Method and apparatus for handling timing synchronization function synchronization in multiple access point system

Abstract

A timing synchronization function (TSF) synchronization method includes: generating a first TSF information frame, where the first TSF information frame includes first TSF synchronization data, and the first TSF synchronization data includes TSF information of a first access point (AP) of a multi-access point (multi-AP, MAP) system, and generating a second TSF information frame, where the first TSF information frame includes first TSF synchronization data, and the first TSF synchronization data includes TSF information of the first access point (AP) of the multi-AP, MAP system. And transmitting the first TSF synchronization frame to a second AP of the MAP system.

Description

TECHNICAL FIELD

[0001] The present application relates to wireless communications, and more particularly, to a method and apparatus for handling timing synchronization function (TSF) synchronization in a multi-access-point (MAP) system.

BACKGROUND

[0002] In a MAP system, there are multiple access points (APs) (e.g., AP multi-link devices (MLDs)) that cooperate to serve non-AP stations (STAs) (e.g., non-AP MLDs). For many applications, these APs need to coordinate transmit and receive behavior in order to mitigate interference between the APs. However, since these APs can not be physically co-located, their clocks can drift over time. Therefore, there is a need for an innovative timing synchronization design that can synchronize the TSF timers of these APs that operate on the same operating channel or in the same MAP system.

SUMMARY

[0003] It is an object of the present application to provide a method and apparatus for handling timing synchronization function (TSF) synchronization in a multi-AP (MAP) system.

[0004] According to a first aspect of the present application, an example TSF synchronization method is disclosed. The example TSF synchronization method includes generating a first TSF information frame, wherein the first TSF information frame includes first TSF synchronization data, and the first TSF synchronization data includes TSF information of a first access point (AP) of a MAP system; and transmitting the first TSF synchronization frame to a second AP of the MAP system.

[0005] According to a second aspect of the present application, an example TSF synchronization method is disclosed. The example TSF synchronization method includes receiving a TSF information frame, wherein the TSF information frame includes TSF synchronization data, and the TSF synchronization data includes TSF information of a first AP of a MAP system; and performing TSF synchronization of a second AP of the MAP system according to the first TSF synchronization data.

[0006] According to a third aspect of the present invention, an exemplary access point (AP) for a MAP system is disclosed. The exemplary AP includes a network interface circuit and a control circuit. The control circuit is configured to generate a TSF information frame and instruct the network interface circuit to send the TSF information frame to another AP in the MAP system, wherein the TSF information frame includes TSF synchronization data, and the TSF synchronization data includes the AP's TSF information.

[0007] These, and other objectives of the invention, will undoubtedly become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments illustrated in conjunction with various figures and drawings. [Attached Image Description]

[0008] Figure 1 This is a schematic diagram illustrating a MAP system that supports the proposed TSF synchronization scheme according to an embodiment of the present invention.

[0009] Figure 2 This is a schematic diagram illustrating a first TSF synchronization scenario in a MAP system according to an embodiment of the present invention.

[0010] Figure 3 This is a schematic diagram illustrating another MAP system that supports the proposed TSF synchronization scheme according to an embodiment of the present invention.

[0011] Figure 4 This is a schematic diagram illustrating a second TSF synchronization scenario in a MAP system according to an embodiment of the present invention.

Detailed Implementation Methods

[0012] Certain terms are used in the following description and claims to refer to specific components. As those skilled in the art will understand, electronics manufacturers may use different names to refer to a component. This document is not intended to distinguish between components with different names but the same function. In the following description and claims, the terms "comprising" and "including" are used in an open-ended manner and should therefore be interpreted as "including, but not limited to...". Furthermore, the term "connection" is intended to indicate an indirect or direct electrical connection. Thus, if one device is connected to another device, the connection can be a direct electrical connection or an indirect electrical connection via other devices and connections.

[0013] Figure 1This is a schematic diagram illustrating a MAP system supporting the proposed TSF synchronization scheme according to an embodiment of the present invention. MAP system 100 can be a Wi-Fi system conforming to the IEEE 802.11bn (Wi-Fi 8) standard or a next-generation Wi-Fi standard. MAP system 100 includes multiple APs 102, 104_1-104_N (N≥1). For example, AP 102 can act as the master AP initiating TSF synchronization of MAP system 100, and each AP 104_1-104_N can act as a non-master AP that needs to synchronize with the master AP.

[0014] It should be noted that the APs in the MAP system 100 can be AP MLDs with multiple links operating on different RF bands and capable of operating simultaneously, or they can be non-MLD APs. Therefore, the MAP system 100 supporting the proposed TSF synchronization scheme can be formed by multiple AP MLDs, multiple non-MLD APs, or a combination thereof.

[0015] AP 102,104_1-104_N may have the same or similar circuit structures. For example... Figure 1 As shown, AP 102 / 104_1 / 104_N includes a processor 112 / 122_1 / 122_N, a memory 114 / 124_1 / 124_N, control circuitry 116 / 126_1 / 126_N, and network interface circuitry 117 / 127_1 / 127_N. The network interface circuitry 117 / 127_1 / 127_N includes transmitter (TX) circuitry 118 / 128_1 / 128_N and receiver (RX) circuitry 120 / 130_1 / 130_N. The memory 114 / 124_1 / 124_N is used to store program code. The processor 112 / 122_1 / 122_N is used to load and execute program code to manage AP 102 / 104_1 / 104_N. Control circuit 116 / 126_1 / 126_N is used to control communication with non-AP STAs and other APs. For example, control circuit 116 / 126_1 / 126_N controls the TX circuit 118 / 128_1 / 128_N of network interface circuit 117 / 127_1 / 127_N to send frames to non-AP STAs and other APs, and controls the RX circuit 120 / 122_1 / 122_N of network interface circuit 117 / 127_1 / 127_N to receive frames from non-AP STAs and other APs.

[0016] It is important to note that Figure 1 Only the components relevant to this invention are shown. In practical applications, each AP 102,104_1-104_N may include additional components to achieve the specified functionality.

[0017] APs 102, 104_1-104_N in the same MAP system 100 support the proposed TSF synchronization scheme. The control circuit 116 of AP 102 (as the master AP) maintains a TSF timer (e.g., a 64-bit counter) 122. The control circuit 126_1 of AP 104_1 (as a non-master AP) maintains a TSF timer (e.g., a 64-bit counter) 132_1. The control circuit 126_N of AP 104_N (as a non-master AP) maintains a TSF timer (e.g., a 64-bit counter) 132_N. The local clocks of APs 102, 104_1-104_N may drift over time. Therefore, the values ​​of the TSF timers 122, 132_1, and 132_N maintained by different APs 102, 104_1-104_N in the same MAP system 100 may be out of sync. To address this issue, this invention proposes a TSF synchronization scheme that synchronizes the TSF timers of non-master APs with the TSF timers of master APs.

[0018] In this embodiment, it is assumed that there is a backhaul between APs 102, 104_1-104_N in the same MAP system 100, and any AP 102, 104_1-104_N can communicate with other APs through the backhaul, which can be wired or wireless. However, this is for illustrative purposes only and is not intended to limit the invention. In practical applications, any means that enables one AP to communicate with another can be used.

[0019] Since AP 102 acts as the primary AP, it is responsible for periodically initiating TSF synchronization of the MAP system 100 to ensure accurate time synchronization among APs 102, 104_1-104_N within the same MAP system 100. In this embodiment, it is also assumed that APs 104_1-104_N can directly listen to AP 102. Figure 2 This is a schematic diagram illustrating the first TSF synchronization scenario in a MAP system according to an embodiment of the present invention. The primary AP AP1 can be implemented by AP 102, and the non-primary APs AP2 and AP3 can be implemented by two of APs 104_1-104_N, wherein each non-primary AP AP2 and AP3 can directly listen to the primary AP AP1.

[0020] The control circuit 116 of AP 102 is configured to generate a TSF information frame F_TSF1 and instruct the network interface circuit 117 (specifically, the TX circuit 118 of the network interface circuit 117) to send the TSF information frame F_TSF1 to APs 104_1-104_N. For example, the TSF information frame F_TSF1 can be a broadcast frame, which can be broadcast to multiple non-primary APs in MAP system 100. As another implementation, the TSF information frame F_TSF1 can be a unicast frame, which can be unicast to a single non-primary AP in MAP system 100, and the control circuit 116 of AP 102 needs to generate and send multiple TSF information frames F_TSF1 to multiple non-primary APs in MAP system 100 respectively.

[0021] The TSF information frame F_TSF1 is used to carry TSF synchronization data. For example, the TSF synchronization data may include the TSF timing of AP 102 (e.g., the value counted by TSF timer 122 when the transmission of TSF information frame F_TSF1 occurs / begins), a time offset corresponding to the delay caused by the processing and transmission of TSF information frame F_TSF1, an incremental update identifier ID indicating a TSF synchronization revision, or a combination thereof. The TSF information frame F_TSF1 can be a beacon frame or any frame capable of carrying the information required for TSF synchronization.

[0022] AP 104_1 (as a non-master AP) receives TSF information frame F_TSF1 from network interface circuit 117 (specifically, TX circuit 118) of AP 102 (as the master AP), via network interface circuit 127_1 (specifically, RX circuit 130_1). AP 104_1's control circuit 126_1 also acquires TSF information frame F_TSF1 from network interface circuit 127_1 (specifically, RX circuit 130_1). AP 104_1's control circuit 126_1 can check the incremental update ID carried by TSF information frame F_TSF1 to determine whether to adjust TSF timer 132_2. When the incremental update ID indicates that TSF synchronization of AP 104_1 is required, the control circuit 126_1 of AP 104_1 adjusts the TSF timer 132_2 to synchronize with AP 102 by referring to the TSF timing and time offset indicated in the TSF information frame F_TSF1. For example, the current count value of TSF timer 132_2 is updated to be equal to the TSF timing plus the time offset. In this way, after TSF synchronization of AP 104_1 is performed based on the TSF synchronization data carried in the TSF information frame F_TSF1, TSF timers 122 and 132_2 have the same value.

[0023] Similarly, the network interface circuit 127_N of AP 104_N (as a non-master AP) (specifically, the RX circuit 130_N of network interface circuit 127_N) also receives the same TSF information frame F_TSF1 sent from the network interface circuit 117 of AP 102 (as the master AP) (specifically, the TX circuit 118 of network interface circuit 117), and the control circuit 126_N of AP 104_N obtains the TSF information frame F_TSF1 from the network interface circuit 127_N (specifically, the RX circuit 130_N of network interface circuit 127_N). The control circuit 126_N of AP 104_N can check the incremental update ID carried by the TSF information frame F_TSF1 to determine whether to adjust the TSF timer 132_N. When the incremental update ID indicates that TSF synchronization of AP 104_N is required, the control circuit 126_N of AP 104_N adjusts the TSF timer 132_N to synchronize with AP 102 by referring to the TSF timing and time offset indicated in the TSF information frame F_TSF1. For example, the current count value of TSF timer 132_N is updated to be equal to the TSF timing plus the time offset. In this way, after TSF synchronization of AP 104_N is performed based on the TSF synchronization data carried in the TSF information frame F_TSF1, TSF timers 122 and 132_N have the same value.

[0024] After TSF synchronization of APs 104_1-104_N is completed, all TSF timers 122 and 132_1-132_N of different APs 102, 104_1-104_N in the same MAP system 100 are synchronized. When the beacon interval is the same, the target beacon transmission time (TBTT) of the beacon frames of each AP may be the same. In some embodiments of the invention, another "beacon transmission time offset" parameter broadcast by each AP in the frame (e.g., the beacon frame itself) can be used to indicate the beacon transmission time offset with the TBTT, so that the beacon frames broadcast by APs 102, 104_1-104_N do not collide at the same time.

[0025] Figure 3This is a schematic diagram illustrating another MAP system supporting the proposed TSF synchronization scheme according to an embodiment of the present invention. MAP system 300 can be a Wi-Fi system conforming to the IEEE 802.11bn (Wi-Fi 8) standard or a next-generation Wi-Fi standard. MAP system 300 includes multiple APs 102, 304_1-304_N (N≥1). For example, AP 102 can act as the master AP initiating TSF synchronization of MAP system 300, while each AP 304_1-304_N can act as a non-master AP requiring synchronization with the master AP. It should be noted that MAP system 300 supporting the proposed TSF synchronization scheme can be formed by multiple AP MLDs, multiple non-MLDAPs, or combinations thereof.

[0026] APs 102, 304_1-304_N may have the same or similar circuit structures. The main difference between MAP systems 100 and 300 is that some or all APs 304_1-304_N further support relay functionality, used to relay TSF information frames to one or more non-primary APs that cannot directly listen to the primary AP. It is important to note that... Figure 3 Only the components relevant to this invention are shown. In practical applications, each AP 102,304_1-304_N may include additional components to achieve the specified functionality.

[0027] APs 102, 304_1-304_N in the same MAP system 300 support the proposed TSF synchronization scheme. The control circuit 116 of AP 102 (as the master AP) maintains a TSF timer 122 (e.g., a 64-bit counter). The control circuit 326_1 of AP 304_1 (as a non-master AP) maintains a TSF timer 332_1 (e.g., a 64-bit counter). The control circuit 326_N of AP 304_N (as a non-master AP) maintains a TSF timer 332_N (e.g., a 64-bit counter). The local clocks of APs 102, 304_1-304_N may drift over time. Therefore, the values ​​of the TSF timers 122, 332_1, and 332_N maintained by different APs 102, 304_1-304_N in the same MAP system 300 may be out of sync. To address this issue, this invention proposes a TSF synchronization scheme that synchronizes the TSF timers of non-master APs with the TSF timers of master APs.

[0028] In this embodiment, it is assumed that an AP can listen to another AP through at least one frequency band it operates on or through backhaul, and one or more non-primary APs may not be able to directly listen to the primary AP. Figure 4This is a schematic diagram illustrating a second TSF synchronization scenario in a MAP system according to an embodiment of the present invention. The primary AP AP1 can be implemented by AP 102, and the non-primary APs AP2, AP3, AP4, and AP5 can be implemented by four of APs 304_1-304_N. Each non-primary AP AP2 and AP3 can directly listen to the primary AP AP1, while each non-primary AP AP4 and AP5 cannot directly listen to the primary AP AP1. Non-primary AP AP4 is a neighbor AP of non-primary AP AP3, and non-primary AP AP5 is a neighbor AP of non-primary AP AP4.

[0029] As the primary AP, AP 102 is responsible for periodically initiating TSF synchronization within the MAP system 300 to ensure accurate time synchronization among APs 102, 304_1-304_N within the same MAP system 300. The control circuit 116 of AP 102 is configured to generate a TSF information frame F_TSF1 and instruct the network interface circuit 117 (specifically, the TX circuit 118 of the network interface circuit 117) to send the TSF information frame F_TSF1 to non-primary APs that can directly listen to the primary AP. For example, AP 304_1 can directly listen to AP 102, while AP 304_N cannot. The TSF information frame F_TSF1 can be a broadcast frame, broadcast to multiple non-primary APs in the MAP system 300. In another embodiment, the TSF information frame F_TSF1 can be a unicast frame that can be unicast to a single non-primary AP in the MAP system 300, and the control circuit 116 of AP 102 needs to generate and send multiple TSF information frames F_TSF1 to multiple non-primary APs in the MAP system 300 respectively.

[0030] TSF information frame F_TSF1 is used to carry TSF synchronization data. For example, TSF synchronization data may include the TSF time of AP 102 (e.g., the value counted by TSF timer 122 when TSF information frame F_TSF1 transmission occurs / starts), a time offset corresponding to the delay caused by the processing and transmission of TSF information frame F_TSF1, an incremental update ID indicating TSF synchronization revision, or a combination thereof.

[0031] The network interface circuit 127_1 (particularly the RX circuit 130_1 of the network interface circuit 127_1) receives the TSF information frame F_TSF1 sent from the network interface circuit 117 (particularly the TX circuit 118 of the network interface circuit 117) of the access point AP 304_1 (as a non-master AP), and the control circuit 326_1 of the access point AP 304_1 obtains the TSF information frame F_TSF1 from the network interface circuit 127_1 (particularly the RX circuit 130_1 of the network interface circuit 127_1). The control circuit 326_1 of the access point AP 304_1 can check the incremental update ID carried by the TSF information frame F_TSF1 to determine whether to adjust the TSF timer 332_2. When the incremental update ID indicates that TSF synchronization revision requires TSF synchronization for access point AP 304_1, the control circuit 326_1 of access point AP 304_1 adjusts TSF timer 332_1 to synchronize with access point AP 102, referencing the TSF timing and time offset indicated by TSF information frame F_TSF1. For example, the current value of the count of TSF timer 332_1 is updated to be equal to the TSF timing plus the time offset. In this way, after TSF synchronization of access point AP 304_1 is performed based on the TSF synchronization data carried by TSF information frame F_TSF1, both TSF timers 122 and 332_1 have the same value.

[0032] In this embodiment, access point AP 304_N cannot directly listen to access point AP 102 and register as a neighboring AP of access point AP 304_1. Access point AP 304_1 enables relay functionality to provide relayed TSF information frames to access point AP 304_N for TSF synchronization. For example, the control circuit 326_1 of access point AP 304_1 is configured to generate TSF information frame F_TSF2 and instruct network interface circuit 127_1 (specifically, the TX circuit 128_1 of network interface circuit 127_1) to send TSF information frame F_TSF2 to its neighboring AP, including access point AP 304_N.

[0033] Similar to TSF information frame F_TSF1, TSF information frame F_TSF2 can be a broadcast or unicast frame and is used to carry TSF synchronization data. For example, the TSF synchronization data may include the TSF timing of access point AP 304_1 (e.g., the value counted by TSF timer 332_1 when TSF information frame F_TSF2 occurs / begins transmission), a time offset corresponding to the relay delay caused by processing and transmitting TSF information frame F_TSF2, an incremental update ID indicating TSF synchronization revision, or a combination thereof. Since TSF timer 332_1 of access point AP 304_1 is synchronized with TSF timer 122 of access point AP 102, the TSF timing of access point AP 304_1 indicated by TSF information frame F_TSF2 is the same as the TSF timing of access point AP 102. Therefore, TSF information frame F_TSF2 can be considered a relay TSF information frame carrying the TSF timing of access point AP 102. In addition, the incremental update ID indicated by the relay TSF information frame (i.e., TSF information frame F_TSF2) needs to be the same as the incremental update ID indicated by the TSF information frame F_TSF1.

[0034] The network interface circuit 127_N of access point AP 304_N (particularly the RX circuit 130_N of network interface circuit 127_N) receives a relay TSF information frame (i.e., TSF information frame F_TSF2) sent from the network interface circuit 127_1 of access point AP 304_1 (particularly the TX circuit 128_1 of network interface circuit 127_N), and the control circuit 326_N of access point AP 304_N acquires the relay TSF information frame (i.e., TSF information frame F_TSF2) from the network interface circuit 127_N (particularly the RX circuit 130_N of network interface circuit 127_N). The control circuit 326_N of access point AP 304_N can check the incremental update ID carried by the relay TSF information frame (i.e., TSF information frame F_TSF2) to determine whether to adjust the TSF timer 332_N. When the incremental update ID indicates that TSF synchronization revision requires TSF synchronization for access point AP 304_N, the control circuit 326_N of access point AP 304_N adjusts the TSF timer 332_N to synchronize with access point AP 102 by referring to the TSF timing and time offset carried by the trunk TSF information frame (i.e., TSF information frame F_TSF2). For example, the current value of the count of TSF timer 332_N is updated to be equal to the TSF timing plus the time offset. In this way, after performing TSF synchronization of access point AP 304_N based on the TSF synchronization data carried by the trunk TSF information frame (i.e., TSF information frame F_TSF2), both TSF timers 122 and 332_N have the same value.

[0035] likeFigure 4 As shown, non-primary AP AP4 cannot directly listen to primary AP AP1 and register as a neighbor AP of non-primary AP AP3. Assume primary AP AP1 is implemented by access point AP 102, non-primary AP AP3 by access point AP 304_1, and non-primary AP AP4 by access point AP 304_N. Therefore, with the help of relay TSF information frames (i.e., TSF information frame F_TSF2) unicast / broadcast from non-primary AP AP3, the TSF timing of non-primary AP AP4 can be synchronized with the TSF timing of non-primary AP AP3.

[0036] like Figure 4 As shown, non-primary AP AP5 cannot directly listen to primary AP AP1 and register as a neighbor AP of non-primary AP AP4. Assume non-primary AP AP5 is implemented by AP 304_i (i≠1 &i≠N). Similar to AP 304_1, AP 304_N can enable the same relay function to generate relay TSF information frames, and after TSF timer 332_N is synchronized with TSF timers 122 and 332_1, the relay TSF information frame is sent to AP 304_i. Similarly, the update ID indicated by the relay TSF information frame generated by AP 304_i needs to be the same as the update ID indicated by TSF information frame F_TSF1. Since the relay function performed by AP 304_i is the same as that performed by AP 304_N, further description is omitted here for brevity.

[0037] In some embodiments of the present invention, when a non-primary AP (which cannot directly listen to the primary AP) registers as a neighboring AP of multiple non-primary APs, updating the ID can also avoid repeatedly receiving relayed TSF information frames (corresponding to TSF information frames sent from the primary AP).

[0038] As described above, the primary AP is responsible for periodically initiating TSF synchronization of the MAP system. However, due to various reasons, the primary AP may be unable to provide TSF information frames (which could be a beacon frame or any frame that can carry the information required for TSF synchronization). In some cases, the primary AP may be unavailable for a known time. For example, the primary AP may need to be shut down for maintenance or other technical reasons, and the MAP system can anticipate the time when the primary AP goes offline. In other cases, the primary AP may be unavailable for an unknown time. For example, the primary AP may experience a sudden power outage, or the backhaul connection with the primary AP may be interrupted. To maintain TSF synchronization in the MAP system when the primary AP is unavailable, this invention further proposes several error handling designs, including a first error handling design and a second error handling design. The first error handling design can be used to select a new primary AP when the current primary AP is unavailable for an unknown time (e.g., the current primary AP is unexpectedly offline for a period of time or loses several TSF information frames), and can also be used to select a new primary AP when the current primary AP is unavailable for a known time (e.g., the current primary AP knows it will go offline at a predetermined time). The second error handling design can be used to select a new primary AP when the current primary AP is known to be unavailable for a known time (e.g., the current primary AP knows it will go offline at a scheduled time).

[0039] According to the first error handling design, a ranking method is used to assign a unique level to each AP during MAP system setup. For example, the primary AP is assigned level 1, non-primary APs are assigned levels 2, 3, and so on. Thus, when the primary AP goes offline, each online AP in the MAP system is assigned a unique level. When the current primary AP initiating MAP system TSF synchronization goes offline, the online AP with the highest level (e.g., level 2) is selected from all online APs in the MAP system as the new primary AP. After the selected online AP takes over the primary AP role, its level setting is updated to level 1. Furthermore, after the selected online AP takes over the primary AP role, the level settings of other online APs in the same MAP system may be adjusted. For example, the levels of other APs may increase by 1 accordingly.

[0040] For new APs joining the MAP system after initial setup, they are assigned a unique rank, different from the rank 1 held by the primary AP. The ranks of other APs may change depending on the rank assigned to the new AP. For example, if a new AP is assigned rank 2, an AP that was originally ranked 2 might be reassigned to a new rank other than rank 2. The same rules apply when the original primary AP rejoins the MAP system after becoming unavailable.

[0041] According to the second error handling design, before the current primary AP initiating TSF synchronization of the MAP system is expected to go offline at a predetermined time, the current primary AP sends a broadcast frame to other APs (i.e., non-primary APs) in the MAP system. The broadcast frame is configured to indicate which non-primary AP is appointed as the new primary AP to take over the primary AP role and periodically initiate TSF synchronization of the MAP system after the current primary AP goes offline. In some embodiments of the invention, the broadcast frame is further configured to indicate the predetermined time for the current primary AP to go offline. In some embodiments of the invention, the broadcast frame is further configured to indicate the functions provided by the new primary AP. In addition to TSF synchronization functionality, the new primary AP may provide additional functions required by the MAP system. Furthermore, some existing functions supported by the current primary AP may not be provided by the new primary AP. That is, some functions not required by the MAP system may cease when the new primary AP comes online.

[0042] Those skilled in the art will readily observe that numerous modifications and alterations can be made to the apparatus and method while retaining the teachings of the invention. Therefore, the foregoing disclosure should be interpreted only within the scope and limits of the appended claims.

Claims

1. A timed synchronization function (TSF) synchronization method, comprising: Generate a first TSF information frame, wherein the first TSF information frame includes first TSF synchronization data, and the first TSF synchronization data includes TSF information of a first access point (AP) in a multi-access point (MAP) system; and The first TSF synchronization frame is sent to the second AP of the MAP system.

2. The TSF synchronization method as described in claim 1, wherein the first TSF information frame is generated and sent by the first AP, which is the master AP that initiates the TSF synchronization of the MAP system, and the second AP is a non-master AP.

3. The TSF synchronization method as described in claim 2, wherein the first TSF information frame is periodically generated and sent by the master AP.

4. The TSF synchronization method as described in claim 2, wherein the first TSF synchronization data further includes a time offset corresponding to the delay caused by the processing and transmission of the first TSF information frame.

5. The TSF synchronization method as claimed in claim 2, wherein the first TSF synchronization data further includes an update identifier (ID) indicating a TSF synchronization revision.

6. The TSF synchronization method as claimed in claim 1, wherein the first TSF information frame is generated and sent by the first AP, and each of the first AP and the second AP is a non-primary AP different from the primary AP that initiated the TSF synchronization of the MAP system.

7. The TSF synchronization method as described in claim 6, further comprising: The second TSF information frame is received from the third AP of the MAP system, wherein the second TSF information frame includes second TSF synchronization data, and the second TSF synchronization data includes the TSF information of the third AP; The TSF synchronization of the first AP is based at least in part on the TSF information of the third AP.

8. The TSF synchronization method as described in claim 7, wherein the third AP serves as the master AP.

9. The TSF synchronization method as described in claim 7, wherein the third AP is a non-primary AP.

10. The TSF synchronization method of claim 6, wherein the first TSF synchronization data further includes a time offset corresponding to the delay caused by the processing and transmission of the first TSF information frame.

11. The TSF synchronization method of claim 6, wherein the first TSF synchronization data further includes an update identifier (ID) indicating a TSF synchronization revision, and the update ID carried by the first TSF information frame is equal to the update ID carried by the second TSF information frame.

12. The TSF synchronization method as described in claim 1, wherein the first TSF information frame is a broadcast frame.

13. The TSF synchronization method as described in claim 1, wherein the first TSF information frame is a unicast frame.

14. The TSF synchronization method of claim 1, wherein each online AP in the MAP system is assigned a unique level; and the TSF synchronization method further comprises: In response to the current primary AP going offline when it initiates TSF synchronization of the MAP system, the online AP with the highest level is selected from all online APs in the MAP system as the new primary AP.

15. The TSF synchronization method as described in claim 1, wherein the TSF synchronization method further comprises: Before the current primary AP that initiates TSF synchronization of the MAP system is expected to go offline at a predetermined time, it sends a broadcast frame to the non-primary APs in the MAP system. The broadcast frame is set to indicate which non-primary AP is appointed as the new primary AP to take over the TSF synchronization of the MAP system after the current primary AP goes offline.

16. The TSF synchronization method of claim 15, wherein the broadcast frame is further configured to indicate a predetermined time for the current primary AP to go offline, or a function provided by the new primary AP.

17. A timed synchronization function (TSF) synchronization method, comprising: Receive a TSF information frame, wherein the TSF information frame includes TSF synchronization data, and the TSF synchronization data includes TSF information of the first access point (AP) of the multi-access point (MAP) system; and The second AP of the MAP system is synchronized with the first TSF synchronization data.

18. The TSF synchronization method as described in claim 17, wherein the first AP is the master AP that initiates the TSF synchronization of the MAP system, and the second AP is a non-master AP.

19. The TSF synchronization method of claim 17, wherein each of the first AP and the second AP is a non-primary AP different from the primary AP that initiated the TSF synchronization of the MAP system.

20. An access point (AP) of a multi-access point (MAP) system, comprising: Network interface circuit; as well as The control circuit arranges the generation of TSF information frames and instructs the network interface circuit to send the TSF information frames to another AP in the MAP system; The TSF information frame includes TSF synchronization data, and the TSF synchronization data includes the TSF information of the AP.

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