Off-channel beacons in a wireless network

• US 20070014267A1
• Filed: 07/15/2005
• Published: 01/18/2007
• Est. Priority Date: 07/15/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Krischer, Mark, Hart, Brian, Stephenson, David, Lam, Alex
• Granted Patent: US 7,457,620 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04W 48/10 using broadcasted information
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A method, apparatus, and software containing computer readable code to implement the method implemented in a first wireless device. The method includes, for a particular network identifier active in a wireless network, transmitting frames configured to advertise the infrastructure network of the particular network identifier. The transmitting of off-channel beacons is in a provided channel different than the channel in which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames. The transmitting of off-channel beacons further is at a rate higher than the beacon rate frame at which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames.

Claims

1. A method in a first wireless device, the wireless device including a transmitter and modulator for transmitting, and MAC hardware coupled to the transmitter and modulator, the method comprising:

for a particular network identifier of at least one network identifier active in a wireless network that supports at least one network identifier, each network identifier identifying an infrastructure wireless network, each infrastructure wireless network having an access point transmitting beacon frames at a beacon frame rate,

transmitting frames (“

off-channel beacons”

) from the first wireless device, the off-channel beacon frames configured to advertise the infrastructure wireless network of the particular network identifier by including advertising information advertising the infrastructure wireless network, the transmitting of off-channel beacons being in a provided channel (“

the off-channel-beacon channel”

) different than the channel in which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the transmitting of off-channel beacons further being at a rate higher than the beacon rate frame at which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the advertising information in the off-channel frames including information that indicates the channel or channels where the beacon frames of the advertised infrastructure networks or networks are being transmitted,

such that a second wireless device receiving the off-channel beacon can use the information in the off-channel beacon to switch to any of the channels of the infrastructure wireless network or networks advertised in the off-channel beacon and/or to choose whether or not to associate or re-associate with the channel of any infrastructure network advertised in the off-channel beacon, the second wireless device being configured to interpret the information in the off-channel beacon that advertises the one or more infrastructure wireless networks.

2. A method as recited in claim 1, wherein the off-channel beacon further includes information on the capabilities of the advertised BSS(s).

3. A method as recited in claim 2, wherein the off-channel beacon further includes current loading information for the advertised BSS(s).

4. A method as recited in claim 1, wherein the transmitting of the off-channel beacons in the off-channel-beacon channel is continuous.

5. A method as recited in claim 1, wherein the wireless networks are basic service sets (BSSs) substantially compatible with the IEEE 802.11 standard, and wherein the network identifiers are BSSIDs.

6. A method as recited in claim 1, further comprising:

dissuading a third wireless device from associating with the first wireless device as a result of the third wireless device receiving the off-channel beacon transmitted by the first wireless device, the third wireless device being configured such that it cannot interpret the advertising information in the off-channel beacon.

7. A method as recited in claim 6, wherein the dissuading includes the first wireless device sending the third wireless station a disassociation response to any association request received from the client.

8. A method as recited in claim 6, wherein the off-channel beacon is of a management frame type different from a regular beacon frame type, such that a third wireless device that cannot interpret the advertising information in the off-channel beacon and that receives the off-channel beacon from the first wireless device will not attempt to associate with the first wireless device as a result of receiving the off-channel beacon.

9. A method as recited in claim 1, wherein the off-channel-beacon channel is pre-selected.

10. A method as recited in claim 1, wherein the off-channel-beacon channel is indicated to clients as information included in regular beacon frames and probe responses transmitted by access points in the wireless network.

11. A method as recited in claim 1, wherein the off-channel-beacon channel is indicated to clients as information included in mini-beacon frames transmitted by access points in the wireless network more frequently than and in between full beacons, and that are smaller than the full beacons.

12. A method in a first wireless station of a wireless network, the method comprising:

for a particular network identifier of at least one network identifier active in a wireless network that supports at least one network identifier, each network identifier identifying an infrastructure wireless network, each infrastructure wireless network having an access point transmitting beacon frames at a beacon frame rate,

receiving one or more frames (“

off-channel beacons”

) from a second wireless device, the off-channel beacon frames configured to advertise the infrastructure wireless network of the particular network identifier by including advertising information advertising the infrastructure wireless network, the receiving of off-channel beacons being in a provided channel (“

the off-channel-beacon channel”

) different than the channel in which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the off-channel beacons being transmitted by the second wireless device at a rate higher than the beacon rate frame at which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the advertising information in the off-channel frames including information that indicates the channel or channels where the beacon frames of the advertised infrastructure networks or networks are being transmitted; and

interpreting the information in the received off-channel beacons, such that the first wireless device receiving the off-channel beacon advertising the infrastructure wireless network of the particular network identifier can use the information in the off-channel beacon to switch to any of the channels of the infrastructure wireless network or networks advertised in the off-channel beacon and/or to choose whether or not to associate or re-associate with the channel of any infrastructure network advertised in the off-channel beacon.

13. A method as recited in claim 12, wherein the off-channel beacon channel is pre-selected.

14. A method as recited in claim 12, further comprising:

maintaining a cache of most recent off-channel beacon channels; and

switching to the next most recent off-channel beacon channel to attempt receiving the one or more off-channel beacon frames until the receiving of the one or more off-channel beacon frames is successful.

15. A method as recited in claim 12, wherein the off-channel-beacon channel is indicated to the first wireless station as information included in regular beacon frames and probe responses transmitted by access points in the wireless network, the method further comprising:

receiving a beacon containing an indication of the off-channel beacon channel, and switching to the off-channel beacon channel prior to the receiving of the one or more off-channel beacon frames.

16. A method as recited in claim 12, wherein the off-channel-beacon channel is indicated to clients as information included in mini-beacon frames transmitted by access points in the wireless network more frequently than and in between full beacons, and that are smaller than the full beacons, the method further comprising:

receiving a mini-beacon containing an indication of the off-channel beacon channel, and switching to the off-channel beacon channel prior to the receiving of the one or more off-channel beacon frames.

17. A method in a first wireless device operating as an access point of a wireless network, the method comprising:

transmitting frames that include information indicative of a channel (the “

off-channel beacon channel”

) distinct from data channels, the off-channel beacon channel being the channel where, for a particular network identifier of at least one network identifier active in the wireless network that supports at least one network identifier, each network identifier identifying an infrastructure wireless network, one or more frames (“

off-channel beacons”

) from a second wireless device, the off-channel beacon frames configured to advertise the infrastructure wireless network of the particular network identifier by including advertising information advertising the infrastructure wireless network, the off-channel beacons being transmitted by the second wireless device at a rate higher than rate at which full beacons are transmitted by the first access point, the advertising information in the off-channel frames including information that indicates the channel or channels where the beacon frames of the advertised infrastructure networks or networks are being transmitted; and

such that a third wireless device receiving frames that include information indicative of the off-channel beacon channel and that can interpret off-channel beacons, can switch to the indicated off-channel beacon channel, and receive one or more off-channel beacons that provide for the third wireless device the ability to use the information in the off-channel beacon to switch to any of the channels of the infrastructure wireless network or networks advertised in the off-channel beacon and/or to choose whether or not to associate or re-associate with the channel of any infrastructure network advertised in the off-channel beacon.

18. A method as recited in claim 17, wherein the transmitted frames that include information indicative of the off-channel beacon channel are full beacon frames.

19. A method as recited in claim 17, wherein the transmitted frames that include information indicative of the off-channel beacon channel are mini-beacon frames transmitted more frequently than and in between full beacon frames, and that are smaller than the full beacon frames.

20. A carrier medium, carrying at least one computer readable code segment to instruct one or more processors of a processing system to carry out a method in a first wireless device, the wireless device including a transmitter and modulator for transmitting, and MAC hardware coupled to the transmitter and modulator, the method comprising:

for a particular network identifier of at least one network identifier active in a wireless network that supports at least one network identifier, each network identifier identifying an infrastructure wireless network, each infrastructure wireless network having an access point transmitting beacon frames at a beacon frame rate,

transmitting frames (“

off-channel beacons”

) from the first wireless device, the off-channel beacon frames configured to advertise the infrastructure wireless network of the particular network identifier by including advertising information advertising the infrastructure wireless network, the transmitting of off-channel beacons being in a provided channel (“

the off-channel-beacon channel”

) different than the channel in which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the transmitting of off-channel beacons further being at a rate higher than the beacon rate frame at which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the advertising information in the off-channel frames including information that indicates the channel or channels where the beacon frames of the advertised infrastructure networks or networks are being transmitted, such that a second wireless device receiving the off-channel beacon can use the information in the off-channel beacon to switch to any of the channels of the infrastructure wireless network or networks advertised in the off-channel beacon and/or to choose whether or not to associate or re-associate with the channel of any infrastructure network advertised in the off-channel beacon, the second wireless device being configured to interpret the information in the off-channel beacon that advertises the one or more infrastructure wireless networks.

21. An apparatus in a wireless device including a transmitter and modulator, the apparatus comprising:

for a particular network identifier of at least one network identifier active in a wireless network that supports at least one network identifier, each network identifier identifying an infrastructure wireless network, each infrastructure wireless network having an access point transmitting beacon frames at a beacon frame rate,

means for transmitting frames (“

off-channel beacons”

) from the first wireless device via the transmitter and modulator, the off-channel beacon frames configured to advertise the infrastructure wireless network of the particular network identifier by including advertising information advertising the infrastructure wireless network, the transmitting of off-channel beacons being in a provided channel (“

the off-channel-beacon channel”

) different than the channel in which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the transmitting of off-channel beacons further being at a rate higher than the beacon rate frame at which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the advertising information in the off-channel frames including information that indicates the channel or channels where the beacon frames of the advertised infrastructure networks or networks are being transmitted, such that a second wireless device receiving the off-channel beacon can use the information in the off-channel beacon to switch to any of the channels of the infrastructure wireless network or networks advertised in the off-channel beacon and/or to choose whether or not to associate or re-associate with the channel of any infrastructure network advertised in the off-channel beacon, the second wireless device being configured to interpret the information in the off-channel beacon that advertises the one or more infrastructure wireless networks.

22. An apparatus in a wireless device including a transmitter and modulator, the apparatus including a processing element configured to carry out a method that includes:

for a particular network identifier of at least one network identifier active in a wireless network that supports at least one network identifier, each network identifier identifying an infrastructure wireless network, each infrastructure wireless network having an access point transmitting beacon frames at a beacon frame rate,

transmitting frames (“

off-channel beacons”

) from the first wireless device via the transmitter and modulator, the off-channel beacon frames configured to advertise the infrastructure wireless network of the particular network identifier by including advertising information advertising the infrastructure wireless network, the transmitting of off-channel beacons being in a provided channel (“

the off-channel-beacon channel”

) different than the channel in which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the transmitting of off-channel beacons further being at a rate higher than the beacon rate frame at which the access point of the infrastructure wireless of the particular network identifier transmits beacon frames, the advertising information in the off-channel frames including information that indicates the channel or channels where the beacon frames of the advertised infrastructure networks or networks are being transmitted, such that a second wireless device receiving the off-channel beacon can use the information in the off-channel beacon to switch to any of the channels of the infrastructure wireless network or networks advertised in the off-channel beacon and/or to choose whether or not to associate or re-associate with the channel of any infrastructure network advertised in the off-channel beacon, the second wireless device being configured to interpret the information in the off-channel beacon that advertises the one or more infrastructure wireless networks.