Method and system for dynamically assigning channels across multiple radios in a wireless LAN

• US 8,488,524 B2
• Filed: 08/13/2009
• Issued: 07/16/2013
• Est. Priority Date: 06/25/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Friday, Robert J., Calhous, Patrice R., O'Hara, Robert B. Jr., Hills, Alexander H., Dietrich, Paul F.
• Primary Examiner(s): Ghebretinsae, Temesgh
• Assistant Examiner(s): Chan, Richard
• Application Number:
  US12/540,904
• Publication Number:
  US 20090296647A1
• Time in Patent Office: 1,433 Days
• Field of Search: 455/440, 455/452.1, 455/13.1, 455/423, 370/278, 370/252, 370/328, 370/338, 370/230
• US Class Current: 370/328
• CPC Class Codes: H04B 17/24 with feedback of measurements to the transmitter
• CPC Class Codes: H04B 17/309 Measuring or estimating channel quality parameters
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/382 for resource allocation, admission control or handover
• CPC Class Codes: H04W 72/52 based on load
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

In a fixed channel wireless network system with a limited number of channels, assignment of the fixed channels between remote client elements and access elements is made systematically according to a set of criteria accounting for network loading and interference, then channel assignments are dynamically updated according to a priority to maintain optimal network performance with changing conditions of load and interference. The channel utilization problem is address at a system level rather than at a local level by treating the system as a three dimensional color mapping problem. All noise is treated as having a source in virtual access elements with an appropriate performance metric. The performance metric is used to select a channel set that minimize chances of interference and maximize user performance. Specifically, there are several parameter matrices which are managed and updated by a central resource management element, namely signal strength between elements, interference, and load. These matrices are used to find the optimal channel assignments for a predetermined limited set of assignable channels. In one implementation, the channel assignment methodology takes into account the interference associated with access elements operating on a selected channel, as well as the interference or energy that spills over (or is otherwise observable) on physical channels adjacent to the selected channel.

Claims

1. A method, comprising:

monitoring, at one or more wireless network access elements, signal strength of signals transmitted by respective neighboring wireless network access elements;

collecting information from said wireless network access elements and converting said information into reportable data about signal strength observed during the monitoring the signal strength of signals by the one or more wireless network access elements and about access element load, wherein the reportable data about access element load includes data regarding wireless network traffic load corresponding to each of said wireless network access elements over a period of time; and

identifying a combination of channel assignments for the one or more wireless network access elements from a plurality of possible combinations of channel assignments and assigning radio frequency (RF) channels for concurrent, respective use by said wireless network access elements based on the identified combination of channel assignments, wherein the identified combination of channel assignments is selected based on assessment of a performance metric function that includes as factors the signal strength observed by the one or more wireless network access elements, the access element load, and, for each combination of channel assignments, interference associated with concurrent signal transmissions of the wireless network access elements based on such combination of channel assignments for the wireless network access elements and at least one of the RF channels adjacent to the RF channels assigned in the possible combination of channel assignments.

2. The method of claim 1 wherein said reportable data further includes at least one of recognizable interference and physical interference.

3. The method of claim 2 further comprising constructing, from said physical interference, a physical interference matrix that represents noise power within each said physical channel.

4. The method of claim 2 further comprising constructing, from said recognizable interference, a recognizable interference matrix.

5. The method of claim 3 wherein said performance metric is calculated, in part, using said physical interference matrix.

6. The method of claim 4 wherein said performance metric is calculated, in part, using said recognizable interference matrix.

7. The method of claim 3 wherein said constructing step includes:

prioritizing wireless network access elements according to information derived from said interference matrix to obtain priorities;

assigning channels according to said information derived from said first interference matrix to access elements according to said priorities from highest to least until all access elements have channels assigned thereto.

8. The method of claim 3 wherein the constructing step comprises creating a signal strength matrix describing the signal strength observed between each of the access elements;

creating a utilization matrix describing the load observed at each access element over a given time interval;

combining the signal strength matrix and the utilization matrix to create an average signal strength matrix describing the average signal strength observed between each of the access elements; and

creating a first interference matrix by matrix-multiplying the average signal strength matrix by a channel assignment matrix describing a possible assignment of the physical channels across the access elements.

9. The method of claim 8 wherein the constructing step further comprises

deriving an adjacent channel matrix from the channel assignment matrix, the adjacent channel interference matrix describing the interference associated with channels adjacent to the assigned physical channels in the channel assignment matrix;

matrix-multiplying the average signal strength matrix by the adjacent channel interference matrix to create a second interference matrix; and

combining the first and second interference matrixes.

10. The method of claim 9 further comprising weighting the second interference matrix by a pre-determined scaling factor before the combining step.

11. The method of claim 1 further comprising causing one or more wireless network access elements to probe for neighboring wireless network access elements and to observe and detect signal strength of signals transmitted by the neighboring wireless network access elements by transmitting a probe request, receiving one or more probe responses to the probe request, and detecting strength of the signals carrying the one or more probe responses.

12. A system for dynamically assigning said physical channels to a set of wireless network access elements, comprising:

a first resource management module associated with each access element for collecting physical layer information from said wireless network access elements and converting said physical layer information into reportable data about signal strength observed during the monitoring the signal strength of signals by the one or more wireless network access elements and about access element load, wherein the reportable data about access element load includes data regarding wireless network traffic load corresponding to each of said wireless network access elements over a period of time; and

a second resource management module associated with said central control element, said second resource management module in communication via a packetized communication path with said first resource management module, for processing said reportable data to identify a combination of channel assignments for the one or more wireless network access elements from a plurality of possible combinations of channel assignments and assign radio frequency (RF) channels for concurrent, respective use by said wireless network access elements based on the identified combination of channel assignments;

said second resource management module being operative to cause one or more access elements to monitor signal strength of signals transmitted by respective neighboring wireless network access elements; and

select the identified combination of channel assignments based on assessment of a performance metric function that includes as factors the signal strength observed by the one or more wireless network access elements, the access element load, and, for each combination of channel assignments, interference associated with concurrent signal transmissions of the wireless network access elements based on such combination of channel assignments for the wireless network access elements and at least one of the RF channels adjacent to the RF channels assigned in the possible combination of channel assignments.

13. The system of claim 12 wherein said reportable data further includes at least one of recognizable interference and physical interference.

14. The system of claim 12 further including front-end signal reception means for detecting presence of potential physical interference comprising narrowband sensors and further including a selector for selecting between a wideband sensor and a narrowband sensor.

15. The system of claim 14 wherein said wideband sensor includes a wideband filter and said narrowband sensor includes a narrowband filter.

16. The system of claim 12 wherein said central control element further includes high speed dataflow counters for quick update of interference and load data.

17. The system of claim 12 wherein, in said packetized communication path, every data packet has a header with physical layer information appended to said packet.

18. The system of claim 12 wherein the second resource management module is operative to cause one or more access elements to transmit a probe request, receive one or more probe responses to the probe request, and detect strength of the signals carrying the one or more probe responses.

19. An apparatus, comprising:

means for monitoring, at one or more wireless network access elements, signal strength of signals transmitted by respective neighboring wireless network access elements;

means for collecting physical layer information from said wireless network access elements and converting said physical layer information into reportable data about signal strength observed during the monitoring the signal strength of signals by the one or more wireless network access elements and about access element load, wherein the reportable data about access element load includes data regarding wireless network traffic load corresponding to each of said wireless network access elements over a period of time; and

means for identifying a combination of channel assignments for the one or more wireless network access elements from a plurality of possible combinations of channel assignments and assigning radio frequency (RF) channels for concurrent, respective use by said wireless network access elements based on the identified combination of channel assignments, wherein the identified combination of channel assignments is selected based on assessment of a performance metric function that includes as factors the signal strength observed by the one or more wireless network access elements, the access element load, and, for each combination of channel assignments, interference associated with concurrent signal transmissions of the wireless network access elements based on such combination of channel assignments for the wireless network access elements and at least one of the RF channels adjacent to the RF channels assigned in the possible combination of channel assignments.