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

A method of populating a radar-free channel list for a wireless local area network (WLAN) device operable in a 5 GHz spectrum, the spectrum being divided into 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:

• populating an allowed channel list with channels allowed by a regulatory domain for that spectrum;
• populating a BSS-free channel list with the allowed channels having acceptable levels of current WLAN transmission thereon;
• if the allowed channel list includes channels from the first, second, and third sub-bands, then determining whether the BSS-free channel list has less than two channels,
• if so, then choosing three channels from the allowed channel list, wherein a first channel is chosen from the first sub-band, a second channel is chosen from the second sub-band, and a third channel is chosen from the third sub-band,
• if not, then choosing three channels from the BSS-free channel list, wherein a first channel is chosen from the first sub-band, a second channel is chosen from the second sub-band, and a third channel is chosen from the third sub-band,;
• if the allowed channel list includes channels from the first and second sub-bands, then determining whether the BSS-free channel list has less than two channels,
• if so, then choosing three channels from the allowed channel list, wherein a first channel is chosen from the first sub-band, a second channel is chosen from the first sub-band, and a third channel is chosen from the second sub-band,
• if not, then choosing three channels from the BSS-free channel list, wherein a first channel is chosen from the first sub-band, a second channel is chosen from the first sub-band, and a third channel is chosen from the second sub-band;
• and
• if the allowed channel list includes channels from only the first sub-band, then determining whether the BSS-free channel list has less than two channels,
• if so, then choosing two channels from the allowed channel list in the first sub-band,
• if not, then choosing two channels from the BSS-free channel list in the first sub-band.

A method of populating a radar-free channel list for a wireless local area network (WLAN) device operable in a 5 GHz spectrum, the spectrum being divided into 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:

• populating an allowed channel list with channels allowed by a regulatory domain for that spectrum;
• populating a BSS-free channel list with the allowed channels having acceptable levels of current WLAN transmission thereon;
• if the allowed channel list includes channels from all the sub-bands, then determining whether the BSS-free channel list has less than two channels,
• if so, then choosing three channels from the allowed channel list,
• if not, then choosing three channels from the BSS-free channel list;
• if the allowed channel list includes channels from only two sub-bands, then determining whether the BSS-free channel list has less than two channels,
• if so, then choosing three channels from the allowed channel list,
• if not, then choosing three channels from the BSS-free channel list;
• and
• if the allowed channel list includes channels from only one sub-band, then determining whether the BSS-free channel list has less than two channels,
• if so, then choosing two channels from the allowed channel list,
• if not, then choosing two channels from the BSS-free channel list.

A method of performing a startup 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:

• (i) populating an allowed channel list with the allowed channels;
• (ii) populating a BSS-free channel list with allowed channels having acceptable levels of current WLAN transmission thereon;
• (iii) populating a radar-free channel list using the BSS-free channel list and the allowed channel list;
• (iv) performing a radar scan on each channel in the radar-free channel list;
• (v) deleting any channel with radar in the radar-free channel list;
• (vi) repeating steps (i)-(v) until a predetermined number of channels remain in the radar-free channel list;
• (vii) choosing a first channel in the radar-free channel list for operation;
• and
• (viii) beginning operation with the first channel.

A method of performing a startup 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:

• (i) populating an allowed channel list with the allowed channels;
• (ii) populating a BSS-free channel list with allowed channels having acceptable levels of current WLAN transmission thereon;
• (iii) populating a radar-free channel list using the BSS-free channel list, if possible, and otherwise the allowed channel list;
• (iv) performing a radar scan on each channel in the radar-free channel list;
• (v) deleting any channel with radar in the radar-free channel list;
• (vi) repeating steps (i)-(v) until a predetermined number of channels remain in the radar-free channel list;
• (vii) choosing a first channel in the radar-free channel list for operation;
• and
• (viii) beginning operation with the first channel.

A method of switching channels for an access point operating in a 5 GHz spectrum, wherein the 5 GHz spectrum is divided into 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;
• if the access point is operating in the first sub-band, then setting a new channel to a most distant channel in the radar-free channel list;
• and
• if the access point is 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.

A method of switching channels for an access point operating in a 5 GHz spectrum, wherein the 5 GHz spectrum is divided into 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;
• and
• setting a new channel to one of a most distant channel, a lowest channel, and a highest channel in the radar-free channel list,
• wherein if the access point is 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 the highest channel.

A method of switching channels for an access point operating in a 5 GHz spectrum, wherein the 5 GHz spectrum is divided into 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;
• and
• setting a new channel to one of a most distant channel, a lowest channel, and a highest channel in the radar-free channel list,
• wherein if the access point is operating in the third sub-band, then setting the new channel to the lowest channel.

A method of designating backup channels for a radar-free channel list usable by an access point operable in a spectrum, the method comprising:

• determining candidate backup channels for the radar-free channel list;
• performing a radar scan on each candidate backup channel until a radar-free channel is found and deleting any candidate backup channel from the radar-free channel list found with radar during the step of performing;
• choosing the radar-free channel as a current channel and deleting the radar-free channel from the radar-free channel list;
• sending beacons using the current channel;
• allowing stations to authenticate and associate with the access point;
• scanning other candidate backup channels in the radar-free channel using any associated stations that are willing to scan, or else the access point;
• and
• designating candidate backup channels as backup channels and deleting candidate backup channels with radar from the radar-free channel list during the step of scanning.

A method of performing a startup 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:

• (i) populating an allowed channel list with the allowed channels;
• (ii) populating a BSS-free channel list with allowed channels having acceptable levels of current WLAN transmission thereon;
• (iii) populating a radar-free channel list using the BSS-free channel list and the allowed channel list;
• (iv) randomly selecting a first channel from the radar-free channel list;
• (v) if the first channel is in a first sub-band and the regulatory domain exempts scanning in the first sub-band, then designating the first channel as a current channel, selecting a backup channel from the radar-free channel list in the first sub-band without scanning, and proceeding directly to (xi);
• (vi) if the first channel is not in the first sub-band and the regulatory domain exempts scanning in the first sub-band, then performing a radar scan on each channel in the radar-free channel list, except any channel in the first sub-band;
• (vii) if the first channel is in the first sub-band and the regulatory domain requires scanning in the first sub-band, then performing a radar scan on each channel in the radar-free channel list;
• (viii) for steps (vi) and (vii), deleting any channel with radar in the radar-free channel list;
• (ix) repeating steps (i)-(viii) until a predetermined number of channels remain in the radar-free channel list;
• (x) after step (ix), choosing a first channel in the radar-free channel list for operation;
• and
• (xi) beginning operation with the first channel.