WO2018190599A1 - Method for performing retransmission in wireless lan system and wireless terminal using same - Google Patents

Abstract

A method for performing retransmission in a wireless LAN system performed by an access point (AP) according to an embodiment comprises the steps of: transmitting a first wake-up packet for a plurality of wireless terminals comprising a plurality of main radio modules and a plurality of wake-up radio (WUR) modules, wherein the first wake-up packet instructs the plurality of main radio modules to enter an activated state, and the first wake-up packet is modulated in accordance with an on-off keying (OOK) technique; and, if at least one PS-poll frame is not received from at least one wireless terminal among the plurality of wireless terminals as a response to the first wake-up packet, transmitting, on the basis of OFDMA, a second wake-up packet for at least one wireless terminal and a downlink packet for the main radio modules, wherein the second wake-up packet is modulated in accordance with an OOK technique.

Description

Method for performing retransmission in wireless LAN system and wireless terminal using same

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

Discussion is underway for the next generation wireless local area network (WLAN). In next-generation WLANs, 1) enhancements to the Institute of Electronics and Electronics Engineers (IEEE) 802.11 physical physical access (PHY) and medium access control (MAC) layers in the 2.4 GHz and 5 GHz bands, and 2) spectral efficiency and area throughput. aims to improve performance in real indoor and outdoor environments, such as in environments where interference sources exist, dense heterogeneous network environments, and high user loads.

The environment mainly considered in the next-generation WLAN is a dense environment having many access points (APs) and a station (STA), and improvements in spectral efficiency and area throughput are discussed in such a dense environment. In addition, in the next generation WLAN, there is an interest in improving practical performance not only in an indoor environment but also in an outdoor environment, which is not much considered in a conventional WLAN.

Specifically, in next-generation WLANs, we are interested in scenarios such as wireless office, smart-home, stadium, hot spot, building / apartment and based on the scenario. As a result, there is a discussion about improving system performance in a dense environment with many APs and STAs.

In addition, in the next-generation WLAN, there will be more discussion about improving system performance in outdoor overlapping basic service set (OBSS) environment, improving outdoor environment performance, and cellular offloading, rather than improving single link performance in one basic service set (BSS). It is expected. The directionality of these next-generation WLANs means that next-generation WLANs will increasingly have a technology range similar to that of mobile communications. Considering the recent situation in which mobile communication and WLAN technology are discussed together in the small cell and direct-to-direct (D2D) communication area, the technical and business convergence of next-generation WLAN and mobile communication is expected to become more active.

An object of the present specification is to provide a method for performing retransmission in a WLAN system having an improved performance and a wireless terminal using the same.

A method of performing retransmission in a WLAN system performed by an access point (AP) according to the present embodiment includes a plurality of main radio modules and a plurality of wake-up radio (WUR) modules. Transmit a first wake-up packet for the wireless terminal, wherein the first wake-up packet instructs the plurality of main radio modules to enter an active state, and the first wake-up packet is OOK (On-Off). Modulated according to a Keying) technique; And a second wakeup packet for at least one wireless terminal and the main radio when at least one PS-poll frame is not received in response to a first wakeup packet from at least one wireless terminal among a plurality of wireless terminals. Transmitting a downlink packet for the module on an OFDMA basis, wherein the second wake-up packet is modulated according to the OOK technique.

According to the present specification, a method for performing retransmission in a WLAN system having improved performance and a wireless 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 shows an internal block diagram of a wireless terminal receiving a wakeup packet.

5 is a conceptual diagram illustrating a method for a wireless terminal to receive a wakeup packet and a data packet.

6 shows an example of a format of a wakeup packet.

7 shows a signal waveform of a wakeup packet.

FIG. 8 is a diagram for describing a procedure of determining power consumption according to a ratio of bit values constituting information in a binary sequence form.

9 is a diagram illustrating a design process of a pulse according to the OOK technique.

FIG. 10 is a diagram illustrating a case where a plurality of wireless terminals perform power management according to a wakeup packet for a plurality of wireless terminals.

11 illustrates various cases of managing power of a wireless terminal based on wakeup packets for a plurality of wireless terminals.

12 and 13 illustrate a method of performing retransmission in the WLAN system according to the present embodiment.

14 is a diagram illustrating a method of performing retransmission in a WLAN system according to another exemplary embodiment.

FIG. 15 is a diagram illustrating a method for retransmission in a WLAN system according to another embodiment.

16 is a conceptual diagram illustrating a method of performing retransmission based on OFDMA in a WLAN system according to an embodiment.

17 is a flowchart illustrating a method of performing retransmission in the WLAN system according to the present embodiment.

18 is a block diagram illustrating a wireless device to which the present embodiment can be applied.

19 is a block diagram illustrating an example of an apparatus included in a processor.

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, in the present embodiment, the signal to be improved 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 the present 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.).

The PPDU used in the IEEE standard is mainly described as a PPDU structure transmitted over a channel bandwidth of 20 MHz. The PPDU structure transmitted over a wider bandwidth (eg, 40 MHz, 80 MHz) than the channel bandwidth of 20 MHz may be a structure applying linear scaling to the PPDU structure used in the 20 MHz channel bandwidth.

The PPDU structure used in the IEEE standard is generated based on 64 Fast Fourier Tranforms (FTFs), and a CP portion (cyclic prefix portion) may be 1/4. In this case, the length of the effective symbol interval (or FFT interval) may be 3.2us, the CP length is 0.8us, and the symbol duration may be 4us (3.2us + 0.8us) plus the effective symbol interval and the CP length.

4 shows an internal block diagram of a wireless terminal receiving a wakeup packet.

Referring to FIG. 4, the WLAN system 400 according to the present embodiment may include a first wireless terminal 410 and a second wireless terminal 420.

The first wireless terminal 410 includes a main radio module 411 associated with the main radio (ie, 802.11) and a low-power wake-up receiver ('LP WUR') (hereinafter, WUR). Module 412. The main radio module 411 may transmit user data or receive user data in an activated state (ie, an ON state).

When there is no data (or packet) to be transmitted by the main radio module 411, the first radio terminal 410 may control the main radio module 411 to enter an inactive state (ie, an OFF state). For example, the main radio module 411 may include a plurality of circuits supporting Wi-Fi, Bluetooth® radio (hereinafter referred to as BT radio) and Bluetooth® low energy radio (hereinafter referred to as BLE radio).

According to the related art, a wireless terminal operating based on a power save mode may operate in an active state or a sleep state.

For example, a wireless terminal in an activated state can receive all frames from another wireless terminal. In addition, the wireless terminal in the sleep state may periodically wake up and receive a particular type of frame (e.g., beacon frame transmitted periodically) transmitted by another wireless terminal (e.g., AP).

It is assumed that the wireless terminal referred to herein can operate the main radio module in an activated state or in an inactive state.

A wireless terminal that includes a main radio module 411 in an inactive state (i.e., in an OFF state) may be of any type transmitted by another wireless terminal (e.g., AP) until the main radio module is woken up by the WUR module 412. Also cannot receive frames (eg, 802.11 type PPDUs).

In other words, the wireless terminal including the main radio module 411 in an inactive state (ie, in an OFF state) cannot receive beacon frames periodically transmitted by the AP.

That is, it may be understood that the wireless terminal including the main radio module (eg, 411) in the inactive state (ie, the OFF state) according to the present embodiment is in a deep sleep state.

In addition, a wireless terminal that includes a main radio module 411 in an active state (ie, an ON state) may receive all types of frames (eg, 802.11 type PPDUs) transmitted by other wireless terminals (eg, APs). Can be received.

In addition, it is assumed that the wireless terminal referred to herein can operate the WUR module in a turn-off state or in a turn-on state.

When the WUR module 412 is in the turn-on state, the wireless terminal can only receive certain types of frames transmitted by other wireless terminals. In this case, a specific type of frame may be understood as a frame modulated according to an On-Off Keying (OOK) modulation scheme described below with reference to FIG. 5.

When the WUR module 412 is in the turn-off state, the wireless terminal may not receive any type of frame transmitted by the other wireless terminal.

In this specification, to indicate the ON state of a specific module included in the wireless terminal, the terms for the activation state and the turn-on state may be used interchangeably. In the same context, the terms deactivation state and turn-off state may be used interchangeably to indicate an OFF state of a particular module included in the wireless terminal.

The wireless terminal according to the present embodiment may receive a frame (or packet) from another wireless terminal based on the main radio module 411 in the activated state or the WUR module 412 in the turn-on state.

The WUR module 412 may be a receiver for waking the main radio module 411. That is, the WUR module 412 may not include a transmitter. The WUR module 412 may be turned on in a section in which the main radio module 411 is in an inactive state.

For example, when a wake-up packet (WUP) for the main radio module 411 is received, the first radio terminal 410 may be configured to have a main radio module 411 in an inactive state. It can be controlled to enter the activation state.

The low power wake up receiver (LP WUR) included in the WUR module 412 targets a target power consumption of less than 1 mW in an active state. In addition, low power wake-up receivers may use a narrow bandwidth of less than 5 MHz.

In addition, the power consumption by the low power wake-up receiver may be less than 1 Mw. In addition, the target transmission range of the low power wake-up receiver may be the same as the target transmission range of the existing 802.11.

The second wireless terminal 420 may transmit user data based on the main radio (ie, 802.11). The second wireless terminal 420 can transmit a wakeup packet (WUP) for the WUR module 412.

The second wireless terminal 420 may not transmit user data or a wakeup packet (WUP) for the first wireless terminal 410. In this case, the main radio module 411 included in the second wireless terminal 420 may be in an inactive state (ie, an OFF state), and the WUR module 412 is in a turn-on state (ie, an ON state). There may be.

5 is a conceptual diagram illustrating a method for a wireless terminal to receive a wakeup packet and a data packet.

4 and 5, the WLAN system 500 according to the present embodiment may include a first wireless terminal 510 corresponding to the receiving terminal and a second wireless terminal 520 corresponding to the transmitting terminal. have. Basic operations of the first wireless terminal 510 of FIG. 5 may be understood through the description of the first wireless terminal 410 of FIG. 4. Similarly, the basic operation of the second wireless terminal 520 of FIG. 5 may be understood through the description of the second wireless terminal 420 of FIG. 4.

Referring to FIG. 5, when a wakeup packet 521 is received based on the WUR module 512 in an active state (ie, an ON state), the WUR module 512 wakes up to wake up the main radio module 511. The signal 523 may be transmitted to the main radio module 511.

For example, the wakeup signal 523 may be implemented based on primitive information inside the first wireless terminal 510.

For example, when the main radio module 511 receives the wake-up signal 523, all of the plurality of circuits (not shown) supporting Wi-Fi, BT radio, and BLE radio included in the main radio module 511 may be provided. It can be activated or only part of it.

As another example, the actual data included in the wakeup packet 521 may be directly transmitted to a memory block (not shown) of the receiving terminal even if the main radio module 511 is in an inactive state.

As another example, when the wake-up packet 521 includes an IEEE 802.11 MAC frame, the receiving terminal may activate only the MAC processor of the main radio module 511. That is, the receiving terminal may maintain the PHY module of the main radio module 511 in an inactive state. The wakeup packet 521 of FIG. 5 will be described in more detail with reference to the following drawings.

The second wireless terminal 520 can transmit the wakeup packet 521 to the first wireless terminal 510. That is, in order to control the main radio module 511 of the first wireless terminal 510 to enter the activated state (that is, the ON state), the second wireless terminal 520 may transmit the wakeup packet 521. have.

6 shows an example of a format of a wakeup packet.

1 to 6, the wakeup packet 600 may include one or more legacy preambles 610. For example, the legacy preamble 610 may be modulated according to an existing Orthogonal Frequency Division Multiplexing (OFDM) modulation technique.

In addition, the wakeup packet 600 may include a payload 620 after the legacy preamble 610. For example, payload 620 may be modulated according to a simple modulation scheme (eg, On-Off Keying (OOK) modulation technique. Wakeup packet 600 including payload) May be transmitted based on a relatively small bandwidth.

1 through 6, a second wireless terminal (eg, 520) may be configured to generate and / or transmit wakeup packets 521, 600. The first wireless terminal (eg, 510) can be configured to process the received wakeup packet 521.

The wakeup packet 600 may include a legacy preamble 610 or any other preamble (not shown) defined in the existing IEEE 802.11 standard.

The wakeup packet 600 may include one packet symbol 615 after the legacy preamble 610. In addition, the wakeup packet 600 may include a payload 620.

The legacy preamble 610 may be provided for coexistence with the legacy STA. In other words, the legacy preamble 610 may be provided for a third party STA (ie, a STA that does not include an LP-WUR). That is, the legacy preamble 610 may not be decoded by the WUR terminal including the WUR module.

In the legacy preamble 610 for coexistence, an L-SIG field for protecting a packet may be used. For example, an 802.11 STA may detect a start portion of a packet (ie, a start portion of a wakeup packet) through an L-STF field in the legacy preamble 610. The L-SIG field in the legacy preamble 610 may allow the 802.11 STA to know the last part of the packet (ie, the last part of the wakeup packet).

In order to reduce false alarm of the 802.11n terminal, a modulated symbol 615 may be added after the L-SIG of FIG. 6. One symbol 615 may be modulated according to a BiPhase Shift Keying (BPSK) technique. One symbol 615 may have a length of 4 us. One symbol 615 may have a 20 MHz bandwidth like a legacy part.

Payload 620 includes a wake-up preamble field 621, a MAC header field 623, a frame body field 625, and a Frame Check Sequence (FCS) field 627. can do.

The wakeup preamble field 621 may include a sequence for identifying the wakeup packet 600. For example, the wakeup preamble field 621 may include a pseudo random noise sequence (PN).

The MAC header field 624 may include address information (or an identifier of a receiving apparatus) indicating a receiving terminal receiving the wakeup packet 600. The frame body field 626 may include other information of the wakeup packet 600.

The frame body 626 may include length information or size information of the payload. Referring to FIG. 6, the length information of the payload may be calculated based on length LENGTH information and MCS information included in the legacy preamble 610.

The FCS field 628 may include a Cyclic Redundancy Check (CRC) value for error correction. For example, the FCS field 628 may include a CRC-8 value or a CRC-16 value for the MAC header field 623 and the frame body 625.

7 shows a signal waveform of a wakeup packet.

Referring to FIG. 7, the wakeup packet 700 may include payloads 722 and 724 modulated based on a legacy preamble (802.11 preamble, 710) and an On-Off Keying (OOK) scheme. That is, the wakeup packet WUP according to the present embodiment may be understood as a form in which a legacy preamble and a new LP-WUR signal waveform coexist.

In the legacy preamble 710 of FIG. 7, the OOK technique may not be applied. As mentioned above, payloads 722 and 724 may be modulated according to the OOK technique. However, the wakeup preamble 722 included in the payloads 722 and 724 may be modulated according to another modulation technique.

For example, it may be assumed that the legacy preamble 710 is transmitted based on a channel band of 20 MHz to which 64 FFTs are applied. In this case, payloads 722 and 724 may be transmitted based on a channel band of about 4.06 MHz.

FIG. 8 is a diagram for describing a procedure of determining power consumption according to a ratio of bit values constituting information in a binary sequence form.

Referring to FIG. 8, information in the form of a binary sequence having '1' or '0' as a bit value may be represented. Communication based on the OOK modulation scheme may be performed based on the bit values of the binary sequence information.

For example, when the light emitting diode is used for visible light communication, when the bit value constituting the binary sequence information is '1', the light emitting diode is turned on, and when the bit value is '0', the light emitting diode is turned off. (off) can be turned off.

As the light-emitting diode blinks, the receiver receives and restores data transmitted in the form of visible light, thereby enabling communication using visible light. However, since the blinking of the light emitting diode cannot be perceived by the human eye, the person feels that the illumination is continuously maintained.

For convenience of description, as shown in FIG. 8, information in the form of a binary sequence having 10 bit values may be provided. For example, information in the form of a binary sequence having a value of '1001101011' may be provided.

As described above, when the bit value is '1', when the transmitting terminal is turned on and when the bit value is '0', when the transmitting terminal is turned off, 6 bit values of the above 10 bit values are applied. The corresponding symbol is turned on.

Since the wake-up receiver WUR according to the present embodiment is included in the receiving terminal, the transmission power of the transmitting terminal may not be greatly considered. The reason why the OOK technique is used in the present embodiment is because power consumption in the decoding procedure of the received signal is very small.

Until the decoding procedure is performed, there may be no significant difference between the power consumed by the main radio and the power consumed by the WUR. However, as the decoding procedure is performed by the receiving terminal, a large difference may occur between power consumed by the main radio module and power consumed by the WUR module. Below is the approximate power consumption.

-The existing Wi-Fi power consumption is about 100mW. Specifically, power consumption of Resonator + Oscillator + PLL (1500uW)-> LPF (300uW)-> ADC (63uW)-> decoding processing (OFDM receiver) (100mW) may occur.

-WUR power consumption is about 1mW. Specifically, power consumption of Resonator + Oscillator (600uW)-> LPF (300uW)-> ADC (20uW)-> decoding processing (Envelope detector) (1uW) may occur.

9 is a diagram illustrating a design process of a pulse according to the OOK technique.

The wireless terminal according to the present embodiment may use an existing 802.11 OFDM transmitter to generate a pulse according to the OOK technique. The existing 802.11 OFDM transmitter can generate a sequence having 64 bits by applying a 64-point IFFT.

1 to 9, the wireless terminal according to the present embodiment may transmit a payload of a wakeup packet (WUP) modulated according to the OOK technique. The payload (eg, 620 of FIG. 6) according to the present embodiment may be implemented based on an ON time signal and an OFF time signal.

The OOK technique may be applied to the ON time signal included in the payload (eg, 620 of FIG. 6) of the wakeup packet WUP. In this case, the on time signal may be a signal having an actual power value.

Referring to the frequency domain graph 920, the on-time signal included in the payload (eg, 620 of FIG. 6) may be selected from among N1 subcarriers (N1 is a natural number) corresponding to the channel band of the wakeup packet (WUP). It can be obtained by performing IFFT on N2 subcarriers (N2 is a natural number). In addition, a predetermined sequence may be applied to the N2 subcarriers.

For example, the channel band of the wakeup packet WUP may be 20 MHz. The N1 subcarriers may be 64 subcarriers, and the N2 subcarriers may be 13 consecutive subcarriers (921 of FIG. 9). The subcarrier interval applied to the wakeup packet (WUP) may be 312.5 kHz.

The OOK technique may be applied to the OFF time signal included in the payload (eg, 620 of FIG. 6) of the wakeup packet WUP. The off time signal may be a signal that does not have an actual power value. That is, the off time signal may not be considered in the configuration of the wakeup packet WUP.

The on time signal included in the payload (620 of FIG. 6) of the wakeup packet (WUP) is a 1-bit ON signal (ie, a 1-bit ON signal) by the WUR module (eg, 512 of FIG. 5). '1'), i.e., demodulation. Similarly, the off time signal included in the payload may be determined (ie, demodulated) as a 1-bit off signal (ie, '0') by the WUR module (eg, 512 of FIG. 5).

A specific sequence may be preset for the subcarrier set 921 of FIG. 9. In this case, the preset sequence may be a 13-bit sequence. For example, a coefficient corresponding to the DC subcarrier in the 13-bit sequence may be '0', and the remaining coefficients may be set to '1' or '-1'.

Referring to the frequency domain graph 920, the subcarrier set 921 may correspond to a subcarrier having a subcarrier index of '-6' to '+6'.

For example, a coefficient corresponding to a subcarrier whose subcarrier indices are '-6' to '-1' in the 13-bit sequence may be set to '1' or '-1'. A coefficient corresponding to a subcarrier whose subcarrier indices are '1' to '6' in the 13-bit sequence may be set to '1' or '-1'.

For example, a subcarrier whose subcarrier index is '0' in a 13-bit sequence may be nulled. The coefficients of the remaining subcarriers (subcarrier indexes '-32' to '-7' and subcarrier indexes '+7' to '+31') except for the subcarrier set 921 are all set to '0'. Can be.

The subcarrier set 921 corresponding to 13 consecutive subcarriers may be set to have a channel bandwidth of about 4.06 MHz. That is, power by signals may be concentrated at 4.06 MHz in the 20 MHz band for the wakeup packet (WUP).

By using the pulse according to the OOK technique, the power is concentrated in a specific band, so that the signal to noise ratio (SNR) can be increased, and the power consumption for conversion in the AC / DC converter of the receiver can be reduced. . Since the sampling frequency band is reduced to 4.06 MHz, power consumption by the wireless terminal can be reduced.

An OFDM transmitter of 802.11 may use IFFT (for 13 consecutive subcarriers) of N2 sub-carriers (e.g., 64 subcarriers) corresponding to the channel band (e.g., 20 MHz band) of a wake-up packet. For example, 64-point IFFT may be performed.

In this case, a predetermined sequence may be applied to the N2 subcarriers. Accordingly, one on-signal may be generated in the time domain. One bit information corresponding to one on signal may be transmitted through one symbol.

For example, when a 64-point IFFT is performed, a symbol having a 3.2us length corresponding to the subcarrier set 921 may be generated. In addition, when CP (Cyclic Prefix, 0.8us) is added to a symbol having a 3.2us length corresponding to the subcarrier set 921, one symbol having a total length of 4us as shown in the time domain graph 910 of FIG. Can be generated.

In addition, the OFDM transmitter of 802.11 may not transmit the off signal at all.

According to the present embodiment, a first wireless terminal (eg, 510 of FIG. 5) including a WUR module (eg, 512 of FIG. 5) may receive a packet based on an envelope detector that extracts an envelope of the received signal. Can be demodulated.

For example, the WUR module (eg, 512 of FIG. 5) according to the present embodiment may compare a power level of a received signal obtained through an envelope of the received signal with a preset threshold level.

If the power level of the received signal is higher than the threshold level, the WUR module (eg, 512 of FIG. 5) may determine the received signal as a 1-bit ON signal (ie, '1'). If the power level of the received signal is lower than the threshold level, the WUR module (eg, 512 of FIG. 5) may determine the received signal as a 1-bit OFF signal (ie, '0').

According to the present embodiment, the basic data rate for one information may be 125 Kbps (8us) or 62.5Kbps (16us).

Generalizing the contents of FIG. 9, each signal having a length of K (eg, K is a natural number) in the 20 MHz band may be transmitted based on consecutive K subcarriers of 64 subcarriers for the 20 MHz band. For example, K may correspond to the number of subcarriers used to transmit the signal. K may also correspond to the bandwidth of a pulse according to the OOK technique.

All of the coefficients of the remaining subcarriers except K subcarriers among the 64 subcarriers may be set to '0'.

Specifically, for the 1-bit off signal corresponding to '0' (hereinafter, information 0) and the 1-bit on signal corresponding to '1' (hereinafter, information 1), the same K subcarriers may be used. have. For example, the index for the K subcarriers used may be expressed as 33-floor (K / 2): 33 + ceil (K / 2) -1.

In this case, the information 1 and the information 0 may have the following values.

Information 0 = zeros (1, K)

Information 1 = alpha * ones (1, K)

The alpha is a power normalization factor and may be, for example, 1 / sqrt (K).

For simplicity and clarity of understanding herein, the main radio module (eg, 511 of FIG. 5, 1311 of FIG. 5) of the wireless terminal (eg, 510 of FIG. 5) is in an inactive state (ie, OFF state), When the WUR module (eg, 512 of FIG. 5) is in the turn-on state (ie, in the ON state), it may be said that the wireless terminal operates in the WUR mode or the low power mode.

Furthermore, the main radio module (e.g., 511 of FIG. 5, 1311 of FIG. 13) of the wireless terminal (e.g., 510 of FIG. 5) is in an active state (i.e., an ON state), and the WUR module (e.g., 512 of FIG. 5). May be said to operate in the normal mode when the < RTI ID = 0.0 >

FIG. 10 is a diagram illustrating a case where a plurality of wireless terminals perform power management according to a wakeup packet for a plurality of wireless terminals.

Referring to FIG. 10, the horizontal axis of the AP 1000 may represent a time ta, and the vertical axis may be associated with the existence of a frame to be transmitted by the AP 1000.

The first WUR terminal 1010 may include first main radio modules WUR m1 and 1011 and first WUR modules WUR w1 and 1012. For example, the first main radio module 1011 may correspond to the main radio module 511 of FIG. 5. The first WUR module 1012 may correspond to the WUR module 512 of FIG. 5.

The horizontal axis of the first main radio module 1011 may represent time tm1. In addition, an arrow displayed at the lower end of the horizontal axis of the first main radio module 1011 may indicate a power state (eg, an ON state or an OFF state) of the first main radio module 1011. The vertical axis of the first main radio module 1011 may be associated with the presence of a frame to be transmitted by the first main radio module 1011.

The horizontal axis of the first WUR module 1012 may represent the time tw1. In addition, an arrow displayed at the lower end of the horizontal axis of the first WUR module 1012 may indicate a power state (eg, an ON state or an OFF state) of the first WUR module 1012. The vertical axis of the first WUR module 1012 may be associated with the presence of a frame to be transmitted by the first WUR module 1012.

The second WUR terminal 1020 may include a second main radio module (WUR m2, 1021) and a second WUR module (WUR w2, 1022). For example, the second main radio module 1021 may correspond to the main radio module 511 of FIG. 5. The second WUR module 1022 may correspond to the WUR module 512 of FIG. 5.

The horizontal axis of the second main radio module 1021 may represent time tm2. In addition, an arrow displayed at a lower end of the horizontal axis of the second main radio module 1021 may indicate a power state (eg, an ON state or an OFF state) of the second main radio module 1022. The longitudinal axis of the second main radio module 1022 may be associated with the presence of a frame to be transmitted by the second main radio module 1022.

The horizontal axis of the second WUR module 1022 may represent a time tw2. In addition, an arrow displayed at a lower end of the horizontal axis of the second WUR module 1022 may indicate a power state (eg, an ON state or an OFF state) of the second WUR module 1022. The vertical axis of the second WUR module 1022 may be associated with the presence of a frame to be transmitted by the second WUR module 1022.

The third WUR terminal 1030 may include a third main radio module (WUR m3, 1031) and a third WUR module (WUR w3, 1032). For example, the third main radio module 1031 may correspond to the main radio module 511 of FIG. 5. The third WUR module 1032 may correspond to the WUR module 512 of FIG. 5.

The horizontal axis of the third main radio module 1031 may represent time tm3. In addition, an arrow displayed at a lower end of the horizontal axis of the third main radio module 1031 may indicate a power state (eg, an ON state or an OFF state) of the third main radio module 1031. The vertical axis of the third main radio module 1031 may be associated with the presence of a frame to be transmitted by the third main radio module 1031.

The horizontal axis of the third WUR module 1032 may represent the time tw3. In addition, an arrow displayed at the lower end of the horizontal axis of the third WUR module 1032 may indicate a power state (eg, an ON state or an OFF state) of the third WUR module 1032. The vertical axis of the third WUR module 1032 may be associated with the presence of a frame to be transmitted by the third WUR module 1032.

In FIG. 10, the plurality of WUR terminals is shown as corresponding to the first WUR terminal 1010 to the third WUR terminal 1030. However, it is to be understood that the present specification is not limited thereto.

The first WUR terminal 1010 to the third WUR terminal 1030 may be understood as a wireless terminal combined with the AP through a predetermined combining procedure.

In the wakeup periods TW to T1 of FIG. 10, the first main radio module 1011 of the first WUR terminal 1010 is in an inactive state (ie, an OFF state), and the first WUR module 1012 is turned on. It can be assumed to be in the on state (ie, in the ON state).

In addition, the second main radio module 1021 of the second WUR terminal 1020 is in an inactive state (i.e., an OFF state), and the second WUR module 1022 is in a turn-on state (i.e., an ON state). Can assume

In addition, the third main radio module 1031 of the third WUR terminal 1030 is in an inactive state (i.e., an OFF state), and the third WUR module 1032 is in a turn-on state (i.e., an ON state). Can assume

In the wakeup periods TW to T1 of FIG. 10, the AP 1000 may transmit a wake-up packet (hereinafter, “WUP”). For example, the wakeup packet (WUP) of FIG. 10 is a plurality of main radio modules (eg, 1021. 1023 may instruct to enter the activated state.

As another example, the wakeup packet WUP may instruct all main radio modules corresponding to all WUR terminals receiving the wakeup packet WUP to enter an activated state according to a broadcast scheme.

The wakeup packet WUP of FIG. 10 may include a first payload modulated according to an on-off keying (OOK) technique for the first WUR module 1012. For example, the first payload is an ON signal determined as a 1-bit ON signal by the first WUR module 1012 and 1 bit OFF by the first WUR module 1012. The signal may be generated based on an off signal determined as a signal.

The first payload may be transmitted based on a first subchannel belonging to a channel band (eg, 20 MHz) corresponding to N (eg, 64) subcarriers. The first subchannel may be implemented based on N1 (eg, 13) subcarriers among N (eg, 64) subcarriers.

For example, the ON signal included in the first payload may be configured for N1 (eg, 13) subcarriers among N (eg, 64) subcarriers corresponding to the channel band of the wakeup packet (WUP). Can be obtained by performing an Inverse Fast Fourier Transform (IFFT).

In addition, the wakeup packet WUP may include a second payload modulated according to the OOK technique for the second WUR module 1022. For example, the second payload is an ON signal determined as a 1 bit ON signal by the second WUR module 1022 and a 1 bit OFF by the second WUR module 1022. The signal may be generated based on an off signal determined as a signal.

The second payload may be transmitted based on a second subchannel belonging to a channel band (eg, 20 MHz) corresponding to N (eg, 64) subcarriers. The second subchannel may be implemented based on N2 (eg, 13) subcarriers among the N (eg, 64) subcarriers. In this case, N2 (eg, 13) subcarriers may not overlap with N1 (eg, 13) subcarriers.

In addition, the wakeup packet WUP may include a third payload modulated according to the OOK scheme for the third WUR module 1032. For example, the third payload is an ON signal determined as a 1-bit ON signal by the third WUR module 1032 and one bit OFF by the third WUR module 1032. The signal may be generated based on an off signal determined as a signal.

The third payload may be transmitted based on a third subchannel belonging to a channel band (eg, 20 MHz) corresponding to N (eg, 64) subcarriers. The third subchannel may be implemented based on N3 (eg, 13) subcarriers among the N (eg, 64) subcarriers. In this case, N3 (eg, 13) subcarriers may not overlap with N2 (eg, 13) subcarriers.

In the present specification, the main radio module 1011, 1021, 1031 is activated according to a wakeup signal (for example, 523 of FIG. 5), which is a primitive signal generated inside the WUR terminal based on the received wakeup packet (WUP). (Ie, a delay time required to enter the ON state) may be referred to as a turn-on delay (TOD).

A protection time may be introduced to reduce unnecessary overhead and delay caused by a mismatch of a power state between an AP and a WUR terminal due to a turn-on delay (TOD).

The guard time according to the wakeup packet WUP may be understood as the first period T1 to T2 of FIG. 10. In this case, the first sections T1 to T2 of FIG. 10 may be set according to a predetermined parameter for the guard time.

For example, the predetermined parameter for the guard time may be a value individually set in the combining procedure between the AP 1000 and each WUR STA (eg, 1010, 1020, 1030). For example, the guard time set in the first to third WUR STAs 1010, 1020, and 1030 of FIG. 10 may be set to have the same time interval (eg, T1 to T2 of FIG. 10).

The AP 1000 may wait without transmitting any packets until the first period T1 to T2 of FIG. 10 corresponding to the guard time elapses.

For brevity and clarity of the present embodiment, it may be assumed that each WUR terminal 1010, 1020, 1030 switches from the WUR mode to the normal mode before the first period (eg, T1 to T2) corresponding to the guard time. have.

In the second period T2 to T3 of FIG. 10, the AP 1000 may transmit a trigger frame to confirm whether the wakeup packet WUP is successfully received to each WUR terminal. The trigger frame may be a frame transmitted based on contention for the wireless channel.

The trigger frame referred to herein may be understood as a frame that triggers a plurality of uplink transmissions from a plurality of terminals. The trigger frame may include identification information about a plurality of terminals and frequency resource information allocated to each terminal. For further details on the trigger frame referred to herein, reference may be made to section 9.3.1.23 of the standard document IEEE P802.11ax / D2.1 disclosed in January 2018.

In the second period T2 to T3 of FIG. 10, the plurality of WUR terminals 1010, 1020, and 1030 may transmit a plurality of power save poll (PS-pol) frames on overlapping time resources in response to a trigger frame. Can be.

The plurality of PS-poll frames may be individually transmitted based on the main radio modules 1011, 1021, and 1031 included in each WUR terminal 1010, 1020, and 1030. The plurality of PS-pole frames may be frames transmitted when a predetermined time d elapses. In this case, the predetermined time d may be SIFS.

By transmitting a first PS-Poll (PS Poll # 1) frame to the AP 1000 in response to the trigger frame, the first WUR terminal 1010 may transmit the first main radio based on the received wake-up packet WUP. The AP 1011 may inform the AP 1000 that the module 1011 has entered an activated state (ie, an ON state). For example, the first PS Poll # 1 frame may be transmitted through a first resource unit allocated to the first WUR terminal 1010.

That is, when the first PS-Poll (PS Poll # 1) frame is received, the AP 1000 may determine that the wakeup packet WUP has been successfully received by the first WUR terminal 1010.

By transmitting a second PS-Poll (PS Poll # 2) frame to the AP 1000 in response to the trigger frame, the second WUR terminal 1020 receives the second main radio module according to the received wake-up packet WUP. The AP 1000 may be notified that 1021 has entered an activated state (ie, an ON state). For example, a second PS Poll # 2 frame may be transmitted through a second resource unit allocated to the second WUR terminal 1020.

That is, when the second PS-Poll (PS Poll # 2) frame is received, the AP 1000 may determine that the wakeup packet WUP has been successfully received by the second WUR terminal 1020.

By transmitting a third PS-Pol (PS Poll # 3) frame to the AP 1000 in response to the trigger frame, the third WUR terminal 1030 may transmit a third main radio module according to the received wake-up packet WUP. The AP 1000 may be informed that the 1031 has entered an activated state (ie, an ON state). For example, the third PS-Poll (PS Poll # 3) frame may be transmitted through a third resource unit allocated to the third WUR terminal 1030.

That is, when the third PS-Poll (PS Poll # 3) frame is received, the AP 1000 may determine that the wakeup packet WUP has been successfully received by the third WUR terminal 1030.

Subsequently, in order to inform successful reception of the first to third PS-Poll (PS Poll # 3) frames, the AP 1000 may determine a predetermined time after receiving the first to third PS-Poll (PS Poll # 3) frames. When d) elapses, an acknowledgment (ACK) frame may be transmitted. In this case, the predetermined time d may be SIFS.

In addition, the ACK frame of FIG. 10 may be received by each of the WUR terminals 1010, 1020, and 1030 based on the first to third main radio modules 1011, 1021, and 1031 in an activated state (that is, an ON state). .

11 illustrates various cases of managing power of a wireless terminal based on wakeup packets for a plurality of wireless terminals.

In the wakeup periods TW to T1 of FIG. 11, the first main radio module 1111 of the first WUR terminal 1110 is in an inactive state (ie, an OFF state), and the first WUR module 1112 is turned on. It can be assumed to be in the on state (ie, in the ON state).

In addition, the second main radio module 1121 of the second WUR terminal 1120 is in an inactive state (i.e., an OFF state), and the second WUR module 1122 is in a turn-on state (i.e., an ON state). Can assume

In addition, the third main radio module 1131 of the third WUR terminal 1130 is in an inactive state (ie, an OFF state), and the third WUR module 1132 is in a turn-on state (ie, an ON state). Can assume

1 to 11, it may be assumed that the first WUR terminal 1110 does not receive a wakeup packet (WUP) due to an external factor (eg, a channel condition). According to the above assumption, the first WUR terminal 1110 of FIG. 11 may maintain the WUR mode in the first section T1 to T2 and the second section T2 to T3. In this case, the first WUR terminal 1110 may not receive a trigger frame transmitted by the AP 1100.

It may be assumed that the second WUR terminal 1120 receives a wake up packet (WUP). According to the above assumption, before the first intervals T1 to T2 corresponding to the guard time pass, the second WUR terminal 1120 of FIG. 11 may switch from the WUR mode to the normal mode.

However, in the second period T2 to T3, it may be assumed that the second WUR terminal 1120 does not receive a trigger frame transmitted by the AP 1000 due to an external factor (for example, a channel condition). According to the above assumption, the second WUR terminal 1120 of FIG. 11 may maintain the normal mode in the second period T2 to T3 without additional packet transmission.

It may be assumed that the third WUR terminal 1130 receives the wakeup packet (WUP). According to the above assumption, before the elapse of the first periods T1 to T2 corresponding to the guard time, the third WUR terminal 1130 of FIG. 11 may switch from the WUR mode to the normal mode.

In addition, it may be assumed that the third WUR terminal 1130 receives a trigger frame transmitted by the AP 1000 in the second period T2 to T3. According to the above assumption, the third WUR terminal 1130 of FIG. 11 may transmit the third PS poll frame PS Poll # 3 in response to the trigger frame.

However, it may be assumed that the third PS poll frame PS Poll # 3 is not properly received by the AP 1000 due to external factors (eg, channel conditions). According to the above assumption, the third WUR terminal 1130 of FIG. 11 receives an ACK frame for the third PS poll frame (PS Poll # 3) from the AP while maintaining the normal mode in the second intervals T2 to T3. Can not.

According to the present specification, when a PS-poll frame is not received in response to a wakeup packet (WUP) for a plurality of WUR terminals, the AP 1100 determines exactly why the PS-poll frame is not received. It can be difficult to judge.

12 and 13 illustrate a method of performing retransmission in the WLAN system according to the present embodiment.

For clarity and simplicity, it may be understood that the APs 1200 and 1300 illustrated in FIGS. 12 and 13 correspond to the AP 1100 mentioned in FIG. 11. In addition, the WUR terminals 1210 and 1310 illustrated in FIGS. 12 and 13 may be understood to correspond to the first WUR terminal 1110 among the plurality of WUR terminals mentioned in FIG. 11.

Referring to FIG. 12, in the wakeup periods TW to T1 of FIG. 12, the AP 1200 may transmit a first wakeup packet WUP # 1. For example, the first wakeup packet WUP # 1 of FIG. 12 is activated by a plurality of main radio modules included in a plurality of WUR terminals including the WUR terminal 1210 of FIG. 12 according to a multicast scheme. To enter a state (ie, an ON state).

As another example, the first wakeup packet WUP # 1 of FIG. 12 is activated by all main radio modules corresponding to all WUR terminals that have received the first wakeup packet WUP # 1 according to a broadcast scheme. To enter a state (ie, an ON state).

The first wakeup packet WUP # 1 of FIG. 12 may include a plurality of payloads modulated according to an on-off keying (OOK) technique for the plurality of WUR modules.

In the wakeup periods TW to T1 of FIG. 12, the main radio module 1211 of the WUR terminal 1210 is in an inactive state (ie, an OFF state), and the WUR module 1212 is in a turn-on state (ie, ON state).

However, it may be assumed that the WUR terminal 1210 does not receive the first wakeup packet WUP # 1 due to an external factor (for example, a channel condition). According to the above assumption, the WUR terminal 1210 of FIG. 12 may maintain the WUR mode for the first period T1 to T2 corresponding to the guard time of the first wakeup packet WUP # 1.

In the second period T2 to T3 of FIG. 12, at least one PS-pol frame may not be received from at least one WUR terminal among the plurality of WUR terminals indicated by the first wakeup packet WUP # 1. have.

For example, it may be assumed that a PS-poll frame is not received from the WUR terminal 1210 of FIG. 12 among a plurality of WURs indicated by the first wakeup packet WUP # 1.

In the second period T2 to T3 of FIG. 12, the AP 1200 determines whether the first wakeup packet WUP # 1 is successfully received for the plurality of WUR terminals transmitted in the wakeup period TW to T1. A trigger frame can be sent to confirm.

In the present specification, the trigger frame may trigger a plurality of PS-poll frames from a plurality of WUR terminals that have successfully received the first wakeup packet WUP # 1. In this case, the trigger frame and the PS-poll frame may be transmitted and received based on the main radio module of the WUR terminal.

In the second periods T2 to T3 of FIG. 12, the WUR terminal 1210 may maintain a WUR mode. That is, the WUR terminal 1210 may not receive a trigger frame transmitted by the AP 1200.

As mentioned above, it is difficult for the AP 1200 to determine whether at least one PS-pole frame is not received from at least one WUR terminal due to some cause.

In the second period T2 to T3 of FIG. 12, the AP may determine that at least one PS-pol frame is not received from at least one WUR terminal among the plurality of WUR terminals. In this case, the AP may retransmit the first wakeup packet WUP # 1.

For example, the AP 1200 may determine that a PS-poll frame is not received from the WUR terminal 1210 of FIG. 12 among a plurality of WUR terminals. In this case, the AP 1200 may perform retransmission of the first wakeup packet WUP # 1.

In order to retransmit the first wakeup packet WUP # 1, the AP may select a second wakeup packet WUP # 2 for at least one WUR terminal and at least one main radio module included in the at least one WUR terminal. The downlink packet may be transmitted together based on an orthogonal frequency division multiplexing access (OFDMA).

For example, the AP 1200 may include a second wakeup packet WUP # 2 for the WUR module 1212 included in the WUR terminal 1210 and a main radio module 1211 included in the WUR terminal 1210. Null data packet (NDP) for the same may be transmitted on the basis of OFDMA.

Here, the null data packet NDP may mean a packet that does not include a data field in the packet.

In the present embodiment, a trigger frame for triggering at least one uplink transmission from at least one wireless terminal may be transmitted in place of a null data packet NDP.

Referring to FIG. 12, the second wakeup packet WUP # 2 and the null data packet NDP may be transmitted in overlapping time resources. In the second periods T2 to T3 of FIG. 12, the WUR terminal 1210 may operate in a WUR mode. Accordingly, the WUR terminal 1210 may receive the second wakeup packet WUP # 2.

The third section T3 to T4 of FIG. 12 may be understood as a time section corresponding to the guard time of the second wakeup packet WUP # 2.

Before the third period T3 to T4 of FIG. 13 elapses, the WUR terminal 1210 of FIG. 12 may switch from the WUR mode to the normal mode according to the received wakeup packet WUP # 2.

In the third period T3 to T4 of FIG. 12, the WUR terminal 1210 may transmit a PS-poll frame to the AP 1200 in response to the received second wakeup packet WUP # 2. In this case, the PS-poll frame may be transmitted based on the main radio module 1211 in an active state (ie, in an ON state).

By receiving the PS-poll frame, the AP 1200 may know that the WUR terminal 1210 operates in the normal mode. Subsequently, the AP 1200 may transmit an ACK frame in response to the PS-poll frame. In this case, it will be appreciated that the ACK frame may be received based on the main radio module 1211 of the WUR terminal 1210.

Referring to FIG. 13, in the wakeup periods TW to T1 of FIG. 13, the AP may transmit first wakeup packets WUP # 1 for a plurality of WUR terminals. For example, the first wakeup packet WUP # 1 of FIG. 13 includes a plurality of mains included in a plurality of WUR terminals (not shown) including the WUR terminal 1310 of FIG. 13 according to a multicast scheme. The radio module may be instructed to enter an activated state (ie, an ON state).

As another example, the first wakeup packet WUP # 1 of FIG. 13 is activated by all main radio modules corresponding to all WUR terminals receiving the first wakeup packet WUP # 1 according to a broadcast scheme. To enter a state (ie, an ON state).

The first wakeup packet WUP # 1 of FIG. 13 may include a plurality of payloads modulated according to an on-off keying (OOK) technique for a plurality of WUR modules.

In the wakeup periods TW to T1 of FIG. 13, the main radio module 1311 of the WUR terminal 1310 is in an inactive state (ie, an OFF state), and the WUR module 1312 is in a turn-on state (ie, ON state).

For example, it may be assumed that the WUR terminal 1310 of FIG. 13 does not receive the first wakeup packet WUP # 1 due to an external factor (eg, a channel condition). According to the above assumption, the WUR terminal 1310 of FIG. 13 may maintain the WUR mode for the first period T1 to T2 corresponding to the guard time of the first wakeup packet WUP # 1.

In the second period T2 to T3 of FIG. 13, at least one PS-pol frame may not be received from at least one WUR terminal among the plurality of WUR terminals indicated by the first wakeup packet WUP # 1. have.

For example, the PS-poll frame may not be received from the WUR terminal 1310 of FIG. 13 among the plurality of WURs indicated by the first wakeup packet WUP # 1. In this case, the AP 1300 may perform retransmission for the first wakeup packet WUP # 1 without transmitting a separate trigger frame.

In the second period T2 to T3 of FIG. 13, in order to retransmit the first wakeup packet WUP # 1, the AP 1300 may transmit a plurality of WURs indicated by the first wakeup packet WUP # 1. A second wakeup packet (WUP # 2) for at least one WUR terminal and a downlink packet for at least one main radio module included in the at least one WUR terminal may be transmitted together based on OFDMA.

For example, in the second period T2 to T3 of FIG. 13, the second wakeup packet WUP # 2 and the WUR terminal 1310 for the WUR module 1312 included in the WUR terminal 1310 are included in the WUR terminal 1310. A null data packet (NDP) for the main radio module 1311 may be transmitted based on OFDMA. In the second period T2 to T3 of FIG. 13, the WUR terminal 1310 may operate in the WUR mode. Accordingly, the WUR terminal 1310 may receive the second wakeup packet WUP # 2.

According to the above assumption, before the third section T3 to T4 of FIG. 13 passes, the WUR terminal 1210 of FIG. 12 may switch from the WUR mode to the normal mode.

In the present embodiment, a trigger frame for triggering at least one uplink transmission from at least one wireless terminal may be transmitted in place of a null data packet NDP.

In the fourth period T4 to T5 of FIG. 13, at least one WUR terminal may transmit at least one PS-poll frame to the AP 1300 in response to the second wakeup packet WUP # 2. .

For example, the WUR terminal 1310 may transmit a PS-poll frame to the AP 1300 in response to the received second wakeup packet WUP # 2. As an example, the PS-poll frame may be transmitted on a contention basis for the wireless channel. For example, the PS-poll frame may be transmitted based on the main radio module 1311 that is in an active state (ie, in an ON state).

By receiving at least one PS-poll frame, the AP 1300 may know that at least one WUR terminal operates in a normal mode. Subsequently, the AP 1300 may transmit at least one ACK frame in response to the at least one PS-poll frame.

For example, the AP 1300 may transmit an ACK frame in response to the PS-poll frame received from the WUR terminal 1310 in response to the AP 1300. In this case, it will be appreciated that the ACK frame may be received based on the main radio module 1311 of the WUR terminal 1310.

14 is a diagram illustrating a method of performing retransmission in a WLAN system according to another exemplary embodiment.

For clarity and simplicity, it may be understood that the AP 1400 illustrated in FIG. 14 corresponds to the AP 1100 mentioned in FIG. 11. In addition, it may be understood that the WUR terminal 1410 illustrated in FIG. 14 corresponds to the second WUR terminal 1120 among the plurality of WUR terminals mentioned in FIG. 11.

Referring to FIG. 14, in the wakeup periods TW to T1 of FIG. 14, the AP 1400 may transmit a first wakeup packet WUP # 1. For example, the first wakeup packet WUP # 1 of FIG. 14 is activated by a plurality of main radio modules included in a plurality of WUR terminals including the WUR terminal 1410 of FIG. 14 according to a multicast scheme. To enter a state (ie, an ON state).

As another example, the first wakeup packet WUP # 1 of FIG. 14 is activated by all main radio modules corresponding to all WUR terminals that have received the first wakeup packet WUP # 1 according to a broadcast scheme. To enter a state (ie, an ON state).

The first wakeup packet WUP # 1 of FIG. 14 may include a plurality of payloads modulated according to an on-off keying (OOK) technique for the plurality of WUR modules.

In the wakeup periods TW-T1 of FIG. 14, the main radio module 1411 of the WUR terminal 1410 is in an inactive state (ie, an OFF state), and the WUR module 1412 is in a turn-on state (ie, ON state). It may be assumed that the WUR terminal 1410 receives the first wakeup packet WUP # 1.

The first periods T1 to T2 of FIG. 14 may be understood as time periods corresponding to the guard time of the first wakeup packet WUP # 1. Before the first period T1 to T2 of FIG. 14 passes, the WUR terminal 1410 of FIG. 14 may switch from the WUR mode to the normal mode according to the received first wakeup packet WUP # 1.

In the second period T2 to T3 of FIG. 14, the AP 1400 determines whether the first wakeup packet WUP # 1 is successfully received for the plurality of WUR terminals transmitted in the wakeup period TW to T1. A trigger frame can be sent to confirm.

The trigger frame of FIG. 14 may trigger a plurality of PS-poll frames from a plurality of WUR terminals that have successfully received the first wakeup packet WUP # 1. In this case, the trigger frame may be transmitted and received based on the main radio module of the WUR terminal.

In the second period T2 to T3 of FIG. 14, the WUR terminal 1210 may maintain a normal mode. However, it may be assumed that the WUR terminal 1410 of FIG. 14 does not receive a trigger frame due to an external factor (for example, a channel condition).

In the second period T2 to T3 of FIG. 14, the AP 1400 may include at least one PS-pol frame from at least one WUR terminal among the plurality of WUR terminals indicated by the first wakeup packet WUP # 1. Can be determined not to be received. In this case, the AP 1400 may perform retransmission of the first wakeup packet WUP # 1.

In order to retransmit the first wakeup packet WUP # 1, the AP may select a second wakeup packet WUP # 2 for at least one WUR terminal and at least one main radio module included in the at least one WUR terminal. The downlink packet may be transmitted together based on the OFDMA. For example, the AP 1400 may use the second wakeup packet WUP # 2 for the WUR module 1412 included in the WUR terminal 1410 and the main radio module 1411 included in the WUR terminal 1410. Null data packet (NDP) for the same may be transmitted on the basis of OFDMA.

That is, the second wakeup packet WUP # 2 and the at least one null data packet NDP may be transmitted in overlapping time resources. In the second period T2 to T3 of FIG. 14, the WUR terminal 1410 may operate in a normal mode. Accordingly, the WUR terminal 1410 may receive a null data packet NDP.

Subsequently, the WUR terminal 1410 may transmit an ACK frame in response to a null data packet. For example, the ACK frame may be transmitted based on the main radio module 1411.

In the present embodiment, a trigger frame for triggering at least one uplink transmission from at least one wireless terminal may be transmitted in place of a null data packet NDP.

FIG. 15 is a diagram illustrating a method for retransmission in a WLAN system according to another embodiment.

For clear and concise description, it may be understood that the AP 1500 shown in FIG. 15 corresponds to the AP 1100 mentioned in FIG. In addition, it may be understood that the WUR terminal 1510 illustrated in FIG. 15 corresponds to the third WUR terminal 1130 among the plurality of WUR terminals mentioned in FIG. 11.

The wakeup sections TW to T1 of FIG. 15 and the first sections T1 to T2 of FIG. 15 are described for the wakeup sections TW to T1 of FIG. 14 and the first sections T1 to T2 of FIG. 14. Can be understood on the basis of

Referring to FIG. 15, at least one PS-pole from at least one WUR terminal among a plurality of WUR terminals indicated by the first wakeup packet WUP # 1 in the second period T2 to T3 of FIG. 15. The frame may not be received.

For example, the WUR terminal 1510 indicated by the first wakeup packet WUP # 1 may transmit a PS-poll frame to inform the AP 1500 of operating in normal mode. However, it may be assumed that the AP 1500 may not receive the PS-poll frame due to external factors (eg, channel conditions).

In this case, the AP 1500 may perform retransmission for the first wakeup packet WUP # 1 without transmitting a separate trigger frame.

In order to retransmit the first wakeup packet WUP # 1, the AP may select a second wakeup packet WUP # 2 for at least one WUR terminal and at least one main radio module included in the at least one WUR terminal. The downlink packet may be transmitted together based on the OFDMA.

For example, the AP 1500 may include a second wakeup packet WUP # 2 for the WUR module 1512 included in the WUR terminal 1510 and a main radio module 1511 included in the WUR terminal 1510. Null data packet (NDP) for the same may be transmitted on the basis of OFDMA.

That is, the second wakeup packet WUP # 2 and the at least one null data packet NDP may be transmitted in overlapping time resources. In the second period T2 to T3 of FIG. 15, the WUR terminal 1510 may operate in a normal mode. Accordingly, the WUR terminal 1510 may receive a null data packet NDP.

Subsequently, the WUR terminal 1510 may transmit an ACK frame in response to a null data packet. For example, the ACK frame may be transmitted based on the main radio module 1511.

Also, in the present specification, a trigger frame for triggering at least one uplink transmission from at least one wireless terminal may be transmitted in place of a null data packet (NDP).

As described above with reference to FIGS. 12 to 15, the AP may transmit a wakeup packet (WUP) and a null data packet (NDP) together for retransmission based on OFDMA.

Accordingly, the WUR terminal targeted for retransmission may receive one of the wakeup packet (WUP) and the null data packet (NDP) and then reply to the corresponding packet to the AP. That is, the AP can accurately determine the power state of the WUR terminal to be retransmitted. According to the present embodiment, it will be appreciated that unnecessary power consumed by the WUR terminal may be reduced.

16 is a conceptual diagram illustrating a method of performing retransmission based on OFDMA in a WLAN system according to an embodiment.

The horizontal axis of FIG. 16 represents a time domain and the vertical axis represents a frequency domain.

The header of FIG. 16 may be transmitted based on the entire bandwidth of a specific band. For example, the overall bandwidth may be 20 MHz or 80 MHz.

The plurality of HE PPDUs and WUR PPDUs of FIG. 16 may be transmitted based on other frequency resources on overlapping time resources.

For example, the plurality of HE PPDUs may include a null data packet (NDP). For example, the WUR PPDU may include a wakeup packet according to retransmission.

17 is a flowchart illustrating a method of performing retransmission in the WLAN system according to the present embodiment.

Referring to FIG. 17, in step S1710, an AP is configured for a plurality of wireless terminals (ie, a plurality of WUR terminals) including a plurality of main radio modules and a plurality of wake-up radio modules. One wake-up packet may be transmitted.

For example, the first wakeup packet may instruct the plurality of main radio modules to enter an activated state. For example, the first wakeup packet may be modulated according to an on-off keying (OOK) technique.

In operation S1720, the AP may determine whether at least one PS-poll frame is received in response to the first wakeup packet from the at least one wireless terminal among a plurality of wireless terminals.

If a plurality of PS-poll frames are received from all of the plurality of wireless terminals, the procedure ends. In this case, the AP may transmit the buffered downlink data packet to the plurality of wireless terminals.

If at least one PS-pole frame is not received in response to the first wakeup packet from the at least one wireless terminal among a plurality of wireless terminals, step S1730 is performed.

In step S1730, the AP transmits a second wakeup packet for at least one wireless terminal and a downlink packet for at least one main radio module included in the at least one wireless terminal based on Orthogonal Frequency Division Multiplexing Access (OFDMA) can do.

In this case, the at least one second wakeup packet may be modulated according to the OOK technique. In this case, the downlink packet may be at least one null data packet or a trigger frame that triggers at least one uplink transmission from at least one wireless terminal.

Although not shown in FIG. 17, the operation of each wireless terminal according to retransmission of the present specification may be as follows.

For example, when the at least one wireless terminal does not receive the first wakeup packet, the second wakeup packet may be received based on at least one WUR module included in the at least one wireless terminal.

Furthermore, the AP may receive at least one PS-poll frame in response to the second wakeup packet from the at least one wireless terminal.

As another example, when at least one wireless terminal receives the first wakeup packet, the downlink packet may be received based on at least one main radio module included in the at least one wireless terminal.

Furthermore, the AP may receive at least one ACK frame in response to the downlink packet from the at least one wireless terminal.

18 is a block diagram illustrating a wireless device to which the present embodiment can be applied.

Referring to FIG. 18, a wireless device may be implemented as an AP or a non-AP STA as an STA capable of implementing the above-described embodiment. In addition, the wireless device may correspond to the above-described user, or may correspond to a transmitting terminal for transmitting a signal to the user.

The wireless device of FIG. 18 includes a processor 1810, a memory 1820 and a transceiver 1830 as shown. The illustrated processor 1810, memory 1820, and transceiver 1830 may be implemented as separate chips, or at least two blocks / functions may be implemented through one chip.

The transceiver 1830 is a device including a transmitter and a receiver. When a specific operation is performed, only one of the transmitter and the receiver may be performed, or both the transmitter and the receiver may be performed. have. The transceiver 1830 may include one or more antennas for transmitting and / or receiving wireless signals. In addition, the transceiver 1830 may include an amplifier for amplifying a received signal and / or a transmitted signal and a bandpass filter for transmission on a specific frequency band.

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. That is, the processor 1810 may perform the operation disclosed in the embodiment of FIGS. 1 to 17.

The processor 1810 may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, a data processing device, and / or a converter for translating baseband signals and wireless signals.

Memory 1820 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices.

19 is a block diagram illustrating an example of an apparatus included in a processor. For convenience of description, an example of FIG. 19 is described based on a block for a transmission signal, but it is obvious that the reception signal can be processed using the block.

The illustrated data processor 1910 generates transmission data (control data and / or user data) corresponding to the transmission signal. The output of the data processor 1910 may be input to the encoder 1920. The encoder 1920 may perform coding through a binary convolutional code (BCC) or a low-density parity-check (LDPC) technique. At least one encoder 1920 may be included, and the number of encoders 1920 may be determined according to various information (eg, the number of data streams).

The output of the encoder 1920 may be input to the interleaver 1930. The interleaver 1930 performs an operation of distributing consecutive bit signals over radio resources (eg, time and / or frequency) to prevent burst errors due to fading or the like. At least one interleaver 1930 may be included, and the number of the interleaver 1930 may be determined according to various information (eg, the number of spatial streams).

The output of the interleaver 1930 may be input to a constellation mapper 1940. The constellation mapper 1940 performs constellation mapping such as biphase shift keying (BPSK), quadrature phase shift keying (QPSK), quadrature amplitude modulation (n-QAM), and the like.

The output of the constellation mapper 1940 may be input to the spatial stream encoder 1950. The spatial stream encoder 1950 performs data processing to transmit the transmission signal through at least one spatial stream. For example, the spatial stream encoder 1950 may perform at least one of space-time block coding (STBC), cyclic shift diversity (CSD) insertion, and spatial mapping on a transmission signal.

The output of the spatial stream encoder 1950 may be input to an IDFT 1960 block. The IDFT 1660 block performs an inverse discrete Fourier transform (IDFT) or an inverse Fast Fourier transform (IFFT).

The output of the IDFT 1960 block is input to the Guard Interval (GI) inserter 1970, and the output of the GI inserter 1970 is input to the transceiver 1930 of FIG. 19.

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 (12)

1. In a method for performing retransmission in a WLAN system performed by an access point (AP),

   Transmitting a first wake-up packet for a plurality of wireless terminals including a plurality of main radio modules and a plurality of wake-up radio modules, wherein the first wake-up packet is transmitted. Instructing the plurality of main radio modules to enter an activated state, wherein the first wakeup packet is modulated according to an on-off keying (OOK) technique; And

   A second wakeup packet for the at least one wireless terminal when the at least one PS-poll frame is not received in response to the first wakeup packet from the at least one wireless terminal among the plurality of wireless terminals; Transmitting a downlink packet for at least one main radio module included in the at least one wireless terminal based on orthogonal frequency division multiplexing access (OFDMA), wherein the second wakeup packet is modulated according to the OOK scheme How to include.
2. According to claim 1,

   If the at least one wireless terminal does not receive the first wakeup packet, the second wakeup packet is received based on at least one WUR module included in the at least one wireless terminal.
3. The method of claim 2,

   Receiving the at least one PS-Poll frame in response to the second wakeup packet from the at least one wireless terminal.
4. According to claim 1,

   And when the at least one wireless terminal receives the first wakeup packet, the downlink packet is received based on at least one main radio module included in the at least one wireless terminal.
5. The method of claim 4, wherein

   Receiving at least one ACK frame in response to the downlink packet from the at least one wireless terminal.
6. According to claim 1,

   The downlink packet is a trigger frame that triggers at least one null data packet or at least one uplink transmission from the at least one wireless terminal.
7. In an access point (AP) performing retransmission in a WLAN system,

   A transceiver for transmitting or receiving a wireless signal; And

   A processor for controlling the transceiver, wherein the processor,

   Implemented to transmit a first wake-up packet for a plurality of wireless terminals comprising a plurality of main radio module and a plurality of Wake-Up Radio (WUR) module, the first wake The up packet instructs the plurality of main radio modules to enter an activated state, and the first wakeup packet is modulated according to an on-off keying (OOK) technique.

   A second wakeup packet for the at least one wireless terminal when the at least one PS-poll frame is not received in response to the first wakeup packet from the at least one wireless terminal among the plurality of wireless terminals; An AP configured to transmit a downlink packet for the main radio module based on an orthogonal frequency division multiplexing access (OFDMA), wherein the second wakeup packet is modulated according to the OOK scheme;
8. The method of claim 7, wherein

   When the at least one wireless terminal does not receive the first wakeup packet, the second wakeup packet is received based on at least one WUR module included in the at least one wireless terminal.
9. The method of claim 8,

   The processor,

   And the AP is further configured to receive the at least one PS-poll frame in response to the second wakeup packet from the at least one wireless terminal.
10. The method of claim 7, wherein

    And when the at least one wireless terminal receives the first wakeup packet, the downlink packet is received based on at least one main radio module included in the at least one wireless terminal.
11. The method of claim 10,

    The processor,

    And an AP configured to receive at least one ACK frame in response to the downlink packet from the at least one wireless terminal.
12. The method of claim 7, wherein

    The downlink packet is at least one null data packet or a trigger frame for triggering at least one uplink transmission from the at least one wireless terminal.

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