JP2019169844A - Information acquisition device, mobile, information acquisition method, and program - Google Patents

Abstract

To provide an information acquisition device capable of effective utilization of a radio resource.SOLUTION: An information acquisition device 2 provided in an autonomous traveling mobile 1, includes: a wide-area communication part 21 for executing wide-area radio communication; a short-range communication part 22 for executing short-range radio communication; a cluster head determination part 33 for determining whether the own mobile is a cluster head or a cluster member, in a cluster constituted of the multiple mobiles 1 approaching each other; a determination part 23 for determining whether the own mobile is the cluster head or the cluster member on the basis of determination results; and an information management part 24 for receiving information from an information server via the wide-area communication part 21 and storing it and then transmitting the stored information to the mobile 1 of the cluster member via the short-range communication part 22 in response to a request from the mobile 1 of the cluster member when the own mobile is the cluster head, and for receiving the information from the information server from the mobile 1 of the cluster head via the short-range communication part 22 when the own mobile is the cluster member.SELECTED DRAWING: Figure 2

Description

   The present invention relates to an information acquisition apparatus that acquires information managed in an information server.

  In order to support safe movement and social participation of elderly people and persons with disabilities, realization of a moving body that moves autonomously at a low speed, such as an electric wheelchair, has been demanded (for example, see Non-Patent Document 1). Moreover, as such a mobile body that moves autonomously, for example, an entertainment robot, a transport robot, and the like are also known.

Tsutomu Hatase, Kimi Wakamatsu, Hideki Nishimura, Hirotoshi Yamamoto, "Intelligent Wheelchair Robot", FUJITSU, Vol. 57, No. 3, p. 263-268, May 2006

  Mobile objects such as electric wheelchairs use high-capacity information such as an altitude map database during autonomous movement. The altitude map database is, for example, information having information on a moving route (for example, a road) and information on an object such as an obstacle on the moving route. In the future, when a large number of mobile objects such as electric wheelchairs are used, such a large amount of information is transmitted from the information server to each mobile object. And, for example, in a situation where traffic density is high such as intersections waiting for traffic lights and commuting rush, and many mobile objects such as electric wheelchairs are overcrowded, each mobile object receives information from the information server by high-power wireless communication. If the acquisition is attempted, radio interference or radio communication collision occurs over a wider range, which may cause a significant decrease in throughput or communication failure. As a result, the number of mobile bodies that can access the information server at the same time decreases, and there is a possibility that problems such as the need to temporarily stop autonomous movement by mobile bodies that cannot access the information server may occur.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to accommodate more mobile objects in finite radio resources by efficiently using radio resources. It is to provide a movable body that can be used, and an information acquisition device provided in the movable body.

  In order to achieve the above object, an information acquisition apparatus according to the present invention is an information acquisition apparatus provided in a mobile body that moves autonomously, and includes a wide area communication unit that performs wide area wireless communication, and wireless communication by a wide area communication unit In a cluster composed of a short-range communication unit that performs wireless communication in a narrower range and a plurality of mobile units that are close to each other, a determination unit that determines whether the mobile unit is a cluster head or a cluster member When the mobile unit is a cluster head, it receives and stores information from the information server via the wide area communication unit, and stores the stored information in response to a request from the cluster member mobile unit. When it is transmitted to the mobile member of the cluster member via the distance communication unit, and the mobile unit itself is a cluster member, it requests the information managed by the information server from the mobile unit of the cluster head, and class An information management unit which receives via the short distance communication unit from a mobile of the head, but with the.

  With such a configuration, in each cluster, information is acquired from the information server by the moving body of the cluster head, and each cluster member acquires information from the cluster head. Therefore, acquisition of information from the information server can be hierarchized. Further, by performing wireless communication between the cluster head and the cluster member via the short-range communication unit, it is possible to reduce the influence of the wireless communication on the wireless communication in other clusters. As a result, more mobile units can appropriately acquire information from the information server. Therefore, it is possible to construct a radio communication network that can effectively use radio resources and can accommodate more mobile objects in finite radio resources.

  In the information acquisition device according to the present invention, the determination unit may determine that the mobile body is a cluster head when the condition defined by the cluster head determination unit in the short-range communication unit is satisfied.

  The condition defined by the cluster head determining unit may be determined as a cluster head when an integer type random number within a certain range is generated and equal to a specified integer.

  With such a configuration, a moving body that is considered to be suitable as a moving body for the cluster head, that is, a moving body that can pass information to more moving bodies can be used as a cluster head.

  In the information acquisition apparatus according to the present invention, the number of moving bodies in one cluster may be equal to or less than a threshold value.

  With such a configuration, for example, even when wireless communication using one channel is performed in one cluster, it is avoided that many mobile objects concentrate on wireless communication of a certain channel. Will be able to.

  In the information acquisition apparatus according to the present invention, when the number of moving bodies in one cluster exceeds a threshold, the number of moving bodies in one cluster is equal to or less than the threshold. It may be divided.

  With such a configuration, when mobile objects are concentrated in a certain cluster, the cluster is divided into two or more clusters, so that wireless communication in each cluster can be prevented from being crowded.

  Further, in the information acquisition device according to the present invention, the determination unit is a cluster member when the number of moving bodies in a cluster to which the moving body belongs exceeds a threshold value and the moving body is a cluster head. If the number of mobile objects in the cluster to which the mobile object belongs exceeds the threshold, the mobile object of the new cluster head selected from If there is a notification from the moving body of the cluster head that the moving body becomes the cluster head, the moving body determines that the moving body is the cluster head and the moving body becomes the cluster head. If the notification is not received, it may be determined that the cluster member is an existing cluster head or a new cluster head.

  With this configuration, the cluster can be divided by using the moving body selected by the information acquisition apparatus in the existing moving body of the cluster head as a new moving body of the cluster head.

  Further, in the information acquisition device according to the present invention, when the mobile body is a cluster head, the number of mobile bodies in the cluster to which the mobile body belongs is transmitted to the network control server via the wide area communication unit, and the network control server Communication control for receiving wireless communication channels performed by the short-range communication unit from the network control server via the wide-area communication unit, which are assigned to each cluster so that the number of mobile bodies for each channel is equalized Wireless communication by the short-range communication unit between each mobile unit in the cluster to which the mobile unit of the cluster head belongs may be performed using a channel received from the network control server by the communication control unit of the cluster head .

  With such a configuration, wireless communication in each cluster is performed using the wireless communication channel assigned by the network control server, so that the number of mobile bodies using each wireless communication channel can be made uniform.

  Moreover, the mobile body by this invention is provided with an information acquisition apparatus, and moves autonomously using the information acquired by the information acquisition apparatus.

  Further, the information acquisition method according to the present invention is an information acquisition method in a mobile body that moves autonomously, and in a cluster composed of a plurality of mobile bodies close to each other, whether the mobile body is a cluster head, Step of determining whether or not the member is a cluster member, and when the mobile unit is a cluster head, receives and stores information from the information server via wide-area communication that is wide-area wireless communication, and the mobile member of the cluster member In response to a request from the user, the stored information is transmitted to the mobile member of the cluster member via short-range communication that is wireless communication in a narrower range than wide-area communication. The information management step of requesting information managed by the information server to the moving body of the cluster head and receiving it from the moving body of the cluster head via short-range communication. When, those having a.

  According to the information acquisition apparatus and the like according to the present invention, even when the mobile bodies are densely packed, more mobile bodies can appropriately acquire information from the information server.

It is a figure which shows an example of a structure of the information communication system in embodiment. It is a block diagram which shows the structure of the moving body by embodiment. It is a flowchart which shows operation | movement of the information acquisition apparatus by embodiment. It is a flowchart which shows operation | movement of the information acquisition apparatus by embodiment. It is a flowchart which shows operation | movement of the information acquisition apparatus by embodiment. It is a flowchart which shows operation | movement of the information acquisition apparatus by embodiment. It is a figure which shows an example of arrangement | positioning of the mobile body in embodiment. It is a figure which shows an example of arrangement | positioning of the mobile body in embodiment. It is a figure which shows an example of arrangement | positioning of the mobile body in embodiment. It is a figure which shows an example of a structure of the computer system in embodiment.

  Hereinafter, a mobile object according to the present invention will be described using embodiments. In the following embodiments, components and steps denoted by the same reference numerals are the same or equivalent, and repetitive description may be omitted. The mobile body according to the present embodiment forms a cluster with mobile bodies that are close to each other, and hierarchically obtains information from the information server. In addition, it is assumed that wide-area wireless communication is wireless communication with a radius of 100 meters or more, and short-range wireless communication is wireless communication with a distance of 10 meters or less.

  FIG. 1 is a diagram illustrating an example of a configuration of an information communication system according to the present embodiment. The information communication system according to the present embodiment includes a plurality of mobile units 1, an information server 3, a network control server 4, an LTE base station 5, and access points (AP) 6 and 7. The information server 3, the network control server 4, the LTE base station 5, and the access points 6 and 7 are connected via a communication line 500. The communication line 500 is usually a wired line, and may be, for example, the Internet, an intranet, a public telephone line network, or the like. The communication line 500 may be considered as a set of a plurality of communication lines.

  Each mobile unit 1 can perform wide-area wireless communication and short-range wireless communication. The mobile unit 1 can access the information server 3 and the network control server 4 through the LTE base station 5 and the access points 6 and 7 by wide area wireless communication. The wide area wireless communication may be, for example, cellular communication such as LTE (Long Term Evolution), communication by wireless LAN (Local Area Network) (IEEE 802.11 wireless communication), or the like. Moreover, the mobile body 1 can exchange information with the surrounding mobile bodies 1 by short-range wireless communication. Note that short-range wireless communication is wireless communication performed with lower power than wide-area wireless communication. Therefore, the short-range wireless communication range is narrower than the wide-range wireless communication range. The short-range wireless communication may be, for example, communication using a wireless LAN or communication using Bluetooth (registered trademark). When both wide-area and short-range wireless communication is wireless LAN communication, both may be physically configured by two devices, the wide-area and the short-range, and the wide-area and the short-range are integrated. However, the transmission power of the two devices is different. In addition, it may be considered that INFRA (infrastructure) is used when performing wireless communication over a wide area via an AP, and ADHOC (ad hoc) mode is used when performing short-range wireless communication.

In addition, a cluster is formed by a plurality of moving bodies 1 close to each other. This cluster is a group of mobile bodies 1 that share information managed in the information server 3. Usually, one cluster is formed by a plurality of moving bodies 1 existing in a close range. This cluster is composed of a moving body 1 of one cluster head and a moving body 1 of one or more cluster members. Then, it is the moving body 1 of the cluster head that accesses the information server 3 or the like via wide area wireless communication and receives information from the information server 3, and the moving body 1 of the cluster member is the moving body of the cluster head. The information acquired and stored by 1 is acquired via short-range wireless communication. In this way, wireless communication is hierarchized into short-range wireless communication within the cluster and wide-area wireless communication beyond the cluster, and congestion of wide-area wireless communication can be avoided. Moreover, since short-distance wireless communication is performed with lower power, more mobile units 1 can simultaneously perform short-distance wireless communication. Therefore, as a result, radio resources are effectively used, and more mobile units 1 can be accommodated in the information communication system. It is ideal that the moving body 1 belongs to any cluster, but as shown in FIG. 1, there may be a moving body 1 that does not belong to any cluster. Such a moving body 1 may be considered as a moving body of a cluster head in a cluster in which no cluster member exists. Further, it is preferable that the number of moving bodies 1 in one cluster, that is, the number of moving bodies 1 belonging to the cluster is equal to or less than a threshold value. The threshold value may be a predetermined value. As described above, in order to limit the number of moving bodies 1 in one cluster to a threshold value or less, for example, when the number of moving bodies 1 in one cluster exceeds the threshold value, one cluster exists. May be divided so that the number of the moving bodies 1 in the cluster is equal to or less than the threshold value, or only one number of moving bodies 1 equal to or less than the threshold value can belong to one cluster in advance. Good. Thus, the fact that the number of moving bodies 1 in one cluster is equal to or smaller than a threshold value may be equal to or smaller than the threshold value as a result of division or the like.

  Although FIG. 1 shows the case where the mobile body 1 is an electric wheelchair, the mobile body 1 may be anything that moves autonomously, and may be, for example, mobility such as an entertainment robot or a transport robot. . The autonomous movement may be, for example, movement along a route acquired by route search or the like, and movement to an appropriate position according to the surrounding situation (for example, an entertainment robot guides Or approaching a nearby person to perform a conversation or the like. In general, the moving body 1 moves at a low speed. Low speed means that the moving body 1 which is a cluster member existing in one cluster moves autonomously outside the cluster, is not a cluster member, and becomes a cluster member in another cluster or a cluster head of another cluster. The period means that the moving speed is high enough to share information such as map data acquired when the member is a cluster member in the previous cluster, and may be defined as, for example, an average of 6 km / h. This is because when the moving body 1 moves at a higher speed, it is necessary to reconstruct the cluster frequently, so that it becomes difficult to share information appropriately.

  The information server 3 is a server that manages information. Each moving body 1 acquires information managed by the information server 3 directly or indirectly, and performs autonomous movement using the information. The information may be, for example, map information such as an altitude map database or other information used in the mobile body 1. In the present embodiment, a case will be mainly described in which the information acquired and used by the mobile body 1 from the information server 3 is map information. The map information having detailed information is large-capacity data, but the same mobile map 1 can use the same map information. Therefore, the map information cached in the cluster head mobile 1 is used by the cluster member mobile 1 so that the map information can be used effectively.

  The network control server 4 assigns a channel used for short-range wireless communication in each cluster. The network control server 4 receives the cluster information including the number of mobile bodies included in the cluster from the mobile body 1 of the cluster head, and uses the cluster information so that the number of mobile bodies 1 for each channel is equalized. Assign a channel to each cluster. Note that to be uniform means to be more uniform. Therefore, it may not be completely uniform. The network control server 4 transmits information indicating the allocated channel to the corresponding cluster head mobile 1. For example, when the number of usable channels is 10 and there are 20 clusters including the same number of mobile units 1, the network control server 4 determines that the number of mobile units 1 using each channel is the same. One channel may be allocated for every two clusters so as to be more uniform. When the cluster information includes the current position of the cluster head, the network control server 4 may assign a different channel to the adjacent cluster using the current position. By doing so, it is possible to avoid interference of short-range wireless communication between adjacent clusters. Further, the network control server 4 may transmit, for example, a signal indicating the timing for starting the cluster configuration to each mobile unit 1 by broadcast.

  The network control server 4 may transmit an instruction to divide the cluster to the cluster head when the number of the mobile units 1 included in one cluster is large. The case where the number of moving bodies 1 included in one cluster is large may be a case where the number of moving bodies 1 included in the cluster exceeds a threshold value. The threshold value may be determined in advance and held in the network control server 4, for example. When the network control server 4 instructs to divide a certain cluster, the network control server 4 may designate, for example, the mobile object 1 to be divided and the mobile object 1 that will be a new cluster head in the mobile object 1 to be divided, or It is not necessary to specify. In the present embodiment, the latter case, that is, the case where the moving body 1 or a new cluster head belonging to the cluster to be divided is selected on the cluster side will be mainly described.

  In the present embodiment, the case where the information server 3 and the network control server 4 are separate servers will be described, but both may be configured as one server.

  The LTE base station 5 may be a base station used in cellular communication. The access points 6 and 7 may be base stations used for wireless LAN communication, for example. The LTE base station 5 and the access points 6 and 7 of the wireless LAN are already known and will not be described in detail.

  FIG. 2 is a block diagram showing a configuration of the moving body 1 according to the present embodiment. In FIG. 2, the moving body 1 according to the present embodiment moves autonomously, and includes a moving mechanism 11, a current position acquisition unit 12, a movement control unit 13, and an information acquisition device 2. The information acquisition device 2 is provided in the mobile body 1 and includes a wide area communication unit 21, a short-range communication unit 22, a determination unit 23, an information management unit 24, a storage unit 25, and a communication control unit 26. With. In addition, the mobile body 1 performs autonomous movement using the information acquired by the information acquisition device 2.

  The moving mechanism 11 moves the moving body 1, and any method can be used as long as the moving body 1 can be moved. The moving mechanism 11 may have, for example, a traveling unit such as a wheel or an endless track, and a driving unit such as a motor or an engine that drives the traveling unit. Since the moving mechanism 11 can use a known configuration, a detailed description thereof is omitted.

  The current position acquisition unit 12 acquires the current position of the moving body 1. Acquisition of the current position may be performed using, for example, wireless communication, or may be performed using other means that can acquire the current position. As a method of acquiring the current position using wireless communication, for example, a method of acquiring the current position by satellite positioning such as GPS (Global Positioning System) or a position measurement technique indoors, for example, positioning by wireless LAN or IMES ( There are known a method using indoor GPS positioning represented by Indoor Message System, a method using location information of the nearest wireless base station, and the like. The current position acquisition unit 12 may acquire the current position using, for example, an autonomous navigation device. Further, the current position acquisition unit 12 may acquire the current position including the direction (direction) of the moving body 1. The direction may be indicated by, for example, an azimuth angle measured clockwise with north as 0 degree, or may be indicated by other information indicating the direction. The orientation may be acquired by, for example, an electronic compass or a geomagnetic sensor.

  The movement control unit 13 controls the movement by the movement mechanism 11 using the current position acquired by the current position acquisition unit 12 and the information acquired by the information acquisition device 2. For example, the movement control unit 13 may acquire a route from the current position to the destination, and may control the movement of the moving body 1 to the destination using the acquired route. For example, when the moving body 1 has an obstacle detection unit such as a millimeter wave radar, the movement control unit 13 detects when the obstacle is detected by the obstacle detection unit. The movement by the moving mechanism 11 may be stopped, decelerated, or moved so as to avoid obstacles. Moreover, when the direction of the moving body 1 is also acquired by the current position acquisition unit 12, the movement control unit 13 may control the moving mechanism 11 so that the moving body 1 faces the traveling direction, for example. In addition, since control of the moving mechanism 11 by the above movement control parts 13 is already known, the detailed description is abbreviate | omitted.

  The wide area communication unit 21 performs wide area wireless communication. Wide-area wireless communication is, for example, cellular communication or wireless LAN communication as described above. The wide area communication unit 21 may or may not include a wireless communication device for performing communication. The wide area communication unit 21 may be realized by hardware, or may be realized by software such as a driver that drives a communication device.

  The short-range communication unit 22 performs short-range wireless communication and cluster head determination. Short-range wireless communication is wireless communication in a narrower range than wireless communication by the wide area communication unit 21. Therefore, normally, the transmission power of the wireless communication by the short-range communication unit 22 is smaller than the transmission power of the wireless communication by the wide area communication unit 21. As described above, the short-range wireless communication may be, for example, wireless LAN communication, Bluetooth (registered trademark) communication, or the like. Note that the short-range communication unit 22 may or may not include a wireless communication device for performing communication. The short-range communication unit 22 may be realized by hardware, or may be realized by software such as a driver that drives a communication device. As shown in FIG. 2, the short-range communication unit 22 includes an intra-cluster communication unit 31 and a beacon transmission unit 32.

  The intra-cluster communication unit 31 receives information transmitted from other mobile units 1, beacons, and the like. Further, the intra-cluster communication unit 31 transmits information to other mobile units 1. The wireless communication performed by the intra-cluster communication unit 31 is the short-range wireless communication described above.

  The beacon transmission unit 32 transmits a beacon. The beacon usually includes an identifier for identifying the mobile unit 1. The beacon is also transmitted by short-range wireless communication. The short-range wireless communication is as described above. Therefore, the beacon transmitted from the beacon transmission unit 32 is received by the mobile unit 1 existing near the mobile unit 1 having the beacon transmission unit 32 and is not received by the remote mobile unit 1. The beacon transmitted by the beacon transmission unit 32 may be considered as a signal transmitted by broadcast. In addition, the beacon may be referred to as a “Hello packet”. The beacon may include the latest current position acquired by the current position acquisition unit 12.

  In the case where both wide-area and short-range wireless communication are wireless LANs, the wide-area communication unit 21 and the short-range communication unit 22 may be configured integrally. Even in that case, when transmitting by wireless communication in a wide area, transmission is performed with higher power, and when transmitting by wireless communication at a short distance, transmission is performed with lower power. .

  The beacon may be received by a device other than the intra-cluster communication unit 31. Specifically, the short-range communication unit 22 includes an intra-cluster communication unit 31 that performs data communication with another mobile body 1, a beacon transmission unit 32, and a beacon reception unit (not shown) that receives a beacon. And may be provided. In that case, for example, the wireless channel used for data communication within the cluster and the wireless channel used for beacon transmission / reception can be made different, and transmission / reception of beacons affects data communication within the cluster. You can avoid giving.

  In addition, a channel used in wireless communication performed by the intra-cluster communication unit 31 for cluster construction or the like may be determined in advance. Further, as will be described later, after a channel used for information sharing within a cluster is set by the communication control unit 26, short-range wireless communication is performed using the set channel. Also good. Also for the beacon, the channel to be used may be determined in advance.

  The cluster head determination unit 33 defines a condition for determining that the mobile body is a cluster head, generates an integer type random number within a certain range as the condition, and the generated integer type random number is the same as the specified integer. In this case, the mobile body may be determined as the mobile body of the cluster head.

  The determination unit 23 determines whether the mobile body is a cluster head or a cluster member in a cluster composed of a plurality of mobile bodies 1 that are close to each other. The determination unit 23 may determine that the own mobile body is a cluster head when a condition for determining a cluster head by the cluster head determination unit 33 in the short-range communication unit 22 is satisfied. Here, the self-moving body is the moving body 1 including the information acquisition device 2 having the determination unit 23, and the other moving body is the moving body 1 other than the self-moving body. The same applies to the self-moving body and other moving bodies for other components. A certain mobile unit 1 being able to perform wireless communication with another mobile unit 1 may be capable of performing wireless communication with a predetermined quality or higher. Therefore, being able to perform wireless communication may mean that each mobile unit 1 can receive with a received power equal to or higher than a predetermined threshold. The received power may be, for example, a received signal strength indicator (RSSI). Normally, there is one cluster head moving body 1 in one cluster, and the other moving bodies 1 are cluster member moving bodies 1. The number of cluster members included in one cluster is usually two or more, but depending on circumstances, it may be one or zero. For example, when the moving member 1 of a cluster member belonging to a certain cluster is not a cluster member because it has moved away from the moving member 1 of the cluster head as described later, the moving member of one cluster head A cluster having only one is newly constructed. Similarly, when the mobile bodies 1 of several cluster members are separated from the cluster head and are no longer cluster members, the number of cluster members can be one or zero.

  More specifically, the determination of the cluster header and the cluster member may be performed as follows. When forming a cluster, the cluster head determining unit 33 of each mobile 1 generates an integer type random number within a certain range, for example, an integer type random number from 1 to 20, and the generated integer type random number is a specified value, for example, In the case of 20, the determination unit 23 may determine that the own moving body is a moving body of the cluster head. When the determination unit 23 determines that the mobile body is a cluster head mobile body, a cluster head declaration indicating that the mobile body is a cluster head is a short distance according to the determination result. May be transmitted to the surrounding mobile body 1 by wireless communication. The cluster head declaration may include an identifier of the moving body 1 of the cluster head. The cluster head declaration may be transmitted by the intra-cluster communication unit 31 or the beacon transmission unit 32, for example, by CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance). By performing such transmission, even if it is determined that the mobile body is a cluster head in two or more mobile bodies 1, one mobile body 1 in the mobile body 1 is the cluster. The head declaration will be sent first. In such a case, the mobile 1 that has transmitted the cluster head declaration first may become the cluster head. The beacon transmission by the beacon transmission unit 32 and the transmission by the intra-cluster communication unit 31 may be performed by CSMA / CA, and the wide area communication unit 21 is equivalent to CSMA / CA or by LBT (Listen Before Talk). It may be done.

  As a result, the determination unit 23 only needs to be able to determine whether the mobile body is a cluster head or a cluster member. Therefore, the determination unit 23 may or may not perform the determination process. In the latter case, by receiving information indicating which mobile body is the other mobile body 1, the determination unit 23 determines whether the mobile body is a cluster head or a cluster member. May be judged. For example, as will be described later, the determination unit 23 of the moving body 1 in the cluster to be divided determines whether the moving body is the cluster head or the moving body 1 of the cluster head before the division or the network control server 4 selects it. It may be determined that the member is a cluster member.

  When determining that the mobile unit is a cluster member, the determination unit 23 may transmit information indicating that the mobile unit is a cluster member to the mobile unit 1 of the cluster head. In this way, the determination unit 23 determines whether the mobile body is a cluster head or a cluster member, and further, between the mobile body 1 determined to be a cluster head and the mobile body 1 determined to be a cluster member. A cluster is configured by transmitting and receiving a cluster head declaration and information indicating a cluster member. One cluster includes a cluster head mobile body 1 that has transmitted a cluster head declaration, and a cluster member mobile body 1 that has transmitted information indicating that it is a cluster member to the cluster head mobile body 1. Will be.

  When the mobile unit is a cluster head, the information management unit 24 receives information from the information server 3 via the wide area communication unit 21 and stores it in the storage unit 25, and responds to a request from the mobile member 1 of the cluster member. In response, the information stored in the storage unit 25 is transmitted to the cluster member mobile 1 via the short-range communication unit 22. The information may be received from the information server 3 in response to a request for information transmission from the information management unit 24 to the information server 3. In addition, when the mobile unit is a cluster member, the information management unit 24 requests information managed by the information server 3 from the mobile unit 1 of the cluster head, and performs near field communication from the mobile unit 1 of the cluster head. Received via the unit 22. Information received in this manner may also be stored in the storage unit 25. It is preferable that the same information is used by a plurality of mobile bodies 1 existing in adjacent areas, that is, a plurality of mobile bodies 1 belonging to the same cluster, and the information is acquired from the information server 3. It will be. In this way, the information acquired from the information server 3 can be shared among the plurality of mobile objects 1 existing in the adjacent areas. The information may be map information, for example, as described above. Further, the communication with the cluster member mobile 1 via the short-range communication unit 22 may be performed by the intra-cluster communication unit 31 of the short-range communication unit 22. As the information managed by the information management unit 24 acquires the information managed by the information server 3 as described above, the mobile unit 1 that directly accesses the information server 3 is only the mobile unit 1 of the cluster head. The member moving body 1 acquires information from the cluster head moving body 1. Therefore, the acquisition of information is hierarchized, and the capacity of information transmitted and received in wide area wireless communication between the mobile 1 and the information server 3 can be reduced. As a result, radio resources are effectively used, and more mobile units 1 can be accommodated.

  In addition, since the information acquired from the information server 3 usually has a large capacity, as described above, it is preferable that the information is transmitted and received in the cluster via short-range wireless communication. On the other hand, since the request for information from the mobile member 1 of the cluster member to the mobile unit 1 of the cluster head has information that specifies the information to be requested, it is compared with the information acquired from the information server 3. And the capacity is small. Therefore, the request may be made by, for example, short-range wireless communication or may be made by wide-area wireless communication. Note that, from the viewpoint of reducing the amount of communication in wide-area wireless communication, it is preferable that transmission / reception of the request is also performed by short-range wireless communication.

  In the storage unit 25, information acquired by the information management unit 24, that is, information managed by the information server 3 is stored. The storage in the storage unit 25 may be temporary storage in a RAM or the like, or may be long-term storage. The storage unit 25 can be realized by a predetermined recording medium (for example, a semiconductor memory, a magnetic disk, an optical disk, etc.).

  When the mobile unit is a cluster head, the communication control unit 26 transmits cluster information including the number of mobile units 1 in the cluster to which the mobile unit belongs to the network control server 4 via the wide area communication unit 21. The communication control unit 26 may include the latest current position acquired by the current position acquisition unit 12 in the cluster information. Further, the communication control unit 26 receives a channel of wireless communication performed by the short-range communication unit 22 from the network control server 4 via the wide-area communication unit 21 in response to transmission of the cluster information. The wireless communication channel is a result of being assigned to each cluster in the network control server 4 so that the number of mobile bodies 1 for each channel is made uniform. When the current position is also included in the cluster information, the network control server 4 may assign a channel to each cluster so that different channels are assigned to adjacent clusters. The channel used for short-distance wireless communication received by the communication control unit 26 from the network control server 4 may be transmitted from the mobile unit 1 of the cluster head to the mobile unit 1 of the cluster member belonging to the same cluster. Then, the wireless communication by the short-range communication unit 22 between the mobile units 1 in the cluster to which the mobile unit 1 of the cluster head belongs is performed using the channel received from the network control server 4 by the communication control unit 26 of the cluster head. Is preferred. As described above, since the number of the mobile bodies 1 for each channel is made uniform in the information communication system as a whole, it is possible to avoid a situation where only short-range wireless communication in a specific cluster is congested.

  Here, a process of dividing a cluster into two or more clusters when the number of moving objects 1 in one cluster exceeds a threshold value will be described. In addition, it is preferable that the number of the moving bodies 1 in each cluster after the division is equal to or less than the threshold value. In addition, the number of moving bodies 1 in each cluster after the division may finally be equal to or less than the threshold value by repeating the division of the cluster twice or more.

  When the number of the moving bodies 1 in the cluster to which the own moving body belongs exceeds the threshold value and the own moving body is a cluster head, the determining unit 23 selects a new cluster selected from the cluster members. You may notify the moving body 1 of a head that it will become a cluster head. Whether or not the number of the moving bodies 1 in the cluster to which the own moving body belongs exceeds the threshold value may be determined by the determining unit 23, and according to the transmission of the cluster information by the communication control unit 26, the network control server 4 May be received from. The selection of a new cluster head mobile body 1 from the cluster member mobile body 1 may be performed, for example, by random selection. When the count number is received from each mobile body 1 as described above, It may be performed by selecting the moving body 1 having a large count number. After selecting the new cluster head, it is preferable that the determination unit 23 notifies the moving body 1 of the selected cluster head that it has become a new cluster head. At the time of the notification, information for identifying a new cluster member may or may not be notified together. In the former case, the determination unit 23 may select a new cluster member (that is, a cluster member that moves from the original cluster to the new cluster). The selection may be performed, for example, at random. When the current position is also received from each mobile unit 1 (for example, when the current position is also included in the beacon), the selection is close to the new cluster head. This may be done by selecting a cluster member that exists at the location. In addition, when information identifying a new cluster member is also received, the new cluster head notifies each cluster member identified by the received information that the mobile unit has become a cluster head. May be. In addition, when information for identifying a new cluster member is not notified to the new cluster head, for example, a new cluster member may be selected in the moving body 1 of the new cluster head, or Each cluster member belonging to the original cluster may decide whether to remain in the original cluster or move to a new cluster. When determining the cluster to which the mobile unit belongs in the mobile unit 1 of each cluster member, the mobile unit 1 of the cluster member, for example, receives received power of a beacon transmitted from the mobile unit 1 of the cluster head of the original cluster. And the cluster of the mobile unit 1 of the cluster head corresponding to the larger received power may be selected from the received power of the beacon transmitted from the mobile unit 1 of the cluster head of the new cluster. Further, when the determination unit 23 of the moving body 1 of the cluster head in the original cluster also selects a new cluster member, the determining unit 23 adds a new cluster member to the moving body 1 of the new cluster member. It may be notified that the user has become a cluster member or information for identifying the cluster head. Also, for example, when the determination unit 23 of the moving body 1 of the cluster head in the original cluster selects a new cluster head and a new cluster member, the determination unit 23 selects the selected cluster head. The new cluster head moving body 1 and the new cluster member moving body 1 include information for identifying the selected new cluster head moving body 1 and information for identifying the new cluster member moving body 1. You may send it. By doing so, each moving body 1 that belongs to the new cluster to be divided can specify the moving body 1 of the new cluster head and the moving body 1 of the new cluster member in the new cluster. It becomes like this.

  In addition, when the number of the mobile bodies 1 in the cluster to which the mobile body belongs exceeds a threshold value and the mobile body is a cluster member, the determination unit 23 determines whether the mobile body 1 of the cluster head When receiving a notification that the mobile unit will be a cluster head, the mobile unit determines that the mobile unit is a cluster head in the new cluster to which it is split and receives a notification that the mobile unit will be a cluster head. If not, it may be determined that the cluster member is an existing cluster head or a new cluster head. If the moving body does not become a new cluster head, whether it becomes a cluster member of the cluster before the division or a cluster member of the new cluster at the division destination may be determined by, for example, the existing cluster head May be determined by a new cluster head, may be determined by the mobile body, or may be determined by another device such as the network control server 4.

  When division is performed, the cluster head and cluster member in the new cluster may be selected by the cluster head of the original cluster as described above, or may be selected by the network control server 4 or the like. Good. Moreover, the position of each moving body 1 may be used in selecting them. When selecting the cluster head or cluster member of the cluster to be divided using the position, for example, the moving body 1 located near the center among the moving bodies 1 belonging to the cluster to be divided is set as the moving body of the cluster head. Other mobile bodies 1 may be the cluster member mobile bodies 1. Alternatively, the mobile body 1 belonging to the cluster to be divided may be selected using the position of each mobile body 1. In that case, the cluster of the division destination is such that the area where the moving body 1 that will remain in the cluster of the division source is separated from the area where the moving body 1 that belongs to the cluster of the division destination is as far as possible. The mobile body 1 belonging to may be selected.

  Next, operation | movement of the information acquisition apparatus 2 is demonstrated using the flowchart of FIGS. In the description using the flowcharts, it is assumed that the necessity of the division is determined by the network control server 4 and the mobile body 1 belonging to the cluster to be divided is selected by the mobile body 1 of the cluster head before the division.

  FIG. 3 is a flowchart showing the processing of the information acquisition apparatus 2 for determining whether each moving body 1 is a cluster head or a cluster member. FIG. 4 is a flowchart showing the processing of the information acquisition apparatus 2 regarding cluster division.

  First, referring to FIG. 3, the cluster head determination unit 33 determines whether or not to perform cluster head determination (step S101). If the cluster head determination is to be performed, the process proceeds to step S102. If not, the process of step S101 is repeated until it is determined that the cluster head determination is to be performed. The cluster head determination unit 33 determines that the cluster head determination is to be performed when the wide-area communication unit 21 receives a signal transmitted from the network control server 4 and indicating the timing for starting the cluster configuration. May be.

  (Step S <b> 102) The beacon transmission unit 32 periodically transmits a beacon via the beacon transmission unit 32 in order to confirm the number of other mobile units 1 existing in the vicinity.

  (Step S103) The cluster head determination unit 33 generates an integer type random number within a certain range. The result of whether or not the generated integer random number is a specified value is reported to the determination unit 23.

  (Step S104) From the result reported in step S103, the determination unit 23 proceeds to step S105 if the mobile unit 1 determines that it is a cluster head candidate, and if not, the mobile unit is a cluster member. The process proceeds to step S111.

  (Step S <b> 105) The determination unit 23 receives a beacon transmitted as a response from another mobile 1 existing in the vicinity of the beacon transmitted in Step S <b> 102. This reception may be performed through the intra-cluster communication unit 31, for example. Further, for example, the intra-cluster communication unit 31 may periodically transmit a beacon in step S102 and receive beacons from other mobile units 1 until a predetermined time T1 elapses. The received beacons are counted, and if the number of beacons is equal to or greater than a preset threshold value, it is determined that the own mobile body is a cluster head, and the process proceeds to step S106. The process proceeds to step S111 to determine whether is a cluster member. (Step S106) The determination unit 23 transmits a cluster head declaration that the mobile body is a cluster head. This transmission may be performed using, for example, a predetermined channel in short-distance wireless communication via the intra-cluster communication unit 31.

  (Step S <b> 107) The determination unit 23 sends the information indicating the cluster member transmitted from the mobile body 1 of each cluster member via the intra-cluster communication unit 31 in response to the transmission of the cluster head declaration in step S <b> 106. Receive. This reception may be performed until, for example, a predetermined time T3 (> T2) elapses after the beacon is transmitted in step S102. The time T2 will be described later.

  (Step S108) The communication control unit 26 transmits the cluster information to the network control server 4 via the wide area communication unit 21. Note that the cluster information may include, for example, the number of mobile objects 1 belonging to the cluster and the latest current position acquired by the current position acquisition unit 12. Note that the number of mobile bodies 1 belonging to the cluster is equal to, for example, “1” of the mobile body that is the cluster head in addition to the number of mobile bodies 1 that are the transmission source of the information received in step S107 (ie, the number of cluster members). "May be added. Further, as a result, it is only necessary for the network control server 4 to know the number of mobile units 1 included in the cluster, so the cluster information may include the number of cluster members belonging to the cluster. The cluster information may include, for example, the latest current position of the moving body 1.

  (Step S <b> 109) The communication control unit 26 receives from the network control server 4 a channel used for short-distance wireless communication and the necessity of division. When the network control server 4 determines that the division is necessary, the fact that the division is necessary and the channel used for the short-distance wireless communication in the cluster to which the division is made are the mobile unit of the cluster head. 1 may be transmitted.

  (Step S110) The communication control unit 26 transmits the channel received from the network control server 4 and used for short-distance wireless communication to each mobile unit 1 that is a cluster member. This transmission may be performed via the short-range communication unit 22. Further, the communication control unit 26 sets the channel received from the network control server 4 in the intra-cluster communication unit 31 as a channel used for short-range wireless communication. Then, the process proceeds to step S201 in the flowchart of FIG.

(Step S111) The determination unit 23 receives a cluster head declaration in order to determine whether or not it is a cluster member. This reception may be performed through the intra-cluster communication unit 31, for example. Further, this reception may be performed until a predetermined time T2 (> T1) elapses after the beacon is transmitted in step S102, for example.
If the cluster head declaration is not received after the predetermined time T2, the process proceeds to step S102 to determine again whether the cluster head or the cluster member, and the cluster head declaration is made within the predetermined time T2. If received, it is determined to be a cluster member and the process proceeds to step S112.

  (Step S112) The determination unit 23 determines whether two or more cluster head declarations have been received. If two or more cluster head declarations are received, the process proceeds to step S113. If not, the process proceeds to step S114.

  (Step S113) The determination unit 23 selects one mobile body 1 as the cluster head of the mobile body from among the two or more mobile bodies 1 that have transmitted the cluster head declaration. The determination unit 23 may select, for example, the mobile body 1 having the larger received power of the cluster head declaration as the cluster head.

  (Step S114) The determination unit 23 transmits information indicating that the mobile unit is a cluster member to the mobile unit 1 of the cluster head. The information may include, for example, an identifier of the own mobile body. Moreover, the transmission may be performed via the intra-cluster communication unit 31, for example.

(Step S115) The communication control unit 26 receives a channel used in short-distance wireless communication transmitted from the moving body 1 of the cluster head. Then, the communication control unit 26 sets the channel in the short-range communication unit 22 as a channel used for short-range wireless communication. The reception of the channel may be performed via the intra-cluster communication unit 31, for example. This reception may be performed until, for example, a predetermined time T4 (> T2) elapses after the beacon transmission in step S102. Then, the process proceeds to step S204 in FIG.

  (Step S <b> 201) The determination unit 23 of the mobile unit 1 of the cluster head determines whether or not the division is received from the network control server 4. If a message to divide is received, the process proceeds to step S202. If not, the process proceeds to step S301 in the flowchart of FIG.

  (Step S202) The determination unit 23 creates a new member belonging to the cluster to be divided from the moving member 1 of the cluster member that has transmitted the information received in step S107, that is, the moving member 1 of the cluster member belonging to the same cluster as the own moving member. A moving body 1 of a new cluster head and a moving body 1 of a new cluster member are selected.

  (Step S203) The determination unit 23 notifies each mobile unit 1 selected in Step S202 of the new cluster head of the cluster to be divided and the new cluster member. Specifically, the determination unit 23 may notify each mobile unit 1 to be selected of an identifier of a new cluster head and an identifier of a new cluster member. By this notification, each mobile body 1 that belongs to the cluster to be divided can know that it belongs to the new cluster and the mobile body 1 of the cluster head in the new cluster. These notifications may be performed via the intra-cluster communication unit 31. In addition, the notification may include a channel used in short-range wireless communication in the new cluster. The channel may be received from the network control server 4 in step S109, for example. Further, for example, when a channel used for short-range wireless communication in a new cluster is not received from the network control server 4 in step S109, the channel is moved to the mobile unit 1 of the cluster head before the division, Alternatively, the new cluster head mobile unit 1 may be acquired by inquiring of the network control server 4.

  (Step S <b> 204) The determination unit 23 of the cluster member moving body 1 determines whether a notification about a new cluster head or the like has been received from the cluster head moving body 1. If received, the process proceeds to step S205. If not received, the process proceeds to step S401 in the flowchart of FIG. The determination unit 23 of the moving body 1 that has received the notification determines that the moving body is a cluster head when the notification regarding the new cluster head or the like indicates that the moving body is a cluster head. When the notification regarding the new cluster head or the like indicates that the mobile body is a cluster member, the mobile body may be determined to be a cluster member. In this case, since the cluster head and the cluster member of the new cluster are specified by the notification, there is no need to transmit a cluster head declaration or information indicating that it is a cluster member. The cluster will be configured. If the notification from the cluster head includes a channel used in short-range wireless communication in the new cluster, the communication control unit 26 in each mobile unit 1 belonging to the new cluster As a channel used for short-range wireless communication, the short-range communication unit 22 is set. For example, the determination unit 23 may proceed to step S401 when the notification is not received by the time T5 (> T4) determined in advance after the beacon transmission in step S102.

  (Step S205) The determination unit 23 determines whether or not the own mobile body is a cluster head in the cluster at the division destination. If it is a cluster head, the process proceeds to step S301 in the flowchart of FIG. 5, and if it is a cluster member, the process proceeds to step S401 in the flowchart of FIG.

  FIG. 5 is a flowchart showing the processing of the information acquisition apparatus 2 in the moving body 1 that is a cluster head.

  (Step S301) The information management unit 24 of the mobile 1 that is a cluster head determines whether information managed by the information server 3 is necessary. And when the information is required, it progresses to step S302, and when that is not right, it progresses to step S303. For example, when the map information necessary for the movement control is not stored in the storage unit 25, the movement control unit 13 stores the map information corresponding to the latest current position acquired by the current position acquisition unit 12. You may request | require to the management part 24. FIG. For example, when there is a request for information managed by the information server 3 from the movement control unit 13, the information management unit 24 may determine that the information is necessary.

  (Step S302) The information management unit 24 acquires the requested information from the information server 3. Specifically, the information management unit 24 may transmit a request for the information to the information server 3, and may receive the requested information transmitted from the information server 3 in response to the transmission. Transmission of the request and reception of information are performed via the wide area communication unit 21. And the information management part 24 accumulate | stores the acquired information in the memory | storage part 25, passes it to the movement control part 13, and returns to step S301.

  (Step S303) The information management unit 24 determines whether or not a request for transmission of information managed by the information server 3 has been received from the mobile member 1 of the cluster member belonging to the same cluster. If the request is received, the process proceeds to step S304. If not, the process proceeds to step S307. The reception may be performed via the intra-cluster communication unit 31, for example.

  (Step S304) The information management unit 24 determines whether the information requested in step S303 is stored in the storage unit 25. If it is stored, the process proceeds to step S306. If not, the process proceeds to step S305.

  (Step S305) The information management unit 24 acquires the information to be requested from the information server 3 in the same manner as in step S302, and accumulates the information in the storage unit 25.

  (Step S306) The information management unit 24 transmits the information to be requested to the mobile member 1 of the cluster member that is the request source via the intra-cluster communication unit 31. Then, the process returns to step S301.

  (Step S307) The beacon transmission unit 32 determines whether it is time to transmit a beacon. If it is time to transmit a beacon, the process proceeds to step S308; otherwise, the process proceeds to step S309. Note that the beacon transmission unit 32 may periodically determine to transmit a beacon, for example. This beacon is used, for example, to determine whether the mobile member 1 of the cluster member can receive information from the cluster header. The cluster member mobile 1 that can no longer receive the beacon may acquire information managed by the information server 3 directly from the information server 3, for example.

  (Step S308) The beacon transmission unit 32 transmits a beacon. Then, the process returns to step S301.

  (Step S309) The information management unit 24 determines whether to perform cluster head determination. If the cluster head determination is to be performed, the process returns to step S102; otherwise, the process returns to step S301. For example, the information management unit 24 determines that the cluster head determination is performed when the wide-area communication unit 21 receives a signal transmitted from the network control server 4 and indicating the timing for starting the cluster configuration. Also good.

  In the flowchart of FIG. 5, a case is shown in which the process returns to step S <b> 102 when it is determined that cluster head determination is to be performed, but this need not be the case. If it is determined that the cluster head determination is to be performed, the process of forming a cluster after step S102 and the process of acquiring information in steps S301 to S306 may be executed in parallel. This is because even when a cluster is configured, it is necessary to consider the case where new information is required.

  FIG. 6 is a flowchart showing the processing of the information acquisition apparatus 2 in the mobile 1 that is a cluster member. The mobile body 1 that is a cluster member is the mobile body 1 that is determined to be a cluster member when the cluster is configured. This is because, as will be described later, when the cluster is configured, the moving body 1 that was a cluster member may become a cluster member later.

  (Step S401) The information management unit 24 of the moving body 1 determines whether information managed by the information server 3 is necessary. And when the information is required, it progresses to step S402, and when that is not right, it progresses to step S405. For example, when the map information necessary for the movement control is not stored in the storage unit 25, the movement control unit 13 stores the map information corresponding to the latest current position acquired by the current position acquisition unit 12. You may request | require to the management part 24. FIG. For example, when there is a request for information managed by the information server 3 from the movement control unit 13, the information management unit 24 may determine that the information is necessary.

  (Step S402) The determination unit 23 determines whether the mobile body is a cluster member. If it is a cluster member, the process proceeds to step S403. If it is not a cluster member, that is, if it is determined in step S408 that it is no longer a cluster member, the process proceeds to step S404.

  (Step S403) The information management unit 24 acquires the requested information from the moving body 1 of the cluster head. Specifically, the information management unit 24 transmits the request for the information to the mobile unit 1 of the cluster head, and receives the request target information transmitted from the mobile unit 1 of the cluster head in response to the transmission. Also good. The information is received via the intra-cluster communication unit 31. And the information management part 24 accumulate | stores the acquired information in the memory | storage part 25, passes it to the movement control part 13, and returns to step S401.

  (Step S404) The information management unit 24 acquires the requested information from the information server 3. Specifically, the information management unit 24 may transmit a request for the information to the information server 3, and may receive the requested information transmitted from the information server 3 in response to the transmission. Transmission of the request and reception of information are performed via the wide area communication unit 21. And the information management part 24 accumulate | stores the acquired information in the memory | storage part 25, passes it to the movement control part 13, and returns to step S401.

  (Step S405) The determination unit 23 determines whether a beacon transmitted from the moving body 1 of the cluster head has been received. The reception may be performed through the intra-cluster communication unit 31, for example. If a beacon is received, the process proceeds to step S406. If not, the process proceeds to step S407. In addition, receiving a beacon may be receiving a beacon having a predetermined reception power or higher. Whether the beacon is transmitted from the cluster head may be determined using, for example, the identifier of the mobile unit 1 included in the beacon.

  (Step S406) The determination unit 23 acquires and records the time when the beacon is received from a clock unit (not shown). The recording may be performed by accumulation in a recording medium (not shown). Then, the process returns to step S401.

  (Step S407) The determination unit 23 determines whether a beacon is periodically received from the moving body 1 of the cluster head. For example, when the period from the time when the beacon was last received, that is, the latest time recorded in step S406 to the time of the determination exceeds a predetermined threshold, the determination unit 23 periodically It may be determined that a beacon has not been received, and if the period has not exceeded the threshold, it may be determined that a beacon has been received periodically. If a beacon is periodically received, the process proceeds to step S409. If not, the process proceeds to step S408. It is preferable that the threshold used for the determination is set longer than the beacon transmission interval.

  (Step S408) The determination unit 23 determines that the mobile body is not a cluster member. This is because the mobile unit is present at a position where the beacon transmitted from the mobile unit 1 of the cluster head cannot be received, and thus information cannot be acquired from the mobile unit 1 of the cluster head.

  (Step S409) The beacon transmission unit 32 determines whether to perform cluster head determination. If the cluster head determination is to be performed, the process returns to step S102; otherwise, the process returns to step S401. The beacon transmission unit 32 determines that the cluster head determination is to be performed when the wide-area communication unit 21 receives a signal transmitted from the network control server 4 and indicating the timing for starting the cluster configuration, for example. Also good.

  In the flowchart of FIG. 6, a case is shown in which the process returns to step S <b> 102 when it is determined that cluster head determination is to be performed. When it is determined that the cluster head determination is to be performed, the process of forming a cluster after step S102 and the process of acquiring information in steps S401 to S404 may be executed in parallel. This is because new information may be required even when the cluster is configured.

  Moreover, the order of the processes in the flowcharts of FIGS. 3 to 6 is an example, and the order of the steps may be changed as long as the same result can be obtained. Also, in the flowcharts of FIGS. 3 to 6, the processing is ended by powering off or interruption of processing end.

  Although not shown in the flowcharts of FIGS. 3 to 6, the moving body 1 may move autonomously by the movement control unit 13. The movement operation is well known, and its description is omitted.

  7-9 is a figure which shows an example of arrangement | positioning of the mobile body in embodiment.

  Next, with reference to FIGS. 7 to 9, the operation of the moving body 1 according to the present embodiment will be described using a specific example. In this specific example, it is assumed that there are 22 moving bodies 1-1 to 1-22. In addition, when not distinguishing each of the mobile bodies 1-1 to 1-22, it may be called the mobile body 1. In this specific example, it is assumed that wide-area wireless communication and short-range wireless communication are wireless LAN communications. However, as described above, it is assumed that the transmission power of wide-area wireless communication is larger than the transmission power of short-range wireless communication. Also, control-related signals such as beacons and cluster head declarations transmitted / received between the mobile bodies 1 are transmitted / received using a predetermined channel.

At a certain timing, when an instruction from the network control server 4 to execute the cluster head determination is broadcast to each of the mobile units 1-1 to 1-22 shown in FIG. The head determination unit 33 determines that it is time to execute the cluster head determination (step S101). And the beacon transmission part 32 of each mobile body 1 transmits a beacon regularly in order to confirm the number of the other mobile bodies 1 which exist in the vicinity (step S102). Thereafter, the cluster head determination unit 33 of each mobile 1 generates an integer type random number within a certain range, and reports the result of whether or not the generated integer type random number is a prescribed value to the determination unit 23 (step S103).
Then, each determination unit 23 of the moving objects 1-3, 1-15, and 1-22 determines that the own moving object 1 is a cluster head candidate when the generated integer random number is a specified value. (Step 104), the number of other mobiles 1 present in the vicinity is counted as cluster head determination processing to determine whether or not the threshold value is exceeded (Step 105). Since the generated integer random number is not a prescribed value, the mobile unit 1 executes processing for determining that it is a cluster member. (Step S111).

  Among the moving bodies 1-3, 1-15, and 1-22, it is assumed that the moving bodies 1-3 and 1-15 have the other moving bodies 1 in the vicinity in the cluster head determination process having a threshold value or more . (Step 105). Then, the determination unit 23 of the moving body 1-15 transmits a cluster head declaration via the intra-cluster communication unit 31 (step S106). The cluster head declaration is received by the intra-cluster communication unit 31 of the 13 mobile units 1 (step S111). Similarly, the determination unit 23 of the moving body 1-3 also transmits a cluster head declaration via the intra-cluster communication unit 31 (step S106). The cluster head declaration is received by the intra-cluster communication unit 31 of the nine mobiles 1 (step S111). In addition, it is assumed that another mobile body 1 present in the vicinity in the cluster head determination process performed by the mobile body 1-22 is less than the threshold value (step 105). Then, a process for determining that the mobile body is a cluster member is executed. (Step S111) It is assumed that the mobile units 1-7 and 1-10 have received both cluster head declarations (Step S112). Then, the determination unit 23 of the mobile unit 1-7 selects the mobile unit 1-3 having the larger RSSI of the cluster head declaration as the cluster head, and the determination unit 23 of the mobile unit 1-10 determines the RSSI of the cluster head declaration. It is assumed that the moving body 1-15 having a larger is selected as the cluster head (step S113). Then, the determination unit 23 of the mobile unit 1-7 transmits information indicating that the mobile unit is a cluster member to the mobile unit 1-3 via the intra-cluster communication unit 31. In addition, the determination unit 23 of the mobile unit 1-10 transmits information indicating that the mobile unit is a cluster member to the mobile unit 1-15 via the intra-cluster communication unit 31. The other mobile units 1-1 and the like also transmit information indicating that the mobile unit is a cluster member to the mobile units 1-3 and 1-15 of the cluster head that is the transmission source of the cluster head declaration. (Step S114). Each determination unit 23 of the mobile bodies 1-3 and 1-15 can know the mobile body 1 included in the cluster to which the mobile body belongs by receiving such information (step S107). In this case, as shown in FIG. 8, a cluster A having the moving body 1-3 as the cluster head and a cluster B having the moving body 1-15 as the cluster head are configured.

  The decision units 23 of the cluster head moving bodies 1-3 and 1-15 pass the number of moving bodies 1 included in the respective clusters A and B to the communication control section 26. The number of moving bodies is the number obtained by adding 1 to the number of cluster members. Upon receiving the number of mobile objects 1 included in the cluster, the communication control unit 26 acquires the latest current position from the current position acquisition unit 12, and includes the current position and the number of mobile objects 1 included in the cluster. The cluster information is transmitted to the network control server 4 via the wide area communication unit 21 (step S108).

  The network control server 4 receives the cluster information from the mobile units 1-3 and 1-15 of the cluster head, and uses the cluster information to determine whether or not to divide the mobile unit 1 in each cluster. The channels of each cluster are determined so that the number is made uniform and the channels used in wireless communication of adjacent clusters are different. In this case, it is assumed that the division is determined to be necessary when the number of the moving bodies 1 in the cluster is 20 or more. Then, the network control server 4 determines that the division is unnecessary, and since there are only two clusters, it is assumed that channel 1 is assigned to cluster A and channel 6 is assigned to cluster B. Then, the network control server 4 transmits to the cluster head moving body 1-3 that the division is unnecessary and that the channel 1 is used for wireless communication within the cluster. Further, the network control server 4 transmits to the cluster head moving body 1-15 that the division is unnecessary and that the channel 6 is used for wireless communication within the cluster. Such information is received by the communication control unit 26 via the wide-area communication unit 21 of the mobile units 1-3 and 1-15 (step S109). Then, the communication control unit 26 notifies each mobile unit 1 in the cluster of the channel used for wireless communication within the cluster via the intra-cluster communication unit 31 and uses the channel for wireless communication within the cluster. The channel is set in the intra-cluster communication unit 31 (step S110). In addition, the communication control unit 26 of each mobile member 1 of the cluster member receives the channel transmitted from the cluster head via the intra-cluster communication unit 31, and uses the channel as a channel used for intra-cluster communication. The communication unit 31 is set (step S115). As described above, since the network control server 4 determines that the division is unnecessary, the division process is not performed (steps S201 and S204).

  The subsequent acquisition of information by each mobile 1 will be described using cluster A. Assume that the moving body 1-3, which is the cluster head of the cluster A, has moved to a new position and new map information is required. Then, it is assumed that the fact and the latest current position are transferred from the movement control unit 13 to the information management unit 24. Then, the information management unit 24 determines that it is necessary to acquire map information (step S301), and requests the information server 3 for map information corresponding to the latest current position. The request is made via the wide area communication unit 21. When receiving the request, the information server 3 reads the map information corresponding to the current position included in the request, and transmits the read map information to the mobile body 1-3 that is the transmission source of the request. Then, the map information is received by the information management unit 24 of the moving body 1-3 via the wide area communication unit 21, stored in the storage unit 25, and passed to the movement control unit 13 (step S302). As a result, the moving body 1-3 can perform autonomous movement using the acquired map information. When the map information is accumulated in the storage unit 25, it may be accumulated in association with information indicating the area of the map information.

  Thereafter, it is assumed that the moving object 1-1, which is a cluster member of the cluster A, moves to a new position, and new map information is required. Then, the information management unit 24 of the moving object 1-1 determines that it is necessary to acquire map information (step S401). And the information management part 24 inquires the judgment part 23 whether the mobile body 1-1 is a cluster member now. In this case, it is assumed that the user is a cluster member. Then, the information management unit 24 receives from the determination unit 23 that it is a cluster member (step S402), and obtains the map information corresponding to the latest current position via the intra-cluster communication unit 31. 3 is requested. When receiving the request, the information management unit 24 of the moving body 1-3 determines whether the map information corresponding to the request is stored in the storage unit 25 (steps S303 and S304). In this case, it is assumed that it was not included. Then, the information management unit 24 of the mobile body 1-3 acquires the map information from the information server 3, accumulates it in the storage unit 25, and transmits it to the mobile body 1-1 (steps S305 and S306). The map information transmitted from the mobile unit 1-3 is received by the information management unit 24 of the mobile unit 1-1 via the intra-cluster communication unit 31 and accumulated in the storage unit 25, and is also stored in the movement control unit 13. (Step S403). And in the moving body 1-1, it becomes possible to perform the autonomous movement using the acquired map information. Here, a case has been described in which the mobile body 1-3, which is the cluster head, acquires and transmits map information from the information server 3 in response to a request from the cluster member. If the map information is held in 1-3, the held map information is transmitted to the mobile body 1-1. In this way, since the acquisition of information is hierarchized, the frequency with which wide-area wireless communication is used is reduced, so that more mobiles 1 can be accommodated without increasing wireless resources. Become.

  Further, it is assumed that the beacon from the moving body 1-3 of the cluster head cannot be received with an RSSI equal to or higher than a predetermined threshold because the moving body 1-1 continues autonomous movement (step S405). ). Then, the recording of the time according to reception of the beacon is not performed. Then, the determination unit 23 of the mobile object 1-1 determines that the beacon is not received at a certain time (step S407), and determines that the mobile object 1-1 is no longer a cluster member of the cluster A (step S407). S408). Thereafter, when new map information is required, the moving object 1-1 acquires directly from the information server 3 (steps S401, S402, S404).

  Further, when an instruction to perform the cluster head determination is broadcast from the network control server 4 to each mobile unit 1-1 to 1-22 shown in FIG. 7 at a certain timing, The cluster construction by each moving body 1 is performed again. As described above, by repeatedly performing the cluster configuration, even if each mobile body 1 moves in various directions, an optimal cluster is formed at that time. Therefore, an adaptive hierarchical network (cluster) according to the position of the mobile body 1 that moves autonomously is configured.

  In the above description, the case where it is determined that the clusters A and B are not required to be divided has been described. Here, a specific example in the case where it is determined that the cluster B needs to be divided will be described. For example, in a situation where it is determined that the division is necessary when the number of the moving bodies 1 in the cluster is 10 or more, it is determined that the division is necessary for the cluster B.

  Assume that the network control server 4 transmits to the cluster head moving body 1-15 the fact that the cluster is to be divided, the channel 6 used in the cluster B as the dividing source, and the channel 11 used in the cluster as the dividing destination. When receiving the information from the network control server 4 (step S109), the communication control unit 26 of the moving body 1-15 that is the cluster head of the cluster B receives the information in each cluster before the division through the intra-cluster communication unit 31. Is notified of the channel “6” used for wireless communication within the cluster, and the channel is set in the intra-cluster communication unit 31 as a channel used for wireless communication within the cluster (step S110). In addition, since the determination unit 23 of the mobile unit 1-15 that is a cluster head has received that the division is necessary by the communication control unit 26, the mobile unit 1 of 12 cluster members moves from six mobile units that are halves. The bodies 1-12, 1-14, 1-17, 1-19, 1-20, 1-21 are selected at random, and one of the mobile bodies 1-21 is used as the cluster head, and the remaining 5 The mobile bodies 1-12, 1-14, 1-17, 1-19, and 1-20 are set as cluster members (step S202). Then, the determination unit 23 of the mobile body 1-15 indicates that the mobile body 1-21 is selected as the cluster head for the six mobile bodies 1, and the mobile bodies 1-12, 1-14, 1 It is notified that -17, 1-19, and 1-20 have been selected as cluster members, and that the channel used for short-distance wireless communication in the cluster at the division destination is “11” (step S203). The notifications are respectively received by the determination units 23 of the six mobile bodies 1 (step S204), and the determination section 23 of the mobile body 1-21 becomes a cluster head in the new cluster to which the mobile body is divided. In addition, the determination unit 23 of the moving object 1-12, 1-14, 1-17, 1-19, 1-20 determines that the own moving object has become a cluster member in the new cluster to be divided. Judgment is made (step S205). In addition, the determination unit 23 such as the mobile unit 1-12 passes the received channel “11” in the cluster at the division destination to the communication control unit 26. Then, the communication control unit 26 such as the six mobile units 1-12 sets the channel “11” in the intra-cluster communication unit 31 as a channel used in short-range wireless communication. Then, as indicated by the broken line in FIG. 9, the moving objects 1-12, 1-14, 1-17, 1-19, 1-20 do not belong to the cluster B, and form a new cluster. become. In this way, when the number of moving bodies 1 included in a certain cluster is large, the number of moving bodies 1 between the clusters is averaged.

  As described above, according to the moving body 1 according to the present embodiment, information is acquired from the information server 3 by the cluster head moving body 1 in each cluster, and the cluster member moving body 1 moves the cluster head. Information managed by the information server 3 is acquired from the body 1. In addition, since the mobile units 1 included in one cluster exist at close positions, information can be transmitted and received between the mobile units 1 by short-range wireless communication with a small transmission power. Thus, since the mobile body 1 that directly accesses the information server 3 is only the cluster head, the number of mobile bodies 1 that perform wide-area wireless communication is reduced, and the frequency of wide-area wireless communication is reduced. can do. In addition, since short-range wireless communication is performed with smaller transmission power, the range in which interference occurs is narrowed, and the number of mobile bodies 1 that can simultaneously perform short-range wireless communication within the same area is increased. be able to. Therefore, radio resources can be used efficiently, and more mobile units 1 can be used in an information communication system than in the case where each mobile unit acquires information from the information server 3 as in the prior art. Can be accommodated. As a result, for example, the situation in which the mobile body 1 cannot access the information managed by the information server 3 and the autonomous movement by the mobile body 1 is temporarily stopped can be avoided. .

  In addition, by making the number of moving bodies 1 in one cluster equal to or less than a threshold value, it is possible to prevent a situation in which only a short-range wireless communication load in a specific cluster increases. Can do. Further, the network control server 4 determines a channel to be used for short-range wireless communication in each cluster, whereby the load on each wireless channel can be smoothed. In particular, by determining the channel according to the position of the cluster, different channels can be used in adjacent clusters, and interference of short-range wireless communication can be prevented.

  In the present embodiment, an integer type random number within a certain range, for example, if each mobile unit 1 counts the number of beacons received from other mobile units existing in the vicinity and if it is 10, an integer type random number from 1 to 10 is used. If the generated integer type random number is the same value as the value specified by the integer type random number (for example, 7 etc.) from 1 to 10, for example, the case where it is determined as the cluster head has been described. Not necessarily. For example, a decimal random number in a certain range, for example, a decimal random number from 0 to 1, is generated, and a certain threshold value, for example, each mobile unit 1 counts the number of beacons received from other mobile units existing in the vicinity. It may be set corresponding to the number of received beacons, such as 0.1 for 1 and 0.2 for 2 and may be a cluster head if it is equal to or less than the set threshold. Thus, there are various methods for determining the cluster head.

  Moreover, although this embodiment demonstrated the case where the near field communication part 22 was provided with the intra-cluster communication part 31, the beacon transmission part 32, and the cluster head determination part 33, it may not be so. The short-range communication unit 22 may include an intra-cluster communication unit 31 and a cluster head determination unit 33. In that case, the intra-cluster communication unit 31 may also transmit a signal similar to the beacon. For example, when the intra-cluster communication unit 31 performs communication by wireless LAN, transmission of a broadcast with a predetermined transmission power may be transmission of a beacon.

  Further, when configuring a cluster, there may be a moving body 1 that cannot receive a cluster head declaration with a predetermined reception power or more. That is, there may be a mobile body 1 that does not belong to any cluster at the time when the process of constructing the cluster is completed. In that case, the process of constructing a cluster may be performed again only with the mobile 1 that does not belong to any cluster. As described above, it is considered that the number of mobile objects 1 that do not belong to any cluster is reduced by performing the process of constructing the cluster twice or more.

  In the above embodiment, the information exchange between the components is performed by one component when, for example, the two components that exchange the information are physically different from each other. It may be performed by outputting information and receiving information by the other component, or when two components that exchange information are physically the same, one component May be performed by moving from the phase of the process corresponding to to the phase of the process corresponding to the other component.

  In the above embodiment, information related to processing executed by each component, for example, information received, acquired, selected, generated, transmitted, or received by each component In addition, information such as threshold values, mathematical formulas, addresses, and the like used by each component in processing may be temporarily or for a long time held in a recording medium (not shown) even if not specified in the above description. Good. Further, the storage of information on the recording medium (not shown) may be performed by each component or a storage unit (not shown). Further, reading of information from the recording medium (not shown) may be performed by each component or a reading unit (not shown).

  In the above embodiment, information used by each component, for example, an integer type random number within a certain range used by each component for processing, an integer / threshold value / address to be determined as a cluster head, and various set values If the information may be changed by the user, the information may be appropriately changed by the user even if it is not specified in the above description, or not. If the information can be changed by the user, the change is realized by, for example, a not-shown receiving unit that receives a change instruction from the user and a changing unit (not shown) that changes the information in accordance with the change instruction. May be. The change instruction received by the receiving unit (not shown) may be received from an input device, information received via a communication line, or information read from a predetermined recording medium, for example. .

  In the above embodiment, when two or more components included in the mobile object 1 or the information acquisition apparatus 2 include a communication device, an input device, etc., the two or more components are physically single devices. You may have, or you may have a separate device.

  In the above-described embodiment, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component can be realized by a program execution unit such as an MPU (Micro Processing Unit) reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. At the time of execution, the program execution unit may execute the program while accessing the storage unit or the recording medium. The software that realizes the information acquisition apparatus in the above embodiment is the following program. That is, this program causes a computer to function as an information acquisition device provided on a mobile body that moves autonomously, and in a cluster composed of a plurality of mobile bodies that are close to each other, the mobile body is a cluster head. If the mobile unit is a cluster head, it receives and stores information from the information server via a wide area communication unit that performs wide area wireless communication, and determines whether the cluster member is a cluster member. In response to a request from the mobile unit, the stored information is transmitted to the mobile unit of the cluster member via the short-range communication unit that performs wireless communication in a narrower range than the wireless communication by the wide-area communication unit. Is a cluster member, requests information managed by the information server from the mobile unit of the cluster head, and passes the short-range communication unit from the mobile unit of the cluster head. Is a program for functioning as an information management unit which receives Te.

  In the program, the functions realized by the program do not include functions that can be realized only by hardware. For example, functions that can be realized only by hardware such as a modem and an interface card in an acquisition unit that acquires information and a communication unit that performs information communication are not included in at least the functions realized by the program.

  Further, this program may be executed by being downloaded from a server or the like, and a program recorded on a predetermined recording medium (for example, an optical disk such as a CD-ROM, a magnetic disk, a semiconductor memory, or the like) is read out. May be executed by Further, this program may be used as a program constituting a program product.

  Further, the computer that executes this program may be singular or plural. That is, centralized processing may be performed, or distributed processing may be performed.

  FIG. 10 is a diagram illustrating an example of a computer system 900 that executes the program and realizes the information acquisition apparatus 2 according to the embodiment. The above-described embodiment can be realized by computer hardware and a computer program executed on the computer hardware.

  In FIG. 10, a computer system 900 is connected to an MPU (Micro Processing Unit) 911, a ROM 912 such as a flash memory in which a program such as a bootup program, an application program, a system program, and data are stored, and an MPU 911. A RAM 913 that temporarily stores application program instructions and provides a temporary storage space, a touch panel 914, a wireless communication module 915, and a bus 916 that interconnects the MPU 911, the ROM 912, and the like are provided. Further, instead of the touch panel 914, a display and an input device such as a mouse or a keyboard may be provided. Further, the computer system 900 does not have to include the touch panel 914 when the input from the user or the display to the user is not performed.

  A program that causes the computer system 900 to execute the function of the information acquisition device 2 according to the above-described embodiment may be stored in the ROM 912 via the wireless communication module 915. The program is loaded into the RAM 913 when executed. Note that the program may be loaded directly from the network.

The program does not necessarily include an operating system (OS) or a third-party program that causes the computer system 900 to execute the function of the information acquisition device 2 according to the above-described embodiment. The program may include only a part of an instruction that calls an appropriate function or module in a controlled manner and obtains a desired result. How the computer system 900 operates is well known and will not be described in detail.

    Embodiment disclosed this time is an illustration of the structure for implementing this invention concretely, Comprising: The technical scope of this invention is not restrict | limited. The technical scope of the present invention is shown not by the description of the embodiment but by the scope of the claims, and includes modifications within the wording and equivalent meanings of the scope of the claims. Is intended.

  As described above, according to the information acquisition apparatus and the like according to the present invention, an effect that radio resources can be effectively used is obtained.

DESCRIPTION OF SYMBOLS 1 Mobile body 2 Information acquisition apparatus 3 Information server 4 Network control server 21 Wide area communication part 22 Near field communication part 23 Judgment part 24 Information management part 25 Storage part 26 Communication control part 31 Intracluster communication part 32 Beacon transmission part 33 Cluster head determination 900 Computer system 911 MPU (Micro Processing Unit)
912 ROM (Read Only Memory)
913 RAM (Random Access Memory)
914 Touch panel 915 Wireless communication module 916 System bus for mutually connecting 911 to 915

Claims (9)

An information acquisition device provided in a mobile body that moves autonomously,
A wide-area communication unit that performs wide-area wireless communication;
A short-range communication unit that performs wireless communication in a narrower range than wireless communication by the wide-area communication unit;
In a cluster composed of a plurality of mobile bodies that are close to each other, a cluster head inside the short-range communication unit that determines conditions necessary to determine whether the mobile body is a cluster head or a cluster member A determination unit;
A determination unit for determining whether the mobile body is a cluster head or a cluster member based on the condition determination result provided from the cluster head determination unit;
When the own mobile body is a cluster head, it receives and stores information from the information server via the wide area communication unit, and in response to a request from the mobile body of the cluster member, the stored information is When the mobile body is a cluster member, the information is managed by the cluster head mobile body when the mobile body is a cluster member. An information management unit comprising: an information management unit that receives the information from a mobile body via the short-range communication unit.   In the first half of the cluster head determination unit, a random number within a certain range is generated according to the number of other mobile units that can communicate with each other in the vicinity of the own mobile unit, and if the specified random number is within a certain range, the own mobile unit is the cluster head The information acquisition apparatus according to claim 1, wherein   The information acquisition apparatus according to claim 1, wherein the number of moving bodies in one cluster is equal to or less than a threshold value.   The cluster is divided so that the number of moving objects in one cluster is equal to or less than the threshold value when the number of moving objects in one cluster exceeds the threshold value. Or the information acquisition apparatus of Claim 3.   When the number of moving bodies in the cluster to which the moving body belongs exceeds the threshold value and the moving body is a cluster head, the determination unit determines a new cluster head selected from the cluster members. If the mobile body is notified that it is a cluster head and the number of mobile bodies in the cluster to which the mobile body belongs exceeds the threshold value, and the mobile body is a cluster member, the cluster head When a notification indicating that the mobile unit becomes a cluster head is received from the mobile unit, it is determined that the mobile unit is a cluster head, and a notification that the mobile unit is a cluster head has not been received. 5. The information acquisition apparatus according to claim 4, wherein the information acquisition apparatus determines that the cluster member is an existing cluster head or a cluster member of a new cluster head. When the mobile unit is a cluster head, the number of mobile units in the cluster to which the mobile unit belongs is transmitted to the network control server via the wide area communication unit, and the network control server A communication control unit that receives a channel of wireless communication performed by the short-range communication unit, which is assigned to each cluster so that the number is equalized, from the network control server via the wide-area communication unit;
The wireless communication by the short-range communication unit between each mobile unit in a cluster to which the cluster head mobile unit belongs is performed using a channel received by the communication control unit of the cluster head from the network control server. Item 6. The information acquisition device according to any one of Items 5 to 6. The information acquisition device according to any one of claims 1 to 6, comprising:
A moving body that autonomously moves using information acquired by the information acquisition device. An information acquisition method for a mobile object that moves autonomously,
A cluster head determination step of determining a condition necessary for determining whether the mobile body is a cluster head or a cluster member in a cluster composed of a plurality of mobile bodies close to each other by near field communication; ,
A determination step of determining whether the mobile body is a cluster head or a cluster member based on the condition determination result provided by the cluster head determination step;
When the mobile unit is a cluster head, information is received and stored from the information server via wide-area communication, which is wide-area wireless communication, and is stored in response to a request from the mobile member of the cluster member. Information that is managed by the information server when the information is transmitted to the mobile member of the cluster member via short-range communication, which is wireless communication in a narrower range than the wide-area communication, and the mobile member is a cluster member Information management step of requesting the mobile body of the cluster head from the mobile body of the cluster head via the short-range communication. A program for causing a computer to function as an information acquisition device provided in a mobile body that moves autonomously,
A cluster head determination function for determining a condition necessary for determining whether the mobile body is a cluster head or a cluster member in a cluster composed of a plurality of mobile bodies close to each other by near field communication; ,
A determination function for determining whether the mobile body is a cluster head or a cluster member based on the condition determination result provided from the cluster head determination unit;
When the mobile unit is a cluster head, it receives and stores information from the information server via a wide area communication unit that performs wide area wireless communication, and stores the information in response to a request from the cluster member mobile unit. Information is transmitted to a cluster member mobile unit via a short-range communication unit that performs wireless communication in a narrower range than wireless communication by the wide-area communication unit, and the information server A program for requesting the information managed by the mobile unit of the cluster head and executing an information management function for receiving the mobile unit of the cluster head from the mobile unit of the cluster head via the short-range communication unit.