WO2017186059A1

WO2017186059A1 - Method and apparatus for switching access point in wireless local area network

Info

Publication number: WO2017186059A1
Application number: PCT/CN2017/081435
Authority: WO
Inventors: 叶苏昌; 季标; 王云贵; 张�林
Original assignee: 华为技术有限公司
Priority date: 2016-04-29
Filing date: 2017-04-21
Publication date: 2017-11-02
Also published as: CN107333307A; CN107333307B

Abstract

Disclosed are a method and an apparatus for switching an access point (AP) in a wireless local area network, so as to enable a STA in power save mode to perform AP switching. The method comprises: a first AP determining that a STA connected to the first AP is in power save mode, wherein the first AP provides, based on a BSSID corresponding to the STA, a service to the STA, the BSSID corresponding to the STA being different from BSSIDs corresponding to any other STAs in the same ESS as the STA; the first AP determining a second AP in the same ESS to be a target AP connected after the STA is switched; the first AP sending a wake-up frame to the STA, wherein the wake-up frame is used to instruct the STA to be in a non-sleep state when the second AP sends a beacon frame based on the BSSID corresponding to the STA; and the first AP sending a switching instruction to the second AP, wherein the switching instruction is used to instruct the second AP to provide, based on the BSSID corresponding to the STA, a service for the STA.

Description

Method and device for switching access points in wireless local area network

This application claims the priority of the Chinese patent application filed on April 29, 2016, the Chinese Patent Office, the application number is 201610289641.2, and the invention is entitled "Method and Apparatus for Switching Access Points in a Wireless Local Area Network", the entire contents of which are The citations are incorporated herein by reference.

Technical field

The present application relates to the field of communications technologies, and in particular, to a method and device for switching an access point AP in a wireless local area network (WLAN).

Background technique

In a wireless local area network (WLAN) system, a terminal needs to be connected to an access point (AP), and data is transmitted and received through the AP. During communication, the signal between the terminal and the currently connected AP may be degraded. For example, when the distance between the terminal and the currently connected first AP becomes longer, the signal between them becomes worse. When the signal quality between the terminal and the currently connected first AP is lower than the threshold, the terminal initiates an association request to the second AP with better signal, and switches from connecting with the first AP to connecting with the second AP. It can be called roaming of the terminal.

The terminal usually enters the power save mode when there is no data to send and receive. After entering the power save mode, the terminal only periodically turns on the RF module to send and receive data. The terminal cannot initiate roaming actively during the shutdown of the radio module of the terminal. When the terminal opens the radio module, the link between the terminal and the original AP may be degraded to be unable to communicate normally. The terminal can only re-associate with the AP in the WLAN, which not only delays the communication needs of the terminal, but also connects to the original AP. When there is data cached for the terminal, the STA will also be unable to receive the data, resulting in data loss.

Summary of the invention

The present invention provides a method and a device for switching an access point in a wireless local area network, so that the terminal in the power saving mode can successfully perform AP switching.

In a first aspect, the present application provides a method for switching an AP in a WLAN. In the WLAN system applied by the method, each STA in an extended service set (ESS) is assigned a basic service set identifier ( English: basic service set identifier (BSSID), and different STAs in the same ESS are assigned different BSSIDs. The AP in the ESS provides services for the STA based on the BSSID assigned to the STA. After determining that the STA connected to the STA is in the power saving mode and the STA in the power saving mode needs to switch to the second AP in the same ESS, the first AP sends a wakeup frame to the STA, indicating that the STA is in the second. The AP is in an awake state when transmitting a beacon frame based on the BSSID assigned to the STA. On the other hand, the first AP sends a handover instruction to the second AP, instructing the second AP to provide the STA with the BSSID allocated for the STA. After the first AP sends the wake-up frame to the STA and sends the handover instruction to the second AP, the first AP stops serving the STA.

The process of the AP connected to the STA is performed by the AP. Therefore, even if the STA is in the power-saving mode and the radio module is disabled, the AP can perform the AP handover normally. The communication can be performed through the AP in the ESS, and the STA has good communication quality because the STA can switch the AP with the better connection signal.

In an optional implementation, after determining that the STA is in the power saving mode and the STA needs to be connected to the second AP, the first AP first determines its own beacon frame transmission time and the beacon frame of the second AP. Whether the sending time is synchronized, if the two are synchronized, the first AP may save the step of sending a wake-up frame to the STA, and directly send a switching instruction to the second AP. When the beacon frame transmission time of the first AP is not synchronized with the beacon frame transmission time of the second AP, the first AP sends a wakeup frame to the STA, and sends a handover instruction to the second AP to ensure that the STA is in the The second AP is in an awake state when transmitting the beacon frame based on the BSSID allocated to the STA, so that the STA can receive the beacon frame transmitted by the second AP. The present implementation can reduce the transmission of the wake-up frame when the first AP and the second AP transmit the beacon frame, save the transmission resources, and reduce the time-consuming of the AP handover.

In an optional implementation, the wake-up frame includes a first beacon frame, where the first beacon frame includes an indication that the STA adjusts the wake-up time to the second AP, based on the BSSID allocated for the STA, to send the beacon frame. The field of time. For example, the timestamp field included in the first beacon frame is used to indicate that the STA synchronizes the local time with the time of the second AP, such that the wakeup time of the STA is synchronized with the beacon frame transmission time of the second AP, so that the The STA can receive a beacon frame transmitted by the second AP to the STA based on the BSSID assigned to the STA.

In an optional implementation, the first AP sends a wake-up frame to the STA, including a field for indicating that the STA adjusts the wake-up time to a time when the second AP transmits a beacon frame based on the BSSID allocated for the STA, Determining, by the first AP, the second AP to receive the second AP, before determining the time interval between the beacon frame sending time of the first AP and the beacon frame sending time of the second AP. a time of the second beacon frame; the first AP determines a beacon frame transmission time of the first AP and a beacon frame of the second AP according to the time of the beacon frame transmission of the first AP and the time of receiving the second beacon frame The time interval before the send time. After determining the time interval, the first AP determines the field for updating the STA wake-up time according to the time interval.

In an optional implementation, the wake-up frame includes a third beacon frame including a field indicating that the STA remains awake. The STA is in the awake state may be that the STA is in the active mode, or the STA is in the power saving mode and enters (for example, enters according to the listening interval) the awake state. The STA in the awake state turns on its RF module. For example, the transmit traffic indication message (DTIM) field in the third beacon frame is set to 1. In some embodiments, the AP and the STA agree that the STA receives the beacon frame with the DTIM field set to 1. , switch from power saving mode to active mode. In other embodiments, the AP and the STA agree that after receiving the beacon frame with the DTIM field set to 1, the STA continues to be in the power saving mode but remains in the awake state.

In an optional implementation, the STA receives the third beacon frame, and the DTIM field is set to 1 in the third beacon frame, the STA sends an election (English: poll) frame to the first AP, and the first AP receives the poll frame. However, if the data is not sent to the STA, the STA will remain awake until it receives the data or beacon frame transmitted by the connected AP.

In an optional implementation, after the first AP sends a third beacon frame indicating that the STA is in the awake state, the first AP sends one or more data frames to the STA, and the data frame may not include the transmission. Empty (English: null) data frame for data. For example, when the STA is in the awake state in the power saving mode, the first AP receives the poll frame sent by the STA, and sends one or more data frames to the STA, and the “More Data” field of each data frame is set to 1. After receiving the data frame, the STA keeps waking up and sends a poll frame to the first AP again. For another example, when the STA is in the active mode, the first AP sends a data frame to the STA, and after receiving the data frame, the STA will re-enter the countdown to the power saving mode, so that the STA can remain in the active mode.

In an optional implementation, after the first AP sends a beacon frame indicating that the STA is in the awake state, the multiple data frames sent to the STA that cause the STA to maintain the awake state may include a null data frame. Even if the first AP does not buffer the data frame of the STA, the first AP may send a null data frame to the STA, and the “More Data” field of the null data frame is set to 1, indicating that the first AP caches the data frame of the STA to deceive. The STA keeps it awake.

In an optional implementation, after confirming that the STA is successfully connected to the STA, the second AP sends a handover success message to the first AP, and after receiving the handover success message, the first AP stops sending the wake-up frame for the STA.

In a second aspect, the present application provides a device for switching an AP in a WLAN, the device being used to perform the method in any of the foregoing first aspect or any possible implementation of the first aspect. In particular, the apparatus comprises means for performing the method of any of the above-described first aspect or any of the possible implementations of the first aspect.

In a third aspect, the application provides a device for switching an AP in a WLAN, the device being used to perform the method in any of the foregoing first aspect or any possible implementation of the first aspect. Specifically, the device includes a processor and a transceiver coupled to the transceiver. The transceiver is for communicating with other network elements in the WLAN for performing the method of any of the above first aspects or any of the possible implementations of the first aspect by a transceiver.

In a fourth aspect, the present application provides a computer readable medium for storing a computer program comprising instructions for performing the method of the first aspect or any possible implementation of the first aspect.

Further on the basis of the implementations provided by the above aspects, the invention may be further combined to provide further implementation.

DRAWINGS

In order to more clearly illustrate the technical solutions in the present application, the drawings used in the description of the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the present invention. For ordinary technicians, other drawings can be obtained based on these drawings without paying for creative labor.

1 is a schematic diagram of a possible implementation manner of a communication system according to an embodiment of the present invention;

2 is a schematic flowchart of a method for switching an AP according to an embodiment of the present invention;

FIG. 3 is another schematic flowchart of a method for switching an AP according to an embodiment of the present disclosure;

4 is a schematic structural diagram of an apparatus for switching an AP in a WLAN according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of an apparatus for switching an AP in another WLAN according to an embodiment of the present invention.

detailed description

The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Specific features of the embodiments of the present invention and the embodiments are the detailed description of the technical solutions of the present invention, and are not intended to limit the technical solutions of the present invention. The technical features of the embodiments of the present invention and the embodiments may be combined with each other without conflict.

In WLAN communication, the STA needs to be connected to an AP, and the connected AP is responsible for data forwarding for the STA. When the signal between the STA and the currently connected AP is poor, the STA needs to switch to the AP with better signal to ensure the normal data communication of the STA. Generally, the STA initiates roaming after detecting that the link between the AP and the AP is degraded to a certain extent, and performs AP handover.

However, after the STA enters the power saving mode, the STA turns off the radio frequency module, and only periodically turns on the radio frequency module to send and receive data. During the shutdown of the STA's RF module, the STA cannot initiate roaming. And the radio mode is turned on in the STA. In the case of a block, the link between the STA and the original connected AP may be degraded to be unable to communicate normally. The STA can only re-associate with the AP in the WLAN, which not only delays the communication requirement of the STA, but also caches data for the STA in the original connected AP. When the STA is also unable to receive the data, the data is lost.

In order to solve the problem that the STA in the power saving mode is difficult to perform the AP handover, the embodiment of the present invention provides an AP handover method. When the STA is in the power saving mode, the AP is responsible for performing the handover of the AP connected by the STA, so that even in the When the STA closes the radio module, the handover of the AP connected to the STA can still be completed.

In the embodiment of the present invention, when the STA first associates an AP in an extended service set (ESS), the STA is assigned a basic service set identifier (BSSID), ESS. Any AP connected to the STA is serving the STA based on the BSSID. That is, the AP in the ESS simulates an AP that has the BSSID assigned to the STA as the BSSID, and transmits and receives the frame of the STA. That is to say, when the AP in the ESS communicates with the STA, the BSSID is the radio (radio) medium access control (MAC) address of the AP. Since the different APs provide services for the STAs based on the same BSSID, the STA does not perceive the AP handover after the APs that connect the STAs are switched. On the other hand, any two STAs in the ESS are assigned different BSSIDs, which can prevent the message forwarding confusion after the STA switches in the ESS.

The allocation manner of the BSSID corresponding to the STA includes multiple implementation manners. For example, after the STA initiates an association request to the AP in the ESS, the AP that receives the STA association request allocates a BSSID to the STA, and informs the other APs in the ESS to connect the STA to other APs in the ESS. The AP connected to the STA can provide services for the STA based on the BSSID assigned to the STA. For another example, in the communication system shown in FIG. 1, after the STA initiates an association request to the AP in the ESS, the roaming controller in the WLAN allocates a BSSID to the STA, and notifies the AP in the ESS to be based on the BSSID allocated for the STA. Serve the STA.

In the embodiment of the present invention, when the WLAN includes the foregoing roaming controller, the roaming controller may have multiple implementation manners, for example, the roaming controller may be used as a control and configuration of the wireless access point (English: Control And Provisioning of Wireless Access Points) Access Controller (AC) in the CAPWAP protocol. Correspondingly, the AP can be used as the wireless termination point (WTP) in the CAPWAP protocol. In addition, the roaming controller can be implemented by a single device or by a cluster of multiple distributed devices.

In the embodiment of the present invention, after the STA reaches the roaming threshold, the AP connected to the STA switches the STA to another AP in the same ESS, and the AP connected to the STA after the connected AP is switched in the embodiment of the present invention. Referred to as the target AP, the target AP is instructed to provide services for the STA based on the BSSID assigned to the STA.

The AP connected to the STA can determine whether the STA reaches the roaming threshold, and the roaming controller shown in FIG. 1 can determine whether the STA reaches the roaming threshold. Specifically, the AP connected to the STA monitors the signal indicator of the STA, for example, received signal strength indication (RSSI), packet loss rate, and the like. When the monitored value of the STA's signal indicator is degraded to a preset value, the STA can determine that the STA reaches the roaming threshold. When the roaming controller determines whether the STA reaches the roaming threshold, the AP connected to the STA needs to send the monitoring value of the signal indicator of the STA to the roaming controller.

The target AP that the STA needs to connect to may be determined by: the AP that is not connected to the STA in the same ESS monitors the signal indicator of the STA, and the AP or the roaming controller connected to the STA is based on the AP pair that is not connected to the STA. The monitored value of the signal indicator of the STA determines the target AP from the APs that are not connected to the STA. For example, an AP that is not connected to the STA in the same ESS sends a monitoring value of the signal indicator of the STA to the AP connected to the STA. Or a roaming controller, the AP or the roaming controller connected to the STA determines the AP with the best signal indicator detected as the target AP.

Generally, after the STA sends a packet to the connected AP, the physical layer of other APs that are not connected to the STA can receive the packet, calculate the signal indicator such as RSSI, and then media access control of the AP. The media access control (MAC) layer determines whether the message is sent to itself. If the message is not sent to itself, the message is discarded. However, in the embodiment of the present invention, after determining that the packet is not sent to itself, the MAC layer still stores the RSSI and other signal indicators of the packet into the memory, so that the AP can obtain the signal indicator of the STA that is not connected to itself. . The AP can also monitor the signal indicator of the STA that is not connected to itself by using other technical means in the prior art, which is not detailed in the embodiment of the present invention.

Usually, the time when different APs send beacon frames is not synchronized. For example, different APs have different beacon intervals. For example, one AP transmits a beacon frame at 0 milliseconds (ms), 100 ms, 200 ms... and another AP transmits a beacon frame at 0 ms, 110 ms, 220 ms. Or, although the beacon intervals of different APs are the same, the phases of the transmitted beacon frames are different. For example, one AP transmits a beacon frame at 0 ms, 100 ms, 200 ms... and another AP transmits a beacon frame at 30 ms, 130 ms, 230 ms... When the STA is in the active mode, the STA is always in the awake state, and the STA can receive the beacon frame sent by the second AP after the handover, and send the beacon frame according to the second AP. The field included in the synchronization time includes the time of synchronizing with the time of the second AP.

When the STA is in the power saving mode, the STA is in a doze state (English: doze state), and only enters the awake state according to the listening interval (English: listen interval) to receive the selected beacon frame. The listening interval is typically an integer multiple of the beacon interval. Therefore, the STA only opens the radio frequency module to receive the beacon frame at the time when the first AP before the handover transmits the beacon frame. However, since the time when the first AP and the second AP send the beacon frame is usually not synchronized, the STA in the power saving mode enters the awake state for a short period of time, and the beacon frame sent by the second AP may not be received, resulting in the STA. The local time of the switched second AP cannot be synchronized according to the beacon frame sent by the second AP. In this way, although the second AP has succeeded in providing the STA for the STA, the STA cannot receive the beacon frame sent by the second AP, and cannot synchronize the local time with the time of the second AP, thereby failing to pass the second AP. Data transmission and reception.

In order to solve the problem, an embodiment of the present invention provides a method for switching an AP in a WLAN, and an AP, where the first AP before the handover sends a wake-up frame to the STA, so that the STA sends the beacon frame to the second AP after the handover. The STA can be in an awake state, so that the STA can receive the beacon frame sent by the second AP, and synchronize the local time with the time of the second AP according to the beacon frame sent by the second AP.

With reference to FIG. 2, the method for switching the AP according to the embodiment of the present invention is described in detail below by using the first AP to switch the first STA connected to the first AP to the second AP. The method for switching the AP includes the following steps:

Step 101: The first AP determines that the first STA connected to the first AP is in the power saving mode, and determines that the second AP in the ESS where the first AP is located is the target AP that the first STA needs to connect.

Specifically, the first AP is connected to the first STA, where the first STA is connected to the WLAN through the first AP, and the first AP provides the service to the first STA. For example, the first AP forwards data for the first STA. For another example, when the first STA enters the power saving mode, the first STA caches data for the first STA.

The first STA may be any STA connected to the first STA. When entering the power saving mode, the first STA sends a record of the first STA entering the power saving mode to the connected first AP, where the first AP is locally saved. The record can determine that the first STA enters the power save mode.

In step 101, the first AP may learn the first AP roaming threshold according to the manner described above, and learn that the second AP in the same ESS is the target AP that the first AP needs to connect, and the embodiment of the present invention does not repeat here.

Step 102: The first AP sends a wake-up frame to the first STA, where the wake-up frame is used to indicate that the first STA is in an awake state when the second AP sends a beacon frame to the first STA based on the first BSSID allocated for the first STA.

The STA is in the awake state may be that the STA is in the active mode, or the STA is in the power saving mode and enters (for example, enters according to the listening interval) the awake state. The STA in the awake state turns on its RF module.

The wake-up frame in step 102 can have multiple implementations, including but not limited to any of the following implementations:

In the first mode, the wake-up frame is a beacon frame, and the beacon frame includes a field for updating the first STA wake-up time, and the field for updating the first STA wake-up time is used to instruct the first STA to adjust the wake-up time to the second. The time at which the AP transmits the beacon frame based on the first BSSID.

Generally, the first AP sends a beacon frame to the first STA based on the first BSSID, and includes a field for instructing the first STA to synchronize the awake time with the time at which the first AP sends the beacon frame. However, in the embodiment of the present invention, in order to ensure that the first STA can receive the beacon frame sent by the second AP, the first AP may use the one of the beacon frames sent to the first STA to update the first STA wakeup time. The value of the field, the modified field is used to indicate that the first STA synchronizes the awake time with the time at which the second AP sends the beacon frame, and this includes instructing the first STA to adjust the awake time to the second AP based on the first BSSID. The beacon frame of the field of the time at which the beacon frame is transmitted can be used as the wake-up frame in the embodiment of the present invention.

The first AP determines the difference between the sending time of the beacon frame and the sending time of the beacon frame of the second AP, to determine that the indication indicates that the first STA adjusts the awake time to the second AP based on the first BSSID. The field of the time at which the beacon frame was sent. The first AP may receive the beacon frame sent by the second AP, and the beacon frame may be a traditional beacon frame, that is, the second AP sends the BSSID based on the second AP itself. Beacon frame. The first AP determines the local time of the first AP when receiving the beacon frame of the second AP, and calculates a time difference between the time when the next beacon frame is transmitted and the time when the second AP beacon frame is received (T_offset) And determining, according to the time difference, the value of the field for updating the wakeup time of the first STA. If the period in which the second AP transmits the beacon frame is different from the period in which the first AP transmits the beacon frame, the difference between the periods in which the two APs transmit the beacon frame may also be considered when calculating the time difference. Optionally, calculating the time difference may further consider a delay between a time when the first AP receives the beacon frame sent by the second AP and a time when the second AP actually sends the beacon frame.

For example, the timestamp field in the beacon frame is the field for updating the STA wakeup time, and the timestamp field is used to synchronize the local time of the STA with the time of the AP. If the first STA does not need to perform AP handover, the value of the timestamp field of the beacon frame sent by the first AP to the first STA at time T1 is A; and in the case where the first STA needs to be switched to the second AP, The value of the timestamp field of the beacon frame sent by the first AP to the first STA at time T1 is adjusted to (A-T_offset), so that the first STA performs time synchronization according to (A-T_offset), although The time of a STA is not synchronized with the time of the first AP, but the next wake-up time of the first STA can be synchronized with the time when the second AP sends the beacon frame.

For another example, the field used to update the STA wakeup time in the beacon frame may also be a beacon interval or a listening interval field. The beacon interval field is an interval at which the AP sends a beacon frame, and the intercept interval field is an integer multiple of the beacon interval field, indicating an interval at which the STA receives the beacon frame. If the first STA does not need to perform the AP handover, the value of the beacon interval field in the beacon frame sent by the first AP to the first STA at time T1 is B, and the value of the interception interval field is k*B, where k is a positive integer. And in the case that the first STA needs to be switched to the second AP, the first AP is at time T1 The value of the beacon interval field of the beacon frame transmitted to the first STA is (BD), and the value of the interception interval field is k*(BD), where k*D=T_offset, such that the first STA is based on the interception The interval l field enters the next wake-up time after k*(BD) duration, which is exactly the time when the second AP transmits the beacon frame.

After the first AP determines to switch the first STA to the second AP, the first AP sends a beacon frame to the first STA, where the field for updating the first STA wakeup time in the beacon frame points to the second AP. The time at which the beacon frame is sent, not the time at which the first AP sends the beacon frame. In this way, after receiving the beacon frame, the first STA adjusts the subsequent wake-up time to a time synchronized with the second AP transmitting the beacon frame, so that the first STA can receive the beacon frame sent by the second AP.

It should be noted that the wake-up time of the first STA in the mode 1 is synchronized with the beacon frame sending time of the second AP, and the set of the wake-up time of the first STA is the sub-beacon frame transmission time set of the second AP. Set, two sets can be equal, but not necessarily equal.

Mode 2, the wake-up frame includes a beacon frame, the beacon frame including a field indicating that the first STA remains awake in the power saving mode.

Generally, the first STA in the power saving mode enters the awake state from the doze state, receives the beacon frame sent by the connected first AP, and if the beacon frame does not include a field that keeps the first STA awake, the first The STA switches back from the awake state to the doze state. If the beacon frame includes the field that causes the first STA to remain awake, the first STA remains awake after receiving the beacon frame.

For example, the field in the beacon frame that wakes up the first STA may be a delivery traffic indication message (DTIM) field.

Generally, the first AP may notify the first STA that the first STA is located in the DTIM field of the beacon frame sent to the first STA after the data frame or the management frame is cached for the first STA. The buffer unit (English: bufferable unit, BU) needs to be obtained. The first STA in the power saving mode turns on the radio frequency module during the waking time, receives the beacon frame, and maintains the awake state according to the DTIM field in the beacon frame. And sending a polling frame to the first AP, after receiving the poll frame, the first AP sends the data packet buffered by the first STA to the first STA.

In the embodiment of the present invention, when the first STA in the power saving mode needs to be switched to the second AP, the first AP is still in the first STA even if the first AP does not cache the data frame or the management frame for the first STA. Adding a field in the transmitted beacon frame that keeps the first STA awake state (for example, a DTIM field that sets the number of bits corresponding to the first STA), so that the first AP remains awake, thereby enabling it to receive the second The beacon frame sent by the AP.

Optionally, after receiving the third beacon frame sent by the first AP, the first STA sends a poll frame to the first AP, and after receiving the poll frame, the first AP does not send the cacheable unit BU to the first STA. . The first STA will remain awake until the first STA receives the cacheable unit for the poll frame transmission until the first AP receives the cacheable unit sent by the first frame or the first STA. The arrival of the frame transmission time.

The mode 3 is different from the foregoing mode 2 in that the beacon frame sent by the first AP to the first STA includes a field indicating that the first STA switches from the power saving mode to the active mode.

During specific implementation, there are two cases between mode 2 and mode 3:

In the case 2, the beacon frame sent by the first AP to the first STA in the mode 2 includes a field A, where the field A is used to indicate that the first STA remains awake; and in the mode 3, the first AP sends the message to the first STA. A field B is included in the beacon frame, and the field B is used to instruct the first STA to switch from the power saving mode to the active mode. Among them, field A and field B are two different fields.

In the scenario 2, the beacon frame sent by the first AP to the first STA includes the field A. In the application scenario where the mode 2 is located, the first AP is agreed with the first STA, and the field A is used to indicate the first The STA remains awake. Mode 3 The beacon frame sent by the AP to the first STA also includes the field A. However, in the application scenario where the mode 3 is located, the first AP is in agreement with the first STA, and the field A is used to indicate that the first STA is in the power saving mode. Switch to active mode. For example, in a possible implementation manner, after receiving the beacon frame of the DTMI position 1, the first STA does not exit the power saving mode and remains awake; and in another possible implementation, the first STA receives After the beacon frame of the DTMI bit is set, the record of the power-saving mode is sent to the connected AP, and the power-saving mode is exited, and the active mode is entered.

It should be noted that, regardless of whether the first STA maintains the awake state in the mode 2 without exiting the power saving mode, or the first STA switches from the power saving mode to the active mode in the mode 3, the radio module of the first STA All are in working state, and can receive the beacon frame sent by the second AP based on the first BSSID.

Mode 4, in combination with mode 2, after the first AP sends a beacon frame indicating that the first STA remains awake to the first STA, sending, by the first STA, at least one data frame, where the data frame includes indicating that the first STA continues A field that remains awake.

In the embodiment of the present invention, the so-called data frame may be a data frame containing transmission data, or may be an empty data frame not including transmission data.

Specifically, after receiving the third beacon frame sent by the first AP, the first STA sends a poll frame to the first AP, and after receiving the poll frame, the first AP sends at least one data frame to the first STA (including the null In the case of a data frame, wherein the "More Data" field of each of the at least one data frame is set to 1, indicating that the first STA continues to remain awake and continues to send a poll frame to the first AP, while the first AP continues The "More Data" field is set to 1 in the data frame sent to the first STA. In this way, the first STA will remain awake until the first AP does not set the "More Data" field in the data frame sent to the first STA.

Mode 5: In combination with mode 3, the first AP sends at least one data frame to the first STA after transmitting, to the first STA, a beacon frame indicating that the first STA switches from the power saving mode to the active mode.

After the first STA is switched from the power saving mode to the active mode, the first STA may be maintained in the active mode for a period of time, which may be determined by the first STA, the first AP, or both. If the duration of the keep-alive mode is short, the first STA may switch from the active mode to the power-saving mode before the beacon frame transmission time of the second AP arrives, causing the first STA to fail to receive the second AP based on the first BSSID. The beacon frame sent.

In order to solve the problem, in the embodiment of the present invention, after the first AP sends a beacon frame for instructing the first STA to switch from the power saving mode to the active mode, the first AP also sends one to the first STA or Multiple data frames (including the case of empty data frames). After receiving each data frame, the first STA will remain in the active mode for a period of time, so if the data frame is not transmitted continuously, the first STA will remain in the active mode.

For example, it is assumed that the power saving policy of the first STA is set to: when the first STA does not perform data transmission and reception for more than the duration S in the active mode, the active mode is switched from the active mode to the power saving mode. The first STA receives, at time T1, a beacon frame that is sent by the first AP and includes a field for indicating that the first STA switches from the power saving mode to the active mode, and switches from the power saving mode to the active mode, if the first STA does not When data is transmitted or received, the power saving mode is entered again at (T1+S). In order to avoid the occurrence of the situation, in the embodiment of the present invention, the first AP sends a null data frame to the first STA at the time (T1+Sm) before the (T1+S) time, and the first STA receives the null data. After the frame, the active mode will remain in the (T1+Sm) to (T1+2S-m) time period. By analogy, before the end of the activation mode of the first STA, the first AP sends a null data frame (which may also be a data frame containing the transmission data) to the first STA again, so that the first STA continues to remain in the active mode.

In the foregoing manners 4 and 5, the first AP, by sending the third beacon frame to the first STA, sends a plurality of data frames to the first STA, so that the first STA maintains the awake state, thereby enabling the first STA to enable the first STA. Receiving a beacon frame sent by the second AP.

It should be noted that, in the case of no conflict, any two or more of the above manners 1 to 5 may be used in combination, for example, the first AP sends both the first STA and the second AP to the second AP. The time-synchronized beacon frame, in turn, sends a plurality of empty data frames to the first STA, and the "More Data" field in the empty data frames is set to 1, indicating that the first STA remains awake.

In addition, the wakeup time of the first STA in the foregoing manner 1 is synchronized with the beacon frame transmission time of the second AP, and the set of the wakeup time of the first STA is a subset of the beacon frame transmission time set of the second AP. The two sets can be equal, but not necessarily equal.

Step 103: The first AP sends a handover instruction to the second AP, where the handover instruction is used to instruct the second AP to provide a service for the first STA based on the first BSSID.

Specifically, the handover instruction includes an identifier of the first STA, and is used to indicate that the second AP provides a service for the first STA. Optionally, if the first AP or the roaming controller does not immediately notify the second AP of the mapping between the first STA and the first BSSID after allocating the first BSSID to the first STA, the first AP sends the second AP to the second AP. The handover instruction may further include a first BSSID allocated for the first STA, to enable the second AP to provide service for the first STA based on the first BSSID.

Step 104: The first STA receives the wake-up frame, and maintains the awake state at the beacon frame sending time of the second AP.

The specific implementation manner in which the second AP keeps the awake state in the beacon frame sending time of the second AP according to the awake frame is described in step 102, and is not repeated here. In addition, in step 104, the first STA maintains the awake state in the beacon frame transmission time of the second AP, which means that the first STA remains awake at any (or any number of) beacon frame transmission times of the second AP. status.

Step 105: The second AP receives the handover instruction, and provides a service for the first STA based on the first BSSID allocated for the first STA.

Specifically, after receiving the handover instruction, the second AP is responsible for providing services for the first STA. The so-called providing service includes: the second AP sending a beacon frame to the first STA based on the first BSSID, so that the first STA maintains a link with the second AP according to the beacon frame.

The second AP obtains the mapping between the first STA and the first BSSID, and may be implemented as follows: after the first BSSID is allocated to the first STA, the roaming controller sends the mapping between the first STA and the first BSSID to the ESS. Each AP, the second AP, in turn, can learn the first BSSID assigned by the roaming controller to the first STA. Alternatively, after receiving the handover instruction sent by the first AP, the second AP requests the roaming controller to send the BSSID corresponding to the first STA to the second AP, and the second AP can further learn the first BSSID. Or, when the first AP sends the handover instruction to the second AP, the first AP sends the first BSSID corresponding to the first STA to the second AP.

Step 106: The first AP stops providing services for the first STA.

Specifically, the first AP stops serving the first STA, and the first AP does not use the first STA as the STA that needs to provide the normal WLAN service, for example, the first STA is no longer sent based on the BSSID. Frame, forward data, cache data, and more.

In combination with any one of the foregoing manners 2 to 5, the first AP may continue to send a wake-up frame to the first STA after the step 102 and the step 103 are performed, indicating the first STA. The beacon frame transmission time of the second AP remains awake. In the behavior that the first AP sends a wake-up frame to the first STA, the first AP The normal WLAN service is not provided to the first STA. Therefore, the first AP stops serving the first STA in step 106, and the first AP continues to send the wake-up frame to the first STA after performing step 102 and step 103. conflict.

In addition, the IP address used by the STA does not change before and after the AP switching. From the perspective of the STA, the BSSID of the connected AP does not change, and the data is still sent and received by the same IP address. Therefore, in the embodiment of the present invention, the STA does not perceive that the AP has switched.

In the foregoing technical solution of the embodiment of the present invention, the first STA in the ESS is assigned a unique first BSSID, and the AP connected to the first STA in the ESS provides a service for the first STA based on the first BSSID. When the first AP determines that the connected first STA reaches the roaming threshold, and the first STA is in the power saving mode, the first AP sends a handover instruction to the second AP that the first STA needs to connect, indicating that the second AP is based on the first BSSID. The first STA provides a service. On the other hand, the first AP sends a wake-up frame to the first STA, indicating that the first STA keeps the awake state at the time of sending the beacon frame of the second AP, thereby enabling the first STA to receive the second AP. The transmitted beacon frame can maintain a link with the second AP according to the beacon frame sent by the second AP, and ensure that the first STA can accept the service provided by the second AP. The process of the STA connected to the AP is performed by the AP. Therefore, even if the first STA is in the power saving mode and the radio module is disabled, the AP switching of the first STA can be performed normally, and the first STA is guaranteed to be opened. After the radio module is enabled, the AP can communicate with the AP in the ESS, and the communication quality of the first STA is good because the first STA can switch the AP with the better connection signal.

In addition, when the first AP caches data for the first STA, the first AP also hands over the data cached by the first STA to the second AP, and the second AP sends the cached data to the first STA to avoid data. Lost.

In a possible implementation manner, referring to FIG. 3, before step 102, the following steps are further included:

Step 107: The first AP determines whether the beacon frame transmission time of the second AP is synchronized with the beacon frame transmission time of the second AP, and if yes, skips step 102 and directly performs step 103. If not, step 102 is performed. Also perform step 103.

Specifically, after determining that the first STA needs to switch the first STA to the second AP, it is first determined whether the time that the second AP sends the beacon frame with the first AP is synchronized, and if the synchronization is performed, the first AP can receive the first AP. The first STA of the beacon frame can receive the beacon frame sent by the second AP, and the first AP can directly perform step 103 without performing step 102.

If the time at which the second AP sends the beacon frame is not synchronized, the first AP performs step 102, so that the wake-up time of the first STA is the time when the second AP sends the beacon frame.

In the foregoing technical solution, the first AP determines whether the time at which the first AP and the second AP send the beacon frame are synchronized. When the two are synchronized, the first STA does not need to send the wake-up frame to adjust the time in which the first AP is in the awake state. When the two are not synchronized, the wake-up frame is sent to the first STA, which can ensure that the first STA can receive the beacon frame sent by the second AP, and can also send the beacon frame in the first AP and the second AP. Reduce the transmission of wake-up frames during time synchronization, saving transmission resources.

In another possible implementation, after determining that the connection with the first STA is successful, the second AP sends a handover success message to the first AP, so that the first STA knows that the first STA has successfully switched to the second AP, and After receiving the handover success message, the second AP may stop sending the wake-up frame in step 102 to the first STA.

The manner in which the second AP determines that the connection with the first STA is successful includes:

In the mode A, the second AP sends a frame that needs the first STA to return the message to the first STA, the first STA returns a message to the second AP, and the second AP receives the return message, and the first STA is determined to be successful. establish connection.

The frame that needs to be returned by the first STA may be implemented in multiple manners. For example, the frame is a data frame, and after receiving the data frame sent by the second AP, the first STA returns an ACK frame to the second AP. The ACK sent by the first STA to the second AP The frame includes the identifier of the second AP, and the second AP provides the service for the first STA based on the first BSSID, and the second AP only uses the first BSSID as its own BSSID when the first STA is served. Therefore, the second The AP determines, according to the first BSSID in the received ACK frame, that the ACK frame is sent by the first STA, and further determines that the connection with the first STA has been successfully established.

Optionally, the first STA may maintain a short-term awake state after receiving the beacon frame sent by the second AP, and therefore, the second AP may go to the first time after sending the beacon frame to the first STA. A STA sends the frame for determining whether the second AP determines whether the first STA is successfully connected, so that the first STA can receive the frame, and returns a message according to the frame.

In the mode B, the first STA in the power-saving mode may send a packet to the connected AP. After receiving the packet, the second AP may determine to successfully establish a connection with the first STA.

For example, when the first STA is in the power-saving mode, the first STA sends a record of the power-saving mode to the connected AP, and the second AP receives the packet that includes the record to determine that the connection is successfully established with the first STA.

In the foregoing technical solution, the second AP can determine to establish a connection with the first STA according to the received message sent by the first STA, and send a handover success message to the first AP, so that the first STA knows that the first STA has successfully switched to Second AP. The first AP may send a wake-up frame to the first STA before receiving the handover success message, to ensure that the first STA can receive the beacon frame sent by the second AP, and after the first AP receives the wake-up frame, stop the The first STA sends the wake-up frame, which not only saves transmission resources, but also avoids confusion of the response of the first STA.

The embodiment of the present invention further provides an apparatus 200 for switching an AP, where the apparatus 200 functions as an AP in a WLAN. 4 is a schematic structural diagram of an apparatus 200. The device 200 includes a processor 201 and a transceiver 202.

The processor 201 is configured to: determine that the STA connected to the device 200 is in a power saving mode, where the device 200 provides a service for the STA according to the BSSID corresponding to the STA, and the BSSID and the corresponding location of the STA Determining, by the STA, that the BSSIDs of the other STAs in the same ESS are different; determining that the second AP in the ESS is the target AP, the target AP is the AP that is connected after the STA is switched, and generating a wake-up frame, The awake frame is used to indicate that the STA is in an awake state when the second AP sends a beacon frame based on the BSSID corresponding to the STA; generating a handover instruction, where the handover instruction is used to indicate that the second AP is based on the The BSSID corresponding to the STA provides a service for the STA;

The transceiver 202 is coupled to the processor 201, configured to: send the wake-up frame to the STA; and send the handover instruction to the second AP.

In the embodiment of the present invention, the processor 201 and the transceiver 202 may be two separate components, and the two are connected by a bus. In addition, the processor 201 and the transceiver 202 may be integrated, which is not limited in the embodiment of the present invention.

The processor 201 can be a processing element or a collective name of a plurality of processing elements. For example, the processor can be a central processing unit (CPU), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention.

The transceiver 202 includes an antenna and may also include a radio frequency module coupled to the antenna. Optionally, when the device 200 communicates with the second AP through a wired network (such as a fiber network or the like), the transceiver 202 includes a data communication type of a wired communication type, such as an Ethernet, in addition to the foregoing radio frequency module and the antenna. Data transceiver.

In a possible implementation, before being used to generate the wake-up frame, the processor 201 is further configured to: determine that the beacon frame transmission time of the device 200 is not synchronized with the beacon frame transmission time of the second AP.

In a possible implementation, the wake-up frame includes a first beacon frame, the first beacon frame includes a field for updating the STA wake-up time, and the field for updating the STA wake-up time And configured to instruct the STA to adjust an awake time to a time when the second AP sends a beacon frame based on a BSSID corresponding to the STA.

In a possible implementation, the transceiver 202 is further configured to: receive a second beacon frame sent by the second AP;

The processor 201 is further configured to: determine a time when the transceiver receives the second beacon frame, and according to a beacon frame transmission time of the device 200, and the transceiver receives the second beacon frame The time determines a time interval before the beacon frame transmission time of the device 200 and the beacon frame transmission time of the second AP; and determines a field for updating the STA wake-up time according to the time interval.

In one possible implementation, the wake-up frame includes a third beacon frame, the third beacon frame including a field indicating that the STA remains awake.

In a possible implementation, the wake-up frame further includes: at least one data frame sent after the third beacon frame, the at least one data frame is used to keep the STA in an awake state.

In one possible implementation, the at least one data frame includes a null data frame.

In a possible implementation, the device 200 further includes a memory 203, which can be used to: store data sent by the connected STA, store data sent by other network elements to the STA, and store the STA's status record (if it is in the province). Electrical mode), storing instructions sent by other network elements to device 200, and the like.

Optionally, the memory 203 can also store executable instructions, and the processor 201 reads and runs the executable instructions in the memory 203 to implement the functions of the device 200 in the embodiment of the present invention.

The memory 203 may be a storage element or a collective name of a plurality of storage elements, and is used to store executable program code or parameters, data, and the like required for the operation of the device. And the above memory 203 may include random access memory (RAM), may also include non-volatile memory (NVM), and the like.

It should be noted that the memory 203 and the Ethernet data transceiver in FIG. 4 are represented by dashed boxes, indicating that they are not necessary modules for the AP to implement its functions in the embodiment of the present invention. In general, the AP also has functions beyond those described in the embodiments of the present invention that need to be implemented based on the memory 203 and/or the Ethernet data transceiver.

For the specific implementation of the operations performed by the component modules included in the foregoing device 200, reference may be made to the corresponding steps performed by the first AP in the corresponding embodiments of FIG. 2 and FIG. 3, which are not repeatedly described in the embodiments of the present invention.

The embodiment of the invention further provides a device for switching an AP, which can be used as an AP in a WLAN. The device includes a processor and a transceiver.

The transceiver is configured to receive a handover instruction sent by the first AP, where the handover instruction includes an identifier of the first STA.

The processor is coupled to the transceiver, and is configured to: control the AP to provide service for the first STA based on the first BSSID generated for the first STA.

In a possible implementation, the transceiver is further configured to: receive any message sent by the first STA;

The processor is further configured to: after the transceiver receives any message sent by the first STA, generate a handover success message;

The transceiver is further configured to: send a handover success message to the first STA.

In a possible implementation, the processor is further configured to: after the transceiver receives the handover instruction, generate a frame that requires the first STA to return a message;

The transceiver is further configured to: send, to the first AP, the frame that needs the first STA to return a message.

For the specific implementation of the operations performed by the foregoing APs, the corresponding steps performed by the second AP in the embodiment of the present invention are not described herein.

The embodiment of the invention further provides a communication system, which includes multiple APs and multiple STAs.

The first AP of the multiple APs is configured to: determine that the first STA connected to the first AP is in a power saving mode, and determine that the first STA needs to switch to the second AP in the same ESS; and STA sends wake-up frame, wake-up frame And configured to: send, by the first STA, a beacon frame time to the second AP, and send a handover instruction, where the handover instruction is used to enable the second AP to be the first STA based on the first BSSID allocated for the first STA Provide services;

The first STA of the multiple STAs is configured to: receive the wake-up frame, and keep the awake state according to the wake-up frame when the second AP sends the beacon frame;

The second AP of the multiple APs is configured to: receive a handover instruction sent by the first AP, where the handover instruction includes an identifier of the first STA; and provide a service for the first STA based on the first BSSID.

In a possible implementation, before the first AP sends the wake-up frame to the STA, it is determined that the beacon frame transmission time of the UE is not synchronized with the beacon frame transmission time of the second AP.

In a possible implementation, the wake-up frame includes a first beacon frame, the first beacon frame includes a field for updating the first STA wake-up time, the field is used to indicate that the first STA will wake up The time is adjusted to a time when the second AP sends a beacon frame based on the first BSSID corresponding to the first STA.

In a possible implementation, the first AP determines the time of receiving the second beacon frame sent by the second AP before sending the wake-up frame to the first STA; sending time according to the beacon frame of the self and determining the first The time of the second beacon frame sent by the second AP determines a time interval before the beacon frame transmission time of the first AP and the beacon frame transmission time of the second AP; determining, according to the time interval, the The field of the first STA wakeup time is updated.

In a possible implementation, the wake-up frame further includes: at least one data frame transmitted after the third beacon frame, the at least one data frame being used to keep the first STA in an awake state.

In a possible implementation, the second AP is further configured to: after receiving any message sent by the first STA, send a handover success message to the first STA;

The first AP is further configured to: receive a handover success message, and stop sending the wake-up frame to the first STA.

In a possible implementation, the communication system further includes a roaming controller, configured to allocate a unique BSSID to each STA in the same ESS, so that the AP connected to each STA serves the STA based on the BSSID allocated for the STA. .

In a possible implementation, the first AP and the second AP are further configured to: report, to the roaming controller, a monitoring value of the signal indicator of the first STA;

The roaming controller is further configured to: determine, according to the monitoring value, that the first STA reaches the roaming threshold, and determine that the second AP is the target AP, and send a handover triggering instruction to the first AP;

The first AP is configured to: determine that the first STA reaches the roaming threshold, and determine that the second AP is the target AP, including: receiving the handover triggering instruction, determining, according to the handover triggering instruction, that the first STA reaches the roaming threshold, and determining that the second AP is the target AP.

For the specific implementation of the operations performed by the devices included in the above system, reference may be made to the corresponding steps in the embodiments of FIG. 2 and FIG. 3, which are not described in detail in the embodiments of the present invention.

The embodiment of the invention further provides an apparatus for switching an AP in a WLAN, where the WLAN includes multiple APs and multiple STAs. Referring to Figure 5, the apparatus includes:

The first determining module 301 is configured to determine that the STA connected to the device is in a power saving mode, where the device provides a service for the STA based on a BSSID corresponding to the STA, and the BSSID and the corresponding to the STA The BSSID corresponding to any STA of the STA in the same ESS is different;

The second determining module 302 is configured to determine that the second AP in the ESS is a target AP, and the target AP is an AP that is connected after the STA is switched;

The first sending module 303 is configured to send a wake-up frame to the STA, where the wake-up frame is used to indicate that the STA is in an awake state when the second AP sends a beacon frame based on the BSSID corresponding to the STA;

The second sending module 304 is configured to send a handover instruction to the second AP, where the handover instruction is used to indicate that the second AP provides a service for the STA based on a BSSID corresponding to the STA;

The stop service module 305 is configured to stop providing services for the STA after the second sending module sends the switching instruction.

In a possible implementation, the device further includes:

The third determining module 306 is configured to determine, before the first sending module sends the wake-up frame, a time for receiving the second beacon frame sent by the second AP, and send the time according to the beacon frame of the The time at which the second beacon frame is received determines a time interval before a beacon frame transmission time of the apparatus and a beacon frame transmission time of the second AP; and determining the use according to the time interval. The field for updating the STA wakeup time.

For the specific implementation of the operations performed by the various components of the foregoing apparatus, reference may be made to the corresponding steps performed by the first AP in the embodiments of FIG. 2 and FIG. 3, which are not described in detail in the embodiments of the present invention.

Those skilled in the art will appreciate that embodiments of the present invention can be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or a combination of software and hardware. Moreover, the invention can take the form of a computer program product embodied on one or more computer readable storage medium (including but not limited to magnetic memory, optical memory, etc.) including program code.

The present invention has been described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (system), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or FIG. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine for the execution of instructions for execution by a processor of a computer or other programmable data processing device. Means for implementing the functions specified in one or more of the flow or in a block or blocks of the flow chart.

It will be apparent to those skilled in the art that various modifications and changes can be made in the present invention without departing from the scope of the invention. Thus, it is intended that the present invention cover the modifications and the modifications thereof

Claims

A method for switching an access point (AP) in a wireless local area network (WLAN), the method comprising:

The first AP determines that the station (STA) connected to the first AP is in a power saving mode, where the first AP is one of the multiple APs, and the first AP is based on the basic corresponding to the STA a service set identifier (BSSID) serving the STA, the BSSID corresponding to the STA being different from the BSSID corresponding to any STA of the STA in the same extended service set (ESS);

The first AP determines that the second AP in the ESS is the target AP, and the target AP is the AP that is connected after the STA is switched;

The first AP sends a wake-up frame to the STA, where the wake-up frame is used to indicate that the STA is in an awake state when the second AP sends a beacon frame based on the BSSID corresponding to the STA;

The first AP sends a handover instruction to the second AP, where the handover instruction is used to indicate that the second AP provides a service for the STA based on a BSSID corresponding to the STA;

After the first AP sends the handover command, the first AP stops providing services for the STA.
The method of claim 1, wherein the wake-up frame comprises a first beacon frame, the first beacon frame comprising a field for updating the STA wake-up time, the The STA wake-up time field is used to instruct the STA to adjust the wake-up time to the time when the second AP sends a beacon frame based on the BSSID corresponding to the STA.
The method of claim 2, wherein before the first AP sends a wake-up frame to the STA, the method further includes:

Determining, by the first AP, a time when the second beacon frame sent by the second AP is received;

Determining, by the first AP, a beacon frame transmission time of the first AP and a beacon frame transmission of the second AP according to the beacon frame transmission time of the UE and the time of receiving the second beacon frame. Time interval before time;

The first AP determines, according to the time interval, the field used to update the STA wakeup time.
The method of claim 1 wherein the wake-up frame comprises a third beacon frame, the third beacon frame comprising a field indicating that the STA remains awake.
The method of claim 4, wherein the wake-up frame further comprises: at least one data frame transmitted after the third beacon frame, the at least one data frame being used to keep the STA awake status.
The method of claim 5 wherein said at least one data frame comprises a null data frame.
A device for switching an access point (AP) in a wireless local area network (WLAN), the device being the first AP in the WLAN, wherein the device includes:

a first determining module, configured to determine that a station (STA) connected to the device is in a power saving mode, where the device provides a service for the STA based on a basic service set identifier (BSSID) corresponding to the STA, The BSSID corresponding to the STA is different from the BSSID corresponding to any STA of the STA in the same extended service set (ESS);

a second determining module, configured to determine that the second AP in the ESS is a target AP, and the target AP is an AP that is connected after the STA is switched;

a first sending module, configured to send a wake-up frame to the STA, where the wake-up frame is used to indicate that the STA is in an awake state when the second AP sends a beacon frame based on a BSSID corresponding to the STA;

a second sending module, configured to send a handover instruction to the second AP, where the handover instruction is used to indicate that the second AP provides a service for the STA based on a BSSID corresponding to the STA;

The service module is configured to stop providing service to the STA after the second sending module sends the switching instruction.
The device of claim 7, wherein the wake-up frame comprises a first beacon frame, the first beacon frame comprising a field for updating the STA wake-up time, the The STA wake-up time field is used to instruct the STA to adjust the wake-up time to the time when the second AP sends a beacon frame based on the BSSID corresponding to the STA.
The device according to claim 8, wherein the device further comprises:

a third determining module, configured to determine, before the first sending module sends the wake-up frame, a time for receiving the second beacon frame sent by the second AP; and sending time and receiving according to the beacon frame of the first Determining, by the time interval to the second beacon frame, a time interval before a beacon frame transmission time of the device and a beacon frame transmission time of the second AP; and determining, according to the time interval, the Update the field of the STA wakeup time.
The device of claim 7, wherein the wake-up frame comprises a third beacon frame, the third beacon frame comprising a field indicating that the STA remains awake.
The device of claim 10, wherein the wake-up frame further comprises: at least one data frame transmitted after the third beacon frame, the at least one data frame being used to keep the STA awake status.
The device of claim 11 wherein said at least one data frame comprises a null data frame.
An access point (AP), the AP includes:

a processor, configured to: determine that a station (STA) connected to the AP is in a power saving mode, where the AP provides a service for the STA based on a basic service set identifier (BSSID) corresponding to the STA, where The BSSID corresponding to the STA is different from the BSSID corresponding to the STA in the same extended service set (ESS); the other AP in the ESS is the target AP, and the target AP is the An AP connected after the STA is switched; generating a wake-up frame, where the wake-up frame is used to indicate that the STA is in an awake state when the another AP sends a beacon frame based on the BSSID corresponding to the STA; generating a handover command, where The switching instruction is used to indicate that the another AP provides a service for the STA based on a BSSID corresponding to the STA;

a transceiver coupled to the processor, configured to: send the wake-up frame to the STA; and send the handover instruction to the another AP.
The AP of claim 13, wherein the wake-up frame comprises a first beacon frame, the first beacon frame comprising a field for updating the STA wake-up time, the The STA wake-up time field is used to instruct the STA to adjust the wake-up time to the time when the another AP sends a beacon frame based on the BSSID corresponding to the STA.
The AP according to claim 14, wherein the transceiver is further configured to: receive a second beacon frame sent by the another AP;

The processor is further configured to: determine a time when the transceiver receives the second beacon frame, and according to a beacon frame transmission time of the AP, and the transceiver receives the second beacon frame Determining a time interval before a beacon frame transmission time of the AP and a beacon frame transmission time of the another AP; and determining, according to the time interval, the field for updating the STA wake time .
The AP of claim 13, wherein the wake-up frame comprises a third beacon frame, the third beacon frame comprising a field indicating that the STA remains awake.
The AP according to claim 16, wherein said wake-up frame further comprises: at least one data frame transmitted after said third beacon frame, said at least one data frame being used to keep said STA awake status.
The device of claim 17 wherein said at least one data frame comprises an empty data frame.