Communication method of a transmission apparatus and a reception apparatus

<u>BACKGROUND</u>

1. Field

0001The following description relates to a communication method and a transmission apparatus and a reception apparatus.

2. Description of Related Art

0002Mobile terminals such as smart phones allow a user to simultaneously perform a variety of functions, for example, making a call, playing a motion picture, playing back a music file, viewing a digital multimedia broadcasting (DMB), a digital camera function, Bluetooth, wireless Internet access, and the like, using a single device.

0003In addition, as the data rate of a mobile communication networks, Bluetooth, wireless Internet, and the like, increases, power consumption of a terminal may also increase. Accordingly, there is a desire for a communication method that may employ a high capacity battery for a terminal, and may decrease power consumption by the terminal.

0004A prior art example for a WLAN communication network which employs the concept of transmission opportuniy in order to save power is disclosed in <patcit id="pcit0001" dnum="US2008095091A1"><text>US 2008/095091 A1</text></patcit>.

<u>SUMMARY</u>

0005In one general aspect, there is provided a communication method of a reception apparatus operating in an active mode, the method including setting a power management mode to a power saving mode during a transmission opportunity (TXOP), receiving information transmitted from a transmitting apparatus, and determining an operation state of the reception apparatus by determining whether a predetermined criterion is satisfied based on the information received from the transmission apparatus, wherein streams corresponding to one or more reception apparatuses are simultaneously transmitted from the transmission apparatus during the TXOP.

0006The determining may comprises changing the operation state of the reception apparatus from an awake state to a sleep state, in response to the predetermined criterion being satisfied based on information transmitted from the transmission apparatus.

0007The information transmitted from the transmission apparatus may comprise at least one of a group identifier (ID) of a group comprising the reception apparatus, information about whether there is a stream of data to be transmitted to the reception apparatus from the transmission apparatus during the TXOP, and information indicating whether there is an additional stream to be transmitted to the reception apparatus.

0008The predetermined criterion may comprise a first criterion, a second criterion, and a third criterion, if the reception apparatus is not included in the group of the group ID, the first criterion may be satisfied, if the reception apparatus is included in the group of the group ID, and there is no stream of data to be transmitted to the reception apparatus from the transmission apparatus during the TXOP, the second criterion may be satisfied, and if an indicator indicating that there is no additional stream to be transmitted to the reception apparatus during the TXOP is received, the third criterion may be satisfied.

0009The method may further comprise selectively determining whether to change the operation state of the reception apparatus based on the first criterion and the second criterion, using an enabling bit included in each of frames transmitted from the transmission apparatus.

0010The method may further comprise transmitting, to the transmission apparatus, a frame in which the power management mode is set to the power saving mode, in response to the reception apparatus desiring to operate in the power saving mode, and receiving, from the transmission apparatus, an acknowledgement (ACK) as a response to the frame in which the power management mode is set to the power saving mode, wherein the setting comprises setting the power management mode to the power saving mode in the TXOP duration in response to the received ACK.

0011The method may further comprise receiving, from the transmission apparatus, a TXOP setting frame comprising information associated with the TXOP duration, wherein the TXOP setting frame is generated to be decodable by both a reception apparatus having set the power management mode to the power saving mode, and a reception apparatus having not set the power management mode to the power saving mode.

0012The method may further comprise determining whether the reception apparatus is capable of receiving the stream based on the TXOP setting frame, and transmitting a response frame with respect to the TXOP setting frame based on the determination result.

0013The method may further comprise maintaining the operation state of the reception apparatus to be in a sleep state for the remainder of the TXOP duration after terminating receiving of a corresponding stream based on the indicator, or after transmitting a block ACK with respect to the corresponding stream.

0014In another aspect, there is provided a communication method of a transmission apparatus, the method including obtaining a transmission opportunity (TXOP) with respect to a channel, maintaining streams corresponding to reception apparatuses having an active mode as a power management mode, transmitting information used to determine an operation state of each of the reception apparatuses, and simultaneously transmitting the streams to at least one of the reception apparatuses during the TXOP.

0015The information used to determine the operation state of each of the reception apparatuses may comprise at least one of a group identifier (ID) of a group comprising each of the reception apparatuses, information about whether there is a stream of data to be transmitted to the respective reception apparatuses from the transmission apparatus during the TXOP, and information indicating whether there is an additional stream to be transmitted to the respective reception apparatuses.

0016The method may further comprise receiving a frame in which the power management frame is set to the power saving mode, from a reception apparatus desiring to operate in the power saving mode from among the reception apparatuses that have the active mode as the power management mode, and transmitting, to the reception apparatus, an acknowledgement (ACK) with respect to the frame in which the power management mode is set to the power saving mode.

0017The method may further comprise suspending a transmission of a stream corresponding to a reception apparatus that satisfies a predetermined criterion, so that the reception apparatus satisfying the predetermined criterion maintains the operation state to be in a sleep state for an amount of remaining time in the TXOP.

0018The predetermined criterion may comprise a first criterion, a second criterion, and a third criterion, if the reception apparatus is not included in a group of a group ID, the first criterion may be satisfied, if the reception apparatus is included in the group of the group ID, and when there is no stream of data to be transmitted to the reception apparatus from the transmission apparatus during the TXOP, the second criterion may be satisfied, and if an indicator indicating that there is no additional stream to be transmitted to the reception apparatus during the TXOP is received, the third criterion is satisfied.

0019The method may further comprise transmitting a frame comprising an enabling bit enabling a reception apparatus to selectively determine whether to change the operation state of the reception apparatus based on the first criterion and the second criterion.

0020The method may further comprise generating an indicator indicating that there is no additional stream to be transmitted to a reception apparatus during the TXOP.

0021The generating may comprise generating the indicator indicating that there is no additional stream to be transmitted to the reception apparatus using a preamble of a packet transmitted to the reception apparatus or a header of a media access control (MAC) frame transmitted to the reception apparatus.

0022The method may further comprise a buffering a stream to be transmitted to a reception apparatus in the sleep state when the stream to be transmitted to the reception state occurs during the remaining time of the TXOP.

0023The method may further comprise transmitting, to the reception apparatuses, a TXOP setting frame including information associated with the TXOP duration, wherein the TXOP setting frame is generated to be decodable by both a reception apparatus having set the power management mode to the power saving mode, and a reception apparatus having not set the power management mode to the power saving mode.

0024In another aspect, there is provided a computer-readable storage medium comprising program instructions to cause a computer to implement a method including setting a power management mode to a power saving mode during a transmission opportunity (TXOP), receiving information transmitted from a transmitting apparatus, and determining an operation state of the reception apparatus by determining whether a predetermined criterion is satisfied based on the information received from the transmission apparatus, wherein streams corresponding to one or more reception apparatuses are simultaneously transmitted from the transmission apparatus during the TXOP.

0025In another aspect, there is provided a reception apparatus capable of determining a power management mode to operate in during a transmission opportunity (TXOP) of a transmission apparatus, the reception apparatus including a controller configured to determine whether the reception apparatus is to operate in a power saving mode (TXOP PS mode) and a non-power saving mode (non-TXOP PS mode), and a transmitter configured to transmit a frame to the transmission apparatus in which the frame indicates whether the reception apparatus desires to operate in the TXOP PS mode or the non-TXOP PS mode.

0026In response to determining that the reception apparatus is to operate in TXOP PS mode, the controller may set a power management field of the frame to indicate that the reception apparatus desires to operate in TXOP PS mode.

0027The frame may be an association request frame, and the controller may set a capabilities/support field of the association request frame to indicate whether the reception apparatus desires to operate in TXOP PS mode or in non-TXOP PS mode.

0028The reception apparatus may further comprise a receiver configured to receive an acknowledgment (ACK) from the transmission apparatus in response to the association request frame transmitted from transmitter.

0029If the receiver receives the ACK from the transmission apparatus, the controller may set the power management mode of the reception apparatus to the TXOP PS mode, and if the receiver does not receive the ACK from the transmission apparatus, the controller may set the power management mode of the reception apparatus to the non-TXOP PS mode.

0030In another aspect, there is provided a transmission apparatus for transmitting data to a plurality of terminals during a transmission opportunity (TXOP), the transmission apparatus including a receiver configured to receive a frame in which a power management mode is set to a power saving mode (TXOP PS mode), a controller configured to determine if the transmission apparatus is capable of supporting the TXOP PS mode, and a transmitter, in response to determining that the transmission apparatus is capable of supporting the TXOP PS mode, configured to transmit an acknowledgment message to the reception apparatus.

0031The frame may be an association request frame, and a capabilities/support field of the association request frame may be set to indicate that the reception apparatus desires to operate in TXOP PS mode.

0032Other features and aspects may be apparent from the following detailed description, the drawings, and the claims.

<u>BRIEF DESCRIPTION OF THE DRAWINGS</u>

0033<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a diagram illustrating an example of a reception apparatus operating in a transmission opportunity (TXOP) power saving mode.</li><li><figref idref="f0002">FIG. 2</figref> is a flowchart illustrating an example of a communication method of a reception apparatus.</li><li><figref idref="f0003">FIG. 3</figref> is a flowchart illustrating an example of a communication method of a transmission apparatus.</li><li><figref idref="f0004">FIG. 4</figref> is a diagram illustrating an example of a reception apparatus setting a power management mode to a power saving mode.</li><li><figref idref="f0005">FIG. 5</figref> is a diagram illustrating an example of a frame transmitted and received during a TXOP.</li><li><figref idref="f0006">FIG. 6</figref> is a diagram illustrating an example of a TXOP setting frame and a TXOP duration.</li><li><figref idref="f0007">FIG. 7</figref> is a diagram illustrating an example of a reception apparatus.</li><li><figref idref="f0007">FIG. 8</figref> is a diagram illustrating an example of a transmission apparatus.</li></ul>

0034Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals should be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience.

<u>DETAILED DESCRIPTION</u>

0035The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. Accordingly, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein may be suggested to those of ordinary skill in the art. Also, description of well-known functions and constructions may be omitted for increased clarity and conciseness.

0036<figref idref="f0001">FIG. 1</figref> illustrates an example of a reception apparatus operating in a transmission opportunity (TXOP) power saving mode.

0037At least one reception apparatus receiving data from a transmission apparatus may maintain an active mode in order to receive a packet or a frame transmitted to the at least one reception apparatus. For example, the reception apparatus may be a mobile terminal and the transmission apparatus may be an access point. The reception apparatus may remain in active mode. For example, even though there is is no packet to be transmitted to the reception apparatus, the reception apparatus may remain in the active mode in order to overhear a packet to be transmitted to another terminal.

0038The reception apparatus described herein may support various protocol, for example, an IEEE 802.11 protocol such as IEEE 802.11ac, IEEE 802.11n, and the like.

0039If there is no transmission of data corresponding to the reception apparatus, or when the transmission of data to the reception apparatus is completed, it is possible to save power, for example, receive standby time and receive standby power by adjusting an operation mode of the corresponding reception apparatus. For example, the reception apparatus may switch from an awake state to a sleep state or a doze state.

0040Referring to <figref idref="f0001">FIG. 1</figref>, a power management mode of reception apparatuses may include an active mode 110 and a power saving (PS) mode 120. While in the active mode 110, the reception apparatus may enter into two power management modes, a non-power save mode (non-TXOP PS mode) in which the reception apparatus stays awake, and a power save mode (TXOP PS mode) in which the reception apparatus may switch between an awake state 150 and doze state 160.

0041The active mode 110 may correspond to a state in which the reception apparatus may be continuously operating to transmit and receive data to and from a transmission apparatus. The PS mode 120 may be a state, for example, an idle state in which the reception apparatus does not operate or otherwise reduces overall power consumption.

0042In this example, the reception apparatuses operating in the active mode 110 may be divided into reception apparatuses operating in a non-TXOP PS mode 130 and reception apparatuses operating in a TXOP PS mode 140.

0043The reception apparatuses operating in the non-TXOP PS mode 130 may maintain an awake state without a separate operation for the power saving. Accordingly, the reception apparatuses operating in the non-TXOP PS mode 130 may continuously consume power for a receive standby time used to wait for receiving a packet to be transmitted to corresponding reception apparatuses.

0044The reception apparatuses operating in the TXOP PS mode 140 may change an operation state to an awake state 150 or to a sleep state such as a doze state 160, depending on whether a predetermined criterion is satisfied.

0045For example, a predetermined criterion may be satisfied if an identifier (ID) of a corresponding reception apparatus is not included in a group of a group ID included in a preamble of a frame received from the transmission apparatus. As another example, a predetermined criterion may be satisfied if the ID of the corresponding reception apparatus is included in the group of the group ID, however, a number of state time space (N_STS) included in a very high throughput signal (VHT-SIG) field of the received frame is set to '0' to indicate that the transmission apparatus does not have data to transmit to the reception apparatus during the TXOP. As another example, a predetermined criterion may be satisfied if a 'more data bit (MDB)' included in a Media Access Control (MAC) header of the received frame is '0', and the like.

0046For example, the criterion that the N_STS included in the VHT-SIG field of the received frame is '0' may indicate that there is no data or a stream that is to be transmitted to the reception apparatus.

0047It should be appreciated throughout these examples that the bit values are merely for purposes of example, and that any bit value may be used.

0048The criterion that the MDB included in the MAC header of the received frame is '0' may indicate that no more additional streams corresponding to the reception apparatus are to be transmitted during the TXOP, that is, that transmission of the stream corresponding to the corresponding reception apparatus is completed. In this example, the group ID may indicate that the reception apparatus is included in the group, and the N_STS field may indicate that the transmission apparatus has data to transmit to the reception apparatus. The MDB included in the MAC header may be set to indicate that the transmission apparatus has completed transmitting data to the reception apparatus during the TXOP.

0049A reception apparatus satisfying any one of the aforementioned criterion may save the receive standby power for the remainder of the TXOP duration by changing an operation state of the reception apparatus from the awake state 150 to the doze state 160. The TXOP duration may indicate a time duration corresponding to a TXOP with respect to a channel obtained by the transmission apparatus.

0050For example, the reception apparatus operating in the TXOP PS mode 140 may save receive standby power and decrease power consumption of the reception apparatus by changing the operation state for the remainder of the TXOP duration based on the predetermined criterion.

0051Hereinafter, the TXOP PS mode 140 is referred to as a power saving mode.

0052The reception apparatus may notify the transmission apparatus about a power management mode of the terminal using a VHT control field of a MAC header. For example, the power management mode may be the power saving mode 120, the non-TXOP PS mode 130, or the TXOP PS mode 140. The reception apparatus may use one or more bits of the control field to indicate which power saving mode the reception apparatus is in.

0053<figref idref="f0002">FIG. 2</figref> illustrates an example of a communication method of a reception apparatus.

0054For example, the reception apparatus may be one reception apparatus from among a plurality of reception apparatuses that operate in an active mode. During a TXOP, streams corresponding to the reception apparatuses may be simultaneously transmitted from a transmission apparatus.

0055In 210, the reception apparatus determines to operate in a power saving mode. In response to determining to operate in the power saving mode, in 220 the reception apparatus transmits, to the transmission apparatus, a frame in which a power management mode is set to the power saving mode.

0056For example, the power management mode may be set to the power saving mode by setting a field or a bit to a value indicating whether the power saving mode is used in a frame transmitted to the transmission apparatus.

0057Conversely, when it is determined that the reception apparatus is not to operate in the power saving mode, for example, when the reception apparatus determines to operate in the non-TXOP PS mode 130 of <figref idref="f0001">FIG. 1</figref>, the reception apparatus may maintain the operation state as the awake state, in 280.

0058In 230, the reception apparatus determines whether an acknowledgement (ACK) is received from the transmission apparatus in response to the frame in which the power management mode is set to the power saving mode.

0059When the ACK is not received from the transmission apparatus in 230, the reception apparatus maintains the operation state as the awake state, in 280. For example, when the ACK is not received from the transmission apparatus, the reception apparatus may not operate in the power saving mode.

0060When the ACK is received from the transmission apparatus, the reception apparatus sets the power management mode to the power saving mode in the TXOP duration, in 240.

0061In 250, the reception apparatus receives, from the transmission apparatus, a TXOP setting frame including information associated with the TXOP duration.

0062For example, the TXOP setting frame may be generated to be decodable by both a reception apparatus having set the power management mode to the power saving mode, and a reception apparatus having not set the power management mode to the power saving mode.

0063A period in which the reception apparatus may receive the TXOP setting frame may not be limited by the aforementioned order, and thus, may be changed for a process of communicating with the transmission apparatus.

0064In this example, the reception apparatus may determine whether the reception apparatus corresponds to a reception apparatus that is to receive a corresponding stream based on the TXOP setting frame received from the transmission apparatus. Based on the determination result, the reception apparatus may transmit, to the transmission apparatus, a response frame with respect to the TXOP setting frame.

0065In 260, the reception apparatus may determine whether a predetermined criterion is satisfied based on information transmitted from the transmission apparatus. The reception apparatus may determine the operation state of the reception apparatus by determining whether the predetermined criterion is satisfied.

0066For example, information transmitted from the transmission apparatus may include at least one of a group ID of a group including the reception apparatus, information about whether a data stream corresponding to the reception apparatus is to be transmitted from the transmission apparatus during the TXOP, and information indicating whether there is an additional stream to be transmitted to the reception apparatus.

0067For example, the predetermined criterion may include a first criterion, a second criterion, and a third criterion. If any one of the criterion are satisfied, the reception apparatus may switch from an awake state to a doze state for the remainder of the duration of the TXOP of the transmission apparatus.

0068For example, if the reception apparatus is not included in the group of the group ID which includes a set of reception apparatuses within a corresponding cell, the first criterion may be satisfied.

0069As another example, if the reception apparatus is included in the group of the group ID, but a stream corresponding to the reception apparatus is not to be transmitted from the transmission apparatus during the TXOP, the second criterion may be satisfied.

0070As another example, if an indicator indicating that there is no additional stream to be transmitted to the reception apparatus during the remainder of the TXOP is received, the third criterion may be satisfied. In this example, the transmission apparatus may transmit a data stream to the reception apparatus during the TXOP, and when the transmission apparatus has completed the transmission of the data stream to the reception apparatus, the transmission apparatus may notify the reception apparatus that transmission is completed using the indicator. As a result, the reception apparatus may enter a sleep state for the remainder of the TXOP.

0071The reception apparatus may selectively determine whether to change the operation state of the reception apparatus based on the first criterion and the second criterion, using an enabling bit included in each of frames transmitted from the transmission apparatus.

0072In response to at least one of the predetermined criterion being satisfied based on information transmitted from the transmission apparatus in 260, the reception apparatus changes the operation state of the reception apparatus from the awake state to the sleep state, in 270. For example, the reception apparatus may save receive standby power and decrease power consumption for receiving data by maintaining the sleep state for the remainder of the TXOP.

0073Conversely, if the predetermined criterion is not satisfied, the reception apparatus maintains the operation state of the reception apparatus in the awake state, in 280.

0074<figref idref="f0003">FIG. 3</figref> illustrates an example of a communication method of a transmission apparatus.

0075In 310, the transmission apparatus receives a frame in which a power management mode is set to a power saving mode, from a reception apparatus that is to operate in the power saving mode from among one or more reception apparatuses having an active mode as the power management mode.

0076In 320, the transmission apparatus transmits an ACK to the reception apparatus in response to the frame in which the power management mode is set to the power saving mode.

0077In 330, the transmission apparatus obtains a TXOP with respect to a channel.

0078In 340, the transmission apparatus maintains streams corresponding to reception apparatuses that have the active mode as a power management mode.

0079In operation 350, the transmission apparatus transmits information that may be used by the reception apparatuses to determine an operation state of each of the reception apparatuses.

0080For example, information that may be used by the reception apparatuses to determine the operation state of each of the reception apparatuses may include at least one of a group ID of a group including each of the reception apparatuses that the transmission apparatus may send data to such as the reception apparatuses in a corresponding cell, information about whether a stream corresponding to each of the reception apparatuses is to be transmitted from the transmission apparatus during the TXOP, and information indicating whether there is an additional stream to be transmitted to the reception apparatuses during the TXOP.

0081In 360, the transmission apparatus simultaneously transmits the streams to at least one of the reception apparatuses during the TXOP.

0082For example, 'simultaneously' transmitting the streams may indicate that the streams are simultaneously transmitted in a spatial aspect or are transmitted using a multi-user multiple input multiple output (MU-MIMO) communication, and may not indicate that transmission of streams corresponding to at least one terminal simultaneously starts and is simultaneously completed.

0083The transmission apparatus may not transmit a stream corresponding to the reception apparatus that is in the sleep state. For example, the reception apparatuses satisfying the predetermined criterion may maintain the operation state as the sleep state for the remainder of the TXOP duration.

0084For example, information used to determine the operation state and the streams may be included in the same frame.

0085The predetermined criterion may include a first criterion, a second criterion, and a third criterion. When the reception apparatus is not included in the group of the group ID including a set of reception apparatuses within a corresponding cell, the first criterion may be satisfied. When the reception apparatus is included in the group of the group ID, but a stream corresponding to the reception apparatus is not to be transmitted from the transmission apparatus during the TXOP, the second criterion may be satisfied. When an indicator indicating that there are no more additional streams to be transmitted to the reception apparatus during the remainder of the TXOP, the third criterion may be satisfied.

0086The group of the group ID may include the set of reception apparatuses within a corresponding cell.

0087The transmission apparatus may transmit a frame including an enabling bit enabling the reception apparatus to selectively determine whether to change the operation state of the reception apparatus based on the first criterion and/or the second criterion.

0088In 370, the transmission apparatus generates an indicator indicating that there is no additional stream to be transmitted to the reception apparatus during the TXOP.

0089For example, in 370, the transmission apparatus may generate the indicator indicating that there is no additional stream to be transmitted to the reception apparatus using a preamble of a packet transmitted to the reception apparatus or a header of a media access control (MAC) frame transmitted to the reception apparatus. For example, the indicator may be a more data bit (MDB) of the MAC header.

0090In 380, the transmission apparatus buffers a stream that is to be transmitted to a reception apparatus for the remainder of the TXOP duration. For example, a TXOP may be cut short for various unforeseen reasons, and the reception apparatus may still be in a sleep state for the remainder of the TXOP which was cut short. Therefore, the transmission apparatus may buffer data that is to be sent to the reception apparatus.

0091For example, when the reception apparatus desires to operate in the power saving mode, the reception apparatus may transmit, to the transmission apparatus, a frame in which a power management mode is set to the power saving mode. The transmission apparatus may transmit an ACK to the reception apparatus in response to the frame.

0092In response, the transmission apparatus may transmit, to the reception apparatus, information about the TXOP such as the Group ID, whether there is a data stream for the reception apparatus, and whether there is an additional data stream for the reception apparatus. The reception apparatus may determine whether the predetermined criterion is satisfied based on the information. In this example, because the information is transmitted from the transmission apparatus, the transmission apparatus also may know whether the predetermined criterion is satisfied for each respective reception apparatus.

0093Accordingly, even if the reception apparatus does not transmit additional information that the reception apparatus is going to enter into the sleep state, the transmission apparatus may recognize that the reception apparatus is going to enter into the sleep state.

0094<figref idref="f0004">FIG. 4</figref> illustrates an example of a reception apparatus setting a power management mode to a power saving mode.

0095Hereinafter, STA may indicate, for example, a reception apparatus, a terminal, a station, and the like, and AP may indicate, for example, a transmission apparatus, an access point, and the like.

0096An STA (1) 403 desiring to operate in a power saving mode may transmit, to an AP (1) 401, a frame 411 in which a power saving mode, that is, a TXOP PS mode, is set to '1'. In this example, setting of the power saving mode to '1' may indicate that a corresponding STA sets the power management mode of the corresponding STA to the power saving mode. The corresponding STA may use, for example, a capabilities/support field of an association request frame to set the power management mode of the STA to indicate that the STA desires to operate in power saving mode.

0097The STA (1) 403 may receive an ACK 413 from the AP (1) 401 as a response to the frame 411.

0098After receiving the ACK 413, the STA (1) 403 may operate in the power saving mode.

0099Similarly, an STA (2) 405 may transmit, to the AP (1) 401, a frame 415 in which the power saving mode is set to '1', and may operate in the power saving mode after receiving an ACK 417 from the AP (1) 401.

0100The STA (1) 403 and the STA (2) 405 may be set to operate in the power saving mode by performing the aforementioned operation as the AP (1) 401 in a TXOP PS mode setting period 410.

0101In a TXOP duration setting period 430, the AP (1) 401, the STA (1) 403, and the STA (2) 405 may set a TXOP duration 450 using a request to send (RTS) frame 431 and a clear to send (CTS) frame 433.

0102The TXOP duration setting period 430 may correspond to a TXOP setting period which is further described later.

0103The RTS frame 431 and the CTS frame 433 may be used to prevent a frame collision known as a hidden node issue. A process may be initiated by transmitting, by a node, for example, the AP (1) 401 desiring to transmit data, the RTS frame 431. In the case of a wireless environment in which a transmission is possible because other signals are not being transmitted, the STA (1) 403 corresponding to a destination node may transmit the CTS frame 433 as a response to the signal.

0104The other nodes receiving the RTS frame 431 or the CTS frame 433 may solve the hidden node issue by limiting a data transmission for a predetermined amount of time. The predetermined amount of time may be included in the RTS frame 431 and the CTS frame 433.

0105<figref idref="f0005">FIG. 5</figref> illustrates an example of a frame transmitted and received during a TXOP. In this example, the second criterion is not considered.

0106Referring to <figref idref="f0005">FIG. 5</figref>, an AP (1) 501 and six STAs, for example, an STA (1) 503, an STA (2) 505, an STA (3) 507, an STA (4) 509, an STA (5) 511, and an STA (6) 513 are present within a single cell or a basic service set (BSS), and the six STAs are shown in Table 1. <tables id="tabl0001" num="0001"><table frame="all"><title>[Table 1]</title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="26mm" /><colspec colnum="2" colname="col2" colwidth="53mm" /><colspec colnum="3" colname="col3" colwidth="59mm" /><thead><row><entry valign="top" /><entry valign="top">Apparatuses using TXOP PS mode</entry><entry valign="top">Apparatuses using non-TXOP PS mode</entry></row></thead><tbody><row><entry>Data in buffer</entry><entry>STA 1, STA 2</entry><entry>STA 4, STA 5, STA 6</entry></row><row><entry>No data</entry><entry>STA 3</entry><entry>N/A</entry></row></tbody></tgroup></table></tables>

0107Referring to Table 1, among the six STAs, the STA (1) 503, the STA (2) 505, and the STA (3) 507 correspond to terminals in a power saving mode, that is, a TXOP PS mode 140 illustrated in <figref idref="f0001">FIG. 1</figref>.

0108In this example, the AP (1) 501 has data to transmit to the STA (1) 503, the STA (2) 505, the STA (4) 509, the STA (5) 511, and the STA (6) 513.

0109Referring to <figref idref="f0005">FIG. 5</figref>, Frame (1) 520 includes all the stations, that is, the STA (1) 503, the STA (2) 505, the STA (3) 507, the STA (4) 509, the STA (5) 511, and the STA (6) 513, in a group of a group ID included in a preamble 521. Accordingly, after receiving the frame (1) 520, the first criterion is not satisfied for any STA.

0110Frame (1) 520 includes data 523 to be transmitted to the STA (1) 503, and data 525 to be transmitted to the STA (4) 509, and an MDB of the STA (1) 503 is set to '0'.

0111The MDB of the STA (1) 503 is set to '0' which in this example indicates that there is no more data to be additionally transmitted from the AP (1) 501 to the STA (1) 503. Accordingly, the STA (1) 503 may transmit a block acknowledgement (BA) 590 to the AP (1) 501 and then operate in the power saving mode until the end of the TXOP, thereby reducing a standby power consumption. An example of the power saving state is a sleep state or a doze state.

0112After completing reception of a corresponding stream based on the MDB, or after transmitting the BA 590 with respect to the corresponding stream, the STA (1) 503 may maintain the operation state of the STA (1) 503 in a sleep state for the remaining time of the TXOP duration.

0113Frame (2) 540 includes the STA (2) 505, the STA (3) 507, and the STA (4) 509 in a group of a group ID included in a preamble 541, and includes data 543 to be transmitted to the STA (2) 505 and data 545 to be transmitted to the STA (4) 509.

0114The STA (3) 507 in the power saving mode, that is, the TXOP PS mode does not have data to receive from the AP (1) 501, however, is included in the group ID. Accordingly, the STA (3) 507 may not enter the sleep state. That is, in the example of <figref idref="f0005">FIG. 5</figref>, the STAs do not consider the second criterion, but only consider the first and third criterion.

0115In frame (2) 540, an MDB of the STA (2) 505 is set to '1' and thus, STA (2) 505 may remain in an awake state.

0116In frame (2) 540, an MDB of the STA (4) 509 is set to '0', however, STA (4) 509 is in non-TXOP PS mode and does not use the power saving mode. Accordingly, even after transmitting, to the AP (1) 501, BAs 593 and 594 in response to the frame (1) 520 and the frame (2) 540, the STA (4) 509 may remain in the awake state instead of saving power.

0117Frame (3) 560 includes the STA (2) 505 and the STA (5) 511 in a group of a group ID included in a preamble 561, and includes data 563 to be transmitted to the STA (2) 505 and data 565 to be transmitted to the STA (5) 511.

0118The STA (3) 507 operating in the power saving mode is included in a group of a group ID of a frame (4) 580, and therefore, the first criterion is satisfied for the STA (3) 507. Thus, the STA (3) 507 may enter into a power saving mode for the remainder of the TXOP.

0119In the example of <figref idref="f0005">FIG. 5</figref>, operating in the power saving mode may indicate remaining in the sleep state.

0120In frame (3) 560, the MDB of the STA (2) 505 is set to '0' and thus, the STA (2) 505 may enter into the power saving mode and may maintain the sleep state for the remainder of the TXOP duration.

0121Frame (4) 580 includes the STA (5) 511 and the STA (6) 513 in a group of a group ID included in a preamble 581, and includes data 583 to be transmitted to the STA (5) 511 and data 585 to be transmitted to the STA (6) 513. Even though frame (4) 580 includes the STA (3) 507, the STA (3) 507 is already in the sleep state. Accordingly, the STA (3) 507 may continuously maintain the sleep state during the TXOP duration.

0122The STA (5) 511 and the STA (6) 513 may receive frame (4) 580 and may transmit BAs 596 and 597 to the AP (1) 501.

0123The AP (1) 501 may include any STAs in a group of a group ID of a frame to be transmitted. However, STAs that are in the sleep state may not receive a corresponding frame. Accordingly, the AP (1) 501 may buffer data to be transmitted while a corresponding STA is in the sleep state.

0124<figref idref="f0006">FIG. 6</figref> illustrates an example of a TXOP setting frame and a TXOP duration.

0125Referring to <figref idref="f0006">FIG. 6</figref>, an AP (1) 601 may set a time duration corresponding to a TXOP with respect to a channel. For example, the AP (1) 601 may set a TXOP duration 630 by transmitting a TXOP setting frame 620 in a TXOP setting period 610.

0126The TXOP setting frame 620 may include information used to set the time duration corresponding to the TXOP duration 630. The TXOP setting frame 620 may be transmitted in a form form that may be overheard by all the STAs within a cell or a BSS. For example, the STAs may include reception apparatuses having set a power management mode to a power saving mode such as a sleep state, and reception apparatuses having not set the power management mode to the power saving mode such as in the awake state.

0127For example, a multi-user precoding scheme and the like may not be applied to the TXOP setting frame 620. The TXOP setting frame 620 may be generated to be decodable by all the STAs within the cell even those STAs that are in a sleep state.

0128The TXOP setting frame 620 may include information about whether to apply the power saving mode, or a target reception group that is a transmission target of a frame during the corresponding TXOP duration 630. Information associated with the target reception group may include a predetermined group that have the same group ID and STAs belonging to the predetermined group.

0129When the TXOP setting frame 620 includes information associated with the target reception group, STAs excluded from a corresponding reception group may maintain the sleep state by the end of the TXOP duration 630 after receiving the TXOP setting frame 620.

0130A single STA or STAs belonging to the target reception group may transmit a response frame 660 with respect to the TXOP setting frame 620. For example, the response frame 660 may include a portion of or all of descriptions included in the TXOP setting frame 620.

0131Accordingly, hidden nodes not receiving the TXOP setting frame 620 may set a TXOP. When at least one STA transmits the response frame 660, the at least one STA may transmit the response frame 660 according to a predetermined order and a predetermined method. Otherwise, corresponding information may be included in the TXOP setting frame 620.

0132The TXOP setting period 610 may be used to set the time duration corresponding to the TXOP with respect to the channel, for example, the TXOP duration 630.

0133As an example, in the TXOP setting period 610 for setting the TXOP duration 630, the AP (1) 601 may transmit the TXOP setting frame 620 to an STA (1) 603, an STA (2) 605, an STA (3) 607, and an STA (4) 609 within a cell.

0134The TXOP setting frame 620 may be used for a corresponding reception apparatus to receive a corresponding stream in the TXOP duration 630, or to operate in the power saving mode.

0135For example, the TXOP setting frame 620 may include a preamble 621, a legacy signal field (L-SIG) 623, and TXOP setting information 625 for setting the TXOP duration 630.

0136Each of the STA (1) 603, the STA (2) 605, the STA (3) 607, and the STA (4) 609 may set the time duration corresponding to the TXOP with respect to the channel, based on the TXOP setting information 625.

0137In this example, each of the STA (1) 603, the STA (2) 605, and the STA (3) 607 are to receive data from the AP (1) 601 and may access a radio channel in the TXOP duration 630 to receive a packet or a frame from the AP (1) 601.

0138However, the STA (4) 609 is not to receive data from the AP (1) 601 and may not access the radio channel in the TXOP duration 630.

0139The TXOP setting information 625 may include information associated with a group of STAs to receive the data from the AP (1) 601 among the STA (1) 603, the STA (2) 605, the STA (3) 607, and the STA (4) 609.

0140Each of the STA (1) 603, the STA (2) 605, the STA (3) 607, and the STA (4) 609 may set the TXOP duration 630 based on the TXOP setting information 625. In the TXOP duration 630, data transmission may be performed between the AP (1) 601 and each of the STA (1) 603, the STA (2) 605, the STA (3) 607, and the STA (4) 609 using a method similar to the method described above with reference to <figref idref="f0005">FIG. 5</figref>.

0141The STA (1) 603 to receive data from the AP (1) 601 may transmit, to the AP (1) 601, the response frame 660 with respect to the TXOP setting information 625. The response frame 660 with respect to the TXOP setting information 625 may prevent entangling of the STA (1) 603, the STA (2) 605, the STA (3) 607, and the STA (4) 609 when coverages of a plurality of APs are overlapped with each other.

0142<figref idref="f0007">FIG. 7</figref> illustrates an example of a reception apparatus.

0143Referring to <figref idref="f0007">FIG. 7</figref>, reception apparatus 700 includes a transmitter 710 for transmitting data, a controller 720 for controlling the operation of the reception apparatus 700, and a receiver 730 for receiving data.

0144The reception apparatus 700 is capable of determining a power management mode to operate in during a transmission opportunity (TXOP) of a transmission apparatus. For example, the power management mode may include at least one of a non-power saving mode (non-TXOP PS mode) and a power saving mode (TXOP PS mode).

0145The controller 720 may determine whether the reception apparatus 700 is to operate in the power saving mode (TXOP PS mode) or the non-power saving mode (non-TXOP PS mode). In response to determining that the reception apparatus 700 is to operate in TXOP PS mode, the controller 720 may set power management field of the frame to indicate that the reception apparatus 700 desires to operate in TXOP PS mode.

0146For example, the frame may be an association request frame, and the controller 720 may set a capabilities/support field of the association request frame to indicate whether the reception apparatus 700 desires to operate in TXOP PS mode or in non-TXOP PS mode.

0147The transmitter 710 may transmit the frame to the transmission apparatus in which the frame indicates whether the reception apparatus 700 desires to operate in the TXOP PS mode or the non-TXOP PS mode.

0148In response to receiving the frame from the reception apparatus 700, the transmission apparatus may transmit an acknowledgment message (ACK) to the reception apparatus 700. The a receiver 730 may receive the acknowledgment (ACK) from the transmission apparatus in response to the association request frame transmitted from transmitter 710.

0149In response to the receiver 730 receiving the ACK from the transmission apparatus, the controller 720 may set the power management mode of the reception apparatus 700 to the TXOP PS mode, and if the receiver 730 does not receive the ACK from the transmission apparatus, the controller 720 may set the power management mode of the reception apparatus 700 to the non-TXOP PS mode.

0150<figref idref="f0007">FIG. 8</figref> illustrates an example of a transmission apparatus.

0151Referring to <figref idref="f0007">FIG. 8</figref>, transmission apparatus 800 includes a receiver 810 for receiving data, a controller 820 for controlling the transmission apparatus 800, and a transmitter 830 for transmitting data.

0152The transmission apparatus 800 may transmit data to one or more terminals during a transmission opportunity (TXOP). The receiver 810 may receive a frame in which a power management mode is set to a power saving mode (TXOP PS mode). For example, the receiver 810 may receive a frame from a reception apparatus. The frame may be an association request frame, and a capabilities/support field of the association request frame may be set to indicate that the reception apparatus desires to operate in TXOP PS mode.

0153The controller 820 may determine if the transmission apparatus 800 is capable of supporting the TXOP PS mode. In response to determining that the transmission apparatus 800 is capable of supporting the TXOP PS mode, the transmitter 830 may transmit an acknowledgment message to the reception apparatus. It should be appreciated that the examples described with reference to <figref idref="f0001 f0002 f0003 f0004 f0005 f0006">FIGS. 1-6</figref> are also applicable to the reception apparatus 700 and the transmission apparatus 800 described with reference to <figref idref="f0007">FIGS. 7 and 8</figref>. Further description thereof is omitted for concision. According to various aspects, reception apparatuses desiring to operate in a power saving mode among reception apparatuses operating in an active mode may transmit a frame in which a power management mode is set to the power saving mode and thereby be enabled to selectively determine whether to operate in the power saving mode.

0154According to various aspects, when there is no data stream pending for a reception apparatus operating in a power saving mode, it is possible to decrease a receive standby power by maintaining an operation state of the corresponding reception apparatus in a sleep state during the TXOP or for the remainder of the TXOP.

0155According to various aspects, when a reception apparatus operating in a power saving mode satisfies a predetermined criterion, it is possible to decrease power consumption by changing an operation state of the corresponding reception apparatus from an awake state to a sleep state.

0156The processes, functions, methods and/or software described above may be recorded, stored, or fixed in one or more computer-readable storage media that includes program instructions to be implemented by a computer to cause a processor to execute or perform the program instructions. The media may also include, alone or in combination with the program instructions, data files, data structures, and the like. The media and program instructions may be those specially designed and constructed, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD ROM disks and DVDs; magneto-optical media such as optical disks; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory (ROM), random access memory (RAM), flash memory, and the like. Examples of program instructions include both machine code, such as produced by a compiler, and files containing higher level code that may be executed by the computer using an interpreter. The described hardware devices may be configured to act as one or more software modules that are recorded, stored, or fixed in one or more computer-readable storage media, in order to perform the operations and methods described above, or vice versa. In addition, a computer-readable storage medium may be distributed among computer systems connected through a network and non-transitory computer-readable codes or program instructions may be stored and executed in a decentralized manner.

0157As a non-exhaustive illustration only, the terminal device described herein may refer to mobile devices such as a cellular phone, a personal digital assistant (PDA), a digital camera, a portable game console, an MP3 player, a portable/personal multimedia player (PMP), a handheld e-book, a portable lab-top personal computer (PC), a global positioning system (GPS) navigation, and devices such as a desktop PC, a high definition television (HDTV), an optical disc player, a setup box, and the like, capable of wireless communication or network communication consistent with that disclosed herein.

0158A computing system or a computer may include a microprocessor that is electrically connected with a bus, a user interface, and a memory controller. It may further include a flash memory device. The flash memory device may store N-bit data via the memory controller. The N-bit data is processed or will be processed by the microprocessor and N may be 1 or an integer greater than 1. Where the computing system or computer is a mobile apparatus, a battery may be additionally provided to supply operation voltage of the computing system or computer.

0159It should be apparent to those of ordinary skill in the art that the computing system or computer may further include an application chipset, a camera image processor (CIS), a mobile Dynamic Random Access Memory (DRAM), and the like. The memory controller and the flash memory device may constitute a solid state drive/disk (SSD) that uses a nonvolatile memory to store data.

0160A number of examples have been described above. Nevertheless, it should be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and/or if components in a described system, architecture, device, or circuit are combined in a different manner and/or replaced or supplemented by other components or their equivalents. Accordingly, other implementations are within the scope of the following claims.