Delivery of buffered frames to power saving stations in wireless local area networks

A wireless local area network (WLAN) typically includes an access point (AP) and one or more stations. Each station sends a radio signal over the AP to another station in the local area network and receives the radio signal from it, a notebook computer, a personal digital assistant (PDA), and a radio voice over. -Can be a device such as an Internet Protocol (VoIP) phone.

APs and stations transmit data on shared communication channels in units called frames. Frames sent from the station to the AP are called uplink frames, and frames sent from the AP to the station are called downlink frames. In situations where two or more stations (or APs and stations) transmit frames at the same time, one or more of the frames can be destroyed, called a collision. As a result, WLANs generally have one or more protocols that allow a station or AP to gain dedicated access to a shared communication channel for a given time interval to send its frames without collisions. Is adopted. Some wireless network protocols (such as the Institute of Electrical and Electronics Engineers [IEEE] 802.11) are specially referred to as beacons in which the AP can be heard by stations in the BSA (Basic Service Area), which is the area covered by the AP. To be able to broadcast various frames periodically. Beacons allow stations to synchronize their local clock and signal information (eg, number of channels, frequency hopping patterns, dwell time, etc.), time stamps, etc., which allow the station to establish and maintain communication regularly. It contains a variety of information that makes it possible.

If the station is not transmitting or receiving, it can extend its battery life by turning off its radio. If the station turns off its radio, the station is said to enter a "doze" state. A station wakes up from a nap state by turning on its radio to enter an "awaken" state. While in a nap, the station is unable to send or receive signals and is said to be asleep. Stations that save battery life by switching between warning and nap states are said to be in power saving (PS) mode, and stations that employ PS mode are called power saving stations.

If the station is up while the station is dormant, the AP buffers the downlink frame for the station for final delivery.

One method of receiving buffer frames is described in the IEEE 802.11-199 standard and is referred to herein as a "legacy" power saving method. In this method, the AP periodically includes a traffic instruction map (TIM) in the beacon to identify which station in power saving mode has a downlink frame waiting in the AP's buffer for transmission. ..

According to the legacy power saving method, the nap station wakes up to receive the beacon and check the TIM. If TIM indicates that there are buffered frames for that station, the station sends a PS pole to request the delivery of buffered frames. To use the PS pole, the station listens to the TIM on the beacon to determine if the AP has a buffer frame for the station. If there is a buffer frame for the station in the AP, the station sends a PS pole to the AP to inform the AP that the station is up and waiting to receive the buffer frame. The AP sends a buffer frame to the station. If the frame has a "more data" bit set to 1, indicating that there are more buffer frames for the station, the station sends another PS pole to get another buffer frame. .. This is repeated until the AP no longer has more data for the station.

If TIM indicates that there are no buffer downlink frames for the station, the station returns to a nap. In addition, the nap station buffers the uplink frames generated by the application layer and sends one or more of the buffered uplink frames at startup.

Another strategy for delivering AP buffer packets to the appropriate stations is called Automatic Power Saving Delivery (APSD), and the delivery of downlink buffer frames is the frames sent when the PS station is up. Happens without the need for the PS pole to indicate that it is ready to receive. There are two types of APSD: (i) scheduled APSD and (ii) unscheduled APSD. The two APSD variants differ with respect to the start of a "service period", which is the time interval in which the PS station is presumed to be up and can receive frames transmitted by the AP. With a scheduled APSD, the service period starts automatically, that is, without a special signal frame notifying the AP that the station is up and ready to receive a frame. In unscheduled APSD, the transmission of uplink frames is sufficient to signal the start of the service period, that is, the station is up and ready to receive the transmitted frames. The unscheduled service period begins when the AP receives quality of service (QoS) data / empty frames from the station. The station can choose to limit the access category (AC) of the frames that can start the service period. The AC of the frame that can start the service period is specified by the station via a signal such as APSD TSPEC.

Another feature of APSD is the termination of the service period, the time interval that the PS station must remain up. Unlike legacy power saving, where the PS station can sleep after receiving a single frame from the AP, APSD requires the PS station to stay up to receive some buffer frames, Dormant only if it is notified by the AP. The AP sets the EOPS (end of service period) bit to 1 in the last frame it sends to inform the station that it will not transmit any more frames downlink until the next service period.

<p> Conventional mechanisms, such as those described above, have various drawbacks. One such drawback is that in the QoS protocol 802.11e, there are insufficient fields to indicate the priority of buffered frames. Some devices with urgent tasks to perform may want to know this priority over the proper schedule of buffer frame searches for other tasks.</p><p> According to the unscheduled APSD distribution mechanism specified in IEEE802.11e Draft 8.0, the AP sends all buffer frames during the service period before the power saving station can sleep. If the more data bit is set to 0, it indicates that all frames have been transmitted. This can cause at least two problems. One problem is priority reversal. If the AP must send the contents of the APSD buffer to the power saving station before sending the frame to the other station, the low priority frame for the power saving station is before the other station and the higher priority frame. Will be sent to.</p><p> Another problem associated with the unscheduled APSD method proposed to date can occur when an AP interferes with sending to a power saving station in order to send a higher priority frame to another station. The battery is exhausted. It may keep the station running for too long.</p><p> Traditional legacy power saving is inadequate. PS poles are inadequate to use when long packet bursts are buffered as PS poles are required for every frame. The excitation and return of the power saving mode is inadequate for the frames arriving individually, as it contains two extra frames for each buffer frame retrieved. Since TIM cannot tell how much traffic is buffered, it cannot tell you the correct legacy option to use.</p><p> You can add a priority-specific TIM to the beacon and extend the QoS control field to make room for the priority-specific more data bits to provide priority for buffer traffic. This, however, seems impractical.</p><p> In addition, systems that employ the unscheduled APSD method proposed to date are aperiodic bursts because the definition of TIM is limited to a subset of buffer frames whose delivery relies on legacy power saving mechanisms. Do not search for traffic efficiently. Frames that should be searched via unscheduled APSD will not be included in the TIM.</p><p> Embodiments of the present invention significantly overcome such drawbacks and provide mechanisms and techniques for transmitting buffer frame priorities to power saving stations in WLANs. Embodiments of the present invention indicate the priority and queue size of buffer frames. Knowing the buffer frame priority allows the station to decide whether to send a frame to search for buffer frames waiting in the AP, or to perform other time-constrained functions. .. By knowing the queue size, the station can decide which power saving option should be tracked, i.e., the station can use the PS pole or decide to excite or restore the power saving mode. Another aspect of the invention disclosed herein relates to the meaning of TIM and more data bits. The TIM and more data bits must reflect all buffered traffic, not just the traffic that should be retrieved by legacy power saving methods. Therefore, the unscheduled APSD method has been enhanced to handle both periodic and aperiodic traffic. Another aspect of the invention is to allow the AP to determine the end of the service period when deemed appropriate. It is achieved by the EOSP bit and the generalized TIM and more data bit definitions, and if the EOSP bit is set by the AP before the buffer is empty, it notifies the station of the existence of a frame that remains buffered. .. The traditional specification of the unscheduled APSD method causes a priority reversal (or causes the station to consume more power) and cannot be used by many applications (ie, aperiodic traffic). These applications must use legacy power savings, which are less efficient. Yet another aspect of the invention is that a frame of any access category (AC) can act as a trigger frame. The frame is released from it The AC buffer created is not limited to be the same as the AC of the trigger frame. APs generally free frames from the highest priority AC containing buffered frames. Another aspect of the invention disclosed herein relates to the ability of a station to mark an uplink frame that limits the length of the service period and triggers the start of the service period for a power saving station.</p>

<p> In certain embodiments of a method for transmitting buffer frame priority to a power saving station in a WLAN that includes an AP and at least one power saving station, the method comprises at least one of the legacy buffer and APSD buffer in the AP to the station. Includes the step of instructing the station that there is at least one buffer frame in one. The method further comprises receiving an instruction from the station that the station is ready to receive at least one of the buffer frames for the station. Then select a buffer to release at least one buffer frame to the station. The method also includes determining some frames to be transmitted from the selected buffer and transmitting some of the frames from the selected buffer to the station. Another aspect of the invention disclosed herein relates to the ability of a station to mark an uplink frame that limits the length of the service period and triggers the start of the service period for a power saving station.</p><p> In certain embodiments of a method for transmitting buffer frame priority to a power saving station in a WLAN that includes an AP and at least one power saving station, the method comprises at least one of the legacy buffer and APSD buffer in the AP to the station. Includes the step of instructing the station that there is at least one buffer frame in one. The method further comprises receiving an instruction from the station that the station is ready to receive at least one of the buffer frames for the station. Then select a buffer to release at least one buffer frame to the station. The method also includes determining some frames to be transmitted from the selected buffer and transmitting some of the frames from the selected buffer to the station.</p><p> Another embodiment of the invention is an access point (AP) comprising a processor, a memory communicating with the processor, a receiver communicating with the processor and the shared communication channel, and a transmitter communicating with the processor and the shared communication channel. including. The AP further includes at least one legacy buffer and at least one APSD buffer that communicates with the transmitter, and the AP has at least one buffer frame in at least one of the legacy buffers and APSD buffers in the AP for the station. To the station and release at least one buffer frame to the station depending on the process of receiving the instruction from the station to the receiver that the station is ready to receive at least one buffer frame for the station. A buffer is selected, some frames to be transmitted from the selected buffer are determined, and some frames are transmitted from the buffer to the station by the transmitter.</p><p> Yet other embodiments include computerized devices configured to handle all the method operations disclosed in the present invention as embodiments of the present invention. In such embodiments, the computerized device includes a communication interface in a memory system, a processor, and an interconnect mechanism connecting these components. When a memory system is performed on a processor (eg, when it is performed), it is described herein in a computerized device to perform all of the methods and operations described herein as embodiments of the present invention. Encoded in a process that provides the mechanisms and techniques for transmitting buffer frame priorities to the power saving stations in the WLAN described herein, which operate as described. Accordingly, a computerized device that performs or is programmed to perform the processes described herein is an embodiment of the present invention.</p><p> Other configurations of embodiments of the invention disclosed herein include software programs for performing method embodiment steps and operations summarized above and disclosed in detail below. More specifically, computer program products, when performed on computerized devices, are related operations that provide mechanisms and techniques for transmitting buffer frame priorities to power saving stations in WLANs as described herein. Is an embodiment having a computer readable medium comprising encoded computer program logic on it. Computer program logic, when executed on at least one processor with a computing system, causes the processor to perform the operations (eg, methods) described herein as embodiments of the present invention. Such configurations of the present invention generally include computer-readable media such as optical media (eg, CD-ROM), floppy®, hard disks, or firmware in one or more ROMs, RAMs, or PROM chips. Software configured or encoded on top of other media such as microcode, as code and / or other data structures, or as a purpose-built integrated circuit (ASIC), or one or more modules, shared libraries, etc. Provided as a downloadable software image in. Software or firmware or other such configuration may be installed on the computerized device to allow one or more processors in the computerized device to perform the techniques described herein as embodiments of the present invention. it can. Software processes that operate in a collection of computerized devices, such as in a group of data communication devices or other entities, can also provide the systems of the invention. The system of the present invention can be distributed among many software processes on several data communication devices, or all processes are dedicated computers.</p><p> It should be understood that embodiments of the present invention can be implemented as software programs, as software and hardware, or as hardware and / or circuits only, such as within a data communication device, strictly speaking. Features of the invention can be incorporated into data communication devices and / or software systems for such devices, such as those manufactured by Avaya, Inc., Lincroft, NJ, as described herein. ..</p><p> The above and other objects, features and advantages of the present invention are derived from the following more detailed description of preferred embodiments of the present invention, as shown in the accompanying drawings in which the same reference numerals refer to the same components throughout various figures. It will be clear. The drawings are not necessarily to a constant scale and instead emphasize the explanation of the principles of the invention.</p>

With reference to FIG. 1, a block diagram of the WLAN environment 10 according to the present invention is shown. Environment 10 includes AP12 and multiple stations 14a-14d. Although four stations are shown, it should be understood that any number of stations can be used. Stations 14a-14d transmit frames to AP12 over the wireless communication channel. Stations 14a-14d can also receive frames from the AP12 over the wireless communication channel. The station can also enter power saving (PS) mode and send and receive frames while in power saving mode.

AP12 receives frames from one or more stations 14a-14d over the radio communication channel. The AP12 can also send frames to one or more stations 14a-14d over the radio communication channel. AP12 can also buffer downlink frames for stations in nap and deliver buffered downlink frames to the appropriate stations when the station wakes up from nap.

A station can extend its battery life by turning off its radio when it is not transmitting or receiving. The station can be in one of two power management modes, active mode and PS mode. As mentioned above, frames addressed to stations in PS mode can be buffered in the AP.

A station in PS mode can choose one of two ways to deliver that frame buffered in the AP while in PS mode. One way is to use a PS pole. On the PS pole, the station listens to the TIM to determine if the AP has a buffer frame for the station. The station sends a PS pole to the AP, telling the AP that the station is up. The AP sends a buffer frame to the station. If the frame has a "more data" bit set indicating that there are more buffer frames for the station, the station sends another PS pole to get another buffer frame. This is repeated until the AP no longer has a frame from the station.

Another method is to use Automatic Power Saving Delivery (APSD). To use APSD, the station presents a Traffic Specification (TSPEC) request with the field APSD field set to indicate that APSD should be used (for example, set the APSD field to 1). TSPEC contains data traffic estimates and related requirements. All buffer frames associated with the authorization APSD TSPEC are sent during the service period. There are two types of service periods possible under APSD, unscheduled and scheduled, so there are two variants of APSD: unscheduled APSD and scheduled APSD. Unscheduled APSDs can only be used for conflict-based access, while scheduled APSDs can be used for both conflict-based access and pole access. APSD can be efficiently combined with traditional (legacy) power management features to adapt to mixed traffic.

According to the present invention, the buffer frame priority and queue size are indicated to the station. By knowing the buffer frame priority, the station can decide whether to send a frame to find the buffer frame waiting in the AP, or perform other time-constrained functions. it can. Knowing the queue size allows the station to decide which power saving options should be tracked.

It should be noted that in the environment containing the present invention, TIM is given an extended definition. TIM contains traffic to be searched by legacy power saving methods and unscheduled APSD. The TIM and more data bits indicate whether traffic is buffered in the AP. The TIM and more data bits reflect all buffered traffic (periodic and aperiodic), so stations with aperiodic traffic can use the unscheduled APSD to retrieve the traffic. Therefore, unscheduled power saving methods have been enhanced to handle both periodic and aperiodic traffic.

The AP decides to end the service period when it seems appropriate. The AP can consider buffer frame priorities, the amount of buffer frames, and other criteria in determining when the service period should end. It is achieved by the EOSP bit and the generalized TIM and more data bit definitions, and if the EOSP bit is set by the AP before the AC buffer is empty, the presence of the buffered frame will be stationed. Notice.

The unscheduled service period begins when the AP receives the appropriate AC-associated data / empty frame from the station. If authorization control is mandatory for the authorization TSPEC traffic category, the service period ends after the AP is destined for the APSD station and attempts to send all frames associated with the authorization APSD TSPEC. Otherwise, the service period ends at the discretion of the AP, but not before the AP attempts to send at least one frame addressed to the APSD station.

Unscheduled APSD is more efficient than legacy power saving for all traffic types because a single trigger frame can search many frames. The downlink frame is released from the trigger PS buffer by the trigger frame. Trigger frames are defined as QoS data or QoS empty frames that are uplinked by a PS mode station whose user priority (UP) map maps to a trigger-enabled AC. Transmission of trigger frames is not implicitly permitted by downlink flow authorization. If the trigger frame maps to an AC with ACM = 1, the station must establish a proper uplink flow before sending the trigger. The combination of transmission station and UP uniquely identifies the trigger PS buffer, and the trigger frame releases all frames from that buffer.

The released frames are delivered during the trigger service period. The trigger service period begins after the AP sees the trigger frame sent by the station. The AC frame can act as a trigger frame. The AC buffer from which the frame is released is not limited to be the same as the AC of the trigger frame. APs generally free frames from the highest priority AC containing buffered frames.

Frames released from the trigger PS buffer are delivered using the corresponding AC access parameters. The AP uses the EOS P bit carried in the QoS control field to indicate the end of the trigger service period.

It should be clear that for a particular station, the APSD buffer, trigger frame, and trigger service period are all per AC. Therefore, if a non-AP station establishes a flow that results in one or more trigger-enabled ACs, the station initiates a separate trigger service period for each such AC to retrieve all buffer frames. There must be. Non-AP stations must remain up as long as at least one trigger service period is still in progress. If there is at least one authorization downlink or bidirectional TSPEC with APSD = 1 that maps to AC, then that AC is considered trigger-aware for a particular station. The downlink unicast QoS data frame associated with the trigger-enabled AC is temporarily held in the AC's trigger PS buffer.

In order for the station to receive call signals and other control / maintenance frames arriving in the APSD buffer, the TIM and more data bits indicate the presence of these frames in the AP. If there is a single TIM, the AC buffer from which the frame is released is not limited to be the same as the AC of the trigger frame. The station cannot tell AC the buffer frame from TIM and therefore may not be able to provide the same AC trigger frame as the buffer frame. As long as a frame is released from a single trigger buffer per trigger frame, the AP determines the buffer for releasing the frame. The AP preferably releases the frame from the highest priority AC containing the buffer frame. The station must search all its buffer frames, but using a single TIM (and a single more data bit) creates ambiguity about the AC of the buffer frames, which causes ambiguity. Problems may occur that require the device to perform other urgent tasks. Knowledge of buffer traffic priority allows the station to immediately search for top priority frames, while lower priority frames are made to wait.

Using more TIMs will increase channel overhead, while using longer QoS control fields will increase frame size, neither of which is desirable. An alternative is to add some signal information to an existing field that is currently transmitted but reversed. The bits in the QoS control field of the DL frame that correspond to the queue size on the uplink (UL) frame can be used for this signal. These bits, called the Residual Buffer (RB) bits, indicate whether there is any data left in the buffer from which the frame was released. RB can be binary or indicate the queue size. The station watching the TIM instruction either waits for the next trigger (UL voice) before responding to the TIM instruction, or sends a trigger frame. The AP will respond to the highest priority frames buffered in the station. With RB instructions, the station has enough information to do what it needs to do.

Next, with reference to FIG. 2, a block diagram showing the main components of a particular embodiment of the AP is shown. The access point 12 includes a processor 20, a memory 22, a receiver 24, and a transmitter 26 that are interconnected as shown. Transmitter 26 includes legacy buffer 28 and APSD buffer 30.

The processor 20 is a general-purpose processor capable of executing instructions stored in the memory 22, reading data from the memory 22, writing data to the memory 22, and executing various processes. The memory 22 can store programs and data used by the processor 22, and can be any combination of random access memory (RAM), flash memory, disk drive, and the like.

The receiver 24 is a circuit capable of receiving frames from the shared communication channel 32 and transferring the received frames to the processor 20. The transmitter 26 is a circuit capable of receiving a frame from the processor 20 and transmitting the frame on the shared communication channel 32.

In certain embodiments of AP12, the AP comprises a processor, a memory that communicates with the processor, a receiver that communicates with the processor and shared communication channels, and a transmitter that communicates with the processor and shared communication channels. The transmitter includes at least one legacy buffer 28 and at least one APSD buffer 30.

In operation, the AP instructs the station that there is at least one buffer frame in at least one of the legacy buffers and automatic power saving distribution (APSD) buffers in the AP for the station. Instructions from the AP to the station can be made by transmitting a TIM in the beacon or by transmitting a more data bit instruction in a downlink frame. If the more data bit is transmitted in a downlink frame, the AP can also send a residual buffer (RB) bit. The combination of more data bits and RB bits is used to determine the state of residual buffer frames in the AP.

Table 1 below lists specific embodiments of the interpretation of the more data bits and RB bits.<tables num="1"><img file="JP4360552B2_D0001.tif" /></tables>

As shown in Table 1, when the more data bit is set to zero, there are no more frames left buffered in the AP. If the more data bit is set to 1 and the RB bit is set to zero, then there are frames with lower priority than the received frames that remain buffered in the AP. If the more data bit is set to 1 and the RB bit is set to 1, then there are frames with the same priority as the received frames that remain buffered in the AP.

The AP receives the instruction at the receiver where the station is activated and ready to receive at least one of the buffer frames for the station. This can be achieved, for example, by the AP receiving a trigger frame. The trigger frame can be any uplink frame from the station, or an uplink frame from a station with a special marker. An example of a marker for a trigger frame would be a nonzero maximum SP length. The maximum SP length is a field in the uplink frames sent by the power saving station that indicates the maximum number of frames buffered for the station in the AP to send during the next service period. The ability to limit the maximum length of service period allows a station to (a) limit the length of the time interval it must activate to receive buffered frames in the AP, and (b) It receives a frame from the AP and allows the uplink frame to be sent without having to stay up until it can sleep again. The AP then selects a buffer to free at least one buffer frame for the station. The AP selects the buffer that has the highest priority and contains the buffer frame. Some frames are determined to be transmitted from the selected buffer, and some frames are transmitted from the buffer selected by the transmitter to the station. Some frames are sent using unscheduled APSD for aperiodic traffic. AP is AC authorized for traffic APSD If you have TSPEC, do unscheduled APSD for aperiodic traffic. If a single TIM is present, the AP sends frames from a buffer associated with an AC that is different from the AC associated with the trigger frame. As long as a frame is released from a single trigger buffer per trigger frame, the AP chooses a buffer for releasing frames.

A flow chart of the method disclosed here is shown in Figure 3. Rectangular elements are referred to herein as "processing blocks" and represent computer software instructions or instruction groups. Alternatively, the processing and decision block represents a process performed by a functionally equivalent circuit such as a digital signal processor circuit or an application specific integrated circuit (ASIC). The flow diagram does not show the syntax of a particular programming language. Rather, the flow diagram shows the functional information required by one of ordinary skill in the art to create a circuit or generate computer software to perform the processing required by the present invention. It should be noted that many routine program elements such as loop and variable initialization and the use of temporary variables are not shown. Unless otherwise indicated herein, one of ordinary skill in the art will appreciate that the particular sequence of steps described is only exemplary and can be modified without departing from the spirit of the invention. Thus, unless otherwise stated, the steps described below are in no particular order, meaning that, where possible, the steps can be performed in any convenient or desirable order.

Embodiments of the invention can be in computer-readable media such as floppy disks, hard disks, or optical media, or in memory type systems such as firmware, read-only memory (ROM), or. Includes encoded applications (ie, unexecuted or non-executable logical instructions and / or data) as executable code in memory systems (eg, in random access memory or RAM), as in this example. Should be understood.

Next, referring to FIG. 3, a method 100 for transmitting buffer frame priority to a power saving station in a WLAN including an AP and at least one power saving station is shown. The method starts at processing block 102 and indicates the existence of at least one legacy buffer in the AP and at least one buffer frame in the APSD buffer for the station.

In processing block 104, instructions are given by at least one step of transmitting a TIM and a step of transmitting more data bits in a downlink frame. In processing block 106, the step of transmitting more data bits further includes the step of transmitting a residual buffer (RB) bit having more data bits. The more data bits and RB bits are analyzed as shown in processing block 108. If the more data bit is not set, there are no more frames left buffered in the AP. If the RB bit is not set and the more data bit is set, then there are frames with lower priority than the received frames that remain buffered in the AP. If the RB bit and the more data bit are set, there are frames with the same priority as the received frames that remain buffered in the AP.

At processing block 110, the station receives an instruction from the station notifying the AP that it is ready to receive at least one of the buffer frames for the station. I described processing block 112 sea urchin, the step of receiving an indication comprises the step of receiving the trigger frame.

In processing block 114, select a buffer to release at least one buffer frame to the station. As shown in processing block 116, the step of selecting a buffer includes the step of selecting a buffer having the highest priority and containing a buffer frame.

In processing block 118, some frames to be transmitted from the selected buffer are determined. This decision can take into account buffer frame priority, some buffer frames, and other criteria.

As shown in processing block 120, some frames determined in processing block 118 are transmitted from the buffer to the station. As described in processing block 122, transmission is performed using an unscheduled APSD for aperiodic traffic. Further, as shown in processing block 124, the use of unscheduled APSD for aperiodic traffic is done when the AC of the traffic has an authorized APSD TSPEC. In addition, as described in processing block 126, if there is a single TIM, the frame is sent from a buffer associated with an AC that is different from the AC associated with the trigger frame. In processing block 128, the AP determines the buffer for frame release as long as the frame is released from a single trigger buffer per trigger frame.

Although preferred embodiments of the present invention have been described above, it will be apparent to those skilled in the art that other embodiments incorporating these concepts can be used. In addition, the software included as part of the present invention can be implemented in computer program products, including computer-enabled media. For example, such computer-enabled media includes hard drive devices, CD-ROMs, DVD-ROMs, or readable memory devices such as computer diskettes that store computer-enabled program code segments. be able to. Computer-readable media can also include either optical, wired, or wireless communication links with program code segments carried on it as digital or analog signals. Therefore, the invention should not be limited to the embodiments described, but only to the spirit and scope of the appended claims.

<figref num="1">It is a block diagram of a specific embodiment of a wireless local area network environment according to the aspect of this invention.</figref><figref num="2">FIG. 6 is a block diagram of the main components of an access point according to an exemplary embodiment of the present invention.</figref><figref num="3A">It is a flow chart of a specific embodiment of the method for transmitting the priority of a buffer frame to a power saving station in a wireless local area network according to the aspect of the present invention.</figref><figref num="3B">It is a flow chart of a specific embodiment of the method for transmitting the priority of a buffer frame to a power saving station in a wireless local area network according to the aspect of the present invention.</figref>