Information element used to indicate loss of the backhaul connection

Abstract

Systems and methods for managing nodes in a mesh network are provided. An information element may be provided to indicate the status of a backhaul connection. A critical node may use the information element to determine the status of a backhaul connection before joining a PAN. A critical path may be created and maintained, the critical path including the critical node and any intermediate nodes between the critical node and the root. The critical node may switch PANs when a backhaul connection becomes unavailable. Nodes other than the critical node on the critical path may also facilitate the switch. The loss of a backhaul connection may be determined by examining the information element. A node may switch PANs and coordinate the switch with its child nodes.

Description

Technical Field

[0001] The present invention relates to managing nodes in a mesh network and, in particular, to providing information elements to indicate a loss of a backhaul connection. Background Art

[0002] The PAN architecture may have hysteresis in the network topology to prevent thrashing when there is a temporary disruption in the network, such as a temporary loss of a backhaul connection. However, some systems and devices cannot tolerate a temporary loss of a backhaul connection and require a PAN switchover once the backhaul connection becomes unavailable.

[0003] Typically, the root node does not routinely communicate the status of the backhaul connection to other nodes in the PAN. Instead, each node must determine the status of the backhaul connection by sending upper layer messages and receiving responses from the backhaul. Since a node cannot send upper layer messages before it joins the PAN, a node cannot determine the status of the backhaul connection before joining. A node that needs a backhaul connection may join the PAN and then determine that the backhaul connection is not available.

[0004] A node that determines that the backhaul connection of its current PAN is unavailable may determine that it needs to switch PANs. However, the node may not have direct visibility to another PAN, which may delay the switch to a different PAN.

[0005] When a node switches PAN, any child node either stays with the current PAN by finding a new parent node, or switches to the new PAN by unjoining the current PAN and joining the new PAN. This process is time consuming and makes the child node unavailable until it locates a new parent node or completes the unjoin / join process. Summary of the invention

[0006] Aspects of the invention provide improvements to the way a node determines the state of a backhaul connection and joins or switches to a PAN with an available backhaul connection. Additional aspects of the invention provide a more efficient way to switch PANs when a node has child nodes. Regardless of the reason for the switch, a node can take its child nodes with it when it switches.

[0007] A node may consider the state of the backhaul connection before joining a PAN. The node may be a key node that requires an available backhaul connection. The state of the backhaul connection may be included in a layer 2 message such as a beacon. In one example, the backhaul state information is included in an information element in the beacon.

[0008] Once a critical node joins a PAN, a critical path from the critical node to the root of the PAN can be established. In one example, a layer 3 message (such as a DAO message) is used to establish the critical path. Nodes along the critical path can seek to join a new PAN when the backhaul connection of the current PAN becomes unavailable.

[0009] When a node switches to a new PAN, it can coordinate the switch with its child nodes. The switched node identifies the new PAN and obtains the timing synchronization information of the new PAN. The switched node sends the timing synchronization information of the new PAN and the time for switching to the new PAN to its child nodes. The switched node and child nodes maintain the timing synchronization information of both the current PAN and the new PAN. At the time for switching, the switched node and its child nodes switch to the new PAN. Whenever a switch occurs, the node can coordinate the switch to the new PAN with its child nodes. This coordination is not limited to switching based on loss of backhaul connection.

[0010] These illustrative aspects and features are not mentioned to limit or define the present invention, but to provide examples to aid in understanding the inventive concepts disclosed in the present application.Other aspects, advantages and features of the present invention will become apparent after reviewing the entire application. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] These and other features, aspects and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which:

[0012] Figure 1 Two PANs and non-joined critical nodes are illustrated in accordance with an aspect of the present invention.

[0013] Figure 2 The diagram illustrates key nodes participating in a PAN according to an aspect of the present invention.

[0014] Figure 3 The diagram illustrates the loss of a backhaul connection of a PAN according to an aspect of the present invention.

[0015] Figure 4 The diagram illustrates key nodes for switching to a different PAN according to one aspect of the present invention.

[0016] Figure 5 Illustrated is a parent node switching to a different PAN in accordance with one aspect of the present invention.

[0017] Figure 6 A parent node and its child nodes switching to a different PAN according to one aspect of the present invention are illustrated.

[0018] Figure 7The diagram illustrates communication between a joining node and two PANs according to one aspect of the present invention.

[0019] Figure 8 An exemplary node according to an aspect of the invention is illustrated. DETAILED DESCRIPTION

[0020] The present invention relates to a system and method for managing nodes in a mesh network, including enabling key nodes to join a PAN, creating and maintaining key paths, performing PAN switching through key path nodes, and maintaining a parent / child relationship when switching PANs. The key node may consider the state of the PAN's backhaul connection before joining the PAN. Once joined, the key path from the key node to the root is identified, and if the backhaul connection of the current PAN becomes unavailable, nodes along the key path (including the key node) may attempt to join a new PAN. The state of the PAN's backhaul connection may be transmitted using an information element (IE) in a beacon. If the key path node is a parent node with one or more child nodes, and it switches PANs, the key path node and the child nodes may switch PANs while maintaining their parent-child relationship. When the parent node switches PANs for reasons other than loss of the backhaul connection, the parent node may maintain its parent-child relationship with its child nodes.

[0021] Key nodes and key paths

[0022] Figure 1 Two PANs are shown - PAN A and PAN B. Node 110 is the root of PAN A, and node 150 is the root of PAN B. PAN A includes nodes A-1 to A-6, and PAN B includes nodes B-1 and B-2. Backhaul connection 104 connects PAN A to central system 102, and backhaul connection 106 connects PAN B to the central system. Although not shown in FIG. Figure 1 , but any number of intermediate devices may exist between the PAN and the central system 102.

[0023] Node 110 and node 150 monitor the status of their respective backhaul connections and include information about the status of their backhaul connections in their beacons. In one example, they determine whether they are connected to an NTP server, and if so, determine that their backhaul connections are available. Other implementations may consider other factors to determine whether their backhaul connections are available or unavailable, including but not limited to connections to specific systems or servers, or connections to time sources. Each node includes its current backhaul status information in an IE in its respective beacon. The IE may be a new IE, or it may be an existing IE. If an existing IE is used, the backhaul status information may be appended to the IE. Any type of IE that includes backhaul status information is referred to herein as a backhaul status IE. Backhaul status information may be conveyed using one bit, where a first value indicates that the backhaul connection is available, and a second value indicates that the backhaul connection is unavailable or unknown. In some implementations, the backhaul status information includes additional information, such as how long the backhaul connection has been in its current state. For example, a timestamp indicating the time of the last state change may be used. In Figure 1 In the example illustrated in , backhaul connection 104 is available and backhaul connection 106 is not available.

[0024] exist Figure 1 In , node N is a critical node that is not joined to any PAN. A critical node is a node that requires a backhaul connection. If a backhaul connection becomes available, the critical node may not be able to wait for the backhaul connection to reconnect. An example of a critical node is a node associated with DA (Distribution Automation) equipment (e.g., line sensors, switches, and re-closers). A node can be designated as a critical node at the time of installation, or it can be designated as a critical node after installation.

[0025] Node N receives Beacon A from PAN A and Beacon B from PAN B. In this example, Beacon A includes a Backhaul Status IE indicating that backhaul connection 104 is available, and Beacon B includes a Backhaul Status IE indicating that backhaul connection 106 is unavailable. Since node N is a critical node, it joins PAN A. Critical nodes may be configured to avoid joining a PAN that has an unavailable backhaul connection, even if other factors (e.g., rating, load, etc.) may be favorable for joining the PAN.

[0026] Figure 2PAN A is illustrated after node N joins. After node N joins, it sends a DAO message that identifies node N as a critical node. In one example, node N sets a bit in the DAO flag field to indicate that it is a critical node. Based on the DAO message, node 110, which is the root of PAN A, determines the critical path of node N and stores information describing the critical path of node N, which is the path including node N, node A-5, node A-4 and node A-1. The root can send a DAO-ACK message to node N with a bit that is set to indicate that the critical path is in place.

[0027] In some implementations, when each node between the root and node N receives the DAO-ACK message, the node checks this bit and determines that it is a critical path node. If the node does not support critical path nodes, then after it receives the message, it does not forward the message. Instead, it may discard the message or send an error message.

[0028] Node N can use other types of messages or other fields to indicate that it is a critical node, including but not limited to the indication in the hop-by-hop extension header of the IPv6 message. In one example, node N sets a bit in the hop-by-hop extension header to indicate that it is a critical node and is requesting a critical path. When node A-5 supports critical path nodes, it receives the message, checks the bit, enters the pre-critical path state, and forwards the message to the next node. The process repeats until the message reaches the root of PAN A. When the root sends a message indicating that the critical path is in place back to node N, the nodes between the root and node N can check the message and transition from the pre-critical path state to the critical path state.

[0029] Since PAN A may be a wireless mesh network, the critical path of node N may change. If the critical path changes, the critical path of node N may include additional or different nodes. The critical path information maintained by the root and the critical path state of each node affected by the change are updated to reflect the change in the critical path.

[0030] After node N joins PAN A, it generates and sends a beacon containing the Backhaul Status IE. Node N obtains information for the Backhaul Status IE from the beacon that node N receives from its parent node A-5 or other nodes in PAN A.

[0031] Backhaul connection loss and critical path

[0032] Figure 3The diagram illustrates a scenario in which the backhaul connection of PAN A becomes unavailable and the backhaul connection of PAN B is available. When node 110 detects that its backhaul connection is unavailable, it may generate a beacon, Beacon A, which includes backhaul status information in a Backhaul Status IE. Information about the status of the backhaul connection is propagated through the network until node N receives a beacon with a Backhaul Status IE indicating that the backhaul connection of PAN A is unavailable. Since node N is a critical node, once node N determines that the backhaul connection of its current PAN is unavailable, it may begin searching for a new PAN to join. If node N receives a beacon from a different PAN (such as Beacon B from PAN B), it may consider whether the backhaul connection of PAN B is available when determining whether to switch PANs. If it decides to switch PANs, it may follow the above combined method. Figure 1 and 2 A similar process is described for joining PAN B. In this example, other nodes joined to PAN A can remain joined to PAN A, as in Figure 4 As shown in .

[0033] When node N joins PAN B, its parent node, node A-5, determines that node N is no longer a child node. In one example, node N sends a disassociation message to node A-5 before joining PAN B to notify node A-5 of the switch. Node N determines whether it has any other child nodes that are key nodes or critical path nodes. If it does not have any other child nodes that are key nodes or critical path nodes, it determines that it is no longer on the critical path and sends a DAO message indicating that it is no longer a critical path node. Similarly, if node A-4 does not have a child node that is a key node or a critical path node, it sends a DAO message indicating that it is no longer a critical path node. If node A-1 does not have a child node that is a key node or a critical path node, it sends a DAO message to its parent node, node 110, and node 110 removes the critical path of node N. If node A-5 has another child node (e.g., node A-6) that is a key node or a critical path node, node A-5 may still be a critical path node. In this case, node 110 stores the critical path information of node A-6. Once a node (eg, node A-5) is no longer a critical path node, it may remain joined to its current PAN or switch to a target PAN based on factors other than the backhaul connectivity status of its current PAN and the target PAN.

[0034] In some instances, a critical node may only rarely receive beacons from another PAN. Once a node on the critical path receives a beacon from another PAN with an available backhaul connection, while the backhaul connection of the current PAN is unavailable, it may switch PANs. For example, if node A-5 receives a beacon with a backhaul status IE from node A-4 or another node in PAN A, which indicates that the backhaul connection of PAN A is unavailable, node A-5 may search for another PAN to join. Since node A-5 is on the critical path, it may be more aggressive in seeking a different PAN than if it were not on the critical path. In some implementations, a node considers its RPL layer when determining how aggressively to seek a different PAN. For example, a layer 1 node may not be as aggressive as a lower layer node.

[0035] If node A-5 receives a beacon from a different PAN (such as beacon B from PAN B), it can determine whether to switch PANs based on whether the backhaul connection of PAN B is available. When the backhaul connection of PAN B is available, node A-5 joins PAN B, such as Figure 5 as shown in . Figure 5 The diagram shows that after node A-5 joins PAN B, its child nodes, node A-6 and node N, may not join PAN A or PAN B. Figure 5 5 is not a critical node and has no child nodes that are critical nodes, so it does not identify itself as a critical node or a critical path node after joining PAN B. In some implementations, node A-6 and node N each perform a separate joining process. Each node can rejoin PAN A by finding a new parent node, join PAN B through node A-5 (its PAN A parent node), or join PAN B by finding a different parent node. Since node N is a critical node and the backhaul connection of PAN A is not available, node N joins PAN B. In the scenario where node N joins PAN B as a child node of node A-5, node N sends a DAO message that identifies node N as a critical node. In combination with the above Figure 2 The discussion proceeds in a similar manner to establishing the critical path.

[0036] In some implementations, an auxiliary backhaul connection (such as Ethernet or cellular) may be available. If so, when a critical path node receives a beacon with a Backhaul Status IE indicating that the backhaul connection is unavailable, the node may choose to remain on the current PAN and use the auxiliary backhaul connection.

[0037] If the backhaul status IE indicates that the backhaul connection is unavailable and includes information about how long the backhaul connection has been unavailable, the critical path node may consider how long the backhaul connection has been unavailable when determining when to switch to a new PAN.

[0038] Although the foregoing examples discuss the use of the Backhaul Status IE in conjunction with critical nodes, the Backhaul Status IE may be used whenever backhaul status information is useful. It is not limited to use by critical path nodes.

[0039] Maintaining parent-child relationships when switching PANs

[0040] When a node switches to a new PAN, it can maintain the existing parent-child relationship. This switch may occur due to loss of backhaul connectivity or for any other reason.

[0041] continue Figure 3 In the example of , node A-5 can bring its child nodes with it when it joins PAN B. Once node A-5 determines that it is going to switch to the target PAN, the node maintains the timing synchronization information of both its current PAN (e.g., PAN A) and its target PAN (e.g., PANB). Node A-5 obtains the timing synchronization information of the target PAN from the beacon in the target PAN. Node A-5 transmits the timing synchronization information of the target PAN and the time when it plans to switch to the target PAN to its child nodes, node A-6 and node N. The timing synchronization information and the switching time can be transmitted from node A-5 using a beacon. For example, the IE in the beacon currently provides information about the network and includes an absolute slot number, a channel hopping sequence, and a time slot offset information. The IE in the beacon can be modified to include a PAN switching timestamp. Only nodes that recognize node A-5 as their parent node can act according to the timing synchronization information and the switching time. Once node A-6 and node N receive the beacon with the timing synchronization information and the switching time, these nodes maintain the timing synchronization information of both PAN A and PAN B. At the switching time, node A-5 and its child nodes (node ​​A-6 and node N) are switched from PAN A (e.g. Figure 3 ) to PAN B (as shown in Figure 6). After the switch, node A-5 may send a DIS message to node B-2 to trigger a DIO message from node B-2. In response to the DIO message, node A-5 may send a DAO message indicating that its child node (node ​​N) is a critical node and that node A-5 is on a critical path. Once node A-5 receives the DAO-ACK message, it may send the DIO message to its child nodes (e.g., node A-6 and node N) that it brought from PAN A via a unicast, multicast, or broadcast method so that these child nodes may obtain a new network prefix.

[0042] After the node is switched to PAN B, the critical path includes Node A-5, Node B-2, Node B-1, and Node 150. By switching Node A-5, Node A-6, and Node N together to the target PAN, timing and network connectivity are maintained, and the availability of child nodes (e.g., Node A-6 and Node N) is improved.

[0043] When the parent node determines that it is switching to the target PAN for any reason, the parent-child relationship between the nodes can be maintained. This is not limited to situations where the parent node is a critical path node or when the switch is based on backhaul connection status.

[0044] Communication between key nodes and PAN

[0045] Figure 7 A critical node 704 is illustrated seeking to join a PAN. Node 704 initially determines whether to join the PAN corresponding to mesh network 702. At 710, the backhaul connection of network 702 becomes unavailable. Subsequently, at 712, a border router or root node of network 702 communicates the loss of the backhaul connection to the network. In one example, the border router sends a beacon with a backhaul status IE indicating that the backhaul connection is unavailable. Critical node 704 begins listening to beacons at 714 to find a network to join. At 716, node 704 receives a beacon from network 702. The beacon includes a backhaul status IE indicating that network 702 has lost its backhaul connection. Since node 704 is a critical node, it continues to listen to additional beacons to find a network with an available backhaul connection.

[0046] At 720, the backhaul connection of the PAN corresponding to the mesh network 706 is available. At 722, the border router of the network 706 transmits the availability of the backhaul connection to the network. In one example, the border router sends a beacon with a backhaul status IE, which indicates that the backhaul connection is available. At 724, the node 704 receives the beacon from the network 706. Since the beacon from the network 706 indicates that the backhaul connection is available, the node 704 determines that it will try to join the network 706. The node 704 and the network 706 exchange messages 726, 728 at layer 2. The message exchange may include an association request and an association response message. Other types of message exchanges are also possible. Once joined at layer 2, the node 704 and the network 706 perform another message exchange at layer 3. For example, the node 704 can send a DAO message indicating that it is a key node, and the nodes within the network 706 can respond with a DAO-ACK message.

[0047] At 734, the backhaul connection of network 706 becomes unavailable. Then, at 736, the border router of network 706 communicates the loss of the backhaul connection to the network. At 738, a beacon from network 706 indicates that the backhaul connection of network 706 is unavailable. In response to receiving the beacon, node 704 begins searching for a new PAN at 740.

[0048] although Figure 7 Beacons are used to transmit backhaul status information, but other implementations may use a different type of message, including but not limited to another type of layer 2 message or a proprietary frame.

[0049] Example Node

[0050] Figure 8 An exemplary node 800 is illustrated. The node may include a processor 802, a memory 804, and a transceiver device 820, all communicatively coupled via a bus 806. The components of the node 800 may be powered by an A / C power source or a low energy source, such as a battery (not shown). The transceiver device 820 may include (or be communicatively coupled to) an antenna 808 for communicating with other nodes. In some examples, the transceiver device is a radio frequency ("RF") transceiver for wirelessly transmitting and receiving signals.

[0051] The processor may include a microprocessor, an application specific integrated circuit ("ASIC"), a state machine, a field programmable gate array ("FPGA"), or other suitable computing device. The processor may include any number of computing devices and may be communicatively coupled to a computer readable medium, such as memory 804. The processor may execute computer executable program instructions or access information stored in memory to perform operations, such as those described herein. The instructions may include processor-specific instructions generated by a compiler and / or interpreter from code written in any suitable computer programming language. When the instructions (such as those provided in critical path module 814) are executed, they may configure the node to perform any of the operations described herein. Although in Figure 8 The processor, memory, bus, and transceiver devices are depicted as separate components that communicate with each other, but other implementations are possible. The systems and components discussed herein are not limited to any particular hardware architecture or configuration.

[0052] Although the subject matter has been described in detail with respect to certain aspects of the subject matter, it should be appreciated that those skilled in the art can readily generate changes, modifications, and equivalents to these aspects after gaining an understanding of the foregoing. Therefore, it should be understood that the present disclosure has been presented for purposes of illustration and not limitation, and the present disclosure does not exclude the inclusion of such modifications, variations, and / or additions to the subject matter, as would be apparent to one of ordinary skill in the art.

Claims

1. A node added to a network, comprising: Processing equipment; A network interface capable of communicating over a network; as well as Memory configured by critical path modules, The execution of the critical path module configures the node to: receiving a layer 3 message from a second node identifying a critical path and determining that the node is on the critical path, wherein the critical path includes a critical node and at least a second node, the critical node requiring a backhaul connection; determining a status of a backhaul connection between the first PAN and the central system; When the backhaul connection is unavailable, generating a first layer 2 message having a backhaul status information element (IE) indicating that the backhaul connection is unavailable; Transmitting the first layer 2 message; determining an updated status of a backhaul connection between the first PAN and the central system; When the backhaul connection is available, generating a second layer 2 message having a backhaul status IE indicating that the backhaul connection is available; Transmitting layer 2 messages; as well as In response to a change in the critical path in the network, a state indicating that the node is on the critical path is updated.

2. The node of claim 1, wherein execution of the critical path module further configures the node to determine a status of a backhaul connection between the first PAN and the central system by evaluating a backhaul status IE from a received third layer 2 message.

3. The node of claim 2, wherein execution of the critical path module further configures the node to: When the Backhaul Status IE from the received Layer 3 2 message indicates that the backhaul connection is not available, another PAN is searched.

4. The node of claim 1, wherein execution of the critical path module further configures the node to determine a status of a backhaul connection between the first PAN and a central system by determining whether the node is connected to a time source.

5. The node of claim 1, wherein execution of the critical path module further configures the node to: after transmitting the first layer 2 message, receive a second layer 3 message from a second node, wherein the second layer 3 message indicates that the second node is no longer on the critical path.

6. The node of claim 1, wherein the layer 3 message is a DAO message and the first layer 2 message is a beacon.

7. A method performed by a node, comprising: receiving a layer 3 message from a second node identifying a critical path and determining that the node is on the critical path, wherein the critical path includes a critical node and at least a second node, the critical node requiring a backhaul connection; determining a status of a backhaul connection between the first PAN and the central system; When the backhaul connection is unavailable, generating a first beacon having a backhaul status information element (IE) indicating that the backhaul connection is unavailable; transmitting a first beacon; determining an updated status of a backhaul connection between the first PAN and the central system; When the backhaul connection is available, generating a second beacon having a backhaul status IE indicating that the backhaul connection is available; transmitting a second beacon; as well as In response to a change in the critical path in a network, a state indicating that the node is on the critical path is updated.

8. The method of claim 7, wherein determining the status of the backhaul connection between the first PAN and the central system comprises: The Backhaul Status IE from the received beacon for the first PAN is evaluated.

9. The method according to claim 8, further comprising: When the Backhaul Status IE from the received beacon for the first PAN indicates that the backhaul connection is not available, another PAN is searched for.

10. The method of claim 7, wherein determining a status of a backhaul connection between the first PAN and the central system comprises: Determine whether the node is connected to an NTP server.

11. The method according to claim 7, further comprising: After transmitting the first beacon, a second layer 3 message is received from the second node, wherein the second layer 3 message indicates that the second node is no longer on the critical path.

12. The method of claim 7, wherein the layer 3 message is a DAO message.

13. A method for enabling a node to join a network, comprising: receiving a first beacon, wherein the first beacon includes a backhaul status information element (IE) indicating a status of a backhaul connection associated with a first PAN; analyzing the backhaul status IE in the first beacon to determine whether a backhaul connection associated with the first PAN is available; When the backhaul status IE in the first beacon indicates that the backhaul connection associated with the first PAN is unavailable, continuing to listen for additional beacons; receiving a second beacon, wherein the second beacon includes a backhaul status IE indicating a status of a backhaul connection associated with a second PAN; analyzing the backhaul status IE in the second beacon to determine whether a backhaul connection associated with the second PAN is available; When the backhaul status IE in the second beacon indicates that a backhaul connection associated with the second PAN is available, joining the second PAN; as well as In response to a change in a critical path in the first PAN or the second PAN, a status of one or more nodes in the first PAN or the second PAN is updated, the status indicating whether the node is located on the critical path.

14. The method according to claim 13, further comprising: after joining the second PAN, receiving a third beacon, wherein the third beacon includes a backhaul status IE indicating a status of a backhaul connection associated with the second PAN; generating a fourth beacon including a backhaul status IE indicating a status of a backhaul connection associated with the second PAN; and A fourth beacon is transmitted.

15. The method according to claim 14, further comprising: When the backhaul status IE in the third beacon indicates that the backhaul connection of the second PAN is not available, then beacons received from different PANs are evaluated to determine whether a backhaul connection associated with the different PAN is available.

16. The method according to claim 13, further comprising: After joining the second PAN, a layer 3 message is transmitted to the parent node, indicating that the node is a critical node requiring a backhaul connection.

17. The method according to claim 16, further comprising: receiving a layer 3 message by the parent node, and The parent node is identified as being on a critical path.

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