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

• US 7,327,697 B1
• Filed: 06/25/2002
• Issued: 02/05/2008
• Est. Priority Date: 06/25/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Airespace, Inc. (Cisco Systems, Inc.)
• Inventors: Dietrich, Paul F., Calhoun, Patrice R., Friday, Robert J., O'Hara, Robert B. Jr., Hills, Alexander H.
• Primary Examiner(s): Pezzlo; John
• Application Number:
  US10/183,704
• Time in Patent Office: 2,051 Days
• Field of Search: 370/278, 370/282, 370/252, 370/430, 370/328, 370/329, 370/338, 370/229, 370/230, 370/462, 370/337, 455/440, 455/452, 455/13.1, 455/423, 455/525, 713/201, 709/227, 709/228, 709/220, 709/221, 709/240
• US Class Current: 370/278
• 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 72/541 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.

Claims

1. In a wireless local area network system having a limited number of fixed physical channels, a plurality of access elements and at least one central control element, a method for dynamically assigning the physical channels comprising:

receiving physical layer information collected at said access elements, said physical layer information converted into reportable data about at least observed signal strength between access elements;

access element load, recognizable interference, and physical interference;

weighting said recognizable interference according to a first weight factor and weighting said physical interference according to a second weight factor;

constructing at least one decision matrix from said reportable data; and

assigning, from said central control element, said channels to said access elements based on optimizing a performance metric extracted from examination of said at least one decision matrix.

2. The method according to claim 1 further including constructing, from said physical interference, a physical interference matrix with additional virtualized channels representing noise power within each said physical channel.

3. The method according to claim 1 wherein said performance metric is further modified according to said access element load on said communication channels.

4. The method according to claim 1 wherein said constructing step includes the step of:

searching for optimal solutions for said decision matrix.

5. The method according to claim 4 wherein said constructing step includes:

prioritizing access elements according to information derived from said decision matrix to obtain priorities;

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

6. The method according to claim 1 further comprising causing the access elements to actively probe for neighboring access elements, and measure the received signal strength of RF signals transmitted by the neighboring access elements.

7. In a wireless local area network system having a limited number of fixed physical channels, a plurality of access elements and at least one central control element, a system for dynamically assigning said physical channels comprising:

a first resource management module associated with each access element for collecting physical layer information and converting said physical information into reportable data about at least observed signal strength between access elements; and

a second resource management module assocaited 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 into at least one decision matrix for each of said access elements;

said second resource management module being operative to assign said physical channels to said access elements based on said decision matrices;

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

8. The system according to claim 7 wherein said reportable data further includes at least one of 1) access element load, 2) recognizable interference, and 3) physical interference.

9. The system according to claim 7 further including frontend 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.

10. The system according to claim 9 wherein said wideband sensor includes a wideband filter and said narrowband sensor includes a narrowband filter.

11. The system according to claim 7 wherein, in said packetized communication path, every data packet has a header with physical layer information appended to said packet.

12. In a wireless local area network system having a limited number of fixed physical channels, a plurality of access elements and at least one central control element, a method for dynamically assigning the physical channels comprising:

receiving physical layer information collected at said access elements, said physical layer information converted into reportable data about observed signal strength between access elements, access element load, recognizable interference, and physical interference;

weighting said recognizable interference according to a first weight factor and weighting said physical interference according to a second weight factor;

constructing at least one decision matrix from said reportable data; and

assigning said channels to said access elements based on optimizing a performance metric extracted from examination of said at least one decision matrix.

13. The method according to claim 12 further including constructing, from said physical interference, a physical interference matrix with additional visualized channels representing noise power within each said physical channel.

14. The method according to claim 12 wherein said performance metric is further modified according to said access element load on said communication channels.

15. The method according to claim 12 wherein said constructing step includes the step of:

searching for optimal solutions for said decision matrix.

16. The method according to claim 15 wherein said constructing step includes:

prioritizing access elements according to information derived from said decision matrix to obtain priorities;

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

17. The method according to claim 12 further comprising causing the access elements to actively probe for neighboring access elements, and measure the received signal strength of RF signals transmitted by the neighboring access elements.