KR20110016374A - Apparatus and method of managing power save mode in wireless lan system - Google Patents

Abstract

PURPOSE: An apparatus and a method of managing power save mode in a wireless LAN(Local Area Network) system are provided to obtain the synchronization of a wakeup schedule between two stations after setting up a TDLS(Tunneled Direct Link Setup) direct link. CONSTITUTION: A processor(720) is connected to a transceiver(710), and sets up a peer station and a TDLS direct link. The processor transfers to the peer station a PSM(Power Save Mode) request frame including a wakeup schedule for power management through an AP(Access Point). The processor receives a PSM response frame through the TDLS direct link from the peer station.

Description

Power saving mode management method and device in a wireless LAN system {APPARATUS AND METHOD OF MANAGING POWER SAVE MODE IN WIRELESS LAN SYSTEM}

The present invention relates to a wireless local area network (WLAN), and more particularly, to a method and apparatus for managing a power saving mode in a WLAN system.

With the development of Wireless Local Access Networks (WLANs), portable terminal users, such as laptop computer users, are able to perform their tasks with increased mobility. For example, a user may take a laptop computer to a meeting to attend a meeting and connect to a local network via a WLAN.

In a system based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, a basic service set (BSS) refers to a set of successfully synchronized stations. The Basic Service Area (BSA) refers to the area that contains the members constituting the BSS. The BSA may vary depending on the propagation characteristics of the wireless medium. BSS can be classified into two basic types: Independent BSS (IBS) and Infrastructure BSS. The former is distributed as forming a self-contained network. A BSS that does not allow access to a Distribution System (DS). The latter includes one or more Access Points (APs) and a distributed system. Generally, the AP includes all of the communication processes between stations. Refers to the BSS used.

According to the IEEE 802.11e standard "Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications / Amendment 8: Medium Access Control (MAC) Quality of Service Enhancements" published November 11, 2005, In addition, the infrastructure BSS (Basic Service Set) does not allow direct transmission of data between non-AP STAs, but requires transmission via the AP for data transmission. . This means that the station cannot directly transmit a frame to another STA in the BSS and passes through the AP for transmission of the frame. Direct link setup (DLS) between non-AP STAs is supported since the IEEE 802.11e standard. Stations can send frames directly to other stations via the DLS direct link.

The station operates in one of two power management modes: active mode (AM) and power save mode (PSM). The active mode refers to the station always in a wakeup state, and the PSM switches the station between the wakeup state and the doze state. The wake-up state is a state in which the station can transmit and receive, and the sleep state is a state in which transmission or reception is impossible or only minimal reception is possible to prevent power consumption. In general, since a station is a portable device belonging to a user, it is essential to support a PSM to efficiently manage power. In the IEEE 802.11e standard, power management is called automatic power save delivery (APSD). APSD has two mechanisms: unscheduled APSD (U-APSD) and scheduled APSD (S-APSD).

Power management is also required on the direct link. According to IEEE 802.11e, after a DLS direct link is set up, a station in an AM or PSM transmits data frames and / or management frames to another station via the DLS direct link.

To set up a DLS direct link, a DLS request frame and a DLS response frame are exchanged over an AP between two non-AP STAs. This means that an AP supporting IEEE 802.11e is required for the DLS direct link to be set up. However, if the WLAN system currently used is based only on IEEE 802.11a / b / g, the AP may not support DLS. Therefore, even a non-AP STA supporting IEEE 802.11e cannot set up a DLS direct link through an AP, and thus cannot utilize a DLS service.

Even if the AP does not support IEEE 802.11e, Tunneled Direct Link Setup (TDLS) has emerged to enable direct link setup between non-AP STAs. In TDLS, a TDLS direct link is set up with an encapsulated data frame.

There is a need for an efficient power management scheme over TDLS direct links.

An object of the present invention is to provide a method and apparatus for managing a power saving mode through a TDLS direct link in a WLAN system.

In one aspect, a power saving mode management method in a WLAN system is provided. The method establishes a Tunneled Direct Link Setup (TDLS) direct link with a peer station and sends a PSM (Power Save Mode) request frame including a wake-up schedule for power management through an access point (AP) to the peer station. And receiving a PSM response frame from the peer station via the TDLS direct link, wherein the wakeup schedule is initiated based on the time at which the PSM response frame is received.

After sending the PSM request frame, a wakeup state may be maintained.

Establishing the TDLS direct link sends a TDLS setup request frame through the AP to the peer station, receives a TDSL setup response frame in response to the TDLS setup request frame via the AP from the peer station, and the And sending a TDSL setup confirmation frame to the peer station in response to a TDSL setup response frame via the AP.

The PSM request frame may be an encapsulated data frame.

The PSM response frame may include a status field indicating acceptance or rejection of the wakeup schedule, and the wakeup schedule may be started when the status field indicates acceptance.

If the status field indicates rejection, the PSM response frame may include an alternative wakeup schedule, and the other wakeup schedule may be initiated based on a time point at which the PSM response frame is received. The wakeup schedule may be initiated after receiving the PSM response frame.

The wakeup schedule may include a wakeup window duration indicating a period during which the station is in a wakeup state and a wakeup interval indicating an interval between two consecutive wakeup windows.

In another aspect, a wireless device for managing a power saving mode in a WLAN system is provided. The wireless device includes a transceiver for transmitting and receiving a frame, and a processor coupled with the transceiver. The processor establishes a Tunneled Direct Link Setup (TDLS) direct link with a peer station and sends a power save mode (PSM) request frame including a wake-up schedule for power management through an access point (AP) to the peer station. And receiving a PSM response frame from the peer station via the TDLS direct link, wherein the wakeup schedule is initiated based on the time at which the PSM response frame is received.

After the TDLS direct link is established, synchronization of the wakeup schedule can be obtained between the two stations. Power can be managed efficiently by clearly defining when entering or waking from sleep mode.

1 illustrates a wireless local area network (WLAN) system in which an embodiment of the present invention is implemented. The WLAN system includes at least one basic service set (BSS). A BSS is a collection of stations (STAs) that have been successfully synchronized to communicate with each other. BSS can be classified into Independent BSS and Infrastructure BSS (Infrastructured) BSS.

BSS1 and BSS2 of FIG. 1 are infrastructure BSSs including AP1 20 and AP2 50, respectively. The BSS1 includes a STA1 10, a STA2 20, and an AP1 20. BSS2 includes STA3 30, STA4 40, and AP2 50. An access point (AP) is an STA that provides a distribution service. The independent BSS operates in ad-hoc mode and does not include an AP. A plurality of infrastructure BSSs are connected by using a distribution system (DS) 80. An extended service set (ESS) is a plurality of BSSs connected through the DS 80. In the same ESS, the non-AP STA may move from BSS to another BSS while performing seamless communication.

A STA is any functional medium that includes a medium access control (MAC) and a wireless-medium physical layer (PHY) interface that meets the IEEE 802.11 standard. The STA may be an AP or a non-AP STA, but refers to a non-AP STA unless otherwise indicated below. The STA may be called other names such as a user equipment (UE), a mobile station (MS), a mobile terminal (MT), a portable device, an interface card, and the like. An AP is a functional medium that provides a connection to a STA via a wireless medium. The AP may be called another name such as a centralized controller, a base station (BS), a scheduler, and the like.

Tunneled Direct Link Setup (TDLS) is a protocol that uses encapsulated frames through an AP to establish a direct link. Encapsulation is delivered in the same manner as a general data frame from an AP's point of view, but it is processed to recognize that the STA is an operation frame between STAs that exchange data frames. Hereinafter, the direct link or TDLS direct link refers to a direct link established through TDLS.

2 shows a process of establishing a direct link through TDLS. This may be referred to section 11.20 of the IEEE 802.11z / D3.0 "Draft Amendment for Direct Link Setup" disclosed in November 2008. IEEE 802.11z is for supporting a direct link between STAs supporting IEEE 802.11e in an AP environment supporting IEEE 802.11a / b / g. The dotted line in the figure means transmission of an encapsulated data frame.

Referring to FIG. 2, in step S210, the STA1 transmits a TDLS setup request frame, which is a TDLS action frame for requesting the establishment of a direct link, to the STA2 through the AP (S210). In step S220, the STA2 receiving the TDLS setup request frame transmits a TDSL setup response frame to the STA1 through the AP in response to the direct setup request (S220). In step S230, STA1 transmits a TDSL Setup Conform frame to the STA2 through the AP to confirm the received TDSL setup response frame (S230). In the TDLS setup procedure, since the TDLS operation frame is encapsulated and transmitted in the form of a data frame without direct involvement of the AP, it is likely to be lost during transmission. Therefore, in the TDLS process, the initiating STA (ie, STA2) transmits the TDLS setup confirmation frame with respect to the TDLS setup response frame from the peer STA (ie, STA2).

The initiating STA, also called a TDLS initiator, is a STA that transmits a TDLS setup request frame. A peer STA is also called a TDLS responder and refers to an STA to which a direct link is established. In the example of FIG. 2, the initiating STA is STA1 and the peer STA is STA2.

The TDLS operation frame is a frame related to the setting, release, etc. of the TDLS, and is encapsulated in the form of a data frame and transmitted to the peer STA through the AP. Encapsulation means that the AP does not know whether it is a TDLS motion frame and delivers it in the same form as a general data frame. Therefore, even if the AP does not support IEEE 802.11e, since the TDLS operation frame can be delivered to the peer STA, the direct link can be established.

3 shows a configuration of a TDLS operation frame. The configuration of the TDLS operation frame is merely an example, and other fields may be added or some fields may be omitted.

The TDLS operation frame 300 includes a MAC header 310, a frame body 320, and a frame check sequence 330. The MAC header 310 includes a frame control field, a duration / ID field, a plurality of address fields (Address1, Address2, Address3, Address4), a sequence control field, and a QoS ( Quality of Service) field may be included. FCS 330 includes a Cyclic Redundancy Check (CRC) across MAC header 310 and frame body 320.

The frame body 320 includes an action field 321, a TDLS type 322, and a body field 325. The action field 321 indicates that the data frame is a TDLS action frame. TDLS type 322 represents the type of TDLS motion frame. The body field 325 includes information according to the type of the TDLS motion frame.

According to section 7.4 of IEEE 802.11z / D3.0, the type of TDLS operation frame is defined as in the following table.

Field value Type 0 TDLS Setup Request One TDLS Setup Response 2 TDLS Setup Confirm 3 TDLS Teardown 4 TDLS Peer Traffic Indication 5 TDLS Channel Switch Request 6 TDLS Channel Switch Response 7 TDLS Peer PSM Request 8 TDLS Peer PSM Response 9 TDLS AP PHY Rate Request 10 TDLS AP PHY Rate Response 11 to 255 Reserved

The TDLS Setup Request Frame, the TDLS Setup Response Frame, and the TDLS Setup Confirmation Frame are used to set up the direct link as described above.

The TDLS Peer PSM Request frame and the TDLS Peer PSM Response frame are used to set the PSM (Power Save Mode).

According to clause 11 of IEEE 802.11z / D3.0, two PSMs are disclosed. One is Peer PSM, and the other is Peer unscheduled-automatic power save delivery (U-APSD). Peer PSM is a power management mechanism based on a periodic wakeup schedule. Peer U-APSD is an unscheduled power management mode. According to the peer U-APSD, two STAs in which a direct link is established are in a doze state. The STA to which the data is to be sent (called a buffer STA) sends a TDLS Peer Traffic Indication frame through the AP to a peer STA in sleep state (called a sleep STA). The TDLS peer traffic indication frame is an encapsulated data frame. The STA that receives the TDLS peer traffic indication frame goes into a wakeup state and receives data through the direct link. According to the peer U-APSD, the buffer STA does not know when the sleep STA will trigger a service period, and it is necessary to wait in the wake-up state after transmitting the TDLS peer traffic indication frame.

4 shows a peer PSM. In step S410, a TDLS direct link is set up between STA1 and STA2. In step S420, the STA1 sends a TDLS peer PSM request frame to the STA2 through the AP. In step S430, the STA2 sends a TDLS peer PSM response frame to the STA1 through the AP.

The TDLS peer PSM request frame and the TDLS peer PSM response frame are delivered through the AP as encapsulated data frames. This means that the STA that transmits the frame may not know when the frame will be transmitted to the peer STA. If the peer STA is in the sleep state, the data frame is not transmitted until the peer STA is in the wake-up state.

For scheduled power management, synchronization is important so that the periods of waking up (and / or entering the sleeping state) between the two STAs coincide. However, it is not easy to obtain synchronization of two STAs through an encapsulated data frame.

Therefore, the following proposes scheduled power management that is easy to synchronize.

5 illustrates a power management method according to an embodiment of the present invention. In step S510, a TDLS direct link is established between STA1 and STA2. The TDLS direct link may be established through the general setup procedure described above.

In step S520, the STA1 sends a PSM request frame to the STA2 through the AP. The PSM request frame is transmitted through the AP as an encapsulated data frame. The PSM request frame includes a wakeup schedule. The wakeup schedule includes a wakeup window duration, a wakeup interval and / or an idle count. The wakeup window section refers to a section in which the corresponding STA is in the wakeup state (or the sleep state). The wakeup window refers to a section in which the STA wakes up. The wakeup interval refers to the time interval between wakeup windows. The idle count is the number of consecutive wakeup windows in which no frame is received from the peer STA before deleting the set wakeup schedule. That is, if the service period does not start during the period indicated by the idle count, the wakeup schedule is deleted. The service interval refers to a continuous time interval in which at least one unicast frame is transmitted between two peer STAs when at least one STAT is in the PSM. The service interval may be initiated during the wake up window.

In step S430, the STA2 sends a PSM response frame to the STA1 in response to the PSM request frame through the TDLS direct link.

6 shows an example of an information element (IE) included in a PSM response frame. This is merely an example, and the order of each IE may be changed, another IE may be added, or some IEs may be omitted. The PSM response frame includes an alternate wakeup schedule 620 and a status field 610. The status field 610 indicates the acceptance or rejection of the wakeup schedule included in the PSM request frame. If the status field 610 indicates refusal, another wakeup schedule 620 suggests a new wakeup schedule to the peer STA. The wakeup window section 621, the wakeup interval 622, and / or the idle count 623 included in another wakeup schedule 620 have the same meaning as the information included in the PSM request frame.

After sending the PSM request frame, STA1 may continue to wake up to receive the PSM response frame via the TDLS direct link. When the STA in the sleep state has data to send to the peer STA, it wakes up in the wake-up state and transmits a PSM request frame and keeps the wake-up state.

PSM response frames are sent over the TDLS direct link. This is to synchronize a wakeup schedule between two STAs. If the PSM response frame is transmitted through the AP in an encapsulated data frame, the PSM response frame may be dropped by the AP. After the STA2 sends the PSM response frame in which the status field is set to accept, a problem may occur in which the STA1 does not follow the wakeup schedule and only the STA2 manages the power saving mode according to the wakeup schedule. In addition, STA2 may not know whether the PSM response frame is transmitted to STA1, and thus it is not easy to synchronize the start time of the wake-up window.

Therefore, the STA2 transmits the PSM response frame to the STA1 through the TDLS direct link, and the wakeup schedule is started based on a time point when the PSM response frame is received (or transmitted). Since the STA1 maintains the wake-up state after sending the PSM request frame, the STA1 can directly receive the PSM response frame. The start point of the first wake window of the wake-up schedule set between the two STAs may be set to a constant offset or target beacon transmission time (TBTT) after the reception time of the PSM response frame. The wakeup schedule between the two STAs may be synchronized based on a certain time point after the reception of the PSM response frame or a frame (eg, a beacon frame) transmitted after the reception of the PSM response frame.

7 illustrates a wireless device in which an embodiment of the present invention is implemented. Wireless device 700 includes a transceiver 710 and a processor 720. The transceiver 710 implements a PHY interface according to the IEEE 802.11 standard and transmits and / or receives frames. The processor 720 is connected with the transceiver 710 to implement a MAC entity, establish a connection with another station (eg, an AP or peer station), and transmit and / or receive a frame. Transmitting or receiving a frame by the processor 720 means transmitting or receiving a frame through the transceiver 710. The transceiver 710 and the processor 720 may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, and / or a data processing device.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

1 shows a WLAN system in which an embodiment of the present invention is implemented.

2 shows a process of establishing a direct link through TDLS.

3 shows a configuration of a TDLS operation frame.

4 shows a peer PSM.

5 illustrates a power management method according to an embodiment of the present invention.

6 shows an example of an IE included in a PSM response frame.

7 illustrates a wireless device in which an embodiment of the present invention is implemented.

Claims (12)

In the WLAN mode management method, Set up a Tunneled Direct Link Setup (TDLS) direct link with the peer station, Sending a power save mode (PSM) request frame including a wake-up schedule for power management to the peer station through an access point (AP), and Receive a PSM response frame from the peer station via the TDLS direct link, The wake up schedule is initiated based on the time point at which the PSM response frame is received. The method of claim 1, wherein the method wakes up after sending the PSM request frame. The method of claim 1, wherein establishing the TDLS direct link Send a TDLS setup request frame to the peer station through the AP, Receive a TDSL setup response frame from the peer station in response to the TDLS setup request frame via the AP, Sending a TDSL setup acknowledgment frame to the peer station in response to a TDSL setup response frame via the AP. The method of claim 1, wherein the PSM request frame is an encapsulated data frame. 2. The method of claim 1 wherein the PSM response frame includes a status field indicating accept or reject of the wakeup schedule, and the wakeup schedule is initiated when the status field indicates accept. 6. The method of claim 5, wherein if the status field indicates refusal, the PSM response frame includes an alternative wakeup schedule, wherein the other wakeup schedule is initiated based on the time at which the PSM response frame is received. . 6. The method of claim 5, wherein the wake up schedule is initiated after receiving the PSM response frame. 2. The method of claim 1, wherein the wakeup schedule comprises a wakeup window duration indicating a period of time during which the station is in a wakeup state and a wakeup interval indicating an interval between two consecutive wakeup windows. In a wireless device for managing a power saving mode in a WLAN system, A transceiver for transmitting and receiving frames; And And a processor coupled to the transceiver, wherein the processor Set up a Tunneled Direct Link Setup (TDLS) direct link with the peer station, Sending a power save mode (PSM) request frame including a wake-up schedule for power management to the peer station through an access point (AP), and Receive a PSM response frame from the peer station via the TDLS direct link, The wake up schedule is initiated based on the time point at which the PSM response frame is received. 10. The method of claim 9, wherein establishing the TDLS direct link Send a TDLS setup request frame to the peer station through the AP, Receive a TDSL setup response frame from the peer station in response to the TDLS setup request frame via the AP, Sending a TDSL setup acknowledgment frame in response to a TDSL setup response frame through the AP to the peer station. 10. The wireless device of claim 9, wherein the PSM response frame includes a status field indicating acceptance or rejection of the wakeup schedule, and the wakeup schedule is initiated when the status field indicates acceptance. 12. The method of claim 11, wherein if the status field indicates rejection, the PSM response frame includes an alternative wakeup schedule, and the other wakeup schedule is initiated based on the time at which the PSM response frame is received. Device.

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