METHOD BY WHICH STATIONS OPERATING IN POWER SAVE MODE IN WIRELESS LAN SYSTEMS TRANSMIT AND RECEIVE FRAMES, AND APPARATUS FOR SUPPORTING SAME

• US 20150023236A1
• Filed: 01/30/2014
• Published: 01/22/2015
• Est. Priority Date: 02/10/2012
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Choi, Jinsoo, Han, Seunghee, Kwak, Jinsam, Seok, Yongho, Kim, Jeongki
• Granted Patent: US 9,491,700 B2
• Time in Patent Office: Days
• US Class Current: 370/311
• CPC Class Codes: H04W 52/0225 using monitoring of external events, e.g. the presence of a signal
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention relates to a method by which a station (STA) which operates in power save mode in a wireless LAN system transmits and receives frames. The method includes the steps of: obtaining a channel access authority on the basis of at least one slot time, wherein each slot time is the unit time when a channel is maintained in an idle state for a channel access by the STA; transmitting a power save (PS) poll frame requesting the transmission of a buffered frame to an access point (AP); and receiving a response frame from the AP in response to the PS poll frame. The length of each slot time is set to be longer than the transmission time of the PS poll frame.

Claims

1. A method of transmitting and receiving a frame performed by a station (STA) that operates in a power save mode in a wireless local area network (WLAN) system, comprising:

acquiring a channel access authority based on at least one slot time, each of the slot time being a unit time when a channel is kept in an idle state for a channel access of the STA;

transmitting a PS (power save)-poll frame requesting a transmission of a buffered frame to an access point (AP); and

receiving a response frame from the AP in response to the PS-poll frame,

wherein a length of the each slot time is set to be larger than transmission time of the PS-poll frame.

2. The method of claim 1, further comprising setting a back-off timer which is a number of the at least one slot time.

3. The method of claim 2, further comprising:

receiving a traffic indication map (TIM) element,

wherein the TIM element includes a bitmap sequence, and

a specific bit of the bitmap sequence indicates whether the buffered frame for the STA exists.

4. The method of claim 3, wherein a value of the back-off timer is determined based on an order of the specific bit in the bitmap sequence.

5. The method of claim 3, wherein a value of the back-off timer is determined based on an order of the specific bit in the bitmap sequence and a time when the STA sets the back-off timer.

6. The method of claim 3, wherein the value of the back-off timer is determined by an order of the specific bit among at least one bit indicating that a buffered frame for a specific STA in the bitmap sequence exists.

7. The method of claim 3, wherein the value of the back-off timer is determined by an order of the specific bit among at least one bit indicating that a buffered frame for a specific STA in the bitmap sequence exists and timing information for setting the back-off timer.

8. The method of claim 1, wherein the response frame is a buffered frame.

9. The method of claim 1, wherein the response frame is an acknowledgement (ACK) frame.

10. A wireless device that operates in a power save mode in a wireless local area network (WLAN) system, the apparatus comprising:

a transceiver configured to transmit and receive a radio signal; and

a processor operatively coupled with the transceiver configured to;

acquire a channel access authority based on at least one slot time, each slot time being a unit time when a channel is kept in an idle state for a channel access of the STA,

transmit a PS (power save) poll frame requesting a transmission of a buffered frame to an access point (AP), and

receive a response frame from the AP in response to the PS-poll frame,

wherein a length of the each slot time is set to be larger than transmission time of the PS-poll frame.

11. The wireless device of claim 10,

wherein the processor is further configured to set a back-off timer which is a number of the at least one slot time.

12. The wireless device of claim 11,

wherein the processor further configured to receive a traffic indication map (TIM) element,

wherein the TIM element includes a bitmap sequence, and

a specific bit of the bitmap sequence indicates whether the buffered frame for the wireless device exists.

13. The wireless device of claim 12, wherein a value of the back-off timer is determined based on an order of the specific bit in the bitmap sequence.

14. The wireless device of claim 12, wherein a value of the back-off timer is determined based on an order of the specific bit in the bitmap sequence and a time when the wireless device sets the back-off timer.

15. The wireless device of claim 12, wherein the value of the back-off timer is determined by an order of the specific bit among at least one bit indicating that a buffered frame for at least one wireless device in the bitmap sequence exists.

16. The wireless device of claim 12, wherein the value of the back-off timer is determined by an order of the specific bit among at least one bit indicating that a buffered frame for at least one wireless device in the bitmap sequence exists and timing information for setting the back-off timer.

17. The apparatus of claim 10, wherein the response frame is a buffered frame.

18. The apparatus of claim 10, wherein the response frame is an acknowledgement (ACK) frame.