Methods for implementing a dynamic frequency selection (DFS) and a temporary channel selection feature for WLAN devices

• US 20040156336A1
• Filed: 12/08/2003
• Published: 08/12/2004
• Est. Priority Date: 01/30/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Atheros Communications Incorporated (Qualcomm, Inc.)
• Inventors: McFarland, William J., Green, Michael R.
• Granted Patent: US 6,870,815 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: G01S 7/021 Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals
• CPC Class Codes: H04L 1/22 using redundant apparatus to increase reliability
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26
• CPC Class Codes: H04L 63/08 for authentication of entities cryptographic mechanisms or cryptographic arrangements for entity authentication H04L9/32
• CPC Class Codes: H04L 63/162 at the data link layer
• CPC Class Codes: H04W 12/06 Authentication
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 24/04 Arrangements for maintaining operational condition
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Various regulatory domains promulgate standards to define how wireless devices should operate in certain frequency bands. The 5 GHz spectrum is of particular importance to certain regulatory domains because of radar systems also operating in this spectrum. To avoid interference with such radar systems, wireless devices operating in this spectrum should be able to detect radar and quickly vacate any channels currently used by the radar systems. In a channel switching technique, if the new channel is radar-exempt, then normal operation commences on the new channel. If the new channel is non-radar-exempt, then normal operation commences on a temporary radar-exempt channel and an aggregate background scan can be performed on the new channel. If no radars are detected using the aggregate background scan, then operation is switched from the temporary radar-exempt channel to the new channel. This channel switching technique minimizes disruption to users during a radar event.

Claims

1. A method of performing a channel switch operation for an access point in a regulatory domain, the regulatory domain having a frequency spreading requirement, the access point being allowed to communicate using allowed channels in a spectrum, the method comprising:

setting a new channel based on radar detection in a particular sub-band, the new channel being selected from a previously-scanned channel list;

determining whether the new channel is exempt from radar scan in the regulatory domain;

if the new channel is exempt, then recommencing normal operation using the new channel;

if the new channel is not exempt, then

selecting a temporary channel, wherein the temporary channel is exempt from radar scan, and recommencing normal operation using the temporary channel;

performing an aggregate background scan on the new channel; and

if the new channel passes the aggregate background scan, then recommencing normal operation using the new channel.

2. The method of claim 1, wherein if the new channel is not exempt and if the new channel fails the aggregate background scan, then setting another new channel from the previously-scanned channel list.

3. The method of claim 1, wherein setting another new channel includes marking a non-occupancy list.

4. The method of claim 1, wherein the previously-scanned channel list is built using a pseudo-random, weighted algorithm.

5. A method of switching channels for an access point operating in a 5 GHz spectrum, wherein the 5 GHz spectrum includes a first sub-band of 5150-5250 MHz, a second sub-band of 5250-5350 MHz, and a third sub-band of 5470-5725 MHz, the method comprising:

accessing a radar-free channel list;

setting a new channel selected from the radar-free channel list;

if the new channel is in the first sub-band, then beginning normal operation using the new channel without an additional radar scan; and

if the new channel is not in the first sub-band, then beginning normal operation using a temporary channel in the first sub-band, performing an aggregate background radar scan on the new channel, and switching from the temporary channel to the new channel if the aggregate background radar scan finds no radars.

6. The method of claim 5, wherein if the access point is initially operating in the second sub-band and at least one channel in the radar-free channel list is in the first sub-band, then setting the new channel to a lowest channel in the radar-free channel list.

7. The method of claim 5, wherein if the access point is initially operating in the second sub-band and no channel in the radar-free channel list is in the first sub-band, then setting the new channel to a highest channel in the radar-free channel list.

8. The method of claim 5, wherein if the access point is initially operating in the third sub-band, then setting the new channel to a lowest channel in the radar-free channel list.

9. A method of switching channels for an access point operating in a spectrum, wherein the spectrum includes a first radar-exempt sub-band and a second non-radar-exempt sub-band, the method comprising:

accessing a radar-free channel list;

setting a new channel selected from the radar-free channel list;

if the new channel is in the first radar-exempt sub-band, then beginning normal operation using the new channel without an additional radar scan; and

if the new channel is in the second non-radar-exempt sub-band, then beginning normal operation using a temporary channel in the first radar-exempt sub-band, performing an aggregate background radar scan on the new channel, and switching from the temporary channel to the new channel if the aggregate background radar scan finds no radars.

10. The method of claim 9, wherein if the access point is initially operating in the second non-radar-exempt sub-band and at least one channel in the radar-free channel list is in the first radar-exempt sub-band, then setting the new channel to a lowest channel in the radar-free channel list.

11. The method of claim 9, wherein if the access point is initially operating in the second non-radar-exempt sub-band and no channel in the radar-free channel list is in the first radar-exempt sub-band, then setting the new channel to one of a highest channel and a lowest channel in the radar-free channel list.