Method for steering smart antenna beams for a WLAN using MAC layer functions

• US 20050221838A1
• Filed: 03/15/2005
• Published: 10/06/2005
• Est. Priority Date: 03/17/2004
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Cha, Inhyok, Zhao, Zheng, Gorsuch, Thomas Eric, Lintelman, Ross L.
• Granted Patent: US 7,200,376 B2
• Time in Patent Office: Days
• US Class Current: 455/452.200
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0695 using beam selection
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A smart antenna steering algorithm operates in response to different functions monitored by the media access control (MAC) layer within a client station. One function is when the MAC layer indicates that the client station has been placed in a power savings mode. In response, the antenna algorithm stores an index of the currently selected antenna. Another function is when the MAC layer indicates that the client station has not been synchronized, associated and authenticated with an access point. In response, the algorithm selects an omni-directional antenna beam as the default antenna beam. Another function is when the MAC layer provides beacon period synchronization information to the antenna steering algorithm so that the algorithm can update its own timer.

Claims

1. A method for operating a client station in a wireless local area network (WLAN) communication system comprising an access point, the client station comprising an antenna steering algorithm and a smart antenna responsive to the antenna steering algorithm for selecting one of a plurality of antenna beams, the method comprising:

placing the client station in a powered on state;

computing a status metric indicating a status of the following events

synchronization of the client station with the access point,

association of the client station with the access point, and

authentication of the client station by the access point;

the status metric having a first value when the events are met and a second value when anyone of the events is not met;

scanning the plurality of antenna beams for selecting a preferred antenna beam for exchanging data with the access point when the status metric has the first value;

monitoring the status metric; and

changing the preferred antenna beam to a default antenna beam when the status metric changes from the first value to the second value.

2. A method according to claim 1 wherein the default antenna beam comprises an omni-directional antenna beam.

3. A method according to claim 1 further comprising resetting at least one timer associated with the antenna steering algorithm when the status metric changes from the first value to the second value.

4. A method according to claim 3 further comprising scanning the plurality of antenna beams for selecting a new preferred antenna beam when the status metric changes from the second value to the first value.

5. A method according to claim 1 wherein the events associated with the status metric are monitored within a media access control (MAC) layer of the client station.

6. A method according to claim 1 wherein the plurality of antenna beams comprise a plurality of directional antenna beams and an omni-directional antenna beam.

7. A method according to claim 1 wherein the WLAN comprises an 802.11 WLAN.

8. A method for operating a client station in a wireless local area network (WLAN) communication system comprising an access point, the client station comprising an antenna steering algorithm and a smart antenna responsive to the antenna steering algorithm for selecting one of a plurality of antenna beams, the method comprising:

placing the client station in a powered on state;

computing a power metric, the power metric having a first value indicating that the client station is in the powered on state and a second value indicating that the client station is in a power savings state;

scanning the plurality of antenna beams for selecting a preferred antenna beam and at least one alternate antenna beam for exchanging data with the access point when the power metric has the first value;

monitoring the power metric for a change from the first value to the second value; and

storing selection of the antenna beams for the preferred antenna beam and for the at least one alternate antenna beam when the power metric changes to the second value indicating that the client station is in the power savings state.

9. A method according to claim 8 further comprising resetting at least one timer associated with the antenna steering algorithm when the power metric changes from the first value to the second value.

10. A method according to claim 9 further comprising performing a re-scan using the antenna beams corresponding to the saved selections when the power metric changes from the second value to the first value.

11. A method according to claim 8 wherein the power metric is computed within a media access control (MAC) layer of the client station.

12. A method according to claim 8 wherein the plurality of antenna beams comprise a plurality of directional antenna beams and an omni-directional antenna beam.

13. A method according to claim 12 wherein the at least one alternate antenna beam comprises the omni-directional antenna beam.

14. A method according to claim 8 wherein the WLAN comprises an 802.11 WLAN.

15. A method for operating a client station in a wireless local area network (WLAN) communication system comprising an access point, the client station comprising an antenna steering algorithm and a smart antenna responsive to the antenna steering algorithm for selecting one of a plurality of antenna beams, the method comprising:

receiving beacon frames from the access point for setting a first beacon timer tracking beacon periods of the received beacon frames, the first beacon timer being operated separate from the antenna steering algorithm;

periodically synchronizing the first beacon timer with a second beacon timer being operated at the antenna steering algorithm for also tracking the beacon periods of the received beacon frames; and

running the second beacon timer during each antenna beam searching period.

16. A method according to claim 15 wherein the first beacon timer is maintained in a media access layer (MAC) of the client station

17. A method according to claim 15 wherein the plurality of antenna beams comprise a plurality of directional antenna beams and an omni-directional antenna beam.

18. A method according to claim 15 wherein the WLAN comprises an 802.11 WLAN.