Patent Publication Number: US-2020301410-A1

Title: Wireless device, wireless system, communication method, information transfer method, information transfer device, information transfer system, and program storage medium

Description:
TECHNICAL FIELD 
     The present invention relates to a communication device that transfers received control information. 
     BACKGROUND ART 
     In recent years, an unmanned vehicle called an unmanned X vehicle (UXV) has attracted attention. ‘X’ for the UXV takes various words. In the case of X=aerial, the UXV is an unmanned aerial vehicle (UAV). In the case of X=ground, the UXV is an unmanned ground vehicle (UGV). 
     There is an increasing demand to make use of such a UXV for various applications. For example, it is discussed that a plurality of unmanned vehicles forming a group achieve reduction in human risks and a safe and efficient operation in an area where it is difficult for a person to enter, such as check of a damage situation and a search for a disaster victim from above a disaster area. 
     Under an environment making use of such an unmanned vehicle, an unexpectable environmental change or event may occur. In order to accomplish a given operation by making use of a plurality of unmanned vehicles under such an environment, research and development are carried out relating to a control algorithm for individual unmanned vehicles to autonomously perform a collaborative operation. 
     For example, NPL 1 discloses a control algorithm that reconciles adaptability of individual unmanned vehicles and optimization in formation of individual unmanned vehicles in an unmanned vehicle group. This algorithm performs control in consideration of the following two indices in a comprehensive way. A first of the indices determines to which direction and to which position an individual unmanned vehicle is to move, based on information from a variety of sensors and the like provided in order for each unmanned vehicle to accomplish an operation. A second of the indices determines to which direction and to which position an individual unmanned vehicle is to move in consideration of a position of another unmanned vehicle, in order to execute a given operation collaboratively as a group. 
     PTL 1 discloses an approach for designating, by a node sending certain information, an area to which the information is to be transferred, and transferring the information to the area, in a wireless ad-hoc network. 
     PTL 2 discloses a wireless communication device that relays and transmits received data to another wireless communication device, stores device information identifying another wireless communication device with which a wireless communication is possible, and determines whether to relay received data to another wireless communication device. 
     PTL 3 discloses an ad-hoc communication device in which each device wirelessly communicates with another device in an autonomous and distributed way. 
     PTL 4 discloses a wireless device constituting a wireless communication network that is autonomously established and in which a wireless communication is performed between a transmission source and a transmission destination. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Translation of PCT International Application Publication No. JP-T-2010-518863 
         PTL 2: International Publication No. WO 2016/152104 
         PTL 3: Japanese Unexamined Patent Application Publication No. 2008-092196 
         PTL 4: Japanese Unexamined Patent Application Publication No. 2007-235895 
       
    
     Non Patent Literature 
     
         
         NPL 1: M. Ogawa, M. Emura, M. Ichien, and M. Yano, ““Autonomous and Adaptive Control”: Collaborative Swarm Control Algorithm Inspired by Adaptive Mechanism of Living Organisms,” in Proceedings of 2016 IEEE/OES Autonomous Underwater Vehicles (AUV), pp. 439 to 444, November 2016. 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     As described in the paragraphs of Background Art, in order that individual unmanned vehicles autonomously perform a collaborative operation in an unmanned vehicle group, it is necessary to allow information to be exchanged between moving unmanned vehicles. In order to do that, for example, it is effective to connect the unmanned vehicles to each other by using a wireless network called an ad-hoc network and accomplish an operation while exchanging information. 
     For example, a search from above an area where it is impossible for a person to enter or the like is assumed. In that case, unmanned vehicles fly while configuring an ad-hoc network, from a local headquarter where a person takes command. The unmanned vehicles search for, for example, an object or a person to be searched for, while capturing a downward image. 
     At that time, it is assumed that an unmanned vehicle detects an object or a person to be searched for. In that case, a video and a picture captured by the unmanned vehicle having detected the object or the person can be transferred to the headquarter by multihopping over the ad-hoc network among the unmanned vehicles, and a person can perform checking in detail. 
     Herein, the control algorithm disclosed in NPL 1 is based on the premise that individual unmanned vehicles are connected by an ad-hoc network. Then, the control algorithm exchanges, by using the configured ad-hoc network, positional information relating to a position at which each unmanned vehicle is currently present and a variety of information necessary for accomplishing an operation. 
     Thus, there is an issue that, as the number of unmanned vehicles forming a group increases, information to be exchanged increases, resulting in an increase in traffic amount (an increase in a traffic load). In general, a wireless ad-hoc network has a narrow available network bandwidth. Thus, when a traffic load of information to be exchanged increases, a wireless ad-hoc network needs increased amount of time for exchanging information, which adversely affects efficient accomplishment of an operation. A bandwidth necessary for transferring information such as a video and a picture may be depleted. 
     Herein, it is assumed that optimization relating to formation of individual unmanned vehicles is considered in a group formed by a plurality of unmanned vehicles. In that case, it is considered that unmanned vehicles at a close distance have a large influence on each other relating to mutual movement and positions. It is also considered that unmanned vehicles at a far distance have a small influence on each other relating to mutual movement and positions. 
     Thus, when the control algorithm disclosed in PTL 1 is executed, control information of unmanned vehicles at a close distance needs to be acquired with high frequency. However, it is considered that, even when control information of unmanned vehicles at a far distance is acquired with low frequency, optimality relating to formation of individual unmanned vehicles is not remarkably deteriorated. Meanwhile, it is considered that acquiring no control information of unmanned vehicles at a far distance may be a factor in failing to maintain the above-described optimality. Therefore, it is considered that traffic amount relevant to exchange of control information over a wireless ad-hoc network to which an unmanned vehicle is connected can be possibly reduced by varying a rate of acquiring control information according to a distance between unmanned vehicles. 
     Herein, it is assumed that, as an approach for stopping transfer of control information according to a distance, for one thing, a method of providing a lifetime called a time-to-live (TTL) for control information is considered as a candidate. This method limits a range to which the control information is transferred, by, for example, setting the maximum hop count through which transfer is possible and an expiration time of transfer. 
     This approach stops transfer of the control information at a point in time when a set hop count or time is exceeded. However, when a hop count is set as a TTL, it cannot be unconditionally said that a distance between a generation-source unmanned vehicle in which the control information is generated and an unmanned vehicle receiving the control information is long, even when the hop count, that is, the number of unmanned vehicles through which the control information is transferred, is large. Similarly, when an expiration time is set as a TTL, it cannot be unconditionally said that a distance between a generation-source unmanned vehicle in which the control information is generated and an unmanned vehicle receiving the control information is long, even when the expiration time is expired. 
     Therefore, when such an approach is used, it may be impossible to vary a rate of received control information according to a distance. 
     Meanwhile, the approach disclosed in PTL 1 can set an area by a generation-source unmanned vehicle in which control information is generated. However, in the approach, control information is not transferred at all to an unmanned vehicle existing outside the area. Therefore, as described above, it is considered that the approach in PTL 1 cannot maintain the above-described optimality. 
     The present invention is made in order to solve the above-described issue. 
     An object of the present invention is to provide an information transfer method and the like that can reduce a traffic load relating to exchange of control information necessary for control of individual unmanned vehicles to autonomously perform a collaborative operation, while ensuring the above-described optimality in the case of using a plurality of unmanned vehicles. The optimality is optimality in adaptability of individual unmanned vehicles and formation of the individual unmanned vehicles in an unmanned vehicle group, in the case of accomplishing a given operation. 
     Solution to Problem 
     A wireless device according to the present invention includes: a derivation unit that derives, from a first position that is included in sent first control information and is a position of a generation-source wireless device in which the first control information is generated, and a second position that is included in second control information to be sent by a candidate wireless device being a candidate for a device to which the first control information is transferred and is a position of the candidate wireless device, a distance between the generation-source wireless device and the candidate wireless device; a determination unit that calculates, by using a predetermined function that exhibits a tendency to decrease with an increase of the distance and always takes a positive value, a probability of transferring the first control information to the candidate wireless device; a transfer unit that performs the transfer based on the probability; and a sending unit that sends the first control information and the second control information to a movement control unit that controls autonomous movement by using the first control information and the second control information. 
     Advantageous Effects of Invention 
     The information transfer method and the like according to the present invention is capable of reducing a traffic load relating to exchange of control information necessary for control by which individual unmanned vehicles autonomously perform a collaborative operation, while ensuring optimality in the case of using a plurality of unmanned vehicles. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a conceptual diagram illustrating a configuration example of a communication system according to a first example embodiment. 
         FIG. 2  is a conceptual diagram illustrating a configuration example of a communication device according to the first example embodiment. 
         FIG. 3  is a conceptual diagram illustrating a processing flow example of processing relating to transmission of control information prepared by an application unit. 
         FIG. 4  is a conceptual diagram illustrating a processing flow example of processing of transferring control information. 
         FIG. 5  is a conceptual diagram illustrating a processing flow example of processing performed by a transfer propriety determination unit. 
         FIG. 6  is an image illustrating how processing of transferring control information is performed by a general communication device. 
         FIG. 7  is an image illustrating how processing of transferring control information is performed by the communication device according to the first example embodiment. 
         FIG. 8  is a conceptual diagram illustrating processing of replacing processing of S 305 . 
         FIG. 9  is a conceptual diagram illustrating a processing flow example of processing performed by a transfer propriety determination unit according to a third example embodiment. 
         FIG. 10  is a block diagram illustrating a configuration example of a communication device according to a fourth example embodiment. 
         FIG. 11  is a conceptual diagram illustrating a hardware configuration example of an information processing device that can achieve the communication device according to the example embodiments. 
         FIG. 12  is a block diagram illustrating a minimum configuration according to the example embodiments. 
     
    
    
     EXAMPLE EMBODIMENT 
     Next, example embodiments of the present invention will be described with reference to the drawings. The drawing schematically illustrates a configuration according to the example embodiment of the present invention. In addition, the example embodiment of the present invention described below is one example, and may be changed as appropriate within the scope of the identical essence. 
     First Example Embodiment 
     A first example embodiment is an example embodiment relating to a communication system that varies, according to a distance between a generation-source communication device by which the control information is generated and a communication device being a candidate for a device to which the control information is transferred, the number of transmission destinations for transfer of control information. It is assumed herein that transfer is used synonymously with delivery. 
     [Configuration and Operation] 
       FIG. 1  is a conceptual diagram illustrating a configuration of a communication system  1  being an example of the communication system according to the first example embodiment. 
     The communication system  1  includes communication devices  101  to  10   n  being n communication devices. Herein, n is an integer equal to or more than 2. 
     The communication devices  101  to  10   n  mutually have a common configuration described below. Hereinafter, each of the communication devices  101  to  10   n  will be sometimes denoted simply as a “communication device”. 
     The communication device can perform wireless communication with another communication device, and is capable of a certain extent of autonomous movement. The communication device is, for example, an unmanned vehicle called an unmanned X vehicle (UXV) described in the paragraphs of Background Art. 
     The wireless communication is, for example, a communication performed through a connection to a wireless local area network (LAN) such as Wireless Fidelity (abbreviated as Wi-Fi, a registered trademark). The communication devices can perform the wireless communication in a mutual way, for example, by an ad-hoc mode. 
     The communication devices may be connected to each other over a wireless ad-hoc network using a wireless communication technology other than a wireless LAN. In that case, any two of the communication devices may perform wireless communication in a mutual way via the wireless communication network. 
     The communication devices are capable of movement as described above. For the movement, each of the communication devices includes, for example, an engine, a motor, a fuel tank and a storage battery powering the engine and the motor, a wheel, a propeller, and the like. 
     Besides the above, each of the communication devices includes, as needed, an information acquisition means for acquiring information on surroundings, such as a camera and a variety of sensors. In that case, each of the communication device may acquire, by using the information acquisition means, a variety of environment information and the like such as a picture of surroundings, a video of surroundings, a temperature, and a humidity. 
     Each of the communication devices generates control information including positional information and the like of the communication device. Each of the communication devices may exchange or share the control information with another communication device. The control information includes a device ID, positional information, and a sequence number thereof. Herein, an ID is an abbreviation of an identifier, and means an identifier. The device ID can identify a communication device generating the control information. The positional information is positional information of the communication device acquired from global positioning system (GPS) information and the like. The sequence number is an information ID being able to identify generated control information for at least a certain period of time. 
     Each of the communication devices may transfer, to another communication device, a content such as a picture, a video, and sensing information acquired by using a camera and a variety of sensors included as needed. 
     Each of the communication devices transfers the control information and the content directly to a neighboring communication device, or alternatively, transfers the control information and the content by multihopping via a plurality of communication devices. Herein, a neighboring communication device of a certain communication device refers to a communication device existing within a range where a direct communication is possible mutually with the communication device by performing the wireless communication without being interposed by another communication device. 
     Each of the communication devices may recognize each other between the communication device and the neighboring communication device, by, for example, periodically broadcasting, to a periphery thereof, an administrative message that is called a beacon being a well-known art. 
     Alternatively, each of the communication devices and the neighboring communication device of the communication device may recognize each other, by using the control information. Such a method of detecting a neighboring communication device in an ad-hoc network is a well-known art, and thus, will not be described in detail. 
     In the following description, a communication device generating control information or content data will be referred to as a generation-source communication device in which control information or content data is/are generated. A communication device transmitting control information or content data to another communication device will be referred to as a transmission-source communication device from which control information or content data is/are transmitted, regardless of whether the control information or the content data is/are generated by the communication device. The generation-source communication device and the transmission-source communication device may be an identical communication device, or may be different communication devices. 
     The communication device according to the present example embodiment may share the control information generated by the communication device between the communication devices included in the communication system  1 , by transferring the control information therebetween. For the transfer, for example, transfer methods based on flooding and an epidemic method being well-known arts may be used. 
     In a transfer method based on flooding, it is assumed that a certain communication device receives the control information transmitted by a neighboring communication device of the communication device. In that case, the communication device having received the control information transfers the control information to another of the neighboring communication devices other than the transmission-source communication device from which the control information is transmitted. As a transfer method relating to the transfer, use of broadcasting or multicasting can be also contemplated, as will be described in a third example embodiment. However, according to the present example embodiment, transfer through unicasting is assumed. 
     Consequently, a certain communication device may possibly receive the identical control information from a plurality of other communication devices. In the information transfer method according to the present example embodiment, it is assumed that, when pieces of received control information are duplicated, the communication device receiving the control information discards the duplicated pieces of control information. As described above, control information includes an information ID identifying the control information. Thus, the duplicated pieces of control information can be discarded by deleting pieces of control information having the same information ID while leaving one of the pieces. 
     Alternatively, duplication of the control information may be prevented by using multipoint relay (MPR) in optimized link state routing (OLSR) being a well-known routing protocol, and the like. 
     In a transfer method based on an epidemic method, each of the communication devices periodically transmits and receives, to and from a neighboring communication device, a message including a summary vector stored in the communication device, and exchanges the summary vector. Herein, a summary vector is a list of contents including the control information held by the communication device. Each of the communication devices detects, based on a summary vector received from another communication device, a difference between contents held by the communication device and contents stored in the another communication device being a transmission source of the summary vector. Then, in order to eliminate the difference, each of the communication devices transmits, to the communication device being the transmission source of the summary vector, a content request requesting for transmission of a content as the difference. 
     Then, the communication device having received the content request transmits the requested content to the communication device having transmitted the content request. Such transfer of a content based on a content request is called pull-type transfer. 
     Alternatively, in the present transfer method, each of the communication devices may perform push-type transfer in which a communication device having detected, based on a summary vector, a content not stored in a communication device having transmitted the summary vector transmits the content to the communication device having transmitted the summary vector. 
     The communication device according to the present example embodiment utilizes a well-known art as described above, and determines a neighboring communication device to which the control information is transferred through unicasting. Therefore, in the following description, description will be given by assuming that a neighboring communication device being a transmission destination to which the control information is transferred by a certain communication device is already recognized by the communication device according to a well-known art as described above. 
     In the case of transmitting content data acquired by a camera and a variety of sensors included in a communication device to a particular communication device, transfer can be performed based on a routing protocol being a well-known art. 
     On the basis of the premise as described above, the communication device according to the present example embodiment will be described below. 
       FIG. 2  is a conceptual diagram illustrating a configuration of a communication device  100  being an example of the communication device according to the present example embodiment. 
     The communication device  100  includes a communication unit  110 , a data transmission/reception unit  120 , a transfer propriety determination unit  130 , an application unit  140 , a storing unit  150 , and a positional information acquisition unit  160 . The communication device  100  further includes a movement control unit  171 , a movement enabling unit  172 , and a movement information acquisition unit  173 . 
     The communication device  100  includes, besides the configuration illustrated in  FIG. 2 , the above-described configuration and the like relating to movement, photographing of a picture and a video, and sensing. These configurations are operated by control of the application unit  140 . The control can be achieved by using a well-known art, and thus, will not be described in detail. 
     The communication unit  110  includes a communication module such as, for example, a wireless LAN, for connecting to an unillustrated network processing unit described below and a wireless communication network configured between the communication devices in the communication system  1  illustrated in  FIG. 1 . The network processing unit performs, for example, processing of a transport layer such as a TCP or a UDP, processing on a network layer such as an IP, and processing of MAC and the like controlled by a kernel of an OS. Herein, an OS is an abbreviation of an operating system. A TCP is an abbreviation of a transmission control protocol, and a UDP is an abbreviation of a user datagram protocol. An IP is an abbreviation of an internet protocol, and MAC is an abbreviation of media access control. 
     The data transmission/reception unit  120 , the transfer propriety determination unit  130 , and the application unit  140  are, for example, a central processing unit (CPU) executing processing in accordance with program control. The data transmission/reception unit  120 , the transfer propriety determination unit  130 , and the application unit  140  execute processing in accordance with, for example, control of application software running on the basis of an OS mounted on the communication device  100 . 
     The data transmission/reception unit  120  transmits and receives control information and content data such as a picture and a video transmitted and received to and from the application unit  140 , to and from the above-described neighboring communication device via the communication unit  110 . 
     Further, the data transmission/reception unit  120  determines whether a communication device with which the communication device  100  communicates is the neighboring communication device of the communication device  100 . Then, the data transmission/reception unit  120  causes the storing unit  150  to store a list of neighboring communication devices of the communication device  100 . 
     Further, when receiving the control information from a neighboring communication device, the data transmission/reception unit  120  causes the transfer propriety determination unit  130  to determine whether to transfer the received control information to another neighboring communication device other than the transmission-source communication device from which the control information is transmitted. Then, when the determination result indicates transfer of the control information, the data transmission/reception unit  120  transfers the control information to the another neighboring communication device. 
     Further, the data transmission/reception unit  120  sends, to the movement control unit  171 , control information received from another communication device. 
     The communication unit  110  radiates a radio wave including information indicated by the data transmission/reception unit  120 , to a wireless space through an antenna included in the communication unit  110 . 
     Further, the communication unit  110  converts a radio wave arriving at an antenna included in the communication unit  110  into reception information, and sends the reception information to the data transmission/reception unit  120 . 
     The transfer propriety determination unit  130  determines whether to transfer control information received by the data transmission/reception unit  120  to another neighboring communication device  100  different from a transmission-source communication device from which the control information is transmitted. 
     When performing the determination, the transfer propriety determination unit  130  extracts a device ID, positional information of the generation-source communication device being a communication device that is a generation source of the control information, and an information ID from the control information received by the data transmission/reception unit  120 . The extracted device ID is a device ID of the generation-source communication device. The extracted information ID is an information ID of the control information. 
     The transfer propriety determination unit  130  determines, based on the extracted positional information of the generation-source communication device and positional information of a neighboring communication device being a transmission destination candidate, whether to transfer the control information. Then, the transfer propriety determination unit  130  sends a determination result relating to the determination to the data transmission/reception unit  120 . 
     The application unit  140  generates content data as needed. The application unit  140  causes the data transmission/reception unit  120  to transmit the content data to another communication device. 
     The application unit  140  acquires positional information from the positional information acquisition unit  160 , for example, at a preliminarily set timing for generating control information. The application unit  140  causes the storing unit  150  to hold recent positional information of the communication device  100  acquired from the positional information acquisition unit  160 . 
     The application unit  140  generates control information including recent positional information of the communication device  100 , a device ID of the communication device  100 , and a sequence number being an information ID of the control information, and sends the control information to the data transmission/reception unit  120 . 
     Further, when receiving control information generated by another communication device, the application unit  140  causes the storing unit  150  to store positional information of the another communication device included in the control information. The application unit  140  causes the storing unit  150  to store the positional information together with a device ID of the another communication device and an information ID of the control information. 
     At that time, when the storing unit  150  already holds positional information of the another communication device, the application unit  140  determines whether an information ID of the control information is newer than an information ID of control information already stored in the storing unit  150 . Then, when it is determined that the information ID of the control information is newer than the information ID of the control information already stored in the storing unit  150 , the application unit  140  causes the storing unit  150  to update the positional information. 
     Further, as needed, the application unit  140  photographs a picture and a video by using an unillustrated camera and the like, and converts the picture and the video into content data. Further, as needed, the application unit  140  converts sensor information acquired from a variety of unillustrated sensors into content data. The application unit  140  causes the data transmission/reception unit  120  to transfer the generated content data to another communication device. 
     The storing unit  150  is, for example, a storage medium such as a memory. The storing unit  150  preliminarily holds a variety of information necessary for achieving the information transfer method according to the present example embodiment. The information includes a program and information necessary for each of the application unit  140 , the data transmission/reception unit  120 , and the transfer propriety determination unit  130  to perform the above-described operation. 
     Further, the storing unit  150  stores information indicated by each of the application unit  140 , the data transmission/reception unit  120 , and the transfer propriety determination unit  130 . The information may include, for example, the above-described content data prepared by the application unit  140 , a list of device IDs of other communication devices, the above-described determination results, and the like. 
     Further, the storing unit  150  sends information indicated by each of the application unit  140 , the data transmission/reception unit  120 , and the transfer propriety determination unit  130  to any of the application unit  140 , the data transmission/reception unit  120 , or the transfer propriety determination unit  130  being an indicated transmission destination. 
     The positional information acquisition unit  160  successively acquires positional information of the communication device  100  by using a GPS and the like. The positional information acquisition unit  160  sends, in response to a request from the application unit  140 , positional information of the communication device  100  at a current time point to the application unit  140 . 
     The movement information acquisition unit  173  acquires movement information being information necessary for the movement control unit  171  to prepare control information to be sent to the movement enabling unit  172 . The movement information includes positional information of the communication device  100  or another communication device, and also includes speed information, acceleration information, image information, and the like. The movement information acquisition unit  173  acquires the positional information from the application unit  140 . The movement information acquisition unit  173  acquires movement information other than the positional information from a variety of sensors included in the movement information acquisition unit  173 . The movement information acquisition unit  173  sends the acquired information to the movement control unit  171 . 
     The movement control unit  171  generates a control signal, based on the information sent from the movement information acquisition unit  173  and the control information, and sends the generated control signal to the movement enabling unit  172 . The control signal indicates, for example, a direction of movement and a movement speed to the movement enabling unit  172 . The control signal causes the movement enabling unit  172  to perform a certain extent of autonomous movement of the communication device  100 . 
     The movement enabling unit  172  performs movement of the communication device  100  in accordance with the control signal sent from the movement control unit  171 . The movement enabling unit  172  causes the communication device  100  to move by means of rotation and the like of a propeller, a wheel, and the like according to the control signal from the movement control unit  171 . 
     [Processing Flow Example] 
       FIG. 3  is a conceptual diagram illustrating a processing flow example of processing performed by the application unit  140  illustrated in  FIG. 2  and relating to transmission of control information prepared by the application unit  140 . 
     The application unit  140  starts the processing illustrated in  FIG. 3 , for example, upon external input of start information. The start information is, for example, information for activating a program causing the application unit  140  to operate. 
     Then, as processing of S 101 , the application unit  140  performs determination as to whether to generate and transmit control information. The application unit  140  performs the determination by, for example, determining whether a timing for generating control information has come. Herein, the timing for generating control information is preliminarily set to, for example, one-second intervals and the like. Herein, the application unit  140  is assumed to be able to use a timer. 
     When a determination result in the processing of S 101  is yes, the application unit  140  performs processing of S 102 . 
     Meanwhile, when a determination result in the processing of S 101  is no, the application unit  140  performs processing of S 104 . 
     When performing the processing of S 102 , the application unit  140  generates control information as the processing. At that time, the application unit  140  acquires latest positional information from the positional information acquisition unit  160 . Then, the application unit  140  generates control information including the acquired latest positional information, a device ID of the communication device  100 , and an information ID of the control information. A device ID of the communication device  100  is, for example, a MAC address and an IP address of the communication device  100 . 
     Then, as processing of S 103 , the application unit  140  specifies a transmission destination of the control information, and performs transmission preparation of the control information. 
     For example, when control information is delivered based on the above-described pull-type, the application unit  140  sets a transmission source of the content request as a transmission destination of the control information. Specifically, the application unit  140  sets, as an identifier of the control information, for example, a combination of the device ID and the information ID included in the control information generated in S 102 , generates a summary vector including the identifier, and exchanges the summary vector as a message with a neighboring communication device. Since the neighboring communication device does not hold the control information, the neighboring communication device sends a content request to the communication device. A transmission-destination communication device to which the control information is sent is the transmission-source communication device from which the content request is sent. As the processing, a communication device causes the storing unit  150  to record a device ID of the specified transmission-destination communication device. The device ID of the transmission-destination communication device is, for example, a MAC address or an IP address of the transmission-destination communication device. As a specified transmission destination, one or more communication devices may be set as transmission destinations. When a method of delivering control information is based on the above-described flooding, all neighboring communication devices may be set as transmission destinations. 
     The transmission preparation means, for example, storing of generated control information in a transmission buffer included in the storing unit  150 . 
     Then, as the processing of S 104 , the application unit  140  causes the data transmission/reception unit  120  to transmit the control information prepared for transmission in the processing of S 103  to the specified transmission-destination communication device. 
     At a time of performing the processing of S 104 , when there is another piece of data to be sent, the application unit  140  may cause the data transmission/reception unit  120  to send the another piece of data. The another piece of data is, for example, the above-described content data. When the application unit  140  causes the data transmission/reception unit  120  to send the another piece of data, the application unit  140  stores, for example, the another piece of data in the transmission buffer. 
     Then, as processing of S 105 , the application unit  140  performs determination as to whether to end the processing illustrated in  FIG. 3 . The application unit  140  performs the processing by, for example, determining presence or absence of external input of end information. The end information is, for example, information for ending an operation of a program causing the application unit  140  to operate. 
     When a determination result in the processing of S 105  is yes, the application unit  140  ends the processing illustrated in  FIG. 3 . 
     Meanwhile, when a determination result in the processing of S 105  is no, the application unit  140  performs the processing of S 101  again. 
       FIG. 4  is a conceptual diagram illustrating a processing flow example of processing of transferring control information performed by the data transmission/reception unit  120  illustrated in  FIG. 2 . 
     The data transmission/reception unit  120  starts the processing illustrated in  FIG. 4 , for example, upon external input of start information. The start information is, for example, information for activating a program for causing the data transmission/reception unit  120  to operate. 
     Then, as processing of S 201 , the data transmission/reception unit  120  performs determination as to whether data is sent from the communication unit  110 . The data may include the above-described control information and the above-described content data. 
     When a determination result in the processing of S 201  is yes, the data transmission/reception unit  120  performs processing of S 202 . 
     When a determination result in the processing of S 201  is no, the data transmission/reception unit  120  performs the processing of S 201  again. 
     When performing the processing of S 202 , the data transmission/reception unit  120  performs, as the processing, reception processing of data sent from the communication unit  110 . The reception processing is, for example, as follows. 
     The data transmission/reception unit  120  performs reception processing according to whether a type of received data received via the communication unit  110  is control information or content data. 
     When the received data is control information, the data transmission/reception unit  120  sends the received control information to the application unit  140 , and causes the application unit  140  to perform the following processing. 
     Upon receiving an instruction from the data transmission/reception unit  120 , the application unit  140  extracts positional information of a generation-source communication device in which the control information is generated, a device ID of the generation-source communication device, and a sequence number being an information ID of the control information that are included in the control information. Hereinafter, positional information of a generation-source communication device in which control information is generated, a device ID of the generation-source communication device, and a sequence number being an information ID of the control information that are included in the control information will be also referred to as message information. The application unit  140  causes the storing unit  150  to hold the message information. 
     When the application unit  140  attempts to cause the storing unit  150  to hold message information, the storing unit  150  may sometimes already hold positional information of the generation-source communication device. In that case, for example, when the application unit  140  determines that an information ID of the control information is newer than a sequence number of control information held by the storing unit  150 , the application unit  140  updates the positional information. 
     Meanwhile, when the received data is content data, the data transmission/reception unit  120  sends the received data to the application unit  140 . In that case, the application unit  140  performs, on the received data, processing preliminarily defined as an application. 
     When the data transmission/reception unit  120  receives control information generated by a neighboring communication device, the data transmission/reception unit  120  causes the storing unit  150  to hold a device ID of the neighboring communication device through the above-described processing. 
     Next, as processing of S 203 , the data transmission/reception unit  120  performs determination as to whether the data on which reception processing is performed in the processing of S 202  is control information. 
     When a determination result in the processing of S 203  is yes, the data transmission/reception unit  120  performs processing of S 204 . 
     Meanwhile, when a determination result in the processing of S 203  is no, the data transmission/reception unit  120  performs processing of S 207 . 
     When performing the processing of S 204 , the data transmission/reception unit  120  causes, as the processing, the transfer propriety determination unit  130  illustrated in  FIG. 2  to perform processing illustrated in  FIG. 5  described later. At that time, the data transmission/reception unit  120  sends the message information to the transfer propriety determination unit  130 . 
     Then, as processing of S 205 , the data transmission/reception unit  120  performs determination as to whether a transfer instruction for the message information is issued by the transfer propriety determination unit  130  before a time period Tth elapses after the processing of S 204  is performed. Herein, the time period Tth is a time period preliminarily set in such a way that, when the transfer propriety determination unit  130  sends the transfer instruction in response to the message information, the transfer propriety determination unit  130  sends the transfer instruction by a time when the time period Tth elapses. 
     When a determination result in the processing of S 205  is yes, the data transmission/reception unit  120  performs processing of S 206 . 
     Meanwhile, when a determination result in the processing of S 205  is no, the data transmission/reception unit  120  performs the processing of S 207 . 
     When performing the processing of S 206 , the data transmission/reception unit  120  causes, as the processing, the communication unit  110  illustrated in  FIG. 2  to perform transfer of latest control information. A neighboring communication device being a transmission destination of the transfer is designated by the transfer propriety determination unit  130  at a time of processing of S 309  in  FIG. 5 , as will be described later. 
     Then, as the processing of S 207 , the data transmission/reception unit  120  performs determination as to whether to end the processing illustrated in  FIG. 4 . The data transmission/reception unit  120  performs the determination by, for example, determining presence or absence of external input of end information. The end information is, for example, information for ending an operation of a program causing the data transmission/reception unit  120  to operate. 
     When a determination result in the processing of S 207  is yes, the data transmission/reception unit  120  ends the processing illustrated in  FIG. 4 . 
     Meanwhile, when a determination result in the processing of S 207  is no, the data transmission/reception unit  120  performs the processing of S 201  again. 
       FIG. 5  is a conceptual diagram illustrating a processing flow example of processing performed by the transfer propriety determination unit  130  illustrated in  FIG. 2 . 
     The transfer propriety determination unit  130  starts the processing illustrated in  FIG. 5 , for example, upon external input of start information. The start information is, for example, information for activating a program for causing the transfer propriety determination unit  130  to operate. 
     Then, as processing of S 301 , the transfer propriety determination unit  130  performs determination as to whether an instruction for starting the processing illustrated in  FIG. 5  is issued by the data transmission/reception unit  120 . The instruction is an instruction illustrated as S 204  in  FIG. 4 . As described above, the instruction is issued together with sending of the message information. 
     When a determination result in the processing of S 301  is yes, the transfer propriety determination unit  130  performs processing of S 302 . 
     Meanwhile, when a determination result in the processing of S 301  is no, the transfer propriety determination unit  130  performs the processing of S 301  again. 
     When performing the processing of S 302 , the transfer propriety determination unit  130  prepares, as the processing, a list of neighboring communication devices, and causes the storing unit  150  illustrated in FIG.  2  to store the list. When there is no neighboring communication device, the transfer propriety determination unit  130  prepares an empty list, and causes the storing unit  150  to store the list. 
     Then, as processing of S 303 , the transfer propriety determination unit  130  performs determination as to whether there is a neighboring communication device not yet subjected to processing of S 304  in the list prepared in latest processing of S 302 . 
     When a determination result in the processing of S 303  is yes, the transfer propriety determination unit  130  performs the processing of S 304 . 
     Meanwhile, when a determination result in the processing of S 303  is no, the transfer propriety determination unit  130  performs processing of S 310 . 
     When performing the processing of S 304 , the transfer propriety determination unit  130  selects, as the processing, one neighboring communication device included in the list prepared in the latest processing of S 302  and not yet subjected to the processing of S 304 . 
     Then, as the processing of S 305 , the transfer propriety determination unit  130  acquires, from the storing unit  150  illustrated in  FIG. 3 , latest positional information of the neighboring communication device selected in the processing of S 304 . As described above, the storing unit  150  holds latest positional information of a generation-source communication device in which received control information is generated, in association with a device ID of the generation-source communication device. The generation-source communication device includes a neighboring communication device. Thus, the transfer propriety determination unit  130  can acquire latest positional information of the selected neighboring communication device from the storing unit  150 . 
     Next, as processing of S 306 , the transfer propriety determination unit  130  derives a distance d between a transmission-source communication device from which the control information is transmitted and the neighboring communication device selected in the processing of S 304 . 
     It is assumed that positional information is represented by three-dimensional (x, y, and z directions) coordinates, positional information of the generation-source communication device is (xi, yi, zi), and positional information of the neighboring communication device is (xj, yj, zj). In that case, the distance d can be derived by using the following expression (1). 
         d= √{square root over (( x   i   −x   j ) 2 +( y   i   −y   j ) 2 +( z   i   −z   j)   2 )}  (1)
 
     Then, as processing of S 307 , the transfer propriety determination unit  130  derives a transfer degree f from the distance d derived in the processing of S 306  and a predetermined constant R (called a transfer distance). The transfer degree f is given as a function g(d) of the distance d between a generation-source communication device in which the control information is generated and a neighboring communication device to be processed. The function g(d) gives a larger value as the distance d becomes larger. 
     The transfer propriety determination unit  130  derives the transfer degree f by using, for example, the following expression (2). 
         f=g ( d )=2 ceiling(d/R)−1    (2)
 
     Herein, ceiling(x) means the minimum integer equal to or more than x. A reciprocal of the transfer degree f is a value representing a degree of probability that control information is transferred according to a distance between a generation-source communication device in which the control information is generated and a neighboring communication device to be processed being a destination to which the control information is transferred. The transfer degree f=1 means that control information generated by a generation-source communication device in which the control information is generated is transferred every time. The transfer degree f=16 means that control information generated by a generation-source communication device in which the control information is generated is transferred once every sixteen times. 
     Next, as processing of S 308 , the transfer propriety determination unit  130  performs determination as to whether the transfer degree f derived in the processing of S 307  satisfies a preliminarily set condition. 
     The condition is that, for example, division of a sequence number s being an information ID of the control information by the transfer degree f leaves a remainder of zero. Accordingly, it is determined that the condition is satisfied once every f times. In other words, a probability that transfer is executed is 1/f. 
     When a determination result in the processing of S 308  is yes, the transfer propriety determination unit  130  performs processing of S 309 . 
     Meanwhile, when a determination result in the processing of S 308  is no, the transfer propriety determination unit  130  performs the processing of S 303  again. 
     When performing the processing of S 309 , the transfer propriety determination unit  130  instructs, as the processing, the data transmission/reception unit  120  to transfer control information sent by the data transmission/reception unit  120  to the transfer propriety determination unit  130 . The instruction is performed together with sending of a device ID of the neighboring communication device selected in the latest processing of S 304  to the data transmission/reception unit  120 . 
     Then, the transfer propriety determination unit  130  performs the processing of S 303  again. 
     When performing the processing of S 310 , the transfer propriety determination unit  130  performs, as the processing, determination as to whether to end the processing illustrated in  FIG. 5 . The transfer propriety determination unit  130  performs the determination by, for example, determining presence or absence of external input of end information. The end information is, for example, information for ending an operation of a program causing the transfer propriety determination unit  130  to operate. 
     [Specific Example] 
     Next, a specific example of processing of transferring control information performed by the communication device according to the present example embodiment will be described. 
     Next, an advantageous effect acquired by a transfer system according to the present example embodiment will be described in comparison with a case of a general transfer system. 
       FIG. 6  is an image illustrating how processing of transferring control information is performed by general devices  201  to  205  being examples of a general communication device. 
     In  FIG. 6 , the general devices  201  to  205  are arranged in a row in such a way that an interval between two adjacent general devices become a constant distance R. Transfer of control information may be performed directly between two adjacent general devices illustrated in  FIG. 6 . 
     Each rectangular shape with sort of a turned-up lower right corner illustrated in  FIG. 6  represents control information. A numerical character written in each piece of control information is an information ID of the control information. 
     Herein, it is assumed that the general device  201  sends each piece of control information having information IDs  1  to  8  to the general device  202  at timings t 1  to t 8  sequentially in this order, as illustrated in  FIG. 6 . 
     Then, the general device  202  transfers the each piece of control information received from the general device  201  to the general device  203 . 
     Then, the general device  203  transfers the each piece of control information received from the general device  202  to the general device  204 . 
     Then, the general device  204  transfers the each piece of control information received from the general device  203  to the general device  205 . 
     As described above, the general system illustrated in  FIG. 6  has a large traffic load relating to exchange of control information necessary for control to perform an autonomous collaborative operation. 
       FIG. 7  is an image illustrating how processing of transferring control information is performed by the communication devices  101  to  105  being examples of the communication device according to the present example embodiment. 
     In  FIG. 7 , the communication devices  101  to  105  are arranged in a row in such a way that an interval between two adjacent communication devices becomes a constant R. Transfer of control information may be performed directly between two adjacent communication devices illustrated in  FIG. 7 . 
     Each rectangular shape with sort of a turned-up lower right corner illustrated in  FIG. 7  represents control information. A numerical character written in each piece of control information is an information ID of the control information. 
     Herein, it is assumed that the communication device  101  sends each piece of control information having information IDs  1  to  8  to the communication device  102  at timings t 1  to t 8  sequentially in this order, as illustrated in  FIG. 7 . 
     Then, through the processing of S 306  illustrated in  FIG. 5 , the communication device  102  derives a double of the constant R as a distance d. Then, through the processing of S 307  in  FIG. 5 , the communication device  102  derives f=2 as a transfer degree f by using the above-described expression (2). 
     Then, the communication device  102  transfers, to the communication device  103 , only pieces of control information having information IDs  2 ,  4 ,  6 , and  8  among the each piece of control information received from the communication device  101 . Herein, the condition in the processing of S 308  is based on a premise that an information ID of control information divided by the transfer degree f leaves a remainder of zero. 
     Next, similarly, the communication device  103  derives d=3R and f=4, and transfers, to the communication device  104 , only pieces of control information having an information ID  4  or  8  among the each piece of control information received from the communication device  102 . 
     Next, similarly, the communication device  104  derives d=4R and f=8, and transfers, to the communication device  105 , only a piece of control information having an information ID  8  among the each piece of control information received from the communication device  103 . 
     In this way, in the communication system according to the present example embodiment illustrated in  FIG. 7 , as a distance d from a generation-source communication device in which control information is generated to a neighboring communication device increases, a probability that the control information reaches the neighboring communication device decreases. Thus, the communication system according to the present example embodiment reduces a traffic load relating to exchange of control information necessary for control of individual communication devices to autonomously perform a collaborative operation. 
     However, in the communication system according to the present example embodiment illustrated in  FIG. 7 , even when a distance d from a generation-source communication device in which control information is generated to a neighboring communication device being a transmission destination increases, a probability that the control information reaches the neighboring communication device being the transmission destination does not become zero. As described in the paragraphs of Technical Problem, in order to ensure the above-described optimality in the case of using communication devices, it is important that a probability that control information generated by any communication device reaches the communication devices does not become zero. Therefore, the communication system according to the present example embodiment can enable ensuring the above-described optimality in the case of using communication devices. 
     [Advantageous Effect] 
     As described in the paragraphs of Technical Problem, in order to ensure the above-described optimality in the case of using communication devices, it is important that a probability that control information generated by any communication device reaches the communication devices does not become zero. In order to reduce a traffic load relating to exchange of control information necessary for control of individual communication devices to autonomously perform a collaborative operation, it is effective that, as a distance d increases, a probability that control information reaches individual unmanned vehicles decreases. 
     The communication device according to the present example embodiment derives, when control information is sent from another communication device, a probability of transferring the control information, based on a distance d between a generation-source communication device in which the control information is generated and each neighboring communication device. The probability becomes smaller when the distance d increases, although does not becomes zero. 
     Therefore, the communication device according to the present example embodiment can reduce a traffic load relating to exchange of control information necessary for control of individual unmanned vehicles to autonomously perform a collaborative operation, while ensuring the above-described optimality in the case of using a plurality of unmanned vehicles. 
     Second Example Embodiment 
     A second example embodiment is an example embodiment relating to a communication system that sets a unique constant R for each communication device. 
     [Configuration and Operation] 
     An example of a communication system according to the second example embodiment is the same as the communication system  1  illustrated in  FIG. 1 . Description of a communication system  1  according to the second example embodiment is the same as the description of the communication system  1  according to the first example embodiment illustrated in  FIG. 1 , except for the following description about communication devices. 
     An example of a communication device according to the second example embodiment is the same as the communication device  100  illustrated in  FIG. 2 . Description of a communication device  100  according to the second example embodiment is the same as the description of the communication device  100  according to the first example embodiment, except for the following description. Hereinafter, description will be given of the communication device  100  according to the second example embodiment regarding a portion different from the communication device  100  according to the first example embodiment, by means of comparison with the communication device  100  according to the first example embodiment. When the following description is inconsistent with the description according to the first example embodiment, the following description is prioritized. 
     As described above, the communication device  100  according to the first example embodiment derives a transfer degree f for determining transfer propriety of control information, by using a constant R uniformly set for the entire communication system. 
     In contrast to this, the communication device  100  according to the second example embodiment sets the constant R individually for each communication device  100 . Further, control information generated by the communication device  100  according to the second example embodiment includes a device ID, positional information of the communication device  100 , a sequence number, and a constant R preliminarily set for the communication device  100 . The device ID is a device ID being able to identify the communication device  100  by which the control information is generated. The sequence number is an information ID being able to identify generated control information for at least a certain period of time. 
     Hereinafter, considering the above, components of the communication device  100  according to the second example embodiment will be described. 
     As described above, the transfer propriety determination unit  130  according to the first example embodiment receives a device ID of a generation-source communication device, positional information of the generation-source communication device, and an information ID of the control information that are extracted from which control information received by the data transmission/reception unit  120 . Then, the transfer propriety determination unit  130  according to the first example embodiment reads out positional information of a neighboring communication device other than the generation-source communication device in which the control information is generated that is stored in the storing unit  150 . Then, the transfer propriety determination unit  130  according to the first example embodiment determines whether to transfer the control information, based on these pieces of information. 
     In contrast to this, a transfer propriety determination unit  130  according to the second example embodiment reads out, from a storing unit  150 , information received from a data transmission/reception unit  120 , positional information of a neighboring communication device other than a generation-source communication device in which the control information is generated, and a constant R for the neighboring communication device. Then, the transfer propriety determination unit  130  determines whether to transfer the control information, based on these pieces of information. 
     As described above, when generating control information, the application unit  140  according to the first example embodiment generates control information including positional information acquired from the positional information acquisition unit  160 , a device ID of the communication device  100 , and a sequence number of the control information. Then, the application unit  140  sends the prepared control information to the data transmission/reception unit  120 . Upon receiving control information generated by another communication device, the application unit  140  causes the storing unit  150  to hold positional information of the generation-source communication device included in the control information, together with a device ID of the generation-source communication device and an information ID of the control information. 
     In contrast to this, when generating control information, an application unit  140  according to the second example embodiment generates the following, in addition to positional information acquired from a positional information acquisition unit  160 , a device ID of the communication device  100 , and a sequence number of the control information. That is, the application unit  140  generates control information including a constant R preliminarily set for the communication device  100 , and inputs the control information to the data transmission/reception unit  120 . Upon receiving control information generated by another communication device, the communication device  100  according to the second example embodiment causes the storing unit  150  to store positional information of the generation-source communication device and a constant R for the generation-source communication device included in the control information. The communication device  100  causes the storing unit  150  to store the positional information and the constant R together with a device ID of the generation-source communication device and an information ID of the control information. 
     As described above, the storing unit  150  according to the second example embodiment holds, in addition to a variety of information stored in the storing unit  150  according to the first example embodiment, a constant R for a transmission-source communication device from which control information is transmitted, in each transmission-source communication device. 
     [Processing Flow Example] 
     A processing flow example of processing performed by the application unit  140  according to the second example embodiment illustrated in  FIG. 2  and relating to transmission of control information prepared by the application unit  140  is the same as the processing flow example according to the first example embodiment illustrated in  FIG. 3 . 
     However, description of the processing flow example is different from that of the processing flow example according to the first example embodiment in the following point. 
     The processing flow example illustrated in  FIG. 3  according to the second example embodiment is different from the processing flow example illustrated in  FIG. 1  according to the first example embodiment in a point that processing of S 102  includes the following processing. 
     In other words, the application unit  140  generates control information including acquired latest positional information, a device ID of the communication device  100 , an information ID of the control information, and a constant R preliminarily set for the communication device  100 . 
     Except for the above description, description of processing of S 103  according to the second example embodiment is the same as the description of the processing of S 103  according to the first example embodiment. When the above description is inconsistent with the description of the processing of S 103  according to the first example embodiment, the above description is prioritized. 
     A processing flow example relating to transfer processing performed in the second example embodiment by the data transmission/reception unit  120  illustrated in  FIG. 2  when control information sent from another communication device is received is the same as the processing flow according to the first example embodiment illustrated in  FIG. 4 . However, description of the processing flow according to the second example embodiment is different from the description of the processing flow according to the first example embodiment in the following point. 
     A difference between the descriptions is the following portion relating to processing of S 202  in the processing flow. 
     The application unit  140  extracts positional information, a device ID, a constant R, and a sequence number of control information that are included in the control information included in received data, and causes the storing unit  150  to hold the positional information, the device ID, the constant R, and the sequence number. The positional information is positional information of a generation-source communication device in which the control information is generated. The device ID is a device ID of the generation-source communication device in which the control information is generated. The constant R is a constant R preliminarily set for the generation-source communication device in which the control information is generated. The sequence number is an information ID of the control information. 
     Except for the above description, description of the processing of S 202  according to the second example embodiment is the same as the description of the processing of S 202  according to the first example embodiment. When the above description is inconsistent with the description of the processing of S 202  according to the first example embodiment, the above description is prioritized. 
     A processing flow example of processing performed by the transfer propriety determination unit  130  illustrated in  FIG. 2  according to the second example embodiment is a processing flow in which the processing of S 305  illustrated in  FIG. 5  is replaced with processing of S 305   a  illustrated in  FIG. 8 . 
       FIG. 8  is a conceptual diagram illustrating processing with which the processing of S 305  illustrated in  FIG. 5  is replaced. 
     Description of the processing flow according to the second example embodiment to which the replacement is applied is different from the description of the processing flow according to the first example embodiment illustrated in  FIG. 5  in the following point. Except for the following description, the description of the processing flow to which the replacement is applied according to the second example embodiment is the same as the description of the processing flow according to the first example embodiment illustrated in  FIG. 5 . When the following description is inconsistent with the description according to the first example embodiment, the following description is prioritized. 
     Description about processing of S 304 , S 305   a,  and S 306  is different from the first example embodiment in a point as follows. 
     The processing of S 304  is followed by the processing of S 305   a.    
     When performing the processing of S 305   a,  the transfer propriety determination unit  130  acquires, as the processing, latest positional information of a neighboring communication device selected in the processing of S 304 , from the storing unit  150  illustrated in  FIG. 3 . Further, the transfer propriety determination unit  130  acquires, as the processing, a constant R for the neighboring communication device from the storing unit  150 . As described in the description according to the first example embodiment, a neighboring communication device periodically transmits control information. Thus, the storing unit  150  holds positional information of a neighboring communication device and a constant R for the neighboring communication device. Thus, the transfer propriety determination unit  130  can acquire, from the storing unit  150 , latest positional information of a selected neighboring communication device and a constant R for the selected neighboring communication device. 
     The processing of S 305   a  is followed by the processing of S 306 . 
     Description about processing of S 307  is different from the first example embodiment in a point as follows. 
     When performing the processing of S 307 , the transfer propriety determination unit  130  calculates, as the processing, a transfer degree f, based on the constant R acquired in the processing of S 305   a  and a distance d derived in the processing of S 306 . 
     Except for the above description, the description of S 307  according to the second example embodiment is the same as the description of S 307  according to the first example embodiment. 
     [Advantageous Effect] 
     A transfer system according to the present example embodiment individually sets a constant R for each communication device. In other words, this means that a range influenced in the case of determining formation of communication devices can be determined according to an attribute such as a movement speed of each of the communication devices. Accordingly, the transfer system enables further improvement of optimality relating to formation of a communication device group, in addition to the advantageous effect exhibited by the transfer system according to the first example embodiment. 
     Third Example Embodiment 
     A third example embodiment is an example embodiment relating to a communication device that transfers received control information to another communication device through multicasting or broadcasting. 
     [Configuration and Operation] 
     An example of a communication system according to the third example embodiment is the same as the communication system  1  illustrated in  FIG. 1 . Description of a communication system  1  according to the second example embodiment is the same as the description of the communication system  1  according to the first example embodiment illustrated in  FIG. 1 , except for the following description about communication devices. 
     An example of a communication device according to the third example embodiment is the same as the communication device  100  illustrated in  FIG. 2 . Description of a communication device  100  according to the third example embodiment is the same as the description of the communication device  100  according to the second example embodiment, except for the following description. Hereinafter, description will be given of the communication device  100  according to the third example embodiment regarding a portion different from the communication device  100  according to the second example embodiment, by means of comparison with the communication device  100  according to the second example embodiment. When the following description is inconsistent with the description according to the second example embodiment, the following description is prioritized. 
     As described above, when transferring control information, the communication device  100  according to the second example embodiment transfers control information to a neighboring communication device  100  by using unicasting. In contrast to this, when transferring control information, the communication device  100  according to the third example embodiment transfers control information by using broadcasting or multicasting. Hereinafter, considering the above, components of the communication device  100  will be described. 
     When transferring control information to a neighboring communication device, the data transmission/reception unit  120  according to the second example embodiment transfers, through unicasting, control information to each neighboring communication device being a transfer target. 
     In contrast to this, when transferring control information to a neighboring communication device, a data transmission/reception unit  120  according to the third example embodiment transfers control information to all neighboring communication devices at once by using broadcasting or multicasting. As such a transfer method, a so-called flooding approach being a well-known art is available. At that time, the data transmission/reception unit  120  may use MPR in OLSR being the above-described well-known routing protocol, and may prevent duplication of control information. Except for the above description, the data transmission/reception unit  120  according to the third example embodiment is the same as the data transmission/reception unit  120  according to the second example embodiment, and thus, will not be described. 
     The transfer propriety determination unit  130  according to the second example embodiment acquires a device ID of a generation-source communication device from which control information received by the data transmission/reception unit  120  is generated, positional information of the generation-source communication device, and a sequence number being an information ID of the control information that are extracted from the control information. Then, the transfer propriety determination unit  130  according to the second example embodiment reads out positional information of a neighboring communication device other than a transmission-source communication device from which the control information is transmitted and a constant R for the neighboring communication device that are held by the storing unit  151  . Then, the transfer propriety determination unit  130  according to the second example embodiment determines, based on these pieces of information, whether to transfer the control information, regarding each of neighboring communication devices being transfer candidates. 
     In contrast to that, a transfer propriety determination unit  130  according to the third example embodiment acquires information received from the data transmission/reception unit  120 , positional information of a neighboring communication device other than a transmission-source communication device from which the control information is transmitted, and a constant R for the neighboring communication device that are stored in the storing unit  150 . Then, the transfer propriety determination unit  130  according to the third example embodiment calculates, based on these pieces of information, a transfer degree f for each neighboring communication device being a transfer candidate. Then, the transfer propriety determination unit  130  according to the third example embodiment determines whether to transfer the control information through broadcasting or multicasting, with the smallest transfer degree f among transfer degrees f for the neighboring communication devices as a reference. The smallest transfer degree f means transfer of control information to a neighboring communication device relating to the transfer degree f is performed most frequently. 
     Except for the above description, description of the transfer propriety determination unit  130  according to the third example embodiment is the same as the description of the transfer propriety determination unit  130  according to the second example embodiment. 
     [Processing Flow Example] 
     A processing flow example of processing performed by an application unit  140  according to the third example embodiment illustrated in  FIG. 2  and relating to transmission of control information generated by the application unit  140  is the same as the processing flow according to the second example embodiment illustrated in  FIG. 3 . 
     However, description of the processing flow example is different from that of the processing flow example according to the second example embodiment in the following point. 
     The processing flow illustrated in  FIG. 3  according to the third example embodiment is different from the processing flow illustrated in  FIG. 3  according to the second example embodiment in the following point about processing of S 104 . 
     Specifically, the data transmission/reception unit  120  reads out transmission data being data to be transmitted that is in the head of a transmission buffer for performing processing of transmitting control information and content data in order. The transmission data is control information or content data. The data transmission/reception unit  120  transmits the read-out transmission data to a neighboring communication device being a transmission target via a communication unit  110 . When the read-out transmission data is control information, the data transmission/reception unit  120  transmits the control information by using broadcasting or multicasting. When the read-out transmission data is content data, the data transmission/reception unit  121  transmits the content data through any of unicasting, broadcasting, and multicasting, according to a transmission destination of the content data. 
     Except for the above description, description of the processing of S 104  according to the second example embodiment is the same as the description of the processing of S 104  according to the second example embodiment. When the above description is inconsistent with the description of the processing of S 104  according to the second example embodiment, the above description is prioritized. 
     A processing flow example relating to transfer processing performed by the data transmission/reception unit  120  illustrated in  FIG. 2  when control information sent from another communication device is received according to the third example embodiment is the same as the processing flow according to the second example embodiment illustrated in  FIG. 4 . However, description of the processing flow according to the third example embodiment is different from the description of the processing flow according to the second example embodiment in a point that processing of S 206  in the processing flow includes the following processing. 
     When performing the processing of S 206 , the data transmission/reception unit  120  transfers, as the processing, control information determined as being included in received data in processing of S 203 , through broadcasting or multicasting via the communication unit  110  illustrated in  FIG. 2 . 
     Except for the above description, description of the processing of S 206  according to the second example embodiment is the same as the description of the processing of S 206  according to the first example embodiment. When the above description is inconsistent with the description of the processing of S 206  according to the second example embodiment, the above description is prioritized. 
       FIG. 9  is a conceptual diagram illustrating a processing flow example of processing performed by the transfer propriety determination unit  130  according to the third example embodiment illustrated in  FIG. 3 . 
     Description about start, processing of S 301  to S 304 , S 305   a,  S 306 , S 307 , and S 310 , and end illustrated in  FIG. 9  is the same as the description of the processing and the like according to the second example embodiment illustrated in  FIGS. 5 and 8 . Hereinafter, description will be given of the processing flow illustrated in  FIG. 9 , regarding a portion different from the processing according to the second example embodiment. 
     The transfer propriety determination unit  130  according to the third example embodiment performs processing of S 302  followed by processing of S 302 - 2 . 
     When performing the processing of S 302 - 2 , the transfer propriety determination unit  130  sets, as the processing, a common transfer degree F. as an initial value. Herein, the common transfer degree F. is used in processing of S 308   a  described later. A term common in a common transfer degree means that the common transfer degree is applied commonly to neighboring devices in a list prepared in the processing of S 302 . It is assumed that the initial value of the common transfer degree F. is supposed to be sufficiently large in comparison with a normally derived transfer degree f. 
     Description of the processing of S 303 , S 304 , S 305   a,  S 306 , and S 307  is the same as the processing according to the second example embodiment as described above, and thus, will not be given. 
     The transfer propriety determination unit  130  according to the third example embodiment performs the processing of S 307  followed by processing of S 307 - 2 . 
     When performing the processing of S 307 - 2 , the transfer propriety determination unit  130  performs, as the processing, determination as to whether a transfer degree f derived in the processing of S 307  is smaller than the common transfer degree F. As described above, a sufficiently large value is set for the common transfer degree F. as an initial value. Thus, in the first processing of S 307 - 2  after the processing of S 302 - 2 , it is determined that the transfer degree f is smaller than the common transfer degree F. 
     When a determination result in the processing of S 307 - 2  is yes, the transfer propriety determination unit  130  performs processing of S 307 - 3 . 
     Meanwhile, when a determination result in the processing of S 307 - 2  is no, the transfer propriety determination unit  130  according to the third example embodiment performs the processing of S 303  again. 
     When performing the processing of S 307 - 3 , the transfer propriety determination unit  130  according to the third example embodiment sets, as the processing, the transfer degree f derived in the processing of S 307  as a common transfer degree F. Then, the transfer propriety determination unit  130  according to the third example embodiment performs the processing of S 303  again. 
     When a determination result in the processing of S 303  is no, the transfer propriety determination unit  130  according to the third example embodiment performs the processing of S 308   a.    
     When performing the processing of S 308   a,  the transfer propriety determination unit  130  according to the third example embodiment performs, as the processing, determination as to whether the common transfer degree F. satisfies a condition. 
     The condition is that, for example, division of a sequence number s being an information ID of the control information by the common transfer degree F. leaves a remainder of zero. Accordingly, it is determined that the condition is satisfied once every F times. 
     When a determination result in the processing of S 308   a  is yes, the transfer propriety determination unit  130  according to the third example embodiment performs processing of S 309   a.    
     Meanwhile, when a determination result in the processing of S 308   a  is no, the transfer propriety determination unit  130  according to the third example embodiment performs the processing of S 310 . 
     When performing the processing of S 309   a,  the transfer propriety determination unit  130  according to the third example embodiment instructs the transfer propriety determination unit  130  to transmit control information sent by the transfer propriety determination unit  130  when the transfer propriety determination unit  130  performs processing of S 204  illustrated in  FIG. 4 . The transmission is transmission through broadcasting or multicasting. Herein, in the case of the transmission through multicasting, the transfer propriety determination unit  130  assumes, when performing the instruction, that neighboring communication devices in a list prepared in the last processing of S 302  are included in a certain multicast group, and designates a multicast address of the group as a transmission-destination address. In the case of the transmission through broadcasting, designation of a transmission destination is unnecessary. 
     Then, the transfer propriety determination unit  130  according to the third example embodiment performs the processing of S 310 . Description of S 310  is the same as the description of S 310  according to the second example embodiment illustrated in  FIG. 5 . 
     [Advantageous Effect] 
     The communication system according to the third example embodiment enables reduction in traffic amount of control information according to a distance from a generation-source communication device in which the control information is generated, even when the control information is transmitted through broadcasting or multicasting. When control information is transmitted through broadcasting or multicasting, individual communication devices may possibly receive the control information with frequency higher than control information reception frequency determined on the basis of a proper transfer degree. However, broadcasting or multicasting enables batch transmission to a plurality of neighboring communication devices. Accordingly, the communication system enables more efficient transfer of control information, in addition to the advantageous effect exhibited by the communication system according to the second example embodiment. 
     The above description of the communication system according to the present example embodiment and a portion thereof is based on the description of the communication system according to the second example embodiment and a portion thereof. Further, the description of the communication system according to the second example embodiment and a portion thereof is based on the description of the communication system according to the first example embodiment and a portion thereof. Therefore, the communication system according to the present example embodiment and a portion thereof can be achieved by the communication system according to the first example embodiment and a portion thereof. 
     Regarding the data transmission/reception unit  120  according to the above-described first to third example embodiments, an example has been described in which control information and content data to be transmitted are written in an identical transmission buffer and, in the case of transmission, control information and content data is read out sequentially from the head of the transmission buffer and are transmitted. However, data transmission processing may be transmission in order of higher priority according to priority appropriately given to control information and content data to be transmitted, such as, for example, preferential transmission of control information. 
     Regarding the transfer propriety determination unit  130  according to the above-described first to third example embodiments, an example has been described in which a transfer degree f is calculated by using the expression (2). However, as the transfer degree f, a transfer degree f may be used that is preliminarily determined fixedly for a distance d between a generation-source communication device in which control information is generated and a neighboring communication device, and a constant R. A way of determination includes, for example, f=1 in the case of 0≤d/R&lt;1, f=2 in the case of 1≤d/R&lt;3, f=16 in the case of 3≤d/R, and the like. A transfer degree f is determined in such a way that f becomes larger as a distance d becomes larger. Thus, a method of calculating a transfer degree f is not limited to the expression (2) as long as the calculation method is capable of tinning control information to be transferred and reducing traffic amount. The communication device according to the example embodiment may transfer control information with a temporarily higher transfer probability or temporarily lower transfer probability than a transfer probability derived by using a transfer degree or the like. The communication system according to the example embodiment may be any communication system capable of achieving average reduction in traffic amount. 
     Regarding control information prepared by the communication device according to the above-described first to third example embodiments, an example has been described in which a sequence number is used as an information ID of control information. However, an information ID of control information is not limited to a sequence number. For example, by including time information or the like in control information, the control information can be also identified by using the time information as an information ID. In that case, however, the above-described determination method cannot be used in which transfer is performed when a sequence number divided by a transfer degree f leaves a remainder of zero. Instead, a method is applicable in which the number of pieces of control information not previously transferred to the storing unit is counted from the number of pieces of transferred control information for each generation-source communication device in which control information is generated, and transfer propriety is determined according to the counted value. 
     Furthermore, regarding the data transmission/reception unit  120  according to the above-described first to third example embodiments, an example has been described in which, when receiving control information generated by another communication device, the data transmission/reception unit  120  inquires of the transfer propriety determination unit  130  whether to transfer the control information to another neighboring communication device. Then, an example has been described in which the data transmission/reception unit  120  according to the first to third example embodiments performs transfer, based on a result of inquiry. However, by inquiring of the transfer propriety determination unit  130  at a time of first transfer of control information generated by the communication device  100 , even a generation-source communication device in which control information is generated can transfer the generated control information according to a transfer degree. 
     In addition to the above description, each component of the communication device  100  according to the above-described example embodiments may be configured by a semiconductor processing part including an application specific integrated circuit (ASIC). These components may be achieved by causing a computer system including at least one processor (for example, a microprocessor) and a DSP to execute a program. Herein, the microprocessor is a micro processing unit (MPU). A DSP is an abbreviation of a digital signal processor. 
     Specifically, one or a plurality of program(s) including instructions for causing a computer system to perform an algorithm relating to transmission signal processing or reception signal processing performed by the data transmission/reception unit  120 , the transfer propriety determination unit  130 , the application unit  140 , and the storing unit  150  is/are prepared. Then, the program(s) may be executed by a computer. 
     The program(s) may be provided for a computer by being stored in various types of non-transitory computer readable media. A non-transitory computer readable medium includes various types of recording media (tangible storage media). 
     A non-transitory computer readable medium is, for example, a magnetic recording medium (for example, a flexible disk, a magnetic tape, and a hard disk), a magneto-optical recording medium (for example, a magneto-optical disk), a CD-ROM, or a CD-R. Herein, a CD-ROM is an abbreviation of a compact disc-read only memory. A CD-R is an abbreviation of a compact disc-recordable. 
     Alternatively, a non-transitory computer readable medium is, for example, a CD-R/W or a semiconductor memory. Herein, a CD-R/W is an abbreviation of a compact disc-rewritable. A semiconductor memory is, for example, a mask ROM, a programmable ROM (PROM), or an erasable PROM (EPROM). 
     Alternatively, a non-transitory computer readable medium is, for example, a Flash ROM and a random access memory (RAM). 
     A program may be provided for a computer by various types of transitory computer readable media. A transitory computer readable medium is, for example, an electrical signal, an optical signal, and an electromagnetic wave. A transitory computer readable medium can provide a program for a computer via, for example, a wired communication path such as an electrical wire or an optical fiber, or via a wireless communication path. 
     The above-described example embodiments are not limited to the above description, and a change may be made therein as appropriate without departing from the spirit. 
     The above-described example embodiments are merely examples relating to application of a technical idea acquired by the present inventor. In other words, it is obvious that the technical idea is not limited to only the above-described example embodiments and various changes may be made therein. 
     Fourth Example Embodiment 
       FIG. 10  is a block diagram illustrating a configuration of a communication device  100   y  being an example of a communication device according to a fourth example embodiment. 
     The communication device  100   y  includes a positional information acquisition unit  10 , a data transmission/reception unit  11 , and a storing unit  12 . 
     The positional information acquisition unit  10  is, for example, the positional information acquisition unit  160  illustrated in  FIG. 2 . The data transmission/reception unit  11  is, for example, a combination of the communication unit  110 , the data transmission/reception unit  120 , and the transfer propriety determination unit  130  illustrated in  FIG. 2 . The storing unit  12  is, for example, the storing unit  150  illustrated in  FIG. 2 . 
     Upon request from the data transmission/reception unit  11  for acquisition of positional information, the positional information acquisition unit  10  acquires positional information (for example, a GPS) of the communication device  100   y  at that time, and notifies the data transmission/reception unit  11  of the positional information. 
     The data transmission/reception unit  11  generates control information described in the first to third example embodiments at preliminarily set time intervals, and transfers the control information to a neighboring communication device. Further, upon receiving control information generated by another neighboring communication device, the data transmission/reception unit  11  extracts a variety of information included in the received control information. The variety of information includes a device ID of a generation-source communication device, positional information of the generation-source communication device, an information ID of the control information, and a constant R. The data transmission/reception unit  11  causes the storing unit  12  to store the device ID, the positional information, the information ID, and the constant R. Then, the data transmission/reception unit  11  determines whether to transfer the received control information to another neighboring communication device. The data transmission/reception unit  11  calculates a transfer degree f, based on the positional information of the generation-source communication device in which the received control information is generated, a distance d calculated from positional information of a transmission-destination communication device held by the storing unit  12 , and a preliminarily set constant R, and performs the determination according to a value of the transfer degree f. 
     The storing unit  12  stores the above-described device ID of the generation-source communication device, the above-described positional information of the generation-source communication device, the above-described information ID of the control information, and the above-described constant R that are extracted from the received control information. 
     When transferring control information generated by each communication device to another communication device within a communication system, the communication device  100   y  determines whether to transmit the control information, based on a transfer degree according to a distance between a generation-source communication device in which the control information is generated and a communication device being a transmission destination. Consequently, every time control information is generated, the control information is transferred to a communication device at a close distance from a generation-source communication device in which the control information is generated. However, as the distance becomes farther, transmission destinations to which the control information is transferred are reduced according to a transfer degree, in a communication device through which the control information passes during transfer. 
     Thus, when a plurality of communication devices  100   y  accomplish a given operation while autonomously performing a collaborative operation, traffic amount relevant to exchange of a variety of information necessary for a control algorithm achieving the autonomous collaborative operation is reduced. Accordingly, the communication device  100   y  enables reduction in transfer delay of information necessary to be exchanged, and enables ensuring a bandwidth necessary for another information communication. 
     A configuration example of a hardware resource that achieves the communication device according to the above-described example embodiments of the present invention by using one information processing device (computer) will be described. The communication device may be achieved by using physically or functionally at least two information processing devices. The communication device may be achieved as a dedicated device. Only some of functions of the communication device may be achieved by using an information processing device. 
       FIG. 11  is a conceptual diagram illustrating a hardware configuration example of an information processing device capable of achieving the communication device according to the example embodiments of the present invention. An information processing device  90  includes a communication interface  91 , an input/output interface  92 , an arithmetic device  93 , a storage device  94 , a non-volatile storage device  95 , and a drive device  96 . 
     The communication interface  91  is a communication means by which the communication device according to the example embodiments communicates with an external device wiredly or/and wirelessly. When the communication device is achieved by using at least two information processing devices, these devices may be connected to each other in such a way as to be mutually communicable via the communication interface  91 . 
     The input/output interface  92  is a man-machine interface such as a keyboard being one example of an input device, and a display as an output device. 
     The arithmetic device  93  is an arithmetic processing device such as a general-purpose central processing unit (CPU) and a microprocessor. The arithmetic device  93  may read out, for example, a variety of programs stored in the non-volatile storage device  95  into the storage device  94 , and may execute processing according to the read-out programs. 
     The storage device  94  is a memory device such as a random access memory (RAM) that can be referred to from the arithmetic device  93 , and stores a program, a variety of data, and the like. The storage device  94  may be a volatile memory device. 
     The non-volatile storage device  95  is, for example, a non-volatile storage device such as a read only memory (ROM) and a flash memory, and can store a variety of programs, data, and the like. 
     The drive device  96  is, for example, a device that processes reading and writing of data from and in a recording medium  97  described later. 
     The recording medium  97  is, for example, any recording medium capable of recording data, such as an optical disk, a magneto-optical disk, and a semiconductor flash memory. 
     The example embodiments according to the present invention may be achieved by, for example, configuring a communication device by using the information processing device  90  exemplified in  FIG. 11 , and supplying the communication device with a program capable of implementing a function described in the above-described example embodiments. 
     In this case, the example embodiments can be achieved by the arithmetic device  93  executing the program supplied for the communication device. Some, but not all, of functions of the communication device can be also configured by using the information processing device  90 . 
     Furthermore, configuration may be made in such a way that the above-described program is recorded in the recording medium  97 , and the above-described program is stored in the non-volatile storage device  95  as appropriate in a shipment stage, an operational stage, or the like of the communication device. In this case, a method of supplying the above-described program may employ a method of installing the above-described program on the communication device by using an appropriate jig in a manufacture stage before shipment, an operational stage, or the like. Further, a method of supplying the above-described program may employ a general procedure, such as a method of downloading the above-described program externally via a communication line such as the Internet. 
     The example embodiments described above are preferred example embodiments of the present invention, and various changes may be made therein without departing from the spirit of the present invention. 
       FIG. 12  is a block diagram illustrating a configuration of a wireless device  100   x  being a minimum configuration according to the example embodiments. 
     The wireless device  100   x  includes a derivation unit  130   ax,  a determination unit  130   bx,  a transfer unit  120   x,  and a sending unit  121   x.    
     The derivation unit  130   ax  derives a distance between the generation-source wireless device and the candidate wireless device from a first position and a second position. Herein, the first position is a position of the generation-source wireless device, included in sent first control information. The second position is a position of a candidate wireless device being a candidate for a device to which the first control information is transferred, included in second control information sent by the candidate wireless device. 
     The determination unit  130   bx  calculates, by using a predetermined function that exhibits a tendency to decrease with an increase of the distance and always takes a positive value, a probability of transferring the first control information to the candidate wireless device. 
     The transfer unit  120   x  performs the transfer based on the probability. 
     The sending unit  121   x  sends the first control information and the second control information to a movement control unit that controls autonomous movement by using the first control information and the second control information. 
     As described in the paragraphs of Technical Problem, in order to ensure the above-described optimality in the case of using communication devices, it is important that a probability that control information generated by any communication device reaches each of the communication devices does not become zero. In order to reduce a traffic load relating to exchange of control information necessary for control of individual communication devices to autonomously perform a collaborative operation, it is effective that, as a distance d increases, a probability that control information reaches each unmanned vehicle decreases. 
     The wireless device  100   x  determines a probability of transferring the first control information to the candidate wireless device, based on the distance between the generation-source wireless device and the candidate wireless device. The probability exhibits a tendency to decrease when the distance increases, although does not becomes zero. A degree of the decrease as the distance increases may be adjusted by substituting the distance divided by a predetermined numerical value regulating the degree into the function, and the like. 
     Therefore, the wireless device  100   x  is capable of reducing a traffic load relating to exchange of control information necessary for control of individual unmanned vehicles to autonomously perform a collaborative operation, while ensuring the above-described optimality in the case of using a plurality of unmanned vehicles. 
     Thus, with the configuration, the wireless device  100   x  exhibits the advantageous effect described in the paragraphs of [Advantageous Effects of Invention]. 
     The wireless device  100   x  illustrated in  FIG. 12  is, for example, the communication devices  101  to  10   n  illustrated in  FIG. 1 , the communication device  100  illustrated in  FIG. 2 , and the communication device  100   y  illustrated in  FIG. 10 . 
     The derivation unit  130   ax  is, for example, a portion deriving a distance between the generation-source wireless device and the candidate wireless device, in the transfer propriety determination unit  130  illustrated in  FIG. 2 . 
     The determination unit  130   bx  is, for example, a portion calculating a probability of transferring the first control information to the candidate wireless device by using the function, in the transfer propriety determination unit  130  illustrated in  FIG. 2 . 
     The transfer unit  120   x  is, for example, a portion performing the transfer based on the probability, in the data transmission/reception unit  120  and the communication unit  110  illustrated in  FIG. 2 . 
     The sending unit  121   x  is, for example, a portion performing sending of the first control data and the second control data to the movement control unit  171 , in the data transmission/reception unit  120  illustrated in  FIG. 2 . 
     A sentence “exhibits a tendency to decrease with an increase of the distance” described above means that there may be a range of the distance within which a function value relating to the function increases along with an increase of the distance, but overall, the function value tends to decrease. For example, a case in which performing some kind of smoothing processing on the function results in a function after the smoothing processing that decreases with an increase of the distance is included in a case in which a function exhibits a tendency to decrease with an increase of the distance. The smoothing processing includes, for example, processing of deriving a spline curve or a B-spline curve for a predetermined number of function values of the function. 
     While the example embodiments of the present invention have been described, the present invention is not limited to the above-described example embodiments, and further modification, replacement, and adjustment may be added without departing from the basic technical idea of the present invention. For example, configurations of elements illustrated in the drawings are examples for helping understanding of the present invention, and there is no intention to limit the present invention to the configurations illustrated in the drawings. 
     Some or all of the above-described example embodiments can be described as the following supplementary notes, but are not limited to the following. 
     (Supplementary Note 1) 
     A wireless device including: 
     a derivation unit that derives, from a first position that is included in sent first control information and is a position of a generation-source wireless device in which the first control information is generated, and a second position that is included in second control information to be sent by a candidate wireless device being a candidate for a device to which the first control information is transferred and is a position of the candidate wireless device, a distance between the generation-source wireless device and the candidate wireless device; 
     a determination unit that calculates, by using a predetermined function that exhibits a tendency to decrease with an increase of the distance and always takes a positive value, a probability of transferring the first control information to the candidate wireless device; 
     a transfer unit that performs the transfer based on the probability; and 
     a sending unit that sends the first control information and the second control information to a movement control unit that controls autonomous movement by using the first control information and the second control information. 
     (Supplementary Note 2) 
     The wireless device according to supplementary note 1, wherein the function asymptotically approaches zero with an increase of the distance. 
     (Supplementary Note 3) 
     The wireless device according to supplementary note 1 or 2, wherein the function is in proportion to, relating to a value acquired by subtracting 1 from a minimum integer equal to or more than a number of the distance divided by a predetermined constant, a reciprocal of 2 raised to a power of the value. 
     (Supplementary Note 4) 
     The wireless device according to supplementary note 2 or 3, wherein the function is in proportion to a second function, and a proportionality constant relating to the proportion is unique for each of the candidate wireless devices. 
     (Supplementary Note 5) 
     The wireless device according to any one of supplementary notes 1 to 4, wherein the candidate wireless device is a neighboring wireless device to which the first control information can be sent wirelessly without passing through another wireless device. 
     (Supplementary Note 6) 
     The wireless device according to any one of supplementary notes 1 to 5, wherein the transfer is performed through unicasting. 
     (Supplementary Note 7) 
     The wireless device according to any one of supplementary notes 1 to 5, wherein the transfer is performed through broadcasting or multicasting. 
     (Supplementary Note 8) 
     The wireless device according to supplementary note 7, wherein the transfer is performed according to a maximum value of the probability derived for each of a plurality of the candidate wireless devices. 
     (Supplementary Note 9) 
     The wireless device according to supplementary note 8, wherein the transfer is performed according to a maximum value of the probability derived for each of all of the candidate wireless devices. 
     (Supplementary Note 10) 
     The wireless device according to any one of supplementary notes 1 to 5, wherein, when the transfer is performed, the transfer through multicasting is performed for all of the candidate wireless devices. 
     (Supplementary Note 11) 
     The wireless device according to any one of supplementary notes 1 to 10, wherein the first control information includes, in addition to the first position, a device ID of the generation-source wireless device and an information ID of the first control information. 
     (Supplementary Note 12) 
     The wireless device according to any one of supplementary notes 1 to 11, wherein the second control information includes, in addition to the second position, a device ID of the candidate wireless device and an information ID of the second control information. 
     (Supplementary Note 13) 
     A wireless system including a plurality of the wireless devices according to any one of supplementary notes 1 to 12. 
     (Supplementary Note 14) 
     A communication method including: 
     deriving, from a first position that is included in sent first control information and is a position of a generation-source wireless device in which the first control information is generated, and a second position that is included in second control information to be sent by a candidate wireless device being a candidate for a device to which the first control information is transferred and is a position of the candidate wireless device, a distance between the generation-source wireless device and the candidate wireless device; 
     calculating, by using a predetermined function that exhibits a tendency to decrease with an increase of the distance and always takes a positive value, a probability of transferring the first control information to the candidate wireless device; 
     performing the transfer based on the probability; and 
     sending the first control information and the second control information to a movement control unit that controls autonomous movement by using the first control information and the second control information. 
     (Supplementary Note 15) 
     The communication method according to supplementary note 14, wherein the derivation, the calculation, and the transfer are performed when autonomous movement is performed. 
     (Supplementary Note 16) 
     A communication program that causes a computer to execute: processing of deriving, from a first position that is included in sent first control information and is a position of a generation-source wireless device in which the first control information is generated, and a second position that is included in second control information to be sent by a candidate wireless device being a candidate for a device to which the first control information is transferred and is a position of the candidate wireless device, a distance between the generation-source wireless device and the candidate wireless device; 
     processing of calculating, by using a predetermined function that exhibits a tendency to decrease with an increase of the distance and always takes a positive value, a probability of transferring the first control information to the candidate wireless device; 
     processing of performing the transfer based on the probability; and 
     processing of sending the first control information and the second control information to a movement control unit that controls autonomous movement by using the first control information and the second control information. 
     (Supplementary Note 17) 
     An information transfer method that wirelessly transfers information between each pair of a plurality of communication devices, the information transfer method including: 
     a step of acquiring positional information of an own communication device being the communication device being a target; and 
     a data transmission/reception step of performing the transfer by generating set information including at least a device ID identifying the own communication device, acquired positional information, and an information ID identifying the positional information, and performing the transfer of the set information, as transfer target information, being received from a neighboring communication device with which direct wireless communication is possible and generated by another of the communication devices, to a neighboring communication device other than a transmission destination of the information, wherein 
     the data transmission/reception step includes: 
     calculating, from the positional information that is included in the transfer target information and relating to a generation-source communication device being the communication device as a generation source of the transfer target information, and the positional information that is notified from a transmission-destination neighboring communication device being the neighboring communication device as a transmission destination of the transfer target information, an inter-communication-device distance being a distance between the generation-source communication device and the transmission-destination neighboring communication device; 
     deriving, based on the inter-communication-device distance and a preliminarily set constant, a probability of performing the transfer of the transfer target information to a neighboring communication device; and 
     performing, based on the probability, the transfer of the transfer target information to the transmission-destination neighboring communication device. 
     (Supplementary Note 18) 
     The information transfer method according to supplementary note 17, wherein the transfer target information includes the set information received from the neighboring communication device and generated by another of the communication devices, and the set information generated by the own communication device. 
     (Supplementary Note 19) 
     The information transfer method according to supplementary note 17 or 18, wherein a transfer degree representing a transfer rate of the transfer target information is calculated by using the inter-communication-device distance and the constant, and the derivation is performed by using the transfer degree. 
     (Supplementary Note 20) 
     The information transfer method according to supplementary note 19, wherein the constant is set individually for each of the communication devices. 
     (Supplementary Note 21) 
     The information transfer method according to supplementary note 19 or 20, wherein the transfer is performed according to the transfer degree at equal intervals from a series of the transfer target information generated by each of the communication devices. 
     (Supplementary Note 22) 
     The information transfer method according to any of supplementary notes 19 to 21, wherein the transfer degree is set to such a value that indicates the transfer of the transfer target information with high frequency when the inter-communication-device distance is shorter than the constant, and indicates the transfer of the transfer target information with low frequency when the inter-communication-device distance is longer than the constant. 
     (Supplementary Note 23) 
     The information transfer method according to any of supplementary notes 19 to 22, wherein, 
     when the transfer of the transfer target information to the transmission-destination neighboring communication device is performed, whether to perform the transfer is determined based on the highest probability among the probabilities derived for each of the transmission-destination neighboring communication devices, and, 
     according to a result of the determination, the transfer of the transfer target information to each of the transmission-destination neighboring communication devices is performed by using broadcasting or multicasting. 
     (Supplementary Note 24) 
     An information transfer device being a communication device that wirelessly transfers information between each pair of a plurality of the communication devices, the information transfer device including: 
     a positional information acquisition means for acquiring positional information of an own communication device; and 
     a data transmission/reception means for performing the transfer by generating set information including at least a device ID identifying the own communication device, acquired positional information, and an information ID identifying the set information, and performing the transfer of the set information, as transfer target information, being received from a neighboring communication device being the communication device with which direct wireless communication is possible and generated by another of the communication devices, to the neighboring communication device other than a transmission destination of the set information, wherein 
     the data transmission/reception means 
     calculates, from the positional information that is included in the transfer target information and representing a position of a generation-source communication device being a generation source of the set information, and the positional information that is notified from a transmission-destination neighboring communication device to which the transfer target information is transferred, an inter-communication-device distance between the generation-source communication device and the neighboring communication device being a transmission destination relating to the transfer; 
     derives, based on the inter-communication-device distance and a preliminarily set constant, a probability of performing the transfer of the transfer target information to the neighboring communication device; and 
     performs, based on the probability, the transfer of the transfer target information to the transmission-destination neighboring communication device, and 
     the information transfer device is the own communication device. 
     (Supplementary Note 25) 
     An information transfer system including a plurality of the communication devices according to supplementary note 24. 
     (Supplementary Note 26) 
     A program for information transfer that causes a computer to execute: 
     processing of acquiring positional information of an own communication device being a communication device that wirelessly transfers information between each pair of a plurality of the communication devices; and 
     data transmission/reception processing of performing transfer by generating set information including at least a device ID identifying the own communication device, acquired positional information, and an information ID identifying the set information, and performing the transfer of the set information, as transfer target information, being received from a neighboring communication device being the communication device with which direct wireless communication is possible and generated by another of the communication devices, to the neighboring communication device other than a transmission destination of the set information, wherein 
     the data transmission/reception processing includes: 
     processing of calculating, from the positional information that is included in the transfer target information and relating to a generation-source communication device being the communication device as a generation source of the set information, and the positional information that is notified from the neighboring communication device being a transmission destination of the transfer target information, an inter-communication-device distance between the generation-source communication device in which the transfer target information is generated and the neighboring communication device being the transmission destination; 
     processing of deriving, based on the inter-communication-device distance and a preliminarily set constant, a probability of performing the transfer of the transfer target information to the neighboring communication device; and 
     processing of performing, based on the probability, the transfer of the transfer target information to the neighboring communication device being the transmission destination. 
     While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims. 
     This application is based upon and claims the benefit of priority from Japanese patent application No. 2017-223378, filed on Nov. 21, 2017, the disclosure of which is incorporated herein in its entirety by reference. 
     REFERENCE SIGNS LIST 
     
         
           1  Communication system 
           90  Information processing device 
           91  Communication interface 
           92  Input/output interface 
           93  Arithmetic device 
           94  Storage device 
           95  Non-volatile storage device 
           96  Drive device 
           97  Recording medium 
           100 ,  100   y,    101 ,  102 ,  103 ,  104 ,  105 ,  10   n  Communication device 
           100   x  Wireless device 
           110  Communication unit 
           11 ,  120  Data transmission/reception unit 
           120   x  Transfer unit 
           121   x  Sending unit 
           130  Transfer propriety determination unit 
           130   ax  Derivation unit 
           130   bx  Determination unit 
           140  Application unit 
           12 ,  150  Storing unit 
           10 ,  160  Positional information acquisition unit 
           171  Movement control unit 
           172  Movement enabling unit 
           173  Movement information acquisition unit 
           201 ,  202 ,  203 ,  204 ,  205  General device