Method for migrating nodes in distributed network to centralized network

Abstract

A method (500) for migrating two or more nodes (400) in a distributed wireless network to a centralized wireless network, the method (500) comprising the steps of: receiving (S501), by a first bridge device (200), configuration information about the distributed wireless network from a second bridge device (300) in the distributed wireless network; accessing (S502), by the first bridge device (200), the distributed wireless network based on the received configuration information; querying (S503), by the first bridge device (200), two or more nodes (400) in the distributed wireless network to collect topology information among the two or more nodes (400); determining (S504), by the first bridge device (200), a sequence list for requesting two or more nodes (400) to join the centralized wireless network based on the topology information; and notifying (S505) the two or more nodes (400) to join the centralized wireless network according to the sequence list.

Description

Technical Field

[0001] The present invention relates to the field of wireless communications. More specifically, various methods, devices and systems related to migrating a node between two different wireless networks are disclosed herein. Background Art

[0002] Zigbee, Thread, and Bluetooth Mesh are examples of wireless networks targeting IoT applications such as lighting and building automation. They provide low-latency, low-rate services that enable messages to be delivered between, for example, a light switch and one or more luminaires. Mesh networks provide great flexibility and scalability to the system. However, on the other hand, centralized Zigbee networks provide improved security and control over the network, which is also attractive in many applications. Therefore, there is a need to migrate existing distributed networks to centralized networks in a reliable manner.

[0003] Some communication standards, such as the Zigbee standard, support both distributed and centralized network architectures. Such standards may also define how distributed and centralized networks may be formed from scratch. However, there is no clearly defined method to move an existing distributed network to a centralized network without having to redeploy the entire network. Furthermore, it may also be desirable that such a transition be instantaneous with reduced impact on network functionality. Summary of the invention

[0004] In a distributed network, some nodes are end nodes or leaf nodes that rely on other nodes (router nodes or parent nodes) to relay messages to them. One problem that may arise during the transition from a distributed network to a centralized network is that if those router nodes or parent nodes leave the distributed network earlier than the end nodes and / or leaf nodes, then those end nodes and / or leaf nodes may lose connection with the distributed network without notification about the transition and then become unreachable.

[0005] The inventors have realized that it would be beneficial to standardize the network migration procedure by taking into account topology information.More specifically, the object of the invention is achieved by a method as claimed in claim 1 and a bridge device as claimed in claim 11 .

[0006] According to a first aspect of the present invention, a method for migrating two or more nodes in a distributed wireless network to a centralized wireless network is provided. The method comprises the following steps: a first bridge device receives configuration information about a distributed wireless network from a second bridge device in the distributed wireless network; the first bridge device accesses the distributed wireless network based on the received configuration information; the first bridge device queries two or more nodes in the distributed wireless network to collect topology information among the two or more nodes; the first bridge device determines a sequence list for requesting two or more nodes to join the centralized wireless network based on the topology information; and notifies the two or more nodes to join the centralized wireless network according to the sequence list; wherein the sequence list is arranged to allow a first node among the two or more nodes to join the centralized wireless network earlier than a second node among the two or more nodes when the first node receives a message from another bridge device via a relay of a second node in the distributed wireless network.

[0007] The configuration information about the distributed wireless network may be related to a network ID of the distributed network, an operating channel of the distributed network, or another network parameter related to the distributed network. The configuration information is used to assist the first bridge device to access the distributed network.

[0008] Topology information may be gathered by obtaining neighbor information associated with each individual node, such as its list of neighbors with one-hop direct links, output power used to establish a link with a neighbor node, power received from a neighbor node, or link quality information associated with a link with another node.

[0009] Thus, topology information may be related to the physical deployment of nodes in the system. Topology information may also be related to the network configuration of the distributed network, such as which nodes are assigned as router nodes and which nodes are assigned as end nodes or non-routing nodes. For example, an end node may receive information from a router node, but may not receive information from another end node.

[0010] In a preferred embodiment, the sequence list is arranged to allow a first node of two or more nodes to join the centralized wireless network earlier than a second node of the two or more nodes when the first node receives a message from a bridge device via a relay of a second node in the distributed wireless network.

[0011] The sequence list is arranged to avoid the situation where a critical node (e.g., the only link node between two sub-parts of the network) moves to the new centralized network earlier than other nodes, which would make some nodes in the distributed network unreachable and unable to be informed about the transition. For example, a router node or parent node would leave the distributed network later than the end nodes or child nodes that depend on it for access to the distributed network.

[0012] Advantageously, the method further comprises the step of opening, by the first bridge device, the centralized wireless network for the node to join.

[0013] This step can be implemented by the first bridge device before or after joining the distributed wireless network, depending on whether the first bridge device can be in both networks simultaneously, such as via two radios or via a single radio in a time-sharing manner. Alternatively, the first bridge device can turn on the centralized wireless network after notifying two or more nodes to join the centralized wireless network. And then, the first bridge device will also notify the two or more nodes to join after a certain delay, which allows the centralized wireless network to prepare for the node to join.

[0014] Advantageously, the method further comprises the step of providing, by the second bridge device, information relating to the two or more nodes to the first bridge device.

[0015] The second bridge device may provide the first bridge device with information related to each node to further assist the first bridge device in setting up a centralized network and establishing connections with each node.

[0016] Alternatively, the method further comprises the step of querying, by the first bridge device, two or more nodes on the distributed wireless network to collect information related to the two or more nodes.

[0017] As the first bridge device joins the distributed network, it can collect such information itself. However, since the second bridge device may have collected such information during its normal data communication in the distributed network, it may be more efficient for the second bridge device to provide such information directly to the first bridge device.

[0018] In one example, the information related to the two or more nodes includes at least one of addresses, configuration parameters, and status information related to the two or more nodes.

[0019] Advantageously, the method further comprises the step of providing, by the first bridge device, one or more parameters related to the centralized wireless network to the two or more nodes.

[0020] This step may be combined with the step of requesting two or more nodes to join the centralized wireless network.

[0021] The one or more parameters may be related to a network ID of the centralized network; an operating channel of the centralized network or another network parameter.

[0022] In one example, the method further includes the step of restoring a node of the two or more nodes in the centralized wireless network to a previous state of the node in the distributed wireless network.

[0023] By understanding the configuration, settings, state, or scenario of individual nodes in the distributed network, the first bridge device or a new bridge device can restore the node to the previous configuration, settings, state, or scenario after the node is moved to the new centralized network, which further enhances the smooth transition.

[0024] In another example, the method further includes the steps of generating a link key for a node among the two or more nodes in the centralized wireless network based on the obtained information related to the two or more nodes; and notifying the node of the link key.

[0025] Upon receiving information related to a single node, such as an identifier or address of the node, the first bridge device may generate an end-to-end link key for the single node. The end-to-end link key may be used to improve the security of end-to-end communications in a centralized network.

[0026] This step may be performed by a first bridge device of the centralized network, such that the first bridge device informs the various nodes of their dedicated link keys.

[0027] Advantageously, at least one of the distributed wireless network and the centralized wireless network is according to the Zigbee standard.

[0028] The Zigbee standard is widely adopted in home automation and lighting control applications. The Zigbee network layer natively supports both star and tree networks as well as general mesh networking. Powerful topology control provides great flexibility in control systems, especially for reaching destination nodes far away from the source node using direct links.

[0029] ZigBee specifies three different device types: ZigBee Coordinator (ZC), ZigBee Router (ZR), and ZigBee End Device (ZED). These three devices play different roles in a ZigBee network. ZigBee Routers (ZR) pass data between devices and / or coordinators. Zigbee End Devices (ZED) provide only basic functionality. ZEDs are leaf nodes. They communicate only through their parent node, and unlike router devices, they cannot relay messages to other nodes. They do not participate in any routing. End devices rely on their parent routers to send and receive messages. With respect to IEEE802.15.4, ZC and ZR are full function devices (FFD), while ZED is a reduced function device (RFD).

[0030] Thus, topology information among two or more nodes in a distributed wireless network may be determined by a combination of the physical locations of the nodes, the functionality supported by the nodes, and the types of roles they play in the distributed network.

[0031] Optionally, the first bridge device and the second bridge device are physically co-located. For example, the first bridge device and the second bridge may be deployed adjacent to each other, such as within direct wireless communication range. It may also be the case that the first bridge device and the second bridge device are co-located such that the first bridge device will be replaced by the second bridge device after migration. It may also be physically possible that the first bridge device and the second bridge device are the same bridge device. It also applies to the case where an existing bridge device has the ability to transition to a centralized network through a firmware update. All of these steps will simply be performed on the same bridge device to move its network from a distributed topology to a centralized topology.

[0032] Advantageously, the first bridge device and the second bridge device have a further communication channel connected to each other which does not belong to the distributed wireless network or the centralized wireless network.

[0033] The additional communication channel may be a wired channel or a wireless channel. For example, the first bridge device and the second bridge device may be connected via an IP network (e.g., Ethernet). The first bridge device and the second bridge device may also be connected via a Wi-Fi network, a BLE link, or a 4g / 5G cellular link.

[0034] According to a second aspect of the present invention, a bridge device is provided. A bridge device for migrating two or more nodes in a distributed wireless network to a centralized wireless network, the bridge device comprising a communication interface, configured to receive configuration information about the distributed wireless network from another bridge device in the distributed wireless network; a radio, configured to access the distributed wireless network based on the received configuration information; query two or more nodes in the distributed wireless network to collect topology information among the two or more nodes; a controller, configured to determine a sequence list for requesting the two or more nodes to join the centralized wireless network based on the topology information; wherein the radio is also configured to notify the two or more nodes to join the centralized wireless network according to the sequence list; wherein the sequence list is arranged to allow a first node among the two or more nodes to join the centralized wireless network earlier than a second node among the two or more nodes when the first node receives a message from another bridge device via a relay of a second node in the distributed wireless network.

[0035] The whole procedure of migrating nodes to the centralized network can be initiated by the new bridge device of the centralized network, for example, it first requests to join the existing distributed network by obtaining configuration parameters from the old bridge device of the distributed wireless network. And then, the new bridge device of the centralized network or the existing bridge device in the distributed wireless network can take the main responsibility of arranging a smooth transition. In a preferred example, the new bridge device performs the main steps during the procedure.

[0036] The topology information is used to determine a sequence list to ensure that no unreachable nodes are left in the distributed network during the transition period. The topology information may be collected by the new bridge device by querying nodes in the distributed network. Alternatively, it is also possible that during earlier data communications in the distributed network, the existing bridge device regularly collects topology information, and then the existing bridge device may directly provide such topology information to the new bridge device. Based on the topology information, the new bridge device determines a sequence list and requests nodes to join the centralized network according to the sequence list.

[0037] Existing bridge devices can also provide further information related to individual nodes, such as their addresses, configuration parameters, or the state of the node in the distributed network. Such information can help new bridge devices restore nodes to their previous state or configuration after they have been moved to a new centralized network. This information can also be used to generate dedicated link keys to secure end-to-end communication links.

[0038] Beneficially, when the first node receives a message from another bridge device via relaying of a second node in the distributed wireless network, the sequence list is arranged to allow a first node of the two or more nodes to join the centralized wireless network earlier than a second node of the two or more nodes.

[0039] In one option, the radio is further configured to open the centralized wireless network for the nodes to join after notifying two or more nodes to join the centralized wireless network according to the sequence list.

[0040] In this option, the first bridge device will open the centralized wireless network after notifying two or more nodes to join the centralized wireless network. Therefore, the first bridge device will also notify two or more nodes to join after a certain delay, which allows the centralized wireless network to prepare for the node to join.

[0041] In another option, the radio is further configured to open a centralized wireless network for the node and operate on the centralized wireless network and the distributed wireless network in a time-sharing manner.

[0042] As disclosed above, the first bridge device may open the centralized wireless network before it initiates the transition procedure. This may be achieved if the first bridge device can remain in both the distributed network and the centralized network simultaneously, such as by incorporating two radios in the first bridge device, or by using a single radio of the first bridge device in a time-sharing manner between the two networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In the drawings, similar reference numerals are used throughout the different Figure 1Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0044] Figure 1 A possible system setup is shown;

[0045] Figure 2 A flow chart illustrating a method for migrating two or more nodes in a distributed wireless network to a centralized wireless network;

[0046] Figure 3 A block diagram showing a bridge device for use in a distributed wireless network; and

[0047] Figure 4 An example of a bridge device is illustrated. DETAILED DESCRIPTION

[0048] The embodiments set forth below represent information that enables those skilled in the art to practice the embodiments. When reading the following description with reference to the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize the application of these concepts not specifically mentioned herein. It should be understood that these concepts and applications fall within the scope of the present disclosure.

[0049] For wireless communications, a distributed network topology offers improved flexibility and scalability. However, it can also bring the risk of compromised security. Taking Zigbee as an example, there are well-known weaknesses in distributed Zigbee networks, especially during the joining process. In order to provide better security, it is attractive to move to a centralized network with additional secure joining mechanisms. Although the Zigbee standard defines how distributed and centralized networks can be formed from scratch, there is no clearly defined method to move an existing distributed network to a centralized network without having to redeploy the entire network. From a user experience perspective, it is important to be able to make this transition with minimal user intervention and network disruption. Preferably, this transition can be achieved instantly.

[0050] One approach is to use the Zigbee Commissioning Cluster (ZCC), which essentially defines messages that can be sent to individual nodes in the network, with information such as the Zigbee PAN-ID of the centralized network to join, the extended PAN ID, the network and link keys, etc. It also defines messages that instruct a node to reboot and join the new network. Upon reboot, the node joins the new network using the more secure centralized join mechanism defined in Zigbee, and also "realizes" that it is now part of a centralized network.

[0051] Another approach is to define custom messages that essentially do a subset of what ZCC does. In its simplest form, a simple restart and rejoin message can be sent to a node, which will cause the node to search for a new network, and then find the centralized network and join it.

[0052] Regardless of which method is used, it is necessary to push nodes to leave the existing distributed network to join the new centralized network. Known methods demonstrate how to move a single node from a distributed network to a centralized network. However, there is still a lack of a process / method to reliably migrate every node in the network to a centralized one. As an example, a problem that may arise is that if a key node (e.g., the only link node between two sub-parts of the network) moves to the new centralized network earlier than other nodes, this will make some nodes in the distributed network unreachable and unable to be notified about the transition. One approach is that the extended PAN-ID, PAN-ID, network key, etc. used for both the existing distributed network and the new centralized network can remain the same. However, this approach may cause some unexpected confusion to the nodes.

[0053] The present invention solves this problem in a more general way, where the centralized network can be completely independent with refreshed network parameters such as PAN-ID, network keys, etc. This also provides improved security, as the new centralized network can freely choose the refreshed new keys, and thus the new centralized network starts up just like it was built from scratch.

[0054] Figure 1 A possible system setup of an existing bridge device and a new bridge device is shown. In this example, the new bridge device can be located away from the existing bridge device and connected via an additional communication channel that is not part of the distributed network or the centralized network. The additional communication channel can be based on a wireless communication protocol or a wired communication protocol.

[0055] According to the Zigbee protocol, a conventional mechanism for migrating nodes from an existing distributed network to a new centralized network is to pass the existing Zigbee network parameters (PAN-ID, network key, etc.) and other information related to the distributed network to the new bridge device 200. This information may be encrypted and passed through a wired connection (such as via an IP network) or a wireless connection between the existing bridge device 300 and the new bridge device 200. The wireless connection may be based on another wireless communication protocol different from the existing distributed network or the new centralized network, such as Wi-Fi, BLE, or 4G / 5G cellular.

[0056] Figure 1It also highlights that problems may arise if the existing bridge device 300 would naively instruct the nodes (A to E) to switch sequentially to join the new bridge device 200 in centralized mode (by issuing Zigbee commissioning cluster commands or simpler custom commands). Once node C leaves the distributed network, nodes D and E will no longer be reachable.

[0057] Therefore, a new solution is needed to solve this problem. In order to assist the new bridge device to join the distributed network, the existing bridge device can send the network parameters related to the distributed network (PAN-ID, extended PAN-ID, channel, network key, etc.) directly to the new bridge device via the communication interface. It is also possible that the existing bridge device opens the distributed network for any node to join. Optionally, in this step, the existing bridge device can also send a list of nodes' identification or addresses (e.g., IEEE addresses), their existing / current settings / status / conditions (e.g., for lighting, it can be on / off status, color temperature condition, etc.) to the new bridge device. As an example of implementing the proposed solution, the steps involved may be as follows.

[0058] a) Thus, the new bridge device 200 can perform a regular join (if the existing bridge device 300 opens the network for joining) or a secure join (if the existing bridge device 300 has provided network parameters related to the distributed network). At the end of this step, the new bridge device 200 joins the existing distributed network.

[0059] b) The new bridge device 200 can send signals (ping) to different nodes to obtain topology information based on the identification / address list received in step a). The new bridge device 200 can also broadcast queries to nodes in the distributed network to collect topology information. The topology information may include its links / neighbors, transmit / receive power, etc. Based on the topology information, the existing bridge device 300 or the new bridge device 200 can derive an overview of the network topology among multiple nodes. If the new bridge device 200 receives the identification / address list based on the response from the node in step a), the new bridge device 200 can also derive whether there are certain nodes that it cannot reach. This is a beneficial byproduct that can help users realize that the location of the new bridge device 200 is not optimal given the physical layout of the system.

[0060] c) The new bridge device 200 may randomly select a PAN-ID, extended PAN-ID, operating frequency channel, network key or other network parameters for the centralized network it will form.

[0061] d) The new bridge device 200 may derive a sequence list based on the topology information obtained in step b). Then, the new bridge device 200 may request the node to leave the existing distributed network according to the sequence list. Figure 1 , the new bridge device 200 will first ask light bulbs A and D to leave, followed by light bulb C, and then light bulbs B and E. This order will ensure that all nodes in the network receive the request to leave the existing network. Before or in conjunction with the request, the new bridge device 200 may also send the network parameters selected in step c) to the nodes (one option is to send via the use of ZCC messages, if implemented).

[0062] e) Once all nodes have been sent a request, or a ZCC message or another custom message for the same purpose, the new bridge device 200 leaves the distributed network itself and forms a centralized network using the parameters it selected in step d). The new bridge device 200 then opens the centralized network for nodes to join. The new bridge device 200 uses the information obtained in the previous steps to successfully enable the nodes to join in centralized mode. For example, if the new bridge device 200 also receives information related to the nodes in step a) from the existing bridge device 300, it can help it obtain information derived from the installation code (possibly from the backend server) to obtain the link key, so that these nodes can successfully join the centralized network.

[0063] f) Some radio chip vendors may offer a feature where a node can be part of two networks simultaneously. The new bridge device 200 may have this feature. In this case, since the bridge device can be on two separate networks, it can concurrently issue leave requests to the distributed network while allowing joins on its own centralized network.

[0064] g) Optionally, once all nodes have joined the centralized network, the new bridge device 200 may use the node-related information obtained in step a) to return the nodes to their previous state (on / off state, color temperature state, etc.).

[0065] Figure 2A flow chart of a method 500 for migrating two or more nodes in a distributed wireless network to a centralized wireless network is shown. The method 500 includes the following steps: in step S501, a first bridge device 200 receives configuration information about a distributed wireless network from a second bridge device 300 in the distributed wireless network; in step S502, the first bridge device 200 accesses the distributed wireless network based on the received configuration information; in step S503, the first bridge device 200 queries two or more nodes 400 in the distributed wireless network to collect topology information among the two or more nodes 400; in step S504, the first bridge device 200 determines a sequence list for requesting the two or more nodes 400 to join the centralized wireless network based on the topology information; and in step S505, the two or more nodes 400 are notified to join the centralized wireless network according to the sequence list.

[0066] Figure 3 A block diagram of a bridge device 200 is shown. As a basic setting, the bridge device 200 includes a communication interface 210, a radio 220, and a controller 230. The communication interface 210 is configured to receive configuration information about the distributed wireless network from another bridge device in the distributed wireless network. The radio 220 is configured to access the distributed wireless network based on the received configuration information; and query two or more nodes 400 in the distributed wireless network to collect topology information among the two or more nodes 400. The controller 230 is configured to determine a sequence list for requesting the two or more nodes 400 to join the centralized wireless network based on the topology information. The radio is also configured to notify the two or more nodes 400 to join the centralized wireless network according to the sequence list.

[0067] As an example, the present invention can be implemented by Figure 4. The network transmission module can be implemented in the controller of the bridge device. In the new bridge device 200, the network transmission module obtains configuration information related to the existing distributed network from the existing bridge device 300 in the above step a), and therefore, the network transmission module can control the radio of the new bridge device 200 to perform steps ab), such as joining the distributed network and querying the node for topological information. It is also possible that the network transmission module obtains topological information from the existing bridge device 300, which has collected such information during conventional communication with the node. Based on the collected topological information, the network transmission module calculates in step d) to generate an appropriate sequence list for migrating the node to the new bridge device. Then, the network transmission module continues to monitor the radio to send requests to all nodes on the distributed network according to the determined sequence list. Once all requests have been sent, the network transmission module controls the radio to switch from the distributed network to the new centralized network and waits for the node to join.

[0068] Note that the present invention is equally applicable to situations where an existing bridge device has the capability to transition to a centralized network through a firmware update. All of these steps will simply be performed on the same bridge device to move its network from a distributed topology to a centralized topology.

[0069] The method according to the present invention can be implemented on a computer as a computer-implemented method, or in dedicated hardware, or in a combination of both.

Claims

1. A method (500) for migrating two or more nodes (400) in a distributed wireless network to a centralized wireless network, the method (500) comprising the following steps: - receiving (S501) configuration information about the distributed wireless network from a second bridge device (300) in the distributed wireless network by a first bridge device (200); - The first bridge device (200) accesses (S502) the distributed wireless network based on the received configuration information; - querying (S503) two or more nodes (400) in the distributed wireless network by the first bridge device (200) to collect topology information among the two or more nodes (400); - determining (S504) by the first bridge device (200) a sequence list for requesting the two or more nodes (400) to join the centralized wireless network based on the topology information; - notifying (S505) the two or more nodes (400) to join the centralized wireless network according to the sequence list; The sequence list is arranged to allow a first node among the two or more nodes (400) to join the centralized wireless network earlier than a second node among the two or more nodes (400) when the first node receives a message from a bridge device via a relay of a second node in the distributed wireless network.

2. The method (500) of claim 1, further comprising: - The first bridge device (200) opens the centralized wireless network for the node (400) to join.

3. The method (500) according to claim 1 or 2, further comprising: - providing information related to the two or more nodes (400) to the first bridge device (200) by the second bridge device (300).

4. The method (500) according to claim 1 or 2, further comprising: - querying two or more nodes (400) on the distributed wireless network by the first bridge device (200) to collect information related to the two or more nodes (400).

5. The method (500) according to claim 3 or 4, wherein the information related to the two or more nodes (400) includes at least one of addresses, configuration parameters and status information related to the two or more nodes (400).

6. The method (500) according to any one of the preceding claims 2-5, further comprising: - providing, by the first bridge device (200), one or more parameters related to the centralized wireless network to the two or more nodes (400).

7. The method (500) according to any one of the preceding claims 3-6, further comprising: - restoring a node among two or more nodes (400) in the centralized wireless network to a previous state of the node in the distributed wireless network.

8. The method (500) according to any one of the preceding claims 3-7, further comprising: - generating a link key for a node in the two or more nodes (400) in the centralized wireless network based on the obtained information related to the two or more nodes (400); and - Notify the node of said link key.

9. The method (500) according to any of the preceding claims, wherein at least one of the distributed wireless network and the centralized wireless network is according to the Zigbee standard.

10. The method (500) according to any one of the preceding claims, wherein the first bridge device (200) and the second bridge device (300) have a further communication channel connected to each other which does not belong to the distributed wireless network or the centralized wireless network.

11. A bridge device (200) for migrating two or more nodes (400) in a distributed wireless network to a centralized wireless network, the bridge device (200) comprising: - a communication interface (210) configured to receive configuration information about the distributed wireless network from another bridge device in the distributed wireless network; - a radio (220) configured to: o accessing the distributed wireless network based on the received configuration information; o querying two or more nodes (400) in the distributed wireless network to collect topology information among the two or more nodes (400); - A controller (230) configured to: o determining a sequence list for requesting the two or more nodes (400) to join the centralized wireless network based on the topology information; wherein the radio is further configured to notify the two or more nodes (400) to join the centralized wireless network according to the sequence list; The sequence list is arranged to allow a first node among the two or more nodes (400) to join the centralized wireless network earlier than a second node among the two or more nodes (400) when the first node receives a message from another bridge device via a relay of a second node in the distributed wireless network.

12. The bridge device (200) of claim 11, wherein the radio (220) is further configured to open the centralized wireless network for the nodes (400) to join after notifying the two or more nodes (400) to join the centralized wireless network according to the sequence list.

13. The bridge device (200) of claim 11, wherein the radio (220) is further configured to open the centralized wireless network for a node (400) and operate on both the centralized wireless network and the distributed wireless network in a time-sharing manner.

Images