Unconnected power save mode for improving battery life of wireless stations in wireless local area networks

• US 7,403,774 B2
• Filed: 09/29/2004
• Issued: 07/22/2008
• Est. Priority Date: 09/29/2004
• Status: Active Grant

• Current Assignee: Telogy Networks, Inc. (Texas Instruments, Inc.)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Chandra, Praphul, Sindhwani, Manoj, Lide, David
• Primary Examiner(s): Vo; Nguyen
• Application Number:
  US10/953,289
• Publication Number:
  US 20060068751A1
• Time in Patent Office: 1,392 Days
• Field of Search: 455/432.1, 455/434, 455/436, 455/515, 455/574, 455/161.1, 455/343.1, 455/343.2, 370/338
• US Class Current: 455/432.1
• CPC Class Codes: H04B 1/1615 Switching on; Switching off, e.g. remotely battery saving circuits associated with selective call operation H04W52/00; details of power consumption reduction in a PLL, H03L7/0802, H03L7/14, H03L2207/08, H03L2207/18; muting amplifiers by gain control see H03G3/34
• CPC Class Codes: H04W 52/0241 where no transmission is received, e.g. out of range of the transmitter
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

An unconnected power save method reduces the battery consumption of a wireless station in a wireless local area network (WLAN). A wireless station enters a sleep mode between scans for a prospective access point. The sleep duration time is determined using the current position of the station relative to the WLAN network topology.

Claims

1. A method for improving battery life of a wireless device in a wireless local area network having a topology, said method comprising:

scanning, with a wireless station, for an identifying signal from a prospective access point in a wireless local area network;

memorizing, during said scanning, identifying signals from one or more access points that are geographically near to said prospective access point;

entering an unconnected power save mode, wherein the wireless device is in a sleep mode having a sleep mode duration which is determined using the current position of the wireless device relative to the wireless local area network topology; and

reducing a sleep mode duration of said wireless station when said wireless station detects said memorized identifying signals.

2. The method of claim 1, wherein if said wireless station fails to detect said identifying signal from said prospective AP, increasing said sleep mode duration of said wireless station after said wireless station unsuccessfully scans for said identifying signal from said prospective access point.

3. The method of claim 2, wherein said increasing said sleep mode duration further comprises increasing a time of said sleep mode when a number of scans for said prospective access point by said wireless station is greater than a threshold number of scans.

4. The method of claim 1, wherein said memorizing comprises creating a list of said identifying signals from said one or more access points that are near to said prospective access point;

and

if said wireless station detects and connects to said prospective access point, updating said list with identification numbers of said one or more access points and a channel number of said connected prospective access point.

5. The method of claim 4, further comprising:

determining if said wireless station is near to said prospective access point by matching identifying signals from any access points detected during a current scan to said memorized list of identifying signals of said near access points.

6. The method of claim 1, further comprising:

memorizing a list of one or more channels used by said prospective access point; and

scanning only said one or more channels in order to said identifying signal from said prospective access point.

7. The method of claim 1, wherein said reducing comprises adjusting said sleep mode according to minimum thresholds of time of said sleep mode.

8. The method of claim 7, wherein said thresholds of said sleep mode are determined based upon unsuccessful scan count thresholds of said wireless station.

9. The method of claim 1, wherein said increasing comprises adjusting said sleep mode according to maximum thresholds of time of said sleep mode.

10. The method of claim 1, wherein said scanning comprises scanning, with a wireless Internet Protocol telephone.

11. A method for improving battery life of a wireless device in an IEEE 802.11 wireless local area network (WLAN), comprising:

scanning, with a wireless station, for wireless signals from access points containing basic service set identification numbers (BSSIDs);

creating a list of said BSSIDS detected from said scanning;

determining if said wireless station is close to a prospective access point by comparing said list of said BSSIDs of said access points to a list of BSSIDs of neighboring access points to said prospective access point; and

if said station is close to said prospective access point, increasing the periodicity of scans by said station for said prospective access point.

12. The method of claim 11, further comprising:

if said wireless station is close to said prospective access point but remains unconnected after said increased periodicity of scans, then increasing said time of said sleep mode.

13. The method of claim 12, wherein said increasing said time of said sleep mode further comprises increasing said time of said sleep mode when a number of scans for said prospective access point by said wireless station is greater than a threshold number of scans.

14. The method of claim 11, further comprising:

if said wireless station connects to said prospective access point, updating said neighbor list with BSSIDs from said scans of said access points.

15. The method of claim 11, further comprising:

saving a list of particular channels used by said prospective access point; and

scanning only said particular channels in order to connect to said prospective access point.

16. The method of claim 11, wherein said reducing comprises adjusting said sleep mode according minimum and maximum thresholds of time of said sleep mode.

17. The method of claim 16, wherein said minimum and maximum thresholds of said sleep mode are determined based upon minimum and maximum unsuccessful scan count thresholds.