices operating in the WLAN and associated with signals and energy from devices that are not operating in the WLAN as detected by the AP devices by receiving radio frequency energy in each of the plurality of channels. During a channel plan evaluation session, the wireless activity data is evaluated for multiple ones of the plurality of access point devices to determine whether the channel on which an access point device operates should be changed such that a decision to change the channel for at least one access point is limited to a localized region of the wireless network and does not necessarily affect a channel change decision for access points outside of the localized region of the wireless network. The channel on which the at least one access point device operates is changed or assigned based on the evaluation. In one form, the wireless activity data is a single metric that is derived from multiple pieces of data, each representing a different component of wireless activity determined by an AP device to be occurring in a channel.

Claims

1. A method comprising:

at each of a plurality of wireless network access point devices operating on at least one of a plurality of channels in a wireless network, receiving radio frequency energy in each of the plurality of channels and generating at least one metric representing activity in each channel associated with signals of devices operating in the wireless network and associated with signals and energy from devices that are not operating in the wireless network;

during a channel plan evaluation session, evaluating the at least one metric for multiple ones of the plurality of access point devices to determine whether the channel on which an access point device operates should be changed such that a decision to change the channel for at least one access point is limited to a localized region of the wireless network and does not necessarily affect a channel change decision for access points outside of the localized region of the wireless network; and

changing the channel on which the at least one access point device operates based on said evaluating.

2. The method of claim 1, wherein evaluating comprises generating a list of candidate access point devices whose metric is to be evaluated during a channel plan evaluation session, selecting an access point device in the list, evaluating the metric for the selected access point device to determine whether a different channel from the one the selected access point device is currently operating on would provide better performance based on the metric for each channel, identifying neighbor access point devices in the localized region of the wireless network for the selected access point device based on a receive signal strength with respect to signals transmitted by the selected access point device, analyzing an impact of a channel change for the selected access point device to the neighbor access point devices in the localized region of the wireless network, removing from the candidate list the selected access point device and one or more neighbor access point devices in the localized region of the wireless network based on said analyzing, and repeating selecting, identifying, analyzing and removing with respect to a next selected access point in the list until the list is empty.

3. The method of claim 2, wherein identifying comprises identifying one-hop neighbor access point devices for which the receive signal strength exceeds a threshold and identifying two-hop neighbor access point devices for which the received signal strength from signals from a one-hop neighbor access point device exceeds a threshold.

4. The method of claim 3, wherein analyzing comprises evaluating the metric for each one-hop neighbor access point device on each of the plurality of channels based on a choice for a new channel for the selected access point device, generating a metric for the selected access point device for the new channel, comparing the metric for the new channel with the metric for a current channel for the selected access point device, determining whether a difference between the metric for the new channel and the metric for the current channel of the selected access point device satisfies a first criterion.

5. The method of claim 4, when it is determined that the metric for the new channel and the metric for the current channel of the selected access point device satisfies a first criterion, further comprising computing a cumulative metric from the metric for the selected access point device for the new channel and the metrics for the one-hop and two-hop neighbor access point devices.

6. The method of claim 5, and further comprising comparing the cumulative metric with a second criterion, and assigning a new channel plan to the selected access point and to its one-hop and two-hop neighbor access point devices depending on whether the difference satisfies the first criterion, depending on whether the cumulative metric satisfies the second criterion and depending on whether channel searching is performed during the first channel searching stage or the second channel searching stage.

7. The method of claim 6, wherein during the first channel searching stage, assigning is based on the difference satisfying the first criterion or the cumulative metric satisfying the second criterion and during the second channel searching stage, assigning is based on the difference satisfying the first criterion and the cumulative metric satisfying the second criterion.

8. The method of claim 7, wherein during the first channel searching stage, removing comprises removing only one-hop neighbor access point devices from the list, and during the second channel searching stage, removing comprises removing one-hop and two-hop neighbor access point devices from the list.

9. The method of claim 2, wherein selecting comprises selecting the next access point device comprises selecting an access point device in the list that has the worse metric among remaining access point devices in the list.

10. The method of claim 2, wherein selecting comprises the next access point device comprises randomly selecting an access point device from the list according to at least one of:

a uniform distribution and a distribution that assigns a greater probability to those access point devices in the list whose metric indicates worse performance.

11. The method of claim 2, wherein selecting the next access point device comprises alternating at successive selection iterations between randomly selecting an access point device in the list and selecting an access point device in the list that currently has the worst metric among remaining access point devices in the list.

12. A system comprising:

a plurality of wireless network access point devices each configured to operate on at least one of a plurality of channels in a wireless network, wherein each access point is configured to receive radio frequency energy in each of the plurality of channels and generate at least one metric representing activity in each channel associated with signals of devices operating in the wireless network and associated with signals and energy from devices that are not operating in the wireless network; and

a controller apparatus configured to communicate with the plurality of wireless network access point devices and to supply control signals that control which channel each wireless network access point device uses for operating in the wireless network, wherein the controller apparatus is configured to, during a channel plan evaluation session, evaluate the at least one metric for multiple ones of the plurality of access point devices to determine whether the channel on which an access point device operates should be changed such that a decision to change the channel for at least one access point is limited to a localized region of the wireless network and does not necessarily affect a channel change decision for access points outside of the localized region of the wireless network, and to change the channel on which the at least one access point device operates based on the evaluation of the metric for multiple ones of the plurality of access point devices.

13. The system of claim 12, wherein the controller apparatus is configured to evaluate by generating a list of candidate access point devices whose metric is to be evaluated during a channel plan evaluation session, selecting an access point device in the list, evaluating the metric for the selected access point device to determine whether a different channel from the one the selected access point device is currently operating on would provide better performance based on the metric for each channel, identifying neighbor access point devices in the localized region of the wireless network for the selected access point device based on a receive signal strength with respect to signals transmitted by the selected access point device, analyzing an impact of a channel change for the selected access point device to the neighbor access point devices in the localized region of the wireless network, removing from the candidate list the selected access point device and one or more neighbor access point devices in the localized region of the wireless network based on said analyzing, and repeating selecting, identifying, analyzing and removing with respect to a next selected access point in the list until the list is empty.

14. The system of claim 13, wherein the controller apparatus is configured to identify neighbor access point devices by identifying one-hop neighbor access point devices for which the receive signal strength exceeds a threshold and identifying two-hop neighbor access point devices for which the received signal strength from signals from a one-hop neighbor access point device exceeds a threshold.

15. The system of claim 13, wherein the controller apparatus is configured to select the next access point device by selecting an access point device in the list that has the worst metric among remaining access point devices in the list.

16. The system of claim 13, wherein the controller apparatus is configured to select the next access point device by randomly selecting an access point device from the list according to at least one of:

a uniform distribution and a distribution that assigns a greater probability to those access point devices in the list whose metric indicates worse performance.

17. The system of claim 13, wherein the controller apparatus is configured to select the next access point device by alternating at successive selection iterations between randomly selecting an access point device in the list and selecting an access point device in the list that currently has the worst metric among remaining access point devices in the list.

18. Logic encoded in one or more tangible media for execution and when executed operable to:

receive from each of a plurality of wireless access point devices operating at least one of a plurality of channels in a wireless network, wireless activity data representing activity in each channel associated with signals of devices operating in the wireless network and associated with signals and energy from devices that are not operating in the wireless network as detected by the wireless access point devices by receiving radio frequency energy in each of the plurality of channels;

during a channel plan evaluation session, evaluate the wireless activity data for multiple ones of the plurality of access point devices to determine whether the channel on which an access point device operates should be changed such that a decision to change the channel for at least one access point is limited to a localized region of the wireless network and does not necessarily affect a channel change decision for access points outside of the localized region of the wireless network; and

change the channel on which the at least one access point device operates based on the evaluation.

19. The logic of claim 18, wherein the logic that evaluates comprises logic configured to generate a list of candidate access point devices whose wireless activity data is to be evaluated during a channel plan evaluation session, selecting an access point device in the list, evaluate the wireless activity data for the selected access point device to determine whether a different channel from the one the selected access point device is currently operating on would provide better performance based on the wireless activity data for each channel, identify neighbor access point devices in the localized region of the wireless network for the selected access point device based on a receive signal strength with respect to signals transmitted by the selected access point device, analyze an impact of a channel change for the selected access point device to the neighbor access point devices in the localized region of the wireless network, remove from the candidate list the selected access point device and one or more neighbor access point devices in the localized region of the wireless network based on the analysis, and repeat selecting, identifying, analyzing and removing with respect to a next selected access point in the list until the list is empty.

20. The logic of claim 19, wherein the logic that selects the next access point device is configured to randomly select an access point device from the list according to at least one of:

a uniform distribution and a distribution that assigns a greater probability to those access point devices in the list whose metric indicates worse performance.

21. The logic of claim 19, wherein the logic that selects the next access point device is configured to alternate at successive selection iterations between randomly selecting an access point device in the list and selecting an access point device in the list that currently has the worst metric among the still remaining access point devices in the list.