Unscheduled power save delivery method in a wireless local area network for real time communication

• US 6,917,598 B1
• Filed: 12/19/2003
• Issued: 07/12/2005
• Est. Priority Date: 12/19/2003
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Smavatkul, Nattavut, Wilson, Timothy J., Chen, Ye, Emeott, Stephen P., Simpson, Floyd D., Wang, Huai Y.
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): LY, ANH VU H
• Application Number:
  US10/741,651
• Publication Number:
  US 20050136833A1
• Time in Patent Office: 571 Days
• Field of Search: 370/311, 370/318, 370/338, 370/346, 370/348, 370/443, 370/444, 370/445, 370/447, 370/448, 370/449, 370/455, 370/461, 370/496
• US Class Current: 370/311
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 52/0225 using monitoring of external events, e.g. the presence of a signal
• CPC Class Codes: H04W 74/06 using polling
• 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 mobile station (106) establishes a real time communication link via an access point (102) for carrying voice or other time-sensitive data. A WLAN subsystem (204) of the mobile station is normally kept in a low power state. Upon initiating a communication link the mobile station signals to the access point that unscheduled power save delivery mode will be used (614), and the access point reserves resources to assure the necessary quality of service. The mobile station initiates a frame transaction by first powering up the WLAN subsystem (712), acquiring the WLAN channel (407), and transmitting a polling frame. Upon successful receipt of the polling frame the access point prepares to reply with an aggregate response. The aggregate response commences by transmitting all data in an aggregate buffer, including both reserved and unreserved data buffers. Upon successful receipt of the aggregate response, the mobile station places the WLAN subsystem back into a low power state.

Claims

1. A method of performing power save operation in a wireless local area network (WLAN) by a mobile station while performing voice communications, comprising:

admitting a reserved traffic stream at an access point, including establishing a reserved buffer at the access point for buffering data corresponding to the reserved traffic stream to be transmitted to the mobile station;

placing a WLAN subsystem of the mobile station in a low power state;

waking up the WLAN subsystem of the mobile station from the low power state in response to the occurrence of a service interval timer event, the service interval timer for timing a service interval, the service interval defining a real time duration of a voice frame;

transmitting a polling frame to the access point over a WLAN channel, the polling frame identifying the reserved traffic stream and including an aggregation indicator;

in response to transmitting the polling frame, receiving an aggregate response at the mobile station over the WLAN channel, wherein the aggregate response includes at least one frame of data from an aggregate buffer of the access point, the aggregate buffer for buffering both unreserved and reserved data for the mobile station, and wherein receiving the aggregate response continues until the aggregate buffer is empty or a service time period expires; and

upon receiving the aggregate response, setting the WLAN subsystem into the low power state.

2. A method of performing power save operation as defined by claim 1, wherein the aggregate response is transmitted in response to aggregate bit in the polling frame.

3. A method of performing power save operation as defined by claim 1, further comprising receiving an acknowledgement frame at the mobile station from the access point over the WLAN channel in response to transmitting the polling frame.

4. A method of performing power save operation as defined by claim 1, further comprising transmitting an acknowledgement frame from the mobile station to the access point over the WLAN channel in response to receiving the at least one response frame.

5. A method of performing power save operation as defined by claim 1, wherein:

receiving the aggregate response includes receiving a header of a first frame of the aggregate response having a MORE_—

DATA bit set to indicate a second response frame will be transmitted subsequently;

the method further comprising receiving a second response frame at the mobile station.

6. A method of performing power save operation as defined by claim 1, wherein transmitting the polling frame comprises transmitting a null frame.

7. A method of performing power save operation as defined by claim 6, wherein transmitting the null frame is performed upon expiration of a window timer initiated upon the beginning of a service interval, the service interval defining a real time duration of a voice frame, the window timer having a duration less than the service interval.

8. A method of performing power save operation as defined by claim 1, further comprising acquiring the WLAN channel after waking up the WLAN subsystem, performed by contending for the WLAN channel.

9. A method of performing power save operation as defined by claim 8, wherein contending for the WLAN channel is performed by carrier sensing.

10. A method of facilitating power save operation by an access point in a wireless local area network (WLAN) while performing voice communications, comprising:

admitting a reserved traffic stream at the access point, including establishing a reserved buffer at the access point for buffering data corresponding to the reserved traffic stream to be transmitted to a mobile station, the reserved buffer and unreserved buffer forming an aggregate buffer at the access point wherein unreserved data is buffered in the unreserved buffer;

placing a WLAN subsystem of the mobile station in a low power state;

waking up the WLAN subsystem of the mobile station from the low power state in response to the occurrence of a service interval timer event, the service interval timer for timing a service interval, the service interval defining a real time duration of a voice frame;

receiving a polling frame at the access point over a WLAN channel from the mobile station, the polling frame identifying the reserved traffic stream;

checking the aggregate buffer for buffered data to be sent to the mobile station; and

transmitting an aggregate response to the mobile station over the WLAN channel, the aggregate response being transmitted by the access point and including data in the aggregate buffer, the transmitting continuing until the aggregate buffer is empty or until a service time period is reached.

11. A method of facilitating power save operation as defined by claim 10, where transmitting the aggregate response is performed in response to the polling frame containing an aggregate bit indicating a desire to use an aggregate response mode.

12. A method of facilitating power save operation as defined by claim 10, further comprising transmitting an acknowledgement frame to the mobile station from the access point over the WLAN channel in response to receiving the polling frame.

13. A method of facilitating power save operation as defined by claim 10, further comprising receiving an acknowledgement frame from the mobile station at the access point over the WLAN channel in response to transmitting the aggregate response.

14. A method of facilitating power save operation as defined by claim 10, wherein:

transmitting the aggregate response includes transmitting a header of a first response frame having a MORE_—

DATA bit set to indicate a second response frame will be transmitted subsequently;

the method further comprising transmitting a second response frame to the mobile station.

15. A method of facilitating power save operation as defined by claim 10, wherein receiving the polling frame comprises receiving a null frame.

16. A method of facilitating power save operation as defined by claim 10, wherein transmitting the aggregate response comprises transmitting a null frame if there is no data in the aggregate buffer.

17. A method of facilitating power save operation as defined by claim 10, further comprising acquiring the WLAN channel in response to receiving the polling frame, performed by contending for the WLAN channel.

18. A method of facilitating power save operation as defined by claim 17, wherein contending for the WLAN channel is performed by carrier sensing.

19. A method of performing power save operation in a wireless local area network (WLAN) having at least one mobile station and at least one access point, the method comprising:

admitting a reserved traffic stream at the access point, including establishing a reserved buffer at the access point for buffering data corresponding to the reserved traffic stream to be transmitted to the mobile station, the reserved buffer and an unreserved buffer forming an aggregate buffer at the access point wherein unreserved data is buffered in the unreserved buffer;

placing a WLAN subsystem of the mobile station in a low power state;

waking up the WLAN subsystem of the mobile station from the low power state in response to the occurrence of a service interval timer event, the service interval timer for timing a service interval, the service interval defining a real time duration of a voice frame;

acquiring a WLAN channel between the mobile station and the access point, performed by the mobile station after waking up the WLAN subsystem from the low power state;

transmitting a polling frame over the WLAN channel from the mobile station upon acquiring the WLAN channel, the polling frame identifying the reserved traffic stream;

acquiring the WLAN channel, performed by the access point after checking the reserved buffer;

transmitting an aggregate response to the mobile station over the WLAN channel, the aggregate response being transmitted by the access point and including data in the aggregate buffer, the transmitting continuing until the aggregate buffer is empty or until a service time period is reached; and

upon receiving the aggregate response at the mobile station, setting the WLAN subsystem into the low power state.

20. A method of performing power save operation as defined by claim 19, further comprising transmitting an acknowledgement frame to the mobile station from the access point over the WLAN channel in response to transmitting the polling frame.

21. A method of performing power save operation as defined by claim 19, further comprising transmitting an acknowledgement frame from the mobile station to the access point over the WLAN channel in response to receiving the aggregate response.

22. A method of performing power save operation as defined by claim 19, wherein transmitting the polling frame comprises transmitting a null frame.

23. A method of performing power save operation as defined by claim 22, wherein transmitting the null frame is performed upon expiration of a window timer initiated upon the beginning of the service interval, the window timer having a duration less than the service interval.

24. A method of performing power save operation as defined by claim 19, wherein transmitting the polling frame comprises transmitting a frame of voice data, the voice data provided to the WLAN subsystem by a voice processing subsystem of the mobile station.