JP7815159B2 - Communication device, communication method, and program - Google Patents

Description

Embodiments of the present invention relate to a communication device, a communication method, and a program.

Technologies disclosed include the automatic configuration of a tree-structured (DAG: Directed Acyclic Graph) communication path (a so-called mesh network), a technology in which each node (an example of a communication device) passes data along via a bucket relay, and a technology in which a parent node with good communication quality and a small number of hops to an aggregation device is selected and automatically switched over. Here, an aggregation device is also called a border router, concentrator, root node, etc.

Algorithms are also disclosed that collect information about neighboring nodes and use the collected information to select a parent node. Here, the information about neighboring nodes may include the received signal strength level (RSSI: Received Signal Strength Indicator, LQI: Link Quality Indicator), ETX, which indicates the frame arrival rate, path cost (or Rank value), etc.

The received radio wave level is the reception level of frames received from the local node to a neighboring node. Alternatively, the received radio wave level is the reception level of frames received from a neighboring node to the local node. ETX is a value calculated from the number of data frames transmitted from the local node to a neighboring node and the number of data frames arriving at the local node. The path cost is, for example, the product of the number of hops from the aggregation device to the neighboring node and a fixed value. The path cost may also be the cumulative total of communication quality values from the aggregation device to the neighboring node, or the product of the number of hops from the aggregation device to the neighboring node and a fixed value, plus the cumulative total of communication quality values from the aggregation device to the neighboring node.

Patent No. 6164001

However, with conventional technology, due to limited memory capacity in communication devices, it may not be possible to store information about all neighboring nodes. Furthermore, no algorithm is known for managing information about a new neighboring node when memory resources for storing information about neighboring nodes are depleted and a new neighboring node is detected. Specifically, no algorithm is known for managing whether, when a new neighboring node is detected, stored information about any neighboring nodes is discarded, or information about the new neighboring node is discarded without being stored. Furthermore, no information management method is known for stabilizing a multi-hop network in a short period of time. For example, the technology described in Patent Document 1 simply uses a first-to-win system, and when memory resources are depleted, information about existing neighboring nodes is not evicted and information about the newly detected neighboring node is not retained.

The present invention has been made in consideration of the above, and aims to provide a communication device, communication method, and program that can stabilize a multi-hop network in a short time when memory resources for storing information about neighboring nodes are depleted and a new neighboring node is detected.

The communication device of the embodiment includes a storage unit, a route control unit, a test frame transmission/reception unit, and a public relations frame reception unit. The storage unit stores a neighbor table containing neighborhood information including communication quality with neighboring nodes. The route control unit selects a parent node from among the neighboring nodes based on the neighborhood information contained in the neighbor table. The test frame transmission/reception unit transmits a test frame to the neighboring node, measures the communication quality with the neighboring node, and updates the neighborhood information based on the measured communication quality. The public relations frame reception unit receives a public relations frame from a new neighboring node, and if the neighbor information of the new neighboring node that is the sender of the public relations frame does not exist in the neighbor table, there is no free space in the neighbor table, and the number of neighboring nodes whose communication quality has been measured among the neighboring nodes whose neighborhood information is stored in the neighbor table is less than a predetermined number, the public relations frame reception unit does not register the neighborhood information of the new neighboring node in the neighbor table.

FIG. 1 is a block diagram illustrating an example of a configuration of a communication device according to a first embodiment. FIG. 2 is a diagram illustrating an example of a neighbor table included in the communication device according to the first embodiment. FIG. 3 is a flowchart illustrating an example of the flow of a process for registering neighborhood information of a neighboring node in the communication device according to the first embodiment. FIG. 4 is a flowchart illustrating an example of the flow of a process of searching for a neighboring node that is a candidate for deletion in the communication device according to the first embodiment. FIG. 5 is a flowchart illustrating an example of the flow of a process for registering neighborhood information of a neighboring node in the communication device according to the second embodiment. FIG. 6 is a flowchart illustrating an example of the flow of a process for searching for a neighboring node with the worst received radio wave level in the communication device according to the second embodiment.

Below, an example of a communication device, communication method, and program according to this embodiment will be described with reference to the accompanying drawings.

(First embodiment)
1 is a block diagram showing an example of the configuration of a communication device according to the first embodiment. As shown in FIG. 1, the communication device 1 according to the present embodiment includes a route control unit 101, a PR frame transmission unit 102, a PR frame reception unit 103, a test frame transmission/reception unit 104, a storage unit 105, and a wireless communication interface 106.

The memory unit 105 is an example of a memory unit that stores a neighbor table. Here, the neighbor table is a management table that contains neighborhood information about neighboring nodes, such as the communication quality with neighboring nodes. The wireless communication interface 106 manages wireless communication between the communication device 1 (referred to as the local device or local node) and external devices such as neighboring nodes.

The route control unit 101 is an example of a route control unit that selects a parent node from among neighboring nodes based on the neighborhood information contained in the neighbor table. In this embodiment, the route control unit 101 selects a parent node when the neighborhood information is updated. For example, the route control unit 101 selects a parent node in accordance with RFC 6552, RFC 6719, or the like.

The test frame transmission/reception unit 104 transmits test frames to neighboring nodes. Here, the test frames are frames for measuring the communication quality between the neighboring nodes and the node itself. The test frames may also be unicast frames for data communication with a server or other nodes.

In this embodiment, the test frame transmission/reception unit 104 transmits test frames to at least neighboring nodes whose neighbor information is stored in the neighbor table in order to measure the communication quality between the node and neighboring nodes. The test frames may be transmitted periodically, or in accordance with the Trickle Timer (RFC6206), for example.

Furthermore, when the test frame transmitting/receiving unit 104 receives any frame, including a test frame, from another node, such as a neighboring node, it updates the neighbor information (e.g., received radio wave level) of the neighboring node that is the sender of the test frame, among the neighbor information contained in the neighbor table. In other words, the test frame transmitting/receiving unit 104 functions as an example of a test frame transmitting/receiving unit that transmits a test frame to a neighboring node, measures the communication quality with the neighboring node, and updates the neighbor information based on the measured communication quality. In this embodiment, the test frame transmitting/receiving unit 104 updates the neighbor information of the neighboring node that is the sender of the test frame when an ACK is received after transmitting the test frame, or when the wait for an ACK times out.

The PR frame transmitter 102 transmits a PR frame including the path cost from the aggregation device to the local node to a neighboring node. Here, the PR frame may be data including the path cost from the aggregation device to the local node. For example, the PR frame may be a DIO as described in the RPL of RFC6550, or a beacon such as IEEE802.15.4, Bluetooth (registered trademark), or a wireless LAN (Local Area Network). In this embodiment, the PR frame transmitter 102 may transmit the PR frame at any timing.

The PR frame receiving unit 103 processes PR frames received from neighboring nodes. Specifically, the PR frame receiving unit 103 receives PR frames from new neighboring nodes. Furthermore, if the neighbor information of the new neighboring node that is the sender of the received PR frame is not present in the neighbor table, there is no free space in the neighbor table, and the number of neighboring nodes whose neighbor information is stored in the neighbor table and whose communication quality has been measured is less than a predetermined number n, the PR frame receiving unit 103 does not register the neighbor information of the new neighboring node in the neighbor table. Here, the predetermined number n is a number set in advance. As a result, neighbor information is not deleted from the neighbor table until the number of neighboring nodes whose communication quality has been measured reaches the predetermined number n. As a result, it becomes easier to increase the number of neighboring nodes whose communication quality has been measured, thereby shortening the time until the network stabilization is achieved.

Furthermore, if the neighbor information of the new neighboring node does not exist in the neighbor table, there is no free space in the neighbor table, and the number of neighboring nodes whose neighbor information is stored in the neighbor table that have already measured their communication quality is equal to or greater than a predetermined number n, the public relations frame receiving unit 103 calculates a first cost and a second cost. Here, the first cost is the sum of the communication quality with the neighboring node whose neighbor information is stored in the neighbor table and the path cost from the aggregation device to the neighboring node. Furthermore, the second cost is the sum of the path cost from the aggregation device to the new neighboring node and a preset path cost.

The public relations frame receiving unit 103 then sets the neighboring node with the largest first cost as the neighboring node of the deletion candidate, and if the second cost is greater than the first cost of the neighboring node of the deletion candidate, it resets the neighboring node of the deletion candidate to a new neighboring node. Furthermore, if the neighbor information of the neighboring node of the deletion candidate exists in the neighbor table, the public relations frame receiving unit 103 deletes the neighbor information of the neighboring node of the deletion candidate from the neighbor table and registers the neighbor information of the new neighboring node in the neighbor table. This allows neighboring nodes that improve the packet delivery rate to the aggregation device to remain in the neighbor table, so that the multi-hop network can be stabilized in a short time when the memory resources for holding neighbor information are depleted and a new neighboring node is detected.

Figure 2 is a diagram illustrating an example of a neighbor table included in a communication device according to the first embodiment. In this embodiment, the neighbor table stored in the storage unit 105 includes, as shown in Figure 2, neighboring node addresses, path costs, first received radio wave levels, second received radio wave levels, first communication quality values, second communication quality values, and communication quality value measurement status.

The neighboring node address is information that identifies a neighboring node registered in the neighbor table, and may be, for example, the EUI64 of the neighboring node. The path cost is the path cost from the aggregation device to the neighboring node, and the smaller the value, the better the probability that packets will reach the aggregation device. Here, the aggregation device may be a border router, concentrator, or root node. For example, the path cost may be the Rank defined in RFC6550, RFC6552, or RFC6719, the number of hops on the path from the aggregation device to the neighboring node, or the cumulative communication quality on the path from the aggregation device to the neighboring node.

The first received radio wave level is the received radio wave level at the local node. Specifically, the first received radio wave level is the received radio wave level of any frame that arrives at the local node from a neighboring node. The second received radio wave level is the received radio wave level of a test frame from the local node that arrives at a neighboring node.

The higher the first and second received radio wave levels, the better the communication quality with neighboring nodes is estimated to be. The first received radio wave level may be a moving average value of the received radio wave level of any frame received by the node from a neighboring node. The second received radio wave level may be a moving average value of the received radio wave level of a test frame received by the node from the node to a neighboring node. The value of the second received radio wave level is recorded, for example, in a frame transmitted from a neighboring node. The first and second received radio wave levels are used to calculate the third received radio wave level. The third received radio wave level may be the same value as the first received radio wave level. The third received radio wave level may also be the smaller of the first received radio wave level and the second received radio wave level. The third received radio wave level is used as the received radio wave level when communicating between the node and a neighboring node.

The first communication quality value is the communication quality value of the test frame sent to a neighboring node. The second communication quality value is the communication quality value of the test frame sent from a neighboring node to the node itself. Specifically, the first and second communication quality values may be numerical values that represent the probability that the test frame packet will arrive, and it is estimated that the smaller the value, the better the communication quality between the node itself and the neighboring node.

For example, the first and second communication quality values may be calculated using the following equation (1).
First and second communication quality values = MinCost × number of acknowledgement frames (ACK) received from neighboring nodes ÷ number of test frames transmitted to neighboring nodes (1)
Alternatively, the first and second communication quality values may be moving average values of the values calculated by the above formula (1).

The communication quality measured status is a status that indicates whether the communication quality with a neighboring node has been measured. For example, where m is a natural number greater than or equal to 1, when the number of attempts to send a test frame to a neighboring node since registering the neighboring node's neighborhood information in the neighbor table reaches m, the test frame transmitting/receiving unit 104 changes the communication quality measured status of the neighboring node to True, and when the public relations frame receiving unit 103 registers a new neighboring node, it initializes the communication quality measured status of the neighboring node to False. Note that the test frame transmitting/receiving unit 104 may also change the communication quality measured status of the neighboring node to True when the number of attempts to send a test frame to the neighboring node since registering the neighboring node's neighborhood information in the neighbor table reaches m and a frame containing a second communication quality value is received from the neighboring node.

Figure 3 is a flowchart showing an example of the flow of the neighbor information registration process for a neighboring node in a communication device according to the first embodiment. When a public relations frame is received from a neighboring node, the public relations frame receiving unit 103 determines whether the neighbor information for the neighboring node that is the sender of the public relations frame exists in the neighbor table (step S301). If the neighbor information for the neighboring node of the sender exists in the neighbor table (step S301: Yes), the public relations frame receiving unit 103 updates the neighbor information for the neighboring node of the sender in the neighbor table and terminates the process (step S302). For example, the public relations frame receiving unit 103 updates the first received radio wave level.

If the neighbor table does not contain neighbor information for the sender's neighbor node (step S301: No), the PR frame receiving unit 103 determines whether there is space in the neighbor table (step S303). Here, "space in the neighbor table" means that the number of neighbor information items for neighbor nodes is less than a preset number. If there is space in the neighbor table (step S303: Yes), the PR frame receiving unit 103 adds (registers) the neighbor information for the sender's neighbor node (i.e., a new neighbor node) to the neighbor table (step S304).

If there is no free space in the neighbor table (step S303: No), the PR frame receiving unit 103 determines whether the number of neighboring nodes in the neighbor table whose communication quality value measured status is True is less than a predetermined number n (step S305). If the number of neighboring nodes whose communication quality value measured status is True is less than the predetermined number n (step S305: Yes), the PR frame receiving unit 103 does not register the neighborhood information of new neighboring nodes in the neighbor table. This makes it easier to increase the number of neighboring nodes whose communication quality has been measured, thereby shortening the time it takes for the network to stabilize.

If the number of neighboring nodes whose communication quality value measured status is True is equal to or greater than the predetermined number n (step S305: No), the PR frame receiving unit 103 searches for the neighboring node with the worst communication quality (hereinafter referred to as the deletion candidate neighboring node) (step S306). Next, it determines whether the neighbor information of the deletion candidate neighboring node exists in the neighbor table (step S307). If the neighbor information of the deletion candidate neighboring node does not exist in the neighbor table (step S307: No), that is, if the new neighboring node is the deletion candidate neighboring node, the PR frame receiving unit 103 does not delete the neighbor information from the neighbor table, and does not register the neighbor information of the new neighboring node in the neighbor table.

Furthermore, if the neighborhood information of the neighboring node that is a candidate for deletion exists in the neighbor table (step S307: Yes), the PR frame receiving unit 103 deletes the neighborhood information of the neighboring node that is a candidate for deletion from the neighbor table (step S308) and registers the neighborhood information of the new neighboring node in the neighbor table (step S309). This allows neighboring nodes that are estimated to have the worst communication quality to be deleted preferentially, allowing neighboring nodes with good communication quality between the node and the node itself to remain in the neighbor table, thereby shortening the time it takes for the multi-hop network to stabilize.

Figure 4 is a flowchart showing an example of the flow of a process for searching for neighboring nodes of a deletion candidate in a communication device according to the first embodiment. First, the PR frame receiving unit 103 sets the neighboring nodes of the deletion candidate to nil and sets the Worst Cost to 0 (step S401). Here, Worst Cost is the path cost of the neighboring nodes of the deletion candidate.

The PR frame receiving unit 103 performs steps S402 to S406 for each of all neighboring nodes (assuming neighboring node x) in the neighbor table. The PR frame receiving unit 103 determines whether neighboring node x, whose neighbor information is registered in the neighbor table, is a parent node (step S402). If neighboring node x is a parent node (step S402: Yes), the PR frame receiving unit 103 removes neighboring node x from the list of neighboring nodes to be deleted. If neighboring node x is not a parent node (step S402: No), the PR frame receiving unit 103 determines whether a test frame has not yet been sent to neighboring node x (step S403). If a test frame has not yet been sent to neighboring node x (step S403: Yes), the PR frame receiving unit 103 removes neighboring node x from the list of neighboring nodes to be deleted. This makes it less likely that neighboring nodes whose communication quality values have not been measured will be expelled from the neighbor table. This means that nearby nodes with potentially good communication quality are more likely to remain in the neighbor table, shortening the time it takes for the multi-hop network to stabilize.

If a test frame has already been sent to neighboring node x (step S403: No), the PR frame receiving unit 103 calculates the cost of neighboring node x as the sum of the path cost from the aggregation device to neighboring node x and the communication quality value with neighboring node x (step S404). Here, the path cost from the aggregation device to neighboring node x may be the value stated in the PR frame. Next, the PR frame receiving unit 103 determines whether the calculated cost is greater than the Worst Cost (step S405).

If the calculated cost is less than or equal to the Worst Cost (step S405: No), the PR frame receiving unit 103 removes neighboring node x from the list of neighboring nodes to be deleted. On the other hand, if the calculated cost is greater than the Worst Cost (step S405: Yes), the PR frame receiving unit 103 sets the calculated cost as the Worst Cost and sets neighboring node x as a neighboring node to be deleted (step S406). The PR frame receiving unit 103 then repeats the processes of steps S402 to S406 for all neighboring nodes in the neighbor table.

After steps S402 to S406 have been repeated for all neighboring nodes in the neighbor table, the PR frame receiving unit 103 calculates the cost by adding the path cost from the aggregation device to the new neighboring node and a preset MinCost (step S407). This makes it possible to compare the new neighboring node with neighboring nodes in the neighbor table. Here, MinCost is the communication quality value when the network is at its most stable, and may be a preset fixed value.

Next, the PR frame receiving unit 103 determines whether the neighboring node of the deletion candidate is nil or whether the cost calculated in step S407 is greater than the Worst Cost (step S408). If the neighboring node of the deletion candidate is not nil and the cost calculated in step S407 is less than or equal to the Worst Cost (step S408: No), the PR frame receiving unit 103 returns the neighboring node of the deletion candidate without setting a new neighboring node as the neighboring node of the deletion candidate (step S409). On the other hand, if the neighboring node of the deletion candidate is nil or the cost calculated in step S407 is greater than the Worst Cost (step S408: Yes), the PR frame receiving unit 103 sets a new neighboring node as the neighboring node of the deletion candidate (step S410) and returns the neighboring node of the deletion candidate (step S409). This allows neighboring nodes that improve the packet delivery rate to the aggregation device to remain in the neighbor table.

In this way, according to the communication device 1 of the first embodiment, neighboring nodes with poor communication quality are preferentially deleted from the neighbor table among the neighboring nodes whose neighbor information is registered, and neighboring information is not deleted from the neighbor table until the number of neighboring nodes whose communication quality has been measured reaches a predetermined number n. As a result, when the memory resources for storing neighboring information are depleted and a new neighboring node is detected, the multi-hop network can be stabilized in a short time.

Second Embodiment
In this embodiment, a neighbor node having poor communication quality is deleted from the neighbor table based on the third received radio wave level. In the following description, a description of the same configuration as in the first embodiment will be omitted.

In this embodiment, the public relations frame receiving unit 103 deletes from the neighbor table the neighbor information of the neighbor node with the lowest third received radio wave level among the neighbor nodes whose neighbor information is included in the neighbor table and the new neighbor node. Specifically, the public relations frame receiving unit 103 sets the neighbor node with the lowest third received radio wave level among the neighbor nodes whose neighbor information is registered in the neighbor table as the neighbor node to be deleted. Next, if the third received radio wave level of the new neighbor node is lower than the third received radio wave level of the neighbor node to be deleted, the public relations frame receiving unit 103 resets the new neighbor node to the neighbor node to be deleted and deletes the neighbor information of the neighbor node to be deleted from the neighbor table. This allows nodes that are too far from the communication device 1 to be removed from the parent node options early on, thereby shortening the time it takes for the network to stabilize.

Figure 5 is a flowchart showing an example of the flow of the process for registering neighbor information of neighboring nodes in a communication device according to the second embodiment. In this embodiment, if there is no free space in the neighbor table (step S303: No), the public relations frame receiving unit 103 searches for the neighboring node with the lowest third received radio wave level (neighboring node candidate for deletion) among neighboring nodes whose neighbor information is included in the neighbor table and new neighboring nodes (step S501). Next, the public relations frame receiving unit 103 determines whether a neighboring node candidate for deletion has been found (step S502).

If a neighboring node that is a candidate for deletion is found (step S502: Yes), the PR frame receiving unit 103 proceeds to step S307 and determines whether the neighbor information of the neighboring node that is a candidate for deletion exists in the neighbor table. This allows nodes that are too far from the communication device 1 to be removed from the parent node options early on, thereby shortening the time it takes for the network to stabilize. On the other hand, if a neighboring node that is a candidate for deletion is not found (step S502: No), the PR frame receiving unit 103 proceeds to step S305 and determines whether the number of neighboring nodes whose communication quality value measurement status in the neighbor table has been measured is less than a predetermined number n.

Figure 6 is a flowchart showing an example of the process flow for searching for a neighboring node with the worst received radio wave level in a communication device according to the second embodiment. First, the PR frame receiving unit 103 sets the neighboring node to be deleted to nil and sets the Worst Level to 0 (step S601). Here, the Worst Level is the third received radio wave level of the neighboring node to be deleted.

The public information frame receiving unit 103 repeats the processes shown in steps S602 to S606 for each of all neighboring nodes (referred to as neighboring node x) in the neighbor table. The public information frame receiving unit 103 determines whether the third received radio wave level during communication with a neighboring node whose neighbor information is registered in the neighbor table is sufficiently strong (step S602). Here, a sufficiently strong third received radio wave level may be equal to or greater than a preset threshold for the received radio wave level. Alternatively, a sufficiently strong third received radio wave level may be equal to or greater than threshold B during communication with a neighboring node at least once and never falls below threshold B thereafter.

If the third received radio wave level during communication with neighboring node x is sufficiently strong (step S602: Yes), the public relations frame receiving unit 103 removes neighboring node x from the list of neighboring nodes to be deleted. If the third received radio wave level is not sufficiently strong (step S602: No), the public relations frame receiving unit 103 determines whether neighboring node x is a parent node (step S603). If neighboring node x is a parent node (step S603: Yes), the public relations frame receiving unit 103 removes neighboring node x from the list of neighboring nodes to be deleted.

If neighboring node x is not a parent node (step S603: No), the PR frame receiving unit 103 sets the third received radio wave level when communicating with neighboring node x to level (step S604). Next, the PR frame receiving unit 103 determines whether the set level is lower than the Worst Level (step S605). If the set level is equal to or higher than the Worst Level (step S605: No), the PR frame receiving unit 103 removes neighboring node x from the list of neighboring nodes to be deleted. On the other hand, if the set level is lower than the Worst Level (step S605: Yes), the PR frame receiving unit 103 sets the third received radio wave level when communicating with neighboring node x to Worst Level and sets neighboring node x as a neighboring node to be deleted (step S606).

Then, the PR frame receiving unit 103 determines whether the neighboring node of the deletion candidate is nil (step S607). If the neighboring node of the deletion candidate is nil (step S607: Yes), the PR frame receiving unit 103 determines whether the third received radio wave level when communicating with the new neighboring node is sufficiently strong (step S608), as in step S602. If the third received radio wave level when communicating with the new neighboring node is sufficiently strong (step S608: Yes), the PR frame receiving unit 103 returns a message indicating that there is no neighboring node of the deletion candidate (step S609).

If the third received radio wave level during communication with the new neighboring node is not sufficiently strong (step S608: No), the public relations frame receiving unit 103 sets the new neighboring node as a neighboring node to be deleted (step S610) and returns the new neighboring node as a neighboring node to be deleted (step S609).

Also, if the neighboring node candidate for deletion is not nil (step S607: No), the PR frame receiving unit 103 determines whether the third received radio wave level during communication with the new neighboring node is lower than the Worst Level (step S611). If the third received radio wave level during communication with the new neighboring node is equal to or higher than the Worst Level (step S611: No), the PR frame receiving unit 103 returns the neighboring node candidate for deletion set in steps S602 to S606 (step S609).

If the third received radio wave level during communication with the new neighboring node is lower than the Worst Level (step S611: Yes), the PR frame receiving unit 103 sets the new neighboring node as a neighboring node candidate for deletion (step S610) and returns the neighboring node candidate for deletion (step S609).

In this way, with the communication device 1 according to the second embodiment, nearby nodes with low received radio wave levels due to reasons such as being too far from the communication device 1 can be quickly removed from the list of parent node options, thereby shortening the time it takes for the network to stabilize.

As described above, according to the first and second embodiments, when memory resources for storing neighbor information are depleted and a new neighboring node is detected, the multi-hop network can be stabilized in a short time.

The program executed by the communication device 1 of this embodiment is provided in advance in a ROM (Read Only Memory) or the like. The program executed by the communication device 1 of this embodiment may also be provided by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD-ROM, flexible disk (FD), CD-R, or DVD (Digital Versatile Disk).

Furthermore, the program executed by the communication device 1 of this embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Furthermore, the program executed by the communication device 1 of this embodiment may be provided or distributed via a network such as the Internet.

The program executed by the communication device 1 of this embodiment may be configured as a module including the above-mentioned units (route control unit 101, public relations frame transmission unit 102, public relations frame reception unit 103, test frame transmission/reception unit 104, and wireless communication interface 106), and the actual hardware may be configured such that an example of a processor such as a CPU (Central Processing Unit) reads and executes the program from the above-mentioned ROM, thereby loading the above-mentioned units onto the main memory, and generating the route control unit 101, public relations frame transmission unit 102, public relations frame reception unit 103, test frame transmission/reception unit 104, and wireless communication interface 106 on the main memory.

While several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in a variety of other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

REFERENCE SIGNS LIST 1 Communication device 101 Route control unit 102 Public information frame transmitting unit 103 Public information frame receiving unit 104 Test frame transmitting/receiving unit 105 Storage unit 106 Wireless communication interface

Claims (6)

a storage unit that stores a neighbor table including neighbor information including communication quality with neighboring nodes;
a route control unit that selects a parent node from among the neighboring nodes based on the neighbor information included in the neighbor table;
a test frame transmitting/receiving unit that transmits a test frame to the neighboring node, measures communication quality with the neighboring node, and updates the neighborhood information based on the measured communication quality;
a public relations frame receiving unit that receives a public relations frame from a new neighboring node, and when the neighbor information of the new neighboring node that is the source of the public relations frame does not exist in the neighbor table, there is no free space in the neighbor table, and the number of the neighboring nodes that have measured the communication quality among the neighboring nodes whose neighbor information is stored in the neighbor table is less than a predetermined number, does not register the neighbor information of the new neighboring node in the neighbor table;
A communication device comprising: The public information frame receiving unit
If the neighbor information of the new neighbor node does not exist in the neighbor table, there is no free space in the neighbor table, and the number of the neighbor nodes whose neighbor information is stored in the neighbor table and whose communication quality has been measured is equal to or greater than the predetermined number,
calculating a first cost by adding together the communication quality with the neighboring node whose neighbor information is stored in the neighbor table and a path cost from the aggregation device to the neighboring node;
Calculating a second cost by adding a path cost from the aggregation device to the new neighboring node and a preset path cost;
Set the neighboring node with the largest first cost as a neighboring node of the deletion candidate, and if the second cost is greater than the first cost of the neighboring node of the deletion candidate, set the new neighboring node as a neighboring node of the deletion candidate again;
2. The communication device according to claim 1, wherein if the neighborhood information of the neighbor node of the deletion candidate exists in the neighbor table, the neighborhood information of the neighbor node of the deletion candidate is deleted from the neighbor table, and the neighborhood information of the new neighbor node is registered in the neighbor table. the test frame transmitting/receiving unit measures, as the communication quality, a received radio wave level of the test frame from the neighboring node or a received radio wave level of the test frame from the communication device that has reached the neighboring node;
The communication device according to claim 1 or 2, wherein the public relations frame receiving unit deletes from the neighbor table the neighbor information of the neighbor node whose received radio wave level is the lowest among the neighbor nodes whose neighbor information is included in the neighbor table and the new neighbor node. The communication device of claim 3, wherein the PR frame receiver sets the neighboring node with the lowest received radio wave level among the neighboring nodes whose neighbor information is registered in the neighbor table as a neighboring node to be deleted, and if the received radio wave level of the new neighboring node is lower than that of the neighboring node to be deleted, re-sets the new neighboring node as the neighboring node to be deleted, and deletes the neighboring information of the neighboring node to be deleted from the neighbor table. 1. A communication method performed in a communication device, comprising:
a step of a route control unit selecting a parent node from among the neighboring nodes based on neighbor information included in a neighbor table and including communication quality with the neighboring nodes;
a test frame transmitting/receiving unit transmitting a test frame to the neighboring node, measuring communication quality with the neighboring node, and updating the neighborhood information based on the measured communication quality;
a PR frame receiving unit receiving a PR frame from a new neighboring node, and when the neighbor information of the new neighboring node that is the source of the PR frame does not exist in the neighbor table, there is no free space in the neighbor table, and the number of the neighboring nodes whose neighbor information is stored in the neighbor table and whose communication quality has been measured is less than a predetermined number, not registering the neighbor information of the new neighboring node in the neighbor table;
A communication method including: Computer,
a route control unit that selects a parent node from among the neighboring nodes based on neighbor information included in the neighbor table and including communication quality with the neighboring nodes;
a test frame transmitting/receiving unit that transmits a test frame to the neighboring node, measures communication quality with the neighboring node, and updates the neighborhood information based on the measured communication quality;
a public relations frame receiving unit that receives a public relations frame from a new neighboring node, and when the neighbor information of the new neighboring node that is the source of the public relations frame does not exist in the neighbor table, there is no free space in the neighbor table, and the number of the neighboring nodes that have measured the communication quality among the neighboring nodes whose neighbor information is stored in the neighbor table is less than a predetermined number, does not register the neighbor information of the new neighboring node in the neighbor table;
A program to make it function as such.