Efficient power management in wireless local area networks

• US 20050152324A1
• Filed: 01/12/2005
• Published: 07/14/2005
• Est. Priority Date: 01/12/2004
• Status: Active Grant

• Current Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Original Assignee: Avaya Incorporated
• Inventors: Benveniste, Mathilde
• Granted Patent: US 7,603,146 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04W 28/10 Flow control between communication endpoints
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/44 in connection with interruption of transmission
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method of providing power management in a Wireless Local Area Network (WLAN) is presented. The method includes receiving a Traffic Indication Map (TIM) at a station, indicating the presence of buffered frames, associated with any AC, for the station at an Access Point (AP). The method further includes sending, by the station, one of an uplink data frame if one is buffered, and a null frame to retrieve the buffered frames from said AP. The station remains awake to receive frames from the AP until a downlink frame is received containing an indication that it is the last frame to be transmitted in the service period. The method may further include determining at the end of service period whether there are more frames remaining buffered for the station at the AP.

Claims

1. A method of providing power management in a Wireless Local Area Network (WLAN) comprising:

receiving a Traffic Indication Map (TIM) at a station, said TIM indicating the presence of buffered frames, associated with any AC, for said station at an Access Point (AP);

sending, by said station, one of an uplink QoS Data frame if one is buffered, and a Null frame to retrieve said buffered frames from said AP; and

said station remaining awake to receive frames from the AP until a downlink frame is received containing an indication that it is the last frame to be transmitted in the service period.

2. A method of providing power management in a Wireless Local Area Network (WLAN) comprising:

sending, by a station, one of an uplink data frame if one is buffered, and a null frame to retrieve said buffered frames from said AP;

said station remaining awake to receive frames from the AP until a downlink frame is received containing an indication that it is the last frame to be transmitted in the service period; and

determining at the end of service period whether there are more frames remaining buffered for said station at the AP.

3. The method of claim 2 wherein said station retrieving remaining buffered frames by one of sending a null frame, sending PS Polls, and entering the Active mode and then transitioning back to PS mode.

4. A method of providing power management in a Wireless Local Area Network (WLAN) comprising:

receiving, by said station, a periodic downlink traffic stream from an Access Point (AP) during a scheduled period;

said station remaining awake to receive frames from the AP until a downlink frame is received containing an indication that it is the last frame to be transmitted in the service period; and

determining, when said station receives the indication of the end of the service period in the downlink frame, whether there are more frames remaining buffered for said station at the AP.

5. The method of claim 4 wherein said station retrieving any remaining buffered frames by one of sending a null frame, sending PS Polls, and by entering the Active mode and then transitioning back to PS mode.

6. The method of claim 4 further comprising indicating, by a station, a time when said station expects to receive traffic

7. The method of claim 4 wherein a service period schedule is produced by the AP by determining a service interval and a start time so that overlap between service periods of different stations is minimized.

8. The method of claim 7 further comprising adjusting the service start time to be later than or equal to a requested service start time and less than a service period relative to said requested start time.

9. The method of claim 4 wherein said station uses Enhanced Distributed Channel Access (EDCA) and wherein a service period schedule comprises a predetermined schedule.

10. The method of claim 9 further comprising delivering by said AP buffered frames to said station at the start of said service period.

11. The method of claim 9 wherein said schedule includes staggered service periods for different stations.

12. The method of claim 9 wherein, after said AP transmits buffered frames to a station, refraining from transmitting for a predetermined time period.

13. The method of claim 9 further comprising using backoff delays drawn from a shorter contention window by said EDCA station than other EDCA stations with a same priority traffic.

14. A method of providing power management in Wireless Local Area Networks (WLANs) comprising:

determining that downlink traffic between an Access Point (AP) and a station in power saving mode comprises periodic traffic and non-periodic traffic;

utilizing scheduled Automatic Power Saving Delivery (APSD) for delivery of said periodic traffic; and

utilizing unscheduled APSD for delivery of non-periodic traffic.

15. The method of claim 14 wherein said utilizing scheduled APSD includes determining the schedule in accordance with a first Traffic Specification (TSPEC).

16. The method of claim 14 wherein said utilizing unscheduled APSD includes using an uplink stream of null frames generated when said station receives a Traffic Indicator Map (TIM) indicating the presence of buffered frames at said AP.

17. A method of deriving a schedule in a Wireless Local Area Network (WLAN) comprising:

adopting a basic service interval;

determining whether the service interval in the Traffic Specification (TSPEC) is a multiple of said basic service interval;

when said service interval is a multiple of said basic service interval then accepting said TSPEC;

when said service interval is not a multiple of said basic service interval then denying said TSPEC;

slotting channel time into time schedule channels repeating at fixed time intervals equal to the basic service interval; and

assigning an time schedule channel to a TSPEC based on the service interval contained in said TSPEC and the service intervals of other TSPECs already assigned said channel.

18. The method of claim 17 wherein said denying a scheduled APSD TSPEC further comprises use of Unscheduled APSD.

19. The method of claim 17 wherein said schedule is used for one of APSD and polling.