JP2013207399A - Cluster tree network and address update method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cluster tree network capable of flexibly corresponding to an installation density of node.SOLUTION: In a cluster tree network, a network management server makes a tree-like connection with a plurality of nodes making itself as a top of the connection, and address of each node includes route information for reaching the node. The cluster tree network comprises: a change condition determination part 13 to determine whether an address system change condition is satisfied or not, in which the address system change condition is to be satisfied when a node number is increased; an address system change part 14 to change the address system so as to decrease a maximum allowable hop number when the address system change condition is determined to be satisfied; and an address update part 23 to update an address of a node according to the changed address system.

Description

  The present invention relates to a cluster tree network, and more specifically, a cluster tree network in which a plurality of nodes are connected in a tree shape with a network management server as a vertex, and each node address includes path information to the node, and an address It relates to the update method.

  Conventionally, a cluster tree network is known as a network connecting a plurality of nodes and a network management server. FIG. 13 is a network configuration diagram showing the configuration of the cluster tree network. In the example of FIG. 13, nodes 1 to 10 are connected in a tree shape with the network management server 100 as a vertex. Each node 1-10 is connected to one or more other nodes, but the direction is defined for the connection. In other words, each of the nodes 1 to 10 distinguishes whether the connected node is a parent node or a child node. Each of the nodes 1 to 10 has one parent node. Among the plurality of nodes, the branch node has one or a plurality of child nodes, and the leaf node has no child nodes but only a parent node.

  Such a cluster tree network can be applied as, for example, a sensor network. In this case, sensors are connected to the nodes 1 to 10, respectively. By using the cluster tree network structure, each node 1-10 transmits a sensor detection value to the network management server 100, and the network management server 100 collectively manages the sensor detection value at each node. it can. For example, if a sensor for metering electricity or gas is adopted as a sensor and the nodes 1 to 10 are dwelling units, information on electricity and gas usage fees at each dwelling unit can be collected in a batch by the network management server 100, and the meter reader Does not need to go through each dwelling unit.

  In such a cluster tree network, an address partially including the address of the parent node can be adopted as the address of each node (see, for example, Patent Document 1). FIG. 14 is a diagram illustrating a specific example of an address. In the example of FIG. 14, the address is 8 digits. In the address 1000 of the example of FIG. 14, the lowest number 1001 that is not “00” is a characteristic part of the own node address as seen from the parent node. The upper part 1002 is a part indicating the address of the parent node. Further, a portion 1003 excluding the lowest part of the portion 1002 indicating the address of the parent node is a portion indicating the address of the parent node of the parent node.

  Specifically, the lowest number “02” that is not “00” is the characteristic part of the own node address seen from the parent node, and the higher part “01: 02: 01: 01” The effective part of the address, the part “01:02:01” excluding the lowest part “01” of the part “01: 02: 01: 01” indicating the address of the parent node is the address of the higher-order node of the parent node Is the effective part of In the specification and drawings of the present application, “:” used when describing an address is a notation for the purpose of indicating the path of the node as described above, and is equivalent to “:” in the actual address. Information is not included. In addition, the address is described in hexadecimal notation. In hexadecimal notation, “0x” is usually added to the head like “0x01”. However, in the specification and drawings of the present application, this “0x” is omitted.

  According to such an address system, each node's address includes the address information of the upper node, and the address information of the upper node includes the address information of the upper node. Therefore, the address of each node indicates the path information from the network management server to the node.

  The network management server 100 stores the addresses of all child nodes. Each node stores an address of its own parent node and an address of a child node. When transmitting data to a specific node, the network management server 100 specifies and transmits the address of the destination child node to the highest node. FIG. 15 shows an example in which data is transmitted from the network management server 100 to the node 10 having the address “01: 02: 01: 01: 02: 00: 00: 00”. In the example of FIG. 15, the network management server 100 transmits data using the address “01: 02: 01: 01: 02: 00: 00: 00” of the node 10 as a transmission address.

  The node 1 receives the transmission data including the address “01: 02: 00: 01: 02: 00: 00: 00” as the transmission address, and receives its own address “01: 00: 00: 00: 00: 00: 00”. Compared with “0:00”, the transmission address includes its own address, so this transmission data is transmitted. The node 2 and the node 3 that are child nodes of the node 1 compare their own addresses with the transmission address “01: 02: 01: 01: 02: 00: 00: 00”. In node 2, since its own address is “01: 01: 00: 00: 00: 00: 00”, since this address is not included in the transmission address, node 2 stores the received transmission data. Discard. In the node 3, the self address is “01: 02: 00: 00: 00: 00: 00”, and since this address is included in the transmission address, the node 3 further transfers this data. Send as much as possible.

  Similarly, the node 6, the node 8, and the node 10 receive the transmission data transferred in order. When the transmission data arrives at the node 10, the node 10 receives the transmission data as data addressed to itself because the transmission address included in the transmission data matches the own address.

  In this way, according to the address system in which route information is included in the address, each node only needs to manage the address of its own child node, and each node needs to store the routing table of all nodes. This eliminates the load on each node addressing and routing.

  In the address system as described above, if the maximum allowable hop count (maximum allowable hop count) is increased, the child nodes that can be connected to one branch node (a node that can have child nodes) are limited. That is, assuming that each of the addresses shown in FIG. 14 separated by “:” is a place and each place is 1 byte, since this address is the 8th place, it becomes 8 bytes. Since the number of places in the address is the maximum allowable hop count, the maximum allowable hop count in the address system of FIG. 14 is 7 hops. Also, since each rank is 1 byte (0 to 255), one branch node can have 254 child nodes (one for its own node and one for broadcasting). In this 8-byte address, if the maximum allowable hop count is increased to 15, for example, 8 bytes are maintained as a whole, each rank becomes 0-15, and the branch node can have only 14 child nodes at the maximum.

  Therefore, when the installation density of nodes increases, a large number of branch nodes are required to connect the nodes to this cluster tree network, resulting in interference between the branch nodes and existing around the branch nodes. A situation occurs in which the node to be connected cannot be connected to the cluster tree network.

  In order to deal with such a problem, in the network of Patent Document 2, in the ZigBee mesh network, the installation density of nodes around the own node is inferred based on the neighboring node information of 1 hop ahead and 2 hop ahead, and the density is If it is higher, the packet transmission interval is extended.

JP 2010-11084 A JP 2011-55394 A

  However, according to the technique of Patent Document 2 described above, the node installation density increases and the packet transmission interval becomes longer. As a result, the communication time required to transmit the same amount of data becomes longer. There is a problem of end. The technique of Patent Document 2 described above relates to a mesh network as described above. However, if this technique is applied to a cluster tree network, the allocation at the time of transmitting data in a time-sharing manner decreases as the installation density increases. As a result, there also arises a problem that the communication time required for data transmission becomes long.

  Therefore, an object of the present invention is to provide a cluster tree network that can flexibly cope with the installation density of nodes.

  The cluster tree network of the present invention is a cluster tree network in which a plurality of nodes are connected in a tree shape with a network management server as a vertex, and the address of each node includes path information to the node, and the increase in the number of nodes A change condition determination unit that determines whether or not an address system change condition that is satisfied by the above condition is satisfied, and the address system so that the maximum allowable hop count is reduced when it is determined that the address system change condition is satisfied And an address updating unit for updating the address of the node in accordance with the changed address system.

  According to this configuration, when the number of nodes increases, the number of nodes that can be connected is increased by changing the address system. Therefore, in order to increase the number of nodes that can be connected, the number of divisions in time division transmission is increased. The number of nodes that can be connected can be increased without increasing the communication speed.

  In the above cluster tree network, the address system change condition may be that the installation density of the nodes exceeds a predetermined threshold.

  According to this configuration, even if the number of nodes that can be newly connected is limited due to the high density of nodes and the occurrence of branch nodes that cannot have any more child nodes, the address system By changing, the number of connectable nodes can be increased.

  In the cluster tree network, the node installation density may be the number of nodes installed per unit area in a field of a repeater that is a node directly connected to the network management server.

  According to this configuration, the node installation density can be obtained by simple calculation.

  In the cluster tree network described above, the installation density of the nodes is obtained by counting the number of nodes in the field of the plurality of repeaters according to the proportion shared with other repeaters. It's okay.

  According to this configuration, it is possible to appropriately obtain the node installation density even when the fields of a plurality of repeaters partially overlap.

  In the above cluster tree network, the installation density of the nodes may be obtained for each node.

  According to this configuration, the address can be updated by changing the address system of only a part of the plurality of nodes constituting the cluster tree network.

  In the above cluster tree network, the installation density of the nodes required for each node is the number of nodes installed per unit area in the field of the relay directly connected to the network management server, and the connection of the nodes It may be obtained based on the number of finished child nodes.

  According to this configuration, it is possible to determine whether or not to change the address system based on the overall installation density of the network below the repeater and the installation density around the node.

  In the cluster tree network described above, the installation density of the nodes obtained for each node may be obtained based on the number of installed nodes per unit area within the node communication radius.

  According to this configuration, it is possible to determine whether or not to change the address system based on the installation density around the node.

  In the cluster tree network described above, the address system change condition may be that the number of child nodes of a repeater that is a node directly connected to the network management server exceeds a threshold value.

  According to this configuration, it is possible to determine whether or not to change the address system very easily.

  In the cluster tree network described above, the address system change condition may be that the network management server receives a notification that a new node could not be added from the node.

  According to this configuration, the address system can be changed when a new node cannot be actually added at each node.

  In the above cluster tree network, the address system changing unit changes the address system to increase the number of bits of a part of the node address, and the address update unit is configured to change the address of the node address. Increase the number of bits in some places, bit-shift the bits in some places, and update the address to delete the least significant bit of the address, and the node with the maximum allowed hop count The address update unit updates the address by changing the parent node.

  According to this configuration, the maximum allowable number of hops decreases, and the number of bits in a part of the address increases, so that the total number of connectable nodes can be increased as a whole.

  In the above cluster tree network, the address system changing unit may not add a node having a node density higher than the threshold and a node lower than the threshold or a new node required for each node. The address system of the notified node and lower nodes may be changed.

  According to this configuration, the address system can be changed only in a part necessary for increasing the number of connectable nodes in the cluster tree network.

  In the cluster tree network described above, when there are a plurality of nodes that have notified that a new node could not be added, the address system changing unit has addresses of nodes with lower installation density and lower-level nodes. You may change the system.

  According to this configuration, the address system can be changed only in a part necessary for increasing the number of connectable nodes in the cluster tree network.

  Another aspect of the present invention is an address updating method in a cluster tree network in which a plurality of nodes are connected in a tree shape with a network management server as a vertex, and the address of each node includes path information to the node. When the address update method determines that the address system change condition is satisfied in the change condition determination step and the change condition determination step for determining whether or not the address system change condition to be satisfied by the increase of the nodes is satisfied, The address system changing step for changing the address system so as to reduce the maximum allowable hop number and the address updating step for updating the address of the node according to the changed address system are included.

  Even with this configuration, when the number of nodes increases, the number of connectable nodes is increased by changing the address system, so the number of divisions in time division transmission is increased to increase the number of connectable nodes. Therefore, the number of nodes that can be connected without increasing the communication speed can be increased.

  According to the present invention, when the number of nodes is increased, the number of connectable nodes is increased by changing the address system. Therefore, in order to increase the number of connectable nodes, the number of divisions in time division transmission is set. The number of nodes that can be connected can be increased without increasing the communication speed.

The block diagram which shows the structure of the network management server in embodiment of this invention Diagram showing the result of connection simulation considering interference (when node installation density is low) Diagram showing the result of connection simulation considering interference (when node installation density is high) Partial enlarged view of connection simulation result considering interference (when node installation density is high) The figure which shows the specific example of the node management table in embodiment of this invention The block diagram which shows the structure of the node in embodiment of this invention (A) The figure which shows the specific example of the determination example 1 of the address system change condition in embodiment of this invention (b) The figure which shows the specific example of the determination example 2 of the address system change condition in embodiment of this invention (A) The figure which shows the specific example (before change) of the change of the address system in embodiment of this invention (b) The figure which shows the specific example (after change) of the change of the address system in embodiment of this invention (A) The figure which shows the specific example (before change) of the address update by the change of the address system in embodiment of this invention (b) The specific example (after change) of the address system by the change of embodiment of this invention Figure showing The figure explaining the alternative accompanying the change of the address system in embodiment of this invention The block diagram which shows the structure of the node in the modification of embodiment of this invention. Figure showing a specific example of address information Network configuration diagram showing the configuration of a cluster tree network Figure showing a specific example of an address Network configuration diagram showing an example of transmitting data from a network management server to a specific node

  Hereinafter, a cluster tree network according to an embodiment of the present invention will be described with reference to the drawings. The cluster tree network according to the embodiment of the present invention has a configuration in which a network management server is used as a vertex and a plurality of nodes are connected in a tree shape under the network management server, as in the prior art.

  In the following description, the connection between nodes is also referred to as a link. In the following embodiments, the nodes are connected to each other wirelessly, and the highest node (relay device) and the network management server are connected by wire. However, the present invention is not limited to this, and some or all of the nodes are connected. They may be connected to each other by wire, or the highest node and the network management server may be connected wirelessly. In the following description, transmission from the network management server to the node is referred to as downlink transmission, and transmission from the node to the network management server is referred to as uplink transmission.

  Further, in the following description, the terms child node and parent node, upper and lower, are relative concepts viewed from a certain node or network management server. Therefore, a certain node becomes a child node when viewed from the next higher node, and becomes a parent node when viewed from the next lower node. Further, data transfer at each node when data is transmitted from the network management server to a certain node or from a certain node to the network management server is also referred to as a hop, and the number of transfers from the transmission source is also referred to as a hop number. A cluster tree network is a type of multi-hop network that transmits data by multiple hops. A node having child nodes is called a branch node, and a node having no child nodes is called a leaf node.

  In the following, an embodiment of the present invention that solves the problem after analyzing the situation where the node cannot be connected to the cluster tree network when the installation density of the node becomes high will be described.

  2 and 3 are diagrams illustrating connection results in consideration of interference. FIG. 4 is a partially enlarged view of FIG. In FIG. 2 and FIG. 3, several types of frequency bands are used in order to avoid interference, and it is shown that different frequency bands are assigned to the solid line, the chain line, the one-dot chain line, and the two-dot chain line, respectively.

FIG. 2 shows a case where the node installation density is low (for example, the node installation density is 360 / km2) and the maximum allowable hop count is set to 8 in advance, while FIG. 3 shows that the node installation density is high. (For example, the node installation density is 640 / km ² ) and the maximum number of child nodes in each rank from the first hop to the fourth hop is 254, and the maximum number of child nodes in each rank after the fifth hop is 14 And the maximum allowable hop count is set to 9.

  FIG. 2 shows that 997 nodes can be connected with respect to 1000 nodes in the figure, but the three nodes surrounded by a circle at the upper left cannot be connected. This is probably because the nodes around these nodes have already reached the maximum allowable hop count. Further, FIG. 3 shows that 997 nodes can be connected to 1000 nodes in the figure, but the three nodes surrounded by a circle at the lower left cannot be connected. This is presumably because the nodes around these nodes already have the maximum number of child nodes.

  As shown in FIG. 2 and FIG. 3, in the relationship between the maximum allowable hop count for each node installation density and the number of connectable nodes, it is possible to connect to one branch node by extending the hop without changing the address size. The number of child nodes decreases. Therefore, as the node installation density increases, the number of branch nodes increases, and eventually the available frequencies are used up. As a result, a node that cannot be connected even at a node within a connectable distance appears.

  Based on such a situation, in the present embodiment, the address system is changed so as to change the maximum allowable number of hops depending on whether or not an address system change condition that will be satisfied by an increase in the number of nodes is satisfied. Hereinafter, the cluster tree network according to the embodiment of the present invention will be described in detail.

  FIG. 1 is a block diagram showing the configuration of the network management server according to the embodiment of this invention. The network management server 110 includes a transmission / reception unit 11, a node management table storage unit 12, a change condition determination unit 13, and an address system change unit 14. The transmission / reception unit 11 transmits / receives data to / from the repeater. The transmission / reception unit 11 normally receives data (for example, sensor detection values such as meter reading information) transmitted by uplink transmission from a node in the tree. Further, in downlink transmission, the transmission / reception unit 11 transmits transmission data (for example, an instruction to change an address system to be described later) to all nodes in the tree or a specific part of nodes. When transmitting data to a specific node, the transmission / reception unit 11 transmits the transmission data with the address of the specific node added as a transmission address. Transmission data consists of a header part and a data part, and a transmission address is given to the header part of transmission data.

  The node management table storage unit 12 stores a node management table. In the node management table, node IDs and addresses of nodes in the cluster tree network are associated with each other. FIG. 5 is a diagram illustrating a specific example of the node management table. In this example, the address shows an address system in which each rank is 1 byte and the maximum allowable hop count is 7 hops.

  The change condition determination unit 13 determines whether or not the address system change condition is satisfied. The address system change condition will be described later. The address system change unit 14 changes the address system of some or all nodes when the change condition determination unit 13 determines that the address system change condition is satisfied. Specifically, the address system changing unit 14 changes the address system so as to decrease the maximum allowable hop count when the installation density increases. Details of the change of the address system will be described later.

  FIG. 6 is a block diagram showing the configuration of the node. The node 210 includes a transmission / reception unit 21, a reception determination unit 22, an address update unit 23, and a self address storage unit 24. In the case of downlink transmission, the transmission / reception unit 21 receives transmission data from the parent node and extracts necessary information. In the case of uplink transmission, the transmission / reception unit 21 receives transmission data from the child node, and transmits necessary information. Extract. The own address storage unit 24 stores the address of the node.

  In the case of downlink transmission, the reception determination unit 213 determines the transmission destination by referring to the own address stored in the own address storage unit 212 based on the data of the header part of the transmission data received from the parent node. . Specifically, depending on whether or not the own address matches the upper part of the header data of the transmission data (that is, whether or not the own address is included in the header data) It is determined whether or not transmission data is received. When the own address matches the upper part of the header data of the transmission data, the reception determining unit 213 further transfers the data, and the own address is the same as the header data of the transmission data. If they match completely, the transmission data is received as the data addressed to itself, and the self address does not match the upper part of the header data of the transmission data (the header of the transmission data If the address is not included in the part), the received data is discarded.

  The address update unit 23 updates the own address stored in the own address storage unit 24. The address update by the address update unit 23 will be described later.

  As described above, in the cluster tree network according to the present embodiment, the address system is changed based on whether or not the address system change condition is satisfied. First, the address condition change condition and the determination as to whether the condition is satisfied in the change condition determination unit 13 will be described.

(Example of address system change condition judgment 1)
In this example, the field is determined for each repeater connected to the network management server 110. Information of this field is stored in the node management table storage unit 12. For each repeater, the change condition determination unit 13 determines the size of the field stored in the node management table storage unit 12 and the number of nodes included in the node management table stored in the node management table storage unit 12, that is, node installation Based on the number, the node installation density is calculated by the following equation (1).
Installation density = number of nodes installed / field size (1)
FIG. 7A is a diagram illustrating a specific example of the first determination example. In the example of FIG. 7A, since the field size is 1 km × 1 km and the number of installed nodes is 4, the installation density is 4 / km ² . Note that the repeater does not count as a node.

  The change condition determination unit 13 holds a threshold value for installation density. The change condition determination unit 13 determines that the address system change condition is satisfied when the installation density calculated by the above equation (1) exceeds the installation density threshold, and the address system change unit 14 determines that. The address system changing unit 14 changes the address system.

(Example 2 of address system change condition determination)
This example is a modification of the above determination example 1, and appropriately determines the installation density when the fields of a plurality of repeaters partially overlap. FIG. 7B is a diagram illustrating a specific example of the determination example 2. In the example of FIG. 7B, the relay X1 field includes eight nodes, but four of these nodes also belong to the relay X2 field. As shown in FIG. 7B, when the fields of a plurality of repeaters partially overlap, the installation density of nodes is calculated by the following equation (2) in consideration of the number of installations for each field. .
Installation density = (Number of non-overlapping nodes installed / field size) + (Number of overlapping nodes installed / duplicate / field size) (2)

  Here, the number of installed non-overlapping nodes is the number of installed nodes belonging to only one repeater field, and the number of installed redundant nodes is the number of installed nodes belonging to a plurality of repeater fields. It is. That is, nodes belonging to a plurality of repeater fields are not counted as one node, but are shared with other repeaters (equal in the present embodiment). Count the number. In the example of FIG. 7B, four of the nodes included in the field of the repeater X1 belong to the field of the repeater X2 and belong to the field of two repeaters in total. , Count as 1/2.

  The change condition determination unit 13 holds a threshold value for installation density. The change condition determination unit 13 determines that the address system change condition is satisfied when the installation density calculated by the above equation (2) exceeds the installation density threshold, and the address system change unit 14 Notice.

(Example of address system change condition judgment 3)
In this example, the installation density is obtained for each node. Specifically, a constant multiple of the number of connected child nodes of the node is added as a weight to the installation density according to the determination example 1 or the determination example 2 for each node. That is, the change condition determination unit 13 calculates the installation density of each node by the following equation (3).
Installation density of each node = Installation density of determination example 1 or determination example 2 + α (number of connected child nodes) (3)
Here, α is a constant.

  The change condition determination unit 13 obtains the installation density for each node according to the equation (3), and compares it with the threshold given as the address system change condition. When there is a node whose installation density exceeds the threshold, the change condition determination unit 13 determines that the address system change condition is satisfied, and notifies the address system change unit 14 of it.

(Example 4 of address system change condition determination)
Also in this example, the installation density is obtained for each node. Specifically, the installation density is calculated by the following equation (4) from the number of nodes included in the communication radius of each node.
Installation density of each node = number of nodes included in communication radius / communication radius (4)
Here, the communication radius may be common to each node. In this case, the density determination unit 13 may have information on the communication radius. Further, the communication radius may be different for each node. In this case, information on the communication radius is associated with each node ID in the node management table.

  The change condition determination unit 13 obtains the installation density for each node according to the equation (4), and compares it with the threshold given as the address system change condition. When there is a node whose installation density exceeds the threshold, the change condition determination unit 13 determines that the address system change condition is satisfied, and notifies the address system change unit 14 of it.

(Example 5 of address system change condition determination)
In this example, whether or not the address system change condition is satisfied is determined based on the number of nodes connected to each repeater, that is, the number of child nodes of each repeater. The change condition determination unit 13 refers to the node management table stored in the node management table storage unit 12 to obtain the number of child nodes for each repeater. Then, the change condition determination unit 13 compares the acquired number of child nodes with a predetermined threshold value. The change condition determination unit 13 determines that the address system change condition is satisfied when there is a repeater whose number of child nodes exceeds the threshold value, and notifies the address system change unit 14 of the determination.

  Next, address update processing in the address system changing unit 14 will be described. As described above, in the cluster tree network according to the present embodiment, the address system is changed so as to change the maximum allowable hop count. The address system changing unit 14 changes the address system when the change condition determining unit 13 determines that the address system changing condition is satisfied and notifies that fact. Here are some examples.

  FIG. 8 is a diagram showing a change of the address system in the present embodiment. FIG. 8A shows the address system before the change, and FIG. 8B shows the address system after the change. As shown in FIG. 8A, before the change, the number of bits was evenly allocated to each byte, but when the address system change condition is satisfied, the address system change unit 14 As shown in b), the second place of the address (the place immediately below the repeater) is changed to 2 bytes. As a result, the maximum allowable number of hops is reduced by 1, and the maximum allowable number of hops that was 7 hops before the change shown in FIG. 8A is reduced to 6 hops.

  The transmission / reception unit 11 delivers an address update instruction together with the address system changed by the address system change unit 14 to a lower node through the corresponding relay. Upon receiving this address update instruction, the address update unit 23 of the node 210 updates the address and notifies the network management server 110 of the new address. In the network management server 110, the transmission / reception unit 11 receives this notification and updates the node management table.

  FIG. 9 is a diagram showing a specific example of address update by changing the address system. FIG. 9A shows the address before the change, and FIG. 9B shows the address after the change. In the example of FIG. 8, since the number of second-order bits immediately below the repeater is increased, the address “01: 01: 00: 00: 00: 00: 00” of the first hop node is “ 01: 0001: 00: 00: 00: 00 ”. Similarly, for the nodes below that, the second place “01” is changed to “0001” and the last place is deleted.

  FIG. 10 is a diagram for explaining an alternative associated with a change in the address system. As described above, since the last place of each node is deleted by changing the address system, the node with the maximum allowable number of hops becomes the same as the address of its parent node by this address update. In order to avoid this, in the cluster tree network of this example, the address is updated as follows.

  The address system changing unit 14 distributes an instruction for changing the address system to reduce the number of hops to all nodes. Upon receiving the instruction, the address update unit 23 of the node 210 updates the address as follows. First, nodes higher than the second tier from the maximum allowable hop count, that is, nodes higher than the sixth hop when the maximum allowable hop count is 7 hops (nodes from the first hop to the fifth hop) are as follows: As shown in FIG. 8, the address is updated by bit-shifting and deleting the last digit.

  If the node at the second stage (sixth stage hop) from the maximum allowable hop count is a leaf node (a node that does not have a child node), it can be bit-shifted and deleted at the last place in the same way as the upper node. , Update the address. If the node of the second tier (the sixth hop) from the maximum allowable hop count is a branch node (a node having a child node), the node is a higher-order node than the original parent node and can be connected. Search for surrounding nodes.

  As a result of the search, if there is a node that can connect a child node of two or more hops, the branch node in the second tier from the maximum allowable hop count substitutes the connectable node as a new parent node. The new parent node issues a new address to the replaced node, and the replaced node stores the issued new address in its own address storage unit 24. The replaced node notifies the child node of the new own address. The child node that has received the notification updates its own address so as to include the address of the replaced parent node, and stores it in its own address storage unit 24.

  As a result of the search, if there is no node that can connect a child node with two or more hops, the branch node in the second tier from the maximum allowable number of hops separates the child node, bit-shifts only its own address, and moves to the last position. Update the address by deleting. In the example of FIG. 10, since the node B6 of the sixth hop has no nodes that can connect child nodes of two or more hops around it, the node B7 of the seventh hop that is a child node is separated and its own address Is updated by bit-shifting and deleting the last digit “00”.

  As a result of the search, if there is no node that can connect a child node of two or more hops, the node with the maximum allowable number of hops, that is, the lowest-order node searches for a connectable surrounding node, and finds the connection found The possible node is replaced with a new parent node. The new parent node issues a new address to the lowermost node that has been replaced, and the lowermost node that has performed the replacement stores the issued new address in its own address storage unit 24. In the example of FIG. 10, the lowermost 7th hop node B7 searches for connectable surrounding nodes and the 5th hop node A5 is connectable. doing.

  As described above, when the address system change condition such as the increased node density is satisfied, the number of connectable nodes can be increased by changing the address system to reduce the maximum allowable hop count. Yes. After the address system is changed as described above, if a node that cannot be connected due to an increase in the number of nodes occurs, the address system is changed so as to further reduce the maximum allowable hop count. When the maximum allowable hop count is further reduced after the change in the example of FIG. 8, the address system is changed so that the number of bits of the second hop is 2 bytes and the sixth hop that is the lowest is deleted. change. In the same manner, the address system is changed in accordance with the increase in node installation density.

  As described above, according to the cluster tree network of the present embodiment, when an address system change condition such as an increase in the installation density of nodes is satisfied, the address system can be changed by changing the address system. In order to increase the number of nodes that can be connected, the number of divisions in time division transmission is not increased to increase the number of nodes that can be connected, and therefore the number of nodes that can be connected without increasing the communication speed is increased. it can.

  In the above embodiment, five examples have been described as examples of determining the installation density. Below, the further modification of judgment of installation density is demonstrated.

(Modification example of judgment of address system change condition)
In the modification, the network management server 110 changes the address system when the parent node finds a child node that cannot be connected and notifies the network management server 110 of the child node. FIG. 11 is a block diagram illustrating a configuration of a node in the modification. The node 220 of the modification includes a child address storage unit 25 and an update determination unit 26 in addition to the configuration of the node 210 of the above embodiment. The child address storage unit 25 stores a child address table in which node IDs and addresses of all child nodes are associated with each other. When the child address storage unit 25 and the child node addition determination unit 26 receive a request from a newly added node (new node) to become the parent node of the new node, that is, the node becomes a parent node candidate. Used in some cases.

  In this modification, in the self-address storage unit 24, as the address information, in addition to the self-address, “the characteristic part start bit of the self-address” and “the number of bits of the characteristic part of the self-address” for the eight bytes constituting the self-address And “the number of bits of the characteristic part of the address of the child node” are stored. FIG. 12 is a diagram illustrating a specific example of address information. In the example of FIG. 12, the address of the node A1 is “01: 0001: 00: 00: 00: 00”, and the characteristic part of the own address (part different from the parent node) is the second The first place is “0001”. This node A1 has a node AA1 and a node AB1 as child nodes.

  The address of the node AA1 is “01: 0001: 01: 00: 00: 00” including all effective parts (higher parts that are not zero) of the address of the node A1 that is the parent node. Since the characteristic part of the own address of this node AA1 is “01” in the third place, the “characteristic part start bit of the own address” is the 25th bit (8 bits × 3 digits + 1). Also, “the number of bits of the feature part of the own address” is 8 bits of the third place “01”, and “the number of bits of the feature part of the address of the child node” is 8 bits of the fourth place “00”. is there. Therefore, the self address storage unit 24 of the node AA1 stores information such as the characteristic part start bit of the self address: 25, the number of bits of the characteristic part of the self address: 8, and the number of bits of the characteristic part of the address of the child node: 8. Has been.

  Similarly, the address of the node AB1 is “01: 0001: 02: 00: 00: 00: 0” including all effective parts (higher parts that are not zero) of the address of the node A1 that is the parent node. Since the characteristic part of the own address of the node AB1 is “02” in the third place, the “characteristic part start bit of the own address” is the 25th bit. In addition, “the number of bits of the feature part of the own address” is 8 bits of the third place “02”, and “the number of bits of the feature part of the address of the child node” is 12 bits of the fourth place “000”. is there. Accordingly, the own address storage unit 24 of the node AB1 stores information such as the feature part start bit of the own address: 25, the number of bits of the feature part of the own address: 8, and the number of bits of the feature part of the address of the child node: 12. Has been.

  Here, the number of bits of the characteristic part of the address of the child node represents the number of child nodes that the node can have (maximum number of child nodes). When the address update unit 23 receives a request from the new node to become a parent node, that is, when the own node becomes a parent node candidate, the child node addition determination unit 26 stores the child stored in the child address storage unit 25. With reference to the address table and the address information stored in the own address storage unit 24, it is determined whether or not to add a new node as a child node.

  Specifically, the child node addition determining unit 26 determines whether or not the number of child nodes included in the child address table has reached the maximum number of child nodes determined by “the number of bits of the characteristic part of the address of the child node”. Judging. When the number of child nodes included in the child address table has reached the maximum capacity of child nodes and there is no address that can be issued to a new node, that is, when a new child node cannot be added due to the restriction of the number of child nodes orange Notifies the address updating unit 23 that a new node cannot be added as a child node. When the address updating unit 23 receives a notification from the child node adding unit 26 that a child node cannot be added, the address updating unit 23 uses the transmission / reception unit 21 to notify the network management server 110 that a new node cannot be added as a child node. Notice.

  When receiving the notification, the change condition determination unit 13 of the network management server 110 determines that the address system change condition is satisfied, and notifies the address system change unit 14 of the determination.

  On the other hand, the child node addition determination unit 26 refers to the child address table stored in the child address storage unit 25 and the address information stored in the own address storage unit 24, and when there is an address that can be issued to the new node. The address is added to the child address table, and the address update unit 23 is notified of the address. In this case, the address updating unit 23 uses the transmission / reception unit 21 to notify the new node of the issued address and notifies the network management server 110 of the node ID of the new node and the issued address. Upon receiving this notification, the transmission / reception unit 11 of the network management server 110 adds the address of the new node to the node management table of the node management table storage unit 12.

  As described above, in this modification, the address system change condition is to receive notification that a parent node candidate has refused a request for a parent node from a new node. Thus, the change condition determination unit 13 of the network management server 110 may determine that the address system change condition is satisfied based on the notification received from the node.

  In the above embodiment, when the installation density of nodes becomes high, the address system of all nodes below the corresponding repeater is uniformly changed. The present invention is not limited to this, and the address system of only a part of the cluster tree network having a high installation density of nodes may be changed. That is, in the above determination example 3 and determination example 4, it is determined whether or not the installation density exceeds the threshold value for each node. If the installation density of a certain node exceeds the threshold value, the node and the node The address system of lower nodes can be changed. Further, in the modified example of the above determination, the parent node candidate and the parent node candidate are subordinate to the parent node candidate by receiving the notification that the new node cannot be added as a child node and receiving the node ID of the new node. You can change the node address system.

  The above-described example of FIG. 11 shows an example in which the address system is partially changed in this way. In the example of FIG. 11, the node AA1 and the node AB1 have a common parent node, but the number of bits of the feature part of the address of the child node is 2 for the node AA1 and 3 for the node AB1 . This is because the installation density of the node AB1 is determined to exceed the threshold value by the determination example 3 or the determination example 4, and the node AB1 is changed as a result of the change of the node AB1 and the lower node address system, or the modification of the determination. This is a result of changing the address system of the node AB1 and lower nodes because the new node could not be added as a child node.

  Further, when only a part of the address system is changed as described above, a plurality of candidates for changing the address system may be raised. For example, in the modification of the above judgment, after a new parent node is refused to become a parent node by a parent node candidate, the other parent node candidate is requested to become a parent node, and the other parent node When a candidate is also refused to become a parent node, each parent node candidate sends a notification to the network management server 110 that a new node could not be added.

  In such a case, the address system changing unit 14 of the network management server 110 can change the address system for all the nodes that satisfy the address system changing condition and the lower-level nodes. The address system may be changed by selecting any of a plurality of nodes satisfying the above. For example, the address system may be changed by selecting a node having a low installation density among a plurality of nodes that satisfy the address system change condition.

  In the above description, an example is described in which the address system is changed when the number of nodes increases and the installation density increases. However, at the same time, when the number of nodes decreases and the installation density decreases, such a case also occurs. The address system may be changed according to a decrease in installation density. For example, it is conceivable that the number of nodes decreases when a node is removed or when a new repeater is installed and an address is updated accordingly. In these cases, for example, the address system may be changed so that the maximum allowable hop count is increased when the installation density of nodes falls below a predetermined threshold. In this case, the determinations in the above determination examples 1 to 5 can be performed as a determination as to whether or not the address system is changed so as to increase the maximum allowable hop count.

  That is, in the determination examples 1 to 4, it is determined that the address system change condition for increasing the maximum allowable hop count is satisfied when the installation density of nodes below the repeater or the installation density for each node falls below the threshold. The address system may be changed. For Judgment Example 5, when the number of child nodes immediately below the repeater falls below the threshold, it may be determined that the address system change condition for increasing the maximum allowable hop count is satisfied, and the address system may be changed. . However, from the viewpoint of avoiding frequent changes to the address system, the threshold as the address system change condition for increasing the maximum allowable hop count is the address system change condition for decreasing the maximum allowable hop count. It is desirable to make it lower than the threshold value.

  In the above embodiment, the network management server 110 sends the changed address system and the instruction for updating the address to the node 210, and the address of each node is updated at each node. The network management server 110 may perform part of the above processing and notify the node of the updated address. For example, as described above, since some nodes can update addresses by bit shift and deletion of the lowest order, regardless of the possibility of substitution, these address updates may be performed by the network management server 110. . In addition, when the network management server 110 receives a notification from the parent node candidate that a new node could not be added, the network management server 110 changes the address system of the parent node candidate and then creates a new node. Addresses may be assigned so that the parent node candidates are different.

  The present invention has an effect of increasing the number of nodes that can be connected without causing a delay in communication speed, and a plurality of nodes are connected in a tree shape with a network management server as a vertex, and the address of each node Is useful as a network management server or the like in a cluster tree network including route information to the node.

DESCRIPTION OF SYMBOLS 110 Network management server 11 Transmission / reception part 12 Node management table storage part 13 Change condition judgment part 14 Address system change part 210 Node 21 Transmission / reception part 22 Reception determination part 23 Address update part 24 Self address storage part 220 Node 25 Child address storage part 26 Child Node addition decision part

Claims (13)

A cluster tree network in which a plurality of nodes are connected in a tree shape with a network management server as a vertex, and each node address includes path information to the node,
A change condition determination unit that determines whether or not an address system change condition that will be satisfied by an increase in the number of nodes is satisfied;
When it is determined that the address system change condition is satisfied, an address system change unit that changes the address system so as to reduce the maximum allowable hop count;
An address update unit for updating the address of the node according to the changed address system;
A cluster tree network characterized by comprising:   2. The cluster tree network according to claim 1, wherein the address system change condition is that an installation density of the nodes exceeds a predetermined threshold.   3. The cluster tree according to claim 2, wherein the installation density of the nodes is the number of installed nodes per unit area in a field of a repeater that is a node directly connected to the network management server. network.   4. The installation density of the nodes is obtained by counting the number of nodes in the field of the plurality of repeaters according to a ratio shared with other repeaters. Cluster tree network as described in.   The cluster tree network according to claim 2, wherein the installation density of the nodes is obtained for each of the nodes.   The installation density of the nodes required for each node is based on the number of nodes installed per unit area in the field of the relay directly connected to the network management server and the number of connected child nodes of the node. 6. The cluster tree network according to claim 5, wherein the cluster tree network is obtained.   6. The cluster tree network according to claim 5, wherein the installation density of the nodes obtained for each node is obtained based on the number of installed nodes per unit area within the node communication radius.   2. The cluster tree network according to claim 1, wherein the address system change condition is that the number of child nodes of a relay that is a node directly connected to the network management server exceeds a threshold value.   2. The cluster tree network according to claim 1, wherein the address system change condition is that the network management server receives a notification that a new node cannot be added from the node. The address system changing unit changes the address system to increase the number of bits of a part of the address of the node,
The address update unit increases the number of bits of the part of the address of the node, bit-shifts the bits of the part of the order, and deletes the least significant bit of the address. Update the address,
The cluster tree network according to any one of claims 1 to 9, wherein the address update unit of the node having the maximum allowable hop count updates its address by changing its parent node.   The address system changing unit is configured to notify the node that the installation density of the nodes required for each node exceeds the threshold and lower nodes, or a node that has not been able to add a new node and lower 11. The cluster tree network according to claim 1, wherein the address system of the node is changed.   The address system changing unit, when there are a plurality of nodes that have notified that a new node could not be added, to change the address system of a node with a lower installation density and lower nodes among them The cluster tree network according to claim 9. A method of updating an address in a cluster tree network in which a plurality of nodes are connected in a tree shape with a network management server as a vertex, and each node address includes path information to the node,
A change condition determination step for determining whether or not an address system change condition to be satisfied by an increase in the number of nodes is satisfied;
When determining that the address system change condition is satisfied in the change condition determination step, an address system change step for changing the address system so as to reduce the maximum allowable hop count;
An address update step of updating the address of the node according to the changed address system;
An address update method comprising:

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