Enhanced passive scanning

• US 7,583,643 B2
• Filed: 09/30/2003
• Issued: 09/01/2009
• Est. Priority Date: 09/30/2003
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Wilson, Timothy J., Smith, Brian K., Simpson, Floyd D.
• Primary Examiner(s): Harper; Vincent P.
• Assistant Examiner(s): Casca; Fred A
• Application Number:
  US10/674,984
• Publication Number:
  US 20050068928A1
• Time in Patent Office: 2,163 Days
• Field of Search: 370/311, 370/338, 370/329, 455/432.1
• US Class Current: 370/338
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

The application provides an enhanced passive scanning method for a wireless local area network, including the steps of receiving (405) at least one of a beacon signal (342, 348) or a gratuitous probe response (344), updating (435) a site timing table entry in a site timing table based on the received beacon signal (342, 348) or gratuitous probe response (344), setting (445) a scan start time based on entries in the updated site timing table, and determining (450) a power mode for a wireless communication device based on the scan start time. An enhanced passive scanning system (200, 500, 600) and computer usable medium for enhanced passive scanning is also disclosed.

Claims

1. An enhanced passive scanning method for a wireless local area network, comprising:

receiving a gratuitous probe response;

updating a site timing table entry in a site timing table based on the received gratuitous probe response;

setting a scan start time for a neighboring access point or mobile device based on entries in the updated site timing table; and

determining a power mode for a wireless communication device based on the scan start time by determining a time period remaining until a target gratuitous probe response transmission time is scheduled.

2. The method of claim 1 wherein a beacon signal or the gratuitous probe response are received from a mobile station or an access point.

3. The method of claim 1 wherein the receiving step further comprises receiving a beacon signal from an access point, the beacon signal including an access-point timestamp, a beacon interval, a basic service set identifier, and a traffic indication map and the site timing table entry is undated based on the received beacon signal or gratuitous probe response.

4. The method of claim 1 wherein the gratuitous probe response is received from an access point, the gratuitous probe response including an access-point timestamp, a gratuitous probe response interval, and a basic service set identifier.

5. The method of claim 1 wherein the updated site timing table includes an access-point timestamp, a local station timestamp, a beacon interval, and a gratuitous probe response interval.

6. The method of claim 1 further comprising:

scanning at least one channel for a beacon signal or the gratuitous probe response.

7. The method of claim 6 wherein scanning at least one channel comprises one of performing an active scan, performing a passive scan, or performing an enhanced passive scan.

8. The method of claim 1 further comprising:

creating the site timing table with at least one site timing table entry, the site timing table based on a received beacon signal or a gratuitous probe response.

9. The method of claim 8 wherein creating the site timing table entry comprises tuning to an access point channel, receiving the beacon signal or the gratuitous probe response, collecting transmission measurements of an access point, and storing access point information in the site timing table.

10. The method of claim 1 further comprising:

selecting an access point based on received beacon signals or the received gratuitous probe responses.

11. The method of claim 1 further comprising:

generating an enhanced passive scan schedule based on at least one site timing table entry in the site timing table, the enhanced passive scan schedule including a channel number, a local scan start time, and a maximum channel scan time for each site timing table entry in the site timing table.

12. An enhanced passive scanning system for a wireless local area network, comprising:

means for receiving a gratuitous probe response;

means for updating a site timing table entry in a site timing table based on the received gratuitous probe response; and

means for setting a scan start time for a neighboring access point or mobile device based on entries in the updated site timing table; and

means for determining a power mode for a wireless communication device based on the scan start time by determining a time period remaining until a target gratuitous probe response transmission time is scheduled.

13. The system of claim 12 further comprising:

means for scanning at least one channel for a beacon signal or the gratuitous probe response.

14. The system of claim 13 further comprising:

means for creating the site timing table with at least one site timing table entry, the site timing table based on a received beacon signal or a gratuitous probe response.

15. The system of claim 12 further comprising:

means for selecting an access point based on received beacon signals or the received gratuitous probe responses.

16. The system of claim 12 further comprising:

means for generating an enhanced passive scan schedule based on at least one site timing table entry in the site timing table, the enhanced passive scan schedule including a channel number, a local scan start time, and a maximum channel scan time for each site timing table entry in the site timing table.