JP4517885B2 - Network reconfiguration method, program, information recording medium, node, base station, multi-hop network system - Google Patents

Description

  The present invention relates to a network reconfiguration method for partially reconfiguring a tree network when a node is deleted, failed, or added in a wireless sensor network.

  A wireless sensor network senses environmental information such as temperature and humidity with distributed sensor nodes (hereinafter referred to as nodes), collects the results at a base station by a network composed of nodes, and performs statistical analysis and notification of abnormality detection It is a network system used for

  A wireless sensor network is premised on a tree network, and a tree network having a base station as a root when a node is initially installed is configured.

As a method of configuring a tree network, there is a method disclosed in Non-Patent Document 1. The routing disclosed in Non-Patent Document 1 is as follows.
The base station sequentially transmits detection signals to each node. Each node determines whether or not the reception strength of the detection signal is equal to or greater than a threshold value, and only the node that has received the detection signal at a predetermined strength or higher returns a detection response signal to the base station.
This establishes a connection between the base station and the node that has returned the detection response signal.

  Next, the base station sequentially transmits detection signals to the nodes that have not yet been connected through the nodes that have already been connected. Each node determines whether or not the reception strength of the detection signal is equal to or greater than a threshold value, and only the node that has received the detection signal with a predetermined strength or higher receives the detection response signal via the node that is the transmission source of the detection signal. Reply to the base station.

  As a result, the node that cannot be directly connected to the base station is connected to the base station via the node directly connected to the base station.

  By repeating the above procedure, a tree network is configured.

  In the procedure described in Non-Patent Document 1, since the base station centrally controls the signal transmission timing of the nodes, signal collision can be reduced and a tree network can be stably configured even when the number of nodes is large.

  On the other hand, it may be necessary to reconfigure the tree network during operation. This is a case where a node that is no longer needed is deleted, a node fails, or a new node is added.

  A case where a node is deleted will be described as an example. FIG. 1 shows a tree network 30 including nodes 1 to 14 with a base station as a root.

  Here, it is assumed that the node 4 is deleted. When the node 4 is deleted, the nodes belonging to the subtree having the node 4 as a root, that is, the node 7, the node 11, the node 12, and the node 14 lose connection with the tree network 30 and become unconnected nodes.

  Similarly, when a node fails, a node belonging to a subtree having the failed node as a root becomes an unconnected node. In addition, when adding a node, the added node itself becomes an unconnected node.

  In such a case, it is necessary to reconnect an unconnected node to the tree network by reconfiguring the tree network. In that case, it is necessary to reconfigure the tree network in as short a time as possible. This is because it is necessary to minimize the downtime of the service in operation.

  FIG. 24 shows a conventional reconnection method. Conventionally, a method of re-detecting unconnected nodes from the base station one by one and reconfiguring the tree network by the procedure described in Non-Patent Document 1 has been used. In other words, the procedure described in Non-Patent Document 1 is repeated until all nodes are detected or detection is performed via all nodes.

Another example of a conventional network reconfiguration method is “multi-hop wireless network and wireless station” disclosed in Patent Document 1. In the invention disclosed in Patent Document 1, each wireless station autonomously configures a wireless network when each wireless station finds an optimum connection destination (higher connection destination wireless station).
Japanese Patent Laid-Open No. 2001-237764 Takahiro Okuma, Daisuke Kawasaki, Takehiro Hokimoto, Masanobu Arai, “Realization of Power Saving Multi-hop Routing Function by Call ID”, IEICE Technical Report, Vol.103, No.624, January 22, 2004, 39- 42 pages

A problem in using the technique described in Non-Patent Document 1 is that it takes a very long time to reconfigure the tree network. The reason is that unconnected nodes are detected from the base station one by one and reconnected to the tree network.
As described above, it is necessary to reconfigure the tree network in as short a time as possible. The invention described in Non-Patent Document 1 cannot be said to sufficiently satisfy this requirement.

  Further, in the invention described in Patent Document 1, when a certain radio station becomes unable to connect to an upper connection destination radio station, a lower radio station (child radio station) sequentially selects an upper connection destination radio station. I do. For this reason, if the number of radio stations is large, the time required for network reconfiguration will be prolonged.

  Thus, conventionally, a tree network could not be reliably reconfigured in a short period of time.

  The present invention has been made in view of such problems, a network reconfiguration method capable of reliably reconfiguring a tree network in a short time, its program, a computer-readable information recording medium on which it is recorded, and a node, It is an object to provide a base station and a multi-hop network system.

  To achieve the above object, according to a first aspect of the present invention, there is provided a network reconfiguration method in a wireless tree network in which a base station and a plurality of nodes are connected by a wireless communication method. Designating the root of the subtree of the connection as a proxy node of the base station, the step of detecting the connectivity between the own node or a descendant node and the wireless tree network, and the subtree not connected to the tree network. A step of changing the hierarchical structure of the unconnected subtree so that a node belonging to the tree network becomes a root of the unconnected subtree, and a node having the connectivity to the tree network To notify each node on the route from the base station to the base station of the hierarchical structure of the changed subtree. There is provided a network reconfiguration method according to symptoms.

  In the first aspect of the present invention, when deleting a node from the wireless tree network, it is preferable to designate a child node of the node to be deleted as a proxy node. In addition, when adding a node to the wireless tree network, it is preferable to designate the node to be added as a proxy node. In addition, when a node belonging to the wireless tree network fails, it is preferable to designate a child node of the failed node as a proxy node.

  In any of the above configurations of the first aspect of the present invention, in the step of detecting the connectivity with the wireless tree network, the connectivity with the wireless tree network is detected in ascending order of the number of hops with the proxy node. Is preferred.

  In any of the above configurations of the first aspect of the present invention, if a plurality of nodes having connectivity with the wireless tree network are detected in the step of detecting connectivity with the wireless tree network, It is preferable to set a route with a small number of hops to the station as the root of the subtree.

  In order to achieve the above object, the present invention provides, as a second aspect, a program for causing a node to execute a network reconfiguration method in a wireless tree network in which a base station and a plurality of nodes are connected by a wireless communication scheme. A step of designating a wireless tree network and a root of an unconnected sub-tree as a proxy node of a base station to a substantial computer that controls the node, and connectivity between the proxy node or its descendant nodes and the radio tree network And a hierarchical structure of the unconnected subtree such that a node belonging to a subnetwork not connected to the tree network and having connectivity with the tree network becomes a root of the unconnected subtree. Each node in the path from the node having connectivity to the tree network to the base station In contrast, there is provided a program of a network reconfiguration method characterized by and a step of notifying the hierarchical structure of subtrees after the change.

  In the second aspect of the present invention, when the own node is deleted from the wireless tree network, it is preferable to cause a substantial computer to designate a child node as a proxy node. In addition, when the own node is added to the wireless tree network, it is preferable to cause a substantial computer to designate the own node as a proxy node. In addition, when the parent node of the own node fails, it is preferable to cause the substantial computer to designate the own node as the proxy node.

  In any of the above configurations according to the second aspect of the present invention, when the own node belongs to an unconnected subtree, connectivity to the wireless tree network in ascending order of the number of hops with the proxy node is provided to a substantial computer. Is preferably detected.

  In addition, when other nodes belonging to the unconnected subtree also have connectivity with the wireless tree network, the subnode is assigned to the subtree only when the number of hops to the base station is minimum. It is preferable to use a new route.

  In order to achieve the above object, the present invention provides, as a third aspect, information that can be read by a computer in which a program of a network reconfiguration method according to any one of the configurations of the second aspect of the present invention is recorded. A recording medium is provided.

  In order to achieve the above object, according to a fourth aspect of the present invention, there is provided, as a fourth aspect, a node that is connected to a base station by a wireless communication method and constitutes a wireless tree network, wherein As a proxy node of the base station, and when specified as a proxy node, means for requesting confirmation of the presence or absence of connectivity with the radio tree network from the descendant node of the own node, and a radio tree network; If the node belongs to an unconnected subtree, the node having connectivity with the wireless tree network becomes a new route in response to an instruction from the proxy node. Means for changing the hierarchical structure of the unconnected subtree, and when the own node becomes a new route of the unconnected subtree, For each node in the path, there is provided a node, characterized in that it comprises a means for notifying the hierarchical structure of subtrees after the change.

  In the fourth aspect of the present invention, when the own node is deleted from the radio tree network, it is preferable to designate the child node as a proxy node, and the own node is added to the radio tree network. In this case, it is preferable to designate the own node as a proxy node. In addition, when the parent node of the own node fails, it is preferable to designate the own node as a proxy node.

  In any of the above configurations of the fourth aspect of the present invention, when the own node belongs to an unconnected subtree, it is possible to detect connectivity with the wireless tree network in ascending order of the number of hops with the proxy node. Good.

  In any of the above configurations of the fourth aspect of the present invention, when the other nodes belonging to the unconnected subtree also have connectivity with the wireless tree network, the number of hops to the base station is minimum It is preferable that only a new root of the partial tree is obtained.

  In order to achieve the above object, according to a fifth aspect of the present invention, there is provided a base station that forms a wireless tree network together with at least one node connected by a wireless communication method, and is not connected to the wireless tree network. Receives information about the hierarchy structure of the unconnected subtree after the change from the means to specify the root of the subtree as the proxy node of the base station and any node belonging to the unconnected subtree whose hierarchy structure has been changed In this case, the present invention provides a base station having means for updating information representing the hierarchical structure of the tree network in accordance with the received information.

  In order to achieve the above object, as a sixth aspect, the present invention relates to at least one node according to any one of the configurations of the fourth aspect of the present invention and the fifth aspect of the present invention. A multi-hop network system including a base station is provided.

  According to the present invention, a network reconfiguration method capable of reliably reconfiguring a tree network in a short time, its program, a computer-readable information recording medium, and a node, base station, and multihop network system Can provide.

[Principle of the Invention]
In the present invention, the process of reconnecting the node to the tree network is performed in four steps as shown in FIG.
In the first step (initiator designation process), an “initiator” that controls the reconfiguration of the tree network is designated on behalf of the base station. Through the processing in this step, the root of the subtree that has become unconnected to the tree network (hereinafter referred to as “unconnected subtree”) due to node deletion or failure is designated as the initiator.

  In the second step (Neighbor Discovery process), in order to detect connectivity with the tree network, the initiator performs Neighbor Discovery or the descendant node of the initiator performs Neighbor Discovery according to an instruction from the initiator To do. Through the processing in this step, connectivity between any node belonging to the unconnected subtree and the tree network is detected.

  In the third step (partial tree hierarchical structure update process), the hierarchical structure of the unconnected partial tree is updated according to the connectivity with the tree network detected by Neighbor Discovery. Through the processing in this step, the hierarchical structure is updated so that the node that has succeeded in Neighbor Discovery becomes the root of a new unconnected subtree.

  In the fourth step (partial tree reconnection process), an unconnected partial tree is connected to the tree network again. By the processing in this step, the unconnected subtree is connected to the tree network again.

As described above, the tree network needs to be reconfigured when a node is deleted, when a node fails, or when a node is added. Is different. The Neighbor Discovery process, the subtree hierarchical structure update process, and the subtree reconnection process are processes common to all triggers.
The initiator designation process in each case of node deletion, node failure, and node addition will be described in detail later.

  When reconfiguring the tree network, instead of trying to reconnect unconnected nodes in order from the base station (root) as in the conventional method, the initiator is specified by the initiator specification process, and the unconnected node is not connected by the Neighbor Discovery process. The initiator detects the connectivity between any node belonging to the subtree and the tree network by Neighbor Discovery. In the subtree hierarchical structure update process, the hierarchical structure of the unconnected subtree is updated in accordance with the detection result in the Neighbor Discovery process, and the unconnected subtree and the tree network are regenerated in the subtree reconnection process. Connecting.

  Thereby, the number of updates of the routing table of the node can be reduced, and as a result, the time required for reconfiguration of the tree network can be shortened.

  Hereinafter, a preferred embodiment of the present invention based on the above principle will be described.

[First Embodiment]
A first embodiment in which the present invention is suitably implemented will be described.
FIG. 2 shows a tree network including nodes 1 to 14 with a base station as a root.
Each node has a routing table shown in FIG. The routing table includes information on parent nodes and descendant nodes. That is, the information includes the configuration of the subtree having the own node as a root and the parent node.

  FIG. 4 shows the types of signals transmitted and received by the base station and each node.

FIG. 5 shows a configuration of a node applied to the tree network.
The node 500 includes an input unit 501, an output unit 502, an initiator instruction / execution unit 503, a Neighbor Discovery instruction / execution unit 504, a subtree hierarchical structure update unit 505, a storage unit 506, a routing processing unit 507, and a subtree addition unit 508. Have.

The input unit 501 includes a “node deletion signal”, “node failure signal”, “initiator instruction signal”, “update start signal”, “update start instruction signal”, “Neighbor Discovery instruction signal”, “Neighbor Discovery success signal”, “Neighbor Discovery failure signal”, “update signal”, “addition signal”, “update completion signal”, “update completion instruction signal”, etc. are accepted as inputs.
Further, the input unit 501 receives a “deletion start signal” and an “addition start signal” for starting an operation of an initiator instruction / execution unit 503 described later when a node is deleted or a node is added.

  The output unit 502 transmits these signals to the other nodes 500 and the base station 600.

The function of the initiator instruction / execution unit 503 will be described.
First, functions related to the operation at the time of node deletion will be described. The initiator instruction / control unit 503 performs the following operation when deleting a node.
When the input unit 501 receives the “deletion start signal”, the output unit 502 transmits an “update start signal”.
When the input unit 501 receives the “update start signal”, the input node 501 shifts its own node from the operation state to the route update state and does not respond to Neighbor Discovery.
If the own node is a deletion node, after transmitting an “update start signal” to all descendant nodes, the “node deletion signal” includes the ID information of the own node and is transmitted to the parent node by the output unit 502 .
When the input unit 501 receives the “node deletion signal”, the subtree having the deleted node as a root is deleted from the routing table held in the storage unit 506. Further, the output unit 502 transmits a “node deletion signal” to the parent node.
If the local node is a deletion node, after transmitting a “node deletion signal” to the parent node, the output unit 502 is caused to transmit an “initiator instruction signal”.
When the input unit 501 receives the “initiator instruction signal”, the local node is used as an initiator and Neighbor Discovery described later is executed.

Functions related to the operation of the initiator designation / execution unit 503 at the time of a node failure will be described. The initiator instruction / control unit 503 performs the following operation when a node fails.
If the node has found a failure, the subtree having the failure node held in the storage unit 506 as a root is deleted from the routing table held in the storage unit 506. Then, the “node failure signal” is transmitted to the failure discovery node (that is, the node between the parent node of the failure node and the base station).
When the input unit 501 receives the “update start instruction signal”, the subtree having the fault node as the root is deleted from the subtree held in the storage unit 506.
When the input unit 501 receives the “update start instruction signal”, the output unit 502 transmits an “update start signal” to all descendant nodes.
After transmitting the “update start signal” to all the descendant nodes, a “notification completion signal” indicating “the“ update start signal ”has been transmitted to all the descendant nodes” is sent from the output unit 502 to the base station. To send to.
When the input unit 501 receives the “initiator instruction signal”, the local node is set as the initiator.

Functions related to the operation of the initiator designation / execution unit 503 when adding a node will be described. The initiator designation / control unit 503 performs the following operation when adding a node.
When the input unit 501 receives the “addition start signal”, the local node is set as the initiator.

The Neighbor Discovery instruction / execution unit 504 will be described. In the Neighbor Discovery instruction / execution unit 504, if the own node is an initiator, Neighbor Discovery is executed. Further, the initiator transmits a “Neighbor Discovery instruction signal” to the descendant node.
The node that has received the “Neighbor Discovery instruction signal” performs Neighbor Discovery. When Neighbor Discovery succeeds, the result is stored in the storage unit 506, and a “Neighbor Discovery success signal” is transmitted to the initiator. A node that has succeeded in Neighbor Discovery becomes a root of a new subtree (hereinafter, a new root node).
When Neighbor Discovery fails, a “Neighbor discovery failure signal” is transmitted to the initiator.

The subtree hierarchical structure update unit 505 will be described.
The subtree hierarchical structure update unit 505 reflects the hierarchical structure of the subtree updated using the initiator as a route in the routing table according to the result of Neighbor Discovery.
When receiving the “Neighbor Discovery success signal” from the input unit 501, the initiator updates the routing table of its own node. Then, the routing table and the new route node information are included in the “update information”, and the output unit 502 is transmitted to the new parent node.
Here, as the new parent node, a child node having the new root node as a descendant in the old routing table is selected.

When the “update signal” is received from the input unit 501, a child node having the new route node included therein as a descendant node in the old routing table is set as a new parent node. Also, the subtree information included in the “update signal” is added to the routing table.
Then, the information on the routing table of the own node and the information of the new route node are transmitted to the parent node together with the “update signal”.

  When the new route node receives the “update signal” by the input unit 501, the routing table included therein is added to the routing table of the own node. Also, the node detected by Neighbor Discovery is set as a new parent node.

The subtree adding unit 506 will be described.
In the new route node, the output unit 502 transmits the routing table of the own node together with the “addition signal” to the parent node.
The node that has received the “additional signal” adds the routing table information included in the “additional signal” to the routing table of the own node. Then, the content of the received “additional signal” is transmitted to the parent node using the output unit 502.
The new root node that has received the “update completion signal” by the input unit 501 transmits the “update completion signal” from the output unit 502 to all descendant nodes. The node that has received the “update completion signal” shifts from the route update state to the operation state.

  The storage unit 506 holds a result of the routing table Neighbor Discovery.

  The routing processing unit 507 is used when creating a temporary route using a technique disclosed in Non-Patent Document 1 when a node failure described later is performed.

FIG. 6 shows the configuration of base station 600.
The base station 600 includes an input unit 601, an output unit 602, an initiator instruction / execution unit 603, a storage unit 606, a routing processing unit 607, and a partial tree addition unit 608.
The input unit 601 accepts “node deletion signal”, “node failure signal”, “addition signal”, “addition completion signal”, and the like as inputs.

The function of the initiator instruction / execution unit 603 will be described.
When the “node deletion signal” is received by the input unit 601, the subtree having the deletion node as the root is deleted from the routing table held in the storage unit 606.
When the “node failure signal” is received by the input unit 601, the subtree having the failed node as a route is deleted from the routing table held in the storage unit 606. Also, the output unit 602 is used to transmit an “update start instruction signal” to the child node of the failed node.
When the “notification completion signal” is received by the input unit 601, the “initiator instruction signal” is output to the child node of the failed node using the output unit 602.

The function of the subtree adding unit 608 will be described.
The base station that has received the “additional signal” by the input unit 601 adds the routing table information included in the “additional signal” to the routing table of its own node. Then, the output unit 602 transmits an “update completion signal” indicating that the routing table update of the base station is completed to the new route node.

  The storage unit 606 holds a routing table, a result of Neighbor Discovery, and the like.

  The routing processing unit 607 is used when creating a temporary route using a technique disclosed in Non-Patent Document 1 when a node failure described later is performed.

The tree network reconfiguration operation will be described.
First, a procedure for designating an initiator will be described. As described above, the procedure for designating the initiator varies depending on the trigger for starting the operation, and will be described separately.

<Initiator designation procedure when deleting a node>
First, an initiator designation procedure when deleting a node will be described. FIG. 7 shows the flow of an initiator designation operation when deleting a node.
When the deletion node receives the “deletion start signal” (step B1), it transmits an “update start signal” to all descendant nodes (step B2). The node that has received the “update start signal” shifts from the operation state to the route update state as shown in FIG.

  Next, the deletion node transmits a “node deletion signal” to a node between the deletion node and the base station (step B3). The node that has received the “node deletion signal” deletes the subtree having the deletion node as a root from the routing table.

  The deletion node transmits an “initiator instruction signal” that instructs the child node to perform the initiator operation (step B4). The node that receives the “initiator instruction signal” becomes an initiator and controls execution of Neighbor Discovery, which will be described later, and the like (step B5).

<Initiator designation procedure in case of node failure>
Next, an initiator designation procedure when a node fails will be described. FIG. 9 shows the flow of the initiator designation operation at the time of a node failure. In the event of a node failure, the node that has found the failed node (failed node) (that is, the parent node of the failed node) deletes the subtree with the failed node as the root from the routing table of its own node. Then, a “node failure signal” for notifying the occurrence of the failure node is transmitted to each node between the parent node of the failure node and the base station (step C1). The node that has received the “node failure signal” deletes the subtree having the failed node as the root from the routing table.

  As in the case of node deletion, it is necessary to transmit an “update start signal” and an “initiator instruction signal” to a child node of the failed node even when a node fails. However, since there is no route to the child node of the failed node, the base station creates a temporary route to the child node of the failed node by applying the method disclosed in Non-Patent Document 1 (step C2).

At this time, using the method disclosed in Non-Patent Document 1, any node belonging to the subtree having the child node of the failed node as a root is detected. As a result, a temporary path can be formed between the tree network and any node belonging to the subtree having the failed node as a root.
At this time, the detected node is referred to as a transit node. The base station uses this temporary path to transmit an “update start instruction signal” and an “initiator instruction signal” to the child node of the failed node (step C3). At that time, the ID of the transit node is included in the signal.
A node belonging to the subtree having the failed node as a root transfers an “update start instruction signal” and an “initiator instruction signal” that are not addressed to the own node to the parent node.

  In this way, the “update start instruction signal” and the “initiator instruction signal” can be delivered to the child node of the failed node (step C4).

  In addition, the child node of the failed node transmits a “notification completion signal” to the base station, but first transmits it to the transit node included in the “update start instruction signal”. The relay node that has received the “update completion signal” transfers the received signal to the base station using the temporary route (step C5).

  Through the above procedure, the base station and the child node of the failed node communicate using the temporary path until the initiator is designated.

  The base station transmits an “update start instruction signal” to the child node of the failed node and the descendant node of the child node of the failed node using the temporary route. The child node of the failed node that has received the “update start instruction signal” transmits an “update start signal” to all descendant nodes.

  The child node of the failed node notifies the base station that the “update start signal” has been transmitted to all the descendant nodes by using the “notification completion signal”.

  When receiving the “notification completion signal” from the child node of the failed node, the base station transmits an “initiator instruction signal” to the child node of the failed node using the temporary path (step C6).

  The child node of the failed node that has received the initiator instruction signal transmits a “provisional route deletion signal” to each node between the deletion node and the base station in order to delete the temporary route (step C7). Thereby, the temporary route is deleted.

  The node that becomes the initiator (step C8) controls execution of Neighbor Discovery, which will be described later.

<Operation of base station when adding node>
The operation of the base station when adding a node will be described. FIG. 10 shows a flow of operation of the base station when adding a node.
The node that receives the “addition start signal” (step F1) becomes an initiator (step F2).

  As described above, an initiator is designated when a node is deleted, when a node fails, or when a node is added.

  Next, the operation of the Neighbor Discovery execution / instruction of the initiator will be described. 11, 12 and 13 show the flow of Neighbor Discovery execution / instruction operation. The initiator first performs Neighbor Discovery and tries to detect a new connectivity with the tree network (step D1). If Neighbor Discovery is detected (step D2 / Yes), the initiator selects the detected node as a new parent node, and updates the routing table.

  If the initiator fails in Neighbor Discovery (step D2 / No), the “Neighbor Discovery instruction signal” is transmitted in order from the descendant node having the smallest hop count with the initiator, and the descendant node performs Neighbor Discovery ( Step D3).

  If the descendant node has succeeded in Neighbor Discovery (step D4 / Yes), the subtree with the initiator as the root is set to be the root of the new subtree with the descendant node that has succeeded in Neighbor Discovery (hereinafter, the new root node). The hierarchical structure is changed (step D6). Here, along with the change of the hierarchical structure, the routing table is updated between the new root node and the initiator (steps D6 to D12).

  The initiator transmits an “addition signal” requesting to add information of a new subtree to the routing table to a node on the route between the new root node and the base station (including the base station) (steps D13 to D13). D16). Thereby, the routing table of each node in the path | route of a new root node and a base station is updated. In addition, the base station that has received the “addition signal” transmits an “update completion notification” to the new root node (step D17). The new root node that has received the “update completion notification” from the base station transmits an “update completion notification” indicating that the path change has been completed to all descendant nodes (step D18). The state of the node that has received the “update completion notification” shifts from the route update state to the operational state.

[Operation example 1]
Assume that the node 4 is deleted in the tree network 30 shown in FIG.
First, when the node 4 receives the “deletion start signal”, the node 4 transmits an “update start signal” to all descendant nodes, that is, the node 7, the node 11, the node 14, and the node 12.
As illustrated in FIG. 8, the node that has received the update start signal shifts from the operation state to the route update state. Since the node in the route update state does not have reachability to the base station, it does not reply to Neighbor Discovery.

  Next, the node 4 transmits a “node deletion signal” to the nodes on the path from the own node to the base station, that is, the node 1 and the base station. The node (node 1 and base station) that has received the “node deletion signal” deletes the information of the subtree having the deletion node (node 4) as a route from the routing table. At this time, a routing table between the node 1 and the base station is shown in FIG.

  Next, the node 4 transmits an “initiator instruction signal” to the node 7 that is a child node. Thereby, the node 7 becomes an initiator.

  The node 7 that has become the initiator first performs Neighbor Discovery and tries to detect a new connectivity with the tree network 30.

Hereinafter, a case where Neighbor Discovery in the node 7 as an initiator is successful will be described as an example.
When the neighbor is detected, the node 7 selects the detected node as a new parent node, and updates the routing table. Here, it is assumed that the node 3 is detected as a neighbor. The routing table of the node 7 at this time is shown in FIG.

  Next, the node 7 transmits an “additional signal” to a node between the own node and the base station, that is, the node 3, the node 1, and the base station. To the “additional signal”, the routing table information of the own node is added. Receiving the “additional signal”, the node 3, the node 1, and the base station add the subtree information having the node 7 as a route to the routing table. At this time, the routing table of the node 3, the node 1, and the base station is as shown in FIG.

In this way, the routing table of each node on the route from the node 7 to the base station is updated. Finally, the node 7 as an initiator transmits an “update completion signal” to all descendant nodes, that is, the node 11, the node 14, and the node 12.
The node that has received the “update completion signal” shifts from the route update state to the operation state.

Next, a case where Neighbor Discovery in the node 7 that is an initiator has failed will be described.
When the node 7 as the initiator fails in Neighbor Discovery, the initiator transmits “Neighbor Discovery instruction signal” in order from the descendant node having the smallest number of hops, and causes the descendant node to perform Neighbor Discovery. Here, it is assumed that a Neighbor Discovery instruction is issued in the order of node 11 → node 12 → node 13.

As a specific example when the descendant node executes Neighbor Discovery, a case where the nodes 11 and 12 fail in Neighbor Discovery and the node 14 succeeds in Neighbor Discovery will be described.
The node 7 that is an initiator transmits a Neighbor Discovery instruction signal to the node 11. The node 11 that has received the “Neighbor Discovery instruction signal” executes Neighbor Discovery. As a result of executing Neighbor Discovery, the node 11 cannot detect the node, and therefore transmits a “Neighbor Discovery failure signal” to the node 7.

  Next, the node 7 transmits a “Neighbor Discovery instruction signal” to the node 12. The node 12 that has received the “Neighbor Discovery instruction signal” executes Neighbor Discovery. As a result of executing Neighbor Discovery, the node 12 cannot detect the node, and therefore transmits a “Neighbor Discovery failure signal” to the node 7.

  Next, the node 7 transmits a “Neighbor Discovery instruction signal” to the node 14. The node 14 that has received the “Neighbor Discovery instruction signal” executes the Neighbor Discovery. The node 14 holds the detected neighbor and transmits a “Neighbor Discovery success signal” to the node 7 that is the initiator.

  Upon receiving the “Neighbor Discovery success signal” from the node 14, the ode 7 changes the hierarchical structure so that the node 14 becomes the root of the subtree having the node 7 as the root.

  For node 7, the child node having node 14 as a descendant node is node 11. Therefore, the node 11 becomes the new parent node of the node 7. Also, the subtree having the node 11 as a route is deleted from the routing table. The routing table of the node 7 at this time is shown in FIG.

  The node 7 transmits the updated routing table and the ID information of the new root node to the parent node 11 together with “update information”.

  The node 11 that has received the “update signal” sets the node 14 that is a descendant node as a new parent node. Further, the subtree having the node 14 as a route is deleted from the routing table. Then, the received “update signal” information is added to the routing table. The routing table of the node 11 at this time is shown in FIG.

  The node 11 transmits the updated routing table and the ID information of the new root node to the parent node 14 together with the “update information”.

  The node 14 that has received the “update information” adds the information of the routing table included in the received “update signal” to the routing table of its own node.

  Further, the node 14 sets the node 9 detected by Neighbor Discovery as a parent node. The routing table of the node 14 at this time is shown in FIG.

  The node 14 transmits an “additional signal” to nodes (including the base station) on the path between the node and the base station, that is, the node 9, the node 6, the node 3, the node 1, and the base station. As a result, the routing table of each node in the path between the node 14 and the base station is updated. FIG. 20 shows a routing table of node 9, node 6, node 3, node 1, and base station at this time.

  The base station that has updated the routing table according to the received “additional signal” transmits an “update completion signal” to the node 14.

  The node 14 that has received the “update completion signal” transmits the “update completion signal” to all descendant nodes, that is, the node 11, the node 7, and the node 12. The node that has received the “update completion signal” shifts from the path change state to the operation state.

  This completes the operation when deleting a node. FIG. 21 shows a tree network reconfigured in the above operation.

[Operation example 2]
An operation when a node constituting the tree network fails will be described. In the above operation example 1, the node is deleted from the tree network. However, the difference between the operation at the time of node deletion and the operation at the time of node failure or node addition is an operation designated by the initiator. Accordingly, only the operation of initiator designation will be described.

  Assume that the node 4 has failed in the tree network 30 shown in FIG.

  In the case of a node failure, the node that has found the node failure, that is, the node 1 that is the parent node of the failed node (node 4), deletes the subtree having the node 4 as the root from the routing table of its own node. Then, a “node failure signal” is transmitted to the node (that is, the base station) on the path from the node 1 to the base station. The base station that has received the “node failure signal” deletes, from the routing table, the information of the subtree that is routed to the node 4 that is the failed node. The routing table of the node 1 and the base station at this time is shown in FIG.

  The base station that has received the “node failure signal” creates a temporary path between the base station and the node 7 using the technique disclosed in Non-Patent Document 1. For example, it is assumed that the node 12 that is a descendant node of the node 14 is detected from the node 13. In this case, the subsequent “update start instruction signal”, “notification completion signal”, and “initiator instruction signal” are transmitted and received using a temporary path. When the node 7 receives the “initiator instruction signal” and becomes an initiator, the node 7 transmits a “temporary route deletion signal” to the node 7 → node 12 → node 13 → node 8 → node 5 → node 2 → base station. Is deleted.

  The base station transmits an “update start instruction signal” to the node 7 using the temporary route. The node 7 that has received the “update start signal” transmits an “update start signal” to all descendant nodes, that is, the nodes 11, 14, and 12. Then, the node 7 notifies the base station of a “notification completion signal”.

  When receiving the “notification completion signal” from the node 7, the base station transmits an “initiator instruction signal” to the node 7 using the temporary route. The node 7 that has received the “initiator instruction signal” transmits a temporary route deletion request to the base station. And it becomes an initiator and controls execution of Neighbor Discovery.

[Operation example 3]
When a node is added, when the “node addition signal” is received, the added node itself becomes the initiator. The procedures other than the designation of the initiator are the same as those in the first operation example.

  In the tree network according to the present embodiment, when the tree network is reconfigured, the number of node routing table updates can be reduced, and as a result, the time required for reconfiguration of the tree network can be reduced. In addition, if the initiator itself does not have connectivity with the tree network, the connectivity between the descendant node and the tree network is examined, and if there is a node with connectivity, the tree structure is changed using that as a new root Therefore, the unconnected subtree can be reliably connected to the tree network.

[Second Embodiment]
A second embodiment in which the present invention is suitably implemented will be described.
FIG. 23 shows an operation flow of network reconfiguration in the present embodiment.
The difference from the operation of the first embodiment is that, when a plurality of neighbors are detected as a result of neighbor discovery, the node having the smallest number of hops to the base station is selected as the neighbor.

  By selecting the node having the smallest number of hops to the base station as the Neighbor, the number of hops from the new root node to the base station is reduced, and the number of routing table updates can be reduced.

  Thereby, the time required for reconfiguration of the tree network can be further shortened.

[Third Embodiment]
The base station 600 and the node 500 shown in FIG. 5 and FIG. 6 record a program for realizing the function in a computer-readable recording medium in addition to being realized by dedicated hardware. It is also possible to cause the computer to read and function as the base station 600 and the node 500.
As a computer-readable recording medium, in addition to an exchangeable recording medium such as a magnetic disk, a magneto-optical disk, and an optical disk, a recording medium (HD, semiconductor memory, etc.) built in the computer can be applied.

  Furthermore, as in the case of transmitting a program via the Internet, a program is dynamically held for a short time (transmission medium or transmission wave), or a program is held for a certain period of time, such as a memory inside a computer. Including things.

  Even when the functions of the base station 600 and the node 500 are realized by software processing by a computer, the operations are the same, and redundant description is omitted.

Each of the above embodiments is an example of a preferred embodiment of the present invention, and the present invention is not limited to this.
For example, in the tree networks exemplified in the above embodiments, the number of child nodes is two or less, but it is needless to say that a node having three or more child nodes may exist.
Even when two or more nodes are deleted, added, or failed at the same time, the tree network can be reconfigured by the same operation as described above.
As described above, the present invention can be variously modified.

It is a figure which shows the procedure of the tree network reconstruction in this invention. It is a figure which shows an example of a tree network. It is a figure which shows an example of the routing table of each node of a tree network. It is a figure which shows the signal exchanged between each node in the case of reconfiguration of a tree network. It is a figure which shows the structural example of a node. It is a figure which shows the structural example of a base station. It is a figure which shows the flow of operation | movement of the initiator designation | designated process at the time of node deletion. It is a figure showing transition of the state of a node. It is a figure which shows the flow of operation | movement of the initiator designation | designated process at the time of a node failure. It is a figure which shows the flow of operation | movement of the initiator designation | designated process at the time of node addition. It is a figure which shows the flow of a process of the connectivity detection in a subtree, and the reconstruction of a tree structure. It is a figure which shows the flow of a process of the connectivity detection in a subtree, and the reconstruction of a tree structure. It is a figure which shows the flow of a process of the connectivity detection in a subtree, and the reconstruction of a tree structure. It is a figure which shows an example of a routing table. It is a figure which shows an example of a routing table. It is a figure which shows an example of a routing table. It is a figure which shows an example of a routing table. It is a figure which shows an example of a routing table. It is a figure which shows an example of a routing table. It is a figure which shows an example of a routing table. It is a figure which shows the structure of the tree network after a reconfiguration | reconstruction. It is a figure which shows an example of a routing table. It is a figure which shows the flow of a process of the connectivity detection in a subtree, and the reconstruction of a tree structure. It is a figure which shows the procedure of the tree network reconstruction process by a prior art.

Explanation of symbols

501, 601 Input unit 502, 602 Output unit 503, 603 Initiator instruction / execution unit 504 Neighbor Discovery instruction / execution unit 505 Partial tree hierarchical structure update unit 506, 606 Storage unit 507, 607 Routing processing unit 508, 608 Sub tree addition unit

Claims (21)

A network reconfiguration method in a wireless tree network in which a base station and a plurality of nodes are connected by a wireless communication method,
Designating a root of the unconnected subtree with the wireless tree network as a proxy node of the base station;
The proxy node detecting connectivity between the node or a descendant node and the wireless tree network;
Changing the hierarchical structure of the unconnected subtree so that a node belonging to the tree network and an unconnected subtree and having connectivity with the tree network becomes a root of the unconnected subtree; ,
A network reconfiguration method comprising: notifying each node in a path from the node having connectivity with the tree network to the base station of the hierarchical structure of the subtree after the change.   The network reconfiguration method according to claim 1, wherein when a node is deleted from the wireless tree network, a child node of the node to be deleted is designated as the proxy node.   3. The network reconfiguration method according to claim 1, wherein when adding a node to the wireless tree network, the node to be added is designated as the proxy node.   4. The network reconfiguration method according to claim 1, wherein when a node belonging to the wireless tree network fails, a child node of the failed node is designated as the proxy node.   5. The step of detecting connectivity with the wireless tree network includes detecting connectivity with the wireless tree network in ascending order of hop count with the proxy node. The network reconfiguration method according to the item.   When a plurality of nodes having connectivity with the wireless tree network are detected in the step of detecting connectivity with the wireless tree network, a route with a small number of hops to the base station is used as the root of the subtree 6. The network reconfiguration method according to claim 1, wherein the network reconfiguration method is set. A program for causing a node to execute a network reconfiguration method in a wireless tree network in which a base station and a plurality of nodes are connected by a wireless communication method,
A substantial computer controlling the node;
Designating a root of the unconnected subtree with the wireless tree network as a proxy node of the base station;
Detecting connectivity between the proxy node or its descendant nodes and the wireless tree network;
Changing the hierarchical structure of the unconnected subtree so that a node belonging to the tree network and an unconnected subtree and having connectivity with the tree network becomes a root of the unconnected subtree; ,
A step of notifying each node on the path from the node having connectivity with the tree network to the base station of the hierarchical structure of the changed subtree. Program.   8. The program of the network reconfiguration method according to claim 7, wherein when the own node is deleted from the wireless tree network, the substantial computer is caused to designate a child node as the proxy node.   9. The program of the network reconfiguration method according to claim 7, wherein when the own node is added to the wireless tree network, the substantial computer is caused to designate the own node as the proxy node.   10. The network reconfiguration method according to claim 7, wherein when a parent node of the own node fails, the substantial computer is caused to designate the own node as the proxy node. 11. program.   8. When the own node belongs to the unconnected subtree, the substantial computer is caused to detect connectivity with the wireless tree network in ascending order of the number of hops with the proxy node. The program of the network reconfiguration method according to any one of 10.   When other nodes belonging to the unconnected subtree also have connectivity with the wireless tree network, the substantial computer is assigned the own node only when the number of hops to the base station is minimum. 12. The network reconfiguration method program according to claim 7, wherein a new root of the subtree is used.   13. A computer-readable information recording medium on which a program for the network reconfiguration method according to claim 7 is recorded. A node that is connected to a base station in a wireless communication scheme to form a wireless tree network,
Means for designating the root of the base station as a root of the subtree not connected to the wireless tree network;
Means for requesting confirmation of the presence or absence of connectivity with the wireless tree network to a descendant node of the own node when designated as the proxy node;
Means for confirming the presence or absence of connectivity with the wireless tree network;
When the own node belongs to the unconnected subtree, in response to an instruction from the proxy node, the node having connectivity with the wireless tree network becomes a new route so that the unconnected subtree A means of changing the hierarchical structure;
Means for notifying each node in the path from the self-node to the base station of the changed sub-tree hierarchical structure when the self-node becomes a new route of the unconnected sub-tree. A node characterized by having.   15. The node according to claim 14, wherein when the own node is deleted from the wireless tree network, a child node is designated as the proxy node.   The node according to claim 14 or 15, wherein when the own node is added to the wireless tree network, the own node is designated as the proxy node.   The node according to any one of claims 14 to 16, wherein when the parent node of the own node fails, the own node is designated as the proxy node.   18. The connectivity with the wireless tree network is detected in order from the smallest number of hops to the proxy node when the own node belongs to the unconnected subtree. 18. Nodes.   When other nodes belonging to the unconnected subtree also have connectivity with the wireless tree network, it becomes a new route of the subtree only when the number of hops to the base station is minimum. 19. A node according to any one of claims 14 to 18 characterized in that A base station that forms a wireless tree network with at least one node connected by a wireless communication method,
Means for designating the root of the base station as a root of the subtree not connected to the wireless tree network;
When the information about the hierarchical structure of the unconnected subtree after the change is received from any node belonging to the unconnected subtree whose hierarchical structure has been changed, the tree network according to the received information And a means for updating information representing the hierarchical structure of the base station.   A multi-hop network system comprising at least one node according to any one of claims 14 to 19 and a base station according to claim 20.

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