Patent Description:
A terminal device in a wireless local area network (WLAN) may enter a sleep mode. However, the terminal device in the sleep mode also needs to frequently enter an awake state from a doze state to receive data.

<CIT> discloses apparatus comprising processing circuitry configured to encode a wake-up packet to be transmitted on one or more sub-channels to one or more low-power wake-up receivers (LP-WURs), where each of the wake-up packets are to be <NUM> data tones or <NUM> data tones, where the wake-up packet comprises one or more wake-up pulses; and cause to be transmitted the one or more wake-up packets on the one or more sub-channels.

<CIT> discloses various wake-up procedures for user equipments (UEs). A UE may include a low power wake-up radio (LP-WUR) separate from a front end module (FEM). The LP-WUR may remain awake continuously (or at high-frequency intervals) and monitor for a wakeup signal, allowing the FEM to remain powered down in the absence of downlink data. When the LP-WUR detects a wakeup signal configured for the LP-WUR, the LP-WUR may be configured to wake up the FEM to receive incoming downlink data.

<CIT> discloses apparatuses, devices, systems and methods of communicating a wakeup packet. For example, an apparatus may include circuitry configured to cause a wireless device to generate a frame comprising a Low-Power Wakeup-Receiver (LP-WUR) capability indication to indicate a capability of the wireless device to process communication of a wakeup packet; and to transmit the frame.

<CIT> discloses a station, a method performed by a station and a corresponding method performed by an access point (AP) of a network to allow the station to operate a wireless local area network (WLAN) radio in a sleep state until the WLAN radio is ready to receive a beacon from the AP. The station includes a low power (LP) radio configured to receive a wake up signal from an AP of a network to which the station is connected. The station further includes a WLAN radio configured to operate in a sleep state until the WLAN radio receives an indication from the LP radio that the wakeup signal has been received, wherein WLAN radio is further configured to operate in a fully awake state after receipt of the indication to receive a beacon from the AP indicating a data transmission is pending for the station.

<CIT> discloses a power saving station integrates a low power consumption wake-up receiver with wideband wireless of main radio. The low power wake-up receiver of power saving station receives a wake-up request signal sent from the wireless network and wakes up the main radio of the station to communicate with the wireless network over wideband frequency channel. The wake-up request signal is transmitted over a narrow band frequency channel and can be addressed to a single station or multiple of stations via OFDMA in wideband channel.

<CIT> discloses techniques for allowing a wireless device to wake up a low power device while remaining compatible with other devices and wireless protocols. A first station determines that a low power device needs to wake up all or a portion of its circuitry in order to send and/or receive data from the first station. The first station sends a legacy preamble according to a standard wireless communication method such as according to IEEE <NUM> or Bluetooth addressed to the low power device. Legacy stations will recognize that a device is accessing the medium and will abstain from transmitting data during the transaction(s) between the first station and the low power device. The first station then sends a wake up payload according to a low power wireless communication method such as ASK or FSK to the low power device. The low power device recognizes the wake up payload and wakes up its main radio such as an IEEE <NUM> or Bluetooth radio. The first station sends and/or receives data to/from the low power device according to the standard wireless communication method. If there is no more data to send or receive, low power device powers down at least its main radio. <CIT> discloses methods and stations for wireless communication are described herein. In some aspects, the station may include a processing circuit configured to process a first signal transmitted to the station, the first signal indicating a target wake up time when an activation signal is expected to be received. The station may further include a wake-up circuit configured to transition a first receiver to an awake state based on the indicated target wake up time. The first receiver is configured to receive the activation signal at the indicated target wake up time. The station may further include a second receiver configured to transition to an awake state based on the first receiver receiving the activation signal and receive a second signal while in the awake state. <CIT> discloses a low-power radio communication system comprising a control unit that starts transmission of a beacon signal when a wake-up signal addressed to the terminal is detected.

This application provides a wireless access point, a terminal device, and a method for waking up a terminal device, so as to reduce power consumption of a terminal device.

Embodiments and examples not covered by the claims are meant to illustrate, and facilitate the understanding of, the claimed invention.

According to a first aspect, a terminal device according to claim <NUM> is provided.

According to a second aspect, a method for waking up a terminal device according to independent claim <NUM> is provided. The method includes the steps performed by the terminal device in the first aspect.

According to a third aspect, a method for waking up a terminal device according to independent claim <NUM> is provided.

According to a fourth aspect, an apparatus for waking up a terminal device according to independent claim <NUM> is provided.

Further aspects are provided by the dependent claims.

The following describes the embodiments of the present invention with reference to <FIG>.

In an internet of things scenario, many devices need to be powered by batteries. Therefore, it is quite important to prolong lifespans (battery lifespans) of the devices. Because a WLAN device is highly popularized, if the WLAN device can be used to implement functions required by the internet of things scenario, a threshold for popularizing the internet of things can be reduced.

The WLAN device may enter a sleep mode. However, a terminal device in the sleep mode also needs to frequently enter an awake state from a doze state, to receive data of another WLAN device (for example, a wireless access point (AP) or a WLAN device of another type). A longer time in which a device stays in the doze state contributes to less consumed energy. However, staying in the doze state for a long time reduces timely performance of data transmission.

To reduce power consumption of the WLAN device as much as possible and meet a requirement for timely performance of data transmission, a dedicated wake-up radio (WUR) radio frequency circuit other than a primary radio frequency (RF) circuit is disposed in the WLAN device in the embodiments of the present invention. The WLAN device on which the WUR radio frequency circuit is disposed is referred to as a WUR terminal device or a terminal device. The WUR radio frequency circuit can only receive a radio signal and cannot send a radio signal. The WUR radio frequency circuit is only configured to receive a frame (which may be referred to as a WUR frame such as a WUR beacon frame or a WUR wake-up frame) related to a wake-up operation, and ignores other frames (for example, a data frame). Therefore, power consumption and complexity of the WUR radio frequency circuit are low. Power consumption of the WUR radio frequency circuit that is generated during operating may be less than <NUM> microwatts (µW). The primary radio frequency circuit and the WUR radio frequency circuit may be separate, or may be integrated into a chip.

When there is no data that is to be transmitted, the terminal device is in a sleep state. When the terminal device is in the sleep state, the primary radio frequency circuit is disconnected for energy saving. When the terminal device is in the sleep state, the WUR radio frequency circuit listens to a wireless medium, to receive a wake-up frame in time. Optionally, the WUR radio frequency circuit may suspend operating for further energy saving. For example, the WUR radio frequency circuit may periodically suspend operating. Further, when the terminal device is in the sleep state, any component except the WUR radio frequency circuit in the entire device may be in a power-off state. If the terminal device includes a volatile memory, the volatile memory may not be in the power-off state when the terminal device is in the sleep state. Alternatively, the terminal device may copy content in the volatile memory to a non-volatile memory before entering the sleep state, and then disable the volatile memory when entering the sleep state.

When the WLAN device needs to send data to a terminal device, or needs to query data of a terminal device, the WLAN device first sends a wake-up frame. After receiving the wake-up frame, a WUR radio frequency circuit of a to-be-woken-up terminal device wakes up a primary radio frequency circuit of the terminal device. In this case, the terminal device is in the awake state. After sending the wake-up frame, the WLAN device sends a WLAN frame. The WLAN frame may be a data frame or a management frame. The data frame may include an indication for sending the data to the terminal device by the WLAN device or querying the data of the terminal device.

In an example in which the WLAN device is a wireless AP, to reduce interference between wireless APs, adjacent wireless APs usually operate on different operating channels. If wireless APs send WUR frames on respective operating channels, adjacent wireless APs send WUR frames on different channels.

After a terminal device moves from a coverage area of an original wireless AP to a coverage area of an adjacent wireless AP, because the terminal device does not know an operating channel of the new wireless AP, the terminal device can only switch to an operating channel of a WUR radio frequency circuit, to attempt to listen to a WUR frame sent by the new wireless AP. WLAN bands include a <NUM> megahertz (MHz) band, a <NUM> gigahertz (GHz) band, a <NUM> band, a <NUM> band, a <NUM> band, a <NUM> band, a <NUM> band, and the like. Quantities of WLAN channels included in different WLAN bands are specified by regulations of each country/region. For example, there are <NUM> channels with a bandwidth of <NUM> in the <NUM> band in the United States. Because the terminal device does not know the operating channel of the new wireless AP, the operating channel of the WUR radio frequency circuit of the terminal device needs to be frequently switched, to find the operating channel of the new wireless AP from the <NUM> channels. Frequent channel switching increases power consumption of the WUR radio frequency circuit.

If a plurality of wireless APs in one area send WUR frames on a same channel, when the terminal device randomly moves in the area, the WUR radio frequency circuit of the terminal device may listen to the WUR frame sent by the new wireless AP without a need to perform channel switching.

<FIG> is a schematic diagram of a network architecture according to an embodiment of the present invention.

In <FIG>, there are a plurality of wireless devices, namely, a WLAN device <NUM> to a WLAN device <NUM>.

In this embodiment of the present invention, although operating channels of the WLAN device <NUM> to the WLAN device <NUM> are different, the WLAN device <NUM> to the WLAN device <NUM> send WUR frames on a same specified channel (a channel <NUM> (CH <NUM>)). When a terminal device <NUM> randomly moves in coverage areas of the WLAN device <NUM> to the WLAN device <NUM>, a WUR radio frequency circuit of the terminal device <NUM> may listen to a WUR frame sent by any wireless AP without a need to perform channel switching. Alternatively, after any WLAN device fails to send a wake-up frame on an operating channel of the WLAN device, the WLAN device sends the wake-up frame on the specified channel (the channel <NUM>). After the terminal device <NUM> leaves a coverage area of an original WLAN device, the WUR radio frequency circuit of the terminal device <NUM> may listen to a WUR frame sent by any wireless AP, provided that the WUR radio frequency circuit of the terminal device <NUM> is switched to the specified channel.

<FIG> is a schematic diagram of waking up a terminal device by a WLAN device according to an embodiment of the present invention.

An example in which a WLAN device <NUM> wakes up a terminal device <NUM> is used in <FIG>, to describe a process in this embodiment of the present invention.

The WLAN device <NUM> includes a processor <NUM> and a transceiver <NUM>. The processor <NUM> may include a central processing unit (CPU), a network processor (NP), a radio frequency circuit, an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or any combination thereof. The PLD may be a complex programmable logic device (CPLD), a field programmable gate array (FPGA), generic array logic (GAL), or any combination thereof. The radio frequency circuit is also referred to as an RF module, and is an electronic component for sending and/or receiving a radio signal between devices. The circuits in the processor may be separate, or may be integrated into one or more chips.

The transceiver <NUM> may be an antenna. The antenna may include an array antenna, a multi-band antenna, a microstrip antenna, a directional antenna, or any antenna of another type. The processor <NUM> receives and sends a radio signal by using the transceiver <NUM>.

Optionally, the WLAN device <NUM> further includes a memory. The memory may be a separate device, or may be integrated into the processor <NUM>. The memory may include a volatile memory such as a random access memory (RAM). The memory may alternatively include a non-volatile memory such as a read-only memory (ROM), a flash memory, an optical disc, a magnetic tape, a floppy disk, a hard disk, or a solid-state drive. The memory may alternatively include any combination of the foregoing types of memories. If the processor <NUM> needs program code, the memory may store program code and transmit the program code to the processor <NUM>, so that the processor <NUM> implements this embodiment of the present invention according to an indication of the program code.

The terminal device <NUM> includes a primary radio frequency circuit <NUM> and a WUR radio frequency circuit <NUM>. There may be one or more primary radio frequency circuits <NUM>. There may be one or more WUR radio frequency circuits <NUM>. For example, an operating band of the primary radio frequency circuit <NUM> is the same as an operating band of the WUR radio frequency circuit <NUM>. If the terminal device <NUM> includes a plurality of primary radio frequency circuits <NUM> with different operating bands, the terminal device <NUM> may include a plurality of WUR radio frequency circuits <NUM> with corresponding operating bands. For another example, two or more primary radio frequency circuits <NUM> with different operating bands may be woken up by one WUR radio frequency circuit <NUM>. The primary radio frequency circuit <NUM> and the WUR radio frequency circuit <NUM> may share an antenna. The primary radio frequency circuit <NUM> and the WUR radio frequency circuit <NUM> may alternatively use respective antennas. The following describes this embodiment of the present invention by using a <NUM> band as an example. This embodiment of the present invention may also be applied to another band.

The primary radio frequency circuit <NUM> is a radio frequency circuit of the terminal device <NUM> for receiving and sending WLAN data. An operating channel of the primary radio frequency circuit <NUM> may be referred to as a primary connectivity radio channel.

The WUR radio frequency circuit <NUM> is a radio frequency circuit of the terminal device <NUM> for receiving a WUR frame. The WUR radio frequency circuit <NUM> includes only a receiver and does not include a transmitter. Therefore, the WUR radio frequency circuit can only receive a radio signal and cannot send a radio signal. An operating channel of the WUR radio frequency circuit <NUM> may be referred to as a WUR channel. The WUR radio frequency circuit <NUM> uses a specified channel as the WUR channel. Alternatively, the WUR channel includes a primary WUR channel and a secondary WUR channel. The primary WUR channel is the operating channel of the primary radio frequency circuit <NUM>, and the secondary WUR channel is the specified channel. If the WLAN device <NUM> fails to send a wake-up frame on the primary WUR channel, the WLAN device <NUM> switches to the secondary WUR channel, to send the wake-up frame. If the terminal device <NUM> listens and obtains no WUR beacon frame on the primary WUR channel for a long time, the terminal device <NUM> switches to the secondary WUR channel, to listen to a wireless medium. The specified channel is a same channel on which a plurality of APs send WUR frames.

Optionally, the terminal device <NUM> may further include a processor. The processor may include a CPU, an NP, an ASIC, a PLD, or any combination thereof. Optionally, the terminal device <NUM> may further include a memory. The memory may include a volatile memory such as a random access memory (RAM). The memory may alternatively include a non-volatile memory such as a read-only memory (ROM), a flash memory, an optical disc, a magnetic tape, a floppy disk, a hard disk, or a solid-state drive. The memory may alternatively include any combination of the foregoing types of memories. The primary radio frequency circuit <NUM>, the WUR radio frequency circuit <NUM>, the processor (if any), and the memory (if any) may be separate chips, or may be integrated into one or more chips.

A process of waking up the terminal device <NUM> by the WLAN device <NUM> is as follows:
<NUM>. The WLAN device <NUM> sends information about a specified channel on an operating channel of the WLAN device <NUM>, and after receiving the information about the specified channel, a primary radio frequency circuit of the terminal device <NUM> configures a specified channel of a WUR radio frequency circuit based on the information.

For example, the WLAN device <NUM> is the WLAN device <NUM> in <FIG>, and the terminal device <NUM> is the terminal device <NUM> in <FIG>. The operating channel of the WLAN device <NUM> is a channel <NUM>, and the specified channel of the WLAN device <NUM> is a channel <NUM>. The specified channel of the WLAN device <NUM> may be fixed. For example, the specified channel may be specified by a standard or a regulation, or may be specified by a device vendor. The specified channel of the WLAN device <NUM> may alternatively be statically configured. For example, the specified channel may be manually configured as a specified value. The specified channel of the WLAN device <NUM> may alternatively be dynamically negotiated. For example, a plurality of WLAN devices <NUM> in an area negotiate a specified channel shared by the WLAN devices <NUM>.

If the terminal device <NUM> knows the specified channel, step <NUM> may be omitted. Therefore, if the specified channel is fixed or statically configured, step <NUM> is optional. For example, if the specified channel specified by the standard or the regulation is fixed for the terminal device <NUM>, or specified channels are manually configured for both the WLAN device <NUM> and the terminal device <NUM>, step <NUM> may be omitted.

If the specified channel is fixed or statically configured, a channel on which dynamic frequency selection (DFS) does not need to be performed may be selected as the specified channel. For example, in the United States, Canada, Russia, Singapore, China, South Korea, Australia, Brazil, Taiwan, and New Zealand, one of a channel <NUM>, a channel <NUM>, a channel <NUM>, a channel <NUM>, and a channel <NUM> may be used as the specified channel.

If the specified channel of the WLAN device <NUM> is dynamically negotiated, the WLAN device <NUM> may preferably select a channel on which DFS does not need to be performed as the specified channel. For example, priorities of channels selected as specified channels may be configured in the WLAN devices <NUM>, and a priority of a channel on which DFS does not need to be performed is higher than a priority of another channel.

As specified in regulations of some countries/regions, DFS needs to be performed on all channels in the <NUM> band, or all channels in the <NUM> band can be only used indoors. If a WLAN is only used indoors, for example, in an indoor internet of things scenario, the specified channel of the WLAN device <NUM> may be manually configured as an indoor channel. If a WLAN needs to be used outdoors, the WLAN device <NUM> performs DFS and then selects a valid WLAN channel as the specified channel.

If the specified channel of the WLAN device <NUM> is dynamically negotiated, or the specified channel is fixed or statically configured, but the terminal device <NUM> does not know the specified channel, the WLAN device <NUM> needs to notify the terminal device <NUM> of the specified channel. The WLAN device <NUM> sends the information about the specified channel on the operating channel. The information about the specified channel may be carried in a WUR channel element. The WUR channel element is a newly defined information element. A value of an element ID field of the WUR channel element is, for example, one of <NUM> to <NUM> or <NUM> to <NUM>. A length of an information field of the WUR channel element may be an octet, and the information field of the WUR channel element includes a channel number. For example, if the specified channel is the channel <NUM>, a value of the channel number of the WUR channel element is <NUM>. The WUR channel element may be carried in one or more of a beacon frame, a probe response frame, and an action frame (for example, a spectrum management action frame or a WUR action frame).

The specified channel may be the same as or different from the operating channel of the WLAN device <NUM>. For example, if the specified channel is the channel <NUM>, and operating channels of a plurality of WLAN devices are respectively the channel <NUM>, the channel <NUM>, the channel <NUM>, the channel <NUM>, and the channel <NUM>, an operating channel of one of the WLAN devices is the same as the specified channel.

Optionally, to reduce interference between the operating channel and the specified channel, an operating channel available to the WLAN device and the primary radio frequency circuit may be configured as a WLAN channel other than the specified channel. For example, if the specified channel is the channel <NUM>, the operating channel available to the WLAN device and the primary radio frequency circuit may be only a valid operating channel other than the channel <NUM>.

If the specified channel is different from the operating channel of the WLAN device <NUM>, the WLAN device <NUM> switches to the specified channel when being to send a WUR frame, and sends the WUR frame on the specified channel. After sending the WUR frame, the WLAN device <NUM> returns to the operating channel of the WLAN device <NUM>.

The WLAN device <NUM> sends a WUR beacon frame on the specified channel.

The WLAN device <NUM> periodically sends the WUR beacon frame on the specified channel (for example, the channel <NUM>). The WUR beacon frame is different from a beacon frame sent by the WLAN device <NUM> on the operating channel (for example, the channel <NUM>), and the WUR beacon frame and the beacon frame on the operating channel are separately sent. For example, a beacon interval of the WUR beacon frame may be far greater than a beacon interval of the beacon frame. The beacon interval of the WUR beacon frame may be carried in a WUR mode element. The WUR mode element may be carried in one or more of a beacon frame, a probe response frame, and an action frame (for example, a WUR action frame) on the operating channel.

If the WLAN device <NUM> sends the WUR beacon frame on the specified channel, and the WUR radio frequency circuit <NUM> of the terminal device <NUM> is enabled and operates on the specified channel, the terminal device <NUM> receives the WUR beacon frame. The terminal device <NUM> that receives the WUR beacon frame knows existence of the WLAN device <NUM> that sends the WUR beacon frame. Optionally, the WUR beacon frame may include an indication for the operating channel of the WLAN device <NUM>.

The foregoing step <NUM> is optional, and the WLAN device <NUM> may not send the WUR beacon frame on the specified channel. For example, if the primary WUR channel is the operating channel and the secondary WUR channel is the specified channel, the WLAN device <NUM> may only send the WUR beacon frame on the operating channel, and does not send the WUR beacon frame on the specified channel.

When the terminal device <NUM> is in a sleep state, the WUR radio frequency circuit <NUM> of the terminal device <NUM> is enabled. Optionally, when the terminal device <NUM> is in an awake state, the terminal device <NUM> may disconnect the WUR radio frequency circuit <NUM> for further energy saving.

The WLAN device <NUM> may change the specified channel. For example, if the specified channel of the WLAN device <NUM> is dynamically negotiated, the WLAN device <NUM> may change the specified channel. Alternatively, if the specified channel of the WLAN device <NUM> is configured, the specified channel may be changed in a new configuration. To enable the terminal device <NUM> to know a change of the specified channel, the WLAN device <NUM> needs to notify the terminal device <NUM> of a new specified channel. For example, before changing the specified channel, the WLAN device <NUM> indicates a new specified channel by using the WUR beacon frame. The WUR radio frequency circuit <NUM> receives the WUR beacon frame, and if the WUR beacon frame indicates a new specified channel, the WUR radio frequency circuit <NUM> operates on the new specified channel. For another example, if the secondary WUR channel is the specified channel, the WLAN device <NUM> sends a change indication of the specified channel on the specified channel, to indicate a new specified channel. The WUR radio frequency circuit <NUM> that operates on the specified channel receives the change indication of the specified channel, and the WUR radio frequency circuit <NUM> operates on the new specified channel according to the indication. The change indication of the specified channel may be a WUR frame of a new type.

The WLAN device <NUM> sends a wake-up frame on the specified channel.

If the WLAN device <NUM> needs to wake up one or more terminal devices, the WLAN device <NUM> sends the wake-up frame on the specified channel. The wake-up frame in this embodiment of the present invention is a WUR frame, and may also be referred to as a WUR wake-up frame. The wake-up frame includes an identifier of a to-be-woken-up terminal device. The WUR radio frequency circuit <NUM> of the terminal device <NUM> receives the wake-up frame, and may determine, based on the identifier of the to-be-woken-up terminal device, whether the terminal device <NUM> is the to-be-woken-up terminal device. An identifier of the terminal device may be an address of the terminal device, for example, a media access control (MAC) address, or may be an identifier of another type that can identify the terminal device, for example, an association ID (AID) of the terminal device <NUM> and a combination of BSS colors of a basic service set (BSS) associated with the terminal device <NUM>. A BSS color is an identifier for simplifying each BBS by the wireless AP in the area. The identifier of the terminal device may be an identifier of one terminal device, or may be a group identifier or a broadcast identifier. The group identifier indicates that all terminal devices in a corresponding group are to-be-woken-up terminal devices. The broadcast identifier indicates that any terminal device is a to-be-woken-up terminal device.

If the WLAN device <NUM> needs to send a WLAN frame (for example, an individually addressed frame) to one terminal device, the WLAN device <NUM> sends the wake-up frame indicating that the identifier of the to-be-woken-up terminal device is an identifier of one terminal device, to wake up the terminal device.

If the WLAN device <NUM> needs to send a WLAN frame to a plurality of terminal devices, the WLAN frame is a group addressed frame. The WLAN device <NUM> sends the wake-up frame indicating that the identifier of the to-be-woken-up terminal device is a group identifier or a broadcast identifier, to wake up the plurality of terminal devices. The WLAN device <NUM> sends the group addressed frame on the operating channel after a preparation period (after the wake-up frame indicating that the identifier is a group identifier or a broadcast identifier is sent.

The WLAN device <NUM> may modulate a payload of the WUR wake-up frame through on-off keying (OOK). Correspondingly, the WUR radio frequency circuit <NUM> demodulates the payload of the WUR wake-up frame through OOK. The WUR wake-up frame may not occupy full bandwidth of the specified channel, but only uses one or more orthogonal frequency division multiplexing (OFDM) subcarriers thereof.

If the WUR radio frequency circuit <NUM> receives the wake-up frame on the specified channel and the terminal device <NUM> is the to-be-woken-up terminal device, the WUR radio frequency circuit <NUM> wakes up the primary radio frequency circuit <NUM>. For example, if the identifier of the to-be-woken-up terminal device is an identifier of one terminal device, and the identifier of the terminal device is the identifier of the terminal device <NUM>, the WUR radio frequency circuit <NUM> wakes up the primary radio frequency circuit <NUM>. If the identifier of the to-be-woken-up terminal device is a group identifier, and the terminal device <NUM> is in a group identified by the group identifier, the WUR radio frequency circuit <NUM> wakes up the primary radio frequency circuit <NUM>. If the identifier of the to-be-woken-up terminal device is a broadcast identifier, the WUR radio frequency circuit <NUM> wakes up the primary radio frequency circuit <NUM>.

The WUR radio frequency circuit <NUM> may directly wake up the primary radio frequency circuit <NUM>. Alternatively, the WUR radio frequency circuit <NUM> may instruct the processor to wake up the primary radio frequency circuit <NUM>. After being woken up, the primary radio frequency circuit operates on an operating channel available to the primary radio frequency circuit.

Optionally, the wake-up frame may include the indication for the operating channel of the WLAN device <NUM>. The primary radio frequency circuit <NUM> operates on the operating channel according to the indication after being woken up.

The primary radio frequency circuit <NUM> sends a response to the wake-up frame on the operating channel.

If the WLAN device <NUM> sends the wake-up frame indicating that the identifier of the to-be-woken-up terminal device is the identifier of one terminal device <NUM>, to wake up the terminal device <NUM> individually, the WLAN device <NUM> needs to determine whether the terminal device <NUM> has been woken up. Because the WUR radio frequency circuit <NUM> cannot send a radio signal, the WUR radio frequency circuit <NUM> cannot reply with an acknowledgement (ACK) frame on the specified channel. Therefore, the primary radio frequency circuit <NUM> of the terminal device <NUM> sends the response to the wake-up frame on the operating channel after being woken up. The response may be an ACK frame, a probe request frame, a data frame (for example, an empty data frame), or any frame of another type, provided that the WLAN device <NUM> knows that the terminal device <NUM> has been woken up. If the WLAN device <NUM> receives the response to the wake-up frame on the operating channel, the WLAN device <NUM> knows that the terminal device <NUM> has been successfully woken up. If the WLAN device <NUM> does not receive the response to the wake-up frame on the operating channel, it indicates that the WLAN device <NUM> fails to wake up the terminal device <NUM>.

Optionally, if the WLAN device <NUM> does not receive the response to the wake-up frame on the operating channel, the WLAN device <NUM> notifies another WLAN device. The another WLAN device and the WLAN device <NUM> send a new wake-up frame on the specified channel. The new wake-up frame includes the identifier of the terminal device <NUM>. In addition, a new wake-up frame sent by each WLAN device includes an indication for an operating channel of the corresponding WLAN device.

Optionally, if the WLAN device <NUM> does not receive the response to the wake-up frame on the operating channel, the WLAN device <NUM> sends a new wake-up frame on the specified channel. The new wake-up frame may be the same as a previously sent wake-up frame. Alternatively, the new wake-up frame may be different from a previously sent wake-up frame. For example, if the operating channel of the WLAN device <NUM> changes when the WLAN device <NUM> waits for a response to the previously sent wake-up frame, an indication for the operating channel in the new wake-up frame correspondingly changes.

Optionally, if the WLAN device <NUM> fails to wake up the terminal device <NUM> for the first time, the WLAN device <NUM> attempts to wake up the terminal device <NUM> again. If the WLAN device <NUM> fails to wake up the terminal device <NUM> again after one or more attempts, the WLAN device <NUM> instructs another WLAN device to send a wake-up frame.

If the WLAN device <NUM> sends the wake-up frame indicating that the identifier of the to-be-woken-up terminal device is a group identifier or a broadcast identifier, step <NUM> may be omitted.

The WLAN device <NUM> sends a WLAN frame on the operating channel.

If the WLAN device <NUM> wakes up the terminal device <NUM> individually, the WLAN device <NUM> sends the WLAN frame to the terminal device <NUM> on the operating channel after determining that the terminal device <NUM> has been woken up. If the WLAN device <NUM> sends the wake-up frame indicating that the identifier is a group identifier or a broadcast identifier, to wake up a plurality of terminal devices, the WLAN device <NUM> does not need to determine whether each WLAN device <NUM> has been woken up. The WLAN device <NUM> sends the WLAN frame such as a group addressed frame on the operating channel after a preparation period after the wake-up frame is sent.

<FIG> is an example in which a terminal device moves in coverage areas of two WLAN devices according to an embodiment of the present invention. In <FIG>, a terminal device <NUM> is associated with a WLAN device <NUM> and then enters a sleep state. The terminal device <NUM> in the sleep state moves into a coverage area of a WLAN device <NUM> and then is woken up by the WLAN device <NUM>. For example, the WLAN device <NUM> is the WLAN device <NUM> in <FIG>, the WLAN device <NUM> is the WLAN device <NUM> in <FIG>, and the terminal device <NUM> is the terminal device <NUM> in <FIG>. An operation process is as follows:
<NUM>. The WLAN device <NUM> sends information about a specified channel on an operating channel of the WLAN device <NUM>, and after receiving the information about the specified channel, a primary radio frequency circuit of the terminal device <NUM> configures a WUR channel of a WUR radio frequency circuit as a specified channel based on the information.

The operating channel of the WLAN device <NUM> is a channel <NUM>, and the specified channel is a channel <NUM>. The WLAN device <NUM> sends information about the channel <NUM> on the channel <NUM>. After receiving the information about the channel <NUM>, the primary radio frequency circuit of the terminal device <NUM> configures the specified channel of the WUR radio frequency circuit as the channel <NUM>. Then, the terminal device <NUM> enters the sleep state.

The WLAN device <NUM> sends a WUR beacon frame on the specified channel, where the WUR beacon frame indicates a new specified channel.

The WLAN device <NUM> periodically sends the WUR beacon frame on the channel <NUM>. If the WLAN device <NUM> determines that the new specified channel is a channel <NUM>, the WUR beacon frame sent by the WLAN device <NUM> on the channel <NUM> indicates that the channel <NUM> is the new specified channel. The WUR radio frequency circuit of the terminal device <NUM> receives the WUR beacon frame, and configures the new specified channel.

The WLAN device <NUM> sends the WUR beacon frame on the new specified channel.

The WLAN device <NUM> periodically sends the WUR beacon frame on the channel <NUM>. The terminal device <NUM> in the sleep state can receive the WUR beacon frame when being in a coverage area of the WLAN device <NUM>. If leaving the coverage area of the WLAN device <NUM>, the terminal device <NUM> in the sleep state cannot receive the WUR beacon frame.

The WLAN device <NUM> sends a WUR beacon frame on the new specified channel.

The specified channel of the WLAN device <NUM> is the same as that of the WLAN device <NUM>. When the WLAN device <NUM> changes the specified channel to the channel <NUM>, the specified channel of the WLAN device <NUM> is also changed to the channel <NUM>. After the specified channel is changed, the WLAN device <NUM> periodically sends the WUR beacon frame on the channel <NUM>. The terminal device <NUM> in the sleep state can receive the WUR beacon frame after entering the coverage area of the WLAN device <NUM>.

The WLAN device <NUM> sends a wake-up frame on the new specified channel.

When the WLAN device <NUM> needs to wake up the terminal device <NUM>, the WLAN device <NUM> sends, on the channel <NUM>, a wake-up frame that includes an identifier of the terminal device <NUM>. The wake-up frame further includes an indication for an operating channel (a channel <NUM>) of the WLAN device <NUM>. The WUR radio frequency circuit of the terminal device <NUM> receives the wake-up frame.

The primary radio frequency circuit of the terminal device <NUM> sends a response to the wake-up frame on an operating channel.

After receiving the wake-up frame, the WUR radio frequency circuit of the terminal device <NUM> wakes up the primary radio frequency circuit. Because the WUR radio frequency circuit cannot send a radio signal, the WUR radio frequency circuit cannot reply with an acknowledgement frame on the channel <NUM>. Therefore, after being woken up, the primary radio frequency circuit of the terminal device <NUM> sends the response to the wake-up frame on the channel <NUM>.

If the WLAN device <NUM> does not receive the response to the wake-up frame on the channel <NUM>, the WLAN device <NUM> sends a new wake-up frame on the channel <NUM>. The new wake-up frame may be the same as a previously sent wake-up frame. Alternatively, the new wake-up frame may be different from a previously sent wake-up frame.

After determining that the terminal device <NUM> has been woken up, the WLAN device <NUM> sends a WLAN frame to the terminal device <NUM> on a channel <NUM>.

<FIG> is another example in which a terminal device moves in coverage areas of two WLAN devices according to an embodiment of the present invention. In <FIG>, a terminal device <NUM> is associated with a WLAN device <NUM> and then enters a sleep state. The terminal device <NUM> in the sleep state moves into a coverage area of a WLAN device <NUM> and then is woken up by the WLAN device <NUM>. For example, the WLAN device <NUM> is the WLAN device <NUM> in <FIG>, the WLAN device <NUM> is the WLAN device <NUM> in <FIG>, and the terminal device <NUM> is the terminal device <NUM> in <FIG>. An operation process is as follows:
<NUM>. The WLAN device <NUM> sends information about a specified channel on an operating channel of the WLAN device <NUM>, and after receiving the information about the specified channel, a primary radio frequency circuit of the terminal device <NUM> configures a specified channel of a WUR radio frequency circuit based on the information.

The operating channel of the WLAN device <NUM> is a channel <NUM>, and the specified channel is a channel <NUM>. The WLAN device <NUM> sends information about the channel <NUM> on the channel <NUM>. After receiving the information about the channel <NUM>, the primary radio frequency circuit of the terminal device <NUM> configures a secondary WUR channel of the WUR radio frequency circuit as the specified channel (the channel <NUM>). Then, the terminal device <NUM> enters the sleep state.

The WLAN device <NUM> sends a WUR beacon frame on the operating channel.

The WLAN device <NUM> periodically sends the WUR beacon frame on the channel <NUM>. If the WLAN device <NUM> determines a new specified channel, the WUR beacon frame sent by the WLAN device <NUM> on the channel <NUM> indicates the new specified channel. The WUR radio frequency circuit of the terminal device <NUM> receives the WUR beacon frame, and configures the secondary WUR channel as the new specified channel.

The terminal device <NUM> in the sleep state leaves a coverage area of the WLAN device <NUM>, and cannot receive the WUR beacon frame sent by the WLAN device <NUM> on the operating channel.

The terminal device <NUM> in the sleep state can receive the WUR beacon frame when being in the coverage area of the WLAN device <NUM>. If leaving the coverage area of the WLAN device <NUM>, the terminal device <NUM> in the sleep state cannot receive the WUR beacon frame on the channel <NUM>.

The WLAN device <NUM> sends a WUR beacon frame on an operating channel.

The operating channel of the WLAN device <NUM> is a channel <NUM>. The terminal device <NUM> in the sleep state cannot know an operating channel of a WLAN device falling in a coverage area of the terminal device <NUM>. The WUR radio frequency circuit of the terminal device <NUM> in the sleep state still operates on the channel <NUM>, and therefore cannot receive the WUR beacon frame on the channel <NUM>. If the terminal device <NUM> still fails to listen and obtain the WUR beacon frame after one or more beacon intervals of the WUR beacon frame, the WUR radio frequency circuit operates on the secondary WUR channel, namely, the channel <NUM>.

The WLAN device <NUM> sends a wake-up frame on the operating channel.

When the WLAN device <NUM> needs to wake up the terminal device <NUM>, the WLAN device <NUM> sends, on the channel <NUM>, a wake-up frame that includes an identifier of the terminal device <NUM>. Because the terminal device <NUM> leaves the coverage area of the WLAN device <NUM>, and the WUR radio frequency circuit of the terminal device <NUM> operates on the secondary WUR channel, namely, the channel <NUM>, the terminal device <NUM> cannot receive the wake-up frame from the WLAN device <NUM>.

The WLAN device <NUM> instructs each WLAN device to send a wake-up frame on a specified channel.

Because the terminal device <NUM> is not woken up, and therefore does not respond to the wake-up frame, the WLAN device <NUM> receives no response to the wake-up frame on the channel <NUM>. Optionally, the WLAN device <NUM> may send a new wake-up frame on the channel <NUM>. If the WLAN device <NUM> fails to send the wake-up frame for the first time, or fails to resend the wake-up frame, the WLAN device <NUM> instructs each WLAN device (including the WLAN device <NUM>) to send, on the specified channel (the channel <NUM>), the wake-up frame that includes the identifier of the terminal device <NUM>. In addition, each wake-up frame includes an indication for an operating channel of a corresponding WLAN device. The WUR radio frequency circuit of the terminal device <NUM> operates on the secondary WUR channel, namely, the channel <NUM>. Therefore, the terminal device <NUM> receives the wake-up frame from the WLAN device <NUM>. The wake-up frame from the WLAN device <NUM> includes an indication for the operating channel (the channel <NUM>) of the WLAN device <NUM>.

The primary radio frequency circuit of the terminal device <NUM> sends a response to the wake-up frame on an operating channel (a channel <NUM>) indicated by the wake-up frame.

After determining that the terminal device <NUM> has been woken up, the WLAN device <NUM> sends a WLAN frame to the terminal device <NUM> on the channel <NUM>.

<FIG> is a schematic diagram of an apparatus for waking up a terminal device according to an embodiment of the present invention. The apparatus for waking up a terminal device is implemented by any WLAN device in <FIG>. The apparatus for waking up a terminal device includes a wake-up module <NUM> and a sending module <NUM>. The wake-up module is configured to send a wake-up frame on a specified channel, and the wake-up frame includes an identifier of a to-be-woken-up terminal device. The sending module is configured to send a WLAN frame on an operating channel. For details about the apparatus for waking up a terminal device, refer to the content of the foregoing embodiments shown in <FIG>. All or some of the foregoing embodiments may be implemented by using software, hardware, or a combination thereof. When the software or the combination of software and hardware is used to implement the embodiments, all or some of the embodiments may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the procedures or functions according to the embodiments of the present invention are all or partially generated. The computer may be a general-purpose computer, a dedicated computer, a computer network, or another programmable apparatus. The computer instructions may be stored in a storage medium or may be transmitted from one storage medium to another storage medium. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, a twisted pair, or an optical fiber) or wireless (for example, infrared, radio, or microwave) manner. The storage medium may be any usable medium accessible by a computer, or a data storage device, such as a server or a data center, integrating one or more media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, an optical disc), a semiconductor medium (for example, a solid-state drive (SSD)), or the like.

Claim 1:
A terminal device, comprising a primary radio frequency circuit (<NUM>) and a wake-up radio, WUR, radio frequency circuit (<NUM>), wherein
the WUR radio frequency circuit (<NUM>) is configured to: only receive a radio signal, operate on a specified channel, and if the WUR radio frequency circuit receives a wake-up frame on the specified channel and the terminal device is a to-be-woken-up terminal device, wake up the primary radio frequency circuit, wherein the wake-up frame comprises an identifier of the to-be-woken-up terminal device;
the primary radio frequency circuit (<NUM>) is configured to operate on an operating channel of the primary radio frequency circuit after being woken up;
wherein the primary radio frequency circuit is further configured to receive information about the specified channel of the WUR radio frequency circuit on the operating channel of the primary radio frequency circuit; and
wherein the wake-up frame further comprises an indication for the operating channel, and the primary radio frequency circuit is configured to: after being woken up, operate on the operating channel indicated by the wake-up frame.