WO2020187238A1

WO2020187238A1 - Method for switching access point, and terminal

Info

Publication number: WO2020187238A1
Application number: PCT/CN2020/079925
Authority: WO
Inventors: 周琪; 俞居正; 白小飞
Original assignee: 华为技术有限公司
Priority date: 2019-03-18
Filing date: 2020-03-18
Publication date: 2020-09-24
Also published as: CN111726837A; CN111726837B

Abstract

Disclosed are a method for switching an access point, and a terminal. The method comprises: an STA attempting, on a first channel, to receive a beacon from a first AP; the STA sending a detection request on a second channel; the STA receiving, on the second channel, a detection response given by a second AP; after the quality of communication between the STA and the second AP is determined, once a detection condition is satisfied, the STA immediately sending a detection request on the first channel to prompt the first AP to reply with a detection response, and determining, according to a reply situation of the first AP, whether an emergency roaming condition is satisfied; and if the emergency roaming condition is satisfied, the STA immediately attempting to be associated with the second AP, so as to ensure smooth communication of the STA.

Description

Method and terminal for switching access point

This application claims the priority of a Chinese patent application filed on March 18, 2019 with the application number 201910203932.9 and the invention title "A method and terminal for switching access points", the entire content of which is incorporated into this application by reference .

Technical field

This application relates to the field of communications, and in particular to a method and terminal for switching access points.

Background technique

In the intelligent logistics automated guided vehicle (AGV) warehousing (hereinafter referred to as smart warehousing), the access point (AP) provides wireless local area network (wireless local area network) services for the mobile AGV. A station (STA) is installed to establish a connection with the AP and report its own location and other information to the server in real time. The server needs to provide the AGV walking route and related environmental information in real time. In view of the strict requirements of intelligent storage in real-time and packet loss rate, it is necessary to carry out targeted design in the aspects of signal link quality detection, link quality assurance and improvement of roaming initiative.

The information about the link quality between the working channel and the associated AP of the STA mainly comes from the received signal strength indication (RSSI) value of the message or beacon; scanning is triggered when the working channel RSSI value is lower than the threshold. And choose a more suitable AP to roam according to the scan results.

However, when it is judged that the RSSI is low, it is necessary to actively scan multiple channels to obtain real-time AP information on other channels, and roam according to the scanning results. The channel scanning time is long, which will cause a high probability for mobile storage scenarios with high real-time performance. Continuous packet loss affects the stability of STA operation.

Summary of the invention

This application provides a method and terminal for switching access points, which can enable STAs to obtain information of associated APs while obtaining information of other non-associated APs. When roaming and switching APs are needed, they can switch to the appropriate AP in time , To ensure the smooth communication of STA and improve the stability of STA operation.

In view of this, the first aspect of this application proposes a method for switching access points, which can be applied to the algorithm logic of WLAN terminals, and the specific devices involved in the execution of the method can correspond to corresponding ones in the WLAN terminal. Functional entity. The method may include: an STA tries to receive a beacon from a first AP on a first channel, the STA is associated with the first AP, the first channel is the working channel of the first AP; the STA is on a second channel Send a probe request; the STA receives a probe response from the second AP on the second channel, and determines the communication quality between the STA and the second AP based on the probe response; when determining the relationship between the STA and the second AP After the inter-communication quality, once the detection conditions are met, the STA immediately sends a detection request on the first channel to prompt the first AP to reply to the detection response, and determines whether the emergency roaming conditions are met according to the response of the first AP, Wherein, the detection condition includes the failure of an attempt to receive a beacon from the first AP; if the emergency roaming condition is met, and the communication quality between the STA and the second AP meets the handover condition, the STA immediately tries to communicate with the second AP. The second AP is associated, and the handover condition includes that the communication signal strength between the STA and the second AP is greater than a first threshold. Emergency roaming can improve the timeliness of AP handover. During emergency roaming, the communication quality with AP is not detected, but the historical data of the communication quality detected before is used to determine the handover target.

Optionally, in some implementation manners of the present application, the detection condition further includes that the signal strength of the most recently received beacon from the first AP is less than a second threshold. The communication quality reflected by the signal strength of the last beacon is closer to the real-time communication quality.

Optionally, in some implementation manners of the present application, the single stay duration of the STA on the first channel is the first duration, the single stay duration of the STA on the second channel is the second duration, and the first duration The sum of the duration and the second duration does not exceed 200 milliseconds. It can be seen from this possible implementation that a relatively high-frequency channel scanning period is adopted, so that the STA can receive the information of the associated AP or other information within a working period without affecting the reception of service packets. The link status of the AP enables the STA to select the appropriate AP by scanning the link status of other APs in time when the communication with the associated AP is not good, which improves the timeliness of AP switching.

Optionally, in some implementations of this application, the beacon interval of the first AP is a third duration, the third duration is less than or equal to 50 milliseconds, the first duration is greater than the third duration, and the second duration is less than The third duration. It can be seen from this possible implementation that, by setting the relationship between the first duration, the second duration, and the third duration, the first AP can also receive at least one message sent by the first AP while staying on the first channel. Beacon; and the STA loses at most one beacon sent by the first AP during the second channel scanning period. It will not have a major impact on the normal operation of the STA during the period when it leaves the first channel. It is guaranteed that the STA can be in a working cycle. After receiving the information of the associated AP, the link status of other APs can also be obtained, while avoiding the occurrence of packet loss and reducing the packet loss rate of the STA.

Optionally, in some implementations of the present application, the STA dynamically adjusts the first duration, where if the STA has no service on the first channel, the first duration is greater than 100 milliseconds; if the STA is on the first channel If a channel has service, the first duration is between 50 milliseconds and 100 milliseconds. It can be seen from this possible implementation that, by judging the STA’s service condition on the first channel, the STA’s working cycle duration is optimized, which further reduces the duration of a single cycle, improves the real-time performance of the STA’s acquisition of information, and is more realistic. Working status.

Optionally, in some implementation manners of the present application, the emergency roaming condition includes that the delay between receiving the probe response from the first AP and sending the probe request on the first channel by the STA is greater than a third threshold . It can be seen from this possible implementation that the setting of the emergency roaming conditions can be determined based on the time difference between the sending of the probe request and the receiving of the probe response. Because the delay is higher in the smart logistics scenario, the delay is greater than the third Emergency roaming is carried out in time under the threshold condition, which avoids the occurrence of packet loss and improves the timeliness of AP handover.

The second aspect of the present application provides a WLAN terminal, the WLAN terminal having the function of implementing the above-mentioned first aspect or any one of the possible implementation methods of the first aspect. This function can be realized by hardware, or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above-mentioned functions.

In a third aspect, the present application provides another WLAN terminal. The WLAN terminal may include: a processor, a memory, and a WLAN interface; the memory is used to store a program; the processor is used to try to receive the second channel through the WLAN interface on the first channel. A beacon of an AP, the STA is associated with the first AP, the first channel is the working channel of the first AP; the probe request is sent on the second channel; the probe reply from the second AP is received on the second channel Response, and determine the communication quality between the STA and the second AP according to the probe response; after determining the communication quality between the STA and the second AP, once the detection conditions are met, immediately send on the first channel The probe request is used to prompt the first AP to reply a probe response, and according to the response of the first AP, it is determined whether the emergency roaming condition is satisfied, wherein the detection condition includes an attempt to receive a beacon from the first AP failed; if the emergency roaming If the condition is met, and the communication quality between the STA and the second AP meets the handover condition, it will immediately try to associate with the second AP. The handover condition includes that the communication signal strength between the STA and the second AP is greater than the first A threshold.

In a fourth aspect, the present application provides a computer-readable storage medium, including instructions, which when run on a computer, cause the computer to execute the method described in the foregoing first aspect and any optional implementation manner. The computer storage medium includes: U disk, mobile hard disk, read-only memory (read-only memory, ROM), random access memory (random access memory, RAM), magnetic disk or optical disk and other media that can store program codes.

In the fifth aspect, this application provides a computer program product, which when running on a computer, causes the computer to execute the method described in the foregoing first aspect and any optional implementation manner.

In a sixth aspect, the present application provides a chip system including a processor for supporting the WLAN terminal to implement the functions involved in the above aspects, for example, sending or processing the data and/or information involved in the above methods . In a possible design, the chip system further includes a memory for storing necessary program instructions and data for the WLAN terminal. The chip system can be either a WLAN terminal or a system chip used in the WLAN terminal to perform corresponding functions.

It can be seen from the above technical solutions that this application has the following advantages: real-time scanning allows STAs to obtain information of associated APs while obtaining information of other non-associated APs. When roaming is required to switch APs, the STA can use the historical record Scanning the information of non-associated APs selects the appropriate AP and switches in time to ensure smooth communication of the STA, which can effectively reduce the packet loss rate of the STA, improve the stability of STA operation and the timeliness of AP switching.

Description of the drawings

In order to more clearly describe the technical solutions of the embodiments of the present application, the following will briefly introduce the embodiments and the accompanying drawings required in the description of the prior art. Obviously, the drawings in the following description are only some implementations of the present application. For example, other drawings can be obtained from these drawings.

Figure 1 is a schematic diagram of the operation scene of the automatic guided transport vehicle;

FIG. 2 is a diagram of the structure of a wireless local area network site device provided by an embodiment of the present application;

FIG. 3 is a schematic diagram of the relationship between the division of the duration of the STA working channel and the duration of the AP sending a beacon according to an embodiment of the present application;

FIG. 4 is a schematic diagram of a method for switching access points provided by an embodiment of the present application;

FIG. 5 is a flowchart of a method for switching access points provided by an embodiment of the present application;

FIG. 6 is a schematic structural diagram of a WLAN terminal provided by an embodiment of the present application;

FIG. 7 is a schematic structural diagram of another WLAN terminal provided by an embodiment of the present application;

FIG. 8 is a schematic structural diagram of another WLAN terminal provided by an embodiment of the present application.

detailed description

The embodiment of the application provides a method and device for switching access points, which can be used in a scenario where an AGV with an STA initiates roaming and switches APs during operation. The real-time scanning method allows the STA to obtain the associated AP information Obtain the information of other non-associated APs at the same time. When roaming and switching APs are needed, the appropriate AP is selected by scanning the information of the non-associated APs in the history record and switching in time to ensure the smooth communication of STAs and effectively reduce STAs. The packet loss rate improves the stability of STA operation.

In order to enable those skilled in the art to better understand the solutions of the application, the technical solutions in the embodiments of the application will be described below in conjunction with the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the application. Examples, not all examples. Based on the embodiments in this application, they should all fall within the protection scope of this application.

As shown in Figure 1, it is a schematic diagram of the operation scene of the automated guided vehicle. In the intelligent logistics automated guided vehicle (AGV) storage (hereinafter referred to as the intelligent storage), the access point (AP) ) Provides wireless local area network services for mobile AGVs. A station (STA) is installed on the AGV to establish a connection with the AP and report its location and other information to the server in real time. The server needs to provide the AGV walking route in real time And related environmental information. In view of the strict requirements of intelligent storage in real-time and packet loss rate, it is necessary to carry out targeted design in the aspects of signal link quality detection, link quality assurance and improvement of roaming initiative.

It should be noted that multiple APs and AGVs are shown in FIG. 1, and this number is only for scenario description, that is, in the applicable scenarios of this embodiment, one or more AGVs can run the method provided in this embodiment. It can also be a handover between one or more APs. The specific number depends on the actual scenario and there is no limitation here.

Since the STA needs to frequently switch between multiple APs, it needs to obtain the link quality, and the information to determine the link quality between the STA's working channel and the associated AP mainly comes from the received signal strength indicator of the message or beacon ( received signal strength indication, RSSI) value; when the working channel RSSI value is lower than the threshold, scanning is triggered, and a more appropriate AP is selected for roaming according to the scanning result. However, the roaming conditions of the STA completely depend on passively receiving the signal strength sent by the associated AP. For the mobile storage scenario with high real-time, it may cause misjudgment of information and affect the stability of STA operation.

In addition, due to the high roaming threshold of the STA, the STA has strong stickiness and poor initiative with the currently associated AP. When judging that the RSSI is low, it needs to actively scan multiple channels to obtain other AP information, and roam according to the scanning results. Then switch to a suitable AP, this scanning process takes a long time, and for high real-time mobile storage scenarios, it will increase the probability of STA packet loss.

In order to solve the above-mentioned problem, the embodiment of the present application provides a method for switching access points. The method can be applied to a device with a wireless local area network (WLAN) STA, such as an AGV with an STA. As shown in Figure 2, it is a diagram of the wireless local area network site equipment architecture provided by the embodiments of this application. The WLAN STA equipment includes a WIFI chip, a control processor (central processing unit, CPU), a power supply module, interfaces and storage peripherals, and radio frequency circuits. And antennas, among them, the WIFI chip only contains the wireless part of the circuit, which can be divided into application layer, lower media access control (LMAC) layer, and physical (PHY) layer according to its functions. The CPU includes upper media control Access (upper media access control, UMAC) layer, upper driver and application layer. The method for switching access points can run in the application layer of the CPU in the WLAN STA device. For example, the model of the CPU can be QCA9882, MT7620 series, the method can be written through an algorithm, or an application program, and complete the reception and transmission of related signals through interaction with the WIFI chip.

In this embodiment, the STA can communicate with the AP in the form of a beacon. It can be understood that since the beacon is a type of WLAN frame, and the WLAN frame includes data frames, control frames, and management frames, in the following embodiments, In some possible scenarios, the beacon used can also be replaced with other communication forms based on data frames, control frames or management frames in the IEEE 802.11 protocol, for example: STA sends probe request, qos null data to obtain link quality, etc. , There is no limitation here.

First, the embodiment of this application optimizes the scanning mechanism and cycle duration of the STA. Among them, the STA scans the first channel and the second channel with a working cycle of up to 200ms, where the first channel is the working channel of the associated AP, and the first channel is the working channel of the associated AP. The second channel is a collective term for the working channels of unassociated APs. It can be understood that there can be one or more unassociated APs. The specific scenario depends on the actual situation. Correspondingly, the second channel can be for multiple unassociated APs. The set of working channels, that is, the second channel may be a path that is explained because the associated AP broadcasts, and multiple non-associated APs receive the broadcast and respond to it.

In this embodiment, the duty cycle can be a scan with a fixed duration, or it can be divided into cycles of different durations, that is, the duration of the first cycle can be 100ms, and the duration of the second cycle is 200ms, where the cycle The change process may be response and staff settings, or adjustment in response to the period of the associated AP sending beacons. The specific duration and adjustment method depend on the actual scenario, and there is no limitation here.

The following describes each time length division and the corresponding relationship with the accompanying drawings. As shown in FIG. 3, it is a schematic diagram of the relationship between the time length division of the STA working channel and the AP sending beacon duration provided by the embodiment of the present application. A working cycle time of a STA is divided into the dwell time of the first channel and the scan time of the second channel. The dwell time of the first channel of the STA is the first duration, and the STA is in the working channel for communicating with the associated AP. The STA can receive the beacon sent by the associated AP; the scanning time of the STA on the second channel is the second duration, and the STA is on a working channel that is not communicating with the associated AP. At this time, the STA can broadcast a probe request, such as probe request, and then receive The probe response sent by the non-associated AP, for example: probe response; the periodic time interval for the associated AP to send beacons is the third time period. Since this embodiment adopts the high-frequency scanning method, the third time period can be less than or equal to 50 milliseconds. The STA loses at most one beacon sent by the associated AP during the second channel scan, then the third duration>the second duration; in addition, to ensure that the STA can receive at least one beacon sent by the associated AP during the first channel communication period, then The third duration<the first duration, it can be understood that the third duration can be considered to be set, and the corresponding first duration and second duration will be adjusted accordingly according to the above-mentioned magnitude relationship according to the setting of the third duration.

In addition, Figure 3 shows one working cycle of STA and three sending cycles of AP. It should be noted that in actual scenarios, multiple working cycles of STA or multiple sending cycles of AP may be included. Depending on the scene, there is no restriction here.

It is understandable that the STA can obtain the link status of different unassociated APs in different work cycles, and can obtain the link status of at least one unassociated AP in each work cycle, and then compare the link status of these unassociated APs. Select the storage within the preset time period to facilitate analysis and selection when required. For example: STA will store the basic service set identifier (BSSID) of multiple unassociated APs in the last 3 working cycles When you need to select an AP and switch, you can scan the BSSID of the unassociated AP to select.

It is understandable that, in the case of satisfying the relative size relationship, the above-mentioned first duration, second duration, and third duration can be artificially set, or they can be calculated based on the current STA's business volume. The specific duration depends on actual scenarios. There is no restriction here. For example, in a possible scenario, the STA has no service operation during the stay time of the working channel. In order to save the working time in this case, the stay time of the STA on the first channel when there is no service can be 50 milliseconds to 100 milliseconds. Between milliseconds, that is, 50 milliseconds, can be recorded as the preset minimum value, so that the stay time of the STA on the first channel when there is service is between 100 milliseconds and 200 milliseconds, that is, 200 milliseconds can be recorded as the preset maximum value, where , The preset minimum value<the first duration<the preset maximum value, considering that the STA can receive at least one beacon sent by the associated AP during the working channel communication, the third duration<the preset minimum value.

Optionally, in a possible scenario, before leaving the first channel, the STA can send a power saving frame to the associated AP. At this time, the STA will stop receiving data frames and enter the sleep state. The associated AP will send the data that needs to be sent. The frame is buffered, and after receiving the power-saving frame sent by the STA, the wake-up command is identified in the beacon, and the STA resumes normal reception of the data frame.

Through the optimization of the scanning mechanism of the above STA, the STA can receive the beacon sent by the associated AP or the related information sent by other APs (non-associated APs) within a working cycle to obtain the information of the unassociated AP. Status information of the link with the STA; through the cooperation of the STA's working time division and the AP's sending beacon period, the STA can lose at most one beacon sent by the associated AP when it leaves the working channel to ensure the STA's normal communication.

In the following, in conjunction with the optimization of the scanning mechanism of the above STA, the access point switching method provided by the embodiment of the present application is described with reference to the accompanying drawings. As shown in FIG. 4, it is a schematic diagram of a method for switching access points provided by an embodiment of the present application. , The method includes but is not limited to the following steps:

401. The STA tries to receive a beacon from the first AP on the first channel.

In this embodiment, the first AP is the AP that the STA is currently associated with, and the first channel is the working channel between the first AP and the STA. The first AP periodically sends beacons, and the STA will try to receive and obtain the RSSI. The STA can also receive other WLAN frames sent by the first AP, such as data frames or management frames, so the STA can also judge the communication status with the first AP based on the reception strength of other WLAN frames.

402. The STA sends a probe request on the second channel.

In this embodiment, the second channel is a channel between unassociated APs and STAs, where there may be one or more unassociated APs. After the STA sends a probe request, non-associated APs within a certain range will receive the probe request and reply with a probe response.

403. The STA receives a probe response from the second AP on the second channel, and determines the communication quality between the STA and the second AP according to the probe response.

In this embodiment, the STA can obtain the link quality with the second AP according to the probe response returned by the second AP. It can be understood that since the STA can send the probe request in the form of broadcast, the responding AP can be There are multiple. In this case, the STA can obtain the corresponding link quality according to these responses. The link quality includes RSSI, and stores the BSSID and RSSI of the corresponding AP.

404. After determining the communication quality between the STA and the second AP, determine whether the communication quality between the STA and the first AP meets the detection condition.

In this embodiment, the detection condition for the communication quality between the STA and the first AP may be determined based on the loss of the beacon. Specifically, it may be to determine the loss of the most recently received beacon, or it may be in advance. It is assumed that the number of lost beacons in the time period exceeds the first threshold. For example, the number of lost beacons of the STA exceeds 3 in the last 5 working cycles.

Optionally, judging the loss of a beacon can be done based on the cooperation of the STA controller’s kernel state counter and the user’s timer. First, the STA controller’s kernel state enables the counter. Each time a beacon is received, the counter is incremented by 1 , When the value reaches the preset upper limit, it returns to zero; in addition, the user mode of the STA controller starts the timer, and the working period of the timer is higher than the period of the associated AP to send the beacon. For example, if the beacon sending period is 50ms, the timer The working period of the can be 60ms; then, the timer can check the value increase of the timer, if it is 0, it is regarded as a beacon loss.

In this embodiment, if there is no beacon received last time, the RSSI value of the last communication with the first AP can also be determined. If the RSSI value is less than the second threshold, the difference between the STA and the first AP The communication quality satisfies the detection conditions; it is understandable that the RSSI value can also be judged as the number of RSSI strengths lower than the second threshold within the preset time period reaches the third threshold, for example: if the STA has worked in the last 5 If the RSSI strength of 3 working cycles in the cycle is lower than 110 dBm, the communication quality between the STA and the first AP meets the detection conditions.

It can be understood that the determination of the RSSI intensity can be based on the comparison with the second threshold; it can also be determined based on the range determined by the second threshold. For example, when the RSSI intensity is within the range of 100dBm±5dB, it is normal. Below the range is weak strength; the second threshold value can also be used as a range and a floating value is used for judgment. The specific judgment method depends on the actual scene and is not limited here.

Optionally, the foregoing determination of the beacon loss or the strength of RSSI may also be based on the determination of abnormal continuity, that is, it is determined that the number of consecutive lost beacons within a preset time period exceeds the first threshold, or, at a preset time The number of RSSI strengths in the segment below the second threshold continuously reaches the third threshold.

It is understandable that the setting of the preset conditions for the beacon can be a combination of one or more of the above descriptions, for example: only determine the loss of the beacon or determine the loss of the beacon and determine the strength of the RSSI In addition, in the process of judging multiple conditions, the judging of multiple period data can be one by one or simultaneously. The specific judging method depends on the actual scene and is not limited here.

405. The STA immediately sends a probe request on the first channel.

In this embodiment, once the STA's communication quality on the first channel meets the preset conditions, the STA can immediately send a link detection request to the associated AP to determine the real-time status of the associated link. Specifically, the STA can send a probe request The frame waits for the probe response frame that the AP responds to, or you can quickly ping the gateway to wait for the ACK response. The specific detection method depends on the actual scenario and is not limited here.

It is understandable that link detection can feed back the communication status of the STA to the associated AP. The associated AP can determine the communication status of the first AP to the STA in the last cycle or multiple cycles, and generate related messages, such as: Analysis of the difference between the RSSI value communicated by the STA to the first AP and the RSSI value communicated by the associated AP to the STA.

406. Determine whether the emergency roaming condition is met according to the response of the first AP.

In this embodiment, whether the first AP satisfies the emergency roaming condition may include multiple situations. First, after the STA sends a probe request to the first AP, the STA does not receive the response from the first AP. For example, the STA quickly pings the gateway to determine whether it will receive an ACK response from the first AP, and judge whether it will receive an ACK response from the first AP. Meet the roaming conditions.

Second, after the STA sends a probe request to the first AP, it receives a probe response, but the RSSI value of the probe response is less than the preset threshold. For example, if the STA sends a probe request to the first AP and receives the probe response from the first AP, but the RSSI obtained according to the probe response is less than 10 dBm, the first AP meets the emergency roaming condition.

Third, after the STA sends a probe request to the first AP, it is the first moment, and then receives the probe response at the second moment, but the time interval between the first moment and the second moment is greater than the delay threshold, for example: STA The probe request is sent to the first AP at the first time, and then the probe response from the first AP is received at the second time. The time interval between the first time and the second time is 100ms, which is greater than the delay threshold of 50ms. An AP meets the emergency roaming conditions.

It is understandable that the above-mentioned emergency roaming condition determination method can be one item in the application scenario, or a combination of the above-mentioned multiple items, and the combination method can be parallel or progressive. The specific method depends on the actual situation. Depending on the scene, there is no limitation here.

407. Whether the communication quality between the STA and the second AP meets the handover condition.

In this embodiment, the handover conditions include: whether the RSSI value between the STA and the second AP is greater than the handover threshold; whether the delay between the STA and the second AP is less than the delay threshold; the specific condition determination may be The above single condition can also be a combination of multiple conditions.

It is understandable that the STA's handover object can be based on the result of scanning for non-associated APs in the above-mentioned method, that is, the handover object can be one or more non-associated APs scanned in the current cycle, or it can be scanned in multiple cycles. For example, the STA only scans the BSSIDs of the unassociated APs scanned in the current cycle.

408. The STA immediately tries to associate with the second AP.

In this embodiment, after determining an AP that meets the handover condition, the STA immediately tries to associate with the AP, and no longer enters the normal roaming procedure.

Through the above method of switching access points, the STA can promptly switch to a non-associated AP that meets the requirements when the communication status with the associated AP is not good, to ensure that the link is smooth, and the STA actively detects the link to improve data transmission. The accuracy rate effectively reduces the packet loss rate of the STA.

The following is a process description of the method provided in the embodiment of this application in conjunction with a specific scenario. As shown in Figure 5, it is a flow chart of a method for switching access points provided in the embodiment of this application. In the smart storage scenario, the AGV It is equipped with STA and needs to switch between multiple APs during operation. Due to the complex working scene of AGV and high real-time requirements, a method of switching access points that can meet this demand is needed. Description will be given below in conjunction with the drawings.

In step S1, the STA adjusts the staying time on the first channel and the scanning time on the second channel according to the beacon sending period of the associated AP. For the specific adjustment method, refer to the related description in FIG. 3, which will not be repeated here.

In step S2, the STA obtains the beacon of the associated AP through the first channel; sends a probe request to the unassociated AP through the second channel to obtain the probe response, and obtains the link status of the unassociated AP, the specific form of the probe request and the acquisition For the link situation method, refer to the related description of step 401 in FIG. 4, which is not repeated here.

In step S3, it is determined whether the beacon sent by the associated AP is lost. Specifically, the determination of the loss of the beacon can be completed based on the cooperation of the kernel state counter of the STA controller and the timer in the user state. First, the kernel state of the STA controller is enabled The counter, each time a beacon is received, the counter is increased by 1, and returns to zero when the value reaches the preset upper limit; in addition, the user mode of the STA controller starts a timer, and the working period of the timer is higher than the period of the associated AP to send the beacon. For example: if the sending period of the beacon is 50ms, the working period of the timer can be 60ms; then, the timer can check the value increase of the timer, if it is 0, it is regarded as the beacon lost.

In step S4, if it is determined in step S3 that the beacon sent by the associated AP is lost, the beacon loss in multiple working cycles within a preset time period is obtained. Specifically, it can be judged whether it is sent by the associated AP in 2 consecutive working cycles. The beacon is missing.

In step S5, the RSSI value of the current link is obtained according to the beacon sent by the associated AP, and the specific method for judging the strength of the RSSI can refer to the related description of step 402 in FIG. 4, which will not be repeated here.

In step S6, if it is determined in step S5 that the RSSI value of the beacon sent by the associated AP is weak, the RSSI value in multiple working cycles within the preset time period is obtained. Specifically, it can be determined whether it is associated with the AP in 3 consecutive working cycles. RSSI value is weak.

In step S7, if the beacon sent by the associated AP in 2 consecutive working cycles is lost, or the RSSI value is weak in 3 consecutive working cycles, the STA initiates link detection. For the specific detection method, refer to step 403 in Figure 4 Related descriptions are not repeated here.

In step S8, the STA judges the rationality of the link detection result, that is, whether the emergency roaming condition is satisfied. For the specific judgment method, refer to the related description of step 404 in FIG. 4, which will not be repeated here.

In step S9, if the result of link detection is unreasonable, the STA will roam and switch to a suitable AP. At this time, the AP selection is based on the link condition of the unassociated AP obtained through the second channel in step S2, and the specific switching is The method is similar to step 405, and will not be repeated here.

In the smart warehousing scenario, the AGV can be operated periodically according to the method described in steps S1-S9 above. It should be noted that the periodical period is less than or equal to 200ms, and can be adjusted according to the current working status or working environment. , For example: select the working cycle range of 100ms-200ms, choose this range according to the complexity of the working environment.

The embodiments of this application can be applied to the WLAN terminal according to the above method, and the WLAN terminal can be divided into functional modules. For example, each functional module can be divided corresponding to each function, or two or more functions can be integrated into one process. Module. The above-mentioned integrated modules can be implemented in the form of hardware or software functional modules. It should be noted that the division of modules in the embodiments of the present application is illustrative, and is only a logical function division, and there may be other division methods in actual implementation.

For example, in the case of dividing each functional unit in an integrated manner, as shown in FIG. 6, it is a schematic structural diagram of a WLAN terminal provided in an embodiment of the present application.

As shown in FIG. 6, the WLAN terminal 600 provided in the embodiment of the present application includes: a receiving unit 601, a sending unit 602, and an associating unit 603.

The receiving unit 601 is configured to try to receive a beacon from a first AP on a first channel, where the STA is associated with the first AP, and the first channel is a working channel of the first AP;

The sending unit 602 is configured to send a probe request on the second channel;

The receiving unit 601 is further configured to receive a probe response from the second AP on the second channel, and determine the communication quality between the STA and the second AP according to the probe response;

The sending unit 602 is further configured to, after determining the communication quality between the STA and the second AP, once the detection condition is met, immediately send a detection request on the first channel to prompt the first AP to reply Detecting a response, and determining whether an emergency roaming condition is met according to the response of the first AP, where the detecting condition includes a failure of an attempt to receive a beacon from the first AP;

The associating unit 603 is configured to immediately try to associate with the second AP if the emergency roaming condition is met and the communication quality between the STA and the second AP meets the handover condition, and the handover condition includes The strength of the communication signal between the STA and the second AP is greater than a first threshold.

Among them, all relevant content of the steps involved in the foregoing method embodiments can be cited in the functional description of the corresponding functional unit, and will not be repeated here.

The embodiment of the present application also provides a WLAN terminal, and the WLAN terminal may also be in the form of a circuit. The WLAN terminal can be used to perform the actions performed by the STA in the foregoing method embodiments.

The WLAN terminal will be described below with reference to the accompanying drawings. FIG. 7 is a schematic structural diagram of a WLAN terminal provided in an embodiment of the present application. It is easy to understand and easy to illustrate. In Fig. 7, the WLAN terminal uses AGV as an example. As shown in Figure 7, the WLAN terminal includes a processor, a memory, a radio frequency circuit, an antenna, and a WLAN interface. The processor is mainly used to process the communication protocol and communication data, and to control the WLAN terminal, execute the software program, and process the data of the software program. The memory is mainly used to store software programs and data. The radio frequency circuit is mainly used for the conversion of baseband signal and radio frequency signal and the processing of radio frequency signal. The antenna is mainly used to send and receive radio frequency signals in the form of electromagnetic waves.

When data needs to be sent, the processor performs baseband processing on the data to be sent, and then outputs the baseband signal to the radio frequency circuit. The radio frequency circuit performs radio frequency processing on the baseband signal and sends the radio frequency signal out in the form of electromagnetic waves through the antenna. When data is sent to the WLAN terminal, the radio frequency circuit receives the radio frequency signal through the antenna, converts the radio frequency signal into a baseband signal, and outputs the baseband signal to the processor, and the processor converts the baseband signal into data and processes the data. For ease of description, only one memory and processor are shown in FIG. 7. In actual WLAN terminal products, there may be one or more processors and one or more memories. The memory may also be referred to as a storage medium or storage device. The memory may be set independently of the processor, or may be integrated with the processor, which is not limited in the embodiment of the present application.

In the embodiments of the present application, the antenna and radio frequency circuit with the transceiving function can be regarded as the transceiving unit of the WLAN terminal, and the processor with the processing function can be regarded as the processing unit of the WLAN terminal. As shown in FIG. 7, the WLAN terminal includes a transceiving unit 710 and a processing unit 720. The transceiver unit may also be referred to as a transceiver, a transceiver, a transceiver, and so on. The processing unit may also be called a processor, a processing board, a processing module, and so on. Optionally, the device for implementing the receiving function in the transceiving unit 710 can be regarded as the receiving unit, and the device for implementing the sending function in the transceiving unit 710 can be regarded as the sending unit, that is, the transceiving unit 710 includes a receiving unit and a sending unit. The transceiver unit may sometimes be called a transceiver, a transceiver, or a transceiver circuit. The receiving unit may sometimes be called a receiver, receiver, or receiving circuit. The transmitting unit may sometimes be called a transmitter, a transmitter, or a transmitting circuit.

It should be understood that the transceiving unit 710 is configured to perform the sending and receiving operations on the WLAN terminal side in the foregoing method embodiment, and the processing unit 720 is configured to perform other operations on the WLAN terminal in the foregoing method embodiment except for the transceiving operation.

For example, in an implementation manner, the processing unit 702 is configured to try to control the transceiver unit 701 to receive a beacon from a first AP on a first channel through a WLAN interface, and the STA is associated with the first AP, so The first channel is the working channel of the first AP; the probe request is sent on the second channel through the WLAN interface; the probe response from the second AP is received on the second channel through the WLAN interface, and The communication quality between the STA and the second AP is determined according to the probe response; after the communication quality between the STA and the second AP is determined, once the detection conditions are met, the WLAN is immediately used The interface sends a probe request on the first channel to prompt the first AP to reply a probe response, and determines whether an emergency roaming condition is met according to the reply of the first AP, where the probe condition includes receiving from the first AP If the emergency roaming condition is met and the communication quality between the STA and the second AP satisfies the handover condition, an attempt to associate with the second AP is immediately attempted, and the handover condition includes The communication signal strength between the STA and the second AP is greater than the first threshold

When the WLAN terminal is a chip, the chip includes a transceiver unit and a processing unit. Among them, the transceiver unit may be an input/output circuit or a communication interface; the processing unit is a processor or microprocessor or integrated circuit integrated on the chip.

For the WLAN terminal in this embodiment, reference may be made to the device shown in FIG. 8. FIG. 8 is a schematic structural diagram of another WLAN terminal provided in an embodiment of the present application. As an example, the device can perform functions similar to the processor in FIG. 7. In FIG. 8, the device includes a processor 810, a data sending processor 820, and a data receiving processor 830. The associating unit 603 in the foregoing embodiment may be the processor 810 in FIG. 8 and completes corresponding functions. The receiving unit 601 or the sending unit 602 in the foregoing embodiment may be the sending data processor 820 and/or the receiving data processor 830 in FIG. 8. Although the channel encoder and the channel decoder are shown in FIG. 8, it can be understood that these modules do not constitute a restrictive description of this embodiment, and are merely illustrative.

As another form of this embodiment, a computer-readable storage medium is provided with instructions stored thereon, and when the instructions are executed, the method on the WLAN terminal side in the above method embodiment is executed.

As another form of this embodiment, a computer program product containing instructions is provided, and when the instructions are executed, the method on the WLAN terminal side in the foregoing method embodiment is executed.

It should be understood that the processor mentioned in the embodiments of the present invention may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor or the like.

It should also be understood that the memory mentioned in the embodiments of the present invention may be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. Among them, the non-volatile memory can be read-only memory (ROM), programmable read-only memory (programmable ROM, PROM), erasable programmable read-only memory (erasable PROM, EPROM), and electronic Erase programmable read-only memory (electrically EPROM, EEPROM) or flash memory. The volatile memory may be a random access memory (RAM). By way of exemplary but not restrictive description, many forms of RAM are available, such as static random access memory (static RAM, SRAM), dynamic random access memory (dynamic RAM, DRAM), synchronous dynamic random access memory (synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (double data rate SDRAM, DDR SDRAM), enhanced synchronous dynamic random access memory (enhanced SDRAM, ESDRAM), synchronous connection dynamic random access memory (synchlink DRAM, SLDRAM) ) And direct memory bus random access memory (direct rambus RAM, DR RAM).

When the processor is a general-purpose processor, DSP, ASIC, FPGA or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component, the memory (storage module) is integrated in the processor.

It should be noted that the memories described herein are intended to include, but are not limited to, these and any other suitable types of memories.

Those skilled in the art can clearly understand that, for the convenience and conciseness of description, the specific working process of the above-described system, device, and unit can refer to the corresponding process in the foregoing method embodiment, which will not be repeated here.

In the several embodiments provided in this application, it should be understood that the disclosed system, device, and method may be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division, and there may be other divisions in actual implementation, for example, multiple units or components can be combined or It can be integrated into another system, or some features can be ignored or not implemented. In addition, the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or units, and may be in electrical or other similar forms.

The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

In addition, the functional units in each embodiment of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units may be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or software functional unit.

If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on this understanding, the technical solution of this application essentially or the part that contributes to the existing technology or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium , Including several instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage media include: U disk, mobile hard disk, read only memory (ROM), random access memory (RAM), magnetic disk or optical disk and other media that can store program codes.

As mentioned above, the above embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, a person of ordinary skill in the art should understand that: The technical solutions recorded in the embodiments are modified, or some of the technical features thereof are equivalently replaced; these modifications or replacements do not cause the corresponding technical solutions to deviate from the technical solutions and scope of the embodiments of the present application.

Those of ordinary skill in the art can understand that all or part of the steps in the foregoing embodiments can be implemented by hardware, or by a program instructing relevant hardware to be completed. The program can be stored in a computer-readable storage medium. The storage medium mentioned can be a read-only memory, a magnetic disk or an optical disk, etc.

Claims

A method for switching an access point (AP) in a wireless local area network (WLAN), which is characterized in that it includes:

A station (STA) tries to receive a beacon from a first AP on a first channel, the STA is associated with the first AP, and the first channel is the working channel of the first AP;

The STA sends a probe request on the second channel;

Receiving, by the STA, a probe response from the second AP on the second channel, and determining the communication quality between the STA and the second AP according to the probe response;

After determining the communication quality between the STA and the second AP, once the detection conditions are met, the STA immediately sends a probe request on the first channel to prompt the first AP to reply with a probe response, and according to the The response of the first AP determines whether an emergency roaming condition is met, where the detection condition includes a failure to receive a beacon from the first AP;

If the emergency roaming condition is met and the communication quality between the STA and the second AP meets the handover condition, the STA immediately tries to associate with the second AP, and the handover condition includes the STA The strength of the communication signal with the second AP is greater than the first threshold.
The method according to claim 1, wherein the detection condition further comprises that the signal strength of the most recently received beacon from the first AP is less than a second threshold.
The method according to claim 1 or 2, wherein the single stay duration of the STA on the first channel is the first duration, and the single stay duration of the STA on the second channel is the first Two durations, the sum of the first duration and the second duration does not exceed 200 milliseconds.
The method according to claim 3, wherein the beacon interval of the first AP is a third duration, the third duration is less than or equal to 50 milliseconds, the first duration is greater than the third duration, so The second duration is less than the third duration.
The method according to claim 4, wherein the STA dynamically adjusts the first duration, wherein if the STA has service on the first channel, the first duration is between 100 milliseconds and 200 Between milliseconds; if the STA has no service on the first channel, the first duration is between 50 milliseconds and 100 milliseconds.
The method according to any one of claims 1 to 5, wherein the emergency roaming condition includes the time when the probe response from the first AP is received and the time when the STA sends the probe on the first channel. The delay between probe requests is greater than the third threshold.
A wireless local area network (WLAN) terminal, the characteristics of which include:

A receiving unit, configured to try to receive a beacon from a first access point (AP) on a first channel, the WLAN terminal is associated with the first AP, and the first channel is the work of the first AP channel;

A sending unit, configured to send a probe request on the second channel;

The receiving unit is further configured to receive a probe response returned by the second AP on the second channel, and determine the communication quality between the WLAN terminal and the second AP according to the probe response;

The sending unit is further configured to, after determining the communication quality between the WLAN terminal and the second AP, once the detection condition is met, immediately send a detection request on the first channel to prompt the first AP to reply Detecting a response, and determining whether an emergency roaming condition is satisfied according to the response of the first AP, where the detecting condition includes an attempt to receive a beacon from the first AP failed;

An association unit, configured to immediately try to associate with the second AP if the emergency roaming condition is met and the communication quality between the WLAN terminal and the second AP meets the handover condition, and the handover condition includes The strength of the communication signal between the WLAN terminal and the second AP is greater than a first threshold.
A wireless local area network (WLAN) terminal, which is characterized by comprising:

Processor and WLAN interface;

The processor is used for:

Try to receive a beacon from a first access point (AP) on a first channel through the WLAN interface, the WLAN terminal is associated with the first AP, and the first channel is the work of the first AP channel;

Sending a probe request on the second channel through the WLAN interface;

Receiving a probe response from a second AP on the second channel through the WLAN interface, and determining the communication quality between the WLAN terminal and the second AP according to the probe response;

After determining the communication quality between the WLAN terminal and the second AP, once the detection conditions are met, immediately send a probe request on the first channel through the WLAN interface to prompt the first AP to reply with a probe response, And determining whether an emergency roaming condition is met according to the response of the first AP, where the detection condition includes a failure of an attempt to receive a beacon from the first AP;

If the emergency roaming condition is met and the communication quality between the WLAN terminal and the second AP meets the handover condition, it will immediately try to associate with the second AP. The handover condition includes the STA and the The strength of the communication signal between the second APs is greater than the first threshold.
A computer program product containing instructions, when the computer program product runs on a computer,

The computer executes the method according to any one of claims 1 to 6.