WO2017119758A2 - Method for managing power in wireless lan system and terminal using same - Google Patents

Abstract

A method for managing power in a wireless LAN system according to an embodiment of the present specification comprises the steps of: receiving a beacon frame including contention window information for a backoff counter of an OFDMA-based random access, and start time information of a service duration for the OFDMA-based random access from an access point (AP) by a user STA; receiving a reference trigger frame for the service duration on the basis of the start time information from the AP by the user STA, wherein the reference trigger frame includes allocation information indicating a plurality of resource units and quantity information associated with the total number of resource units to be allocated during the service duration; and determining whether to switch from an awake state to a sleep state on the basis of a first value according to the quantity information and a second value set in the backoff counter according to the contention window information, by the user STA.

Description

Method for power management in wireless LAN system and terminal using same

The present disclosure relates to wireless communication, and more particularly, to a method for power management in a WLAN system and a terminal using the same.

Recently, with the development of information and communication technology, various wireless communication technologies have been developed. In particular, a wireless local area network (WLAN) is a technology that enables wireless access to the Internet in a home, business, or specific service providing area using a portable terminal based on radio frequency technology.

For example, the portable terminal may be a personal digital assistant (PDA), a laptop, a portable multimedia player (PMP). In general, communication between terminals in a WLAN system is performed through a management entity such as a base station or an access point. The management medium is responsible for scheduling for data communication.

In order to secure the flexibility of the communication between terminals in a WLAN system, various protocols for direct communication between terminals without a management medium have been proposed. NAN is a standard established by the Wi-Fi Alliance (WFA) based on the Wi-Fi standard. The NAN specification provides for synchronization and discovery procedures between devices in the 2.5 GHz or 5 GHz frequency band.

An object of the present specification is to provide a method for power management to reduce power consumption in a WLAN system and a terminal using the same.

The present specification relates to a method for power management in a WLAN system. According to an embodiment of the present disclosure, a user station (ST) may include contention window information for a backoff counter of orthogonal frequency division multiple access (OFDMA) based random access and a service period for OFDMA based random access. Receiving a beacon frame containing the start time information of the AP from the access point, the user STA receives a reference trigger frame from the AP in the service interval based on the start time information The reference trigger frame includes allocation information indicating a plurality of resource units and quantity information on the total number of resource units to be allocated during a service interval. Whether to switch from an awake state to a doze state based on the second value set in the backoff counter according to the value and the contention window information. Determining portion.

According to an embodiment of the present disclosure, a method for power management to reduce power consumption in a WLAN system and a terminal using the same are provided.

1 is a conceptual diagram illustrating a structure of a WLAN system.

2 is a diagram illustrating an example of a PPDU used in the IEEE standard.

3 is a diagram illustrating an example of a HE PPDU.

4 is a diagram illustrating an arrangement of resource units used on a 20 MHz band.

5 is a diagram illustrating an arrangement of resource units used on a 40 MHz band.

6 is a diagram illustrating an arrangement of resource units used on an 80 MHz band.

7 is a diagram illustrating another example of the HE-PPDU.

8 is a block diagram illustrating an example of HE-SIG-B.

9 shows an example of a trigger frame.

10 shows an example of a common information field.

11 shows an example of subfields included in individual user information fields.

12 is a diagram illustrating an existing OFDMA based random access procedure by way of example.

13 is a conceptual diagram illustrating a service interval and a start time according to an exemplary embodiment.

14 is a diagram illustrating a method for power management of a WLAN system according to an exemplary embodiment.

15 is a flowchart illustrating a method for power management of a WLAN system according to an exemplary embodiment.

16 is a diagram illustrating a method for power management of a WLAN system according to another exemplary embodiment.

17 is a diagram illustrating a method for power management of a WLAN system according to another embodiment.

18 is a block diagram illustrating a wireless terminal to which an embodiment can be applied.

The above-described features and the following detailed description are all exemplary for ease of description and understanding of the present specification. That is, the present specification is not limited to this embodiment and may be embodied in other forms. The following embodiments are merely examples to fully disclose the present specification, and are descriptions to convey the present specification to those skilled in the art. Thus, where there are several methods for implementing the components of the present disclosure, it is necessary to clarify that any of these methods may be implemented in any of the specific or equivalent thereof.

In the present specification, when there is a statement that a configuration includes specific elements, or when a process includes specific steps, it means that other elements or other steps may be further included. That is, the terms used in the present specification are only for describing specific embodiments and are not intended to limit the concept of the present specification. Furthermore, the described examples to aid the understanding of the invention also include their complementary embodiments.

The terminology used herein has the meaning commonly understood by one of ordinary skill in the art to which this specification belongs. Terms commonly used should be interpreted in a consistent sense in the context of the present specification. In addition, terms used in the present specification should not be interpreted in an idealistic or formal sense unless the meaning is clearly defined. Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

1 is a conceptual diagram illustrating a structure of a WLAN system. FIG. 1A shows the structure of an infrastructure network of the Institute of Electrical and Electronic Engineers (IEEE) 802.11.

Referring to FIG. 1A, the WLAN system 10 of FIG. 1A may include at least one basic service set (hereinafter, referred to as 'BSS', 100, 105). The BSS is a set of access points (APs) and stations (STAs) that can successfully synchronize and communicate with each other, and is not a concept indicating a specific area.

For example, the first BSS 100 may include a first AP 110 and one first STA 100-1. The second BSS 105 may include a second AP 130 and one or more STAs 105-1, 105-2.

The infrastructure BSS (100, 105) may include at least one STA, AP (110, 130) providing a distribution service (Distribution Service) and a distribution system (DS, 120) connecting a plurality of APs. have.

The distributed system 120 may connect the plurality of BSSs 100 and 105 to implement an extended service set 140 which is an extended service set. The ESS 140 may be used as a term indicating one network to which at least one AP 110 or 130 is connected through the distributed system 120. At least one AP included in one ESS 140 may have the same service set identification (hereinafter, referred to as SSID).

The portal 150 may serve as a bridge for connecting the WLAN network (IEEE 802.11) with another network (for example, 802.X).

In a WLAN having a structure as shown in FIG. 1A, a network between APs 110 and 130 and a network between APs 110 and 130 and STAs 100-1, 105-1, and 105-2 may be implemented. Can be.

1B is a conceptual diagram illustrating an independent BSS. Referring to FIG. 1B, the WLAN system 15 of FIG. 1B performs communication by setting a network between STAs without the APs 110 and 130, unlike FIG. 1A. It may be possible to. A network that performs communication by establishing a network even between STAs without the APs 110 and 130 is defined as an ad-hoc network or an independent basic service set (BSS).

Referring to FIG. 1B, the IBSS 15 is a BSS operating in an ad-hoc mode. Since IBSS does not contain an AP, there is no centralized management entity. Thus, in the IBSS 15, the STAs 150-1, 150-2, 150-3, 155-4, and 155-5 are managed in a distributed manner.

All STAs 150-1, 150-2, 150-3, 155-4, and 155-5 of the IBSS may be mobile STAs, and access to a distributed system is not allowed. All STAs of the IBSS form a self-contained network.

The STA referred to herein includes a medium access control (MAC) conforming to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard and a physical layer interface to a wireless medium. As any functional medium, it can broadly be used to mean both an AP and a non-AP Non-AP Station (STA).

The STA referred to herein includes a mobile terminal, a wireless device, a wireless transmit / receive unit (WTRU), a user equipment (UE), and a mobile station (MS). It may also be called various names such as a mobile subscriber unit or simply a user.

2 is a diagram illustrating an example of a PPDU used in the IEEE standard.

As shown, various types of PHY protocol data units (PPDUs) have been used in the IEEE a / g / n / ac standard. Specifically, the LTF and STF fields included training signals, the SIG-A and SIG-B included control information for the receiving station, and the data fields included user data corresponding to the PSDU.

This embodiment proposes an improved technique for the signal (or control information field) used for the data field of the PPDU. The signal proposed in this embodiment may be applied on a high efficiency PPDU (HE PPDU) according to the IEEE 802.11ax standard. That is, the signals to be improved in the present embodiment may be HE-SIG-A and / or HE-SIG-B included in the HE PPDU. Each of HE-SIG-A and HE-SIG-B may also be represented as SIG-A or SIG-B. However, the improved signal proposed by this embodiment is not necessarily limited to the HE-SIG-A and / or HE-SIG-B standard, and controls / control of various names including control information in a wireless communication system for transmitting user data. Applicable to data fields.

3 is a diagram illustrating an example of a HE PPDU.

The control information field proposed in this embodiment may be HE-SIG-B included in the HE PPDU as shown in FIG. 3. The HE PPDU according to FIG. 3 is an example of a PPDU for multiple users. The HE-SIG-B may be included only for the multi-user, and the HE-SIG-B may be omitted in the PPDU for the single user.

As shown, a HE-PPDU for a multiple user (MU) includes a legacy-short training field (L-STF), a legacy-long training field (L-LTF), a legacy-signal (L-SIG), High efficiency-signal A (HE-SIG-A), high efficiency-signal-B (HE-SIG-B), high efficiency-short training field (HE-STF), high efficiency-long training field (HE-LTF) It may include a data field (or MAC payload) and a PE (Packet Extension) field. Each field may be transmitted during the time period shown (ie, 4 or 8 ms, etc.). Detailed description of each field of FIG. 3 will be described later.

4 is a diagram illustrating an arrangement of resource units (RUs) used on a 20 MHz band. As shown in FIG. 4, resource units (RUs) corresponding to different numbers of tones (ie, subcarriers) may be used to configure some fields of the HE-PPDU. For example, resources may be allocated in units of RUs shown for HE-STF, HE-LTF, and data fields.

As shown at the top of FIG. 4, 26-units (ie, units corresponding to 26 tones) may be arranged. Six tones may be used as the guard band in the leftmost band of the 20 MHz band, and five tones may be used as the guard band in the rightmost band of the 20 MHz band. In addition, seven DC tones are inserted into the center band, that is, the DC band, and 26-units corresponding to each of the 13 tones may exist to the left and right of the DC band. In addition, other bands may be allocated 26-unit, 52-unit, 106-unit. Each unit can be assigned for a receiving station, i. E. A user.

On the other hand, the RU arrangement of FIG. 4 is utilized not only for the situation for a plurality of users (MU), but also for the situation for a single user (SU), in which case one 242-unit is shown as shown at the bottom of FIG. It is possible to use and in this case three DC tones can be inserted.

In the example of FIG. 4, various sizes of RUs have been proposed, that is, 26-RU, 52-RU, 106-RU, 242-RU, and the like. Since the specific sizes of these RUs can be expanded or increased, the present embodiment Is not limited to the specific size of each RU (ie, the number of corresponding tones).

5 is a diagram illustrating an arrangement of resource units (RUs) used on a 40 MHz band.

Just as RUs of various sizes are used in the example of FIG. 4, the example of FIG. 5 may also use 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, and the like. In addition, five DC tones can be inserted at the center frequency, 12 tones are used as the guard band in the leftmost band of the 40 MHz band, and 11 tones are in the rightmost band of the 40 MHz band. This guard band can be used.

Also, as shown, the 484-RU may be used when used for a single user. Meanwhile, the specific number of RUs may be changed as in the example of FIG. 4.

6 is a diagram illustrating an arrangement of resource units (RUs) used on an 80 MHz band.

Just as RUs of various sizes are used in the example of FIGS. 4 and 5, the example of FIG. 6 may also use 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, 996-RU, and the like. have. In addition, seven or five DC tones can be inserted at the center frequency, and 12 tones are used as the guard band in the leftmost band of the 80 MHz band, and in the rightmost band of the 80 MHz band. Eleven tones can be used as guard bands. Also available is a 26-RU with 13 tones each located to the left and right of the DC band.

Also, as shown, 996-RU may be used when used for a single user. Meanwhile, the specific number of RUs may be changed as in the example of FIGS. 4 and 5.

7 is a diagram illustrating another example of the HE-PPDU.

7 is another example illustrating the HE-PPDU block of FIG. 3 in terms of frequency.

The illustrated L-STF 700 may include a short training orthogonal frequency division multiplexing symbol. The L-STF 700 may be used for frame detection, automatic gain control (AGC), diversity detection, and coarse frequency / time synchronization.

The L-LTF 710 may include a long training orthogonal frequency division multiplexing symbol. The L-LTF 710 may be used for fine frequency / time synchronization and channel prediction.

L-SIG 720 may be used to transmit control information. The L-SIG 720 may include information about a data rate and a data length. In addition, the L-SIG 720 may be repeatedly transmitted. That is, the L-SIG 720 may be configured in a repeating format (for example, may be referred to as an R-LSIG).

The HE-SIG-A 730 may include control information common to the receiving station.

Specifically, the HE-SIG-A 730 may include 1) a DL / UL indicator, 2) a BSS color field which is an identifier of a BSS, 3) a field indicating a remaining time of a current TXOP interval, 3) 20, Bandwidth field indicating 40, 80, 160, 80 + 80 Mhz, 4) Field indicating MCS scheme applied to HE-SIG-B, 5) HE-SIB-B is dual subcarrier modulation for MCS ( field indicating whether the modulation is performed using a dual subcarrier modulation), 6) a field indicating the number of symbols used for the HE-SIG-B, and 7) a field indicating whether the HE-SIG-B is generated over the entire band. Field, 8) field indicating the number of symbols in the HE-LTF, 8) field indicating the length and CP length of the HE-LTF, 9) field indicating whether additional OFDM symbols exist for LDPC coding, 10) 11) field indicating the control information on the PE (packet extension), 11) field indicating the information on the CRC field of the HE-SIG-A, etc. may be included. All. Specific fields of the HE-SIG-A may be added or omitted. In addition, some fields may be added or omitted in other environments where the HE-SIG-A is not a multi-user (MU) environment.

The HE-SIG-B 740 may be included only when it is a PPDU for a multi-user (MU) as described above. Basically, the HE-SIG-A 730 or the HE-SIG-B 740 may include resource allocation information (or virtual resource allocation information) for at least one receiving STA. The HE-SIG-B 740 is described in more detail with reference to FIG. 8 described below.

The previous field of the HE-SIG-B 740 on the MU PPDU may be transmitted in duplicated form. In the case of the HE-SIG-B 740, the HE-SIG-B 740 transmitted in a part of the frequency band (for example, the fourth frequency band) is the frequency band (that is, the fourth frequency band) of the Control information for a data field and a data field of another frequency band (eg, the second frequency band) except for the corresponding frequency band may be included. In addition, the HE-SIG-B 740 of a specific frequency band (eg, the second frequency band) duplicates the HE-SIG-B 740 of another frequency band (eg, the fourth frequency band). It can be one format. Alternatively, the HE-SIG-B 740 may be transmitted in an encoded form on all transmission resources. The field after the HE-SIG-B 740 may include individual information for each receiving STA that receives the PPDU.

The HE-STF 750 may be used to improve automatic gain control estimation in a multiple input multiple output (MIMO) environment or an orthogonal frequency-division multiple access (OFDMA) environment.

The HE-LTF 760 may be used to estimate a channel in a MIMO environment or an OFDMA environment.

The size of the FFT / IFFT applied to the field after the HE-STF 750 and the HE-STF 750 may be different from the size of the FFT / IFFT applied to the field before the HE-STF 750. For example, the size of the FFT / IFFT applied to the fields after the HE-STF 750 and the HE-STF 750 may be four times larger than the size of the IFFT applied to the field before the HE-STF 750. .

For example, at least one of L-STF 700, L-LTF 710, L-SIG 720, HE-SIG-A 730, HE-SIG-B 740 on the PPDU of FIG. When a field of s is called a first field, at least one of the data field 770, the HE-STF 750, and the HE-LTF 760 may be referred to as a second field. The first field may include a field related to a legacy system, and the second field may include a field related to a HE system. In this case, the FFT (Fast Fourier Transform) size / IFFT (Inverse Fast Fourier Transform) size is N times the FFT / IFFT size used in the existing WLAN system (N is a natural number, for example, N = 1, 2, 4) can be defined. That is, an FFT / IFFT of N (= 4) times size may be applied to the second field of the HE PPDU compared to the first field of the HE PPDU. For example, 256 FFT / IFFT is applied for a bandwidth of 20 MHz, 512 FFT / IFFT is applied for a bandwidth of 40 MHz, 1024 FFT / IFFT is applied for a bandwidth of 80 MHz, and 2048 FFT for a bandwidth of 160 MHz continuous or discontinuous 160 MHz. / IFFT can be applied.

In other words, the subcarrier spacing / subcarrier spacing is 1 / N times the size of the subcarrier space used in the conventional WLAN system (N is a natural number, for example, 78.125 kHz when N = 4). Can be. That is, spacing may be applied to a subcarrier having a size of 312.5 kHz, which is a conventional subcarrier spacing, and space may be applied to a subcarrier having a size of 78.125 kHz, as a second field of the HE PPDU.

Alternatively, the IDFT / DFT period applied to each symbol of the first field may be expressed as N (= 4) times shorter than the IDFT / DFT period applied to each data symbol of the second field. . That is, the IDFT / DFT length applied to each symbol of the first field of the HE PPDU is 3.2 μs, and the IDFT / DFT length applied to each symbol of the second field of the HE PPDU is 3.2 μs * 4 (= 12.8 μs Can be expressed as The length of an OFDM symbol may be a value obtained by adding a length of a guard interval (GI) to an IDFT / DFT length. The length of the GI can be various values such as 0.4 μs, 0.8 μs, 1.6 μs, 2.4 μs, 3.2 μs.

For convenience of description, although the frequency band used by the first field and the frequency band used by the second field are represented in FIG. 7, they may not exactly coincide with each other. For example, the main band of the first field (L-STF, L-LTF, L-SIG, HE-SIG-A, HE-SIG-B) corresponding to the first frequency band is the second field (HE-STF). , HE-LTF, Data) is the same as the main band, but in each frequency band, the interface may be inconsistent. 4 to 6, since a plurality of null subcarriers, DC tones, guard tones, etc. are inserted in the process of arranging the RU, it may be difficult to accurately match the interface.

The user, that is, the receiving station, may receive the HE-SIG-A 730 and may be instructed to receive the downlink PPDU based on the HE-SIG-A 730. In this case, the STA may perform decoding based on the changed FFT size from the field after the HE-STF 750 and the HE-STF 750. On the contrary, if the STA is not instructed to receive the downlink PPDU based on the HE-SIG-A 730, the STA may stop decoding and configure a network allocation vector (NAV). The cyclic prefix (CP) of the HE-STF 750 may have a larger size than the CP of another field, and during this CP period, the STA may perform decoding on the downlink PPDU by changing the FFT size.

Hereinafter, in the present embodiment, data (or frame) transmitted from the AP to the STA is called downlink data (or downlink frame), and data (or frame) transmitted from the STA to the AP is called uplink data (or uplink frame). Can be expressed in terms. In addition, the transmission from the AP to the STA may be expressed in terms of downlink transmission, and the transmission from the STA to the AP may be expressed in terms of uplink transmission.

In addition, each of the PHY protocol data units (PPDUs), frames, and data transmitted through downlink transmission may be expressed in terms of a downlink PPDU, a downlink frame, and downlink data. The PPDU may be a data unit including a PPDU header and a physical layer service data unit (PSDU) (or MAC protocol data unit (MPDU)). The PPDU header may include a PHY header and a PHY preamble, and the PSDU (or MPDU) may be a data unit including a frame (or an information unit of a MAC layer) or indicating a frame. The PHY header may be referred to as a physical layer convergence protocol (PLCP) header in another term, and the PHY preamble may be expressed as a PLCP preamble in another term.

In addition, each of the PPDUs, frames, and data transmitted through uplink transmission may be represented by the term uplink PPDU, uplink frame, and uplink data.

In a WLAN system to which the present embodiment is applied, the entire bandwidth may be used for downlink transmission to one STA and uplink transmission of one STA based on single (or single) -orthogonal frequency division multiplexing (SUDM) transmission. Do. In addition, in the WLAN system to which the present embodiment is applied, the AP may perform downlink (DL) multi-user (MU) transmission based on MU MIMO (multiple input multiple output), and such transmission is DL MU MIMO transmission. It can be expressed as.

In addition, in the WLAN system according to the present embodiment, orthogonal frequency division multiple access (OFDMA) based transmission method is preferably supported for uplink transmission and downlink transmission. That is, uplink / downlink communication may be performed by allocating data units (eg, RUs) corresponding to different frequency resources to the user. Specifically, in the WLAN system according to the present embodiment, the AP performs OFDMA. DL MU transmission may be performed based on the above, and such transmission may be expressed in terms of DL MU OFDMA transmission. When DL MU OFDMA transmission is performed, the AP may transmit downlink data (or downlink frame, downlink PPDU) to each of the plurality of STAs through the plurality of frequency resources on the overlapped time resources. The plurality of frequency resources may be a plurality of subbands (or subchannels) or a plurality of resource units (RUs). DL MU OFDMA transmission can be used with DL MU MIMO transmission. For example, DL MU MIMO transmission based on a plurality of space-time streams (or spatial streams) is performed on a specific subband (or subchannel) allocated for DL MU OFDMA transmission. Can be.

In addition, in the WLAN system according to the present embodiment, UL MU transmission (uplink multi-user transmission) may be supported that a plurality of STAs transmit data to the AP on the same time resource. Uplink transmission on the overlapped time resource by each of the plurality of STAs may be performed in the frequency domain or the spatial domain.

When uplink transmission by each of the plurality of STAs is performed in the frequency domain, different frequency resources may be allocated as uplink transmission resources for each of the plurality of STAs based on OFDMA. The different frequency resources may be different subbands (or subchannels) or different resource units (RUs). Each of the plurality of STAs may transmit uplink data to the AP through different allocated frequency resources. The transmission method through these different frequency resources may be represented by the term UL MU OFDMA transmission method.

When uplink transmission by each of the plurality of STAs is performed in the spatial domain, different space-time streams (or spatial streams) are allocated to each of the plurality of STAs, and each of the plurality of STAs transmits uplink data through different space-time streams. Can transmit to the AP. The transmission method through these different spatial streams may be represented by the term UL MU MIMO transmission method.

The UL MU OFDMA transmission and the UL MU MIMO transmission may be performed together. For example, UL MU MIMO transmission based on a plurality of space-time streams (or spatial streams) may be performed on a specific subband (or subchannel) allocated for UL MU OFDMA transmission.

In a conventional WLAN system that did not support MU OFDMA transmission, a multi-channel allocation method was used to allocate a wider bandwidth (for example, a bandwidth exceeding 20 MHz) to one UE. The multi-channel may include a plurality of 20 MHz channels when one channel unit is 20 MHz. In the multi-channel allocation method, a primary channel rule is used to allocate a wide bandwidth to the terminal. If the primary channel rule is used, there is a constraint for allocating a wide bandwidth to the terminal. Specifically, according to the primary channel rule, when a secondary channel adjacent to the primary channel is used in an overlapped BSS (OBSS) and 'busy', the STA may use the remaining channels except the primary channel. Can not. Therefore, the STA can transmit the frame only through the primary channel, thereby being limited to the transmission of the frame through the multi-channel. That is, the primary channel rule used for multi-channel allocation in the existing WLAN system may be a big limitation in obtaining high throughput by operating a wide bandwidth in the current WLAN environment where there are not many OBSS.

In the present embodiment to solve this problem is disclosed a WLAN system supporting the OFDMA technology. That is, the above-described OFDMA technique is applicable to at least one of downlink and uplink. In addition, the above-described MU-MIMO technique may be additionally applied to at least one of downlink and uplink. When OFDMA technology is used, a plurality of terminals may be used simultaneously instead of one terminal without using a primary channel rule. Therefore, wide bandwidth operation is possible, and the efficiency of the operation of radio resources can be improved.

As described above, when uplink transmission by each of a plurality of STAs (eg, non-AP STAs) is performed in the frequency domain, the AP has different frequency resources for each of the plurality of STAs based on OFDMA. It may be allocated as a link transmission resource. In addition, as described above, different frequency resources may be different subbands (or subchannels) or different resource units (RUs).

Different frequency resources for each of the plurality of STAs may be indicated through a trigger frame.

8 is a block diagram showing an example of the HE-SIG-B according to the present embodiment.

As shown, the HE-SIG-B field includes a common field at the beginning, and the common field can be encoded separately from the following field. That is, as shown in FIG. 8, the HE-SIG-B field may include a common field including common control information and a user-specific field including user-specific control information. In this case, the common field may include a corresponding CRC field and may be coded into one BCC block. Subsequent user-specific fields may be coded into one BCC block, including a "user-specific field" for two users (2 users), a CRC field corresponding thereto, and the like, as shown.

9 shows an example of a trigger frame in this embodiment. The trigger frame of FIG. 9 allocates resources for uplink multiple-user transmission and can be transmitted from the AP. The trigger frame may consist of a MAC frame and may be included in a PPDU. For example, it may be transmitted through the PPDU shown in FIG. 3, through the legacy PPDU shown in FIG. 2, or through a PPDU specifically designed for the trigger frame. If transmitted through the PPDU of FIG. 3, the trigger frame may be included in the illustrated data field.

Each field shown in FIG. 9 may be partially omitted, and another field may be added. In addition, the length of each field may be varied as shown.

The frame control field 910 of FIG. 9 includes information about the version of the MAC protocol and other additional control information, and the duration field 920 includes time information for setting the NAV described below. Information about an identifier (eg, AID) of the terminal may be included.

In addition, the RA field 930 includes address information of the receiving STA of the corresponding trigger frame and may be omitted as necessary. The TA field 940 includes address information of an STA (for example, an AP) that transmits a corresponding trigger frame, and the common information field 950 is common to be applied to a receiving STA that receives the corresponding trigger frame. Contains control information

It is preferable to include per user information fields 960 # 1 to 960 # N corresponding to the number of receiving STAs receiving the trigger frame of FIG. 9. The individual user information field may be referred to as a "RU assignment field."

In addition, the trigger frame of FIG. 9 may include a padding field 970 and a frame check sequence field 980.

Each of the per user information fields 960 # 1 to 960 # N shown in FIG. 9 preferably includes a plurality of subfields.

10 shows an example of a common information field in this embodiment. Some of the subfields of FIG. 10 may be omitted, and other subfields may be added. In addition, the length of each illustrated subfield may be modified.

The illustrated length field 1010 has the same value as the length field of the L-SIG field of the uplink PPDU transmitted corresponding to the trigger frame, and the length field of the L-SIG field of the uplink PPDU indicates the length of the uplink PPDU. As a result, the length field 1010 of the trigger frame may be used to indicate the length of the corresponding uplink PPDU.

In addition, the cascade indicator field 1020 indicates whether a cascade operation is performed. The cascade operation means that downlink MU transmission and uplink MU transmission are performed together in the same TXOP. That is, after downlink MU transmission is performed, it means that uplink MU transmission is performed after a predetermined time (eg, SIFS). During the casecade operation, only one transmitting device (eg, AP) for downlink communication may exist, and a plurality of transmitting devices (eg, non-AP) for uplink communication may exist.

The CS request field 1030 indicates whether the state of the radio medium, the NAV, or the like should be considered in a situation in which the receiving apparatus receiving the trigger frame transmits the corresponding uplink PPDU.

The HE-SIG-A information field 1040 may include information for controlling the content of the SIG-A field (ie, the HE-SIG-A field) of the uplink PPDU transmitted in response to the corresponding trigger frame.

The CP and LTF type field 1050 may include information about the length of the LTF and the CP length of the uplink PPDU transmitted in response to the corresponding trigger frame. The trigger type field 1060 may indicate the purpose for which the corresponding trigger frame is used, for example, normal triggering, triggering for beamforming, a request for Block ACK / NACK, and the like.

11 shows an example of subfields included in the per user information field in this embodiment. Some of the subfields of FIG. 11 may be omitted, and other subfields may be added. In addition, the length of each illustrated subfield may be modified.

The user identifier field 1110 of FIG. 11 indicates an identifier of an STA (ie, a receiving STA) to which per user information corresponds. An example of the identifier may be all or part of an AID. have.

In addition, the RU Allocation field 1120 may be included. That is, when the receiving STA identified by the user identifier field 1110 transmits an uplink PPDU in response to the trigger frame of FIG. 9, the corresponding uplink PPDU through the RU indicated by the RU Allocation field 1120. Send. In this case, the RU indicated by the RU Allocation field 1120 preferably indicates the RUs shown in FIGS. 4, 5, and 6.

The subfield of FIG. 11 may include a coding type field 1130. The coding type field 1130 may indicate a coding type of an uplink PPDU transmitted in response to the trigger frame of FIG. 9. For example, when BCC coding is applied to the uplink PPDU, the coding type field 1130 is set to '1', and when LDPC coding is applied, the coding type field 1130 is set to '0'. Can be.

In addition, the subfield of FIG. 11 may include an MCS field 1140. The MCS field 1140 may indicate an MCS scheme applied to an uplink PPDU transmitted in response to the trigger frame of FIG. 9. For example, when BCC coding is applied to the uplink PPDU, the coding type field 1130 is set to '1', and when LDPC coding is applied, the coding type field 1130 is set to '0'. Can be.

12 is a diagram illustrating an existing OFDMA based random access procedure by way of example.

1 to 12, the horizontal axis of the AP 1200 may represent a time t of the AP 1200. The horizontal axis of the first STA 1210 represents the time t1 of the first STA 1210, the horizontal axis of the second STA 1220 represents the time t2 of the second STA 1220, and the third STA ( The horizontal axis of 1230 may represent time t3 of the third STA 1230. In addition, the vertical axis of the AP 1200 and the first to third STAs 1210, 1220, and 1230 may be associated with the existence of a frame. According to the present embodiment, contention window information (CW) information associated with a value set in an OBO counter may be signaled to a plurality of STAs through a beacon frame.

Referring to FIG. 12, an OFDMA backoff counter (hereinafter, referred to as an “OBO counter”) may be defined in each STA. The OBO counter may count down in units of resource units (RUs) indicated by trigger frames.

An OFDMA contention window (OFDMA Contention Window) may be defined, which is a range of initial values that can be set in the OBO counter based on the contention window information according to the present embodiment.

The OFDMA contention window (OCW) according to the present embodiment may be set based on contention window information included in a beacon frame (not shown) transmitted by the AP 1200. According to the present embodiment, the contention window information included in the beacon frame (not shown) may include an OCWmin value for the OCW.

For example, based on contention window information (CW) signaled to the STA through a beacon frame (not shown), the STA performing the OFDMA-based random access procedure randomizes the initial value of the OBO counter in the interval [0, OCWmin]. Can be set to the selected value.

For example, when a beacon frame (not shown) is received from the AP 1200, in order to perform an OFDMA based random access procedure, the first to second STAs 1210, 1220, and 1230 are assigned to a beacon frame (not shown). An initial value of the OBO counter of each STA may be individually set based on the included contention window information. For clarity of FIG. 12, it is assumed that a value set to an OBO counter according to contention window (CW) information included in a beacon frame (not shown) is '7'.

The first STA 1210 may set the integer value v1 arbitrarily selected in [0, CWmin] to the first OBO counter as the first initial value (OBO1). For example, the first STA 1210 may set '3' selected in [0, 7] as the first initial value (OBO1) to the first OBO counter.

The second STA 1220 may set an integer value v2 arbitrarily selected in [0, CWmin] as a second initial value (OBO2) in the second OBO counter. For example, the second STA 1220 may set '1' selected in [0, 7] to the second OBO counter as the second initial value (OBO2).

The third STA 1230 may set the integer value v3 arbitrarily selected in [0, CWmin] to the third OBO counter as the third initial value (OBO3). For example, the third STA 1230 may set '7' selected in [0, 7] as a third initial value (OBI3) to the third OBO counter.

In the present specification, a trigger frame for an OFDMA based random access procedure may be referred to as a trigger frame for random access (TR). The random access trigger frame herein follows the format of the trigger frame of FIG. 9.

In the first period T1 to T2 of FIG. 12, the AP 1200 may transmit the first random trigger frame 1201. The first random trigger frame 1201 may include allocation information indicating a plurality of resource units (RUs) allocated by the AP 1200. For example, the allocation information may indicate two resource units RU1 and RU2.

All of the first user identifier fields of the first user-specific field (eg, 960 # 1 of FIG. 9) of the first random trigger frame 1201 may be set to '0'. In addition, the first RU allocation field of the first user-specific field may be set to indicate the first resource unit (RU 1).

All of the second user identifier fields of the second user-specific field (eg, 960 # 2 of FIG. 9) of the first random trigger frame 1201 may be set to '0'. In addition, the second RU allocation field of the second user-specific field may be set to indicate the second resource unit (RU 2).

According to one embodiment of the present specification, if all of the user identifier fields of the trigger frame are set to '0', each STA that receives the trigger frame has resources indicated in the RU allocation field corresponding to the user identifier field set to '0'. The unit RU may be determined as a resource unit (RU) used for an OFDMA based random access procedure.

The first STA 1210 may perform a first countdown operation. The first STA 1210 may sequentially decrease the first initial value v1 set in the first OBO counter by the number '2' of the first and second resource units RU1 and RU2. Accordingly, the first count value v1 ′ maintained in the first OBO count becomes '1'.

The second STA 1220 may perform a second countdown operation. When the second STA 1220 decreases the second initial value v2 set in the second OBO counter only once according to the first resource unit RU1, the value v2 'of the second OBO counter is' 0'. do. Accordingly, the second countdown operation is completed.

After completing the second count operation, the second STA 1220 may select one of the RU sets RU1 and RU2 allocated to the first random trigger frame 1201 as a random resource unit. For example, the second STA 1220 may select the second resource unit RU2 as a random resource unit for transmitting the first uplink frame.

The third STA 1230 may perform a third countdown operation. The third STA 1230 may sequentially decrease the third initial value v3 set in the third OBO counter by the number '2' of the first and second resource units RU1 and RU2. Accordingly, the first count value v3 'held in the third OBO count becomes' 5'.

The second section T2 to T3 may be a short inter-frame space (SIFS).

In the third period T3 to T4, the second STA 1220 uses the random resource unit to access the HE trigger-based PPDU_1 1202 corresponding to the first random trigger frame 1201. 1200).

The fourth section T4 to T5 may be SIFS.

As illustrated in fifth periods T5 to T6, the second STA 1220 according to an embodiment of the present specification may receive the ACK frame 1203 in response to the first trigger based frame 1202. have.

In the sixth period T6 to T7, the AP 1200 and the first to third STAs 1210, 1220, and 1230 may wait.

In the seventh period T7 to T8, the AP 1200 of FIG. 12 may transmit the second random trigger frame 1204. For example, for the OFDMA-based random access procedure, the second random trigger frame 1204 may include allocation information indicating a plurality of resource units (RUs) allocated by the AP 1200. For example, the allocation information may indicate three resource units RU3, RU4, and RU5.

All of the first user identifier fields of the first user-specific field (eg, 960 # 1 of FIG. 9) of the second random trigger frame 1204 may be set to '0'. In addition, the first RU allocation field of the first user-specific field may be set to indicate the first resource unit RU3.

All of the second user identifier fields of the second user-specific field (eg, 960 # 2 of FIG. 9) of the second random trigger frame 1204 may be set to '0'. In addition, the second RU allocation field of the second user-specific field may be set to indicate the fourth resource unit RU4.

All of the third user identifier fields of the third user-specific field (eg, 960 # 3 of FIG. 9) of the second random trigger frame 1204 may be set to '0'. In addition, the third RU allocation field of the third user-specific field may be set to indicate the fifth resource unit RU5.

In a seventh period T7 to T8, the first STA 1210 may resume the first countdown operation. When the first STA 1210 decreases the first initial value v1 'maintained at the first OBO counter only once according to the third resource unit RU3, the value v1 "of the first OBO counter is' 0'. Thus, the first countdown operation is completed.

After completing the first count operation, the first STA 1210 may select one of the RU sets RU3, RU4, and RU5 allocated to the second random trigger frame 1204 as a random resource unit. For example, the first STA 1210 may select the third resource unit RU3 as a random resource unit for transmission of the second uplink frame.

The third STA 1230 may resume the third countdown operation. The third STA 1230 may sequentially decrease the third initial value v3 'maintained at the third OBO counter by the number' 3 'of the third to fifth resource units RU3 to RU5. Accordingly, the third count value v3 " held in the third OBO count becomes '2'.

The eighth section T8 to T9 may be SIFS.

In the ninth periods T9 to T10, the first STA 1210 uses the random resource unit to access the HE trigger-based PPDU_2 1205 corresponding to the second random trigger frame 1204. 1200).

The tenth section T10 to T11 may be SIFS.

As shown in the eleventh periods T11 to T12, the first STA 1210 according to an embodiment of the present specification may receive the ACK frame 1206 in response to the second trigger based frame 1205. have.

If the STA that has completed the random access procedure does not receive an ACK frame corresponding to the uplink frame transmitted through the random resource unit, in order to reduce the possibility of collision between the STAs, the STA that has not received the ACK frame transmits the uplink. It is possible to exponentially increase the range of OCW for. That is, exponentially increasing the range of OCW means increasing the counter window CW of the OBO counter to [0, 2 * OCW + 1]. Subsequently, the STA may set a randomly selected value in the increased counter window period as an initial value for the OBO counter.

13 is a conceptual diagram illustrating a service interval and a start time according to an exemplary embodiment.

1 to 13, a section between the first beacon frame BF1 and the second beacon frame BF2 may be referred to as a beacon interval. In general, an STA operating in a power save (PS) mode may receive a beacon frame in an awake state and then remain doze until the next beacon frame is received. have.

In the beacon interval of the present specification, a plurality of service periods (“SP”) may exist. The STA operating in the power save (PS) mode may maintain an awake state in the service interval SP. The STA in the awake state may receive traffic buffered in the AP from the AP. The STA in the awake state may transmit traffic buffered to the STA to the AP.

Referring to FIG. 13, first and second service intervals SP1 and SP2 may exist in a beacon interval. The first and second service intervals SP1 and SP2 of FIG. 13 may be service intervals through which the random trigger frame TR is transmitted and received.

At least one random trigger frame may be transmitted in a plurality of service intervals (SP) of the present specification. For example, in the first service period SP1, the first to third random trigger frames TR1 to TR3 may be sequentially transmitted.

The first random trigger frame TR1 may include allocation information indicating the first resource unit RU1 and the second resource unit RU2. Referring to the cascade indicator field 1020 of FIG. 10 mentioned above, the presence of a trigger frame cascaded to the first random trigger frame TR1 (in the case of FIG. 13, the second random trigger frame TR2) is described. In order to indicate, the cascade indicator included in the first random trigger frame TR1 may be set to '1'.

In order to indicate the presence of the third random trigger frame TR3, the cascade indicator CI included in the second random trigger frame TR2 may be set to '1'. In order to indicate that the random trigger frame is last transmitted in the first service period SP1, the cascade indicator CI included in the third random trigger frame TR3 may be set to '0'.

According to the present embodiment, a random trigger frame transmitted first in each service period SP may be referred to as a reference trigger frame. Random trigger frames other than a plurality of random trigger frame reference trigger frames transmitted in each service interval SP may be referred to as cascade trigger frames.

For example, the first random trigger frame TR1 transmitted in the first service period SP1 may be referred to as a first reference trigger frame for the first service period SP1. The second and third random trigger frames TR2 and TR3 may be referred to as cascade trigger frames.

In the second service period SP2 of FIG. 13, the fourth random trigger frame TR4 may be transmitted. The fourth random trigger frame TR4 may include allocation information indicating the seventh resource unit RU7 and the eighth resource unit RU8.

In order to indicate that the random trigger frame is last transmitted in the second service period SP2, the cascade indicator CI included in the fourth random trigger frame TR4 may be set to '0'.

According to the present embodiment, the fourth random trigger frame TR4 transmitted in the second service interval SP2 may be referred to as a reference trigger frame for the second service interval SP2.

According to the present embodiment, the beacon frame may include start time (hereinafter 'ST') information for the transmission time of the reference trigger frame of each service interval. For example, the first beacon frame BF1 may include first start time ST1 information and second start time ST2 information.

For example, the first start time information may indicate a transmission time of the first random trigger frame TR1 which is the first reference trigger frame of the first service period SP1. The second start time information may indicate a transmission time of the fourth random trigger frame TR4 which is the second reference trigger frame of the second service period SP2. The start time information herein is not related to the transmission time of a general trigger frame (TF).

In FIG. 13, the start time information included in the beacon frame is described as indicating the transmission time of the reference trigger frame, but the start time information may be understood as indicating the start time of the service interval.

According to the present embodiment, the STA that has received the first beacon frame BF1 may switch to the awake state in each service period based on the first and second start time information ST1 and ST2.

14 is a diagram illustrating a method for power management of a WLAN system according to an exemplary embodiment. It may be assumed that the STA 1410 of FIG. 14 operates in a power save (PS) mode.

Referring to FIG. 14, a period between a transmission time point T1 of the first beacon frame BF1 and a transmission time point T13 of the second beacon frame BF2 may be referred to as beacon intervals T1 to T13. In addition, it may be assumed that two service intervals for the random trigger frame TR exist in the beacon intervals T1 to T13.

Referring to FIG. 14, the first service section SP1 may be a section from the third time point to the eighth time points T3 to T8. The second service section SP2 may be a section from the ninth time point to the twelfth time points T9 to T12.

The first to third random trigger frames TR1 to TR3 may be transmitted in the first service period SP1. The first reference trigger frame for the first service period SP1 may be a first random trigger frame TR1. The second and third random trigger frames TR2 and TR3 may be dependent trigger frames.

As another example, the fourth random trigger frame TR4 may be transmitted in the second service period SP2. The second reference trigger frame for the second service period SP2 may be a fourth random trigger frame TR4.

1 to 14, in the first section T1 to T2. The AP 1400 may transmit the first beacon frame BF1. For example, the first beacon frame BF1 may include first contention window information CW1, first start time information ST1, and second start time information ST2. In the first period T1 to T2, the STA that receives the first beacon frame BF1 may set an initial value of the OBO counter based on the first contention window information CW1.

The competitive window (CW) information may include an OCWmin value for the OCW. For example, the OCWmin value n1 included in the first contention window information CW1 may be '10'. An STA that performs the OFDMA-based random access procedure of FIG. 14 may set an initial value of an OBO counter to a randomly selected value in the interval [0, OCWmin].

For the sake of brevity and clarity of FIG. 14, the value set in the OBO counter based on the first contention window CW1 information of the first beacon frame BF1 may be '7'.

In the first period T1 to T2, after reception of the first beacon frame BF1, the STA 1410 may switch from the awake state to the sleep state.

In the second period T2 to T3, the STA 1410 may maintain a sleep state.

In the third period T3 to T4, the AP 1400 may transmit the first random trigger frame TR1. For example, the first random trigger frame TR1 may include allocation information indicating the first and second resource units RU1 and RU2. In order to indicate the presence of the dependent trigger frame (eg, TR2), the cascade indicator CI of the first random trigger frame TR1 may be set to '1'.

According to the present embodiment, the first random trigger frame TR1 includes first quantity information (#) regarding the total number n1 of resource units RUs allocated for the random access procedure in the first service interval SP1. RU1).

In the present specification, the quantity information # RU1 regarding the total number n of resource units RUs allocated for the random access procedure is determined by the number of minimum resource units RUs that can be allocated by the AP according to an embodiment. The number of allocated maximum resource units (RU) may be indicated.

Referring to FIG. 14, the total number n1 of resource units RUs for the random access procedure allocated in the first service intervals SP1 and T3 to T8 may be '6'.

In the third period T3 to T4, the STA 1410 may switch from the sleep state to the awake state based on the first start time information ST1. In the third period T3 to T4, the STA 1410 may receive the first random trigger frame TR1.

The STA 1410 according to the present embodiment may perform a comparison operation based on the value '7' set in the OBO counter and the first quantity information # RU1 ('6' in FIG. 14). Accordingly, the STA 1410 may determine in advance that the countdown operation of the OBO counter cannot be completed in the first service period SP1. The STA 1410 may update the value '7' set in the OBO counter to a value '1' reduced by the first quantity information # RU1 ('6' in FIG. 14).

The STA 1410 according to the present embodiment may determine that the countdown operation of the OBO counter is not completed in the third period T3 to T4. Therefore, the STA 1410 may switch to the sleep state after the third section T3 to T4.

Referring to FIG. 14, dependent trigger frames TR2 and TR3 of the first service interval SP1 are transmitted in the fifth interval T5 to T6 and the sixth interval T6 to T7. However, the STA 1410 according to the present embodiment may not switch to the awake state in order to receive the dependent trigger frames TR2 and TR3.

According to an embodiment of the present disclosure, the STA 1410 may maintain the sleep state without switching to the awake state after determining that the countdown operation cannot be completed in the first service period SP1. Accordingly, power that is unnecessaryly consumed by the STA can be effectively reduced.

In the eighth section T8 to T9, the STA 1410 may maintain a sleep state.

In the ninth periods T9 to T10, the AP 1400 may transmit a fourth random trigger frame TR4. For example, the fourth random trigger frame TR4 may include allocation information indicating the seventh and eighth resource units RU7 and RU8. Since there is no dependent trigger frame in the second service intervals SP2 and T9 to T12, the cascade indicator CI of the fourth random trigger frame TR4 may be set to '0'.

According to the present embodiment, the fourth random trigger frame TR4, which is the second reference trigger frame for the second service interval SP2, of the resource unit RU allocated by the AP 1400 for the random access procedure The second quantity information # RU2 of the total number n2 may be included.

Referring to FIG. 14, the total number n2 of resource units RU for the random access procedure allocated in the second service intervals SP2 and T9 to T11 may be '2'.

In the ninth periods T9 to T10, the STA 1410 may switch from the sleep state to the awake state based on the second start time information ST2. In the ninth periods T9 to T10, the STA 1410 may receive a fourth random trigger frame TR4.

The STA 1410 according to an embodiment may perform a comparison operation based on the value '1' maintained in the OBO counter and the second quantity information # RU2 ('2' in FIG. 14). Accordingly, the STA 1410 may determine that the countdown operation of the OBO counter may be completed in the second service period SP2. The STA 1410 may update the value '1' held in the OBO counter to the value '0' that has completed the countdown.

After completing the count operation, the STA 1410 may select one of the RU sets RU7 and RU8 allocated to the fourth random trigger frame TR4 as a random resource unit. For example, the STA 1410 may select the seventh resource unit RU7 as a random resource unit for transmitting an uplink frame (UL DATA).

The STA 1410 according to the present embodiment may determine in advance that the countdown operation of the OBO counter is completed in the ninth periods T9 to T10. Accordingly, the STA 1410 may maintain the awake state without switching to the sleep state after the ninth periods T9 to T10.

The tenth section T10 to T11 may be SIFS.

In the eleventh periods T11 to T12, the STA 1410 may transmit an UL frame corresponding to the fourth random trigger frame TR4 to the AP 1400 using a random resource unit. Although not shown in FIG. 14, the eleventh periods T11 to T12 may be sections in which the STA 1410 receives an ACK frame in response to an uplink frame (UL DATA).

In the twelfth periods T12 to T13, the STA 1410 may switch to a sleep state. Subsequently, the STA 1410 may maintain a sleep state until the reception of the second beacon frame BF2.

According to an embodiment of the present disclosure, the STA that receives the reference trigger frame may obtain quantity information that is the total number of resource units (RUs) for the random access procedure allocated in the service interval. Accordingly, the STA that receives the reference trigger frame may maintain the sleep state until the next service interval without having to switch to the awake state in order to receive the dependent trigger frame transmitted in the same service period. That is, according to the present embodiment, a power management method capable of reducing power consumption by the STA may be provided.

15 is a flowchart illustrating a method for power management of a WLAN system according to an exemplary embodiment.

1 to 15, in step S1510, the STA starts contention window information for an OBO counter of orthogonal frequency division multiple access (OFDMA) based random access and a start time of a service interval for OFDMA based random access. A beacon frame including information may be received from an access point (AP).

For example, the beacon frame may include first start time ST1 information for the first service section SP1 and second start time ST2 information for the second service section SP2.

In step S1520, the STA may receive a first reference trigger frame from the AP based on the first start time ST1 information in the first service period SP1. The first reference trigger frame may include allocation information indicating a plurality of resource units allocated by the AP. The first reference trigger frame may include first quantity information # RU1 regarding the total number of resource units to be allocated during the first service interval.

In step S1530, the STA counts in the first service interval SP1 based on the first value according to the first quantity information # RU1 and the second value set in the OBO counter of the STA according to the contention window information. It may be determined whether the down operation can be completed. The STA may update the OBO counter to a value obtained by decreasing the second value by the first value. If the STA determines that the countdown operation cannot be completed in the first service period SP1, step S1540 is performed.

In step S1540, the STA may switch from the awake state to the sleep state. Subsequently, the STA may maintain a sleep state until the second service period SP2 regardless of whether a dependent trigger frame is present in the first service period SP1. In operation S1540, the STA may maintain a sleep state until the second reference trigger frame of the second service period SP2 is received. If the STA determines that the countdown operation can be completed in the first service period SP1, step S1550 is performed.

In step S150, after receiving the first reference trigger frame, the STA may maintain an awake state.

16 is a diagram illustrating a method for power management of a WLAN system according to another exemplary embodiment.

Referring to FIG. 16, it may be assumed that the STA 1610 operates in a power save (PS) mode. Referring to FIG. 16, a period between a transmission time point T1 of the first beacon frame BF1 and a transmission time point T9 of the second beacon frame BF2 may be referred to as beacon intervals T1 to T9.

Referring to FIG. 16, it may be assumed that two service intervals SP1 and SP2 exist for the random trigger frame TR in the beacon intervals T1 to T9. The first service section SP1 may be a section from the third time point to the sixth time points T3 to T6. The second service section SP2 may be a section from the seventh time point to the eighth time points T7 to T8.

It may be assumed that one service period SP3 for the random trigger frame TR exists in the beacon intervals T9 to T15. The third service section SP3 may be a section from the eleventh time point to the fourteenth time points T11 to T14.

For example, the first and second random trigger frames TR1 and TR2 may be transmitted in the first service period SP1. The first reference trigger frame for the first service period SP1 may be a first random trigger frame TR1. The second random trigger frame TR2 may be a dependent trigger frame.

In the second service period SP2, the third random trigger frame TR3 may be transmitted. The second reference trigger frame for the second service period SP2 may be a third random trigger frame TR3.

In the third service period SP3, the fourth random trigger frame TR4 may be transmitted. The thirtieth reference trigger frame for the third service interval SP3 may be a fourth random trigger frame TR4.

1 to 16, in the first period T1 to T2, the STA 1610 may receive the first beacon frame BF1 from the AP 1600. For example, the first beacon frame BF1 may include first contention window information CW1, first start time information ST1, and second start time information ST2.

Furthermore, the first beacon frame BF1 according to another embodiment of FIG. 16 is first quantity information about the total number n1 of resource units RUs allocated for the random access procedure in the beacon intervals T1 to T9. It may further include (# RU1).

In the first period T1 to T2, the STA 1610 that receives the first beacon frame BF1 may set an initial value of the OBO counter based on the first contention window CW1 information.

The contention window information CW may include an OCWmin value for the OCW. For example, the OCWmin value r1 included in the first contention window information CW1 may be '10'. An STA that performs the OFDMA-based random access procedure of FIG. 16 may set an initial value of an OBO counter to a randomly selected value in the interval [0, OCWmin].

For brevity and clarity of FIG. 16, the value set in the OBO counter according to the first contention window CW1 information included in the first beacon frame BF1 may be '7'.

In the first section T1 to T2, the STA 1610 according to another embodiment of the present disclosure is based on the value '7' set in the OBO counter and the first quantity information # RU1 ('6' in FIG. 16). The comparison operation can be performed.

Accordingly, the STA 1610 may determine in advance that the countdown operation of the OBO counter cannot be completed in the beacon intervals T1 to T9. The STA 1610 may update the value '7' set in the OBO counter to a value '1' reduced by the first quantity information # RU1 ('6' in FIG. 16). After the first period T1 to T2, the STA 1610 according to the present embodiment may switch to a sleep state.

The STA 1610 may maintain a sleep state without switching to an awake state in order to receive the second random trigger frame TR2 during the remaining periods T4 to T6 of the first service period SP1. In the sixth period T6 to T7, the STA 1610 may maintain a sleep state for a while.

In addition, the STA 1610 may maintain a sleep state without switching to an awake state in order to receive the third random trigger frame TR3 of the second service period SP2 in the seventh period T7 to T8. . In the eighth period T8 to T9, the STA 1610 may maintain a sleep state for a while.

In the ninth section T9-T10. The STA 1610 may receive the second beacon frame BF2 from the AP 1600. For example, the second beacon frame BF2 may include second contention window information CW2 and third start time information ST3.

In addition, the second beacon frame BF2 according to another embodiment of FIG. 16 is the total number of resource units RU allocated for the random access procedure in the beacon intervals T9 to T15 corresponding to the second beacon frame BF2. The first quantity information # RU2 regarding the number n2 may be included.

The STA 1610 that has not completed the countdown operation in the previous beacon intervals T1 to T9 may resume the countdown operation based on the value '1' maintained in the OBO counter. That is, the STA 1610 does not newly set the value maintained in the OBO counter based on the second contention window information CW2 included in the second beacon frame BF2.

In the ninth section T9-T10. The STA 1610 may determine in advance that the countdown operation of the OBO counter may be completed at the beacon intervals T9 to T15. The STA 1610 may update the value '1' held in the OBO counter to a value '0' reduced according to the second quantity information # RU1 ('2' in FIG. 16). After the ninth section T9 to T10, the STA 1610 according to the present embodiment may switch to a sleep state.

In the tenth period T10 to T11, the STA 1610 may maintain a sleep state.

In the eleventh periods T11 to T12, the STA 1610 may switch from the sleep state to the awake state based on the third start time information ST3. In the eleventh periods T11 to T12, the STA 1610 may receive a fourth random trigger frame TR4.

After completing the count operation, the STA 1610 may select one of the RU sets RU7 and RU8 allocated to the fourth random trigger frame TR4 as a random resource unit. For example, the STA 1610 may select the seventh resource unit RU7 as a random resource unit for transmitting an uplink frame (UL DATA).

The twelfth section T12 to T13 may be SIFS.

In the thirteenth periods T13 to T14, the STA 1610 may transmit an UL frame corresponding to the fourth random trigger frame TR4 to the AP 1600 using a random resource unit. Although not shown in FIG. 16, the thirteenth periods T13 to T14 may be sections in which the STA 1610 receives an ACK frame in response to an uplink frame (UL DATA).

In the fourteenth period T14 to T15, the STA 1610 may switch to the sleep state at the fourteenth time point T14 and maintain the sleep state until the next beacon interval.

In the embodiment of FIG. 16, quantity information on the total number of resource units (RUs) allocated for a random access procedure during a beacon interval is transmitted through a beacon frame. Accordingly, the STA that receives the beacon frame may perform a comparison operation based on a value set in the OBO counter and a value according to quantity information. In the case of FIG. 16, the STA may determine whether to switch to the sleep state after receiving the beacon frame.

In contrast, according to the embodiment of FIG. 14, quantity information of the total number of resource units RUs allocated for the random access procedure is included in the reference trigger frame of each service interval SP.

According to the embodiment of FIG. 16, since the determination of the time at which the STA enters the sleep state is performed quickly, there is an advantage in that power consumed by the STA can be minimized. In addition, according to the embodiment of Figure 14, there is an advantage in terms of flexibility (flexibility) according to the change of the image.

Referring to FIGS. 1 through 16 mentioned above, methods for reducing the power consumed by the STA by signaling the total number of resource units (RUs) allocated for the OFDMA random access procedure are mentioned.

In various situations, the AP may not be able to precalculate quantity information to be included in the random trigger frame TR or the beacon frame. In the present specification, when the total number of resource units (RUs) allocated for the random access procedure is not calculated, it may be referred to as an unknown state.

According to the present embodiment, in order to notify the unknown state, the AP may allocate '0' to a field for quantity information among subfields of the beacon frame or the random trigger frame TR. Accordingly, the STA that receives the beacon frame or the random trigger frame TR having '0' set in the quantity information may determine that the AP cannot receive information on the number of resource units (RUs). Alternatively, the STA that receives the beacon frame or the random trigger frame TR having the maximum value set in the quantity information may determine that the AP cannot receive information about the number of resource units (RUs).

17 is a diagram illustrating a method for power management of a WLAN system according to another embodiment.

12 to 16 described above, contention window information for OCW is included only in a beacon frame. However, in the description of FIG. 17, it is assumed that the contention window information is included in the random trigger frame TR as well as the beacon frame.

Referring to FIG. 17, the first random trigger frame 1701 according to another embodiment may include first contention window information CW1 allocated by the AP 1700. Similarly, the second random trigger frame 1704 may include second contention window information CW2 allocated by the AP 1700.

If the STA simultaneously receives contention window (CW) information for setting the OCW range from the beacon frame and the random trigger frame (TR), the STA may select a smaller value for the OBO counter.

12 and 17, in the first period T1 to T2 of FIG. 17, the AP 1700 may transmit a first trigger frame 1701. It will be appreciated that the process of setting an initial value in the OBO counter of each STA may be replaced with the description of FIG. 12.

The first random trigger frame 1701 may include allocation information indicating a plurality of resource units (RUs). For example, the allocation information may indicate two resource units RU1 and RU2.

The first STA 1710 may perform a first countdown operation. The first STA 1710 may sequentially decrease the first initial value v1 set in the first OBO counter by the number '2' of the first and second resource units RU1 and RU2. Accordingly, the first count value v1 ′ maintained in the first OBO count becomes '1'.

The second STA 1720 may perform a second countdown operation. When the second STA 1720 decreases the second initial value v2 set in the second OBO counter only once according to the first resource unit RU1, the value v2 'of the second OBO counter is' 0'. do. Accordingly, the second countdown operation is completed.

After completing the second count operation, the second STA 1720 may select one of the RU sets RU1 and RU2 allocated to the first random trigger frame 1701 as a random resource unit. For example, the second STA 1720 may select the second resource unit RU2 as a random resource unit for transmission of the first uplink frame.

The third STA 1730 may perform a third countdown operation. The third STA 1730 may sequentially decrease the third initial value v3 set in the third OBO counter by the number '2' of the first and second resource units RU1 and RU2. Accordingly, the first count value v3 'held in the third OBO count becomes' 5'.

The second section T2 to T3 may be a short inter-frame space (SIFS).

In the third period T3 to T4, the second STA 1720 uses the random resource unit to access the HE trigger-based PPDU_1 1702 corresponding to the first random trigger frame 1701. 1700).

The fourth section T4 to T5 may be SIFS.

As illustrated in the fifth period T5 to T6, the second STA 1720 according to an embodiment of the present specification may not receive the ACK frame 1703 in response to the first trigger based frame 1702. Can be. In this case, an operation for setting an initial value of the OBO counter of the second STA 1720 may be as follows.

For example, the second STA 1720 may determine a section for the initial value of the OBO counter based on the value r1 according to the first contention window CW1 information included in the first random trigger frame 1701 [0, 2 * r1 + 1]. Subsequently, the second STA 1720 may set an integer value randomly selected from [0, 2 * r1 + 1] as an initial value (#) of the OBO counter.

For example, the second STA 1720 may determine an initial value of the OBO counter at [0, r1] based on the value r1 according to the first contention window CW1 information included in the first random trigger frame 1701. You can select #) again.

For example, the second STA 1720 may determine a section for the initial value of the OBO counter based on the value r2 according to the second contention window (CW2) information included in the second random trigger frame 1704 [0, 2 * r2 + 1]. Subsequently, the second STA 1720 may set an integer value randomly selected from [0, 2 * r2 + 1] as an initial value (#) of the OBO counter.

For example, the second STA 1720 includes the value (2 * r1 + 1) and the second random trigger frame 1704 that have exponentially increased the value r1 included in the first random trigger frame 1701. One of the lower values (r2) can be set as the initial value (#) of the OBO counter.

For example, the second STA 1720 includes the value (2 * r1 + 1) and the second random trigger frame 1704 that have exponentially increased the value r1 included in the first random trigger frame 1701. The larger value of the set value r2 can be set as the initial value (#) of the OBO counter.

In addition, although not shown through FIG. 17, the STA 1720 that does not receive the ACK frame may select a section for the initial value of the OBO counter based on the value w1 included in the most recently received beacon frame [0, 2 * w1 + 1]. Subsequently, the second STA 1720 may set an integer value randomly selected from [0, 2 * w1 + 1] as an initial value (#) of the OBO counter.

As another example, the second STA 1720 may again select the initial value (#) of the OBO counter at [0, w1] based on the value w1 included in the most recently received beacon frame.

As another example, the interval for the initial value of the OBO counter may be increased to [0, 2 * w2 + 1] based on the second contention window value w2 included in the most recently received beacon frame. Subsequently, the second STA 1720 may set an integer value randomly selected from [0, 2 * w2 + 1] as an initial value (#) of the OBO counter.

As another example, the second STA 1720 may be configured to exponentially increase the value w2 included in the most recently received beacon frame (2 * w2 + 1) and the value included in the most recently received beacon frame. The smaller value of the value w1 may be set as an initial value (#) of the OBO counter.

As another example, the second STA 1720 may be configured to exponentially increase the value w2 included in the most recently received beacon frame (2 * w2 + 1) and the value included in the most recently received beacon frame. A larger value of the value w1 may be set as an initial value (#) of the OBO counter.

18 is a block diagram illustrating a wireless terminal to which an embodiment can be applied.

Referring to FIG. 18, a wireless terminal may be an STA that may implement the above-described embodiment and may be an AP or a non-AP STA. The wireless terminal may correspond to the above-described user or may correspond to a transmitting terminal for transmitting a signal to the user.

The AP 1800 includes a processor 1810, a memory 1820, and a radio frequency unit 1830.

The RF unit 1830 may be connected to the processor 1810 to transmit / receive a radio signal.

The processor 1810 may implement the functions, processes, and / or methods proposed herein. For example, the processor 1810 may perform an operation according to the present embodiment described above. The processor 1810 may perform an operation of the AP disclosed in the present embodiment of FIGS. 1 to 17.

The non-AP STA 1850 includes a processor 1860, a memory 1870, and a radio frequency unit (RF) 1880.

The RF unit 1880 may be connected to the processor 1860 to transmit / receive a radio signal.

The processor 1860 may implement the functions, processes, and / or methods proposed in the present embodiment. For example, the processor 1860 may be implemented to perform the non-AP STA operation according to the present embodiment described above. The processor 1860 may perform the operation of the non-AP STA disclosed in the present embodiment of FIGS. 1 to 17.

Processors 1810 and 1860 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, data processing devices, and / or converters for interconverting baseband signals and wireless signals. The memories 1820 and 1870 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices. The RF unit 1830 and 1880 may include one or more antennas for transmitting and / or receiving a radio signal.

When the present embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. Modules may be stored in memories 1820 and 1870 and executed by processors 1810 and 1860. The memories 1820 and 1870 may be inside or outside the processors 1810 and 1860, and may be connected to the processors 1810 and 1860 by various well-known means.

In the detailed description of the present specification, specific embodiments have been described, but various modifications are possible without departing from the scope of the present specification. Therefore, the scope of the present specification should not be limited to the above-described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims of the present invention.

Claims (10)

1. In the method for power management in a wireless LAN system,

   Contention window information for a backoff counter of orthogonal frequency division multiple access (OFDMA) based random access and a start time of a service period for the OFDMA based random access receiving a beacon frame including time information from an access point (AP);

   The user STA receives a reference trigger frame from the AP in the service period based on the start time information, wherein the reference trigger frame includes allocation information indicating a plurality of resource units; Including quantity information about the total number of resource units to be allocated during the service interval; And

   The user STA determines whether to switch from an awake state to a doze state based on a first value according to the quantity information and a second value set in the backoff counter according to the contention window information. Method comprising the steps of:
2. The method of claim 1,

   Determining whether to switch to the sleep state,

   If the second value is greater than the first value, the user STA transitioning from the awake state to the sleep state after receiving the reference trigger frame; And

   The user STA maintaining the sleep state until a second reference trigger frame is received.
3. The method of claim 2,

   The beacon frame further includes second start time information for a second service interval,

   The second reference trigger frame is a frame received by the user STA in the second service interval based on the second start time information.
4. The method of claim 1,

   The reference trigger frame is a frame in which '0' is set in association identification information corresponding to the plurality of resource units.
5. The method of claim 1,

   And updating, by the user STA, the backoff count to a third value that is reduced from the second value by the first value.
6. The method of claim 1,

   The trigger reference trigger frame further includes a dependency indicator indicating the existence of a dependent trigger frame dependent on the reference trigger frame in the service interval.
7. The method of claim 6,

   When the dependent trigger frame exists in the reference trigger frame, the dependent trigger frame is a frame including second allocation information indicating a plurality of second resource units,

   The quantity information is set to a sum of the number of the plurality of resource units and the number of the plurality of second resource units.
8. The method of claim 1,

   After receiving the beacon frame, the user station further comprises transitioning from the awake state to the sleep state.
9. The method of claim 1,

   The user STA is a STA operating in a power save mode.
10. In a wireless terminal using a method for transmitting an uplink frame in a wireless LAN system, the wireless terminal,

    A transceiver for transmitting and receiving a radio signal; And

    A processor coupled to the transceiver, wherein the processor includes:

    Beacon including contention window information for backoff counter of orthogonal frequency division multiple access (OFDMA) based random access and start time information of a service period for the OFDMA based random access Is configured to receive a frame from an access point,

    The reference trigger frame may be configured to receive a reference trigger frame from the AP in the service section based on the start time information, wherein the reference trigger frame includes allocation information indicating a plurality of resource units and the service section. Includes quantity information about the total number of resource units to be allocated during the

    And determining whether to switch from an awake state to a doze state based on a first value according to the quantity information and a second value set in the backoff counter according to the contention window information.

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