WO2014069981A1

WO2014069981A1 - A method for re-connecting an isolated node in a wireless mesh network

Info

Publication number: WO2014069981A1
Application number: PCT/MY2013/000173
Authority: WO
Inventors: Khoshdelniat Reza; Rao A/L Sinniah GOPINATH; Suryady Bin Kamalurradat ZELDI; Sarwar Usman
Original assignee: Mimos Berhad
Priority date: 2012-11-02
Filing date: 2013-09-30
Publication date: 2014-05-08
Also published as: MY155920A

Abstract

The present invention relates to a method for re-connecting an isolated node in a wireless mesh network. When a node is isolated from its network, the method allows the node to re-connect to its network by routing the isolated node through a neighbouring wireless mesh network. Each network comprises of a gateway (50) and a plurality of wireless nodes. The gateway (50) includes a memory (51), and a processor (52) having a collaboration module (53) and a trust module (54). The collaboration module (53) is used to allow collaboration between the wireless mesh network and the neighbouring network. The trust module (54) is used to determine whether the isolated node belongs to the wireless mesh network. Each wireless node (10) includes a memory (11), and a processor (12) having a collaboration module (13) to allow communication between the node (10) and a wireless node (10) of the neighbouring network.

Description

A METHOD FOR RE-CONNECTING AN ISOLATED NODE IN A WIRELESS MESH

NETWORK

FIELD OF INVENTION

The present invention generally relates to a wireless mesh network, and more particularly to a system and method for re-connecting an isolated node in a wireless mesh network.

BACKGROUND OF THE INVENTION

In a wireless mesh network, a plurality of nodes are interconnected to allow communication between two nodes or between a node and a gateway that could be multi-hops apart. A suitable routing protocol is typically predefined in the wireless mesh network to ensure that a traffic from a source node can be properly routed to a destination node or a gateway that are multi-hops apart.

As the connectivity of the nodes are predefined prior to the actual communication between those nodes, the predefined route may be susceptible to a node or link failure, interference, unsynchronized sleeping schedule of a node and etc. Thus, the destination node or gateway may not be able to receive the traffic sent by the source node due to one or more intermediate nodes in the route are inoperable. In regard to this, a dynamic routing protocol is deployed in the wireless mesh network. The dynamic routing protocol determines a best path to route the traffic between the source node and the destination node. If one or more intermediate nodes are inoperable in the determined path, the dynamic routing protocol determines an alternate path for routing the traffic between those two nodes.

However, the problem arises if a node at the border of the network is disconnected from the network due to its neighbouring nodes are inoperable. The node is isolated from the network, and thus, no traffic can be sent to the isolated node. Therefore, there is a need to re-connect the isolated node to its wireless mesh network. SUMMARY OF INVENTION

In a first aspect of the present invention, a method for re-connecting an isolated node in a wireless mesh network is provided. The method is characterised by the steps of: (a) detecting disconnection with any node within the wireless mesh network by the isolated node; (b) broadcasting a collaboration request message by the isolated node; (c) receiving the collaboration request message by a collaborating node from a neighbouring network; (d) storing the details of the isolated node and adding its network identifier in the collaboration request message by the collaborating node; (e) re-broadcasting the collaboration request message; (f) receiving the collaboration request message by a node from the wireless mesh network, wherein repeating steps (d) and (e) if the collaboration request message is received by another collaborating node and if no collaboration cancellation message has been received by the collaborating node; (g) storing the address of the collaborating node and the network identifier of the neighbouring network; (h) sending the collaboration request message and a collaboration relay message from the node to a gateway of the wireless mesh network, and sending a collaboration response message from the node to the collaborating node; (i) determining whether the node sending the collaboration response message is from the wireless mesh network by the collaborating node, and determining whether the isolated node belongs to the wireless mesh network by the gateway; (j) sending an approval message from the gateway of the wireless mesh network to a gateway of the neighbouring network if the isolated node belongs to the wireless mesh network; (k) receiving the approval message by the gateway of the neighbouring network; (I) storing the address of the isolated node by the gateway of the neighbouring network; and (m) sending a collaboration permission message from the gateway of the neighbouring network to all nodes in the neighbouring network.

Preferably, the collaborating node discards the collaboration request message if a number of hops has exceeded or equal to a predetermined threshold.

Preferably, the gateway determines whether the isolated node belongs to the wireless mesh network by comparing the address of the isolated node in the collaboration relay message with a list of addresses of all nodes associated with the wireless mesh network. Preferably, determining whether the node sending the collaboration response message is from the wireless mesh network includes the steps of comparing the network identifier in the collaboration response message with the network identifier in the collaboration request message; and storing the address of the node sending the collaboration response message and broadcasting a collaboration cancellation message by the collaborating node if both network identifiers are similar.

In a second aspect of the present invention, a method for re-connecting an isolated node in a wireless mesh network is provided. The method characterised by the steps of: (a) detecting disconnection with any node within the wireless mesh network by the isolated node; (b) broadcasting a collaboration request message by the isolated node; (c) receiving the collaboration request message by a collaborating node from a neighbouring network; (d) storing the details of the isolated node and adding its network identifier in the collaboration request message by the collaborating node; (e) re-broadcasting the collaboration request message by the collaborating node; (f) receiving the collaboration request message by a gateway of the neighbouring network, wherein repeating steps (d) and (e) if the collaboration request message is received by another collaborating node and if no collaboration cancellation message has been received by the collaborating node; (g) storing the network identifier and the address of the isolated node in the gateway of the neighbouring network; (h) sending an acknowledgement message to the collaborating node sending the collaboration request message; (i) broadcasting a collaboration cancellation message by the collaborating node; (j) sending an approval request message from the gateway of the neighbouring network to the gateway of the wireless mesh network; (k) storing the address of the isolated node and the network identifier of the neighbouring network by the gateway of the wireless mesh network; (I) determining whether the isolated node belongs to the wireless mesh network by the gateway of the wireless mesh network; (m) sending an approval message from the gateway of the wireless mesh network to a gateway of the neighbouring network if the isolated node belongs to the wireless mesh network; (n) storing the address of the isolated node by the gateway of the neighbouring network; and (o) sending a collaboration permission message from the gateway of the neighbouring network to all nodes in the neighbouring network. Preferably, the collaborating node discards the collaboration request message if a number of hops has exceeded or equal to a predetermined threshold.

Preferably, the gateway determines whether the isolated node belongs to the wireless mesh network by comparing the address of the isolated node in the collaboration relay message with a list of addresses of all nodes associated with the wireless mesh network.

In a third aspect of the present invention, a gateway (50) of a wireless mesh network is provided. The gateway (50) comprises of a processor (52) and a memory (51). Moreover, the gateway (50) is characterised in that the processor (52) includes a collaboration module (53) to allow collaboration between the wireless mesh network with a neighbouring wireless mesh network for re-connecting an isolated node to the wireless mesh network; and a trust module (54) to determine whether the isolated node belongs to the wireless mesh network.

Preferably, the memory (51 ) is used for storing a list of addresses of all nodes associated with the wireless mesh network, a network identifier and address Of at least one gateway of at least one neighbouring network, and an address of the isolated node.

In a fourth aspect of the present invention, a wireless node (10) of a wireless mesh network is provided. The wireless node (10) comprises of a processor (12) and a memory (11). Moreover, the wireless node (10) is characterised in that the processor (12) includes a collaboration module (13) to allow communication between the wireless node and a wireless node of a neighbouring wireless mesh network.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 shows a flowchart of a method for re-connecting an isolated node in a wireless mesh network according to a first embodiment of the present invention. FIG. 2 shows a flowchart of a method for re-connecting an isolated node in a wireless mesh network according to a second embodiment of the present invention.

FIG. 3 shows a block diagram of a first example of an arrangement of two wireless mesh networks.

FIG. 4 shows a block diagram of a second example of an arrangement of two wireless mesh networks. FIG. 5 shows a block diagram of a gateway (50) according to an embodiment of the present invention.

FIG. 6 shows a block diagram of a wireless node (10) according to an embodiment of the present invention.

DESCRIPTION OF THE PREFFERED EMBODIMENT

A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description/ well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.

Referring to FIG. 1, there is shown a method for re-connecting an isolated node in a wireless mesh network according to a first embodiment of the present invention. When a node is isolated from its network, the method allows the node to re-connect to its network by routing the isolated node through a neighbouring network. In order for the isolated node to communicate with the neighbouring network, the neighbouring network must have the same physical layer and medium access control (MAC) layer standard as the physical and MAC layers standard used by the wireless mesh network.

Initially, as in step 101, a node detects that it is unable to connect with any node within its wireless network. This is due to the node is not receiving any acknowledgment message when it sends its periodical data messages to a destination node in its wireless network. Thus, the node is isolated from its network. In step 102, the isolated node broadcasts a collaboration request message The data fields of the collaboration request message are located in the MAC layer header and it includes an address of the isolated node (ReqjNodeJD field), an address of a destination node or a gateway in the same network as the isolated node (DstJD field), a Personal Area Network Identifier or PAN ID of the isolated node (PANJD field), and a PAN ID of the neighbouring network (Collab_PAN_ID field).

The collaboration request message is received by a collaborating node from a neighbouring network and thereon, the collaborating node stores the details of the isolated node and adds its PAN ID to the Collab_PAN_ID field in the collaboration request message as in step 103.

The collaboration request message has a limited number of hops to limit the number of times that the collaboration request message can be rebroadcasted. This is to prevent the neighbouring network from being flooded with collaboration request message and thus, affecting the bandwidth capacity of the neighbouring network. In step 104 and decision 105, the collaborating node checks a number of hops of the collaboration request message and determines whether the number of hops has exceeded a predetermined threshold. If the number of hops has exceeded or equal to the predetermined threshold, the collaborating node discards the collaboration request message as in decision 105 and step 106.

However, if the number of hops has not exceeded the threshold, the collaborating node rebroadcasts the collaboration request message as in decision 105 and step 107.

If the collaboration request message is received by another collaborating node in the neighbouring network, the collaborating node determines whether it receives a collaboration cancellation message before rebroadcasting the collaboration request message (decision 108 and step 110). The collaboration cancellation message is to inform all other nodes in the neighbouring network to stop rebroadcasting the collaboration request message. If the collaborating node receives the collaboration cancellation message, the collaborating node does not rebroadcast the collaboration request message (decision 111 and step 112). Otherwise, the collaborating node stores the details of the isolated node and repeats step 104 to rebroadcast the collaboration request message.

If the collaboration request message is received by a node from the same network as the isolated node, the node stores the address of the collaborating node and also the PAN ID of the neighbouring network as provided in the Collab_PAN_ID field of the collaboration request message (decision 108 and step 120). Moreover, the node from the same network as the isolated node forwards the collaboration request message and a collaboration relay message to the gateway in the same network (step 121). The collaboration relay message is to indicate to the gateway that a node has been isolated from the network and thus, the gateway can communicate with the gateway of the neighbouring network for further action regarding the isolated node. The collaboration relay message includes an address of the isolated node (Req_Node_ID field), an address of a destination node or gateway in the same network as the isolated node (DstJD field), PAN ID of the neighbouring network (Collab_PAN_ID field), PAN ID of the isolated node (PANJD field). In addition to that, the node also sends a collaboration response message to the collaborating node. The collaboration response message is to inform the collaborating node that the collaboration request message has been received by a node from the same network as the isolated node and thus, a link has been established to re-connect the isolated node to its network through the first collaborating node of the neighbouring network. The collaboration response message includes the PAN ID of the node sending the collaboration response message. Thereon, the collaborating node determines whether the node sending the collaboration response message is from the same network as the isolated node (step 122). In addition to that, the gateway receiving the collaboration relay message determines whether the isolated node belongs to its network. The collaborating node determines whether the node sending the collaboration response message is from the same network as the isolated node by comparing the PAN ID in the collaboration response message with the PAN ID in the PANJD field of the collaboration request message. If the PAN ID in the collaboration response message differs from the PAN ID in the collaboration request message, the collaborating node discards the collaboration response message (decision 123 and step 124). However, if both PAN IDs are similar, the collaborating node stores the address of the node sending the collaboration response message and broadcasts a collaboration cancellation message (decision 123 and step 125). On the other hand, the gateway determines whether the isolated node belongs to its network by comparing the address of the isolated node in the Req_Node_ID field in the collaboration relay message with the list of addresses of all nodes associated with its network. If there is a similar address in the list of the gateway as the address of the isolated node, the gateway sends an approval message to a gateway of the neighbouring network (decision 123 and step 125). The approval message includes an address of the isolated node (Req_Node_ID field), a PAN ID of the neighbouring network (Collab_PAN_ID field), a PAN ID of the isolated node (PANJD field). The approval message indicates that the isolated node is verified by the gateway of its network and it is secure for the neighbouring network to collaborate with the isolated node to establish the reconnection between the isolated node and its network. However, if there is no similar address in the list of the gateway as the address of the isolated node, this indicates that the isolated node does not belong to the same network as the gateway and the gateway discards the collaboration request message (decision 123 and step 124).

Once the gateway of the neighbouring network receives the approval message, the gateway of the neighbouring network stores the address of the isolated node and thereon, it sends a collaboration permission message to all nodes in the neighbouring network (step 126). Thereon, the nodes are able to accept the data messages sent by the isolated node and forward it to the node in the same network as the isolated node. Thus, the isolated node is re-connected to its network through the neighbouring network.

Referring to FIG. 2, there is shown a method for re-connecting an isolated node in a wireless mesh network according to a second embodiment of the present invention. When a node is isolated from its network, the method allows the node to re-connect to its network by routing the isolated node through a neighbouring network. In order for the isolated node to communicate with the neighbouring network, the neighbouring network must have the same physical layer and medium access control (MAC) layer standard as the physical and MAC layers standard used by the wireless mesh network.

Initially, as in step 201 , a node detects that it is unable to connect with any node within its wireless network. This is due to the node is not receiving any acknowledgment message when it sends its periodical data messages to a destination node in its wireless network. Thus, the node is isolated from its network.

In step 202, the isolated node broadcasts a collaboration request message. The data fields of the collaboration request message are located in the MAC layer header and it includes an address of the isolated node (Req_Node_ID field), an address of a destination node or a gateway in the same network as the isolated node (DstJD field), a Personal Area Network Identifier or PAN ID of the isolated node (PANJD field), and a PAN ID of the neighbouring network (Collab_PAN_ID field).

The collaboration request message is received by a collaborating node from a neighbouring network and thereon, the collaborating node stores the details of the isolated node and adds its PAN ID to the Collab_PAN_ID field in the collaboration request message as in step 203.

The collaboration request message has a limited number of hops to limit the number of times that the collaboration request message can be rebroadcasted. This is to prevent the neighbouring network from being flooded with collaboration request message and thus, affecting the bandwidth capacity of the neighbouring network. In step 204 and decision 205, the collaborating node checks the number of hops of the collaboration request message and determines whether the number of hops has exceeded a predetermined threshold. If the number of hops has exceeded or equal to the predetermined threshold, the collaborating node discards the collaboration request message as in decision 205 and step 206.

However, if the number of hops has not exceeded the threshold, the collaborating node rebroadcasts the collaboration request message as in decision 205 and step 207. If the collaboration request message is received by another collaborating node in the neighbouring network, the collaborating node determines whether it receives a collaboration cancellation message before rebroadcasting the collaboration request message (decision 208 and step 210). The collaboration cancellation message is to inform all other nodes in the neighbouring network to stop rebroadcasting the collaboration request message. If the collaborating node receives the collaboration cancellation message, the collaborating node does not rebroadcast the collaboration request message (decision 211 and step 212). Otherwise, the collaborating node stores the details of the isolated node and repeats step 204 to rebroadcast the collaboration request message.

If the collaboration request message is received by the gateway in the neighbouring network, the gateway stores the PAN ID of the isolated node and the address of the isolated node and thereon, the gateway sends an acknowledgement message to the collaborating node sending the collaboration request message (decision 208 and step 220).

Once the collaborating node receives the acknowledgement message from the gateway, the collaborating node broadcasts a collaboration cancellation message (step 221).

Thereon, the gateway in the neighbouring network sends an approval request message to the gateway in the same network as the isolated node (step 222). The approval request message includes an address of the isolated node (Req_Node_ID field), and a PAN ID of the neighbouring network (PANJD field).

Once the gateway in the same network as the isolated node has received the approval request message, the gateway records the address of the isolated node and the PAN ID of the neighbouring network (step 223). Thereon, the gateway determines whether the isolated node belongs to its network by comparing the address of the isolated node in the Req_Node_ID field in the collaboration relay message with the list of addresses of all nodes associated with its network. If there is a similar address in the list of the gateway as the address of the isolated node, the gateway sends the approval message to a gateway of the neighbouring network (decision 224 and step 226). However, if there is no similar address in the list of the gateway as the address of the isolated node, this indicates that the isolated node does not belong to the same network as the gateway and the gateway discards the collaboration request message (decision 224 and step 225). Once the gateway of the neighbouring network receives the approval message, the gateway of the neighbouring network stores the address of the isolated node and thereon, it sends a collaboration permission message to all nodes in the neighbouring network (step 227). Thereon, the nodes are able to accept the data messages sent by the isolated node and forward the data messages to the gateway in the neighbouring network node. Thus, a link between the network and the neighbouring network has been established through both gateways. The isolated node can now be re-connected to its network.

Referring to FIG. 3, there is shown a first example of an arrangement of two wireless mesh networks. The first and second networks are different in terms of its high level communication protocol. However, both networks have the same physical layer and MAC layer standard. For instance, the first network is a ZigBee network based on IEEE 802.15.4 physical and MAC layers whereas the second network is a 6L0WPAN network based on IEEE 802.15.4 physical and MAC layers.

A first network comprises of a plurality of wireless nodes (10) and a first gateway (50a) which is connected to three nodes (10a, 10b, 10c), whereas a second network comprises of a plurality of wireless nodes (10') and a second gateway (50b) is connected to two nodes (10b', 10c') of the second network. Certain nodes (10g, 10h, 10i, 10j, 10k) of the first network overlap with the coverage of certain nodes (10c', 10d', 10g', 10h', 10k', 101') of the second network. Although the nodes are overlapping, the nodes (10g, 10h, 10i, 10j, 10k) of the first network are not connected to the nodes (10c', 10d', 10g', 10h', 10k', 101') of the second network. When a node (10k) of the first network is isolated or disconnected from its neighbouring node (10i), the isolated node (10k) is re-connected to its network through some of the nodes (10') in the second network by using the method as shown in FIG. 1. Moreover, one of the nodes (10) is connected to a node (10') in the second network to allow re-connection of the isolated node (10k). Referring to FIG. 4, there is shown a second example of an arrangement of two wireless mesh networks. The first and second networks are different in terms of its high level communication protocol. However, both networks have the same physical layer and MAC layer standard. For instance, the first network is a ZigBee network based on IEEE 802.15.4 physical and MAC layers whereas the second network is a 6L0WPAN network based on IEEE 802.15.4 physical and MAC layers.

A first network comprises of a plurality of wireless nodes (10") and a first gateway (50c) which is connected to three nodes (10a", 10b", 10c"), whereas a second network comprises of a plurality of wireless nodes (10"') and a second gateway (50d) is connected to two nodes (10b'", 10c'") of the second network. A node (10k") of the first network overlaps with the coverage of certain nodes (10j"', 10k'") of the second network. Although the nodes are overlapping, the node (10k") of the first network is not connected to the nodes (lOj'", 10k'") of the second network.

When a node (10k") of the first network is isolated or disconnected from its neighbouring node (10d"), the isolated node (10k") is re-connected to its network through the second network by using the method as shown in FIG. 2. More particularly, a link is established between the second gateway (50d) and the isolated node (10k") through the nodes (10"') in the second network. The second gateway (50d) establishes a link to the first gateway (50c) to allow re-connection of the isolated node (10k"). FIG. 5 shows a block diagram of the gateways (50) of FIGS. 3 and 4. Each gateway (50) includes a memory (51 ) and a processor (52). The gateway (50) may also include any other software and/or hardware to access another network.

A list of addresses of all nodes associated with the wireless mesh network of the gateway (50) is stored in the memory (51). Moreover, the memory (51) also stores network identifier or PAN ID and address of at least one gateway of at least one neighbouring network and the address of the isolated node.

The processor (52) further includes a collaboration module (53) and a trust module (54). The collaboration module (53) is used to allow collaboration between the wireless mesh network of the gateway (50) with a neighbouring wireless mesh network, wherein the collaboration module (53) receives and processes a collaboration request message, replies with an approval message based on the collaboration request message, and transmits a collaboration permission message. Thus, this is to re-connect an isolated node to its wireless mesh network. The trust module (54) is used to determine whether the isolated node belongs to the network of the gateway (50).

FIG. 6 shows a block diagram of the wireless nodes (10) of FIGS. 3 and 4. Each node (10) includes a memor (11) and a processor (12). In addition to that, each node (10) may also include any other suitable hardware and/or software to transmit, receive and/or process communications in a wireless mesh network.

The memory (11) stores information of an isolated node and a node sending a collaboration response message. Such information includes but not limited to an address of the node and a network identifier or PAN ID of the node.

The processor (12) further includes a collaboration module (13). The collaboration module (13) is used to allow collaboration and communication between the wireless node and a wireless node of a neighbouring wireless mesh network, wherein the collaboration module (13) broadcasts a collaboration request message, replies with a collaboration response message based on the collaboration request message, sends a collaboration relay message to the gateway in its network, and transmits collaboration cancellation message. Thus, this is to re-connect an isolated node to its wireless mesh network. In addition to that, the collaboration module (13) is also used for transmitting and receiving packets to/from at least one neighbouring node and/or at least one gateway.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrated and describe all possible forms of the invention. Rather, the words used in the specifications are words of description rather than limitation and various changes may be made without departing from the scope of the invention.

Claims

Ϊ . A method for re-connecting an isolated node in a wireless mesh network is characterised by the steps of:

a) detecting disconnection with any node within the wireless mesh network by the isolated node;

b) broadcasting a collaboration request message by the isolated node; c) receiving the collaboration request message by a collaborating node from a neighbouring network;

d) storing the details of the isolated node and adding its network identifier in the collaboration request message by the collaborating node;

e) re-broadcasting the collaboration request message;

f) receiving the collaboration request message by a node from the wireless mesh network, wherein repeating steps (d) and (e) if the collaboration request message is received by another collaborating node and if no collaboration cancellation message has been received by the collaborating node;

g) storing the address of the collaborating node and the network identifier of the neighbouring network;

h) sending the collaboration request message and a collaboration relay message from the node to a gateway of the wireless mesh network, and sending a collaboration response message from the node to the collaborating node;

i) determining whether the node sending the collaboration response message is from the wireless mesh network by the collaborating node, and determining whether the isolated node belongs to the wireless mesh network by the gateway;

j) sending an approval message from the gateway of the wireless mesh network to a gateway of the neighbouring network if the isolated node belongs to the wireless mesh network;

k) receiving the approval message by the gateway of the neighbouring network;

I) storing the address of the isolated node by the gateway of the neighbouring network; and

m) sending a collaboration permission message from the gateway of the neighbouring network to all nodes in the neighbouring network.

2. The method as claimed in claim 1, wherein the collaborating node discards the collaboration request message if a number of hops has exceeded or equal to a predetermined threshold.

3. The method as claimed in claim 1 , wherein the gateway determines whether the isolated node belongs to the wireless mesh network by comparing the address of the isolated node in the collaboration relay message with a list of addresses of all nodes associated with the wireless mesh network.

4. The method as claimed in claim 1, wherein determining whether the node sending the collaboration response message is from the wireless mesh network includes the steps of:

a) comparing the network identifier in the collaboration response message with the network identifier in the collaboration request message; and

b) storing the address of the node sending the collaboration response message and broadcasting a collaboration cancellation message by the collaborating node if both network identifiers are similar.

5. A method for re-connecting an isolated node in a wireless mesh network is characterised by the steps of:

e) re-broadcasting the collaboration request message by the collaborating node;

f) receiving the collaboration request message by a gateway of the neighbouring network, wherein repeating steps (d) and (e) if the collaboration request message is received by another collaborating node and if no collaboration cancellation message has been received by the collaborating node;

g) storing the network identifier and the address of the isolated node in the gateway of the neighbouring network;

h) sending an acknowledgement message to the collaborating node sending the collaboration request message;

i) broadcasting a collaboration cancellation message by the collaborating node;

j) sending an approval request message from the gateway of the neighbouring network to the gateway of the wireless mesh network; k) storing the address of the isolated node and the network identifier of the neighbouring network by the gateway of the wireless mesh network;

I) determining whether the isolated node belongs to the wireless mesh network by the gateway of the wireless mesh network;

m) sending an approval message from the gateway of the wireless mesh network to a gateway of the neighbouring network if the isolated node belongs to the wireless mesh network;

n) storing the address of the isolated node by the gateway of the neighbouring network; and

o) sending a collaboration permission message from the gateway of the neighbouring network to all nodes in the neighbouring network.

The method as claimed in claim 5, wherein the collaborating node discards the collaboration request message if a number of hops has exceeded or equal to a predetermined threshold.

The method as claimed in claim 5, wherein the gateway determines whether the isolated node belongs to the wireless mesh network by comparing the address of the isolated node in the collaboration relay message with a list of addresses of all nodes associated with the wireless mesh network.

A gateway (50) of a wireless mesh network comprising a processor (52) and a memory (51), wherein said gateway (50) is characterised in that said processor (52) includes: a) a collaboration module (53) to allow collaboration between the wireless mesh network with a neighbouring wireless mesh network for re-connecting an isolated node to the wireless mesh network; and b) a trust module (54) to determine whether the isolated node belongs to the wireless mesh network.

9. The gateway (50) as claimed in claim 8, wherein said memory (51) is used for storing a list of addresses of all nodes associated with the wireless mesh network, a network identifier and address of at least one gateway of at least one neighbouring network, and an address of the isolated node.

10. A wireless node (10) of a wireless mesh network comprising a processor (12) and a memory (11), wherein said wireless node (10) is characterised in that said processor (12) includes a collaboration module (13) to allow collaboration and communication between the wireless node and a wireless node of a neighbouring wireless mesh network.