JP2010011084A - Communication system, communication node, and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent overload of processing of a specific communication node even if many wireless communication nodes perform packet communication via the specific communication node in a tree network. <P>SOLUTION: A route node N0 stores node addresses NA of nodes N1 and N9 which are one level lower in the hierarchy than the route node N0 as addresses of candidates for a destination through which a packet is relayed. The route node N0 receives a packet which contains a node address NA of a node N3 as a destination address. The node address NA of the node N3 contains node addresses NA of nodes N1 and N2. The route node N0 determines a destination (node N1) through which the packet will be relayed, based on the node addresses NA of the nodes N1 and N2 contained in the node address NA of the node N3 and the stored addresses (the node addresses NA of the nodes N1 and N9) of candidates for a destination through which a packet is relayed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a communication system, a communication node, and a communication method that constitute a wireless network employing a tree-structured connection form.

  In recent years, an ad hoc network, which is a wireless network autonomously configured by a plurality of wireless communication nodes having a packet relay function, has attracted attention. As a route management protocol for managing a relay route for relaying a packet in an ad hoc network, AODV (Ad hoc On-Demand Distance Vector: RFC 3561), DSR (Dynamic Source Routing: RFC 4728), and the like have been proposed.

  In such a route management protocol, each wireless communication node is assigned an address (specifically, an IP address), and each wireless communication node manages a route table in which a destination address and a relay destination address are associated with each other. The relay destination address is an address of a device to be relayed next, and is also called a next hop address. Each wireless communication node determines a wireless communication node as a relay destination (next hop) based on the route table and a destination address included in a packet to be relayed.

As one of ad hoc networks, there is a wireless network (hereinafter referred to as a tree-structured network) that employs a tree-structured connection form. For example, a plurality of wireless terminals and wireless base stations form a tree-structured network in which the wireless base stations are the highest layer nodes (hereinafter, root nodes) (see Patent Document 1). According to such a configuration, the wireless terminal can communicate with the infrastructure network via the wireless base station even if it is outside the radio wave coverage of the wireless base station.
Japanese Patent Laid-Open No. 2003-124876 (page 6-7, FIG. 7)

  By the way, in a tree structure network, a large number of wireless communication nodes may execute packet communication via a specific communication node (for example, a root node) located in a higher hierarchy. For this reason, when the conventional route management protocol such as AODV or DSR described above is applied to a tree structure network, the following problems occur.

  Specifically, in the conventional route management protocol, a route table in which a destination address and a relay destination address (next hop address) are associated with each other is used. Therefore, a specific communication node has a large number of wireless communications that constitute a tree structure network. It is necessary to manage a routing table that includes a node address as a destination address. Therefore, when the conventional route management protocol is applied to the tree structure network, there is a problem that the processing load of the specific communication node becomes excessive.

  Therefore, the present invention has been made to solve the above-described problem, and even when a large number of wireless communication nodes perform packet communication via a specific communication node in a tree structure network, the specific It is an object of the present invention to provide a communication system, a communication node, and a communication method that can prevent an excessive processing load on the communication node.

  In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that a tree-structured network (tree-structured network 10) that is a wireless network adopting a tree-structured connection form is configured, and a plurality of wireless communication nodes (node N0) having a packet relay function. N10), and the wireless communication node is connected to an upper communication node (for example, a root node N0) located in a predetermined hierarchy in the tree-structured network and a hierarchy lower than the predetermined hierarchy in the tree-structured network. A destination communication node (for example, the node N3) to which the first address is assigned and a packet relay path (relay path R1) between the specific communication node and the destination communication node in the tree-structured network. And at least one intermediate communication node (e.g., nodes N1, N2) assigned the second address The second address indicates a position of the intermediate communication node on the tree structure network, and the first address indicates the destination communication on the tree structure network. A wireless communication node which indicates a position of a node, includes the second address assigned to all the intermediate communication nodes, and the specific communication node is located in a hierarchy one level lower than the predetermined hierarchy in the tree-structured network If an address storage unit (address storage unit 103) that stores the addresses of the nodes (for example, nodes N1 and N9) as a relay destination candidate address and a packet that includes the first address as a destination address are included in the first address Based on the second address and the relay destination candidate address stored in the address storage unit. And summarized in that comprises a relay destination determining unit for determining a relay destination of the packet and (packet relay unit 104).

  According to such a communication system, when receiving a packet including the first address as the destination address, the relay destination determining unit receives the second address included in the first address and the relay destination candidate address stored in the address storage unit. Based on the above, the relay destination of the packet is determined.

  That is, by adopting an address system including the relay destination address (second address) in the destination address (first address) itself, the specific communication node can use a route table like a conventional route management protocol without using a route table. The relay destination address (second address) can be grasped from the destination address (first address). For this reason, the specific communication node can determine the relay destination (next hop) only by storing the address of the wireless communication node located in the next lower hierarchy as the relay destination candidate address.

  Therefore, according to the communication system according to the first feature of the present invention, it is not necessary to manage the routing table as in the conventional route management protocol in the specific communication node. Even when packet communication is executed via a communication node, it is possible to prevent an excessive processing load on the specific communication node.

  A second feature of the present invention relates to the first feature of the present invention, wherein the first address is assigned to the destination communication node by the intermediate communication node to which the destination communication node is connected. To do.

  A third feature of the present invention relates to the second feature of the present invention, wherein the destination communication node executes a handover for switching the intermediate communication node to be connected to another wireless communication node (for example, the node N10). The other wireless communication node allocates a new first address to the destination communication node according to the position of the other wireless communication node on the tree-structured network when the destination communication node executes the handover. The new first address includes the address of the other wireless communication node.

  A fourth feature of the present invention relates to the third feature of the present invention, wherein, when the destination communication node executes the handover, a transfer request for requesting transfer of the packet addressed to the destination communication node is issued as a handover. The transmission is transmitted to the original intermediate communication node, and the transfer request includes the new first address assigned to the destination communication node by the other wireless communication node.

  A fifth feature of the present invention relates to the third or fourth feature of the present invention, wherein when the new first address is assigned to the destination communication node by the other radio communication node, the destination communication node Transmits a new address corresponding to the position of the destination communication node on the tree-structured network to wireless communication nodes (for example, nodes N5 and N6) located in a lower hierarchy of the destination communication node in the tree-structured network. The gist is to assign.

  A sixth feature of the present invention relates to any one of the first to fifth features of the present invention, and is summarized in that the predetermined hierarchy is the highest hierarchy in the tree structure network.

  A seventh feature of the present invention is a tree-structured network (tree-structured network 10), which is a wireless network configured by a plurality of wireless communication nodes (nodes N0 to N10) having a packet relay function and adopting a tree-structured connection form. ), A communication node (for example, a root node N0) located in a predetermined hierarchy, and an address of a wireless communication node located in a hierarchy one level lower than the predetermined hierarchy in the tree-structured network is set as a relay destination candidate address. When the address storage unit (address storage unit 103) stores the packet and the packet including the first address as the destination address, the second address included in the first address and the relay destination stored by the address storage unit Based on the candidate address, a relay destination determination unit (packet for determining the relay destination of the packet) And the first address is assigned to a destination communication node (for example, a node N3) located in a hierarchy lower than the predetermined hierarchy in the tree-structure network, and on the tree-structure network And the second address is an intermediate communication node (for example, nodes N1, N2) located on a packet relay path between the communication node and the destination communication node in the tree-structured network. And indicating the position of the intermediate communication node on the tree-structured network.

  According to an eighth aspect of the present invention, there is provided a communication node located in a predetermined hierarchy in a tree-structured network, which is a wireless network composed of a plurality of wireless communication nodes having a packet relay function and adopting a tree-structured connection form. A communication method to be applied, the step of storing, as a relay destination candidate address, an address of a wireless communication node located in a hierarchy one level lower than the predetermined hierarchy in the tree structure network, and a first address as a destination address Determining a relay destination of the packet based on the second address included in the first address and the relay destination candidate address stored in the storing step when receiving the packet including the packet, The first address is in a hierarchy lower than the predetermined hierarchy in the tree-structured network. And the second address is a packet relay between the communication node and the destination communication node in the tree-structured network, and indicates the position of the destination communication node on the tree-structured network. The gist is to be assigned to an intermediate communication node located on a route and to indicate the position of the intermediate communication node on the tree-structured network.

  According to the present invention, a communication system capable of preventing an excessive processing load on a specific communication node even when a large number of wireless communication nodes perform packet communication via the specific communication node in a tree structure network. A communication node and a communication method can be provided.

  Next, a communication system according to an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) schematic configuration of communication system, (2) detailed configuration of communication system, (3) address system, (4) operation example of communication system, (5) action / effect, (6) other Embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Schematic Configuration of Communication System FIG. 1 is an overall schematic configuration diagram of a communication system 1 according to the present embodiment.

  As shown in FIG. 1, the communication system 1 includes a plurality of nodes N0 to N10. Each of the nodes N0 to N10 has a packet relay function for relaying a packet.

  The nodes N0 to N10 constitute a tree structure network 10 that is a wireless network adopting a tree structure connection form. Nodes N0 to N10 include a root node N0 and nodes N1 to N10.

  The root node N0 is connected to an external network 100 that is an infrastructure network such as a WAN (Wide Area Network) or a LAN (Local Area Network). The root node N0 is, for example, a radio base station or gateway that is connected to the external network 100 by wire.

  In the present embodiment, the root node N0 constitutes a communication area that is an area where wireless communication is possible. In the example of FIG. 1, the nodes N1 and N9 are located in the communication area and are connected to the root node N0.

  The nodes N1 to N10 are portable wireless terminals such as mobile phone terminals or notebook PCs or PDAs having a wireless communication function. The nodes N1 to N10 execute wireless communication according to, for example, a wireless LAN (such as IEEE 802.11), Bluetooth (registered trademark), or iBurst (registered trademark).

  Each of the nodes N1 to N10 has a function of performing wireless communication with the root node N0 and a function of relaying communication between the root node N0 and other nodes. That is, each of the nodes N1 to N10 can perform wireless communication (single hop communication) with the root node N0 or indirect communication (multihop communication) with the root node N0 via at least one other node.

  The tree-structure network 10 has a tree structure with the root node N0 as the highest hierarchy. In the tree-structured network 10, the node N1 and the node N9 are located in the first hierarchy that is one hierarchy below the highest hierarchy.

  In addition, the node N2 and the node N10 are located in the second hierarchy that is one hierarchy lower than the first hierarchy. The node N3 and the node N4 are located in the third hierarchy that is one hierarchy lower than the second hierarchy. The node N5 and the node N6 are located in the fourth layer that is one layer below the third layer. The node N7 and the node N8 are located in the fifth hierarchy that is one hierarchy lower than the fourth hierarchy.

  In the following, a node connected to the node in the hierarchy one level higher than the hierarchy where a certain node is located is appropriately referred to as a “parent node”. In addition, a node connected to the node in a hierarchy one level lower than a hierarchy where a certain node is located is appropriately referred to as a “child node”.

  For example, the node N2 is a parent node of the node N3 and the node N4, and is a child node of the node N1. The node N3 is a parent node of the node N5 and the node N6, and is a child node of the node N2. Note that a node group connected to the node directly or via another node in a hierarchy lower than a hierarchy where a certain node is located is appropriately referred to as a “subordinate node”.

  A unique node address NA in the tree-structured network 10 is assigned to each of the nodes N1 to N10. The node address NA is used for packet communication, and a packet relay route is determined based on the node address NA. The node address NA indicates the position of each of the nodes N1 to N10 on the tree structure network 10. The node address NA is assigned from the parent node to the child node. The parent node manages the node address NA assigned to the child node.

  The node address NA is not a fixed 4-byte address system as in the conventional IP address, but an address system in which a lower node can be identified by a unique number assigned to each hierarchy and assigned to each parent node. .

  In this embodiment, the node address NA is not assigned to the root node N0. The address of the external network 100 connected to the root node N0 is assigned to the root node N0.

  A node newly joining the tree-structured network 10 sends a connection request to a parent node having the best wireless condition from several candidates, and when the connection is permitted for the connection request, the node address NA is given. Is done.

  The node address NA also serves as path information from the root node N0 to the newly connected node, and the newly connected node uses another node or root node in the tree-structured network 10 using the acquired node address NA. Packet communication with the external network 100 to which N0 belongs is started.

  Only the parent node needs to know the node address NA of the newly connected node, and it does not need to know the root node N0 or the node on the route to the root node N0. Such an address management technique particularly reduces the processing load on the root node N0.

  Hereinafter, an address management method capable of reducing the processing load of the root node N0 will be described in detail. Since the nodes N1 to N10 are configured in the same manner, in the following embodiments, the node N3 is mainly described as a node representing the nodes N1 to N10.

  The node N3 receives a packet addressed to the node N3 from the external network 100 from the root node N0 via the nodes N1 and N2. In the present embodiment, the root node N0 is a communication node located in a predetermined hierarchy (the highest hierarchy) in the tree structure network 10.

  In the present embodiment, the node N3 is located in a hierarchy lower than a predetermined hierarchy in the tree-structure network 10, and constitutes a destination communication node to which a first address is assigned.

  The nodes N1 and N2 are located on the relay route R1 between the specific communication node and the destination communication node in the tree structure network 10, and constitute at least one intermediate communication node to which the second address is assigned.

(2) Detailed Configuration of Communication System Next, details of the communication system 1 will be described in the order of (2.1) configuration of the root node and (2.2) configuration of the node.

(2.1) Configuration of Root Node FIG. 2 is a block diagram showing the configuration of the root node N0. As illustrated in FIG. 2, the root node N0 includes a transmission / reception unit 101, an address management unit 102, an address storage unit 103, and a packet relay unit 104.

  The transmission / reception unit 101 transmits / receives packets to / from the external network 100 and the nodes N1 and N9. In the present embodiment, the transmission / reception unit 101 has a function of performing wired communication with the external network 100 and a function of performing wireless communication with the nodes N1 and N9.

  The address management unit 102 manages the address table stored in the address storage unit 103. Here, the address table is not a configuration in which a destination address and a relay destination address are associated with each other as in the conventional route table, but a configuration in which the node address NA of a child node is only stored as a relay destination candidate address.

  The address storage unit 103 stores the node addresses NA of the nodes N1 and N9 located in the hierarchy one level lower than the root node N0. The address management unit 102 assigns a unique node address NA to a node that requests connection to the root node N0, and stores the assigned node address NA in the address storage unit 103.

  When the transmission / reception unit 101 receives a packet to be relayed to any one of the nodes N1 to N10, the packet relay unit 104 and the destination address (node address NA) included in the packet and the relay destination stored in the address storage unit 103 Based on the candidate address, a relay destination node (next hop) of the packet is determined, and the packet is relayed to the determined relay destination node. That is, the packet relay unit 104 functions as a relay destination determination unit that determines a packet relay destination.

(2.2) Node Configuration FIG. 3 is a block diagram showing the configuration of the node N3. As described above, since all the nodes N1 to N10 have the same configuration, the node N3 will be described here.

  As illustrated in FIG. 3, the node N3 includes a transmission / reception unit 201, an address management unit 202, an address storage unit 203, a packet relay unit 204, and a connection control unit 205.

  The transmission / reception unit 201 transmits / receives packets to / from the parent node and the child node. In the present embodiment, the transmission / reception unit 201 has a function of performing wireless communication with the node N2, the node N5, and the node N6.

  The address management unit 202 manages the address table stored in the address storage unit 203. In the address table in the node N3, unlike the address table in the root node N0, the node address NA of the node N3 itself is also stored. The address storage unit 203 stores the node address NA of the child node (nodes N5 and N6) as a relay destination candidate address.

  When the transmission / reception unit 201 receives a packet to be relayed to any of the subordinate nodes, the packet relay unit 204 receives the destination address (node address NA) included in the packet and the relay destination candidate stored in the address storage unit 203 Based on the address, a relay destination node (next hop) of the packet is determined, and the packet is relayed to the determined relay destination node.

  The connection control unit 205 determines the connection destination of the node N3 and connects to the determined connection destination. For example, the connection control unit 205 receives a beacon signal periodically notified by each of the nodes N0 to N10, and determines a node having the highest reception quality of the beacon signal as a connection destination. In addition, the connection control unit 205 controls handover for switching a connection destination from a certain node to another node. The address management unit 202 updates the address table in accordance with the initial connection operation or the handover operation by the connection control unit 205.

(3) Address System Next, an address system used in the communication system 1 will be described. Here, the configuration of the node address NA “1.1.2” assigned to the node N3 will be described.

  The node address NA has a function as an identifier (ID) for uniquely identifying a node, a function as position information indicating a position on the tree structure network 10, and a function as path information indicating a packet relay path. . Specifically, as shown in FIG. 4, the node address NA “1.1.2” includes the node addresses NA of the nodes N1 and N2 located on the relay route R1 between the root node N0 and the node N3. Is included.

  Specifically, in the node address NA “1.1.2”, the value “1” on the left side is the node address NA of the node N1, and the value “1.1” on the left side and the center is the node address of the node N2. Address NA. That is, from the node address NA “1.1.2”, the node address NA of the parent node of the node N3 is “1.1”, and the node address NA of the parent node of the parent node is “1”. The address system can be specified.

  Therefore, when receiving a packet including the node address NA “1.1.2” as the destination address, the root node N0 can immediately determine that the relay destination node address NA is “1”. In this case, the root node N0 determines the child node (node N1) having the node address NA “1” as the relay destination of the packet.

(4) Operation Example of Communication System Next, an operation example of the communication system 1 will be described in the order of (4.1) overall schematic operation, (4.2) operation sequence, and (4.3) table changing operation.

(4.1) Overall Schematic Operation In this operation example, as shown in FIG. 5, when a node N3 holding several child nodes (nodes N5 and N6) is handed over to another node N10 due to a change in the radio environment. Will be described.

  Specifically, the node N3 determines that the radio quality between the node N3 and the node N2 is deteriorated and the radio quality between the node N3 and the node N10 is good, and performs handover to the node N10. In FIG. 5, the node N3 transmits a connection request to the node N10, and when the node N10 permits the connection request, a node address NA of “2.1.1” is assigned to the node N3.

  The node under the node N3 needs to change the node address NA used by the own node as the node address NA of the parent node changes. Therefore, after the handover, the node N3 notifies the child nodes (node N5 and node N6) of the change of the node address NA. The child nodes (node N5 and node N6) further notify the child nodes (node N7 and node N8).

  In addition, the node N3 transmits a transfer request to the parent node N2 before the handover so that the packet communicated before the handover is transferred to the new node address NA. Thereby, the continuity of communication is maintained. In the example of FIG. 5, the transfer request is relayed from the handover destination node N10 to the node N2 via the route node N0.

  The node N9 and the root node N0 do not need to know that the node N3 has joined the node N10, and communication is possible if only the node N3 and the node N10 are negotiated. Further, the node N10, the node N9, and the root node N0 do not need to know the node group under the node N3.

(4.2) Operation Sequence FIG. 6 is a sequence diagram illustrating a detailed operation example of the communication system 1.

  In step S11, the node N3 is connected to the node N2. When the node N3 connects to the node N2, the node N2 assigns the node address NA “1.1.2” including its own node address NA “1.1” to the node N3 (step S12).

  Further, it is assumed that the subordinate nodes (nodes N5 to N8) are connected to the node N3 after the node N3 is connected to the node N2. Then, the node N3 assigns the node address NA “1.1.2.1” including its own node address NA “1.1.2” to the node N6 (step S14). The node N3 assigns the node address NA “1.1.2.2” including its own node address NA “1.1.2” to the node N5 (step S13).

  In step S15, the node N3 determines that the condition of the node N10 is better than that of the node N2, and starts a handover procedure for switching the parent node from the node N2 to the node N10. When the handover procedure is started, the node N3 transmits a connection request to the node N10 (step S16). The node N10 transmits a connection permission indicating that the connection request from the node N3 has been permitted to the node N3 (step S17).

  In step S18, the node N3 transmits to the node N2 a disconnection request for disconnecting the connection with the node N2. In response to the disconnection request from the node N3, the node N2 disconnects the connection with the node N3 (step S19).

  In step S20, the node N3 transmits an address assignment request for requesting assignment of a new node address NA to the node N10. In response to the address assignment request from the node N3, the node N10 assigns a new node address NA “2.1.1” including its own node address NA “2.1” to the node N3 (step S21). Then, the node N3 changes its own node address NA “1.1.2” to a new node address NA “2.1.1” (step S22).

  In step S23, the node N3 transmits a transfer request for requesting transfer of a packet addressed to the node N3 to the handover source node N2. Here, the transfer request includes the node address NA “1.1” of the node N2 as the destination address, and the new node address NA “2.1.1” of the node N3 as the transfer destination address. In the example of FIG. 5, the transfer request arrives at the root node N0 from the node N3 via the node N10 and the node N9, and is then relayed to the node N2 according to the destination address “1.1”. When the node N2 receives the transfer request, the node N2 stores the new node address NA “2.1.1. After the storage, the node N2 stores the original node address NA“ 1.1.2. x. x. . . The packet addressed to "" is transferred to the new node address NA "2.1.1" (step S24).

  In step S25 and step S27, the node N3 also has a new node for the child nodes (nodes N5 and N6) in response to the change of the own node address NA to the new node address NA “2.1.1”. Assign an address NA.

  Specifically, in step S25, the node N3 assigns a new node address NA “2.1.1.2” including the new node address NA “2.1.1” to the node N5, and notifies that. Notify node N5. When the node N5 is notified of the new node address NA “2.1.1.2”, the node N5 uses its own node address NA “1.1.2.2” and the new node address NA “2.1.1”. .2 "(step S26). Then, in response to the change of the own node address NA to the new node address NA “2.1.1.2”, the node N5 also sends a new node address NA to the node N8 that is a child node of the node N5. Is assigned (step S28).

  In step S27, the node N3 assigns a new node address NA “2.1.1.1” to the node N6 and notifies the node N6 to that effect. When the new node address NA “2.1.1.1” is notified, the node N6 assigns its own node address NA “1.1.2.1” to the new node address NA “2.1.1”. .1 "(step S29). Then, in response to the change of the own node address NA to the new node address NA “2.1.1.1”, the node N6 also sends a new node address NA to the node N7 that is a child node of the node N6. Is assigned (step S30).

(4.3) Table Change Operation FIG. 7 is a diagram showing how the address table held by each node changes before and after the handover of the node N3.

  As shown in FIG. 7A, the node N2 has its own node address NA “1.1” and its child node address NA “1.1.2 (node N3)” and “1.1” before handover. .1 (node N4) ". After the handover, the node N2 deletes the corresponding child node address NA “1.1.2 (node N3)” because the node N3 is no longer a child node.

  As shown in FIG. 7B, the node N3 has its own node address NA “1.1.2”, the child node address NA “1.1.2.2 (node N5)”, and It is stored that “1.1.2.1 (node N6)”. After the handover, since the parent node becomes the node N10, the node N3 has its own node address NA “2.1.1”, the child node address NA “2.1.1.2 (node N5)”, and Change to “2.1.1.1 (node N6)”.

  As shown in FIG. 7C, the node N10 stores that its own node address NA is “2.1” before the handover. Since the node N3 becomes a child node after the handover, the node N10 adds the child node address NA “2.1.1 (node N3)”.

  As shown in FIG. 7D, the node N5 has its own node address NA “1.1.1.2” and its child node address NA “1.1.2.2.1 (node) before the handover. N8) ". After the handover, the node N5 changes its child node address NA to “2.2.1.2.1 (node N8)” because its own node address NA becomes “2.1.1.2”. .

  As shown in FIG. 7E, the node N6 has its own node address NA “1.1.2.1” and its child node address NA “1.1.2.1.1 (node) before the handover. N7) ". After the handover, the node N6 changes its child node address NA to “2.1.1.1.1 (node N7)” because its own node address NA becomes “2.1.1.1”. .

  As shown in FIG. 7F, the node N7 stores that its own node address NA is “1.1.2.1.1” before the handover. After the handover, the node N7 has its own node address NA “2.1.1.1.1”.

  As shown in FIG. 7G, the node N8 stores that its own node address NA is “1.1.2.2.1” before the handover. After the handover, the node N7 has its own node address NA “2.2.1.2.1”.

(5) Operation and Effect As described above, the node address NA of the node N3 includes the node addresses NA of the nodes N1 and N2. The address storage unit 103 of the root node N0 stores the node addresses NA of the nodes N1 and N9 located in the next lower hierarchy as relay destination candidate addresses.

  When the packet relay unit 104 of the root node N0 receives a packet including the node address NA of the node N3 as a destination address, the node relay NA of the nodes N1 and N2 included in the node address NA of the node N3 and the address storage Based on the relay destination candidate address (node addresses NA of the nodes N1 and N9) stored in the unit 103, the relay destination of the packet is determined to be the node N1. Then, the packet relay unit 104 relays the packet to the determined node N1.

  That is, by adopting an address system in which the destination address (the node address NA of the node N3) itself includes the relay destination address (the node addresses NA of the nodes N1 and N2), the root node N0 can be configured like a conventional route management protocol. The relay destination address (node addresses NA of the nodes N1 and N2) can be determined from the destination address (node address NA of the node N3) without using the routing table. Therefore, the root node N0 can determine the relay destination (next hop) only by storing the node addresses NA of the nodes (child nodes) N1 and N9 located in the next lower hierarchy as the relay destination candidate addresses.

  Therefore, according to the present embodiment, it is not necessary to manage the route table as in the conventional route management protocol at the root node N0, and therefore, a large number of nodes N0 to N10 pass through the root node N0 in the tree structure network 10. Even when packet communication is executed, it is possible to prevent the processing load on the root node N0 from becoming excessive.

  In this embodiment, the node address NA of the node N3 is assigned to the node N3 by the node N2 to which the node N3 is connected. For this reason, the processing load of the root node N0 can be reduced as compared with the case where the root node N0 assigns the node address NA of the node N3.

  In the present embodiment, the node N3 performs a handover for switching the connection destination to the node N10. When the handover is executed, the node N10 assigns a new node address NA including the node address NA of the node N10 to the node N3. Therefore, even when the node N3 is handed over, the address system according to the present embodiment (that is, an address system that can reduce the processing load of the root node N0) can be maintained.

  In the present embodiment, when executing a handover to the node N10, the node N3 transmits a transfer request for requesting transfer of a packet addressed to the node N3 to the handover source node N2. The transfer request includes the node address NA of the new node N3 assigned by the node N10 to the destination communication node. Therefore, the node N2 that is the handover source can transfer the packet addressed to the node N3 to the node address NA of the new node N3. For this reason, even when the node N3 is handed over, occurrence of packet loss can be avoided.

  In the present embodiment, when a new node address NA is assigned to the node N3 by the node N10, the node N3 assigns a new node address NA corresponding to the position of the node N3 on the tree structure network 10 to the tree structure network 10. Are assigned to nodes N5 and N6 located in the lower hierarchy of the destination communication node. That is, node addresses NA including the node address NA of the new node N3 are assigned to the nodes N5 and N6.

  Therefore, when the node N3 having a child node performs a handover, the address system according to the present embodiment (that is, an address system that can reduce the processing load of the root node N0) can be maintained for the child node. it can.

(6) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the embodiment described above, the root node N0 is described as a wireless base station or gateway connected to the external network 100 by wire, but the root node N0 may be a wireless terminal wirelessly connected to the external network 100. In the embodiment described above, all of the nodes N0 to N10 have been described as portable wireless terminals. However, a part of the nodes N0 to N10 may include a fixed wireless terminal.

  In the above-described embodiment, the description has been mainly made of reducing the processing load of the root node N0. However, not only the root node N0 but also the processing loads of other upper nodes (for example, the nodes N1 and N9) are reduced. Of course. That is, in the above-described embodiment, since the route table as in the conventional route management protocol is not used, the overall processing load of the tree structure network 10 can be reduced.

  In the above-described embodiment, the description has been made on the assumption that the above-described address system is applied to the external network 100, but an address system (for example, an IP address) different from the above-described address system is applied to the external network 100. In this case, the root node N0 may have an address translation function such as NAT.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

1 is an overall schematic configuration diagram of a communication system according to an embodiment of the present invention. It is a block diagram which shows the structure of the root node which concerns on embodiment of this invention. It is a block diagram which shows the structure of the node which concerns on embodiment of this invention. It is a figure for demonstrating the address system used in the communication system which concerns on embodiment of this invention. It is a figure for demonstrating the whole schematic operation | movement of the communication system which concerns on embodiment of this invention. It is a sequence diagram which shows the detailed operation example of the communication system which concerns on embodiment of this invention. It is a figure which shows a mode that the address table which each node hold | maintains before and after the handover of the node which concerns on embodiment of this invention.

Explanation of symbols

  N0: root node, N1-N10 ... node, 1 ... communication system, 10 ... tree network, 100 ... external network, 101 ... transmission / reception unit, 102 ... address management unit, 103 ... address storage unit, 104 ... packet relay unit, 201 ... transmission / reception unit, 202 ... address management unit, 203 ... address storage unit, 204 ... packet relay unit, 205 ... connection control unit

Claims (8)

A tree-structured network that is a wireless network adopting a tree-structured connection form is configured, and includes a plurality of wireless communication nodes having a packet relay function,
The wireless communication node is
A specific communication node located in a predetermined hierarchy in the tree structure network;
A destination communication node located in a hierarchy lower than the predetermined hierarchy in the tree-structured network and assigned a first address;
A communication system including at least one intermediate communication node located on a packet relay path between the specific communication node and the destination communication node in the tree-structured network and assigned a second address;
The second address indicates a position of the intermediate communication node on the tree-structured network;
The first address indicates a position of the destination communication node on the tree-structured network, and includes the second address assigned to all the intermediate communication nodes;
The specific communication node is:
An address storage unit that stores, as a relay destination candidate address, an address of a wireless communication node located in a hierarchy one level lower than the predetermined hierarchy in the tree-structured network;
When a packet including the first address as a destination address is received, the relay destination of the packet is based on the second address included in the first address and the relay destination candidate address stored in the address storage unit A communication system comprising: a relay destination determining unit that determines   The communication system according to claim 1, wherein the first address is assigned to the destination communication node by the intermediate communication node to which the destination communication node is connected. The destination communication node performs a handover to switch the intermediate communication node of the connection destination to another wireless communication node;
The other wireless communication node assigns a new first address to the destination communication node according to the position of the other wireless communication node on the tree-structured network when the destination communication node executes the handover,
The communication system according to claim 2, wherein the new first address includes an address of the other wireless communication node. When the destination communication node executes the handover, the destination communication node transmits a transfer request for requesting transfer of the packet addressed to the destination communication node to the intermediate communication node of the handover source,
The communication system according to claim 3, wherein the transfer request includes the new first address assigned to the destination communication node by the other wireless communication node.   When the new first address is assigned to the destination communication node by the other wireless communication node, the destination communication node assigns a new address according to the position of the destination communication node on the tree-structured network, The communication system according to claim 3 or 4, wherein the communication system is assigned to a wireless communication node located in a lower hierarchy of the destination communication node in the tree structure network.   The communication system according to claim 1, wherein the predetermined hierarchy is a highest hierarchy in the tree-structured network. A tree-structured network, which is a wireless network configured by a plurality of wireless communication nodes having a packet relay function and adopting a tree-structured connection form, is a communication node located in a predetermined hierarchy,
An address storage unit that stores, as a relay destination candidate address, an address of a wireless communication node located in a hierarchy one level lower than the predetermined hierarchy in the tree-structured network;
When a packet including the first address as a destination address is received, the relay destination of the packet is determined based on the second address included in the first address and the relay destination candidate address stored in the address storage unit A relay destination determination unit that
The first address is assigned to a destination communication node located in a hierarchy lower than the predetermined hierarchy in the tree structure network, and indicates a position of the destination communication node on the tree structure network,
The second address is assigned to an intermediate communication node located on a packet relay path between the communication node and the destination communication node in the tree structure network, and the position of the intermediate communication node on the tree structure network Communication node indicating In a tree-structure network, which is a wireless network configured by a plurality of wireless communication nodes having a packet relay function and adopting a tree-structured connection form, a communication method applied to a communication node located in a predetermined hierarchy,
Storing, as a relay destination candidate address, an address of a wireless communication node located in a hierarchy one level lower than the predetermined hierarchy in the tree-structured network;
When a packet including the first address as a destination address is received, the relay destination of the packet is determined based on the second address included in the first address and the relay destination candidate address stored in the storing step And a step of
The first address is assigned to a destination communication node located in a hierarchy lower than the predetermined hierarchy in the tree structure network, and indicates a position of the destination communication node on the tree structure network,
The second address is assigned to an intermediate communication node located on a packet relay path between the communication node and the destination communication node in the tree structure network, and the position of the intermediate communication node on the tree structure network Indicates the communication method.

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