JP2008042647A - Node constituting ad hoc/network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain nodes constituting an ad hoc/network that are capable of reducing the amount of information. <P>SOLUTION: A node 101-s, when there are existent adjacent nodes exceeding a manageable number, once receiving hello message including adjacent node information from a node 101-a, if link quality La of the foregoing hello message is smaller than or equal to the minimum link quality Lmin in an adjacent node assembly, discards the hello message from the node 101-a. Further, the node 101-s, once receives a broadcast message involving adjacent node information from a node 101-b, and if link quality Lb of the foregoing hello message is greater than the minimum link quality Lmin, then it deletes a node having the minimum link quality Lmin from the adjacent node assembly and registers the node 101-b to the adjacent node assembly. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is an ad hoc network (or multi-hop network) system that performs communication by using an arbitrary node as a relay node when a plurality of nodes autonomously form a network and cannot communicate directly between the nodes. In order to broadcast a message to a node in the network, it is efficient to obtain a node that retransmits the minimum necessary broadcast message from the information held by the nodes located around the local node. The present invention relates to a node constituting an ad hoc network for transferring a broadcast message.

  With the progress of wireless communication technology and the downsizing and sophistication of electronic devices in recent years, communication between communication devices can be performed without using existing network infrastructure, compared to the conventional infrastructure type communication form. There is a growing interest in ad hoc networks. This ad hoc network is different from the conventional fixed infrastructure type network. (1) Communication between objects and devices, (2) Autonomous network construction with huge objects and devices, (3) Existing Network construction that does not depend on the communication infrastructure, and (3) easy and temporary construction of the network, and can autonomously respond to changes in topology. Currently, many routing protocols (ad hoc routing protocols) for forming an ad hoc network have been proposed to satisfy the above characteristics. For example, there are DSR (Dynamic Source Routing) (draft-ietf-manet-dsr-10.txt), AODV (Ad Hoc On Demand Distance Vector Routing) (RFC3561), OLSR (Optimized RF Link) R26.

  DSR and AODV are on-demand type routing protocols, and when a communication request is made, a route from a transmission source to a transmission destination is obtained and communication is performed. OLSR, on the other hand, is a proactive routing protocol that manages topology information by constantly exchanging route information and can start communication based on route information held when a communication request occurs. It has become.

  In recent years, there has been a growing interest in wireless sensor networks that can be constructed at low cost. This wireless sensor network is a network of sensor nodes with sensing, computing, and wireless communication functions. It is an ad hoc network composed of nodes that are arbitrarily placed in areas that require monitoring. is there. Note that sensor nodes constituting a wireless sensor network generally have restrictions on CPU processing capacity, memory resources, battery capacity, and the like, and it is necessary to consider various restrictions.

  In DSR and AODV, a route search request message is broadcast to the destination node in order to obtain a route from the source node to the destination node when a communication request occurs. Each node that receives this broadcast message, when the node is not the destination node included in the corresponding message, based on the sequence number and the source address and destination address of the received broadcast message, It is determined whether the broadcast message has already been received, and all the receiving nodes retransmit the first received broadcast message. In other words, since all the receiving nodes perform re-forwarding, when the number of nodes increases or when nodes exist densely, many redundant broadcast messages are transferred in the network, and the radio band is wasted. was there.

  In order to deal with the above problem, means for realizing efficient broadcast message transfer in the network called a probabilistic method (Probability Based Methods) or a range type method (Area Based Methods) has been proposed (for example, Patent Document 1). However, the probabilistic method is a means of retransmitting the broadcast message that is received stochastically for the first broadcast message received by each node, enabling the transmission of the broadcast message to all nodes in the network. In order to do so, means such as setting the probability value for retransmitting the received broadcast message to an optimum value according to the number of nodes located in the vicinity is required, and depending on how the probability value is set, However, there is a problem in that the probability (reach rate) that the broadcast message is transferred to all the nodes in the network is reduced.

  In the range type method, the wireless communication range newly increased is evaluated by retransmitting the broadcast message according to the positional relationship with the adjacent node, and the received broadcast message is retransmitted. Here, when evaluating a newly increased wireless communication range, it is necessary to assume that the wireless characteristics of each node are the same, resulting in a decrease in the arrival rate due to a mismatch with the actual environment where various nodes exist. There was a problem.

S. Ni, Y. Tseng, Y.M. Chen, and J.M. Sheu, “The broadcast storm program in a mobile ad hoc network,” In Proceedings of the ACM / IEEE International Conference on Mobile Comp. 151-162, 1999

  In OLSR, adjacent node information obtained by exchanging broadcast messages for adjacent nodes called Hello messages as MPR (Multi-Point Relaying) between adjacent nodes, that is, adjacent nodes and 2-hop adjacent Means for realizing efficient broadcast message transfer by obtaining an MPR set, which is a set of nodes that retransmit a broadcast message transferred by the own node, from a node (a node reachable via an adjacent node) Is stipulated. However, in the calculation for obtaining the MPR set, information on adjacent nodes and 2-hop adjacent nodes (information on adjacent nodes) is required, and particularly in a network where nodes are densely present, a large amount of memory is required. There was a problem of becoming.

  In addition, when a hello message is received from an adjacent node that is not managed by the own node, the entry of a new node is detected and the MPR set is recalculated, so that there is not enough memory capacity and the node is located adjacent to the own node. When all nodes cannot be managed, new nodes are frequently detected by receiving hello messages, and the CPU processing load increases due to recalculation of the MPR set, and radio bandwidth is wasted due to re-notification of the MPR set. There was a problem.

  Furthermore, in general, not all nodes have the same radio propagation characteristics, and there may be nodes with a small radio propagation range. In a node with a small radio propagation range, adjacent nodes have a memory amount, etc. When information on all adjacent nodes cannot be retained due to restrictions, a bidirectional link cannot be established with the adjacent node, and information on a sufficient number of adjacent nodes may not be secured. .

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to perform periodicity in an ad hoc network (or multi-hop network) system in which a plurality of nodes autonomously constitute a network. Based on the information of neighboring nodes notified to the node, information on neighboring nodes located around the local node and 2-hop neighboring nodes is retained, and a set of neighboring nodes to which the broadcast message is retransmitted is determined based on the retained information. In this case, a node constituting an ad hoc network that can reduce the amount of information necessary for calculation is obtained.

  The present invention has been made to solve the above-described problems, and its purpose is to manage the own node when there are adjacent nodes exceeding the number of nodes that can be managed by the own node. It is possible to obtain a node constituting an ad hoc network capable of reducing the frequency of various processes by detecting a new node by receiving a broadcast message from a node that does not exist.

  Furthermore, the present invention has been made to solve the above-described problems, and its purpose is sufficient even in a node having a small radio propagation range when there is a large difference in radio propagation characteristics between nodes. A node constituting an ad hoc network capable of establishing a bidirectional link with any number of adjacent nodes is obtained.

  The nodes constituting the ad hoc network according to the present invention include a set of adjacent nodes located next to the own node, a set of 2-hop adjacent nodes that can be reached via the adjacent nodes, and all adjacent nodes that are two hops away. A memory means for holding a minimum necessary set of adjacent nodes to which a broadcast message can be transferred, the set of adjacent nodes based on the broadcast message for adjacent nodes including information on the received adjacent nodes, and the 2 A management means for creating a set of adjacent hop nodes in the memory means, creating a set of adjacent nodes in the memory means based on the set of adjacent nodes and the set of 2-hop adjacent nodes, and notifying from the adjacent nodes Re-transmission means for re-transmitting the broadcast message based on the set of the adjacent nodes, and includes information on the adjacent nodes of the own node A node constituting an ad hoc network that periodically transmits a broadcast message for a contact node, wherein the management means includes a number of adjacent nodes exceeding a predetermined manageable number of nodes. When the broadcast message for the adjacent node including the information on the adjacent node is received from the adjacent first node in the existing state, the minimum link quality in the set of adjacent nodes and the adjacent node from the first node are received. If the link quality of the broadcast message from the first node is less than or equal to the minimum link quality, the adjacent node from the first node When the broadcast message is discarded and the number of adjacent nodes exceeds the predetermined number of nodes that can be managed in the set of the adjacent nodes. When a broadcast message for adjacent nodes including information on adjacent nodes is received from an adjacent second node, the minimum link quality in the set of adjacent nodes and the link of broadcast messages for adjacent nodes from the second node If the link quality of the broadcast message from the second node is greater than the minimum link quality, the third node having the minimum link quality from the set of adjacent nodes. And register the second node in the set of adjacent nodes.

  The nodes constituting the ad hoc network according to the present invention hold and hold information on neighboring nodes and neighboring two-hop nodes located in the vicinity of the own node based on periodically notified neighboring node information. In addition, there is an effect that it is possible to reduce the amount of information necessary for calculation when determining a set of adjacent nodes to which the broadcast message is retransmitted.

Embodiment 1 FIG.
The nodes constituting the ad hoc network according to the first embodiment of the present invention will be described with reference to FIGS. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

  FIG. 1 is a diagram showing a system configuration of an ad hoc network according to Embodiment 1 of the present invention. In FIG. 1, an ad hoc network 100 has a plurality of nodes (Δ marks) 101 connected by wireless links to autonomously configure a network. Each node 101 is provided with transmission / reception means for transmitting / receiving hello messages, management means for managing information on adjacent nodes, memory means for storing information on adjacent nodes, retransmission means for retransmitting broadcast messages, antennas, etc. It has been.

  The node 101 constituting the ad hoc network 100 periodically advertises the identifier of the adjacent node of the own node by the hello message as the local link information of the own node. Also, by receiving a hello message from an adjacent node, information on adjacent nodes (adjacent node set AA, 2-hop adjacent node set BB, adjacent node set CC) is managed by the management means.

  First, in the node 101 constituting the ad hoc network 100, a management unit that manages information on neighboring nodes, and a basic unit for a retransmission unit that efficiently retransmits a broadcast message in the network based on a set CC of neighboring nodes. A typical operation will be described.

  FIG. 2 is a diagram showing a transfer example of the broadcast message of the nodes constituting the ad hoc network according to the first embodiment of the present invention.

  In FIG. 2, the node 101-s periodically transmits a broadcast message called a hello message including the identifier of the adjacent node as local link information of the own node by the transmission / reception means. Also, by receiving the hello message from the adjacent node, the local link information of the own node is updated, and the management unit can reach 2 via the set AA of adjacent nodes adjacent to the own node and the adjacent node. A set BB of hop adjacent nodes is created in the memory means. Then, the minimum necessary set of adjacent nodes CC that can transfer a hello message to all adjacent nodes that are two hops ahead based on the set AA of adjacent nodes and the set BB of 2-hop adjacent nodes by the management means. (MPR set) is created in the memory means. By notifying this adjacent node set CC to the adjacent node by a hello message, only the adjacent node included in the adjacent node set CC retransmits the broadcast message transferred from the node 101-s by the retransfer means. .

  FIG. 3 is a diagram showing a system configuration in which a part of the ad hoc network of FIG. 1 is extracted. FIG. 4 is a diagram showing a configuration of a set of adjacent nodes and a set of 2-hop adjacent nodes of nodes constituting the ad hoc network of FIG.

  In FIG. 3, when the node 101-s receives the hello message from the adjacent nodes 101-a, 101-b, 101-c, and 101-d, the management unit sets the adjacent node set AA {101-a. , 101-b, 101-c, 101-d} and a set BB {101-e, 101-f, 101-g, 101-h, 101-i} of 2-hop neighboring nodes are created in the memory means. Then, the management unit obtains a set CC {101-a, 101-c} of the adjacent node from the set AA of adjacent nodes and the set BB of 2-hop adjacent nodes, and determines the set CC of the adjacent nodes by the hello message as the adjacent node. 101-a, 101-b, 101-c, and 101-d are notified.

  Here, as shown in FIG. 4, the management means of the node 101-s calculates the set CC (MPR set) of adjacent nodes, as shown in FIG. 4, adjacent nodes 101-a, 101-b, 101-c, 101-d. It is also necessary to manage a list of adjacent nodes, which is information of adjacent nodes possessed by each adjacent node, which is local link information.

  As shown in FIG. 4A, in the example of FIG. 3, the adjacent nodes 101-a, 101-b, 101-c, 101- are arranged for each adjacent node constituting the set AA of adjacent nodes of the node 101-s. For each d, “node identifier”, “status” such as one-way communication enabled and two-way communication enabled, “priority”, “other”, and “adjacent node information” are stored. The Further, the “node identifier” of the adjacent node is stored in the “adjacent node information”. The “other” column stores the calculated link quality of the adjacent node as will be described later.

  As shown in FIG. 4B, for each adjacent node that constitutes the set BB of 2-hop adjacent nodes of the node 101-s, in the example of FIG. 3, adjacent nodes 101-e, 101-f, 101-g, For each of 101-h and 101-i, “node identifier”, “lifetime”, “other”, and “information on adjacent node” are stored. Also, “information on adjacent node” stores “node identifier” of an adjacent node that can reach the adjacent node.

  Next, management means for efficiently managing information of adjacent nodes in the nodes constituting the ad hoc network according to Embodiment 1 of the present invention will be described. FIG. 5 is a flowchart showing the operation of the management means of the nodes constituting the ad hoc network according to Embodiment 1 of the present invention.

  For example, when there is a margin in the number of nodes that can be managed in the preset set AA of adjacent nodes, and there is an adjacent node or a 2-hop adjacent node, the management unit of the node 101-s sends a Hello message from the adjacent node. Is received, the link quality, which is a value called LQI (Link Quality Indication) or RSSI (Received Signal Strength Indicator), is calculated and stored in the “other” column of the set AA of adjacent nodes of the adjacent node. The maximum number of adjacent nodes that can be managed is maintained by sequentially registering the adjacent nodes whose link quality is within the specified range in the adjacent node set AA in descending order of link quality.

  Also, the management means of the node 101-s calculates the link quality for the received hello message when the number of manageable nodes exceeds the number of adjacent nodes, and this link quality is held in the adjacent node set AA. If the link quality of the adjacent node is smaller than or equal to the minimum link quality, the received hello message is discarded to avoid frequent recalculation of the set CC (MPR set) of adjacent nodes.

  In the conventional MPR, when a hello message is received from a node that is not registered in the adjacent node set, the MPR set is recalculated assuming that a new node has entered the ad hoc network.

  In Steps 10, 12, 14, and 16 of FIG. 5, when the management unit of the node 101-s receives a hello message (link quality: La) from the adjacent node 101-a, it can additionally manage a new adjacent node. In such a state, the set AA of adjacent nodes and the set BB of 2-hop adjacent nodes are updated. At this time, the calculated link quality La is stored in the “other” column of the adjacent node 101-a registered in the adjacent node set AA. In addition, recalculation of a set CC (MPR set) of adjacent nodes is performed.

  In step 18, the number of nodes that can be managed exceeds the number of nodes that can be managed in the set AA of adjacent nodes, and the management means of the node 101-s determines that the set of adjacent nodes AA {101-a, 101-c,. .. is managed. Here, it is assumed that the minimum link quality is Lmin among the link qualities La, Lc,...

  In steps 20, 22, 24, and 26, when the management unit of the node 101-s receives a hello message (link quality: Ld) from the adjacent node 101-d, there are more adjacent nodes than the number of manageable nodes. In the case of the state, the minimum link quality Lmin is compared with the link quality Ld calculated by the hello message from the node 101-d. When the link quality Ld of the current hello message is smaller than or equal to the minimum link quality Lmin (Lmin ≧ Ld), the received hello message from the node 101-d is discarded.

  In steps 30, 32, 34, and 36, when the management means of the node 101-s receives a hello message (link quality: Lb) from the adjacent node 101-b, there are more adjacent nodes than the number of manageable nodes. In the state to be performed, the minimum link quality Lmin is compared with the link quality Lb calculated by the hello message from the node 101-b. When the link quality Lb of the current hello message is larger than the minimum link quality Lmin (Lmin <Lb), the received hello message from the node 101-b is processed. The set AA of adjacent nodes and the set BB of 2-hop adjacent nodes are updated. In addition, recalculation of a set CC (MPR set) of adjacent nodes is performed. For example, when the link quality Lc is the minimum link quality Lmin, the link quality Lb> link quality Lc, the adjacent node 101-c is deleted from the set of adjacent nodes AA, and the adjacent node 101-b is set to the set of adjacent nodes. Add to AA.

  Adjacent nodes are not based on the link quality called LQI or RSSI, but based on the number of new nodes that are the number of adjacent nodes that do not overlap among the adjacent nodes of any adjacent node. It is also possible to select an adjacent node to be registered in the set AA.

  FIG. 6 is a diagram showing a system configuration in which a part of the ad hoc network of FIG. 1 is extracted. FIG. 7 is a diagram showing a configuration of a set of adjacent nodes and a set of 2-hop adjacent nodes of the nodes constituting the ad hoc network of FIG.

  In FIG. 6, the node 101-x holds {101-x_1,..., 101-x_i} as adjacent nodes, and the node 101-y has {101-y_1,. y_j} and the node 101-z holds {101-z_1,..., 101-z_k} as adjacent nodes.

  As shown in FIG. 7A, for each adjacent node constituting the set AA of adjacent nodes of the node 101-x, in the example of FIG. 6, for each adjacent node 101-z,. ”Identifier”, “status” such as one-way communication enabled and two-way communication enabled, “priority”, “others”, and “information on adjacent nodes” are stored. Further, the “node identifier” of the adjacent node is stored in the “adjacent node information”. The “other” column stores the calculated number of new nodes of the adjacent node, as will be described later.

  As shown in FIG. 7B, for each adjacent node constituting the set BB of 2-hop adjacent nodes of the node 101-x, in the example of FIG. 6, for each adjacent node 101-z_1,. “Node identifier”, “lifetime”, “other”, and “adjacent node information” are stored. Also, “information on adjacent node” stores “node identifier” of an adjacent node that can reach the adjacent node.

  As shown in FIG. 7C, a list of adjacent nodes that are not registered in the set AA of adjacent nodes of the node 101-x is separately stored.

  The adjacent node {101-y_1, ..., 101-y_j} of the adjacent node 101-y of the node 101-x to the adjacent node {101-x_1, ..., 101-x_i} of the node 101-x , There are M different nodes that do not overlap, that is, there are M new nodes. Further, the adjacent nodes {101-z_1, ..., 101- of the adjacent node 101-z of the node 101-x with respect to the adjacent nodes {101-x_1, ..., 101-x_i} of the node 101-x. It is assumed that z_k} includes N (M <N) different nodes that do not overlap, that is, N new nodes.

  At this time, in the node 101-x, when there are more adjacent nodes than the number of nodes that can be managed, as shown in FIGS. On the other hand, information of the adjacent node 101-z (number of new nodes = N) having a large number of new nodes is preferentially registered in the set AA of adjacent nodes and the set BB of 2-hop adjacent nodes. At this time, the calculated number of new nodes is stored in the “other” column of the adjacent node 101-z registered in the adjacent node set AA. As for the adjacent node 101-y that cannot be registered (number of new nodes = M), as shown in FIG. 7C, only the identifier of the adjacent node 101-y is held in the memory means as a list of adjacent nodes.

  Here, the example of FIG. 6 will be described by replacing the example of FIG. The nodes 101-x, 101-y, and 101-z in FIG. 6 correspond to the nodes 101-s, 101-a, and 101-b in FIG. Therefore, adjacent nodes {101-x_1,..., 101-x_i} of the node 101-x are adjacent nodes {101-a, 101-b, 101-c, 101-d} of the node 101-s. Correspond. The adjacent nodes {101-y_1,..., 101-y_j} of the node 101-y correspond to the adjacent nodes {101-s, 101-b, 101-e, 101-f} of the node 101-a. . The adjacent nodes {101-z_1, ..., 101-z_k} of the node 101-z are adjacent to the adjacent nodes {101-s, 101-a, 101-c, 101-f, 101-g of the node 101-b. , 101-h}.

  For simplicity of explanation, 101- is omitted in this paragraph. The adjacent node {s, b, e, f} of the adjacent node a of the node s overlaps with the adjacent node {a, b, c, d} of the node s, and the nodes e and f overlap. There are two different nodes that are not, that is, two new nodes. Also, the adjacent nodes {s, a, c, f, g, h} of the adjacent node b of the node s overlap with the adjacent nodes {a, b, c, d} of the node s. Then, there are three different nodes that do not overlap the nodes f, g, and h, that is, three new nodes. At this time, in the node s, when the number of adjacent nodes exceeds the number of manageable nodes, the management unit sets the adjacent node b having a larger number of new nodes than the corresponding node s (number of new nodes = 3). Information is registered in the adjacent node set AA and the 2-hop adjacent node set BB, and for the adjacent node a (number of new nodes = 3) that cannot be registered, only the identifier of the adjacent node a is listed in the adjacent node list. Held in the memory means. Note that the calculation of a new node does not include its own node (node s).

  Furthermore, the management unit of the node 101-x separately holds the minimum number of new nodes (Minimum_NewNodeNumber) in the memory unit among the information held by the adjacent nodes to be managed.

  The management means of the node 101-x calculates the number of new nodes by the adjacent node that is the source of the received hello message when there are adjacent nodes exceeding the manageable number of nodes, and this new node number is retained. If it is less than or equal to the minimum number of new nodes, the received hello message is discarded, thereby avoiding frequent recalculation of the set CC (MPR set) of adjacent nodes.

  Further, the management means of the node 101-x calculates the number of new nodes based on the adjacent node that is the transmission source of the received hello message when there are adjacent nodes exceeding the manageable number of nodes, and the number of new nodes Is larger than the minimum number of new nodes to be held, the adjacent node having the minimum number of new nodes is deleted from the set AA of adjacent nodes, and the adjacent node that is the transmission source of the current hello message is changed to It is additionally registered in the set AA. In addition, the minimum number of new nodes (Minimum_NewNodeNumber) is updated.

  As described above, nodes that make up an ad hoc network hold information on neighboring nodes based on periodically notified hello messages from neighboring nodes and expect to retransmit broadcast messages Information stored in each node by limiting the information of the adjacent nodes to be held based on the link quality called LQI or RSSI and the number of new nodes based on the adjacent node that is the source of the hello message. It is possible to reduce the amount.

  Also, when there are adjacent nodes beyond the number of manageable nodes, the link quality called LQI or RSSI of the received hello message and the number of new nodes based on the adjacent node that is the source of the hello message are checked. By discarding the hello message received according to the frequency, it is possible to avoid frequent recalculation of the set CC (MPR set) of adjacent nodes, and the set of adjacent nodes generated as a result of an increase in CPU processing load or recalculation. It becomes possible to reduce the waste of the radio band by re-notification of CC (MPR set). In addition, although demonstrated based on MPR here, another mechanism is also possible.

  As described above, according to the broadcast message transfer method in the ad hoc network according to the first embodiment of the present invention, an ad hoc network (or multihop network) in which a plurality of nodes autonomously configure the network is provided. In the system, the nodes that make up the network hold information on neighboring nodes and 2-hop neighboring nodes that are located around the node based on the periodically notified neighboring node information. When determining the pair of adjacent nodes to retransmit the message, the information amount required for the calculation can be reduced by selecting the information of the adjacent node held in the corresponding node based on the link quality and the number of new nodes. This makes it possible to construct an efficient system.

  Also, when the nodes that make up an ad hoc network or multi-hop network exceed the number of nodes that can be managed by the own node and there are adjacent nodes, the link quality and the number of new nodes are maintained to maintain the own node Compared with the corresponding information held when the hello message is received from a node not managed by the node, it is possible to reduce the frequency of various processes by detecting a new node, and there is an effect that an efficient system can be constructed.

Embodiment 2. FIG.
A node constituting an ad hoc network according to Embodiment 2 of the present invention will be described with reference to FIG.

  In the above-described first embodiment, when there are adjacent nodes exceeding the number of manageable nodes, the amount of information held in each node is reduced and frequent recalculation of a set CC (MPR set) of adjacent nodes is performed. Although the technique to avoid has been described, in the second embodiment, by restricting the information managed in the adjacent node, the node that cannot establish the bi-directional link confirms the connectivity with any adjacent node, and is necessary and sufficient It is possible to hold information on adjacent nodes.

  FIG. 8 is a diagram showing a system configuration of an ad hoc network according to the second embodiment of the present invention. In FIG. 8, an ad hoc network 100 has a plurality of nodes (Δ marks) 102 connected by wireless links to autonomously configure the network. Each node 102 includes a transmission / reception unit for transmitting / receiving a hello message, a management unit for managing information on adjacent nodes, a memory unit for storing information on adjacent nodes, a re-transfer unit for retransmitting broadcast messages, an antenna, A bidirectional confirmation means for confirming the bidirectionality of the link with the adjacent node is provided.

  In the first embodiment described above, the ad hoc network 100 configured by the nodes 101 having the same radio propagation range has been described. However, FIG. 8 illustrates an ad hoc network configured by the nodes 102 having significantly different radio propagation ranges. It is a figure which shows the network 100. FIG. In FIG. 8, the node 102-a is a node having a large radio propagation range, and the nodes 102-b and 102-c are nodes having a small radio propagation range. In particular, the node 102-b is an example that is completely included in the radio propagation range of the node 102-a.

  The node 102-a has a large number of nodes in the vicinity, that is, the number of nodes exceeds the number of nodes that can be managed by the node 102-a, and has been described in the first embodiment. Based on the link quality and the number of new nodes, for example, the adjacent node set AA is set as {102-c, 102-x, 102-y}, and information on adjacent nodes is held.

  On the other hand, the node 102-b cannot establish a bidirectional link with the node 102-a because the hello message from the node 102-a does not include the information of the own node, that is, the node 102-b. A set of adjacent nodes AA, for example, {102-j, 102-k} is held from other nodes excluding the node 102-a.

  Here, the bidirectionality confirmation means of the node 102-b is larger than the reach range of the wireless propagation of the own node with respect to a node having a clearly larger number of adjacent nodes than the number of nodes located next to the own node. A reachability confirmation message that estimates that the node has a reach and requests a response to the corresponding node is notified. For example, the hello message from the node 102-a includes the transmission power of the own node (node 102-a), and the node 102-b compares it with the transmission power of the own node (node 102-b). When the transmission power of the node 102-a> the transmission power of the node 102-b, the node 102-b has a radio propagation range larger than the radio propagation range of the node 102-b. presume.

  That is, the bidirectionality confirmation unit of the node 102-b notifies the reachability confirmation message to the node 102-a. The node 102-a that receives the reachability confirmation message that requests a response responds with the reachability confirmation response message, and the node 102-b that receives the reachability confirmation response message receives the node 102- Based on the hello message from a, the node 102-a is registered in the adjacent node set AA.

  As for the node 102-c, since the node 102-a does not exist within the wireless propagation reach of the node 102-c, the node 102-c receives the response of the reachability confirmation message for the node 102-a. Therefore, the node 102-a is not held in the set AA of the adjacent nodes of the node 102-c.

  As described above, the nodes 102 constituting the ad hoc network 100 hold information on neighboring nodes based on periodically notified hello messages from neighboring nodes and are expected to retransmit the hello message. When obtaining a node, an arbitrary node performs reachability confirmation with respect to a specific node and confirms the existence of a bidirectional link, so that a sufficient number of adjacent nodes can be obtained even in the node 102 having a small radio propagation range. And a bidirectional link can be established.

  In addition, although the example of the interactive confirmation means with respect to the node from which the reach | attainment range of radio propagation differs greatly was shown, the node exceeds the number of nodes which can be managed, and the method demonstrated in said Embodiment 1 is used. The same applies to the case where each node holds information on adjacent nodes and thus cannot recognize adjacent nodes capable of sufficient two-way communication between adjacent nodes.

  In an ad hoc network (or multi-hop network) system in which a plurality of nodes 102 autonomously constitutes a network, when there is a large difference in radio propagation characteristics between nodes constituting the network, Even a small node can establish a bidirectional link with a sufficient number of adjacent nodes, and there is an effect that an efficient system construction can be achieved.

It is a figure which shows the system configuration | structure of the ad hoc network which concerns on Embodiment 1 of this invention. It is a figure which shows the example of transfer of the hello message of the node which comprises the ad hoc network which concerns on Embodiment 1 of this invention. It is a figure which shows the system configuration | structure which took out a part of ad hoc network of FIG. FIG. 4 is a diagram illustrating a configuration of a set of adjacent nodes and a set of 2-hop adjacent nodes of nodes constituting the ad hoc network of FIG. 3. It is a flowchart which shows operation | movement of the management means of the node which comprises the ad hoc network which concerns on Embodiment 1 of this invention. It is a figure which shows the system configuration | structure which took out a part of ad hoc network of FIG. It is a figure which shows the structure of the set of the adjacent node of the node which comprises the ad hoc network of FIG. 6, and the set of 2-hop adjacent nodes. It is a figure which shows the system configuration | structure of the ad hoc network which concerns on Embodiment 2 of this invention.

Explanation of symbols

  100 ad hoc network, 101 nodes, 102 nodes.

Claims (3)

Neighboring node set next to its own node, two-hop neighboring node set reachable via neighboring node, and minimum necessary to send broadcast message to all two-hop neighboring nodes Memory means for holding a set of adjacent nodes;
A set of the adjacent nodes and a set of the two-hop adjacent nodes are created in the memory means based on the broadcast message for the adjacent nodes including the received adjacent node information, and the set of the adjacent nodes and the two-hop adjacent Management means for creating the set of adjacent nodes in the memory means based on a set of nodes;
Re-transmission means for re-transmitting the broadcast message based on the set of adjacent nodes notified from the adjacent nodes;
A node constituting an ad hoc network that periodically transmits a broadcast message for an adjacent node including information on an adjacent node of the own node,
The management means includes
In a state where there are adjacent nodes exceeding the predetermined manageable number of nodes in the set of adjacent nodes, when receiving a broadcast message for adjacent nodes including information on adjacent nodes from the adjacent first node, The minimum link quality in the set of adjacent nodes is compared with the link quality of the broadcast message for the adjacent node from the first node, and the adjacent node from the first node is compared to the minimum link quality. If the link quality of the broadcast message is small or equal, the broadcast message for the adjacent node from the first node is discarded,
When the adjacent node exceeds the predetermined manageable number of nodes in the set of the adjacent nodes, when receiving a broadcast message for the adjacent node including information on the adjacent node from the adjacent second node, The minimum link quality in the set of adjacent nodes is compared with the link quality of the broadcast message for the adjacent node from the second node, and the adjacent node from the second node is compared to the minimum link quality. When the link quality of the broadcast message is large, the third node having the minimum link quality is deleted from the set of adjacent nodes, and the second node is registered in the set of adjacent nodes. Nodes that make up the featured ad hoc network. Neighboring node set next to its own node, two-hop neighboring node set reachable via neighboring node, and minimum necessary to send broadcast message to all two-hop neighboring nodes Memory means for holding a set of adjacent nodes;
Based on the broadcast message for adjacent nodes including the received adjacent node information, the set of adjacent nodes and the set of 2-hop adjacent nodes are created in the memory means, the set of adjacent nodes, and the 2-hop adjacent Management means for creating the set of adjacent nodes in the memory means based on a set of nodes;
Re-transmission means for re-transmitting the broadcast message based on the set of adjacent nodes notified from the adjacent nodes;
A node constituting an ad hoc network that periodically transmits a broadcast message for an adjacent node including information on an adjacent node of the own node,
The management means includes
In a state where there are adjacent nodes exceeding the predetermined manageable number of nodes in the set of adjacent nodes, when receiving a broadcast message for adjacent nodes including information on adjacent nodes from the adjacent first node, The minimum number of new nodes held in advance is compared with the number of new nodes based on the adjacent node of the first node, and the number of new nodes based on the adjacent node of the first node is larger than the minimum number of new nodes. If smaller or equal, discard the broadcast message for the adjacent node from the first node;
When the adjacent node exceeds the predetermined manageable number of nodes in the set of the adjacent nodes, when receiving a broadcast message for the adjacent node including information on the adjacent node from the adjacent second node, The minimum number of new nodes held in advance is compared with the number of new nodes based on the adjacent nodes of the second node, and the number of new nodes based on the adjacent nodes of the second node is larger than the minimum number of new nodes. An ad hoc network comprising: deleting a third node having the minimum number of new nodes from the set of adjacent nodes, and registering the second node in the set of adjacent nodes. The node to configure. For a fourth node that is assumed to have a radio propagation range larger than the radio propagation range of its own node, or that is not recognized as a bidirectional adjacent node by the management means When a reachability confirmation message for requesting a response is notified and a reachability confirmation response message is received from the fourth node, a broadcast message for an adjacent node including information on an adjacent node is received from the fourth node. The node constituting the ad hoc network according to claim 1, further comprising bidirectional confirmation means for registering the fourth node in the set of adjacent nodes.

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