Access point power save mechanism for wireless communication systems

• US 8,611,268 B1
• Filed: 04/15/2011
• Issued: 12/17/2013
• Est. Priority Date: 04/15/2011
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Thandaveswaran, Subramania Sharma
• Primary Examiner(s): Chou, Albert T
• Application Number:
  US13/088,081
• Time in Patent Office: 977 Days
• Field of Search: 370/311, 455/422.1, 455/552.1
• US Class Current: 370/311
• CPC Class Codes: H04W 48/12 using downlink control channel
• CPC Class Codes: H04W 52/0206 in access points, e.g. base stations access point devices per se H04W88/08
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Power saving mechanisms can be implemented in an access point to improve power consumption. The access point can be configured to switch from an active power mode to a power save mode in response to not detecting communication activity for at least a predetermined idle time interval. In the power save mode, one or more sleep sub-states and one or more awake sub-states are initiated at the access point. During each awake sub-state, it is determined whether the awake sub-state coincides with a beacon transmission time instant. The access point broadcasts a probe response message if the awake sub-state does not coincide with the beacon transmission time instant. The access point broadcasts a beacon message if the awake sub-state coincides with the beacon transmission time instant.

Claims

1. A method comprising:

switching from an active power mode to a power save mode at an access point, in response to not detecting communication activity associated with the access point for a predetermined idle time interval threshold;

initiating a sleep sub-state and an awake sub-state during the power save mode of the access point;

determining whether the awake sub-state coincides with a beacon transmission time instant associated with the access point;

broadcasting a probe response message associated with the access point during the awake sub-state, in response to determining that the awake sub-state does not coincide with the beacon transmission time instant; and

broadcasting a beacon message associated with the access point during the awake sub-state, in response to determining that the awake sub-state coincides with the beacon transmission time instant.

2. The method of claim 1, wherein the sleep sub-state and the awake sub-state are consecutive and periodically repeating time intervals during the power save mode.

3. The method of claim 1, wherein the communication activity associated with the access point comprises data packets received at the access point, management packets received at the access point, data packets scheduled to be transmitted by the access point, and management packets scheduled to be transmitted by the access point.

4. The method of claim 1, further comprising:

in response to determining that the awake sub-state has elapsed, determining whether to initiate the sleep sub-state based, at least in part, on whether the sleep sub-state coincides with the beacon transmission time instant;

initiating another awake sub-state for broadcasting the beacon message, in response to determining that the sleep sub-state coincides with the beacon transmission time instant; and

initiating the sleep sub-state, in response to determining that the sleep sub-state does not coincide with the beacon transmission time instant.

5. The method of claim 4, wherein said initiating the sleep sub-state further comprises:

determining that the sleep sub-state of the power save mode comprises a first sleep cycle;

determining whether the first sleep cycle coincides with the beacon transmission time instant;

in response to determining that the first sleep cycle coincides with the beacon transmission time instant,

initiating the awake sub-state at the access point for broadcasting the beacon message;

in response to determining that the first sleep cycle does not coincide with the beacon transmission time instant,

initiating the first sleep cycle of the sleep sub-state at the access point;

determining whether to initiate a second sleep cycle of the sleep sub-state;

initiating the second sleep cycle of the sleep sub-state at the access point, in response to determining to initiate the second sleep cycle of the sleep sub-state; and

initiating the awake sub-state of the power save mode, in response to determining not to initiate the second sleep cycle of the sleep sub-state.

6. The method of claim 1,

wherein the sleep sub-state comprises a time interval during which the access point is configured in an inactive power state or during which processing components of the access point are disabled;

and

wherein the awake sub-state comprises a time interval during which the access point is configured in an active power state for maintaining link connectivity and for indicating presence of the access point.

7. The method of claim 1, wherein said initiating the sleep sub-state and the awake sub-state during the power save mode further comprises:

subdividing a beacon interval associated with the access point during the power save mode into a plurality of power save time intervals,

wherein the sleep sub-state comprises a sleep cycle that comprises one of the plurality of power save time intervals, and

wherein the awake sub-state comprises an awake cycle that comprises one of the plurality of power save time intervals.

8. The method of claim 1, further comprising:

determining whether communication activity was detected at the access point during the awake sub-state of the power save mode;

causing the access point to switch from the power save mode to an active power mode, in response to determining that communication activity was detected at the access point; and

causing the access point to continue to remain in the power save mode, in response to determining that communication activity was not detected at the access point.

9. The method of claim 8, wherein said determining whether communication activity was detected at the access point during the awake sub-state comprises at least one of:

determining whether the access point is scheduled to initiate a packet transmission,

determining whether a packet reception was detected at the access point, and

determining whether a request for data intended for a client station associated with the access point was detected at the access point.

10. The method of claim 1, further comprising:

determining whether communication activity was not detected at the access point configured in the active power mode for the predefined idle time interval threshold;

switching from the active power mode to the power save mode, in response to determining that communication activity was not detected at the access point for the predefined idle time interval threshold; and

causing the access point to remain in the active power mode, in response to determining that communication activity was detected at the access point during the predefined idle time interval threshold.

11. The method of claim 1, wherein the access point comprises a wireless local area network (WLAN) access point.

12. A network device comprising:

a processor;

a network interface coupled with the processor; and

a power save unit coupled with the processor and with the network interface, the power save unit operable to;

switch from an active power mode to a power save mode, in response to not detecting communication activity associated with the network device for a predetermined idle time interval threshold;

initiate a sleep sub-state and an awake sub-state during the power save mode of the network device;

determine whether the awake sub-state coincides with a beacon transmission time instant associated with the network device;

broadcast a probe response message associated with the network device during the awake sub-state, in response to the power save unit determining that the awake sub-state does not coincide with the beacon transmission time instant; and

broadcast a beacon message associated with the network device during the awake sub-state, in response to the power save unit determining that the awake sub-state coincides with the beacon transmission time instant.

13. The network device of claim 12, wherein the sleep sub-state and the awake sub-state are consecutive and periodically repeating time intervals during the power save mode.

14. The network device of claim 12, wherein the communication activity associated with the network device comprises data packets received at the network device, management packets received at the network device, data packets scheduled to be transmitted by the network device, and management packets scheduled to be transmitted by the network device.

15. The network device of claim 12, wherein the power save unit is further operable to:

in response to the power save unit determining that the awake sub-state has elapsed, determine whether to initiate the sleep sub-state based, at least in part, on the power save unit determining whether the sleep sub-state coincides with the beacon transmission time instant;

initiate another awake sub-state for broadcasting the beacon message, in response to the power save unit determining that the sleep sub-state coincides with the beacon transmission time instant; and

initiate the sleep sub-state, in response to the power save unit determining that the sleep sub-state does not coincide with the beacon transmission time instant.

16. The network device of claim 15, wherein the power save unit operable to initiate the sleep sub-state further comprises the power save unit operable to:

determine that the sleep sub-state of the power save mode comprises a first sleep cycle;

determine whether the first sleep cycle coincides with the beacon transmission time instant;

in response to the power save unit determining that the first sleep cycle coincides with the beacon transmission time instant,

initiate the awake sub-state at the network device for broadcasting the beacon message;

in response to the power save unit determining that the first sleep cycle does not coincide with the beacon transmission time instant,

initiate the first sleep cycle of the sleep sub-state at the network device;

determine whether to initiate a second sleep cycle of the sleep sub-state;

initiate the second sleep cycle of the sleep sub-state at the network device, in response to the power save unit determining to initiate the second sleep cycle of the sleep sub-state; and

initiate the awake sub-state of the power save mode, in response to the power save unit determining not to initiate the second sleep cycle of the sleep sub-state.

17. The network device of claim 12, wherein the power save unit is further operable to:

determine whether communication activity was detected at the network device during the awake sub-state of the power save mode;

cause the network device to switch from the power save mode to an active power mode, in response to the power save unit determining that communication activity was detected at the network device; and

cause the network device to continue to remain in the power save mode, in response to the power save unit determining that communication activity was not detected at the network device.

18. A non-transitory machine-readable storage medium having instructions stored therein, which when executed by a processor causes the processor to perform operations that comprise:

switching from an active power mode to a power save mode, in response to not detecting communication activity associated with an access point for a predetermined idle time interval threshold;

initiating a sleep sub-state and an awake sub-state during the power save mode, wherein the sleep sub-state and the awake sub-state are consecutive and periodically repeating time intervals during the power save mode;

determining whether the awake sub-state coincides with a beacon transmission time instant associated with the access point;

broadcasting a probe response message associated with the access point during the awake sub-state, in response to determining that the awake sub-state does not coincide with the beacon transmission time instant; and

broadcasting a beacon message associated with the access point during the awake sub-state, in response to determining that the awake sub-state coincides with the beacon transmission time instant.

19. The non-transitory machine-readable storage medium of claim 18, wherein the communication activity associated with the access point comprises data packets received at the access point, management packets received at the access point, data packets scheduled to be transmitted by the access point, and management packets scheduled to be transmitted by the access point.

20. The non-transitory machine-readable storage medium of claim 18, wherein the operations further comprise:

in response to determining that the awake sub-state has elapsed, determining whether to initiate the sleep sub-state based, at least in part, on whether the sleep sub-state coincides with the beacon transmission time instant;

initiating another awake sub-state for broadcasting the beacon message, in response to determining that the sleep sub-state coincides with the beacon transmission time instant; and

initiating the sleep sub-state, in response to determining that the sleep sub-state does not coincide with the beacon transmission time instant.

21. The non-transitory machine-readable storage medium of claim 20, wherein said operation of initiating the sleep sub-state further comprises:

determining that the sleep sub-state of the power save mode comprises a first sleep cycle;

determining whether the first sleep cycle coincides with the beacon transmission time instant;

in response to determining that the first sleep cycle coincides with the beacon transmission time instant,

initiating the awake sub-state at the access point for broadcasting the beacon message;

in response to determining that the first sleep cycle does not coincide with the beacon transmission time instant,

initiating the first sleep cycle of the sleep sub-state at the access point;

determining whether to initiate a second sleep cycle of the sleep sub-state;

initiating the second sleep cycle of the sleep sub-state, in response to determining to initiate the second sleep cycle of the sleep sub-state; and

initiating the awake sub-state of the power save mode, in response to determining not to initiate the second sleep cycle of the sleep sub-state.