A seamless roaming method and system based on multi-node redundancy cooperation

Abstract

The present application relates to the technical field of industrial wireless communication, and in particular to a seamless roaming method and system based on multi-node redundancy cooperation, which comprises the following steps: a field device sends a MAC frame to a neighboring access device, the neighboring access device extracts RSSI, and when the RSSI reaches a threshold, an access controller sends a countdown mark to a current access device; when the countdown counter decreases to 0, the access controller sends downlink data to the current access device and the neighboring access device respectively, and sends the processed downlink data to the field device in different resource units; the field device determines the data type according to the processed downlink data, if the data type is homogeneous service, the field device sends uplink data to the current access device and the neighboring access device through full-bandwidth broadcast, and if the data type is heterogeneous service, the field device sends different control interaction frames to the current access device and the neighboring access device by using resource units. The present application can realize high-reliability redundancy.

Description

Technical Field

[0001] This invention relates to the field of industrial wireless communication technology, specifically to a seamless roaming method and system based on multi-node redundant collaboration. Background Technology

[0002] In modern industrial wireless networks, deterministic latency and absolute reliability are key indicators for ensuring the stable operation of industrial automation equipment. Typical application scenarios, such as the scheduling of intelligent AGVs (Automated Guided Vehicles) in warehousing and the high-frequency collaborative control of robotic arms, place stringent technical requirements on the underlying communication links. Currently, industrial wireless networks mainly employ two underlying access mechanisms: a random backoff architecture based on CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) and a time-slot scheduling architecture based on TDMA (Time Division Multiple Access). While these two architectures meet the basic communication needs of industrial scenarios to a certain extent, significant technical bottlenecks remain when dealing with the handover (roaming) problem of mobile nodes in different areas.

[0003] Existing industrial wireless networks face two main technical drawbacks when mobile nodes hand over data across areas: First, when a field device (FD) is in the handover zone between two access devices (AD), the signal strength of the original communication link is critical due to the complex electromagnetic environment of the factory. This makes it highly susceptible to severe signal fading due to metal obstacles, leading to sudden packet loss and communication interruptions. Second, traditional networks use either a disconnect-then-reconnect mechanism or a complex soft roaming state mechanism for handover across areas. This handover method inevitably creates a communication vacuum period of tens to hundreds of milliseconds, causing critical control commands to fail at the moment of handover. Although existing technologies such as Wi-Fi's (Wireless Fidelity) C-OFDMA (Cooperative Orthogonal Frequency Division Multiple Access) evolution have introduced the concept of a multi-node cooperative resource unit (RU), their design focuses on improving multi-user concurrent capacity and lacks a high-precision time-frequency alignment mechanism for a single mobile node in the handover zone scenario. Therefore, they cannot achieve the function of two access devices providing concurrent redundant services to a single mobile node. Summary of the Invention

[0004] To address the aforementioned technical issues of unstable communication, packet loss, and connection interruptions experienced by mobile terminals in the handover zone between two A / D nodes, this invention provides a seamless roaming method and system based on multi-node redundancy collaboration. This invention primarily builds upon a preceding absolute time-frequency synchronization network by sensing the location status of the FD (Dedicated Function), utilizing the redundancy countdown of the main link to predict FD allocation of reception resources. When the FD is between two A / D nodes, the downlink utilizes the two A / D nodes to transmit redundant data on different RUs (Receiving Units). The uplink introduces an adaptive mechanism, supporting the FD to dynamically select full-bandwidth macro diversity transmission or multi-RU orthogonal transmission based on the transmission content (service data or link interaction frames), thereby providing simplified, bidirectional redundancy protection and smooth handover transition for terminals in the handover zone.

[0005] The technical means employed in this invention are as follows: A seamless roaming method based on multi-node redundancy collaboration includes the following steps: The field device simultaneously sends MAC frames to the current access device and the neighboring access device. The neighboring access device extracts the RSSI. When the RSSI reaches a threshold, the neighboring access device sends the RSSI and the address of the field device to the access controller. When the access controller determines that the field device has entered the junction area between the current access device and the neighboring access device, the access controller sends a countdown flag to the current access device, the countdown flag including a decrementing counter; When the decrementing counter drops to 0, the access controller sends downlink data to the current access device and the neighboring access device respectively. The current access device and the neighboring access device send the processed downlink data to the field device in different resource units. The field device determines the data type based on the processed downlink data. If the data type is homogeneous, the field device sends uplink data to the current access device and the neighboring access device through full bandwidth broadcast. If the data type is heterogeneous, the field device uses resource units to send different control interaction frames to the current access device and the neighboring access device.

[0006] Furthermore, the access controller sends a countdown marker to the currently accessed device, including: Each time the access controller sends a countdown flag to the currently accessed device, the value of the next decrement counter will decrease sequentially, with the initial value of the decrement counter being greater than or equal to 3; The current access device sends a control frame to the field device. The control frame includes a countdown marker. The field device calculates the time slot from when the countdown counter drops to 0 based on the value of the countdown counter. The MAC layer of the field device calculates the time when the access controller will send downlink data to the current access device and the neighboring access device respectively based on the time slot.

[0007] Furthermore, when the MAC layer of the field device identifies data frames with the same sequence number in the processed downlink data, it only processes the first valid frame and discards redundant frames.

[0008] Furthermore, when the processed downlink data sent by the current access device and the neighboring access device are the same data frame, it is determined to be the homogeneous service; when the processed downlink data sent are different data frames, it is determined to be the heterogeneous service.

[0009] Furthermore, when the data type is determined to be the homogeneous service, the field device simultaneously sends uplink data to the current access device and the neighboring access device via full-bandwidth broadcast. The current access device and the neighboring access device then send the uplink data to the access controller, which performs redundancy removal on the uplink data.

[0010] Furthermore, when the data type is determined to be the heterogeneous service, the field device sends a first control interaction frame to the current access device on the first resource unit, and at the same time sends a second control interaction frame to the neighboring access device on the second resource unit. The content of the first control interaction frame and the second control interaction frame are different.

[0011] Furthermore, the MAC frame includes uplink data and an acknowledgment frame.

[0012] Furthermore, when transmitting uplink data in the full-bandwidth broadcast, there is no need to split the transmit power, thus maximizing the signal-to-noise ratio.

[0013] Furthermore, the method also includes: when the field device leaves the handover area, and the RSSI received by the current access device and the neighboring access device is lower than the exit threshold, the access controller uses a countdown mechanism to switch to a single access device mode through the field device.

[0014] This invention also includes a seamless roaming system based on multi-node redundancy collaboration, used to implement a seamless roaming method based on multi-node redundancy collaboration, comprising: Access controller; Access devices include the current access device and neighboring access devices; On-site equipment; The field device is used to simultaneously send MAC frames to the current access device and neighboring access devices; The neighboring access device is used to extract the RSSI of the received MAC frame. When the RSSI reaches a threshold, it sends the RSSI and the address of the field device to the access controller. The access controller is used to determine, based on the received RSSI and the address of the field device, that the field device has entered the junction area between the current access device and the neighboring access device; The access controller is also configured to send a countdown marker to the current access device, the countdown marker including a decrementing counter; The access controller is also configured to send downlink data to the current access device and the neighboring access device respectively when the decrementing counter drops to 0; The current access device and the neighboring access device are used to send processed downlink data to the field device on different resource units; The field device is also used to determine the data type based on the received processed downlink data. If the data type is homogeneous service, it sends uplink data to the current access device and neighboring access devices through full bandwidth broadcast. If the data type is heterogeneous service, it sends different control interaction frames to the current access device and neighboring access devices using different resource units.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This invention utilizes two physically separated access devices to provide bidirectional redundancy for the handover zone link without introducing complex physical layer fusion mechanisms, through frequency band segmentation and dual-end MAC layer deduplication. During the handover and departure phases, it achieves stable communication and soft roaming handover with zero latency jitter.

[0016] 2. To address the unavoidable occasional packet loss in industrial environments, this invention introduces a countdown warning mechanism. Even in situations with poor channel conditions in the handover zone and a small amount of control signaling loss, the terminal can still accurately synchronize the physical layer segmentation time point based on the countdown value in subsequent frames, avoiding deadlock of the transceiver state machine and improving system robustness.

[0017] 3. This invention utilizes the collision-free characteristics of dedicated TDMA time slots to endow the terminal's underlying transmission array with adaptive selection capabilities. For service data, a full-bandwidth direct transmission mode is adopted to maximize transmit power utilization, while macro-diversity deduplication processing is delegated to the network side. For connection interaction control frames, a resource unit segmentation concurrent mode is adopted. This design achieves fine-grained connection management while ensuring high reliability and redundancy.

[0018] Based on the above reasons, this invention can be widely applied in fields such as industrial wireless communication. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of multi-node redundancy in the present invention.

[0021] Figure 2 This is a timing diagram of a seamless roaming method and system based on multi-node redundancy collaboration according to the present invention.

[0022] Figure 3 This is a schematic diagram of downlink multi-RU parallel reception and MAC layer deduplication in the handover area of ​​the present invention.

[0023] Figure 4 This is a schematic diagram of the uplink adaptive concurrency and AC backend deduplication logic of the present invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] like Figure 1As shown, the FD (Field Device) passes through the single-node effective coverage area of ​​AD1 (Current Access Device), the multi-AD handover area, and the single-node effective coverage area of ​​AD2 (Nearby Access Device) sequentially from left to right. When the FD is in the single-node effective coverage area of ​​AD1, it occupies the full bandwidth for single-link communication with AD1. When the FD enters the multi-AD handover area, the underlying layer is divided into different RUs (Resource Units), performing downlink redundant concurrency and uplink adaptive transmission. When the FD completes a smooth handover and is in the single-node effective coverage area of ​​AD2, it resumes full-bandwidth communication and establishes a single-link connection with AD2.

[0027] like Figure 2 As shown, this invention provides a seamless roaming method based on multi-node redundant collaboration, comprising the following steps: S1. The field device simultaneously sends MAC (Media Access Control) frames to the current access device and the neighboring access device. The neighboring access device extracts the RSSI (Received Signal Strength Indicator). When the RSSI reaches the threshold, the neighboring access device sends the RSSI and the address of the field device to the access controller. The access controller determines when the field device enters the junction area between the current access device and the neighboring access device.

[0028] Specifically, all AD and FD devices across the network have maintained sub-microsecond absolute time alignment and crystal oscillator frequency offset compensation using preceding technology. All AD devices are in normal data transmission and reception mode. The first step is that when the mobile FD sends uplink service data or acknowledgment frames in its dedicated TDMA time slot, in addition to the currently associated primary AD, the adjacent AD within the FD's radio frequency coverage area can also receive the uplink signal normally.

[0029] The second step involves the adjacent AD extracting the received RSSI value after successfully demodulating the uplink frame. If the RSSI meets the handover area cooperation threshold set by the system, the AD will report the data along with the FD's MAC address to the AC.

[0030] The third step, after the AC summarizes the data, determines that the FD has entered the handover area of ​​two ADs (such as AD1 and AD2) and prepares to start the multi-AD joint concurrent stable communication mechanism.

[0031] S2. The access controller sends a countdown flag to the currently accessed device. The countdown flag includes a decrementing counter.

[0032] In the step of sending countdown markers: each time the access controller sends a countdown marker to the current access device, the value of the decrement counter will decrease sequentially, with the initial value of the decrement counter being greater than or equal to 3; the current access device sends a control frame to the field device, the control frame including the countdown marker; the field device calculates the time slot from when the decrement counter drops to 0 based on the value of the decrement counter; the MAC layer of the field device calculates the time when the access controller will send downlink data to the current access device and the neighboring access device respectively based on the time slot.

[0033] Specifically, to address the issue of transmit / receive state machine deadlock caused by the loss of a single control command, when the AC determines that dual-path redundancy is required, a countdown-based dynamic bandwidth allocation prediction is implemented: The AC constructs a frame carrying a joint transmission countdown reconfiguration flag (CountdownFlag) and sends it through the current master AD. This flag contains a decrementing counter N (e.g., 3, 2, 1) indicating that the FD should switch to multi-RU receive mode after N time slots.

[0034] Within N consecutive scheduling slots, the primary AD continuously transmits frames carrying a decrementing counter. Once the primary receiver (FD) successfully receives any one of these frames, it can accurately calculate the absolute effective slot for activating the multi-RU parallel reception mechanism based on the current counter value. This mechanism allows for occasional loss of a small number of control frames under poor channel conditions in the handover area, ensuring a flawless reconfiguration process.

[0035] When the designated time slot for the countdown to zero arrives, the MAC layer of the FD instructs the PHY layer (Physical Layer) baseband to switch the receive mode, enabling the receive filter to cover and process the different RU1 (first resource unit) and RU2 (second resource unit) signals in parallel.

[0036] S3. When the decrement counter drops to 0, the access controller sends the downlink data to the current access device and the neighboring access device respectively. The current access device and the neighboring access device send the processed downlink data to the field device in different resource units.

[0037] like Figure 3 As shown, specifically, in the time slot after the countdown reaches zero, the AC (Access Controller) copies and distributes downlink data to AD1 and AD2. At the specified absolute transmission time, AD1 transmits on RU1, and AD2 simultaneously transmits the same data on different RU2 instances, as shown... Figure 1 As shown. The FD physical layer, in multi-RU listening mode, demodulates and decodes the data, sending it to the MAC layer. When the MAC layer of the field device identifies data frames with the same sequence number in the processed downlink data, it only processes the first valid frame and discards redundant frames.

[0038] S4. The field device determines the data type based on the processed downlink data. If the data type is homogeneous, the field device sends uplink data to the current access device and neighboring access devices through full-bandwidth broadcast. If the data type is heterogeneous, the field device uses resource units to send different control interaction frames to the current access device and neighboring access devices.

[0039] When the processed downlink data sent by the current access device and the neighboring access device are the same data frame, it is determined to be a homogeneous service; when the processed downlink data sent by the current access device and the neighboring access device are different data frames, it is determined to be a heterogeneous service.

[0040] like Figure 4 As shown, when FD needs to reply with data in a dedicated uplink time slot, the FD's MAC layer automatically selects the underlying transmission array based on the data type to be sent: When the data type is determined to be homogeneous service, the field device simultaneously transmits uplink data to the current access device and neighboring access devices via full-bandwidth broadcast. The current access device and neighboring access devices then transmit the uplink data to the access controller, which performs redundancy removal on the uplink data. When transmitting uplink data via full-bandwidth broadcast, there is no need to split the transmit power, thus maximizing the signal-to-noise ratio.

[0041] Specifically, if the data to be transmitted is regular service data, i.e., a response to the same data frame being sent to two ADs, FD preferentially uses full bandwidth (or main channel) direct transmission. Since there is no need to split the transmit power, the signal can achieve the maximum SNR (Signal-to-Noise Ratio). At this time, the nearby AD1 and AD2 naturally form macro diversity reception, each reporting to the AC, and the AC backend performs redundancy deduplication.

[0042] When the data type is determined to be a heterogeneous service, the field device sends a first control interaction frame to the current access device on the first resource unit, and at the same time sends a second control interaction frame to the neighboring access device on the second resource unit. The content of the first control interaction frame and the second control interaction frame are different.

[0043] During the handover transition phase, the FD needs to send different control interaction frames to AD1 and AD2, such as sending an exit report to AD1 and a ranging handshake to AD2. The FD automatically switches to multi-RU orthogonal concurrent mode. Under local absolute time driving, the FD sends frame groups to AD1 on RU1 and simultaneously sends frame groups to AD2 on RU2.

[0044] S5. When the field device leaves the handover area, and the RSSI received by the current access device and the adjacent access device is lower than the exit threshold, the access controller uses a countdown mechanism to switch the field device to a single access device mode, completing the final smooth handover transition.

[0045] This invention also includes a seamless roaming system based on multi-node redundancy collaboration, used to implement the aforementioned seamless roaming method based on multi-node redundancy collaboration, comprising: Access controller.

[0046] Access devices include current access devices and neighboring access devices.

[0047] On-site equipment.

[0048] The field device is used to send MAC frames to the current access device and neighboring access devices simultaneously.

[0049] The neighboring access device is used to extract the RSSI of the received MAC frame. When the RSSI reaches the threshold, it sends the RSSI and the address of the field device to the access controller.

[0050] The access controller is used to determine, based on the received RSSI and the address of the field device, whether the field device has entered the handover zone between the current access device and the neighboring access devices.

[0051] The access controller is also used to send countdown markers to the currently accessed devices, the countdown markers including a decrementing counter.

[0052] The access controller is also used to send downlink data to the current access device and the neighboring access device respectively when the decrement counter drops to 0.

[0053] The current access device and the neighboring access device are used to send processed downlink data to the field device on different resource units.

[0054] The field equipment is also used to determine the data type based on the received processed downlink data. If the data type is homogeneous, uplink data is sent to the current access device and neighboring access devices through full bandwidth broadcast. If the data type is heterogeneous, different control interaction frames are sent to the current access device and neighboring access devices using different resource units.

[0055] Example This embodiment provides a method for smooth bidirectional transition communication between AGVs in the handover area within a factory workshop. Assume the system includes an AC (Automatic Control Unit), the network operates based on TDMA (Time Slot Scheduling), AD1 and AD2 are deployed, the terminal FD (Automatic Device Driver) is an AGV, and the maximum bandwidth is 40MHz. The method steps include: S1. The field device sends MAC frames to the current access device and the neighboring access device simultaneously. The neighboring access device extracts the RSSI. When the RSSI reaches the threshold, the neighboring access device sends the RSSI and the address of the field device to the access controller. The access controller determines when the field device enters the junction area between the current access device and the neighboring access device.

[0056] After network deployment is complete, assuming the AGV is initially located at the center of AD1 coverage and communicates normally with AD1 via a single link over the full 40MHz bandwidth. As the AGV moves towards AD2 and enters the handover zone, its uplink data is normally monitored by AD2. AD2 measures RSSI = -64dBm, reaching the handover cooperation threshold and reports it to AC. AC determines that the AGV has entered the handover zone.

[0057] S2. The access controller sends a countdown flag to the currently accessed device. The countdown flag includes a decrementing counter.

[0058] The AC decides to allocate the bandwidth to different RU1 (20M) and RU2 (20M). In the next three consecutive time slots, the AC sends reconfiguration flags with Countdown=3, 2, and 1 respectively via AD1. Assuming the frame with Countdown=3 is lost due to sudden interference, the AGV successfully receives the frame with Countdown=2 in the next time slot. The AGV learns that it will initiate the reconfiguration in two time slots, and the underlying hardware prepares in advance.

[0059] S3. When the decrement counter drops to 0, the access controller sends the downlink data to the current access device and the neighboring access device respectively. The current access device and the neighboring access device send the processed downlink data to the field device in different resource units.

[0060] When the countdown reaches zero, the AGV activates dual different RUs for monitoring. At this time, AD1 transmits control commands on RU1, while AD2 simultaneously transmits the same redundant commands on different RU2s.

[0061] If the link from AD1 to the AGV is briefly and severely blocked, causing the RU1 signal to be lost, while AD2 remains unblocked, the signal reaches the AGV without loss via the different RU2 frequency band. The AGV successfully decodes the command on RU2 and sends it to the MAC layer for permission, thus avoiding communication interruption.

[0062] S4. The field device determines the data type based on the processed downlink data. If the data type is homogeneous, the field device sends uplink data to the current access device and neighboring access devices through full-bandwidth broadcast. If the data type is heterogeneous, the field device uses resource units to send different control interaction frames to the current access device and neighboring access devices.

[0063] Phase 1 (Data Transmission): After the AGV completes its task, it replies with an ACK. Since this data is transparent to the entire system, the AGV transmits it at full power across the 40MHz full bandwidth. AD1 and AD2 naturally receive and report the data, and the AC backend performs deduplication, which greatly simplifies the baseband transmission complexity and maximizes signal penetration.

[0064] Phase Two (Switch Control): As the AGV fully enters the coverage core of AD2, it prepares to perform a protocol-level switch. The AGV needs to say goodbye to AD1 and synchronize parameters with AD2. At this time, the AGV baseband is split into RU1 and RU2. RU1 sends an exit report frame to AD1, and RU2 sends a ranging handshake frame to AD2, without interfering with each other.

[0065] S5. After the handover confirmation, the RSSI of AD1 decays to its limit, and the AC restarts the countdown mechanism, instructing the AGV to restore its receiving configuration to the single-link mode of AD2. The entire process achieves zero AGV service interruption and zero control errors, completing a seamless soft handover at the network layer.

[0066] The countdown mechanism at this point is the same as the steps in S2 above.

[0067] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0068] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A seamless roaming method based on multi-node redundancy cooperation, characterized in that, Includes the following steps: The field device simultaneously sends MAC frames to the current access device and the neighboring access device. The neighboring access device extracts the RSSI. When the RSSI reaches a threshold, the neighboring access device sends the RSSI and the address of the field device to the access controller. When the access controller determines that the field device has entered the junction area between the current access device and the neighboring access device, the access controller sends a countdown flag to the current access device, the countdown flag including a decrementing counter; When the decrementing counter drops to 0, the access controller sends downlink data to the current access device and the neighboring access device respectively. The current access device and the neighboring access device send the processed downlink data to the field device in different resource units. The field device determines the data type based on the processed downlink data. If the data type is homogeneous, the field device sends uplink data to the current access device and the neighboring access device through full bandwidth broadcast. If the data type is heterogeneous, the field device uses resource units to send different control interaction frames to the current access device and the neighboring access device.

2. The seamless roaming method based on multi-node redundancy collaboration according to claim 1, characterized in that, The access controller sends a countdown marker to the currently accessed device, including: Each time the access controller sends a countdown flag to the currently accessed device, the value of the next decrement counter will decrease sequentially, with the initial value of the decrement counter being greater than or equal to 3; The current access device sends a control frame to the field device. The control frame includes a countdown marker. The field device calculates the time slot from when the countdown counter drops to 0 based on the value of the countdown counter. The MAC layer of the field device calculates the time when the access controller will send downlink data to the current access device and the neighboring access device respectively based on the time slot.

3. The seamless roaming method based on multi-node redundancy collaboration according to claim 1, characterized in that, When the MAC layer of the field device identifies data frames with the same sequence number in the processed downlink data, it only processes the first valid frame and discards redundant frames.

4. The seamless roaming method based on multi-node redundancy collaboration according to claim 1, characterized in that, When the processed downlink data sent by the current access device and the neighboring access device are the same data frame, it is determined to be a homogeneous service; when the processed downlink data sent are different data frames, it is determined to be a heterogeneous service.

5. The seamless roaming method based on multi-node redundancy collaboration according to claim 1, characterized in that, When the data type is determined to be the homogeneous service, the field device simultaneously sends uplink data to the current access device and the neighboring access device via full bandwidth broadcast. The current access device and the neighboring access device send the uplink data to the access controller, and the access controller performs redundancy removal on the uplink data.

6. The seamless roaming method based on multi-node redundancy collaboration according to claim 1, characterized in that, When the data type is determined to be the heterogeneous service, the field device sends a first control interaction frame to the current access device on the first resource unit, and at the same time sends a second control interaction frame to the neighboring access device on the second resource unit. The content of the first control interaction frame and the second control interaction frame are different.

7. The seamless roaming method based on multi-node redundancy collaboration according to claim 1, characterized in that, The MAC frame includes uplink data and acknowledgment frames.

8. The seamless roaming method based on multi-node redundancy collaboration according to claim 1, characterized in that, When transmitting uplink data in the full-bandwidth broadcast, there is no need to split the transmit power, so that the signal can obtain the maximum signal-to-noise ratio.

9. The seamless roaming method based on multi-node redundancy collaboration according to claim 1, characterized in that, The method further includes: when the field device leaves the handover area, and the RSSI received by the current access device and the adjacent access device is lower than the exit threshold, the access controller uses a countdown mechanism to switch to a single access device mode through the field device.

10. A seamless roaming system based on multi-node redundancy collaboration, used to implement the seamless roaming method based on multi-node redundancy collaboration as described in any one of claims 1-9, characterized in that, include: Access controller; Access devices include the current access device and neighboring access devices; On-site equipment; The field device is used to simultaneously send MAC frames to the current access device and neighboring access devices; The neighboring access device is used to extract the RSSI of the received MAC frame. When the RSSI reaches a threshold, it sends the RSSI and the address of the field device to the access controller. The access controller is used to determine, based on the received RSSI and the address of the field device, that the field device has entered the junction area between the current access device and the neighboring access device; The access controller is also configured to send a countdown marker to the current access device, the countdown marker including a decrementing counter; The access controller is also configured to send downlink data to the current access device and the neighboring access device respectively when the decrementing counter drops to 0; The current access device and the neighboring access device are used to send processed downlink data to the field device on different resource units; The field device is also used to determine the data type based on the received processed downlink data. If the data type is homogeneous service, it sends uplink data to the current access device and neighboring access devices through full bandwidth broadcast. If the data type is heterogeneous service, it sends different control interaction frames to the current access device and neighboring access devices using different resource units.

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