WO2018131883A1 - Method and apparatus for transmitting wakeup packet in wireless lan system - Google Patents

Abstract

A method and apparatus for transmitting a wakeup packet in a wireless LAN system is proposed. Specifically, a transmission apparatus configures a wakeup packet to which an OOK scheme is applied, and transmits the wakeup packet to a reception apparatus. The wakeup packet includes a wakeup preamble and a wakeup payload. The wakeup preamble includes a preamble sequence comprising an "on" signal and an "off" signal. The "on" signal is transmitted through an "on" symbol generated by applying a first sequence to 13 consecutive subcarriers over a 20-MHz band and performing 64-point IFFT. Information on the data rate of the wakeup payload is indicated using the preamble sequence.

Description

Method and apparatus for transmitting wake-up packet in WLAN system

The present disclosure relates to a technique for performing low power communication in a WLAN system, and more particularly, to a method and apparatus for transmitting a wake-up packet by applying a OOK scheme in a WLAN system.

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 the next-generation WLAN, there is a great interest in scenarios such as wireless office, smart home, stadium, hotspot, building / apartment, and AP based on the scenario. And STA are discussing about improving system performance in a dense environment with many 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.

The present specification proposes a method and apparatus for transmitting a wake-up packet by applying a OOK scheme in a WLAN system.

An example of the present specification proposes a method and apparatus for transmitting a wake-up packet to a WLAN system.

This embodiment may be operated in a transmitter, the receiver may correspond to a low power wake-up receiver, and the transmitter may correspond to an AP.

First of all, the term “on signal” may correspond to a signal having an actual power value. The off signal may correspond to a signal that does not have an actual power value.

The transmitter configures a wake-up packet to which an OOK (On-Off Keying) scheme is applied.

The transmitter transmits the wakeup packet to the receiver.

How the wakeup packet is configured is as follows.

The wakeup packet includes a wakeup preamble and a wakeup payload. In other words, a OOK scheme may be applied to the wakeup preamble and the wakeup payload.

The wakeup preamble includes a preamble sequence consisting of an on signal and an off signal. The preamble sequence may correspond to a signature sequence. The on signal may indicate 1, and the off signal may indicate 0.

The on signal is transmitted through an on symbol generated by applying a first sequence to 13 consecutive subcarriers in a 20 MHz band and performing a 64-point Inverse Fast Fourier Transform (IFFT). That is, the on signal may correspond to one bit and may be transmitted through one symbol generated by performing an IFFT.

Information about the data rate of the wakeup payload is indicated using the preamble sequence. That is, information on the data rate of the wakeup payload may be indicated through a sequence configured in the wakeup preamble.

Various embodiments of indicating a data rate of a wake-up payload through the preamble sequence are as follows.

For example, the preamble sequence may indicate that the data rate of the wakeup payload is a lower data rate than a reference value. In addition, the complementary sequence of the preamble sequence may indicate that the data rate of the wake-up payload is a higher data rate than a reference value.

When the data rate of the wakeup payload is lower than the reference value, a symbol repetition technique may be applied in which the wakeup payload is repeatedly transmitted n times the on signal or the off signal. N may be an integer of at least two. As the number of symbols is repeated, the data rate of the wake-up payload is lowered. The cross-correlation value of the preamble sequence may be obtained as a negative peak. That is, cross correlation may be performed using only the preamble sequence.

When the data rate of the wakeup payload is higher than the reference value, Manchester coding may be applied to the wakeup payload. The Manchester coding is configured to configure the on signal or the off signal based on a sequence in which coefficients exist only in subcarriers having an even subcarrier index or an even subcarrier in odd subcarrier indexes. May be a coding technique. The cross-correlation value of the preamble sequence may be obtained as a positive peak.

The reference value may be a data rate value of the wakeup payload when the wakeup payload is applied only to the OOK scheme. That is, if the data rate of the wake-up payload is greater than or equal to the reference value, it may be regarded as corresponding to a high data rate. If the data rate of the wake-up payload is lower than the reference value, it may be regarded as corresponding to a low data rate.

As another example, the information on the data rate of the wakeup payload may be indicated using a sequence in which one symbol is added before the preamble sequence. The on signal or the off signal may be transmitted in one symbol added before the preamble sequence.

As another example, information about the data rate of the wakeup payload may be indicated by using a sequence in which one symbol is added after the preamble sequence. The on signal or the off signal may be transmitted in one symbol added after the preamble sequence.

As another example, the information on the data rate of the wakeup payload may be indicated by using a combination of the preamble sequence and the complementary sequence of the preamble sequence. For example, when the sequence of the preamble is 101, the complementary sequence of the preamble sequence may be 010. The sequence of 101010, 101101, 010010, and 010101 combining the two sequences may indicate the data rate of the wakeup payload.

As another example, the sequence of repeating the preamble sequence twice may indicate that the data rate of the wakeup payload is lower than a reference value. The complementary sequence of the preamble sequence may indicate that the data rate of the wakeup payload is a data rate higher than a reference value.

The preamble sequence may be configured based on a basic service set (BSS) color. The BSS color may be signaled through a physical layer. That is, the BSS color may not be transmitted through the signal field.

The wakeup preamble may further include a synchronization sequence including the on signal or the off signal. In other words, in the wake-up preamble, a synchronization sequence may be used to perform time synchronization, and the preamble sequence may be used to indicate a data rate.

The on signal of the synchronization sequence may be transmitted repeatedly n times. The off signal of the sync sequence may be transmitted in the last symbol of the sync sequence. N may be an integer of at least two.

The on signal of the synchronization sequence may be configured based on a sequence in which the coefficients of the subcarriers are set to 1 or -1 and the coefficients of the remaining subcarriers are set to 0 in units of m subcarriers in the 13 subcarriers.

That is, if m = 2, an on-signal is constructed based on a sequence in which subcarrier coefficients exist in units of two spaces, and if m = 4, an on-signal is constructed in accordance with a sequence in which subcarrier coefficients exist in units of four columns. If m = 8, the on-signal may be configured based on a sequence in which subcarrier coefficients exist in units of eight columns. M is a natural number and may correspond to an even number as a value for decreasing a symbol.

This is to generate an information signal (or symbol) applying a symbol reduction technique. When a first sequence is applied to 13 subcarriers having coefficients of a subcarrier in units of m subcarriers and IFFT is performed, a 3.2us signal having a 3.2us / m period is generated. You can take one of these to construct a 3.2us / m on signal. The 3.2us / m on signal may be transmitted through the on symbol. Accordingly, the on symbol may have a length of 3.2 us / m except for CP. As a result, the length of the symbol may be reduced and the data rate may be increased instead of the conventional OOK method.

If m is 2, the length of the on symbol to which the on signal of the synchronization sequence is transmitted is 1.6us and n may be 5. If m is 4, the length of the on symbol on which the on signal of the synchronization sequence is transmitted is 0.8us and n may be 10. If m is 8, the length of an on symbol on which the on signal of the synchronization sequence is transmitted is 0.4us and n may be 20.

Increasing the number of repetitions of the on-signal may be advantageous in terms of time synchronization performance, but may increase overhead. Therefore, the n value may be determined in consideration of both time synchronization performance and overhead generation. In particular, the total length of the repeated on symbol may be set to be a multiple of 4 us.

According to the exemplary embodiment of the present specification, the wakeup packet is configured and transmitted by applying the OOK modulation scheme in the transmitter to reduce power consumption by using an envelope detector during wakeup decoding in the receiver. Therefore, the receiving device can decode the wakeup packet to the minimum power.

In addition, the transmitter may configure the preamble sequence of the wakeup packet to signal the start of the wakeup packet, and efficiently perform time synchronization using the periodicity of the preamble sequence.

1 is a conceptual diagram illustrating a structure of a wireless local area network (WLAN).

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 illustrates a low power wake-up receiver in an environment in which data is not received.

5 illustrates a low power wake-up receiver in an environment in which data is received.

6 shows an example of a wakeup packet structure according to the present embodiment.

7 shows a signal waveform of a wakeup packet according to the present embodiment.

FIG. 8 is a diagram for describing a principle in which power consumption is determined according to a ratio of 1 and 0 of bit values constituting binary sequence information using the OOK method.

9 shows a method of designing a OOK pulse according to the present embodiment.

10 is an explanatory diagram of a Manchester coding scheme according to the present embodiment.

11 illustrates various examples of a symbol repetition technique of repeating n symbols according to the present embodiment.

12 illustrates various examples of a symbol reduction technique according to the present embodiment.

Fig. 13 shows an example of the structure of the wakeup frame according to the present embodiment.

14 shows an example of configuring a wakeup preamble using a periodic signal according to the present embodiment.

15 shows another example of configuring a wake-up preamble using a periodic signal according to the present embodiment.

16 shows another example of configuring a wake-up preamble using a periodic signal according to the present embodiment.

17 is a flowchart illustrating a procedure of indicating a data rate through a wakeup preamble by applying the OOK scheme according to the present embodiment.

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

1 is a conceptual diagram illustrating a structure of a wireless local area network (WLAN).

1 shows the structure of the infrastructure basic service set (BSS) of the Institute of Electrical and Electronic Engineers (IEEE) 802.11.

Referring to the top of FIG. 1, the WLAN system may include one or more infrastructure BSSs 100 and 105 (hereinafter, BSS). The BSSs 100 and 105 are a set of APs and STAs such as an access point 125 and a STA1 (station 100-1) capable of successfully synchronizing and communicating with each other, and do not indicate a specific area. The BSS 105 may include one or more joinable STAs 105-1 and 105-2 to one AP 130.

The BSS may include at least one STA, APs 125 and 130 for providing a distribution service, and a distribution system (DS) 110 for connecting a plurality of APs.

The distributed system 110 may connect several BSSs 100 and 105 to implement an extended service set (ESS) 140 which is an extended service set. The ESS 140 may be used as a term indicating one network in which one or several APs 125 and 230 are connected through the distributed system 110. APs included in one ESS 140 may have the same service set identification (SSID).

The portal 120 may serve as a bridge for connecting the WLAN network (IEEE 802.11) with another network (for example, 802.X).

In the BSS as shown in the upper part of FIG. 1, a network between the APs 125 and 130 and a network between the APs 125 and 130 and the STAs 100-1, 105-1 and 105-2 may be implemented. However, it may be possible to perform communication by setting up a network even between STAs without the APs 125 and 130. A network that performs communication by establishing a network even between STAs without APs 125 and 130 is defined as an ad-hoc network or an independent basic service set (BSS).

1 is a conceptual diagram illustrating an IBSS.

Referring to the bottom of FIG. 1, the IBSS is a BSS operating in an ad-hoc mode. Since IBSS does not contain an AP, there is no centralized management entity. That is, in the IBSS, the STAs 150-1, 150-2, 150-3, 155-4, and 155-5 are managed in a distributed manner. In the IBSS, all STAs 150-1, 150-2, 150-3, 155-4, and 155-5 may be mobile STAs, and access to a distributed system is not allowed, thus making a self-contained network. network).

A STA is any functional medium that includes 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. May be used to mean both an AP and a non-AP STA (Non-AP Station).

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

On the other hand, the term "user" may be used in various meanings, for example, may also be used to mean an STA participating in uplink MU MIMO and / or uplink OFDMA transmission in wireless LAN communication. It is not limited to this.

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.).

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 on a bandwidth wider than the channel bandwidth of 20 MHz (eg, 40 MHz and 80 MHz) may be a structure in which linear scaling of the PPDU structure used in the channel bandwidth of 20 MHz is applied.

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.

Wireless networks are ubiquitous, usually indoors and often installed outdoors. Wireless networks use various techniques to send and receive information. For example, but not limited to, two widely used technologies for communication are those that comply with IEEE 802.11 standards such as the IEEE 802.11n standard and the IEEE 802.11ac standard.

The IEEE 802.11 standard specifies a common Medium Access Control (MAC) layer that provides a variety of features to support the operation of IEEE 802.11-based wireless LANs (WLANs). The MAC layer utilizes protocols that coordinate access to shared radios and improve communications over wireless media, such as IEEE 802.11 stations (such as a PC's wireless network card (NIC) or other wireless device or station (STA) and access point ( Manage and maintain communication between APs).

IEEE 802.11ax is the successor to 802.11ac and has been proposed to improve the efficiency of WLAN networks, especially in high density areas such as public hotspots and other high density traffic areas. IEEE 802.11 can also use Orthogonal Frequency Division Multiple Access (OFDMA). The High Efficiency WLAN Research Group (HEW SG) within the IEEE 802.11 Work Group is dedicated to improving system throughput / area in high-density scenarios of APs (access points) and / or STAs (stations) in relation to the IEEE 802.11 standard. We are considering improving efficiency.

Wearable devices and small computing devices such as sensors and mobile devices are constrained by small battery capacities, but use wireless communication technologies such as Wi-Fi, Bluetooth®, and Bluetooth® Low Energy (BLE). Support, connect to and exchange data with other computing devices such as smartphones, tablets, and computers. Since these communications consume power, it is important to minimize the energy consumption of such communications in these devices. One ideal strategy to minimize energy consumption is to power off the communication block as frequently as possible while maintaining data transmission and reception without increasing delay too much. That is, the communication block is transmitted immediately before the data reception, and only when there is data to wake up, the communication block is turned on and the communication block is turned off for the remaining time.

Hereinafter, a low-power wake-up receiver (LP-WUR) will be described.

The communication system (or communication subsystem) described herein includes a main radio (802.11) and a low power wake up receiver.

The main radio is used for transmitting and receiving user data. The main radio is turned off if there are no data or packets to transmit. The low power wake-up receiver wakes up the main radio when there is a packet to receive. At this time, the user data is transmitted and received by the main radio.

The low power wake-up receiver is not for user data. It is simply a receiver to wake up the main radio. In other words, the transmitter is not included. The low power wake-up receiver is active while the main radio is off. Low power wake-up receivers target a target power consumption of less than 1 mW in an active state. In addition, low power wake-up receivers use a narrow bandwidth of less than 5 MHz. In addition, the target transmission range of the low power wake-up receiver is the same as that of the existing 802.11.

4 illustrates a low power wake-up receiver in an environment in which data is not received. 5 illustrates a low power wake-up receiver in an environment in which data is received.

As shown in Figures 4 and 5, if there is data to be transmitted and received, one way to implement an ideal transmission and reception strategy is a main radio such as Wi-Fi, Bluetooth® radio, or Bluetooth® Radio (BLE). Adding a low power wake-up receiver (LP-WUR) that can wake up.

Referring to FIG. 4, the Wi-Fi / BT / BLE 420 is turned off and the low power wake-up receiver 430 is turned on without receiving data. Some studies show that the low power wake-up receiver (LP-WUR) can consume less than 1mW.

However, as shown in FIG. 5, when a wakeup packet is received, the low power wakeup receiver 530 may receive the entire Wi-Fi / BT / BLE radio 520 so that the data packet following the wakeup packet can be correctly received. Wake up). In some cases, however, actual data or IEEE 802.11 MAC frames may be included in the wakeup packet. In this case, it is not necessary to wake up the entire Wi-Fi / BT / BLE radio 520, but only a part of the Wi-Fi / BT / BLE radio 520 to perform the necessary process. This can result in significant power savings.

One example technique disclosed herein defines a method for a granular wakeup mode for Wi-Fi / BT / BLE using a low power wakeup receiver. For example, the actual data contained in the wakeup packet can be passed directly to the device's memory block without waking up the Wi-Fi / BT / BLE radio.

As another example, if a wakeup packet contains an IEEE 802.11 MAC frame, only the MAC processor of the Wi-Fi / BT / BLE wireless device needs to wake up to process the IEEE 802.11 MAC frame included in the wakeup. That is, the PHY module of the Wi-Fi / BT / BLE radio can be turned off or kept in a low power mode.

A number of granular wakeup modes have been defined for Wi-Fi / BT / BLE radios that use low power wake-up receivers, requiring that the Wi-Fi / BT / BLE radio be powered on when a wake-up packet is received. However, according to the above embodiment, only necessary parts (or components) of the Wi-Fi / BT / BLE radio can be selectively woken up, thereby saving energy and reducing the waiting time. Many solutions that use low-power wake-up receivers to receive wake-up packets wake up the entire Wi-Fi / BT / BLE radio. One exemplary aspect discussed herein wakes up only the necessary portions of the Wi-Fi / BT / BLE radio required to process the received data, saving significant amounts of energy and reducing unnecessary latency in waking up the main radio. Can be.

In addition, in the above embodiment, the low power wake-up receiver 530 may wake up the main radio 520 based on the wake-up packet transmitted from the transmitter 500.

In addition, the transmitter 500 may be set to transmit a wakeup packet to the receiver 510. For example, the low power wake-up receiver 530 may be instructed to wake up the main radio 520.

6 shows an example of a wakeup packet structure according to the present embodiment.

The wakeup packet may include one or more legacy preambles. One or more legacy devices may decode or process the legacy preamble.

In addition, the wakeup packet may include a payload after the legacy preamble. The payload may be modulated by a simple modulation scheme, for example, an On-Off Keying (OOK) modulation scheme.

Referring to FIG. 6, the transmitter may be configured to generate and / or transmit a wakeup packet 600. The receiving device may be configured to process the received wakeup packet 600.

In addition, the wakeup packet 600 may include a legacy preamble or any other preamble 610 as defined by the IEEE 802.11 specification. In addition, the wakeup packet 600 may include a payload 620.

Legacy preambles provide coexistence with legacy STAs. The legacy preamble 610 for coexistence uses the L-SIG field to protect the packet. The 802.11 STA may detect the start of a packet through the L-STF field in the legacy preamble 610. The 802.11 STA can know the end of the packet through the L-SIG field in the legacy preamble 610. In addition, by adding a BPSK modulated symbol after the L-SIG, a false alarm of an 802.11n terminal can be reduced. One symbol (4us) modulated with BPSK also has a 20MHz bandwidth like the legacy part. The legacy preamble 610 is a field for third party legacy STAs (STAs not including LP-WUR). The legacy preamble 610 is not decoded from the LP-WUR.

The payload 620 may include a wakeup preamble 622. Wake-up preamble 622 may include a sequence of bits configured to identify wake-up packet 600. The wakeup preamble 622 may include, for example, a PN sequence.

In addition, the payload 620 may include a MAC header 624 including address information of a receiver receiving the wakeup packet 600 or an identifier of the receiver.

In addition, the payload 620 may include a frame body 626 that may include other information of the wakeup packet. For example, the frame body 626 may include length or size information of the payload.

In addition, the payload 620 may include a Frame Check Sequence (FCS) field 628 that includes a Cyclic Redundancy Check (CRC) value. For example, it may include a CRC-8 value or a CRC-16 value of the MAC header 624 and the frame body 626.

7 shows a signal waveform of a wakeup packet according to the present embodiment.

Referring to FIG. 7, the wakeup packet 700 includes a legacy preamble (802.11 preamble, 710) and a payload modulated by OOK. That is, the legacy preamble and the new LP-WUR signal waveform coexist.

In addition, the legacy preamble 710 may be modulated according to the OFDM modulation scheme. That is, the legacy preamble 710 is not applied to the OOK method. In contrast, the payload may be modulated according to the OOK method. However, the wakeup preamble 722 in the payload may be modulated according to another modulation scheme.

If the legacy preamble 710 is transmitted on a channel bandwidth of 20 MHz to which 64 FFTs are applied, the payload may be transmitted on a channel bandwidth of about 4.06 MHz. This will be described later in the OOK pulse design method.

First, a modulation scheme using the OOK scheme and a Manchester coding scheme will be described.

FIG. 8 is a diagram for describing a principle in which power consumption is determined according to a ratio of 1 and 0 of bit values constituting binary sequence information using the OOK method.

Referring to FIG. 8, information in the form of a binary sequence having 1 or 0 as a bit value is represented. By using a bit value of 1 or 0 of the binary sequence information, OOK modulation can be performed. That is, in consideration of the bit values of the binary sequence information, it is possible to perform the communication of the OOK modulation method. For example, when the light emitting diode is used for visible light communication, the light emitting diode is turned on when the bit value constituting the binary sequence information is 1, and the light emitting diode is turned off when the bit value is 0. The light emitting diode can be made to blink. 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 is used. Referring to FIG. 8, there is information in the form of a binary sequence having a value of '1001101011'. As described above, when the bit value is 1, the transmitter is turned on, and when the bit value is 0, the transmitter is turned off, the symbol is turned on at 6 bit values out of 10 bit values. ) do. Therefore, when the symbol is turned on in all 10 bit values, if the power consumption is 100%, the power consumption is 60% according to the duty cycle of FIG. 8.

That is, it can be said that the power consumption of the transmitter is determined according to the ratio of 1 and 0 constituting the binary sequence information. In other words, if there is a constraint that the power consumption of the transmitter must be kept at a certain value, the ratio of 1 and 0, which constitutes information in binary sequence form, must also be maintained. For example, in the case of lighting equipment, since the lighting must be maintained at a specific luminance value desired by people, the ratio of 1 and 0 constituting the information in the form of a binary sequence must also be maintained.

However, since the receiver is mainly a wake-up receiver (WUR), the transmission power is not important. The main reason for using OOK is that the power consumption is very low when decoding the received signal. Until the decoding is performed, there is no significant difference in power consumption in the main radio or WUR, but a large difference occurs in the decoding process. 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 shows a method of designing a OOK pulse according to the present embodiment.

The OFDM transmitter of 802.11 can be reused to generate OOK pulses. The transmitter can generate a sequence having 64 bits by applying a 64-point IFFT as in 802.11.

The transmitter should generate the payload of the wakeup packet by modulating the OOK method. However, since the wakeup packet is for low power communication, the OOK method is applied to the ON-signal. The on signal is a signal having an actual power value, and the off signal (OFF-signal) corresponds to a signal having no actual power value. The off signal is also applied to the OOK method, but the signal is not generated using the transmitter, and since no signal is actually transmitted, it is not considered in the configuration of the wakeup packet.

In the OOK method, information (bit) 1 may be an on signal and information (bit) 0 may be an off signal. Alternatively, when the Manchester coding scheme is applied, information 1 may indicate a transition from an off signal to an on signal, and information 0 may indicate a transition from an on signal to an off signal. Alternatively, on the contrary, the information 1 may indicate the transition from the on signal to the off signal, and the information 0 may indicate the transition from the off signal to the on signal. Manchester coding scheme will be described later.

Referring to FIG. 9, as shown in the right frequency domain graph 920, the transmitter applies a sequence by selecting 13 consecutive subcarriers of a 20 MHz band as a reference band as a sample. In FIG. 9, 13 subcarriers located among the subcarriers in the 20 MHz band are selected as samples. That is, a subcarrier whose subcarrier index is from -6 to +6 is selected from the 64 subcarriers. In this case, the subcarrier index 0 may be nulled to 0 as the DC subcarrier. Set a specific sequence only to the 13 subcarriers selected as samples, and set all subcarriers except the subcarriers (subcarrier indexes -32 to -7 and subcarrier indexes +7 to +31) to 0. .

In addition, since subcarrier spacing is 312.5 KHz, 13 subcarriers have a channel bandwidth of about 4.06 MHz. That is, it can be said that power is provided only for 4.06MHz in the 20MHz band in the frequency domain. By moving the power to the center, the signal to noise ratio (SNR) can be increased and the power consumption of the AC / DC converter of the receiver can be reduced. In addition, the power consumption can be reduced by reducing the sampling frequency band to 4.06MHz.

In addition, as shown in the left time domain graph 910 of FIG. 9, the transmitter may generate one on-signal in the time domain by performing a 64-point IFFT on 13 subcarriers. One on-signal has a size of 1 bit. That is, a sequence composed of 13 subcarriers may correspond to 1 bit. On the other hand, the transmitter may not transmit the off signal at all. When performing IFFT, a 3.2us symbol may be generated, and if a CP (Cyclic Prefix, 0.8us) is included, one symbol having a length of 4us may be generated. That is, one bit indicating one on-signal may be loaded in one symbol.

The reason for configuring and sending the bits as in the above-described embodiment is to reduce power consumption by using an envelope detector in the receiver. As a result, the receiving device can decode the packet with the minimum power.

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

Generalizing the above, the signal transmitted in the frequency domain is as follows. That is, each signal having a length of K in the 20 MHz band may be transmitted on K consecutive subcarriers of a total of 64 subcarriers. That is, K may correspond to the bandwidth of the OOK pulse by the number of subcarriers used to transmit a signal. All other coefficients of the K subcarriers are zero. In this case, the indexes of the K subcarriers used by the signal corresponding to the information 0 and the information 1 are the same. For example, the subcarrier index used may be represented 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).

10 is an explanatory diagram of a Manchester coding scheme according to the present embodiment.

Manchester coding is a type of line coding, and may indicate information as shown in the following table in a manner in which a transition of a magnitude value occurs in the middle of one bit period.

That is, Manchester coding means a method of converting data from 1 to 01, 0 to 10, 1 to 10, and 0 to 01. Table 1 shows an example in which data is converted from 1 to 10 and 0 to 01 using Manchester coding.

As shown in Fig. 10, the bit string to be transmitted, the Manchester coded signal, the clock reproduced on the receiving side, and the data reproduced on the clock are shown in order from top to bottom.

When the transmitting side transmits data using the Manchester coding scheme, the receiving side reads the data a little later on the basis of the transition point transitioning from 1 → 0 or 0 → 1 and recovers the data, and then transitions to 1 → 0 or 0 → 1 The clock is recovered by recognizing the transition point as the clock transition point. Alternatively, when the symbol is divided based on the transition point, it can be simply decoded by comparing the power at the front and the back at the center of the symbol.

As shown in FIG. 10, the bit string to be transmitted is 10011101, the Manchester coded signal is 0110100101011001, and the clock reproduced by the receiver recognizes the transition point of the Manchester coded signal as the transition point of the clock. Then, the data is recovered by using the reproduced clock.

By using the Manchester coding scheme, it is possible to communicate in a synchronous manner using only a data transmission channel without using a separate clock.

In addition, this method can use the TXD pin for data transmission and the RXD pin for reception by using only the data transmission channel. Therefore, synchronized bidirectional transmission is possible.

This specification proposes various symbol types that can be used in the WUR and thus data rates.

Since STAs requiring robust performance and STAs receiving strong signals from APs are mixed, it is necessary to support efficient data rates in some situations. In order to obtain reliable and robust performance, a symbol coding based symbol coding technique and a symbol repetition technique may be used. In addition, a symbol reduction technique may be used to obtain a high data rate.

In this case, each symbol may be generated by using an existing 802.11 OFDM transmitter. In addition, the number of subcarriers used to generate each symbol may be thirteen. However, it is not limited thereto.

In addition, each symbol may use OOK modulation formed of an ON-signal and an OFF-signal.

One symbol generated for the WUR may be composed of a CP (Cyclic Prefix or Guard Interval) and a signal part representing actual information. Symbols having various data rates may be designed by variously setting or repeating the lengths of the CP and the actual information signal.

The following are various examples of symbol types.

For example, the basic WUR symbol may be represented as CP + 3.2us. That is, one bit is represented using a symbol having the same length as the existing Wi-Fi. Specifically, the transmitting apparatus applies a specific sequence to all available subcarriers (for example, 13 subcarriers) and then performs IFFT to form an information signal portion of 3.2 us. In this case, a coefficient of 0 may be loaded on the DC subcarrier or the middle subcarrier index among all available subcarriers.

Different sequences may be applied to the available subcarriers according to the 3.2us on signal and the 3.2us off signal. A 3.2us off signal can be generated by applying all coefficients to zero.

CP may be used by adopting a specific length from the rear of the information signal 3.2us immediately behind. At this time, CP may be 0.4us or 0.8us. This length is equal to the guard interval of 802.11ac.

Accordingly, one bit information corresponding to one basic WUR symbol may be represented as shown in the following table.

Information ‘0’	Information ‘1’
3.2us OFF-signal	3.2us ON-signal

Table 2 does not indicate CP separately. In fact, CP + 3.2us including CP may point to one 1-bit information. That is, the 3.2us on signal can be viewed as a (CP + 3.2us) on signal. A 3.2us off signal can be seen as a (CP + 3.2us) off signal.

As another example, a symbol to which Manchester coding is applied may be represented as CP + 1.6us + CP + 1.6us or CP + 1.6us + 1.6us. The symbol to which the Manchester coding is applied may be generated as follows.

In the OOK transmission using the Wi-Fi transmitter, the time used for transmitting one bit (or symbol) except for the guard interval of the transmission signal is 3.2 us. In this case, if Manchester coding is applied, a signal size transition should occur at 1.6us. That is, each sub-information having a length of 1.6us should have a value of 0 or 1, and may configure a signal in the following manner.

* Information 0-> 1 0 (each can be referred to as sub information 1 0 or sub symbol 1 (ON) 0 (OFF))

First 1.6us (sub information 1 or sub symbol 1): Sub information 1 may have a value of beta * ones (1, K). Beta is a power normalization factor and may be, for example, 1 / sqrt (ceil (K / 2)).

In addition, a specific sequence is applied in units of two squares to all available subcarriers (eg, 13 subcarriers) to generate a symbol to which Manchester coding is applied. That is, even-numbered subcarriers of a particular sequence are nulled to zero. That is, in a particular sequence, coefficients may exist at intervals of two cells. For example, suppose that 13 subcarriers are used to construct an on-signal, a particular sequence with coefficients spaced two spaces apart is {a 0 b 0 c 0 d 0 e 0 f 0 g}, {0 a 0 b 0 c 0 d 0 e 0 f 0} or {a 0 b 0 c 0 0 0 d 0 e 0 method. At this time, a, b, c, d, e, f, g is 1 or -1.

That is, the transmitter maps a specific sequence to K consecutive subcarriers of 64 subcarriers (for example, 33-floor (K / 2): 33 + ceil (K / 2) -1) and the remaining subcarriers. IFFT is performed by setting the coefficient to 0. In this way, signals in the time domain can be generated. The signal in the time domain is a 3.2us long signal having a 1.6us period because coefficients exist at intervals of two spaces in the frequency domain. One of the first or second 1.6us period signals can be selected and used as sub information 1.

Second 1.6us (sub information 0 or sub symbol 0): The sub information 0 may have a value of zeros (1, K). Similarly, the transmitter maps a specific sequence to K consecutive subcarriers of 64 subcarriers (eg, 33-floor (K / 2): 33 + ceil (K / 2) -1) and performs IFFT. The signal in the time domain can be generated. The sub information 0 may correspond to a 1.6us off signal. The 1.6us off signal can be generated by setting all coefficients to zero.

One of the first or second 1.6us periodic signals of the signal in the time domain may be selected and used as the sub information 0. You can simply use the zeros (1,32) signal as subinformation zero.

* Information 1-> 0 1 (each can be referred to as sub information '0', '1' or sub symbol 0 (OFF) 1 (ON))

Since information 1 is also divided into the first 1.6us (sub information 0) and the second 1.6us (sub information 1), a signal corresponding to each sub information may be configured in the same manner as the information 0 is generated.

By using a technique of generating information 0 and information 1 using Manchester coding, it is possible to prevent the off symbol from continuing as compared to the conventional method. Therefore, a coexistence problem with an existing Wi-Fi device may not occur. The coexistence problem is a problem caused by transmitting a signal by determining that another device is a channel idle state due to a continuous off symbol. If only OOK modulation is used, for example, the off-symbol may be contiguous with the sequence 100001 or the like, but if Manchester coding is used, the off-symbol cannot be contiguous with the sequence 100101010110.

According to the above description, the sub information may be referred to as a 1.6us information signal. The 1.6us information signal may be a 1.6us on signal or a 1.6 off signal. The 1.6us on signal and the 1.6 off signal may have different sequences applied to each subcarrier.

CP can be used by adopting a specific length from the back of the 1.6us of the information signal immediately after. At this time, CP may be 0.4us or 0.8us. This length is equal to the guard interval of 802.11ac.

Accordingly, one bit information corresponding to one Manchester coded symbol may be represented as shown in the following table.

Information ‘0’	Information ‘1’
1.6us ON-signal + 1.6us OFF-signal	1.6us OFF-signal + 1.6us ON-signal
Or 1.6us OFF-signal + 1.6us ON-signal	Or 1.6us ON-signal + 1.6us OFF-signal

Table 3 does not indicate CP separately. In fact, CP + 1.6us + CP + 1.6us or CP + 1.6us + 1.6us including CP may indicate one 1-bit information. That is, in the former case, the 1.6us on signal and the 1.6us off signal may be regarded as the (CP + 1.6us) on signal and the (CP + 1.6us) off signal.

As another example, a method of constructing a wake-up packet by repeating symbols for performance improvement is proposed.

The symbol repetition technique is applied to the wakeup payload 724. The symbol repetition technique means repetition of a time signal after insertion of an IFFT and a cyclic prefix (CP) of each symbol. Thus, the length (time) of the wakeup payload 724 is doubled.

That is, it is proposed to apply a symbol representing information such as information 0 or information 1 to a specific sequence and to repeat the configuration as follows.

Option 1: Information 0 and Information 1 can be repeatedly represented by the same symbol.

Info 0-> 0 0 (repeat Info 0 twice)

-Info 1-> 1 1 (repeat Info 1 twice)

Option 2: Information 0 and Information 1 can be repeatedly represented by different symbols.

Information 0-> 0 1 or 1 0 (repeat info 0 and info 1)

Info 1-> 1 0 or 0 1 (repeat Info 1 and Info 0)

Hereinafter, a method of decoding by a receiving apparatus a signal transmitted by applying a symbol repetition technique to the transmitting apparatus will be described.

The transmitted signal may correspond to a wakeup packet, and a method of decoding the wakeup packet can be largely divided into two types. The first is non-coherent detection and the second is coherent detection. In non-coherent detection, the phase relationship between the transmitter and receiver signals is not fixed. Thus, the receiver does not need to measure and adjust the phase of the received signal. In contrast, the coherent detection method requires that the phase of the signal between the transmitter and the receiver be aligned.

The receiver includes the low power wake-up receiver described above. The low power wake-up receiver may decode a packet (wake-up packet) transmitted using an OOK modulation scheme using an envelope detector to reduce power consumption.

The envelope detector measures and decodes the power or magnitude of the received signal. The receiver sets a threshold based on the power or magnitude measured by the envelope detector. When decoding the symbol to which the OOK is applied, it is determined as information 1 if it is greater than or equal to the threshold value, and as information 0 when it is smaller than the threshold value.

The method of decoding a symbol to which the symbol repetition technique is applied is as follows. In the option 1, the receiving apparatus may use the wake-up preamble 722 to calculate a power when symbol 1 (symbol including information 1) is transmitted and determine the threshold.

In detail, the average power of the two symbols may be determined to determine information 1 (1 1) if the value is equal to or greater than the threshold value, and to determine information 0 (0 0) if the value is less than the threshold value.

In addition, in option 2, information may be determined by comparing the power of two symbols without determining a threshold.

Specifically, if information 1 is composed of 0 1 and information 0 is composed of 1 0, it is determined as information 0 if the power of the first symbol is greater than the power of the second symbol. On the contrary, if the power of the first symbol is less than the power of the second symbol, it is determined as information 1.

This is because the order of symbols can be reconstructed by an interleaver. The interleaver may be applied in units of specific symbol numbers below the packet unit.

In addition, not only two symbols but also n can be extended as follows. 11 illustrates various examples of a symbol repetition technique of repeating n symbols according to the present embodiment.

Option 1: Information 0 and information 1 may be repeatedly represented by the same symbol n times as shown in FIG.

-Information 0-> 0 0 ... 0 (repeat info 0 n times)

-Information 1-> 1 1 ... 1 (repeat information 1 n times)

* Option 2: As shown in FIG. 11, information 0 and information 1 may be repeatedly represented by different symbols n times.

-Information 0-> 0 1 0 1 ... or 1 0 1 0 ... (repeat info 0 and info 1 n times with each other)

-Info 1-> 1 0 1 0 ... or 0 1 0 1 ... (repeat info 1 and info 0 n times with each other)

Option 3: As shown in FIG. 11, one half of a symbol may be configured as information 0 and the other half may be configured as information 1 to represent n symbols.

-Information 0-> 0 0 ... 1 1 ... or 1 1 ... 0 0 ... (n / 2 symbols consist of information 0, the remaining n / 2 symbols consist of information 1 do)

-Information 1-> 1 1 ... 0 0 ... or 0 0 ... 1 1 ... (n / 2 symbols consist of information 0, the remaining n / 2 symbols consist of information 1 do)

Option 4: When n is odd, as shown in FIG. 11, n symbols may be represented by dividing the number of symbols 1 (symbol including information 1) and the number of symbols 0 (symbol including information 0).

Information 0-> n symbols where the number of symbols 1 is odd and the number of symbols 0 is even, or n symbols where the number of symbols 1 is even and the number of symbols 0 is odd

Information 1-> n symbols where the number of symbols 0 is odd and the number of symbols 1 is even, or n symbols where the number of symbols 0 is even and the number of symbols 1 is odd

In addition, the order of symbols may be reconstructed by the interleaver. The interleaver may be applied in units of packets and specific symbols.

In addition, as described above, the receiving apparatus may determine whether the information is 0 or 1 by determining the threshold value and comparing the powers of the n symbols.

However, the use of consecutive symbol 0 (or off symbol) may cause a coexistence problem with an existing Wi-Fi device and / or another device. The coexistence problem is a problem caused by transmitting a signal by determining that another device is a channel idle state due to a continuous off symbol. Thus, the option 2 scheme may be preferred as it is desirable to avoid the use of consecutive off symbols to solve the leveling problem.

In addition, it can be extended in a manner of expressing m information using n symbols. In this case, the first or last m is represented by 0 (OFF) or 1 (ON) symbols depending on the information, and the nm or 0 (OFF) or 1 (ON) redundant symbols are formed consecutively before or after. can do.

For example, if a code rate of 3/4 is applied to the information 010, it may be 1,010 or 010,1 or 0,010 or 010,0. However, in order to prevent the use of consecutive off symbols, it may be desirable to apply a code rate of 1/2 or less.

In this embodiment as well, the order of symbols can be reconstructed by the interleaver. The interleaver may be applied in units of packets and specific symbols.

Hereinafter, various embodiments of a symbol to which the symbol repetition technique is applied will be described.

In general, a symbol to which the symbol repetition technique is applied may be represented by n (CP + 3.2us) or CP + n (1.6us).

As shown in FIG. 11, n (n> = 2) information signals (symbols) are used to represent 1 bit, and a specific sequence is applied to all available subcarriers (for example, 13). Form a signal (symbol).

Different sequences may be applied to the available subcarriers according to the 3.2us on signal and the 3.2us off signal. A 3.2us off signal can be generated by applying all coefficients to zero.

CP may be used by adopting a specific length from the rear of the information signal 3.2us immediately behind. At this time, CP may be 0.4us or 0.8us. This length is equal to the guard interval of 802.11ac.

Accordingly, 1 bit information corresponding to a symbol to which a general symbol repetition technique is applied may be represented as shown in the following table.

Information ‘0’	Information ‘1’
3.2us OFF-signal	3.2us ON-signal
Or two specific consecutive signals are 3.2us ON-signal + 3.2us OFF-signal, all other signals are ON or all OFF	Or two specific consecutive signals are 3.2us OFF-signal + 3.2us ON-signal, all other signals are ON or all OFF
Or two specific consecutive signals are 3.2us OFF-signal + 3.2us ON-signal, all other signals are ON or all OFF	Or two specific consecutive signals are 3.2us ON-signal + 3.2us OFF-signal, all other signals are ON or all OFF
Or a certain number (or ceil (n / 2) or floor (n / 2)) placed in a specific position is 3.2us OFF-signal, 3.2us ON-signalEx) ON + OFF + ON + OFF…	Or a certain number (or ceil (n / 2) or floor (n / 2)) placed in a specific position is 3.2us ON-signal, 3.2us OFF-signalEx) OFF + ON + OFF + ON + OFF…

Table 4 does not indicate CP separately. In fact, n pieces (CP + 3.2us) including CPs or CP + n pieces (3.2us) may indicate one 1-bit information. That is, in the case of n (CP + 3.2us), the 3.2us on signal may be viewed as a (CP + 3.2us) on signal, and the 3.2us off signal may be viewed as a (CP + 3.2us) off signal.

As another example, a symbol to which the symbol repetition technique is applied may be represented as CP + 3.2us + CP + 3.2us or CP + 3.2us + 3.2us.

According to the above embodiment, two information signals (symbols) are used to represent one bit and a specific sequence is applied to all available subcarriers (for example, thirteen). Form.

Different sequences may be applied to the available subcarriers according to the 3.2us on signal and the 3.2us off signal. A 3.2us off signal can be generated by applying all coefficients to zero.

CP may be used by adopting a specific length from the rear of the information signal 3.2us immediately behind. At this time, CP may be 0.4us or 0.8us. This length is equal to the guard interval of 802.11ac.

Accordingly, one bit information corresponding to a symbol to which the symbol repetition technique is applied may be represented as shown in the following table.

Information ‘0’	Information ‘1’
3.2us OFF-signal	3.2us ON-signal + 3.2us ON-signal
Or 3.2us ON-signal + 3.2us OFF-signal	Or 3.2us OFF-signal + 3.2us ON-signal
Or 3.2us OFF-signal + 3.2us ON-signal	Or 3.2us ON-signal + 3.2us OFF-signal

Table 5 does not indicate CP separately. In fact, CP + 3.2us + CP + 3.2us or CP + 3.2us + 3.2us, including CP, may point to one 1-bit information. That is, in the case of CP + 3.2us + CP + 3.2us, the 3.2us on signal can be viewed as a (CP + 3.2us) on signal, and the 3.2us off signal can be viewed as a (CP + 3.2us) off signal. .

As another example, a symbol to which the symbol repetition technique is applied may be represented as CP + 3.2us + CP + 3.2us + CP + 3.2us or CP + 3.2us + 3.2us + 3.2us.

According to the above embodiment, three information signals (symbols) are used to represent one bit and a specific sequence is applied to all available subcarriers (eg, thirteen). Form.

Different sequences may be applied to the available subcarriers according to the 3.2us on signal and the 3.2us off signal. A 3.2us off signal can be generated by applying all coefficients to zero.

CP may be used by adopting a specific length from the rear of the information signal 3.2us immediately behind. At this time, CP may be 0.4us or 0.8us. This length is equal to the guard interval of 802.11ac.

Accordingly, one bit information corresponding to a symbol to which the symbol repetition technique is applied may be represented as shown in the following table.

Information ‘0’	Information ‘1’
3.2us OFF-signal + 3.2us OFF-signal + 3.2us OFF-signal	3.2us ON-signal + 3.2us ON-signal + 3.2us ON-signal
Or 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal	Or 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal
Or 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal	Or 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal
Or 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal	Or 3.2us OFF-signal + 3.2us ON-signal + 3.2us OFF-signal

Table 6 does not indicate CP separately. In fact, CP + 3.2us + CP + 3.2us + CP + 3.2us or CP + 3.2us + 3.2us + 3.2us, including CP, may point to one 1-bit information. That is, in the case of CP + 3.2us + CP + 3.2us + CP + 3.2us, the 3.2us on signal can be seen as a (CP + 3.2us) on signal, and the 3.2us off signal is a (CP + 3.2us) off It can be seen as a signal.

As another example, a symbol to which the symbol repetition technique is applied may be represented as CP + 3.2us + CP + 3.2us + CP + 3.2us + CP + 3.2us or CP + 3.2us + 3.2us + 3.2us + 3.2us.

According to the above embodiment, four information signals (symbols) are used to represent one bit and a specific sequence is applied to all available subcarriers (for example, thirteen), and then IFFT is taken to generate an information signal (symbol) of 3.2us. Form.

Different sequences may be applied to the available subcarriers according to the 3.2us on signal and the 3.2us off signal. A 3.2us off signal can be generated by applying all coefficients to zero.

CP may be used by adopting a specific length from the rear of the information signal 3.2us immediately behind. At this time, CP may be 0.4us or 0.8us. This length is equal to the guard interval of 802.11ac.

Accordingly, one bit information corresponding to a symbol to which the symbol repetition technique is applied may be represented as shown in the following table.

Information ‘0’	Information ‘1’
3.2us OFF-signal + 3.2us OFF-signal + 3.2us OFF-signal + 3.2us OFF-signal	3.2us ON-signal + 3.2us ON-signal + 3.2us ON-signal + 3.2us ON-signal
Or 3.2us ON-signal + 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal	Or 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal
Or 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal	Or 3.2us ON-signal + 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal
Or 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal	Or 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal + 3.2us ON-signal
Or 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal + 3.2us ON-signal	Or 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal
Or 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal + 3.2us OFF-signal	Or 3.2us OFF-signal + 3.2us ON-signal + 3.2us OFF-signal + 3.2us ON-signal
Or 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal + 3.2us OFF-signal	Or 3.2us OFF-signal + 3.2us OFF-signal + 3.2us ON-signal + 3.2us ON-signal
Or 3.2us OFF-signal + 3.2us OFF-signal + 3.2us ON-signal + 3.2us ON-signal	Or 3.2us ON-signal + 3.2us ON-signal + 3.2us OFF-signal + 3.2us OFF-signal

Table 7 does not indicate CP separately. Indeed, CP + 3.2us + CP + 3.2us + CP + 3.2us + CP + 3.2us or CP + 3.2us + 3.2us + 3.2us + 3.2us, including CP, may point to one single bit of information. That is, in the case of CP + 3.2us + CP + 3.2us + CP + 3.2us + CP + 3.2us, the 3.2us on signal can be regarded as (CP + 3.2us) on signal and the 3.2us off signal is (CP + 3.2us) off signal.

As another example, a symbol to which Manchester coding is applied based on symbol repetition may be represented by n (CP + 1.6us + CP + 1.6us) or CP + n (1.6us + 1.6us).

According to the above embodiment, a symbol is repeated using a symbol repeated n (> = 2) times, and a specific sequence is applied to all available subcarriers (for example, 13), and the remaining coefficients of 0 are applied. By setting IFFT, 3.2us of signal with 1.6us period is generated. Take one of these and set it as a 1.6us information signal (symbol).

The sub information may be called a 1.6us information signal. The 1.6us information signal may be a 1.6us on signal or a 1.6 off signal. The 1.6us on signal and the 1.6 off signal may have different sequences applied to each subcarrier. The 1.6us off signal can be generated by applying all coefficients to zero.

CP can be used by adopting a specific length from the back of the 1.6us of the information signal immediately after. At this time, CP may be 0.4us or 0.8us. This length is equal to the guard interval of 802.11ac.

Accordingly, 1 bit information corresponding to a symbol to which Manchester coding is applied based on the symbol repetition may be represented as shown in the following table.

Information ‘0’	Information ‘1’
(1.6us ON-signal + 1.6us OFF-signal) Repeat n times	(1.6us OFF-signal + 1.6us ON-signal) Repeat n times
Or (1.6us OFF-signal + 1.6us ON-signal) n times	Or (1.6us ON-signal + 1.6us OFF-signal) n times
(1.6us ON-signal + 1.6us OFF-signal) + (1.6us OFF-signal + 1.6us ON-signal) floor (n / 2) Repeat + if necessary (1.6us ON-signal + 1.6us OFF-signal)	(1.6us OFF-signal + 1.6us ON-signal) + (1.6us ON-signal + 1.6us OFF-signal) floor (n / 2) Repeat + if necessary (1.6us OFF-signal + 1.6us ON-signal)
(1.6us OFF-signal + 1.6us ON-signal) + (1.6us ON-signal + 1.6us OFF-signal) floor (n / 2) Repeat + if necessary (1.6us OFF-signal + 1.6us ON-signal)	(1.6us ON-signal + 1.6us OFF-signal) + (1.6us OFF-signal + 1.6us ON-signal) floor (n / 2) Repeat + if necessary (1.6us ON-signal + 1.6us OFF-signal)

Table 8 does not indicate CP separately. In fact, n (CP + 1.6us + CP + 1.6us) or CP + n (1.6us + 1.6us) including CP may indicate one 1-bit information. That is, in the case of n (CP + 1.6us + CP + 1.6us), the 1.6us on signal can be viewed as a (CP + 1.6us) on signal, and the 1.6us off signal is a (CP + 1.6us) off signal. Can be seen as.

Like the embodiments described above, the symbol repetition technique can satisfy the range requirement of low power wake-up communication. When only the OOK method is applied, the data rate for one symbol is 250 Kbps (4us). At this time, if the symbol is repeated twice using the symbol repetition technique, the data rate may be 125 Kbps (8us), and if the fourth repetition is performed, the data rate may be 62.5 Kbps (16us), and if the eight times are repeated, the data rate may be 31.25Kbps (32us). have. In the case of low-power wake-up communication, if there is no BCC, the symbol needs to be repeated eight times to satisfy the range requirement.

Hereinafter, various embodiments of a symbol to which a symbol reduction technique is applied among symbol types that can be used in the WUR will be described.

12 illustrates various examples of a symbol reduction technique according to the present embodiment.

According to the embodiment of FIG. 12, as the m value increases, the symbol is further reduced to reduce the length of a symbol carrying one piece of information. When m = 2, the length of a symbol carrying one piece of information becomes CP + 1.6us. When m = 4, the length of a symbol carrying one piece of information becomes CP + 0.8us. When m = 8, the length of a symbol carrying one piece of information becomes CP + 0.4us.

As the length of the symbol decreases, a high data rate can be ensured. If only the OOK scheme is applied, the data rate for one symbol is 250 Kbps (4us). In this case, using m = 2, the data rate is 500 Kbps (2us), if m = 4, the data rate is 1Mbps (1us), if m = 8 data rate can be 2Mbps (0.5us). .

For example, a symbol to which a symbol reduction technique is generally applied may be represented by CP + 3.2us / m (m = 2,4,8,16,32, ...) (option 1).

As shown in option 1 of FIG. 12, a symbol using a symbol reduction technique is used to represent one bit, and a specific sequence is applied to every available subcarrier (for example, 13) in m units, and the remaining coefficients are set to zero. do. Subsequently, if IFFT is applied to the subcarrier to which the specific sequence is applied, a 3.2us signal having a 3.2us / m period is generated. Take one of these and map it to the 3.2us / m information signal (information 1).

For example, if a specific sequence is applied in units of two columns (m = 2) to 13 subcarriers, the on signal may be configured as follows.

On signal (information 1): {a 0 b 0 c 0 d 0 e 0 f 0 g} or {0 a 0 b 0 c 0 d 0 e 0 f 0}, where a, b, c, d, e, f, g is 1 or -1.

As another example, if a specific sequence is applied to 13 subcarriers in units of four squares (m = 4), the on signal may be configured as follows.

On signal (Info 1): {a 0 0 0 b 0 0 0 c 0 0 0 d} or {0 a 0 0 0 b 0 0 0 c 0 0 0} or {0 0 a 0 0 0 b 0 0 0 c 0 0} or {0 0 0 a 0 0 0 b 0 0 0 c 0} or {0 0 a 0 0 0 0 0 0 0 b 0 0}, where a, b, c, d is 1 or -1.

As another example, if a specific sequence is applied to 13 subcarriers by 8 columns (m = 8), the on signal may be configured as follows.

On signal (information 1): {a 0 0 0 0 0 0 0 b 0 0 0 0} or {0 a 0 0 0 0 0 0 0 b 0 0 0} or {0 0 a 0 0 0 0 0 0 0 0 b 0 0} or {0 0 0 a 0 0 0 0 0 0 0 b 0}, or {0 0 0 0 a 0 0 0 0 0 0 0 b}, where a and b are 1 or -1 .

The 3.2us / m information signal is divided into a 3.2us / m on signal and a 3.2us / m off signal. In addition, different sequences may be applied to the (usable) subcarriers for the 3.2us / m on signal and the 3.2us / m off signal, respectively. A 3.2us / m off signal can be generated by applying all coefficients to zero.

CP can be used by adopting a specific length from the back of the information signal 3.2us / m immediately behind. At this time, CP may be 0.4us or 0.8us. This length is equal to the guard interval of 802.11ac. However, when m = 8, the CP cannot be 0.8us. Alternatively, CP may be 0.1us or 0.2us, or another value.

Accordingly, 1 bit information corresponding to a symbol to which a general symbol reduction technique is applied may be represented as shown in the following table.

Information ‘0’	Information ‘1’
3.2us / m OFF-signal	3.2us / m ON-signal

CP is not shown separately in Table 9. In fact, CP + 3.2us / m including CP may indicate one 1-bit information. That is, the 3.2us / m on signal may be viewed as a CP + 3.2us / m on signal, and the 3.2us / m off signal may be viewed as a CP + 3.2us / m off signal.

As another example, a symbol to which the symbol reduction technique is applied may be represented by CP + 3.2us / m + CP + 3.2us / m (m = 2,4,8) (option 2).

In the OOK transmission using the Wi-Fi transmitter, the time used for transmitting one bit (or symbol) except for the guard interval of the transmission signal is 3.2 us. At this time, if the symbol reduction technique is applied, the time used for one bit transmission is 3.2us / m. However, in this embodiment, the time used for transmitting one bit is repeated as 3.2us / m + 3.2us / m by repeating a symbol to which the symbol reduction technique is applied, and the signal between 3.2us / m signals is also used by using the characteristics of Manchester coding. A transition in size was allowed to occur. That is, each sub-information having a length of 3.2us / m should have a value of 0 or 1, and may configure a signal in the following manner.

* Information 0-> 1 0 (each can be referred to as sub information 1 0 or sub symbol 1 (ON) 0 (OFF))

First 3.2us / m signal (sub-information 1 or sub-symbol 1): A specific sequence in m-column for all available subcarriers (e.g. 13 subcarriers) to generate symbols with symbol reduction Apply. That is, in a particular sequence, coefficients may exist at intervals of m columns.

The transmitter maps a specific sequence to K consecutive subcarriers of 64 subcarriers and sets a coefficient to 0 for the remaining subcarriers to perform IFFT. In this way, signals in the time domain can be generated. Since the signal in the time domain has coefficients at intervals of m in the frequency domain, a 3.2us signal having a 3.2us / m period is generated. You can take one of these and use it as a 3.2us / m on signal (sub information 1).

Second 3.2us / m signal (sub information 0 or subsymbol 0): As with the first 3.2us / m signal, the transmitter maps a particular sequence to K consecutive subcarriers of 64 subcarriers, Can be generated to generate a time domain signal. The sub information 0 may correspond to a 3.2 us / m off signal. The 3.2us / m off signal can be generated by setting all coefficients to zero.

One of the first or second 3.2us / m periodic signals of the signal in the time domain may be selected and used as the sub information 0.

* Information 1-> 0 1 (each can be referred to as sub information '0', '1' or sub symbol 0 (OFF) 1 (ON))

-Since information 1 is also divided into the first 3.2us / m signal (sub information 0) and the second 3.2us / m signal (sub information 1), the signal corresponding to each sub information is generated in the same way as information 0 is generated. Can be configured.

In addition, information 0 may be configured as 01 and information 1 may be configured as 10.

As in option 2 of FIG. 12, 1-bit information corresponding to a symbol to which a symbol reduction technique is applied may be represented as shown in the following table.

Information ‘0’	Information ‘1’
3.2us / m OFF-signal + 3.2us / m ON-signal or 3.2us / m ON-signal + 3.2us / m OFF-signal	3.2us / m ON-signal + 3.2us / m OFF-signal or 3.2us / m OFF-signal + 3.2us / m ON-signal

In Table 10, CP is not separately indicated. In fact, CP + 3.2us / m including CP may indicate one 1-bit information. That is, the 3.2us / m on signal may be viewed as a CP + 3.2us / m on signal, and the 3.2us / m off signal may be viewed as a CP + 3.2us / m off signal.

Embodiments illustrated by option 1 and option 2 of FIG. 12 may be generalized as shown in the following table.

	Information ‘0’	Information ‘1’
Option 1 (m = 2,4,8)	2us OFF-signal	2us ON-signal
	1us OFF-signal	1us ON-signal
	0.5us OFF-signal	0.5us ON-signal
Option 2 (m = 4,8)	1us OFF-signal + 1us ON-signal or 1us ON-signal + 1us OFF-signal	1us ON-signal + 1us OFF-signal or 1us OFF-signal + 1us ON-signal
	0.5us OFF-signal + 0.5us ON-signal or 0.5us ON-signal + 0.5us OFF-signal	0.5us ON-signal + 0.5us OFF-signal or 0.5us OFF-signal + 0.5us ON-signal

Table 11 shows each signal in length including CP. That is, CP + 3.2us / m including the CP may indicate one 1-bit information.

For example, when m = 4 in Option 2, a symbol carrying one piece of information becomes CP + 0.8us, and thus a 1us off signal or 1us on signal is composed of a CP (0.2us) + 0.8us signal. In Option 2, since Manchester coding is applied and symbols are repeated, the data rate of one information can be 500 Kbps when m = 4.

As another example, when m = 8 in Option 2, a symbol carrying one piece of information becomes CP + 0.4us, and thus a 0.5us off signal or a 0.5us on signal is composed of a CP (0.1us) + 0.4us signal. In Option 2, since Manchester coding is applied and symbols are repeated, the data rate of one information may be 1Mbps when m = 8.

In the table below, the data rates that can be secured through the above-described embodiments are compared with each other.

CP	Default symbol (Example 1) (CP + 3.2us)	Man. Symbol (Example 2) (CP + 1.6 + CP + 1.6)	Man. Symbol (Example 3) (CP + 1.6 + 1.6)
0.4us	277.8	250.0	277.8
0.8us	250.0	208.3	250.0

CP	Symbol rep.n (CP + 3.2us)			CP rep.CP + n (3.2us)			Man. symbol rep.n (CP + 1.6us + CP + 1.6us)
	n = 2 (Example 4)	n = 3 (Example 5)	n = 4 (Example 6)	n = 2 (Example 7)	n = 3 (Example 8)	n = 4 (Example 9)	n = 2 (Example 10)	n = 3 (Example 11)	n = 4 (Example 12)
0.4us	138.9	92.6	69.4	147.1	100.0	75.8	125.0	83.3	62.5
0.8us	125.0	83.3	62.5	138.9	96.2	73.5	104.2	69.4	52.1

CP	Man. CP + n symbols (1.6us + 1.6us)			Symbol reductionCP + 3.2us / m
	n = 2 (Example 13)	n = 3 (Example 14)	n = 4 (Example 15)	m = 2 (Example 16)	m = 4 (Example 17)	m = 8 (Example 18)
0.4us	147.1	100.0	75.8	500.0	833.3	1250.0
0.8us	138.9	96.2	73.5	416.7	625.0	NA

CP	Symbol reductionCP + 3.2us / m		Man. symbol rep. w / Man.CP + 3.2us / m + CP + 3.2us / m
	m = 4	m = 8	m = 4	m = 8
0.1us	1111.1	2000	555.6	1000
0.2us	1000	1666.7	500	833.3

In addition, hereinafter, a scheme for configuring a wake-up preamble for timing synchronization in an 802.11ba system is proposed. In particular, a scheme for configuring a wakeup preamble using a periodic signal is proposed.

In the operation of the receiving end receiving the wake-up frame or the wake-up packet 600, time synchronization must be performed in order to obtain good performance. Thus, there is a need for the design of wake-up preambles for time synchronization. In this specification, a signal configuration of a wakeup preamble for time synchronization during a wakeup frame transmission is proposed. In particular, various embodiments in which a wake-up preamble consisting of a periodic signal is proposed and the above-described symbol reduction technique is applied will be described.

Fig. 13 shows an example of the structure of the wakeup frame according to the present embodiment.

The wakeup preamble 1310 may inform the start of the wakeup frame 1300, and may help perform time synchronization and decode the signal. In particular, the wakeup preamble 1310 may be used for acquiring channel information, measuring received signal power, and identifying an identifier. In particular, time synchronization can be performed by applying auto-correlation using the periodicity of the wake-up preamble 1310 or by applying cross-correlation using information about the sequence itself. It may be.

In addition, the wakeup preamble 1310 includes a first field 1312 and a second field 1314. The first field 1312 may be used to perform signal detection and time synchronization. The second field 1314 may be used to measure signal power and transmit simple control information.

In this specification, a preamble sequence having a periodicity for time synchronization is proposed, and in particular, a wake-up preamble including a signal having a period shorter than a symbol length is proposed as in the conventional Wi-Fi scheme. To this end, a wakeup preamble may be configured using a symbol reduction technique among symbol types for various data rates that may be considered in the wakeup payload 1320.

A wake-up preamble for synchronization can be constructed using signals of 0.4us, 0.8us or 1.6us produced by the symbol reduction technique. In particular, the transmitting device may configure the first field 1312 of the wake-up preamble for time synchronization. However, the symbol reduction scheme is not limited to the first field 1312 but may be applied to the configuration of other fields.

14 to 16 illustrate various examples of configuring the wake-up preamble using the periodic signal according to the present embodiment.

The wake-up preamble consists of a signal of 0.4us, 0.8us or 1.6us repeated several times, and may be configured by repeating different lengths. However, it is advantageous in terms of synchronization performance to repeat signals of the same length due to the characteristics of autocorrelation. In addition, the number of repeating signals should be two or more, and the longer the length, the better the synchronization performance, but the overhead may be increased. In addition to the wake-up preamble, one off symbol 4us may be positioned after repetition of the periodic signal. The one off symbol may be used for indicating wakeup frames as well as gain of synchronization performance.

14 shows an example of a preamble 1410 composed of five 1.6us signals and off symbols, an example of a preamble 1420 composed only of five 1.6us signals, and a preamble 1430 composed of ten 1.6us signals and off symbols. An example and an example of the preamble 1440 composed of only 10 1.6us signals are shown.

In Fig. 15, an example of a preamble 1510 consisting of five 0.8us signals and off symbols, an example of a preamble 1520 consisting only of five 0.8us signals, 10 or 15 or 20 0.8us signals and off symbols An example of the configured preamble 1530 and an example of the preamble 1540 composed of only 10 or 15 or 20 0.8us signals are shown.

In FIG. 16, an example of a preamble 1610 consisting of 10 or 20 or 30 or 40 0.4us signals and off symbols and a preamble 1620 consisting only of 10 or 20 or 30 or 40 0.4us signals An example is shown.

In the various embodiments of FIGS. 14 to 16, the preamble is composed of an 8us periodic signal (five 1.6us signals, ten 0.8us signals, and 20 0.4us signals) and one off symbol in consideration of synchronization performance and overhead. It may be desirable to construct. That is, when the preamble 1410 of FIG. 14 is used, when the preamble 1530 that uses 10 0.8us signals of FIG. 15 is used, the preamble 1610 that uses 20 0.4us signals of FIG. In this case, the best synchronization performance can be obtained considering the overhead.

In addition, hereinafter, a configuration method of a wake-up preamble for transmitting signal power measurement or simple control information in an 802.11ba system is proposed. In addition, embodiments of various preamble configurations utilizing various symbol types and the number of symbols will be described. Here, the signal power measurement is a value measured for calculating a threshold value used in signal decoding.

In particular, the present embodiment proposes a configuration method for the second field 1314 of the wake-up preamble shown in FIG. 13, and various embodiments of symbol types and control information that can be used to configure the second field are described. Suggest. In the present embodiment, the second field 1314 of the wake-up preamble is called a signal field, but may be used for a purpose different from that of the actual Wi-Fi signal. In addition, although the signal field of the present embodiment is said to belong to the wakeup preamble 1310 for convenience, it may be configured as another independent field or may belong to the wakeup payload 1320.

The control information included in the signal field may include the following information. The signal field only needs to indicate essential information for decoding the payload in order to reduce overhead and power consumption.

First, BSS color information (6 bits) may be carried in the signal field. By using the BSS color information, the receiving end may reduce power consumption by not reading the wakeup payload behind the wakeup frame unless it is the BSS. Various types of IDs (identifiers) as well as BSS color information may be carried in the signal field. Alternatively, a specific sequence indicating that the packet is a wakeup packet may be carried in the signal field.

In addition, the signal field may carry indication information regarding a symbol type or data rate used in the signal field and the wakeup payload. For example, two bits may be used to indicate the symbol type or data rate as follows.

Bit	00	01	10	11
Symbol type indication	Common OOK	Manchester coding based symbol	Two symbol repetition	1.6us symbol reduction
Data rate indication	250 kbps	250 Kbps (high data rate)	125 Kbps (low data rate)	500 Kbps

The table is only one example, and the order of each element may be different, may indicate different symbol types or data rates, and may indicate various symbol types or data rates by increasing or decreasing the number of bits. However, the following description will be given considering a field indicating a symbol type or a data rate using 2 bits.

The symbol type or data rate may be indicated to the STA capable of receiving wake-up upon capability negotiation between the AP and the STA rather than the wake-up frame.

In addition to the BSS color information and symbol type or data rate information, various information, such as a wakeup packet type, may be additionally loaded in the signal field. However, hereinafter, the configuration of the signal field will be described based on BSS color information and symbol type or data rate information for a simple example.

-When general OOK method is applied

First, a case may be considered in which the signal field is configured by a general OOK method regardless of the wakeup payload.

1) BSS color field (6 bits)

Here, the signal field consists only of 6 bits and consists of a general OOK. If the symbol type (or data rate) of the wakeup payload is not a general OOK, the first two bits of the wakeup payload may be used to indicate the symbol type (or data rate). The first two bits of the wakeup payload may consist of a typical OOK. Since there is no additional bit other than 6 bits in the signal field, it can consume the least power. In addition, the on-signal of the 6 bits may be used for signal power measurement.

2) Symbol Type field (2 bits) + BSS Color Field (6 bits)

In this case, the signal field may be configured as a general 8-bit OOK. The signal field may inform the symbol type (or data rate) of the wakeup payload in advance. Through this, it is possible to secure the time that the mode of the receiver transitions according to the change in symbol type (or data rate). In addition, there is an advantage in that the symbol type (or data rate) of the wakeup payload can be unified into one. Also, the 8-bit on signal may be used to measure signal power.

3) BSS color field (6 bits) + symbol type field (2 bits)

In this case, the signal field may be configured as a general 8-bit OOK. In addition, the signal field may inform the symbol type (or data rate) of the wake-up payload last. Using the signal field has the advantage of unifying the symbol type (or data rate) of the wakeup payload into one. Also, the 8-bit on signal may be used to measure signal power.

When symbol repetition technique is applied

For robust performance, the signal field may be configured only as a symbol repetition type. It can be composed of the same fields as the field configuration when the general OOK method is applied (1) BSS color field (6 bits) / 2) symbol type field (2 bits) + BSS color field (6 bits) / 3) BSS Color field (6 bits) + symbol type field (2 bits)). However, the overhead increases linearly with the number of repeated symbols. If the signal field consists only of the BSS color field, as in the case of 1) when the general OOK scheme is applied, the first two bits of the wakeup payload will be used to indicate the symbol type (or data rate) of the wakeup payload. Can be. The first two bits of the wakeup payload may consist of symbol repetition.

When configured with the same symbol type as the wakeup payload

A signal field configured with the same symbol type (or data rate) as the wakeup payload may be configured. However, the symbol type may be composed of a general OOK or symbol repetition for robust performance.

1) Symbol Type field (2 bits) + BSS Color Field (6 bits)

In this case, the signal field may consist of a general 8-bit OOK or symbol repetition. In addition, the signal field may be composed of a 6-bit BSS color field configured with the same symbol type as the wake-up payload indicated by the symbol type field and the symbol type field indicated in advance in the capability negotiation. Through such a configuration, there is an advantage in that the symbol type (or data rate) of the wakeup payload can be unified into one. Also, the 8-bit on signal may be used to measure signal power.

When configured with various symbol types regardless of wakeup payload

The signal field may consist of various symbol types regardless of the symbol type (or data rate) of the wakeup payload. In this case, the signal field may include a signal symbol type field indicating a symbol type of the signal field and a payload symbol type field indicating a symbol type of the wakeup payload.

1) Signal symbol type field (2 bits) + BSS color field (6 bits)

In this case, the signal field may consist of a general 8-bit OOK or symbol repetition. In addition, the signal field may be configured with a 6-bit BSS color field configured with a symbol type indicated by a signal symbol type field and a symbol type indicated by a signal symbol type field. In this case, the payload symbol type field may be located in the first two bits of the wakeup payload. In addition, the payload symbol type field may consist of a general OOK or a symbol type indicated in the signal symbol type field. Alternatively, the payload symbol type field may be configured with a symbol type indicated in advance in capability negotiation. In this embodiment, power consumption may be the least among two symbol type fields, a signal symbol type field and a payload symbol type field. Also, the 8-bit on signal may be used to measure signal power.

2) Signal symbol type field (2 bits) + Payload symbol type field (2 bits) + BSS color field (6 bits)

Here, the signal field may consist of a 10-bit general OOK or symbol repetition. In addition, the signal field is composed of a 2-bit payload symbol type field consisting of a symbol type indicated by a symbol type indicated in a signal symbol type field, a signal symbol type field previously indicated at the time of capability negotiation, and a 6-bit BSS color field. Can be. In this case, it is possible to secure a time for the mode of the receiver to transition according to the change of the payload symbol type. In addition, the symbol type of the wake-up payload can be unified to one. In addition, the signal may be used for signal power measurement by using an on signal among the 10 bits.

3) Signal symbol type field (2 bits) + BSS color field (6 bits) + Payload symbol type field (2 bits)

Here, the signal field may consist of a 10-bit general OOK or symbol repetition. In addition, the signal field is composed of a 6-bit BSS color field and a 2-bit payload symbol type field configured as a symbol symbol field composed of a symbol type indicated in advance in the capability negotiation, a symbol type indicated by the signal symbol type field. Can be. In this case, the symbol type of the wakeup payload may be unified into one. In addition, the signal may be used for signal power measurement by using an on signal among the 10 bits.

Hereinafter, as another embodiment, a method of configuring a signal field into a sequence and indicating that the sequence indicates a symbol type or data rate will be described. The sequence constituting the signal field may correspond to a signature sequence.

Since the signal field may be configured with a BSS color or various IDs, the signal field may be configured with a sequence corresponding to the ID. In addition, the sequence field may be configured by simply forming a symbol (sequence) with 101010... To indicate that it is a wake-up packet. Of course, the wakeup packet may be indicated using a specific type of sequence consisting of 0 or 1. In this case, 1 and 0 mean information that the symbol informs, and may simply be an on symbol or an off symbol, or a symbol to which Manchester coding is applied.

In addition, if only two symbol types are used in the wake-up payload, the signal field is configured with 010101 ..., the opposite of 101010 ... to indicate the wake-up packet and indicate the symbol type (or data rate). can do.

It is also possible to add a symbol to the sequence of 101010 ... to indicate the symbol type. If it consists of a specific ID (for example, 100100 or other value) and only two symbol types of the wake-up payload are used, the ID consists of two sequences of 100100 and 011011 as follows: (Or BSS color) and symbol type (or data rate). The two sequences 100100 and 011011 may be complementary.

In addition, the symbol type may be announced by using one symbol at the beginning or the end of the sequence that announces the ID. As such, the signal field may be configured by simultaneously loading ID or wake-up indication information and symbol type information (or data rate information) in the sequence.

If you use three or four symbol types (or data rates) in your wake-up payload, add the first or last symbol to 010101 ..., the opposite of 101010 ..., to add two bits of information (symbol type). Or data rate). For example, if you add the first symbol: 1 101010 ..., 0 101010 ..., 1 010101 ..., 0 010101… You can use the sequence of. As another example, if you add the last symbol… 101010 1 ,. 010101 1 ,. 101010 0 ,. 010101 A sequence of 0 can be used.

If the sequence consists of a specific ID (for example, 100100), add 1 symbol at the beginning and end to add 1 100100, 1 011011, 0 100100, 0 011011 or 100100 1 , 011011 1 , 100100 0 , 011011 0 Like a sequence, two bits of information (symbol type or data rate) can be announced.

In addition, two symbols may be added at the beginning or the end of the sequence to indicate the symbol type (or data rate).

Alternatively, two bit information may be reported by a combination of two sequences. For example, assuming that two sequences 101 and 010 are used, two bits of information (symbol type or data rate) may be reported using 101010, 101101, 010010, and 010101.

In addition, the configuration of a sequence can be generally described as follows.

Pa = (a1 a2 a3 a4... }, Pa_hat = {a1_hat a2_hat a3_hat a4_hat… }

Pb = {b1 b2 b3 b4... }, Pb_hat = {b1_hat b2_hat b3_hat b4_hat… }

Pc = {c1 c2 c3 c4... }, Pc_hat = {c1_hat c2_hat c3_hat c4_hat… }

… ..

an, bn, cn,… = 0 or 1 for n = 1, 2, 3, 4,...

an_hat = 0 or 1 if an = 1 or 0

bn_hat = 0 or 1 if bn = 1 or 0

cn_hat = 0 or 1 if cn = 1 or 0

… .

That is, Pa and Pa_hat, Pb and Pb_hat, Pc and Pc_hat may be complementary to each other.

In addition, one-bit information can be reported using Pa and Pa_hat or Pb and Pb_hat or Pc and Pc_hat. That is, it may be represented by {Pa}, {Pa_hat} or {Pb}, {Pb_hat} or {Pc}, {Pc_hat}.

In addition, two bits of information can be reported using Pa, Pa_hat, Pb, and Pb_hat, as well as a and b as well as various alphabet combinations. That is, {Pa Pb}, {Pa_hat Pb}, {Pa Pb_hat}, {Pa_hat Pb_hat}.

In addition, multi-bit information can be reported using Pa, Pa_hat, Pb, Pb_hat, Pc, Pc_hat, etc. As well as a, b, and c, various alphabet combinations are possible. Namely, {Pa Pb Pc... }, {Pa_hat Pb Pc…. }, {Pa Pb_hat Pc…. }, {Pa Pb Pc_hat… },… {Pa_hat Pb_hat Pc_hat… }.

In addition, a sequence may be constructed using elements of the P matrix of the existing Wi-Fi as follows.

Here, P _4x4 may correspond to P _HT-LTF .

In Equation 1, information 1 may be interpreted as -1 information 0 and vice versa. According to the number of symbol types, a sequence obtained by selecting a row from P _4X4 or P _8X8 may be used as an indicator of each symbol type. For example, if three symbol types are used and P _8X8 is applied, the first three columns may be extracted to form a sequence to indicate three symbol types as follows.

Symbol Type 1: 10111011

Symbol Type 2: 11011101

Symbol Type 3: 11101110

The sequence indicating the symbol type is merely an example and may indicate the symbol type in other combinations.

Alternatively, a variety of sequences, such as a Barker sequence and a Golay sequence, may be used to indicate symbol types.

Although described above based on the indication of the symbol type, various types of information (such as information on data rate) other than the symbol type may be transmitted in the signal field by applying the same method.

17 is a flowchart illustrating a procedure of indicating a data rate through a wakeup preamble by applying the OOK scheme according to the present embodiment.

An example of FIG. 17 is performed in a transmitter, the receiver may correspond to a low power wake-up receiver, and the transmitter may correspond to an AP.

First of all, the term “on signal” may correspond to a signal having an actual power value. The off signal may correspond to a signal that does not have an actual power value.

In step S1710, the transmitter configures a wake-up packet to which the On-Off Keying (OOK) scheme is applied.

In operation S1720, the transmitter transmits the wakeup packet to the receiver.

How the wakeup packet is configured is as follows.

The wakeup packet includes a wakeup preamble and a wakeup payload. In other words, a OOK scheme may be applied to the wakeup preamble and the wakeup payload.

The wakeup preamble includes a preamble sequence consisting of an on signal and an off signal. The preamble sequence may correspond to a signature sequence. The on signal may indicate 1, and the off signal may indicate 0.

The on signal is transmitted through an on symbol generated by applying a first sequence to 13 consecutive subcarriers in a 20 MHz band and performing a 64-point Inverse Fast Fourier Transform (IFFT). That is, the on signal may correspond to one bit and may be transmitted through one symbol generated by performing an IFFT.

Information about the data rate of the wakeup payload is indicated using the preamble sequence. That is, information on the data rate of the wakeup payload may be indicated through a sequence configured in the wakeup preamble.

Various embodiments of indicating a data rate of a wake-up payload through the preamble sequence are as follows.

For example, the preamble sequence may indicate that the data rate of the wakeup payload is a lower data rate than a reference value. In addition, the complementary sequence of the preamble sequence may indicate that the data rate of the wake-up payload is a higher data rate than a reference value.

When the data rate of the wakeup payload is lower than the reference value, a symbol repetition technique may be applied in which the wakeup payload is repeatedly transmitted n times the on signal or the off signal. N may be an integer of at least two. As the number of symbols is repeated, the data rate of the wake-up payload is lowered. The cross-correlation value of the preamble sequence may be obtained as a negative peak. That is, cross correlation may be performed using only the preamble sequence.

When the data rate of the wakeup payload is higher than the reference value, Manchester coding may be applied to the wakeup payload. The Manchester coding is configured to configure the on signal or the off signal based on a sequence in which coefficients exist only in subcarriers having an even subcarrier index or an even subcarrier in odd subcarrier indexes. May be a coding technique. The cross-correlation value of the preamble sequence may be obtained as a positive peak.

The reference value may be a data rate value of the wakeup payload when the wakeup payload is applied only to the OOK scheme. That is, if the data rate of the wake-up payload is greater than or equal to the reference value, it may be regarded as corresponding to a high data rate. If the data rate of the wake-up payload is lower than the reference value, it may be regarded as corresponding to a low data rate.

As another example, the information on the data rate of the wakeup payload may be indicated using a sequence in which one symbol is added before the preamble sequence. The on signal or the off signal may be transmitted in one symbol added before the preamble sequence.

As another example, information about the data rate of the wakeup payload may be indicated by using a sequence in which one symbol is added after the preamble sequence. The on signal or the off signal may be transmitted in one symbol added after the preamble sequence.

As another example, the information on the data rate of the wakeup payload may be indicated by using a combination of the preamble sequence and the complementary sequence of the preamble sequence. For example, when the sequence of the preamble is 101, the complementary sequence of the preamble sequence may be 010. The sequence of 101010, 101101, 010010, and 010101 combining the two sequences may indicate the data rate of the wakeup payload.

As another example, the sequence of repeating the preamble sequence twice may indicate that the data rate of the wakeup payload is lower than a reference value. The complementary sequence of the preamble sequence may indicate that the data rate of the wakeup payload is a data rate higher than a reference value.

The preamble sequence may be configured based on a basic service set (BSS) color. The BSS color may be signaled through a physical layer. That is, the BSS color may not be transmitted through the signal field.

The wakeup preamble may further include a synchronization sequence including the on signal or the off signal. In other words, in the wake-up preamble, a synchronization sequence may be used to perform time synchronization, and the preamble sequence may be used to indicate a data rate.

The on signal of the synchronization sequence may be transmitted repeatedly n times. The off signal of the sync sequence may be transmitted in the last symbol of the sync sequence. N may be an integer of at least two.

The on signal of the synchronization sequence may be configured based on a sequence in which the coefficients of the subcarriers are set to 1 or -1 and the coefficients of the remaining subcarriers are set to 0 in units of m subcarriers in the 13 subcarriers.

That is, if m = 2, an on-signal is constructed based on a sequence in which subcarrier coefficients exist in units of two spaces, and if m = 4, an on-signal is constructed in accordance with a sequence in which subcarrier coefficients exist in units of four columns. If m = 8, the on-signal may be configured based on a sequence in which subcarrier coefficients exist in units of eight columns. M is a natural number and may correspond to an even number as a value for decreasing a symbol.

This is to generate an information signal (or symbol) applying a symbol reduction technique. When a first sequence is applied to 13 subcarriers having coefficients of a subcarrier in units of m subcarriers and IFFT is performed, a 3.2us signal having a 3.2us / m period is generated. You can take one of these to construct a 3.2us / m on signal. The 3.2us / m on signal may be transmitted through the on symbol. Accordingly, the on symbol may have a length of 3.2 us / m except for CP. As a result, the length of the symbol may be reduced and the data rate may be increased instead of the conventional OOK method.

If m is 2, the length of the on symbol to which the on signal of the synchronization sequence is transmitted is 1.6us and n may be 5. If m is 4, the length of the on symbol on which the on signal of the synchronization sequence is transmitted is 0.8us and n may be 10. If m is 8, the length of an on symbol on which the on signal of the synchronization sequence is transmitted is 0.4us and n may be 20.

Increasing the number of repetitions of the on-signal may be advantageous in terms of time synchronization performance, but may increase overhead. Therefore, the n value may be determined in consideration of both time synchronization performance and overhead generation. In particular, the total length of the repeated on symbol may be set to be a multiple of 4 us.

In addition, the transmitter may first configure power values of the on signal and the off signal, and configure the on signal and the off signal. The receiver decodes the on signal and the off signal using an envelope detector, thereby reducing power consumed in decoding.

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

Referring to FIG. 18, the wireless device may be an AP or a non-AP station (STA) that may implement the above-described embodiment. The wireless device may correspond to the above-described user or may correspond to a transmission device 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. That is, the processor 1810 may perform an operation that may be performed by the AP during the operations disclosed in the embodiments 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 this 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 may perform the operation of the non-AP STA in the 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 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.

Claims (14)

1. In a method for transmitting a wake-up packet in a wireless LAN system,

   Configuring, by the transmitter, a wake-up packet to which an On-Off Keying (OOK) scheme is applied; And

   Transmitting, by the transmitter, the wakeup packet to a receiver;

   The wakeup packet includes a wakeup preamble and a wakeup payload,

   The wakeup preamble includes a preamble sequence composed of an on signal and an off signal.

   The on signal is transmitted through an on symbol generated by applying a first sequence to 13 consecutive subcarriers in a 20 MHz band and performing a 64-point Inverse Fast Fourier Transform (IFFT).

   Information on the data rate of the wakeup payload is indicated using the preamble sequence.

   Way.
2. The method of claim 1,

   The preamble sequence indicates that a data rate of the wakeup payload is a low data rate lower than a reference value, and

   A complementary sequence of the preamble sequence indicates that a data rate of the wakeup payload is a higher data rate than a reference value.

   Way.
3. The method of claim 2,

   If the data rate of the wake-up payload is lower than the reference value,

   The wake-up payload is applied with a symbol repetition technique of repeatedly transmitting the on signal or the off signal n times.

   N is an integer of at least 2, and

   The cross-correlation value of the preamble sequence is obtained as a negative peak.

   Way.
4. The method of claim 2,

   If the data rate of the wake-up payload is higher than the reference value,

   The wakeup payload is subjected to Manchester coding,

   The Manchester coding is configured to configure the on signal or the off signal based on a sequence in which coefficients exist only in subcarriers having an even subcarrier index or an even subcarrier in odd subcarrier indexes. Coding techniques, and

   The cross-correlation value of the preamble sequence is obtained as a positive peak.

   Way.
5. The method of claim 2,

   The reference value is a data rate value of the wakeup payload when the wakeup payload is applied only to the OOK scheme.

   Way.
6. The method of claim 1,

   Information on the data rate of the wakeup payload is indicated by using a sequence in which one symbol is added before the preamble sequence,

   The on signal or the off signal is transmitted in one symbol added before the preamble sequence

   Way.
7. The method of claim 1,

   Information on the data rate of the wake-up payload is indicated using a sequence in which one symbol is added after the preamble sequence,

   The on signal or the off signal is transmitted in one symbol added after the preamble sequence

   Way.
8. The method of claim 1,

   Information on the data rate of the wakeup payload is indicated using a sequence combining the preamble sequence and the complementary sequence of the preamble sequence.

   Way.
9. The method of claim 1,

   A sequence of repeating the preamble sequence twice indicates that a data rate of the wakeup payload is a data rate lower than a reference value, and

   The complementary sequence of the preamble sequence indicates that the data rate of the wakeup payload is a data rate higher than a reference value.

   Way.
10. The method of claim 1,

    The preamble sequence is configured based on BSS (Basic Service Set) color,

    The BSS color is signaled through a physical layer

    Way.
11. The method of claim 1,

    The wakeup preamble further includes a synchronization sequence composed of the on signal or the off signal,

    The on signal of the synchronization sequence is repeatedly transmitted n times,

    The off signal of the sync sequence is transmitted in the last symbol of the sync sequence,

    N is an integer of at least 2

    Way.
12. The method of claim 11,

    The on signal of the synchronization sequence is configured based on a sequence in which the coefficients of the subcarriers are set to 1 or -1 and the coefficients of the remaining subcarriers are set to 0 in units of m subcarriers in the 13 subcarriers, and

    M is a natural number

    Way.
13. The method of claim 12,

    If m is 2, the length of the on symbol to which the on signal of the synchronization sequence is transmitted is 1.6us and n is 5,

    If m is 4, the length of the on symbol to which the on signal of the synchronization sequence is transmitted is 0.8us and n is 10, and

    If m is 8, the length of the on symbol on which the on signal of the synchronization sequence is transmitted is 0.4us and n is 20.

    Way.
14. A transmitter for transmitting a wake-up packet in a wireless LAN system,

    RF unit for transmitting or receiving a wireless signal; And

    A processor for controlling the RF unit, wherein the processor:

    Configure a wake-up packet to which an On-Off Keying (OOK) scheme is applied, and

    The wakeup packet is transmitted to a receiving device,

    The wakeup packet includes a wakeup preamble and a wakeup payload,

    The wakeup preamble includes a preamble sequence composed of an on signal and an off signal.

    The on signal is transmitted through an on symbol generated by applying a first sequence to 13 consecutive subcarriers in a 20 MHz band and performing a 64-point Inverse Fast Fourier Transform (IFFT).

    Information on the data rate of the wakeup payload is indicated using the preamble sequence.

    Transmitter.

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