JP5105370B2 - COMMUNICATION SYSTEM, TERMINAL DEVICE, COMMUNICATION METHOD, AND PROGRAM - Google Patents

Description

  The present invention relates to a communication system, a terminal device, a communication method suitable for configuring a communication network formed ad hoc, and a program for realizing these by a computer.

  Conventionally, a technique in which a wireless communication device dynamically forms a communication network ad hoc has been used.

  In such a technology, one of a plurality of devices participating in a communication network is a parent device, the other device is a child device, the parent device manages the child device, and a new device is added to the communication network. When participating, the information is notified to the base unit, and when the base unit is removed from the communication network, one of the remaining slave units becomes the base unit, and the communication network is dynamically managed. There is something to do.

  For example, in a piconet used in Bluetooth (trademark) or the like, such dynamic terminal management is performed. Such communication technology is disclosed in the following literature.

  Here, in the technique disclosed in Patent Document 1, the wireless communication terminal is in an undetermined mode (corresponding to a state in which it does not participate in a communication network), a higher station mode (corresponding to “master”), or a lower station mode (“ Is a technology that changes the transmission power depending on whether the data signal is transmitted or the control signal is transmitted when a communication network is dynamically formed. It is disclosed.

Japanese Patent No. 3796537

  Here, there is a demand to form an ad hoc communication network efficiently and to allow a large number of terminal devices to communicate with each other by relaying data between clusters of a plurality of nodes.

  On the other hand, there is a great demand to suppress power consumption as much as possible in such terminal devices.

  The present invention is to solve the above-described problems, and is preferably a communication system, a terminal device, a communication method, and a computer for realizing the communication network formed in an ad hoc manner. The purpose is to provide a program.

  In order to achieve the above object, the following invention is disclosed in accordance with the principle of the present invention.

  The communication system according to the first aspect of the present invention functions as a node included in a cluster so that terminal devices communicate with each other.

  Here, the cluster includes one upper node and the other lower nodes.

On the other hand, each of the terminal devices
(1) a head node that is included in one cluster and functions as an upper node of the cluster;
(2) a normal node that is included in one cluster and functions as a lower node of the cluster;
(3) It is included in two clusters, and functions as one of gateway nodes functioning as a lower node in one cluster and functioning as an upper node in the other cluster.

  Each of the terminal devices functions as a time setting unit, a sense unit, a transmission unit, and a reception unit.

Here, when the terminal device is (1) a head node, the time setting unit sets a periodic time to all nodes included in a cluster in which the terminal device is included as a head node,
(2) In the case of a gateway node, the periodic time is included in the cluster in which the terminal device is included as an upper node so that the terminal device does not overlap with the periodic time set in the cluster included in the lower node. Set on all nodes.

  On the other hand, the sense unit performs carrier sense at a periodic time set for each of the clusters including the terminal device.

  Further, the transmission unit transmits data to other nodes in accordance with the carrier sense time.

  And a receiving part receives the data from another node according to the time of a carrier sense.

  Moreover, in the communication system of the present invention, each of the terminal devices further includes a suppression unit, and the suppression unit is configured to suppress power consumption while performing no carrier sense, performing no transmission, and performing no reception. can do.

  In the communication system of the present invention, each of the terminal devices functions as a scanning unit and a node setting unit.

  Here, the scanning unit scans another terminal device.

On the other hand, the node setting unit
(1) If no other terminal device is found, the terminal device is set as the head node,
(2) When another terminal device that can be found is a head node, the terminal device is set as a lower node of a cluster having the head node as an upper node,
(3) When the other terminal device that has been found is a gateway node, the terminal device is a lower node of the cluster having the gateway node as an upper node,
(4) When another terminal device that can be found is a normal node, the other terminal device is a gateway node, and the terminal device is a lower node of the cluster having the gateway node as an upper node.

  Further, in the communication system of the present invention, the upper node of the cluster sets a periodic time zone in which data transmission / reception should be performed directly between the nodes included in the cluster, and the transmission unit and the reception unit Data transmission and data reception can be directly performed in a set periodic time zone.

  In the communication system of the present invention, each terminal device further includes a relay unit, and can be configured as follows.

That is, when transmitting data whose final destination is another node,
(1) If the terminal device is a normal node, the terminal device transmits the data to the upper node of the cluster included as the lower node,
(2) If the terminal device is a head node or a gateway node, and the route to the final destination includes a lower node of a cluster in which the terminal device is included as an upper node, the data addressed to the other node is transferred to the lower node Send to
(3) If the terminal device is a gateway node and the route to the final destination includes an upper node of a cluster in which the terminal device is included as a lower node, the data addressed to the other node is transmitted to the upper node. .

  On the other hand, when the receiving unit receives data whose final destination is another node, the relay unit causes the transmitting unit to transmit the data.

  In the communication system of the present invention, in each of the terminal devices, when the terminal device is a head node or a gateway node, the relay unit accumulates and connects the data having the same final destination, and relays the data. As the number of lower nodes included in a cluster in which a terminal device is included as an upper node is larger, the number or size of data that are stored and linked by the final destination can be increased.

  In the communication system of the present invention, in each of the terminal devices, when the terminal device is a head node or a gateway node, the larger the number of lower nodes included in the cluster in which the terminal device is included as an upper node, A short cycle time can be set as the periodic time.

  In the communication system according to the present invention, in each terminal device, when the terminal device is a head node or a gateway node, the relay unit accumulates and connects the data having the same final destination, and relays the data. Aggregate the relay frequency for each destination, and if the route to the final destination includes a lower node of the cluster in which the terminal device is included as an upper node, the higher the relay frequency to the final destination, the higher the relay frequency to the final destination The number or size of data to be stored and linked can be increased.

  In the communication system of the present invention, in each of the terminal devices, when the terminal device is a gateway node, if the route to the final destination includes an upper node of a cluster in which the terminal device is included as a lower node, The lower the frequency of relaying to the final destination, the larger the number or size of data to be relayed and linked to the final destination.

  In the communication system of the present invention, in each terminal device, when the terminal device is a head node or a gateway node, the relay unit counts the data relay frequency, and the higher the total relay frequency, A short cycle time can be set as the periodic time.

  Further, in the communication system of the present invention, when the upper node of the cluster can directly transmit / receive data between the nodes included in the cluster using a directional beam that does not interfere with other nodes, both nodes can transmit and receive data. It is possible to configure such that a periodic time zone to be directly performed is overlapped with other non-interfering nodes.

  A terminal device according to another aspect of the present invention is a terminal device in the communication system.

  A communication method according to another aspect of the present invention functions as a node included in a cluster to allow terminal devices to communicate with each other, and is configured as follows.

  That is, the cluster is composed of one upper node and the other lower nodes.

On the other hand, each of the terminal devices
(1) a head node that is included in one cluster and functions as an upper node of the cluster;
(2) a normal node that is included in one cluster and functions as a lower node of the cluster;
(3) It is included in two clusters, and functions as one of gateway nodes functioning as a lower node in one cluster and functioning as an upper node in the other cluster.

  Furthermore, the communication method includes a time setting step, a sense step, a transmission step, and a reception step, and each step is executed in each terminal device.

Here, in the time setting step, when the terminal device is (1) a head node, the periodic time is set for all nodes included in the cluster in which the terminal device is included as a head node,
(2) In the case of a gateway node, the periodic time is included in the cluster in which the terminal device is included as an upper node so that the terminal device does not overlap with the periodic time set in the cluster included in the lower node. Set on all nodes.

  On the other hand, in the sensing step, carrier sensing is performed at a periodic time set for each of the clusters including the terminal device.

  Further, in the transmission step, data is transmitted to another node in accordance with the carrier sense time.

  In the reception step, data from other nodes is received in accordance with the carrier sense time.

  In addition, the communication method of the present invention further includes a suppression step, and in each of the terminal devices, the suppression step is configured to suppress power consumption while performing no carrier sense, no transmission, and no reception. can do.

  The communication method of the present invention further includes a scanning step and a node setting step, and each step is executed in each terminal device, and can be configured as follows.

  Here, in the scanning process, another terminal device is scanned.

On the other hand, in the node setting process, as a result of scanning,
(1) If no other terminal device is found, the terminal device is set as the head node,
(2) When another terminal device that can be found is a head node, the terminal device is set as a lower node of a cluster having the head node as an upper node,
(3) When the other terminal device that has been found is a gateway node, the terminal device is a lower node of the cluster having the gateway node as an upper node,
(4) When another terminal device that can be found is a normal node, the other terminal device is a gateway node, and the terminal device is a lower node of the cluster having the gateway node as an upper node.

  Further, in the communication method of the present invention, the upper node of the cluster sets a periodic time zone in which data should be directly transmitted and received between the nodes included in the cluster, and in the transmission step and the reception step, Data transmission and data reception can be directly performed in a set periodic time zone.

  In addition, the communication method of the present invention further includes a relay process, which is executed in each of the terminal devices and can be configured as follows.

In other words, in the transmission process, when transmitting data with the other node as the final destination,
(1) If the terminal device is a normal node, the terminal device transmits the data to the upper node of the cluster included as the lower node,
(2) If the terminal device is a head node or a gateway node, and the route to the final destination includes a lower node of a cluster in which the terminal device is included as an upper node, the data addressed to the other node is transferred to the lower node Send to
(3) If the terminal device is a gateway node and the route to the final destination includes an upper node of a cluster in which the terminal device is included as a lower node, the data addressed to the other node is transmitted to the upper node. .

  On the other hand, in the relay process, when data having the final destination as another node is received in the reception process, the data is transmitted in the transmission process.

  Further, in the communication method of the present invention, in each terminal device, when the terminal device is a head node or a gateway node, in the relay step, the data having the same final destination is accumulated and connected, and then relayed. As the number of lower nodes included in a cluster in which a terminal device is included as an upper node is larger, the number or size of data that are stored and linked by the final destination can be increased.

  In the communication method of the present invention, in each of the terminal devices, when the terminal device is a head node or a gateway node, the larger the number of lower nodes included in the cluster in which the terminal device is included as an upper node, A short cycle time can be set as the periodic time.

  In the communication method of the present invention, in each terminal device, when the terminal device is a head node or a gateway node, in the relay process, the data having the same final destination is accumulated and connected, and then relayed. Aggregate the relay frequency for each destination, and if the route to the final destination includes a lower node of the cluster in which the terminal device is included as an upper node, the higher the relay frequency to the final destination, the higher the relay frequency to the final destination The number or size of data to be stored and linked can be increased.

  In the communication method of the present invention, in each of the terminal devices, if the terminal device is a gateway node, if the route to the final destination includes an upper node of a cluster in which the terminal device is included as a lower node, The lower the frequency of relaying to the final destination, the larger the number or size of data to be relayed and linked to the final destination.

  In the communication method of the present invention, in each terminal device, when the terminal device is a head node or a gateway node, in the relay process, the data relay frequency is totaled, and the higher the total relay frequency, A short cycle time can be set as a general time.

  Further, in the communication method of the present invention, if the upper node of the cluster can directly transmit and receive data using a directional beam that does not interfere with other nodes, communication between the nodes included in the cluster can be performed. It is possible to configure such that a periodic time zone to be directly performed is overlapped with other non-interfering nodes.

  In the communication system, the communication method, and the terminal device of the present invention, the function of the gateway node can be omitted from each terminal device.

  Accordingly, in the present invention, the terminal device forms an independent cluster, and a certain terminal device forms a star network that only belongs to one cluster.

  This aspect is suitable when the terminal devices can directly communicate with each other by a directional beam, and the terminals A and B are directional within a period set for a cluster including at least the terminals A, B, C, and D. It is possible to improve the communication efficiency by overlapping the time zone in which communication is performed using the directional beam and the time zone in which the terminals C and D communicate using the directional beam.

  When a directional beam cannot be used, a time for transmitting and receiving data may be allocated to terminal devices by time division, and data can be transmitted and received by relay via a head node, and a gateway. It is also possible to apply a part of the technique of the aspect provided with this aspect to this aspect.

  Programs according to other aspects of the present invention include software radio and computers capable of wireless communication (DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), and the like. It is configured to function as each part of the terminal device.

  The program can be recorded on a computer-readable information recording medium (including a compact disk, flexible disk, hard disk, magneto-optical disk, digital video disk, magnetic tape, or semiconductor memory).

  The information recording medium can be distributed and sold independently of the computer, and the program itself can be distributed and sold via a computer communication network such as the Internet.

  ADVANTAGE OF THE INVENTION According to this invention, the communication system suitable for comprising the communication network formed in an ad hoc, a terminal device, a communication method, and the program for implement | achieving these with a computer can be provided.

  Embodiments of the present invention will be described below. The embodiments described below are for illustrative purposes and do not limit the scope of the present invention. Accordingly, those skilled in the art can employ embodiments in which each or all of these elements are replaced with equivalent ones, and these embodiments are also included in the scope of the present invention. .

  In the drawings of the present application, symbols may be omitted as appropriate for easy understanding.

  FIG. 1 is an explanatory diagram illustrating a relationship between one cluster and a plurality of terminal devices in the present embodiment. Hereinafter, a description will be given with reference to FIG.

  As shown in the figure, one cluster 101 is composed of a plurality of terminal devices 121. The terminal device 121 has two types, a higher node (denoted as “P” in the figure) and a lower node (denoted as “C” in the figure). Always includes only one upper node P, and the rest are all lower nodes C.

  The state shown in this figure corresponds to so-called star coupling, and the upper node P in the cluster 101 performs various settings for the lower node C.

  In the so-called piconet structure, the cluster 101 corresponds to a piconet coordinator (PNC) corresponding to the upper node P and a device (DEV) corresponding to the lower node C.

  In this embodiment, time allocation for performing so-called time division communication is performed.

  When N terminal devices 121 are included in one cluster 101, the transmission / reception directions are generally N (N-1). Therefore, in typical time division communication, the time allocation cycle is divided into N (N−1), and from each terminal device 121 in the cluster 101 to another terminal device 121 in each divided time zone. Allocate communication time.

  Further, when the upper node P always relays communication between the N terminal apparatuses 121, there are 2 (N-1) transmission / reception directions.

  In this case, the time allocation cycle is divided into 2 (N−1), and the communication time from a certain lower node C to the upper node P in the cluster 101 or the upper node P in each divided time zone. Communication time to a certain lower node C is allocated.

  In addition, a setting signal from the upper node P to all the lower devices C is transmitted to the head of each time slot divided in this cycle for a short time. This setting signal is most simply a synchronization signal for synchronization in all the terminal devices 121, but information such as a change in period, a change in the number of terminals, a change in time zone allocation, etc. in the setting signal, It is also possible to insert a notice that the information will be transmitted separately.

  The time when the lower node C periodically senses a signal is called “Healing period”, and the period of sensing is called “Healing interval”. The time length of the hairing period is equal to or shorter than the time length of the hairing interval.

  Also, once a communication timetable is assigned, a period for sensing communication from other nodes is also prepared for the upper node P, and as with the lower node C, a “Healing interval” and a “Healing period” are defined.

  When the control signal transmitted by the upper node P is periodically transmitted, the “Healing interval” coincides with this period, but once the communication timetable is shared in the cluster 101, the carrier sense period is the cluster 101. It is not always necessary to periodically transmit a control signal for synchronization after being shared within the network. For example, a method may be employed in which a control signal is transmitted from the upper node P in accordance with the carrier sense cycle only when various setting information is changed.

  In any case, the upper node P and the lower node C perform carrier sense in the Hairing period within the Hairing interval.

  That is, each lower node C periodically performs carrier sense of a setting signal (possibly transmitted) by the upper node P, thereby confirming whether various settings in the cluster 101 have been changed. .

  In a mode in which the upper node P does not periodically transmit a control signal, in order to confirm that the cluster 101 still exists, a control signal is transmitted during a time zone when the upper node P performs carrier sense. A signal requested from the lower node C may be transmitted so as to be transmitted.

  By adopting such a configuration, the terminal device 121 can grasp a time zone in which the terminal device 121 does not need to transmit a signal and does not need to receive the signal.

  Therefore, in the present embodiment, when the terminal device 121 autonomously shifts to the power saving mode in a time zone in which transmission / reception is not necessary, when carrier sense is performed, or when it is a time zone received by itself. When the time zone for transmission is reached, the normal power mode is restored. In this way, the power consumption of each terminal device 121 is suppressed, and the operable time is lengthened.

  The technology according to the present application can be applied to such a star-shaped network, but can be extended to a mode in which a plurality of clusters are connected.

  FIG. 2 is an explanatory diagram illustrating a state in which a gateway connects a plurality of clusters. Hereinafter, a description will be given with reference to FIG.

  As shown in the figure, each of the plurality of clusters 101 includes a plurality of terminal devices 121, and there are terminal devices 121 belonging to two clusters 101.

  As described above, the terminal devices 121 belonging to the two clusters 101 are called gateway nodes, and are indicated by a symbol G in the drawing.

  There are two clusters 101 to which the gateway node G belongs. In one cluster, the gateway node G corresponds to the lower node C in FIG. 1, and in the other cluster, the gateway node G corresponds to the upper node P in FIG. To do.

  On the other hand, a terminal device 121 that belongs to one cluster 101 and functions as the upper node P in the cluster 101 is called a head node, and is indicated by a symbol H in this figure.

  The other terminal devices 121 belong to one cluster 101 and function as the lower node C in the cluster 101. Such a terminal device 121 is called a normal node, and is indicated by a symbol N in this figure.

  In such a configuration, all the terminal devices 121 are connected on the tree via the head node H and the gateway node G. Therefore, communication between the terminal devices 121 is possible by following this tree.

  As described above, the upper node P in a certain cluster 101 manages the time division communication timetable in the cluster 101.

  The gateway node G is set by another gateway node G or the head node H with a timetable for time division communication of the cluster 101 in which the gateway node G participates as a lower node C.

  On the other hand, the gateway node G sets the time division communication timetable of the cluster 101 in which the gateway node G participates as the upper node P.

  Therefore, it is preferable that the gateway node G is set so that the two timetables do not overlap as much as possible, and in particular, the time at which both carrier scans should be performed does not overlap. When configured in this way, even if two clusters 101 come close to each other via one gateway node G, it is possible to prevent communication from interfering with each other.

  In practice, it is sufficient for the gateway node G to set a communication timetable independently of its upper node. In this case, both carrier scan times may coincide.

  FIG. 3 is an explanatory diagram showing a schematic configuration of the terminal device 121 according to the present embodiment. Hereinafter, a description will be given with reference to FIG.

  The terminal device 121 includes a scan unit 201, a node setting unit 202, a transmission unit 203, a reception unit 204, a sense unit 205, a suppression unit 206, a time setting unit 207, and a relay unit 208.

  For example, when the power is turned on, the scanning unit 201 continuously drives the reception unit 204 to check whether another terminal device 121 exists.

  If the cluster 101 has already been formed, the carrier sense control signal should be broadcast from the upper node P of the cluster 101, and this is detected.

  In addition, in order to be able to form not only a star shape but also a tree shape network, even the lower node C transmits a control signal that broadcasts its existence in the transmission time zone assigned to itself. It is typical to do so. In this case, the control signal transmitted by the lower node C is detected.

Based on the scan result, the node setting unit 202
(1) If other terminal device 121 cannot be found, set itself as head node H,
(2) If the other terminal device 121 that has been found is the head node H, it applies to the head node H to register itself so that it becomes a subordinate node C of the head node H,
(3) If the other terminal device 121 that can be found is the gateway node G, it applies to the gateway node G to register itself so that it becomes a lower node C of the gateway node G,
(3) If the other terminal device 121 that can be found is the normal node N, the operation mode of the normal node N is shifted to the gateway node G, and the terminal device 121 is changed to the lower node C of the gateway node G Apply for registration to another terminal device 121 found.

  This application is made via the transmission unit 203.

  The sense unit 205 performs carrier sense via the reception unit 204 at a periodic time set by its own upper node P in order to confirm that the cluster 101 to which it belongs is maintained.

  The suppression unit 206 controls the power consumption of the transmission unit 203 and the reception unit 204. Based on the timetable shared within the cluster 101, the suppression unit 206 saves the transmission unit 203 in a time zone in which it does not need transmission. Mode, and by setting the receiving unit 204 to the power saving mode in a time zone in which it is not necessary to receive itself, the power consumption of the entire terminal device 121 is suppressed. In addition, it is typical to set the power consumption of other units as appropriate in accordance with such a time zone.

  The relay unit 208 relays communication between other terminal devices 121 when the terminal device 121 functions as the upper node P, and cooperates with the reception unit 204 and the transmission unit 203.

When a certain terminal device 121 wants to transmit certain data to another terminal device 121 (not necessarily belonging to the same cluster 101) as the final destination, the transmission unit 203 operates as follows. Typical.
(1) When the terminal device is the normal node N, the terminal device is transmitted to the upper node P of the cluster 101 to which the terminal device belongs, with the final destination specified in the data.
(2) If the terminal device is the head node H or the gateway node G, the route to the final destination is checked, and if there is a lower node C of the cluster 101 in which the terminal device is included as the upper node P, The data is transmitted to the lower node C with the final destination specified in the data.
(3) If the terminal device is the gateway node G, the route to the final destination is checked, and if there is an upper node P of the cluster 101 in which the terminal device is included as the lower node C in the route, The destination is specified and transmitted to the upper node P.

When the receiving unit 204 receives certain data, since the relay unit 208 monitors the received data, the following processing is executed.
(1) If the final destination of the received data is itself, the data is transferred to other processing as transmitted data.
(2) If the final destination of the received data is not itself, the transmission unit 203 is processed while the final destination is specified for the data.

  In this way, data can be transmitted between the terminal devices 121.

  If it is sufficient that a star-shaped network can be configured, processing as a gateway node may be omitted as appropriate.

  FIG. 4 is an explanatory diagram showing operations of a plurality of terminal devices. In the example shown in this figure, a situation is considered in which three terminal devices 121 of Node 1, Node 2, and Node 3 communicate with each other. Hereinafter, description will be given with reference to this figure.

  First, Node 2 is powered on. Node 2 performs scanning, but since there is no other terminal device 121, Node 2 functions as a head node (Cluster head).

  Next, Node 1 is powered on (Power on). When Node 1 performs a scan (Scan) and searches for other terminal devices 121 in the vicinity, Node 2 is already functioning as a head node (Cluster head), and is thus discovered.

  Then, Node 1 performs an association (Assoc.) With Node 2 and follows the communication timetable determined by Node 2.

  Therefore, Node 1 becomes the lower node C of the cluster 101 in which Node 2 is the upper node P. Node 1 functions as a normal node.

  Next, Node 3 stands up. As a result of the same scanning performed by Node 3, Node 2 could not be detected. However, if Node 1 could be detected, Node 3 associates with Node 1.

  In response to this request, Node 1 starts a function as the gateway node G (Start), so that it forms a new cluster 101 in which itself is the upper node P, and what is the cluster 101 in which the node 1 is the lower node C? A communication timetable for performing communication in a time zone that does not overlap as much as possible is set to be shared by the newly formed cluster 101.

  In this way, the two clusters 101, the cluster 101 composed of Node 2 and Node 1 and the cluster 101 composed of Node 1 and Node 3, are hierarchically configured.

  Data transmission from Node 3 to Node 1 and from Node 1 to Node 3 is relayed by Node 2, but the communication timetable for communication (Stream) between Node 2 and Node 1 is set by Node 2. Yes, the communication timetable for communication between Node 1 and Node 3 is set by Node 1.

  Here, when the upper node P is shut down, the communication timetable is abolished, and the cluster 101 disappears.

  For example, this is a case where Node 2 is stopped (Stop) or a request for leaving (Disassoc) from Node 3 to Node 1 is made.

  FIG. 5 is a state transition diagram in the terminal device. Hereinafter, a description will be given with reference to FIG.

As shown in the figure, the terminal device 121 has six types of statuses (Status). That is,
(1) Power off represents the power off state.
(2) Dissociated represents a state in which each parameter is at an initial value without belonging to any cluster 101.
(3) Scanned represents a state that does not belong to any cluster 101 but has information such as the presence of other nodes.
(4) Normal node represents a state in which a certain cluster 101 participates as a lower node C and complies with a communication timetable determined by an upper node of the cluster 101.
(5) Cluster head represents a state in which the cluster head is operating as a head node, managing the cluster 101, and independently determining a communication timetable.
(6) The Gateway itself becomes a gateway node and participates in the two clusters 101. In one cluster 101, the host node becomes the upper node P and determines the communication timetable. In the other cluster 101, the gateway is the upper node. C represents a state according to the set communication timetable.

Further, as shown in the figure, the terminal apparatus 121 has nine types of procedures (Procedure) for performing state transition.
(1) Reset initializes various parameters such as information about the cluster 101.
(2) Scan checks for the presence of another node.
(3) Start sets a healing interval.
(4) Associate (Assoc.) Notifies that it is desired to become a lower node of a certain node. When the certain node is the head node H or the gateway node G, it becomes a lower node as it is, but when the certain node is the normal node C, the state of the certain node changes.
(5) The Stream transmits a data packet to a specific node.
(6) “Change” changes the “Healing interval”.
(7) In Syncronize (Sync.), The lower node C requests the upper node P to resynchronize the sharing interval.
(8) Disassociate (Disassoc.) Notifies the upper node P that the lower node C is leaving the cluster 101.
(9) The Stop abolishes the healing interval and notifies the terminal device 121, which is its own lower node, of this.

An example of information managed by each terminal device 121 is shown below.
(1) Node ID (8 bits) for all nodes.
(2) For all nodes, whether the current mode is Cluster head / Gateway / Normal node (2 bits).
(3) For all nodes, whether the function that the node can perform is only a normal node, or can it operate as a cluster head or gateway (1 bit).
(4) Physical parameters such as frequency and modulation method (about 40 bits) for all nodes.
(5) For all nodes, the priority order of the node (0-255, 8 bits).
(6) For the upper node, the set healing interval (0 to 65535 μs, 16 bits) is set.
(7) For the upper node, the number of nodes in the cluster (0-255, 8 bits).
(8) Intra-cluster node ID (8 bits × 0-255 nodes, total of 2048 bits) for the upper node.
(9) Normalized traffic for each node in the cluster (1 / 2256-256 / 256 err × 0-255 nodes, total 2048 bits) for the upper node.
(10) Carrier sense period (0-65535 μs, 16 bits) for the lower node.
(10) For the lower node, the node ID (8 bits) of the upper node of the participating cluster.

The structure of a transmitted frame typically includes a preamble part, a header part, and a payload part. There are the following nine types of frames.
(1) The scan request is a request to join the cluster to the head node or the gateway node.
(2) The scan response allocates a carrier sense period in response to the association request.
(3) Association request is a request for requesting a normal node to “become a gateway node to form a cluster” and to join the formed cluster.
(4) The association response is a response to the association request and assigns a carrier sense period.
(5) The synchronization request requests the upper node to resynchronize the carrier sense period.
(6) The synchronization response is a response to the synchronization request.
(7) Announce transmits specific information between nodes.
(8) Data is normal data.
(9) Ack is a so-called acknowledgment (acknowledgment).

  Details of each procedure will be described below.

  First, the Reset procedure initializes parameters in the node.

  Next, the Scan procedure is performed as follows. FIG. 6 is an explanatory diagram showing the flow of the Scan procedure. Hereinafter, a description will be given with reference to FIG.

  When the execution node (Node 1) transmits a Scan request command frame, the node (Node 2 and Node 3) that senses this command continues carrier sense until the end of the frame.

  The sensed node returns a Scan response command after the Backoff time at the end of the frame.

  The Scan response command includes information about the sharing interval when the node that transmitted the Scan response can be an upper node or a higher node.

  Furthermore, the Start procedure sets a node mode, a healing interval set by the upper node itself, a carrier sense period in which the lower node is set (this is equivalent to the healing interval), and other intra-node parameters.

  The Associate procedure is performed as follows. FIG. 7 is an explanatory diagram showing the flow of the Associate procedure. Hereinafter, a description will be given with reference to FIG.

  When Node 1 requests an association to a specific node (Node 3) based on the Scan result, Node 1 transmits an Association request command frame in accordance with the Sharing interval set by that node (Node 3).

  The receiving node (Node 3) returns an Association response command.

  On the other hand, the Stream procedure transmits data to other nodes in the cluster, and FIG. 8 is an explanatory diagram showing the flow of the Stream procedure.

  As shown in the figure, data is transmitted according to a communication interval shared within the cluster (Healing interval).

  Furthermore, the Change procedure is for notifying the change of the intra-cluster parameter within the cluster. FIG. 9 is an explanatory diagram showing the flow of the change procedure.

  As shown in the figure, the information is made known by multicasting the Announce command frame.

  In the Synchronize procedure, the lower node in the cluster requests the higher node again to notify the sharing interval. FIG. 10 is an explanatory diagram showing the flow of the Synchronize procedure.

  As shown in FIG. In Node 1 that has transmitted the request, the Sync. A response is received. After the response time-out period ends, resynchronization at Node 1 is performed (not shown).

  The Dissociate procedure notifies the higher level node that the lower level node does not follow the “Healing interval” thereafter. Is. FIG. 11 is an explanatory diagram showing the flow of the Dissociate procedure.

  As shown in the figure, this procedure is realized by transmitting an Announce command frame to the upper node.

  The Stop procedure notifies the other nodes in the cluster that the upper node is to abolish the healing interval. FIG. 12 is an explanatory diagram showing the flow of the Stop procedure.

  As shown in the figure, the Stop procedure is realized by multicasting an Announce command frame.

  This embodiment proposes a technique in which the upper node appropriately sets the communication timetable in the above embodiment.

  That is, the upper node P sets the time length of the healing interval (carrier sense cycle) and the time length of the time zone available for data transmission according to the number of lower nodes C participating in the cluster 101 managed by the upper node P. It is something to change.

  Here, the “Healing period” in a certain terminal device 121 can be used not only for transmission / reception of control signals but also for data transmission itself. When a signal addressed to itself is detected by carrier sense in the carrier period, data can be accepted by continuing the reception as it is even after the termination of the carrier period.

  Therefore, if the ratio of the healing period to the healing interval increases, the power consumption in each terminal device 121 increases, but the transmission capacity also increases. Therefore, it is suitable when the number of lower nodes C is large.

  Conversely, if the ratio of the healing period to the healing interval is reduced, the power consumption in each terminal device 121 can be reduced, but the transmission capacity is reduced. Therefore, it is suitable when the number of lower nodes C is small.

  FIG. 13 is an explanatory diagram showing a state of a healing interval and a hairing period assigned by a head node and a gateway node. Hereinafter, a description will be given with reference to FIG.

  As shown in this figure, the Healing period set by Node 1 and the Healing period set by Node 2 are set so as not to overlap each other as much as possible. This is because Node 2, which is a gateway node, sets a healing interval and a healing period so as to avoid duplication.

  In the figure, the ratio of the hairing period to the hairing interval is also different. This takes into account the number of lower nodes C in the cluster 101 and the transmission flow rate.

  In this embodiment, in the above embodiment, by connecting the data transmitted to the same final destination in the upper node, the overhead redundancy in which the headers are duplicated is reduced and the short data is prevented from colliding with each other. It improves communication efficiency.

  In this embodiment, the relay unit 208 monitors the final destination of the data received by the receiving unit 204, accumulates the data of the same final destination until the data connection size determined in advance is reached, and concatenates these. Then, the data is transmitted to the transmission unit 203. Here, it is necessary to consider the shape of the network when determining the data connection size.

  That is, whether it is upstream (whether it is close to the head node) and whether the number of lower nodes is large.

  FIG. 14 is an explanatory diagram showing the number of data processed by each node when each terminal device transmits data to the head node in a tree-type network.

  As shown in the figure, since there is a bias in the amount of data to be transmitted, a suitable data connection size (Preferential aggregation size at reach relaying node) in the gateway node is different from each other.

  That is, the larger the number of lower nodes of the terminal device 121, the larger the data connection size, and the smaller the number, the smaller the data connection size.

  In this case, the communication efficiency can be further improved by further shortening the healing interval and increasing the ratio of the healing period.

  In this method, the data connection size is determined only by the number of subordinate nodes as an approximation of the total number of all downstream nodes. However, by combining with the following method, the data connection size can be further adjusted. Adjustment is possible.

  That is, the relay unit 208 counts the frequency of relaying data for each final destination.

  And when the final destination is on the lower node side (downstream, far from the head node), the higher the relay frequency to the final destination, the larger the data connection size, and the lower the lower, Reduce the data connection size. This corresponds to the case where the terminal device 121 having the relay unit 208 is a head node or a gateway node.

  On the other hand, when the final destination is on its own upper node side (upstream, near the head node), the higher the relay frequency to the final destination, the smaller the data connection size, and the lower the lower, Increase the data connection size. This corresponds to a case where the terminal device 121 having the relay unit 208 is a gateway node.

  At this time, the length of the Hairing interval and the ratio of the Hairing period can be adjusted in the same manner as described above.

  FIG. 15 is a graph showing a result of transmission performance simulation when data is linked. As shown in the figure, it can be seen that when data is linked, collision between data is reduced and communication efficiency is improved.

  In the above embodiment, in order to prevent the communication of the terminal devices 121 in the cluster 101 from colliding with each other in the communication timetable, every transmission / reception between the pair of terminal devices 121 or between each lower node and higher node. One frame was allocated from the communication time zone for each transmission / reception. Hereinafter, “frame” in the communication timetable is referred to as “communication channel”.

  Here, not all the terminal devices 121 in the cluster 101 may arbitrarily communicate with each other, but only some of the terminal devices 121 may communicate with each other.

  FIG. 16 is an explanatory diagram showing a state of communication channels assigned to the upper node and the lower node. In the figure, the upper node is represented as “Master” and the lower node is represented as “Slave”.

  In this figure, a communication channel from Master to all Slaves (Master to all), a communication channel from Slave 1 to Master (Slave 1 to Master), a communication channel from Slave 2 to Slave 1 (Slave 2 to Slave 1) These three communication channels are time-divisionally set so as not to overlap each other.

  In a communication channel from the master to all slaves, a control signal for communication channel assignment is transmitted always or as necessary.

  Also, only Slave 1 to Master and Slave 2 to Slave 1 are assumed as communication channels for the individual terminal devices 121 to exchange data. Under such a premise, communication efficiency can be improved by not allocating a communication channel for data transmission / reception between Slave 2 and Master or data transmission / reception in the opposite direction.

  Communication channels are generally assigned when a request is made from Slave to Master when it becomes necessary. However, if the direction of data transmission does not change, it may be determined in advance. Is possible.

  In addition, when the terminal device 121 can perform communication using a directional beam, the assignment method can be changed. That is, depending on the beam directivity conditions, transmission / reception that should originally be assigned a different time zone in the communication timetable can be performed in the same time zone.

  17 and 18 are explanatory diagrams illustrating setting of a communication timetable using a directional beam.

  In the example shown in this figure, each lower node (Slave) has four directions as beam directivities.

  The upper node (Master) manages the beam directivity direction of each lower node and information on which lower node the direction is directed to.

  Under this situation, each lower node requests the upper node to assign a communication channel by designating a data destination as necessary.

  Then, the upper node enumerates beam directivity pairs suitable for transmission / reception of the transmission source specified in the allocation request and its destination.

  Then, the allocation requests are classified so that the transmission / reception sets do not interfere with each other.

  Here, “a plurality of transmissions / receptions do not interfere” means that the same node does not appear repeatedly as a source and a destination of the plurality of transmissions / receptions, that is, a certain node in the communication channel This means that only reception from a node is performed, or transmission to only one other node is performed.

  In the example shown in FIG. 17, the communication from Slave 1 to Slave 2 and the communication from Slave 3 to Slave 4 do not interfere with each other.

  For this reason, communication channels can be assigned to the same time zone.

  In the example shown in FIG. 18, the communication from Slave 3 to Slave 1 and the communication from Slave 1 to Slave 2 interfere with each other because Slave 1 transmits and receives at the same time. Therefore, even if communication channel allocation is requested at the same time, it is rejected.

  The transmission / reception beam directivity pair is generally notified from the upper node to the lower node when the communication channel assignment is notified.

  When the time zone of the assigned communication channel is reached, each lower terminal determines the direction of transmission directivity or the direction of reception directivity based on information specified in the control signal transmitted from the upper node. Data is sent and received.

  Note that the above examples all consider the situation where the directional beam ranges do not overlap each other.

  Accordingly, it is possible to make congestion less likely by adding that the range of directional beams in the transmission and reception does not overlap with the condition that “a plurality of transmissions and receptions do not interfere”.

  However, a mode may be adopted in which the range of the directional beam of each node is set so that all other nodes are included, and communication channels from all nodes to all nodes are allocated simultaneously.

  FIG. 19 is an explanatory diagram showing a state in which all nodes share a communication channel in the same time zone under such a situation.

  Under such circumstances, it is preferable that each node manages directivity to other nodes and transmits data only when its directivity setting is appropriate.

  As described above, according to the present invention, it is possible to provide a communication system, a terminal device, a communication method suitable for configuring a communication network formed in ad hoc, and a program for realizing these by a computer. Can do.

It is explanatory drawing which shows the relationship between the one cluster and several terminal device in this embodiment. It is explanatory drawing which shows a mode that a gateway connects a some cluster. It is explanatory drawing which shows schematic structure of the terminal device which concerns on this embodiment. It is explanatory drawing which shows operation | movement of a some terminal device. It is a state transition diagram in a terminal device. It is explanatory drawing which shows the flow of a Scan procedure. It is explanatory drawing which shows the flow of an Associate procedure. It is explanatory drawing which shows the flow of a Stream procedure. It is explanatory drawing which shows the flow of Change procedure. It is explanatory drawing which shows the flow of a Synchronize procedure. It is explanatory drawing which shows the flow of Dissociate procedure. It is explanatory drawing which shows the flow of a Stop procedure. It is explanatory drawing which shows the mode of the Hairing interval and Heading period which a head node and a gateway node allocate. FIG. 4 is an explanatory diagram showing the number of data processed by each node when each terminal device transmits data to the head node in a tree-type network. It is a graph which shows the result of the transmission performance simulation at the time of connecting data. It is explanatory drawing which shows the mode of the communication channel allocated to a high-order node and a low-order node. It is explanatory drawing which shows the setting of the communication timetable using a directional beam. It is explanatory drawing which shows the setting of the communication timetable using a directional beam. It is explanatory drawing which shows a mode that the communication channel of the same time slot | zone is shared by all the nodes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Cluster 121 Terminal device 201 Scan part 202 Node setting part 203 Transmission part 204 Reception part 205 Sense part 206 Suppression part 207 Time setting part 208 Relay part

Claims (34)

A communication system in which terminal devices communicate with each other by functioning as nodes included in a cluster,
(A) The cluster is composed of one upper node and the other lower nodes,
(B) Each of the terminal devices
(1) a head node that is included in one cluster and functions as an upper node of the cluster;
(2) a normal node that is included in one cluster and functions as a lower node of the cluster;
(3) It is included in two clusters, functions as a lower node in one cluster, functions as one of gateway nodes functioning as an upper node in the other cluster,
(C) Each of the terminal devices
When the terminal device is (1) a head node, the periodic time is set for all nodes included in a cluster in which the terminal device is included as a head node;
(2) When it is a gateway node, the periodic time is set to the cluster in which the terminal device is included as an upper node so that the terminal device does not overlap with the periodic time set in the cluster included in the lower node. A time setting unit to be set for all included nodes,
A sense unit for performing carrier sense at a periodic time set for each of the clusters including the terminal device;
A transmitter that transmits data to other nodes in accordance with the time of the carrier sense;
A communication system comprising: a receiving unit that receives data from another node in accordance with the carrier sense time. The communication system according to claim 1,
Each of the terminal devices
A communication system, further comprising: a suppression unit that suppresses power consumption while performing no carrier sense, performing no transmission, and performing no reception. The communication system according to claim 1 or 2,
Each of the terminal devices
A scanning unit for scanning other terminal devices,
The result of the scan,
(1) When another terminal device cannot be found, the terminal device is set as a head node,
(2) When another terminal device that can be found is a head node, the terminal device is set as a lower node of a cluster having the head node as an upper node,
(3) When another terminal device that can be found is a gateway node, the terminal device is a lower node of the cluster having the gateway node as an upper node;
(4) If the other terminal device that has been found is a normal node, the node setting unit further comprising: the other terminal device as a gateway node; and the terminal device as a lower node of a cluster having the gateway node as an upper node. A communication system comprising: A communication system according to claim 3,
The upper node of the cluster sets, for each node included in the cluster, a periodic time zone in which data should be transmitted and received directly between the two,
The transmission unit and the reception unit directly perform data transmission and data reception in the set periodic time zone. The communication system according to claim 3, wherein in each of the terminal devices,
When the transmission unit transmits data whose final destination is another node,
(1) When the terminal device is a normal node, the terminal device transmits the data to an upper node of a cluster included as a lower node,
(2) If the terminal device is a head node or a gateway node and the route to the final destination includes a lower node of a cluster in which the terminal device is included as an upper node, the data addressed to the other node is Send to lower nodes,
(3) If the terminal device is a gateway node and the route to the final destination includes an upper node of a cluster in which the terminal device is included as a lower node, data destined for the other node is transferred to the upper node. Send
The communication system further comprising: a relay unit that causes the transmission unit to transmit the data when the reception unit receives data whose final destination is another node. The communication system according to claim 5, wherein in each of the terminal devices,
When the terminal device is a head node or a gateway node, the relay unit accumulates and connects data having a common final destination and relays the data,
A communication system, characterized in that the larger the number of lower nodes included in a cluster in which the terminal device is included as an upper node, the larger the number or size of data that are stored and linked by the final destination. The communication system according to any one of claims 1 to 6, wherein in each of the terminal devices,
When the terminal device is a head node or a gateway node, a shorter cycle time is set as the periodic time as the number of lower nodes included in the cluster in which the terminal device is included as a higher node is larger. A communication system. The communication system according to any one of claims 5 to 7, wherein each of the terminal devices includes:
When the terminal device is a head node or a gateway node, the relay unit accumulates and connects data with common final destinations, relays, and counts the relay frequency for each final destination,
If the route to the final destination includes a lower node of the cluster in which the terminal device is included as an upper node, the higher the relay frequency to the final destination, the more data to be relayed to the final destination is accumulated and connected. A communication system characterized by increasing the number or size. The communication system according to claim 8, wherein in each of the terminal devices,
When the terminal device is a gateway node, if the route to the final destination includes an upper node of a cluster in which the terminal device is included as a lower node, the lower the relay frequency to the final destination, the lower the final destination A communication system characterized by increasing the number or size of data to be stored and connected to the relay. The communication system according to any one of claims 5 to 9, wherein in each of the terminal devices,
When the terminal device is a head node or a gateway node, the relay unit counts the data relay frequency, and sets a shorter cycle time as the periodic time as the tabulated relay frequency is higher. A communication system characterized by the above. The communication system according to any one of claims 1 to 10,
When the upper node of the cluster can directly transmit and receive communication between nodes included in the cluster using a directional beam that does not interfere with other nodes, the upper node of the cluster can transmit data within the set time period. A communication system, characterized in that a periodic time zone in which transmission and reception should be performed directly is set to overlap with other non-interfering nodes.   The terminal device in the communication system of any one of Claim 1 to 11. A communication method in which terminal devices communicate with each other by functioning as a node included in a cluster,
(A) The cluster is composed of one upper node and the other lower nodes,
(B) Each of the terminal devices
(1) a head node that is included in one cluster and functions as an upper node of the cluster;
(2) a normal node that is included in one cluster and functions as a lower node of the cluster;
(3) It is included in two clusters, functions as a lower node in one cluster, functions as one of gateway nodes functioning as an upper node in the other cluster,
(C) In each of the terminal devices,
When the terminal device is (1) a head node, the periodic time is set for all nodes included in a cluster in which the terminal device is included as a head node;
(2) When it is a gateway node, the periodic time is set to the cluster in which the terminal device is included as an upper node so that the terminal device does not overlap with the periodic time set in the cluster included in the lower node. A time setting process to be set for all nodes included,
A sensing step of performing carrier sense at a periodic time set for each of the clusters including the terminal device;
A transmission step of transmitting data to another node in accordance with the time of the carrier sense;
A communication method comprising: a receiving step of receiving data from another node in accordance with the carrier sense time. The communication method according to claim 13, comprising:
In each of the terminal devices,
A communication method further comprising: a suppressing step of suppressing power consumption while not performing the carrier sense, not performing the transmission, and not performing the reception. The communication method according to claim 13 or 14,
In each of the terminal devices,
Scanning process for scanning other terminal devices,
The result of the scan,
(1) When another terminal device cannot be found, the terminal device is set as a head node,
(2) When another terminal device that can be found is a head node, the terminal device is set as a lower node of a cluster having the head node as an upper node,
(3) When another terminal device that can be found is a gateway node, the terminal device is a lower node of the cluster having the gateway node as an upper node;
(4) When the other terminal device that has been found is a normal node, the node setting step further includes setting the other terminal device as a gateway node, and setting the terminal device as a lower node of a cluster having the gateway node as an upper node. A communication method characterized by comprising: The communication method according to claim 15, comprising:
The upper node of the cluster sets, for each node included in the cluster, a periodic time zone in which data should be transmitted and received directly between the two,
In the transmission step and the reception step, data transmission and data reception are directly performed in the set periodic time zone. The communication method according to claim 15, comprising:
In each of the terminal devices,
In the transmission step, when transmitting data whose final destination is another node,
(1) When the terminal device is a normal node, the terminal device transmits the data to an upper node of a cluster included as a lower node,
(2) If the terminal device is a head node or a gateway node and the route to the final destination includes a lower node of a cluster in which the terminal device is included as an upper node, the data addressed to the other node is Send to lower nodes,
(3) If the terminal device is a gateway node and the route to the final destination includes an upper node of a cluster in which the terminal device is included as a lower node, data destined for the other node is transferred to the upper node. Send
The communication method further comprising: a relay step of transmitting the data in the transmission step when the data having the other node as the final destination is received in the reception step. The communication method according to claim 17, wherein in each of the terminal devices,
When the terminal device is a head node or a gateway node, in the relay process, the data is shared by connecting the final destination and relayed,
A communication method characterized in that the larger the number of lower nodes included in a cluster in which the terminal device is included as an upper node, the larger the number or size of data that is stored and linked by the final destination. The communication method according to any one of claims 13 to 18, wherein in each of the terminal devices,
When the terminal device is a head node or a gateway node, a shorter cycle time is set as the periodic time as the number of lower nodes included in the cluster in which the terminal device is included as a higher node is larger. Communication method. The communication method according to claim 17 or 18, wherein in each of the terminal devices,
When the terminal device is a head node or a gateway node, in the relay step, data is shared and relayed after common destinations, and the relay frequency is tabulated for each final destination,
If the route to the final destination includes a lower node of the cluster in which the terminal device is included as an upper node, the higher the relay frequency to the final destination, the more data to be relayed to the final destination is accumulated and connected. A communication system characterized by increasing the number or size. The communication method according to claim 20, wherein in each of the terminal devices,
When the terminal device is a gateway node, if the route to the final destination includes an upper node of a cluster in which the terminal device is included as a lower node, the lower the relay frequency to the final destination, the lower the final destination A communication method characterized by increasing the number or size of data to be linked and stored. The communication method according to any one of claims 17, 18, 20, or 21, wherein each of the terminal devices includes:
When the terminal device is a head node or a gateway node, in the relay process, the data relay frequency is totaled, and the higher the aggregated relay frequency, the shorter the time is set as the periodic time. A communication method characterized by the above. The communication method according to any one of claims 13 to 22,
When the upper node of the cluster can directly transmit and receive the communication between the nodes included in the cluster using a directional beam that does not interfere with other nodes, a periodic transmission and reception of data between the two should be performed. A communication method characterized in that a different time zone is set to overlap with other non-interfering nodes.   A program for causing a software radio or a computer having a communication function to function as the terminal device according to claim 12. A communication system in which terminal devices communicate with each other by functioning as nodes included in a cluster,
(A) The cluster is composed of one upper node and the other lower nodes,
(B) Each of the terminal devices
(1) a head node that is included in one cluster and functions as an upper node of the cluster;
(2) a normal node that is included in one cluster and functions as a lower node of the cluster;
Function as one of
(C) Each of the terminal devices
When the terminal device is a head node, a time setting unit that sets a periodic time to all nodes included in a cluster in which the terminal device is included as a head node,
A sense unit for performing carrier sense at a periodic time set for each of the clusters including the terminal device;
A transmitter that transmits data to other nodes in accordance with the time of the carrier sense;
A receiving unit that receives data from other nodes in time with the carrier sense time,
The upper node of the cluster sets, for each node included in the cluster, a periodic time zone in which data should be transmitted and received directly between the two,
The transmitting unit and the receiving unit directly perform data transmission and data reception in the set periodic time zone,
When the communication between the nodes included in the cluster can be directly transmitted / received using a directional beam that does not interfere with other nodes, the time setting unit transmits / receives data within the set time period. The communication system is characterized in that a periodic time zone to be directly performed between the two is set to overlap with other non-interfering nodes. The communication system according to claim 25, wherein
Each of the terminal devices
A communication system, further comprising: a suppression unit that suppresses power consumption while performing no carrier sense, performing no transmission, and performing no reception. A communication system according to claim 25 or 26, wherein
Each of the terminal devices
A scanning unit for scanning other terminal devices,
The result of the scan,
(1) When another terminal device cannot be found, the terminal device is set as a head node,
(2) When another terminal device that can be found is a head node, the terminal device is set as a lower node of a cluster having the head node as an upper node,
(3) A communication system, further comprising: a node setting unit that uses the terminal device as a head node when another terminal device that can be found is a normal node. The communication system according to any one of claims 25 to 27, wherein each of the terminal devices includes:
When the terminal device is a head node, a shorter cycle time is set as the periodic time as the number of lower nodes included in the cluster in which the terminal device is included as a higher node is larger. system.   A terminal device in the communication system according to any one of claims 25 to 28. A communication method in which terminal devices communicate with each other by functioning as a node included in a cluster,
(A) The cluster is composed of one upper node and the other lower nodes,
(B) Each of the terminal devices
(1) a head node that is included in one cluster and functions as an upper node of the cluster;
(2) a normal node that is included in one cluster and functions as a lower node of the cluster;
Function as one of
(C) In each of the terminal devices,
When the terminal device is a head node, a time setting step of setting a periodic time to all nodes included in a cluster in which the terminal device is included as a head node,
A sensing step of performing carrier sense at a periodic time set for each of the clusters including the terminal device;
A transmission step of transmitting data to another node in accordance with the time of the carrier sense;
A receiving step of receiving data from other nodes in time with the carrier sense time,
The upper node of the cluster sets, for each node included in the cluster, a periodic time zone in which data should be transmitted and received directly between the two,
In the transmission step and the reception step, data transmission and data reception are directly performed in the set periodic time zone,
In the time setting step, when communication between nodes included in the cluster can be performed directly using a directional beam that does not interfere with other nodes, data transmission / reception is performed within the set time period. A communication method characterized in that a periodic time zone to be directly performed between the two is set to overlap with other non-interfering nodes. The communication method according to claim 30, wherein
In each of the terminal devices,
A communication method further comprising: a suppressing step of suppressing power consumption while not performing the carrier sense, not performing the transmission, and not performing the reception. The communication method according to claim 30 or 31, wherein
In each of the terminal devices,
Scanning process for scanning other terminal devices,
The result of the scan,
(1) When another terminal device cannot be found, the terminal device is set as a head node,
(2) When another terminal device that can be found is a head node, the terminal device is set as a lower node of a cluster having the head node as an upper node,
(3) A communication method, further comprising: a node setting step in which the terminal device is a head node when another terminal device that has been found is a normal node. The communication method according to any one of claims 30 to 32, wherein each of the terminal devices includes:
When the terminal device is a head node, a shorter cycle time is set as the periodic time as the number of lower nodes included in the cluster in which the terminal device is included as a higher node is larger. Method.   30. A program causing a software radio or a computer having a communication function to function as the terminal device according to claim 29.

Images