A wireless local area network data transmission system

Abstract

The present invention belongs to the technical field of wireless data transmission, and discloses a wireless local area network data transmission system, including a CPE and multiple APs in the same local area network; the CPE includes two radio frequency units, the two radio frequency units establish two wireless connections with two APs, the CPE does not switch the wireless connections of the two radio frequency units at the same time when roaming and switching between APs, and the two radio frequency units have a time interval when switching; the CPE establishes two layer 2 tunnels with a third AP among the multiple APs, each inner layer service data message is forwarded through the two tunnels at the same time, and each tunnel is bound to a wireless connection for data transmission. The wireless local area network data transmission system of the present invention solves the problem of packet loss when the wireless CPE switches between APs in a wireless network running a local forwarding mode, improves the reliability of the wireless link in the industrial wireless application scenario, and achieves a zero packet loss effect for the application terminal connected to the southbound CPE during roaming and switching.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless data transmission, and particularly relates to a wireless local area network data transmission system. Background Art

[0002] Wireless Local Area Network (WLAN) technologies and products have been very widely used in the home and office fields. In recent years, WLAN technologies and products have also been increasingly used in the industrial control field. Especially due to the adoption of the WAPI (WLAN Authentication and Privacy Infrastructure) technology to solve the hidden dangers of WLAN in network security, WLAN technologies have been widely used in the networking of AGVs (Automated Guided Vehicles) in industrial scenarios such as substations and automated warehouses. In these scenarios, a CPE (Customer Premises Equipment) is installed in the robotic device. The CPE realizes a wireless connection with the AP in the north direction, and the CPE is connected to one or more service modules with Ethernet interfaces in the south direction, so as to realize the network interaction between the AGV and the main station server of the control station through the wireless network.

[0003] In these scenarios, the AGV moves quickly, so it will perform wireless roaming handover between multiple APs (Wireless Access Points). In order to minimize packet loss when wireless terminal devices such as AGVs roam and handover between APs, the roaming handover technology is usually optimized to reduce the time of wireless packet loss.

[0004] The Chinese invention patent with the application number 202110091748.7 discloses a method and device for reducing packet loss when a WAPI CPE device switches between APs. It adopts a dual wireless connection method of primary and standby. When the AP switches, the traffic is first switched from the primary wireless connection to the standby wireless connection, and then the primary wireless connection is switched between APs, reducing the packet loss duration of the wireless CPE when switching between APs to less than 50 milliseconds, but there is still a small amount of packet loss. Summary of the Invention

[0005] The present invention aims to solve at least to some extent the above technical problems. For this reason, the object of the present invention is to provide a wireless local area network data transmission system.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A wireless local area network data transmission system, comprising:

[0008] A CPE and multiple APs provided in the same local area network;

[0009] The CPE includes two radio frequency units. The two radio frequency units establish two wireless connections with the same AP or two APs among multiple APs. When the CPE roams and switches between APs, the wireless connections of the two radio frequency units are not switched simultaneously, and there is a time interval between the switches of the two radio frequency units.

[0010] The CPE automatically establishes two bidirectional layer-2 tunnels with a third AP. Specifically, after the CPE establishes a wireless connection with an AP, it sends a control message to the third AP. The control message includes the BSSIDs of the two radio frequency units of the CPE, the BSSID of the radio frequency unit for this wireless connection establishment, and the IP address of the radio frequency unit for this wireless connection establishment. After receiving the control message, the third AP deletes the layer-2 tunnel corresponding to the BSSID of the radio frequency unit for this wireless connection establishment (if any), establishes a layer-2 tunnel with the IP address of the radio frequency unit for this wireless connection establishment as the peer address, and establishes a packet replication pairing relationship between the two layer-2 tunnels based on the BSSIDs of the two radio frequency units. When the CPE or the third AP sends a service packet, it first marks the packet sequence number in the packet, then replicates the packet, and encapsulates the original packet and the replicated packet into the two layer-2 tunnels and sends them to the peer simultaneously. The packets received by the CPE or the third AP from the two layer-2 tunnels are de-duplicated based on the packet sequence numbers in the packets.

[0011] When the CPE sends an inner-layer service packet, the packets of the two tunnels are forwarded through different wireless connections respectively, that is, the packets of the first layer-2 tunnel are bound to the first wireless connection for forwarding, and the packets of the second layer-2 tunnel are bound to the second wireless connection for forwarding.

[0012] Preferably, the third AP is not necessarily the AP connected to the CPE; the third AP may not provide wireless access, or it is a packet forwarding device within a local area network with multiple APs.

[0013] Preferably, the CPE configures the peer address of the layer-2 tunnel to the third AP, and the CPE always establishes two layer-2 tunnels based on this peer address.

[0014] Preferably, the third AP does not need to configure the tunnel to the CPE, but automatically establishes two layer-2 tunnels through the control message interaction between the CPE and the third AP.

[0015] Preferably, the packets received by the CPE and the third AP from one of the layer-2 tunnels are not forwarded out from the other layer-2 tunnel.

[0016] Preferably, when the CPE switches between APs, it does not switch simultaneously, and there is a certain time interval, such as the time interval is not less than 300 milliseconds.

[0017] The beneficial effects of the present invention are:

[0018] A wireless local area network data transmission system provided by the present invention solves the problem of packet loss when a wireless CPE switches between APs in a wireless network operating in the local forwarding mode, improves the reliability of the wireless link in the industrial wireless application scenario, and achieves a zero-packet-loss effect when the application terminal connected to the south of the CPE roams and switches. Description of the Drawings

[0019] Figure 1 is a schematic diagram of the wireless local area network data transmission system of the present invention.

[0020] Figure 2 is a flowchart of message replication and transmission of the present invention.

[0021] In the figure: 101 - the first AP; 102 - the second AP; 103 - the third AP; 104 - the fourth AP; 200 - CPE; 201 - Ethernet interface; 301 - the first wireless connection; 302 - the second wireless connection; 401 - the first layer 2 tunnel; 402 - the second layer 2 tunnel. Detailed Embodiments

[0022] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] It should be understood that in the embodiments, the functions / actions that appear may be different from the order in which the drawings appear. For example, depending on the functions / actions involved, they may actually be executed substantially concurrently, or sometimes the two continuously shown figures may be executed in the reverse order.

[0024] Such as Figure 1 and Figure 2As shown in the figure, a wireless local area network data transmission system according to this embodiment includes multiple APs in the wireless local area network. The multiple APs include the first AP 101, the second AP 102, the third AP 103, the fourth AP 104, etc. The multiple APs are connected together through a local area network, for example, interconnected through an Ethernet switch. This local area network is also connected to other networks, so that other networks are connected to the north of the wireless local area network. The CPE 200 is connected to the Ethernet interface 201. The CPE 200 has two radio frequency units, Radio1 and Radio2. These two radio frequency units can simultaneously connect to the AP devices in the wireless local area network. The radio frequency unit Radio1 is connected to the first AP 101 to form a first wireless connection 301, and the radio frequency unit Radio2 is connected to the second AP 102 to form a second wireless connection 302.

[0025] In order to ensure that there is no packet loss during the roaming and handover of the CPE between APs, two measures are adopted: 1. When the CPE roams and hands over between APs, the wireless connections of the two radio frequency units are not switched simultaneously. There is a time interval between the switches of the two radio frequency units, and the time interval is not less than 300 milliseconds; 2. The packets are redundantly sent between the CPE and a fixed AP.

[0026] Select a certain AP in the wireless local area network connected to the CPE as the third AP. This method is particularly beneficial to the application scenarios of the wireless local area network adopting the local forwarding (also known as distributed forwarding) mode. In some application scenarios such as substation application scenarios (where there is a wide area network between the AP and the AC), local forwarding must be adopted because it is necessary to avoid the problem of increased delay caused by the service packets in the centralized forwarding mode going around to the AC (wireless controller) and then returning to the local area network where the AP is located. The third AP can still access wireless terminals. In this embodiment, the CPE 200 can still roam and hand over to the third AP without affecting the implementation of this solution.

[0027] In order to forward the service packets between the CPE 200 and the third AP 103 along different paths, two layer 2 tunnels are established between the CPE and the third AP, namely the first layer 2 tunnel 401 and the second layer 2 tunnel 402. When forwarding packets, each layer 2 tunnel is bound to a wireless connection for forwarding; that is, the data of the first layer 2 tunnel 401 is forwarded through the first wireless connection 301, and the data of the second layer 2 tunnel 402 is forwarded through the second wireless connection 302. The packets are copied in pairs and forwarded on the first layer 2 tunnel 401 and the second layer 2 tunnel 402. In order to forward the data of the first layer 2 tunnel by binding to the first wireless connection and the data of the second layer 2 tunnel by binding to the second wireless connection, it can be achieved by implementing source address policy routing on the CPE.

[0028] To establish the first and second layer tunnels on the CPE, the peer address of the tunnel is configured as the IP address of the third AP on the CPE, and the IP addresses of the two radio frequency units of the CPE are used as the local IP addresses. The two radio frequency units of the CPE obtain two different IP addresses, namely the first radio frequency unit IP address and the radio frequency unit IP address, through static configuration or DHCP dynamic acquisition. Thus, source address policy routing can be implemented based on these two IP addresses, and the policy routing designates the outgoing interface as different radio frequency units of the CPE. This situation is naturally supported on the third AP because the destination addresses of the two layer 2 tunnels established on the third AP are different. When the packet performs outer layer IP forwarding, the outer layer IP packet will naturally be forwarded according to the directly connected route, and thus will naturally be bound to the wireless link corresponding to the peer IP address.

[0029] On the third AP, there are two ways to configure the two layer 2 tunnels to the CPE:

[0030] 1. Static method: That is, statically configure the layer 2 tunnel. The local address of the layer 2 tunnel is the IP address of the third AP (the same as the IP address of the third AP used as the tunnel peer address on the CPE). The peer addresses of the two layer 2 tunnels are the first radio frequency unit IP address and the second radio frequency unit IP address of the CPE respectively; if there are multiple CPE devices, this method is applicable on the third AP.

[0031] 2. Dynamic method: After the CPE establishes a wireless connection with an AP, it sends a control message to the third AP. The control message includes the BSSIDs of the two radio frequency units, the BSSID of the radio frequency unit for this wireless connection establishment, and the IP address of the radio frequency unit for this wireless connection establishment. After receiving the control message, the third AP triggers the deletion of the layer 2 tunnel corresponding to the BSSID of the radio frequency unit for this wireless connection establishment and the establishment of a layer 2 tunnel with the IP address of the radio frequency unit for this wireless connection establishment as the peer address, and establishes a packet replication pair relationship between the two layer 2 tunnels based on the BSSIDs of the two radio frequency units; both the CPE and the third AP execute this trigger mechanism when the CPE first connects to the AP or during subsequent AP roaming and handover.

[0032] The Layer 2 tunneling technology can adopt the EoGRE (Ethernet over GRE) Layer 2 VPN tunneling technology or the L2TPv3 Layer 2 VPN tunneling technology. Both of these two technologies can achieve the transparent transmission of Layer 2 Ethernet network packets. The tunnel headers of the EoGRE and L2TPv3 Layer 2 VPN tunnels both have packet sequence numbers, and can identify duplicate packets based on the Layer 2 Ethernet header of the payload packets in the tunnel and this sequence number. Of course, an 802.1CB protocol header can also be inserted between the protocol number and the MAC address of the original Layer 2 Ethernet packet header. The protocol number of this protocol header is 0xF1C1, and the first 2 of the subsequent 4 bytes are reserved, and the last 2 bytes are the packet sequence number.

[0033] To achieve redundant packet transmission, the CPE and the third AP 103 are used as the packet replication and de-duplication points. Between these two packet replication and de-duplication points, for the packets received from the wired side, they are all replicated into pairs and marked with the same packet sequence number, and are sent to each other along different network paths. The receiving party performs de-duplication processing according to the information such as the packet sequence number in the packet, and only receives the first-arrived packet with the same sequence number. That is, the packets received by the CPE or the third AP are all replicated into pairs and marked with the same packet sequence number, and are respectively encapsulated into two Layer 2 tunnels and sent to the peer end at the same time. The packets received from the two Layer 2 tunnels are de-duplicated based on the packet sequence number in the packet.

[0034] Packet replication and transmission are as Figure 2 shown. The packet is replicated before sending and then sent. For example, on the CPE200 device, before sending the packet from the first Layer 2 tunnel 401 as the outgoing interface f1, check whether there is a paired outgoing interface f2 in the replication relationship of the first Layer 2 tunnel 401 interface. In this embodiment, the second Layer 2 tunnel 402 interface is the paired outgoing interface. At this time, replicate the packet once, and then send the original packet from the first Layer 2 tunnel 401 interface, and send the replicated packet from the second Layer 2 tunnel 402 interface.

[0035] To avoid network loops, enhanced loop avoidance needs to be implemented, that is, the packets received by the CPE and the third AP from a certain Layer 2 tunnel will not be forwarded out from the other Layer 2 tunnel. That is, the packets received from the first Layer 2 tunnel 401 interface cannot be sent from the second Layer 2 tunnel 402 interface, and vice versa, the packets received from the second Layer 2 tunnel 402 interface cannot be sent from the first Layer 2 tunnel 401 interface. Thus, the loop problem caused by the replication of two packets is avoided.

[0036] This wireless local area network data transmission system is particularly suitable for running in a wireless local area network in local forwarding mode. Of course, it can also run in a wireless network in centralized forwarding mode. For the wireless network in local forwarding mode, the traffic received by the southbound Ethernet interface 201 of the CPE200 will be first sent to the third AP103, and then the traffic will be locally forwarded at 103 and sent to the target network. For the wireless network in centralized forwarding mode, the traffic received by the southbound Ethernet interface 201 of the CPE200 will be first sent to the third AP103, and then the traffic will be sent by the third AP103 to the AC, and the traffic will be sent by the AC to the target network.

[0037] The CPE is equipped with two radio frequency units. These two radio frequency units are simultaneously connected to the APs in the wireless local area network. When the CPE switches between APs, the two radio frequency units do not switch simultaneously and there is a certain time interval. By establishing two layer-2 tunnels between the CPE and the third AP to achieve redundant replication and forwarding of service traffic, it can effectively avoid packet loss problems when the CPE roams and switches between APs, thus significantly improving the reliability of packet forwarding between the CPE and the wireless network, which is beneficial to improving the effects of applications sensitive to packet loss such as robot control.

[0038] The present invention is not limited to the above optional implementation manners. Anyone can obtain other various forms of products under the inspiration of the present invention. However, no matter what changes are made in its shape or structure, as long as the technical solutions fall within the scope defined by the claims of the present invention, they are all within the protection scope of the present invention.

Claims

1. A wireless local area network data transmission system, characterized in that: include: CPE and multiple APs located in the same local area network; The CPE includes two radio frequency units, and the two radio frequency units establish two wireless connections with the same AP or two APs among the multiple APs. When the CPE roams and switches between APs, the wireless connections of the two radio frequency units are not switched at the same time, and there is a time interval when the two radio frequency units are switched; The CPE establishes two Layer 2 tunnels with the third AP among the multiple APs. When forwarding messages, each Layer 2 tunnel is bound to a wireless connection for forwarding; After the CPE establishes a wireless connection with an AP through a radio unit, it sends a control message to the third AP, where the control message includes the BSSIDs of the two radio units, the BSSID of the radio unit for establishing the wireless connection this time, and the IP address of the radio unit for establishing the wireless connection this time; after receiving the control message, the third AP deletes the layer 2 tunnel corresponding to the BSSID of the radio unit for establishing the wireless connection this time, establishes a layer 2 tunnel with the IP address of the radio unit for establishing the wireless connection this time as the peer address, and establishes a message replication pair relationship between the two layer 2 tunnels based on the BSSIDs of the two radio units; The messages received by the CPE or the third AP are copied into pairs and marked with the same message sequence number, respectively encapsulated into two Layer 2 tunnels and sent to the peer end at the same time. The messages received from the two Layer 2 tunnels are deduplicated based on the message sequence numbers in the messages.

2. The wireless local area network data transmission system according to claim 1, characterized in that: The CPE is configured with a peer address of the layer 2 tunnel to the third AP, and two layer 2 tunnels are always established based on the peer address.

3. The wireless local area network data transmission system according to claim 1, characterized in that: The message received by the CPE and the third AP from one of the layer 2 tunnels will not be forwarded from the other layer 2 tunnel.

4. The wireless local area network data transmission system according to claim 1, characterized in that: The time interval is not less than 300 milliseconds.

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