Method of scanning for beacon transmissions in WLAN

• US 20060089138A1
• Filed: 10/26/2004
• Published: 04/27/2006
• Est. Priority Date: 10/26/2004
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Smith, Brian K., Mitra, Suhas
• Granted Patent: US 7,224,970 B2
• Time in Patent Office: Days
• US Class Current: 455/426.100
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A wireless station (114) is within range of more than one access point (120, 124) transmitting on the same channel. The wireless station is associated with one access point and not the other. Consequently the wireless station may receive undesired beacons (304) and desired beacons (302) on the channel. To optimize power save operation the wireless station arbitrates between a scan and shut down scanning procedure (708) and a timed window channel scanning procedure (724), depending on whether the desired beacon is the first received beacon upon waking up from a low power state at a target beacon time.

Claims

1. A method of scanning for beacon transmissions from a wireless local area network (WLAN) access point by a wireless station, comprising:

performing a scan and shut down procedure, including;

waking up a WLAN radio subsystem of the wireless station at a target beacon time;

receiving a beacon on a presently associated channel, the beacon transmission including beacon data including a received access point identifier;

passing the beacon data to a host processor of the wireless station;

placing the WLAN radio subsystem into a low power state immediately after receiving and passing;

comparing the received access point identifier with a presently associated access point identifier, performed by the host processor;

if the received access point identifier is the same as the presently associated access point identifier continuing to the scan and shut down procedure for receiving a next beacon transmission; and

if the received access point identifier is not the same as the presently associated access point identifier, discarding the beacon data and using a timed window scanning procedure for receiving the next beacon transmission.

2. A method of scanning for beacon transmissions as defined in claim 1, wherein receiving the beacon data includes receiving a basic service set identifier as the access point identifier.

3. A method of scanning for beacon transmissions as defined in claim 1, wherein receiving the beacon transmission includes receiving a full beacon.

4. A method of scanning for beacon transmissions as defined in claim 3, wherein receiving the full beacon includes receiving the full beacon at a substantially 100 millisecond interval.

5. A method of scanning for beacon transmissions as defined in claim 1, wherein receiving the beacon transmission includes receiving a supplemental beacon, the supplemental beacon having less beacon data than a full beacon.

6. A method of scanning for beacon transmissions as defined by claim 1, wherein waking up the WLAN radio subsystem at the target beacon time is performed with timing information received in a previously received beacon.

7. A method of scanning for beacon transmissions from a wireless local area network (WLAN) access point by a wireless station, comprising:

performing a timed window scanning procedure, including;

waking up a WLAN radio subsystem of the wireless station at a target beacon time;

receiving a first beacon and a second beacon on a presently associated channel, the first and second beacons including beacon data including a received access point identifier;

passing the beacon data to a host processor of the wireless station;

placing the WLAN radio subsystem into a low power state after the end of a timed window interval;

comparing the received access point identifier of the first beacon with a presently associated access point identifier, performed by the host processor;

if the received access point identifier of the first beacon is the same as the presently associated access point identifier using a scan and shut down procedure for receiving a next beacon transmission; and

if the received access point identifier of the first beacon is not the same as the presently associated access point identifier, discarding the beacon data and using the timed window procedure for receiving the next beacon transmission.

8. A method of scanning for beacon transmissions as defined in claim 7, wherein receiving the beacon data includes receiving a basic service set identifier as the access point identifier.

9. A method of scanning for beacon transmissions as defined in claim 7, wherein receiving the first beacon transmission includes receiving a full beacon.

10. A method of scanning for beacon transmissions as defined in claim 9, wherein receiving the full beacon includes receiving the full beacon at a substantially 100 millisecond interval.

11. A method of scanning for beacon transmissions as defined in claim 7, wherein receiving the first beacon transmission includes receiving a supplemental beacon, the supplemental beacon having less beacon data than a full beacon.

12. A method of scanning for beacon transmissions as defined by claim 7, wherein waking up the WLAN radio subsystem at the target beacon time is performed with timing information received in a previously received beacon.