APPARATUS FOR AND METHOD OF LOW POWER WIRELESS LOCAL AREA NETWORK INDEPENDENT BASIC SERVICE SET MODE OPERATION

• US 20080181154A1
• Filed: 01/31/2007
• Published: 07/31/2008
• Est. Priority Date: 01/31/2007
• Status: Abandoned Application

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Sherman, Itay
• Application Number:
  US11/669,312
• Publication Number:
  US 20080181154A1
• Time in Patent Office: Days
• US Class Current: 370/311
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0219 where the power saving management affects multiple terminals
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A novel and useful apparatus for and method of providing a low power IBSS mode of operation in an ad hoc WLAN. The low power IBSS mechanism enables extremely low power operation when used among stations that implement the mechanism. The mechanism allows the implementation of an IBSS network that is interoperable with standard WLAN IBSS implementations permitting IBSS networks that comprise a mix of stations that implement the mechanism of the present invention with those that do not. Stations synchronize with each other in a manner that takes advantage of the presence of any accurate timing sources, such as the GPS or cellular radio networks. A means is also provided for stations to both advertise the services they are able to support and to discover the services that other stations support in a quick and power efficient manner.

Claims

1. A method of power save operation for use in an ad hoc wireless local area network (WLAN) enabled communication device with access to an accurate timing source, said method comprising the steps of:

acquiring timing information from said accurate timing source;

translating said timing information to a time synchronization function (TSF) having a predetermined offset, said offset adapted to force stations that do not have access to an accurate timing source to synchronize with said communication device; and

publicizing said TSF to other stations in said ad hoc WLAN.

2. The method according to claim 1, further comprising the step of sending beacons incorporating a synchronization indication.

3. The method according to claim 2, wherein said synchronization indication is adapted to indicate whether said station is not synchronized, synchronized to one or more other stations that have access to an accurate timing source or is a timing source with access to an accurate timing source that is used to synchronize the entire ad hoc WLAN.

4. The method according to claim 1, further comprising the step of facilitating the discovery of said communication device by other stations within said ad hoc WLAN discovering by attempting to transmit a beacon every scan period.

5. The method according to claim 1, further comprising the step of advertising to other stations the services supported by said communication device.

6. The method according to claim 5, wherein said step of advertising comprises the step of including a list of said services supported by said communication device in beacon, probe requests or probe response packets.

7. The method according to claim 1, further comprising the step of subdividing a beacon period into a plurality of wakeup periods, whereby stations awake each wakeup period but transmit beacons every beacon period.

8. The method according to claim 1, further comprising the step of switching from a connected state to a lower power scan mode when no traffic is exchanged with said station for a predetermined time period.

9. The method according to claim 1, wherein said accurate timing source comprises a global positioning satellite (GPS) based timing source.

10. The method according to claim 1, wherein said accurate timing source comprises a cellular phone based timing source.

11. The method according to claim 1, wherein said method is implemented in a WLAN medium access control (MAC) within said communication device.

12. The method according to claim 1, wherein said method is implemented in a host device connected to said communication device.

13. A method of power save operation for use in an ad hoc wireless local area network (WLAN) enabled communication device, said method comprising the steps of:

generating a time synchronization function (TSF) having a predetermined offset, said offset adapted to force said communication device to synchronize with stations that do have access to an accurate timing source; and

publicizing said TSF to other stations in said ad hoc WLAN.

14. The method according to claim 13, further comprising the step of sending beacons incorporating a synchronization indication adapted to indicate whether said station is not synchronized, synchronized to one or more other stations that have access to an accurate timing source or is a timing source with access to an accurate timing source that is used to synchronize the entire ad hoc WLAN.

15. The method according to claim 13, further comprising the step of facilitating the discovery of said communication device by other stations within said ad hoc WLAN discovering by attempting to transmit a beacon every scan period.

16. The method according to claim 13, further comprising the step of advertising to other stations the services supported by said communication device.

17. The method according to claim 16, wherein said step of advertising comprises the step of including a list of said services supported by said communication device in beacon, probe requests or probe response packets.

18. The method according to claim 13, further comprising the step of subdividing a beacon period into a plurality of wakeup periods, whereby stations awake each wakeup period but transmit beacons every beacon period.

19. The method according to claim 13, further comprising the step of switching from a connected state to a lower power scan mode when no traffic is exchanged with said station for a predetermined time period.

20. The method according to claim 13, wherein said accurate timing source comprises a global positioning satellite (GPS) based timing source.

21. The method according to claim 13, wherein said accurate timing source comprises a cellular phone based timing source.

22. The method according to claim 13, wherein said method is implemented in a WLAN medium access control (MAC) within said communication device.

23. The method according to claim 13, wherein said method is implemented in a host device connected to said communication device.

24. A wireless local area network (WLAN) station, comprising:

a WLAN radio coupled to an antenna;

a PHY circuit coupled to said WLAN radio;

a medium access control (MAC) coupled to said PHY circuit, said MAC operative to;

generate a time synchronization function (TSF) having a predetermined offset, wherein said TSF and said predetermined offset are generated in accordance with whether said station has access to an accurate timing source;

publicize said TSF to other stations in an ad hoc WLAN; and

a host interface operative to interface said station to an external host.

25. The station according to claim 24, wherein, if said station has access to an accurate timing source, said MAC is operative to:

translate timing information from said accurate timing source to generate said TSF; and

set said predetermined offset to a first offset value adapted to force other stations that do not have access to said accurate timing source to synchronize with said station.

26. The station according to claim 24, wherein, if said station does not have access to an accurate timing source, said MAC is operative to generate said TSF with said predetermined offset set to a second offset value adapted to force said station to synchronize with other stations that do have access to an accurate timing source.

27. The station according to claim 24, wherein said MAC is further operative to advertise to other stations the services supported by said station.

28. The station according to claim 24, wherein said MAC is further operative to include a list of said services supported by said station in beacon, probe requests or probe response packets.

29. The station according to claim 24, wherein said MAC is further operative to subdivide a beacon period into a plurality of wakeup periods, whereby said station awakes each wakeup period but transmits beacons every beacon period.

30. The station according to claim 24, wherein said MAC is further operative to switch from a connected state to a lower power scan mode when no traffic is exchanged with said station for a predetermined time period.

31. A mobile communications device, comprising:

a WLAN station comprising a medium access controller (MAC);

said MAC operative to;

generate a time synchronization function (TSF) having a predetermined offset, wherein said TSF and said offset are generated in accordance with whether said station has access to an accurate timing source;

publicize said TSF to other stations in an ad hoc WLAN; and

advertise services supported by said station in beacon messages transmitted from said station to other stations in said ad hoc WLAN.

32. The mobile communications device according to claim 31, further comprising:

an accurate timing source;

said MAC comprising means operative to;

translate timing information from said accurate timing source to generate said TSF; and

set said predetermined offset to a first offset value adapted to force other stations that do not have access to said accurate timing source to synchronize with said station.

33. The station according to claim 31, wherein said MAC is operative to generate said TSF with said predetermined offset value set to a second offset value adapted to force said station to synchronize with other stations that do have access to an accurate timing source.

34. A method of reducing scan time of an ad hoc wireless local area network (WLAN), said method comprising the steps of:

acquiring timing information from an accurate timing source available to at least one communication device in said ad hoc WLAN;

translating said timing information to a time synchronization function (TSF) having a predetermined offset, said offset adapted to force stations that do not have access to an accurate timing source to synchronize with said communication device;

publicizing said TSF to other stations in said ad hoc WLAN; and

activating scanning on a predetermined frequency and during a time window determined based on said accurate timing source.