WO2022148695A1

WO2022148695A1 - A method of, a node device and a system for relaying a message in a network comprising at least two mesh networks

Info

Publication number: WO2022148695A1
Application number: PCT/EP2021/087744
Authority: WO
Inventors: Changjie Wang; Lei Feng; Jaya KARTHIK
Original assignee: Signify Holding B.V.
Priority date: 2021-01-06
Filing date: 2021-12-28
Publication date: 2022-07-14

Abstract

A method of relaying a message in a network comprising at least two mesh networks each comprising a plurality of operatively interconnected node devices is disclosed. A number of node devices within each mesh network bordering at least one of the other mesh networks is designated as boundary node devices by a network backend server. Each node device within each mesh network is provisioned with a network credential specific to the mesh network comprising the node device and each boundary node device is further provisioned with further network credential(s) specific to the mesh network(s) bordering the mesh network comprising the boundary node device. The method is performed by a boundary node device and comprises the steps of: receiving a message from a node device within a mesh network comprising the boundary node device; determining that the message is intended to at least one of the other mesh networks having node devices supposed to receive the message and bordering the mesh network comprising the boundary node device, and relaying the message a number of times, the number being equal to a number of mesh networks having node devices supposed to receive the message, the message relayed each time being encrypted with a respective network credential of a mesh network having node devices supposed to receive the message.

Description

Title

A method of, a node device and a system for relaying a message in a network comprising at least two mesh networks.

Technical Field

The present disclosure generally relates to the field of wireless mesh network and, more specifically, to a method of, a node device and a system for relaying a message in a network comprising at least two mesh networks, each mesh network comprising a plurality of operatively interconnected node devices.

Background

Electric or electronic devices, such as lighting devices and Internet of Things, loT, devices, and devices supporting enhanced Machine-Type Communication, eMTC, for example, all of which comprise data communication capabilities, are frequently deployed in networks comprised of a plurality of interconnected devices.

These devices, generally called node devices or terminal devices, may operate a short range communication interface and a long range communication interface. The short range communication interface, such as a transceiver module, is configured for communication between node devices only, which is also called inter node device communication and normally time critical. The long range communication interface, such as a network adapter or a transceiver module, is configured for data exchange with remote devices, such as a backend server.

The short range communication interface may operate in accordance with a network protocol for exchanging data by networked devices or nodes, such as designated ZigBee™, Bluetooth™, as well as WiFi based protocols for wireless networks, and wired bus networks such as DALI™ (Digital Addressable Lighting Interface), DSI (Digital Serial Interface), DMX (Digital Multiplex), KNX (and KNX based systems), and proprietary communication technologies and protocols, for example. The long range communication interface may operate in accordance with a wireless mobile communication standard, such as designated 2G/3G/4G/5G cellular communication, and other long-range wireless communication technologies like Long Range Wide Area Network, LoRaWAN, and Narrowband loT, NB-loT, or proprietary communication technologies, and/or a wired data exchange communication technology, for example.

One particular networking topology for connecting a plurality of node devices is referred to as mesh network, in which a node device may be connected directly, dynamically and non-hierarchically to many other node devices within its communication range, with the node devices cooperating with one another to efficiently route data between the node devices.

In practice, a mesh network may support a limited number of node devices in one network, so as to ensure good performance of the network. For example, Bluetooth mesh networking normally supports hundreds of nodes in one network for indoor scenarios.

Based on such a limitation, an application involving a huge number of node devices, such as an outdoor lighting system with tens to hundreds thousands of lighting devices, for example, can be implemented using mesh networking only by creating and managing a mesh network comprising several independent mesh networks.

Node devices in a mesh network, after being installed and powered on, are configured or provisioned by for example a provisioner, which joins each node device into the mesh network by securely distributing network information, including a network credential common to all node devices, a device credential unique to each device, and one or more application credentials to node devices participating in one or more applications.

Messages may be transmitted from one node device to another node device in the same mesh network by flooding, which is the forwarding by a relay node of a packet from any node to every other node connected to the relay node except the node from which the packet arrived. The messages are encrypted by the network credential and the application credential. Each node device in the mesh network with a relay function enabled can relay the message if the message may be successfully decrypted and authenticated using the network credential at the network layer, and, for managed flooding used in Bluetooth mesh network, when a predefined time to live, TTL, is still valid.

Each mesh packet includes an identifier that indicates which network the mesh packet belongs to. As node devices in different mesh networks are provisioned with different network credentials, a node device in one mesh network cannot decrypt or authenticate mesh packets from an other mesh network, and will therefore not relay such packets from the other mesh network. The different mesh networks are in this sense isolated from each other.

This will create problems for applications involving a large number of node devices managed as more than one mesh networks and requiring messages from one mesh network to be relayed by node devices in another mesh network. As an example, lighting on demand service in a lighting system designed for a long street with thousands of lighting devices deployed as several mesh networks will not be able to run as smoothly, as a message from a last lighting device in one mesh network will not be able to trigger neighbouring lighting devices in a neighbouring mesh network. This will degrade user experience and possibly cause safety issues.

Accordingly, there is a need for improved method of relaying a message in a system or network comprising several mesh networks each comprising a plurality of operatively interconnected node devices such that seamless relay of messages across different mesh networks is possible.

Summary

In a first aspect of the present disclosure, there is provided a method of relaying a message in a network comprising at least two mesh networks, each mesh network comprising a plurality of operatively interconnected node devices, a number of node devices within each mesh network bordering at least one of the other mesh networks being designated as boundary node devices by a network backend server, each node device within each mesh network provisioned with a network credential specific to the mesh network comprising the node device, each boundary node device further provisioned with further network credential(s) specific to mesh network(s) bordering the mesh network comprising the boundary node device, the method comprising the steps of: receiving, by a boundary node device, a message from a node device within a mesh network comprising the boundary node device; determining, by the boundary node device, that the message is intended to at least one of the other mesh networks having node devices supposed to receive the message and bordering the mesh network comprising the boundary node device, and relaying, by the boundary node device, the message a number of times, the number being equal to a number of mesh networks having node devices supposed to receive the message, the message relayed each time being encrypted with a respective network credential of a mesh network having node devices supposed to receive the message.

A large-scale network may comprise a number of smaller mesh networks, the smaller mesh networks each comprising a plurality of operatively interconnected node devices are isolated from each other in terms of relaying of messages across the mesh networks, as a result of node devices within each mesh network being provisioned with a network credential specific to the mesh network only. Such isolation is undesirable and may cause various problems to applications requiring uninterrupted or seamless relaying of messages from one mesh network to a neighbouring mesh network.

It is the inventor’s insight that such isolation can be overcome by designating a number of node devices within each mesh network bordering at least another mesh network as boundary node devices and provisioning each boundary node device with multiple network credentials, including a network credential specific to a mesh network comprising the boundary node device and network credential(s) specific to other mesh network(s) bordering the mesh network comprising the boundary node device.

A boundary node device can therefore, upon receiving a message transmitted by a node device belonging to the mesh network comprising the boundary node device and determining that the message is intended not only to node devices within the mesh network comprising the boundary node device but also to node devices within other mesh networks bordering the mesh network comprising the boundary node devices, relay the message multiple times. In addition to relaying the message by encrypting the message with a network credential of the network having the boundary node device, the boundary node device each other time relays the message by encrypting the message using a network credential specific to a bordering mesh network. As a result, a node device in the bordering mesh network will be able to decrypt and authenticate the message with the right network credential, and thereafter process the message as needed.

Each other relay therefore guarantees that a node device in a bordering mesh network supposed to receive the message will receive the message and can then process the message accordingly based on the specific application, after authenticating and decrypting the message with the correct network credential.

The present disclosure therefore provides a novel method and security framework for managing a large-scale network, such as an outdoor lighting system composed of several small mesh networks, enabling seamless flooding communication across the small mesh networks and thus the related applications over the whole network system.

The multiple network credentials are provisioned to the boundary node devices during the network provisioning or configuring procedure. Thereafter, the boundary node devices in regular operation take an extra step to determine whether a received message is intended to multiple mesh networks, and relay the message multiple times if the message is supposed to be transmitted to node devices not only within its own network but also within other bordering mesh networks.

It can be contemplated that a number of boundary node devices in a mesh network is relatively small comparing to non-boundary or normal node in the same mesh network, therefore the method realises seamless flooding communication at the cost of a little bit extra computation and communication resources, which brings much benefits than burdens.

In an example of the present disclosure, a node device is designated as a boundary node device of a mesh network on the basis of at least one of a physical distance between the node device and a physical boundary of the mesh network, a number of node devices belonging to a bordering mesh network and within a communication range of the node device, and an application-dependent requirement.

As implied by the name “boundary” node device, a node device which is thus designated is physically close to the boundary. Therefore, a physical or geographical distance between a node device and a physical boundary of the mesh network may be used as a criterion for designating the node device as a boundary node device.

Another factor considered in designating the boundary node devices may be a number of node devices within a neighbouring or bordering mesh network and in the communication range of the boundary node devices. It can be easily understood that designating a node device having more node devices within a neighbouring or bordering mesh network in its communication range as a boundary node device is more advantageous and efficient as it can ensure that a message will be received by more node devices in bordering mesh networks.

Moreover, a number of boundary node devices may vary depending on detailed requirements of the related application. As an example, for the light on demand service with a requirement of “having four lights turned on ahead a moving object”, the last four lighting devices of a mesh network may be designated as boundary node devices. Flexibility and better control of the flooding communication may be achieved by taking into consideration application-dependent requirements.

It can be contemplated that the above criteria may be combined to achieve a better scheme for designating the boundary node devices in a mesh network.

In an example of the present disclosure, the physical distance between the node device and the physical boundary of the mesh network is determined by the network backend server on the basis of a plan view or a layout of the network.

As a plan view or a layout of a project for constructing the network comprising several mesh networks is always available and can be readily obtained for example from a backend server, the physical distance between the node device and the physical boundary of the mesh network comprising the node device can be easily determined, by for example simply viewing the plan view.

It can be contemplated by those skilled in the art that the physical distance may be determined by using more precise and complicated approaches, such as by using geographic location data obtained by a location detection device comprised or attached to the node device. In an example of the present disclosure, the application-dependent requirement comprises a number of node devices to be designated as boundary node devices.

As discussed above, the number of required boundary node devices may vary depending on the specific application run by the node devices in the mesh network. Selecting the number of boundary node devices based on the application allows the application and related service to be provided in a better controlled way, such as in terms of user experience.

In an example of the present disclosure, the determining, by the boundary node device, that the message is intended to at least one of the other mesh networks having node devices supposed to receive the message and bordering the mesh network comprising the boundary node device is made with reference to a target bordering network indication comprised in the message.

The target bordering mesh network indication is used to indicate which mesh network(s) is or comprises node devices supposed to receive the message. It can be contemplated by those skilled in the art that various coding methods can be used to define how to indicate the target bordering mesh networks. As an example, a bit in the message may be used to indicate whether the message should be transmitted to a bordering mesh network or not, with a value of “1” indicating that the mesh network will receive the message, and a value of “0” indicating that the mesh network will not receive the message. In the case that the mesh network has four bordering mesh networks, the target bordering network indication will takes up four bits in the message.

In an example of the present disclosure, it can be simply designed that a message is intended for all the mesh networks or only for the mesh network comprising the boundary node device. In this case, the target bordering mesh network indication may take only one bit, with for example a value of “1” showing that the boundary node device should relay the message to all bordering mesh networks, and a value of “0” indicating that the message does not need to be relayed to other mesh networks.

It can be contemplated by those skilled in the art that the target bordering mesh network indication may use reserved bit(s) in a packet header of payload of the message. In an example of the present disclosure, the target bordering mesh network indication is mapped to a corresponding network credential of a mesh networks having node devices supposed to receive said message.

This allows the boundary node device to use a correct network credential of a bordering mesh network which is indicated to receive the message by the target bordering network indication. As an example, each network credential provisioned to the boundary node device and a corresponding network ID may be mapped to a bit position of the respective target bordering network indication in the message, thereby allowing the boundary node device to obtain the network credential based on the bit position of the target bordering network indication.

It can be contemplated by those skilled in the art that the indication and mapping scheme is application dependent, and each boundary node device may adopt a dedicate design. The backend server, which has the complete plan view of the all mesh networks, is responsible for determining the indication and mapping scheme for each mesh network.

In an example of the present disclosure, the relaying step comprises retransmitting the received message using message flooding.

It therefore ensures that any node device within the communication range of the boundary node device will receive the message. The communication protocol of the mesh network can remain stay as it is, while the message will not be missed or dropped.

In an example of the present disclosure, each node device comprises a motion detection device, the message from a node device within a mesh network comprising the boundary node device is generated by the node device in response to detection of a moving object by way of the motion detection device of the node device.

In the application scenario of lighting on demand service in a large- scaled outdoor lighting system, a number of streetlights ahead of a travelling direction of a moving object should be triggered before the moving object arrives at the streetlights. This is normally realised by equipping the streetlights with a motion detection device which triggers the transmission of an alert or trigger message in the network comprising the streetlights. In the case that the network comprises a large number of streetlights arranged a long street which are provisioned into different mesh networks, the above method ensures the seamless relay of the alter or trigger message and therefore guarantees that proper light on demand service is provided.

In an example of the present disclosure, all node devices within the network are provisioned with a same application credential.

This is in consideration of the scenario where all node devices within the network run a same application. Provisioning all node devices with the same application credential enables the node devices within the network to process application data as needed.

In an example of the present disclosure, the network is a Bluetooth mesh network comprising at least two Bluetooth mesh networks or a ZigBee mesh network comprising at least two ZigBee mesh networks.

Bluetooth or ZigBee mesh network is well suited for local node to node communication. The above described method can therefore be applied to Bluetooth mesh network advantageously.

In a second aspect of the present disclosure, there is provided a node device arranged for relaying a message in a network comprising at least two mesh networks each comprising a plurality of operatively interconnected node devices, wherein the node device is comprised by a mesh network bordering at least one of the other mesh networks and is designated as a boundary node device by a network backend server, the boundary node device provisioned with a network credential specific to the mesh network comprising the boundary node device, and further provisioned with further network credential(s) specific to mesh network(s) bordering the network comprising the boundary node device, the boundary node device arranged for operating according to any of the first aspect of the present disclosure.

In a third aspect of the present disclosure, there is provided a system for relaying a message in a network, the system comprising: the network and a network backend server, the network comprising at least two mesh networks each comprising a plurality of operatively interconnected node devices, a number of node devices within each mesh network bordering at least one of the other mesh networks functions as boundary node devices, each node device within each mesh network provisioned with a network credential specific to the mesh network comprising the node device, each boundary node device further provisioned with further network credential(s) specific to mesh network(s) bordering the mesh network comprising the boundary node device, wherein: the network backend server is arranged for designating boundary node devices of each mesh network; a boundary node device is arranged for performing the method according to the first aspect of the present disclosure.

In a fourth aspect of the present disclosure there is provided a computer program product, comprising a computer readable medium storing instructions which, when executed on at least one processor, cause the at least one processor to operate a boundary node device or a network backend server in accordance with the first aspect of the present disclosure.

In a fifth aspect of the present disclosure an electric or electronic device is provided, such as a lighting device, comprising at least one node device according to the second aspect of the present disclosure.

The above mentioned and other features and advantages of the disclosure will be best understood from the following description referring to the attached drawings. In the drawings, like reference numerals denote identical parts or parts performing an identical or comparable function or operation.

Brief description of the drawings

Fig. 1 schematically illustrates a lighting system comprising a plurality of lighting devices arranged along a road or street.

Fig. 2 schematically illustrate a system for relaying a message in a network comprising at least two mesh networks each comprising a plurality of operatively interconnected node devices, in accordance with the present disclosure.

Fig. 3 illustrates, in a simplified flow chart diagram, steps of a method of relaying a message in a network of operatively interconnected node devices, such as the one shown in Figure 2, in accordance with the present disclosure.

Fig. 4 illustrates, schematically, a diagram of an example of a node device or terminal device arranged for relaying a message in a network comprising at least two networks each comprising a plurality of operatively interconnected node devices, in accordance with the present disclosure. Detailed description

Examples contemplated by the present disclosure will now be described in more detail with reference to the accompanying drawings. The disclosed subject matter should not be construed as limited to only the examples set forth herein. Rather, the illustrated examples are provided by way of example to convey the scope of the subject matter to those skilled in the art.

The present disclosure is detailed below with reference to a network of operatively interconnected lighting devices functioning as node devices of the network. Those skilled in the art will appreciate that the present disclosure is not limited to the network of lighting devices, but is applicable for networks of a wide variety of node devices enabled with network communication connectivity, as indicated in the background part.

In the following description, the terms “node device”, “lighting device”, “lighting fixture” are used interchangeably in the following description. A “network” refers to a network comprising all node devices of a system, which may comprise several “network” each comprising a part of the all node devices of the system.

Figure 1 schematically illustrates a lighting system 100 comprising a plurality of lighting devices numbered 1 to 99 arranged along a road or street 101. The lighting devices are configured into a network comprising two mesh networks 102 and 103. In Figure 1 the mesh network 102 is illustrated to comprise lighting devices 1 to 8, and the mesh network 103 is illustrated to comprise lighting devices 9 to 99. It will be understood by those skilled in the art that the mesh networks 102 and 103 of Figure 1 are for illustrative purposes only, and in practice the lighting devices may be configured into different mesh networks based on practical needs.

A service provided by the lighting system 100 is referred to as light on demand service, in which a moving object such as a car 105 driving from left to right along the road or street 101 may be detected by presence or motion sensors attached to or comprised in the lighting devices. A lighting device detecting the moving car will then be dimmed up and it may also broadcast a message to prompt the arrival of the moving car to neighbouring lighting devices, and the neighbouring lighting devices will relay the message to next ones such that a number of lighting devices ahead of the moving car, such as in total 6, can be dimmed up.

In the lighting system 100 as shown in Figure 1 , a boundary 106 between lighting devices 8 and 9 is present between the two mesh networks 102 and 103. It is known from the background that a message generated in the mesh network 102 will not be accepted and relayed in the mesh network 103, which means, the lighting device 9 and lighting devices thereafter, i.e. , lighting devices 10, 11 etc. will not be triggered by the relayed message 104 from any nodes in the mesh network 102. As a result, when the car moves close to the boundary 106 of the two mesh networks102 and 103, such as a location between the lighting devices 5 and 6, there will not be enough lights ahead its moving direction. In the example as shown in Figure 1 , the lighting device 9 will be dimmed on only when the car 105 moves to the boundary 106 between node 8 and 9. The situation will lead to bad experience for the car driver and potential safety issues.

In the following, a system for and a method of relaying a message in a network comprising at least two mesh networks each comprising a plurality of operatively interconnected node devices will be described with reference to Figures 2 and 3, in accordance with the present disclosure. Similar reference numerals are used to indicate similar components in Figures 1 and 2.

A system 20 as shown in Figure 2 comprises a network 200 comprising 2n node devices, arranged along an elongated track 201. The network 200 comprises two mesh networks 202 and 203, with the mesh network 202 comprising node devices 1 to n, and the mesh network 203 comprising the node devices n+1 to 2n.

The mesh network 202 neighbours, borders or in other word is next to the mesh network 203 physically or geographically. A boundary 206 can be considered to be present between the mesh networks 202 and 203.

The network 200 is illustrated to have a linear topology in Figure 2, as a result the mesh network 202 borders only the mesh network 203, and vice versa. It will be appreciated by those skilled in the art that a network in accordance with the present disclosure may adopt any topology appropriate for a specific application, and the mesh networks comprised by the whole network may be formed based on practical considerations. In this sense, in reality a mesh network may border a number of mesh networks with each mesh network comprising a number of node devices suitable for ensuring good performance of the network. Generally a mesh network may comprise up to hundreds of node devices.

A backend network server 21 is arranged to control, manage or operate the node devices in the network 200, by way of communication for example over Internet 22. Specifically, the backend network server 21 is, among others, responsible for the setup and creation of network configuration parameters of each local mesh network, including network credentials of each mesh network.

The backend network server 21 has a full picture of the whole network composed of several mesh networks, in the example of Figure 2 the two mesh networks 202 and 203. The backend network server 21 is therefore also arranged to determine boundary node devices for each mesh network.

In determining, designating or selecting boundary node devices for a mesh network, the backend network server 21 may take into consideration various factors such as a distance between a node device and a physical boundary of the mesh network, a number of node devices belonging to a neighbouring mesh network and within a communication range of the node device, and application-dependent requirements.

In the example as illustrated in Figure 2, for the lighting on demand service, in the case the application requires that at least six lighting devices ahead of a moving object should be dimmed up, it may be suitable to designate six lighting devices in each mesh network 202 and 203 with are close most to the boundary 206 as boundary node devices.

After creating the mesh network 202 and 203 each comprising n node devices 1 to n and n+1 to 2n, the backend network server 21 provisions 23 each node device in the mesh network 202 with a network credential NK1 specific to the mesh network 202 and further provisions 24 each node device in the mesh network 203 with a further network credential NK2, which is specific to the mesh network 203 and different from the network credential of the mesh network 202.

Moreover, in a supplementary provisioning procedure, the network backend server 21 also provisions boundary node devices in each mesh network with network credential(s) specific to mesh networks bordering the mesh network comprising the boundary node devices. In the example of Figure 2, it is illustrated that the network backend server 21 provisions 25 the node device n in the mesh network 202 with the network credential NK2 of the mesh network 203, and also provisions 26 the node device n+1 in the mesh network 203 with the network credential NK1 of the mesh network 202.

Generally, a boundary node device in a mesh network is provisioned m+1 network credentials, where m is equal to a number of mesh networks bordering the mesh network comprising the boundary node device.

Besides, the network backend server 21 may provision all node devices involved in a same application with a corresponding application credential. In the example of Figure 2, all node devices are provisioned with a same lighting on demand application key AK.

Figure 3 illustrates, in a simplified flow chart diagram, steps of a method 30 of relaying a message in a network of operatively interconnected node devices, such as the one shown in Figure 2, in accordance with the present disclosure.

The method 30 comprises preparatory steps 31 and 32 respectively for designating boundary node devices for each mesh network, and provisioning the boundary node devices with suitable network credentials. Detailed implementation of steps 31 and 32 are described above with reference to Figure 2.

At step 33, a boundary node device receives a message transmitted from a node device within a mesh network comprising the boundary node device. In the example of Figure 2, the message may be transmitted by the lighting device n-2 in response to detection of a car 205, and optionally relayed 204 via the lighting device n-1 , to the boundary lighting device n.

At step 34, the boundary node device determines that the message is intended to at least one of the other mesh networks having node devices supposed to receive the message and bordering the mesh network comprising the boundary node device. The message therefore has to be transmitted across the boundaries between the different mesh networks.

Various coding methods can be used to define how to indicate the target bordering mesh networks, that is, mesh networks supposed to receive the message. In an exemplary example, a target bordering mesh network indication comprised in the message is used to indicate which mesh networks are or comprise node devices supposed to receive the message. As a specific example, a bit in the message may be used to indicate whether the message should be transmitted to a bordering mesh network or not, with a value of “1” indicating that the bordering mesh network will receive the message, and a value of “0” indicating that the bordering network will not receive the message. In the case that the mesh network has four bordering mesh networks, the target bordering mesh network indication will takes up four bits in the message.

In a simplified but efficient design, it is either designated that node devices of all mesh networks in the network will receive the message, or only node devices in the mesh network comprising the boundary node device will receive the message. In this case, the target bordering mesh network indication may take only one bit, with for example a value of “1” showing that the boundary node device should relay the message to all bordering mesh networks, and a value of “0” indicating that the message does not need to be relayed to other mesh networks.

It can be contemplated by those skilled in the art that the target bordering mesh network indication may use reserved bit(s) in a packet header of payload of the message.

When the boundary node device at step 34 makes a positive decision, the method proceeds to step 35, where the boundary node device relays the received message a number of times, the number being determined by a number of networks determined to receive the message at step 34.

Each time the message is relayed by the boundary node device, it is protected with a different network credential, such as a network credential of the mesh network comprising the boundary node device, or a network credential of a mesh network bordering the mesh network comprising the boundary node device. As a result, a node device in a mesh network bordering the mesh network comprising the boundary node device, when receiving the relayed message, will be able to decrypt and authenticate the message using the correct network credential, and process the message thereafter.

For the boundary node device to relay the message to a particular bordering mesh network using a network credential of the particular mesh network, the target bordering network indication, for indicating that the particular mesh network is supposed to receive the message, is mapped to the corresponding network credential of the particular bordering mesh network. This allows the boundary node device to use a correct network credential of a bordering mesh network which is indicated to receive the message by the target bordering mesh network indication. As an example, each network credential provisioned to the boundary node device and a corresponding network ID may be mapped to a bit position of the respective target bordering mesh network indication in the message, thereby allowing the boundary node device to obtain the network credential based on the bit position of the target bordering mesh network indication.

It can be contemplated by those skilled in the art that the indication and mapping scheme is application dependent, and each boundary node device may adopt a dedicate design. The backend server, which has the complete plan view of the all networks, is responsible for determining the indication and mapping scheme for each mesh network.

In the specific example as illustrated in Figure 2, the message 207, which is encrypted with the network credential NK2 of the mesh network 203, relayed from the node device n in the mesh network 202 to the node device n+1 in the mesh network 203, will be decrypted and authenticated by the node device n+1. The node device n+1 , being a lighting device, will then be dimmed up based on operation command further included in the message. The node device n+1 may also triggers the node devices n+2 and n+3 ahead of it in the travelling direction of the car 205. It therefore ensures that there are still totally six lighting devices dimmed up ahead of the car, thereby providing an improved user experience while preventing any possible safety issues that may be caused by insufficient lighting along the street 201.

Figure 4 illustrates, schematically, a diagram of an example of a node device or terminal device 40 arranged for relaying a message in a network comprising at least two mesh mesh networks each comprising a plurality of operatively interconnected node devices, in accordance with the present disclosure.

The node device 40 comprises a control part or control device 110 and a load such as a lighting fixture or lighting device 120, comprising a lighting module 121, preferably a Light Emitting Diode, LED, lighting module or a plurality of LED lighting modules, operation of which may be controlled by the control device 110 from or through a remote control device, such as a remote or backend server (not shown), for example. The control device 110 operates a long range communication interface 141 , such as a first network adaptor or a transceiver, Tx/Rx 1 , module, arranged for direct wireless message exchange or data packets 142 with a remote control device or backend server. The long range communication interface 141 typically operates according to a mobile communication system technology in a licensed frequency band, such as 2G/3G/4G/5G cellular communication, and other long-range wireless communication technologies, such as known as Long Range Wide Area Network, LoRaWAN, and Narrowband loT, NB-loT, communication, for example. However, the long range communication interface 141 may also operate according to a proprietary wireless communication protocol or technology.

The long range communication interface 141 may also be arranged for wired message exchange 143, such as for data exchange over an Ethernet connection and the Internet, or the like.

The control device 110 further operates a short range communication interface 151 , such as a second network adapter or transceiver, Tx/Rx 2, module arranged for short-range wireless 152 or wired 153 exchange of messages or data packets with another node device in the network, i.e. so called inter-node device communication. Network protocols for exchanging data by networked devices or nodes may comprise ZigBee™, Bluetooth™, as well as WiFi based protocols for wireless networks, and wired bus networks such as DALI™ (Digital Addressable Lighting Interface), DSI (Digital Serial Interface), DMX (Digital Multiplex), and KNX (or KNX based systems), and other proprietary protocols.

The control device 110 further comprises at least one microprocessor, mR, or controller 145, and at least one data repository or storage or memory 146, among others for storing address information of the node device itself and other node devices, such as identifiers 147, IDs, Media Access Control, MAC, addresses and subscriber information of node devices. The repository 146 also stores a network credential for a network comprising the node device 40 and further network credentials for other mesh networks bordering the mesh network comprising the node device 40 . Instead of the repository 146, a separate memory or storage accessible to the at least one processor or controller 145 may be provided.

The at least one microprocessor or controller 145 communicatively interacts with and controls the long range communication interface 141 , the short range communication interface 151 , and the at least one repository or storage 146 via an internal data communication and control bus 148 of the control device 110.

When the node device 40 functions as a boundary node device in a mesh network of a large-scale network, the at least one microprocessor or controller 145 may operate to perform the method of relaying a message in the network described above.

The lighting fixture or lighting device 120 connects 144 to and is controlled from the data communication and control bus 148 by the at least one microprocessor or controller 110. Those skilled in the art will appreciate that any electric load may be connected 144 to the control bus other than or in addition to a lighting fixture or lighting device 120, such as an access point device or a geographic routing device.

The present disclosure is not limited to the examples as disclosed above, and can be modified and enhanced by those skilled in the art beyond the scope of the present disclosure as disclosed in the appended claims without having to apply inventive skills and for use in any data communication, data exchange and data processing environment, system or network.

Claims

1. A method (30) of relaying a message in a network (200) comprising at least two different mesh networks (202, 203), each mesh network (202, 203) comprising a plurality of operatively interconnected node devices, a number of node devices within each mesh network (202, 203) bordering at least one of the other mesh networks (203, 202) being designated as boundary node devices by a network backend server (21), each node device within each mesh network (202, 203) provisioned (32) with a network credential specific to said mesh network comprising said node device, each boundary node device further provisioned (32) with further network credential(s) specific to mesh network(s) bordering said mesh network comprising said boundary node device, the method comprising the steps of: receiving (33), by a boundary node device, a message from a node device within a mesh network comprising said boundary node device; determining (34), by said boundary node device, that said message is intended to at least one of the other mesh networks having node devices supposed to receive said message and bordering said mesh network comprising said boundary node device, and relaying (35), by said boundary node device, said message a number of times, said number being equal to a number of mesh networks having node devices supposed to receive said message, said message relayed each time being encrypted with a respective network credential of a mesh network having node devices supposed to receive said message.

2. The method (30) according to claim 1 , wherein a node device is designated (31) as a boundary node device of a mesh network on the basis of at least one of a physical distance between said node device and a physical boundary of said mesh network, a number of node devices belonging to a bordering mesh network and within a communication range of said node device, and an application-dependent requirement.

3. The method (30) according to claim 2, wherein a physical distance between said node device and said physical boundary of said mesh network is determined on the basis of a plan view or layout of said network comprising at least two different mesh networks.

4. The method (30) according to claim 2, wherein said application- dependent requirement comprises a number of node devices to be designated as boundary node devices.

5. The method (30) according to any of the previous claims, wherein said determining (34), by said boundary node device, that said message is intended to at least one of the other mesh networks having node devices supposed to receive said message and bordering said mesh network comprising said boundary node device is made with reference to a target bordering mesh network indication comprised in said message.

6. The method (30) according to claim 5, wherein said target bordering mesh network indication is mapped to a corresponding network credential of a mesh networks having node devices supposed to receive said message.

7. The method (30) according to any of the pervious claims, wherein said relaying step (35) comprises retransmitting said received message using message flooding.

8. The method (30) according to any of the previous claims, wherein each node device comprises a motion detection device, said message from a node device within a mesh network comprising said boundary node device is generated by said node device in response to detection of a moving object by way of said motion detection device of said node device.

9. The method (30) according to any of the previous claims, wherein all node devices within said mesh network (200) are provisioned with a same application credential.

10. The method (30) according to any of the previous claims, wherein said network is a Bluetooth mesh network comprising at least two Bluetooth mesh networks or a ZigBee mesh network comprising at least two ZigBee mesh networks.

11. A node device arranged for relaying a message in a network comprising at least two mesh networks each comprising a plurality of operatively interconnected node devices, wherein the node device is comprised by a mesh network bordering at least one of the other mesh networks and is designated as a boundary node device by a network backend server, said boundary node device provisioned with a network credential specific to said mesh network comprising said boundary node device, and further provisioned with further network credential(s) specific to mesh network(s) bordering said mesh network comprising said boundary node device, the boundary node device arranged for operating according to any of the previous claims 1 to 10.

12 A system (20) comprising: a network (200) and a network backend server (21), said network (200) comprising at least two mesh networks (202, 203) each comprising a plurality of operatively interconnected node devices, a number of node devices within each mesh network bordering at least one of the other mesh networks functions as boundary node devices, each node device within each mesh network provisioned with a network credential specific to said mesh network comprising said node device, each boundary node device further provisioned with further network credential(s) specific to mesh network(s) bordering said mesh network comprising said boundary node device, wherein: said network backend server (21) is arranged for designating boundary node devices of each mesh network; a boundary node device (n, n+1) is arranged for performing the method according to any of claims 1 to 10.

13. The system according to claim 12, wherein: said network backend server (21) is arranged for provisioning each node device with said network credential specific to said mesh network comprising said node device; said network backend server (21) is further arranged for provisioning each boundary node device with said network credential(s) specific to mesh network(s) bordering said mesh network comprising said boundary node device.

14. A computer program product, comprising a computer readable medium storing instructions which, when executed on at least one processor, cause said at least one processor to operate one of a backend server and a boundary node device in accordance with the method of any of claims 1 - 10.

15. An electric or electronic device, such as a lighting device, comprising at least one node device according to claim 11.