JP2015005888A - Communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent flooding that may occur in a ferry if there are a lot of nodes (communication terminals) in a radio communication available range in the ferry when the ferry (communication terminal) has moved to a closed area.SOLUTION: At arrival of scheduled time when a ferry moving between closed areas arrives at a specific location in a closed area, if nodes moving around in the closed area are in a certain distance from the specific location, each of the nodes negotiates with the other nodes by radio for which node will have a right to communicate with the ferry in order to limit the number of nodes having the right to communicate with the ferry to a threshold value or below. Each node exchanges data with the ferry by radio if it was determined that it has the right to communicate with the ferry by the negotiation.

Description

  The present invention relates to a communication system, a data exchange method, a communication terminal, and a program.

  In recent years, research has been conducted on a delay tolerant network (DTN) that realizes high data reachability even in an inferior communication environment with high discontinuity and large transmission delay. As a characteristic technique of DTN, there is a store-carry-forward. This is a technique for transferring data to a destination by transmitting replicated data when each communication terminal once accumulates and moves the data in a buffer and becomes communicable with another communication terminal. Details of DTN are described in Non-Patent Document 1.

  As a method for transmitting and receiving data between DTN communication terminals, between a first communication terminal moving on a route and a plurality of second communication terminals moving in a closed area including the route. Exchange of data has been proposed as a first related technique related to the present invention (see, for example, Patent Document 1). Specifically, in the first related technology, if the second communication terminal that moves in the closed area is within the wireless communication range of the first communication terminal that moves between the closed areas along the route, Exchange data with other communication terminals.

JP 2010-109688 A

RFC4838 Delay-Tolerant Networking Architecture April 2007 A. Vahdat, D. Becker, “Epidic Routing for Partially-Connected Ad Hoc Networks,” Tech. Report CS-200006, Duke University, Apr.

  In a first related technique related to the present invention, in data exchange between a first communication terminal moving on a route and a plurality of second communication terminals moving in a closed area including the route, When the second communication terminal is within the wireless communication range of the first communication terminal, the second communication terminal communicates with the first communication terminal to exchange data. Therefore, when the first communication terminal moves from outside the closed area to within the closed area, if there are many second communication terminals within the wireless communication range of the first communication terminal, the first communication terminal Flatting occurs. That is, many second communication terminals transmit data to the first communication terminal, so that a large amount of data exceeding the assumption suddenly flows into the first communication terminal at a certain time.

  The object of the present invention is that the above-described problem, that is, when a number of second communication terminals exist within the wireless communication range of the first communication terminal when the first communication terminal moves into the closed area. An object of the present invention is to provide a communication system that solves the problem that flatting occurs in a first communication terminal.

A communication system according to a first aspect of the present invention includes:
A communication system comprising: a first communication terminal that moves on a predetermined route; and a plurality of second communication terminals that move within a closed area including the route and are capable of wireless communication with the first communication terminal. Because
The first communication terminal is
A first wireless communication unit that wirelessly transmits and receives data to and from other communication terminals;
A first data exchange unit for exchanging retained data through the first wireless communication unit with the second communication terminal existing within the wireless communication range of the own communication terminal;
Each of the second communication terminals is
A second wireless communication unit that wirelessly transmits and receives data to and from other communication terminals;
If the communication terminal is within a certain distance from the specific position when the first communication terminal arrives at a specific position on the route in the closed area, In order to limit the number of the second communication terminals having the authority to communicate with the communication terminal to be equal to or less than a threshold, it is possible to determine which of the second communication terminals has the authority to communicate with the first communication terminal. A communication availability negotiation unit that negotiates with the second communication terminal and the second wireless communication unit;
Exchange of possessed data through the second wireless communication unit with the first communication terminal when the communication availability negotiation unit determines that the own communication terminal has authority to communicate with the first communication terminal And a second data exchange unit.

A data exchange method according to the second aspect of the present invention includes:
A method for wirelessly exchanging data between a first communication terminal moving on a predetermined route and a second communication terminal moving in a closed area including the route,
When the second communication terminal arrives at a scheduled time at which the first communication terminal arrives at a specific position on the route in the closed area, the own communication terminal exists within a certain distance from the specific position. If so, any of the second communication terminals communicates with the first communication terminal in order to limit the number of the second communication terminals having authority to communicate with the first communication terminal to a threshold value or less. Negotiate wirelessly with the other second communication terminal about whether or not it has authority,
When the second communication terminal determines that the communication terminal has the authority to communicate with the first communication terminal by the negotiation, the second communication terminal exchanges data with the first communication terminal by radio. .

A communication terminal according to a third aspect of the present invention is:
A second communication terminal that moves in a closed area including the route of the first communication terminal that moves on a predetermined route and is capable of wireless communication with the first communication terminal;
A wireless communication unit that transmits and receives data to and from other communication terminals wirelessly;
A data storage unit for storing data to be transmitted to the first communication terminal and data received from the first communication terminal;
If the communication terminal is within a certain distance from the specific position when the first communication terminal arrives at a specific position on the route in the closed area, In order to limit the number of the second communication terminals having the authority to communicate with the communication terminal to be equal to or less than a threshold, it is possible to determine which of the second communication terminals has the authority to communicate with the first communication terminal. A communication availability negotiation unit that negotiates with the second communication terminal and the second wireless communication unit;
Data for exchanging the data through the wireless communication unit with the first communication terminal when the communication availability negotiation unit determines that the own communication terminal has the authority to communicate with the first communication terminal. And an exchange part.

  Since the present invention has the above-described configuration, when the first communication terminal moves into the closed area, there are many second communication terminals in the wireless communication range of the first communication terminal. However, it is possible to prevent the first communication terminal from being flattened.

1 is a configuration diagram of a communication system according to a first embodiment of the present invention. It is a block diagram of the node (communication terminal) in the communication system which concerns on the 1st Embodiment of this invention. It is a block diagram of the ferry (communication terminal) in the communication system which concerns on the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the node (communication terminal) in the communication system which concerns on the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the ferry (communication terminal) in the communication system which concerns on the 1st Embodiment of this invention. In the communication system which concerns on the 1st Embodiment of this invention, it is a schematic diagram which shows the positional relationship of the ferry and the node in an area in the scheduled time when a ferry arrives at the specific point in an area. It is explanatory drawing of the subject which the 2nd Embodiment of this invention tends to solve. It is explanatory drawing of the effect of the 2nd Embodiment of this invention. It is a block diagram of the communication terminal which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows an example of the operation | movement in the 2nd Embodiment of this invention. It is a flowchart which shows an example of the operation | movement in the 2nd Embodiment of this invention. It is a schematic diagram which shows the other example of the operation | movement in the 2nd Embodiment of this invention. It is a flowchart which shows the other example of the operation | movement in the 2nd Embodiment of this invention. It is a schematic diagram which shows the further another example of the operation | movement in the 2nd Embodiment of this invention. It is a flowchart which shows the further another example of the operation | movement in the 2nd Embodiment of this invention.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
[First embodiment]
Referring to FIG. 1, a communication system 100 according to the first embodiment of the present invention includes a ferry 110 and a plurality of nodes 120.

  The ferry 110 is a communication terminal having a wireless communication function. The ferry 110 is mounted on a moving body such as a vehicle that moves along the route 130. The ferry 110 may be carried by a person without being mounted on a moving body. The ferry 110 moves on the route 130 so as to arrive at a predetermined point on the route 130 at a predetermined time. In this embodiment, the ferry 110 arrives at the point B1 at time t1 and arrives at the point B2 at time t2. As will be described later, when the ferry 110 arrives at the point B1, the ferry 110 exchanges data with the nodes 120 existing around the point B1. When the ferry 110 arrives at the point B2, the ferry 110 exchanges data with the nodes 120 existing around the point B2.

  The node 120 is a communication terminal having a wireless communication function. The node 120 is mounted on a moving body such as a vehicle that moves in an area (closed area) including a ferry moving route. The node 120 may not be mounted on a moving body but may be carried by a person. In the present embodiment, a total of seven nodes 120-1 to 120-7 move in the area 140. In addition, a total of five nodes 120-8 to 120-12 move within the area 150. It is needless to say that the number of nodes is 7 and 5 for convenience of explanation and is not limited to the number of nodes. Further, the area 140 includes the point B1, and the area 150 includes the point B2. As will be described later, only a specific node 120 among the plurality of nodes 120 moving in the area 140 exchanges data with the ferry 110 that has arrived at the point B1. Further, only a specific node 120 among the plurality of nodes 120 moving in the area 150 exchanges data with the ferry 110 that has arrived at the point B2.

  Referring to FIG. 2, the node 120 includes a communication unit 121, a communication availability negotiation unit 122, a data exchange unit 123, and a data storage unit 124.

  The communication unit 121 has a function of transmitting and receiving data to and from other communication terminals wirelessly. The communication unit 121 controls communication protocols in the transport layer and lower layers. A communication protocol such as TCP or UDP may be used for the transport layer. As a communication protocol below the link layer, any communication protocol such as Wi-Fi Adhoc or Wi-Fi Direct may be used as long as wireless communication is possible.

  The data storage unit 124 has a function of storing data 1241 transmitted to the ferry 110 and data 1242 received from the ferry 110. Hereinafter, the data 1241 transmitted to the ferry 110 is referred to as ferry addressed data. The type of data is arbitrary. For example, any of text data, image data, and audio data may be used, or they may be mixed. The data may be called content. The data storage unit 124 is configured by a storage medium such as a memory such as a RAM and a hard disk, for example.

  The communication availability negotiation unit 122 has a function of monitoring whether or not the scheduled time for the ferry 110 to arrive at a specific point in the area of the own communication terminal has arrived. Further, when detecting that the scheduled time has arrived, the communication availability negotiation unit 122 has a function of determining whether or not the own node 120 exists at a location within a certain distance from the specific point at that time. . The fixed distance is a distance within the maximum distance at which the node 120 can wirelessly communicate with the ferry 110 and other nodes 120, and may be set to a distance that is half or less than the maximum distance, for example. In addition, when it is determined that the own node 120 exists within a certain distance from the specific point, the communication availability negotiation unit 122 limits the number of nodes 120 having authority to communicate with the ferry 110 to a threshold value or less. It has a function of negotiating with other nodes 120 as to which node 120 has authority to communicate with the ferry 110.

  The communication availability negotiation unit 122 stores therein the scheduled time at which the ferry 110 arrives at a specific point in the area of the communication terminal, position information (for example, latitude, longitude, altitude) of the specific point, a threshold value, and information on the predetermined distance. doing. Or the data storage part which memorize | stores those information may be equipped in the node 120, and the communication availability negotiation part 122 may be made to read required data from the said data storage part.

  For monitoring the arrival of the scheduled time, the communication availability negotiation unit 122 may periodically perform a process of comparing the scheduled time with the current time, for example. Alternatively, in the monitoring of the arrival of the scheduled time, the communication availability negotiation unit 122 may obtain a difference time between the scheduled time and the current time, set the difference time in a timer, and detect that the timer times out. .

  Further, in determining whether or not the own node is present within a certain distance from the specific point where the ferry 110 arrives, the communication availability negotiation unit 122 measures the current location of the own node using, for example, GPS, and the measured current location. And the distance to the specific point may be calculated, and it may be determined whether or not the calculated distance is equal to or less than a certain distance.

  Further, in the negotiation with other nodes, the communication availability negotiation unit 122 exchanges the distance between the position of each node 120 at the scheduled time and the specific point at which the ferry 110 arrives at the scheduled time, and exchanges the distance between them. Based on the size, it may be determined which node 120 is authorized to communicate with the ferry 110. Specifically, for example, only the upper predetermined number of nodes 120 having a short distance to the specific point may have the authority to communicate with the ferry.

  Alternatively, the communication permission / negotiation negotiating unit 122 may determine which node 120 has the authority to communicate with the ferry 110 by means of bargaining when negotiating with other nodes. Specifically, for example, it is possible to perform a junk between the nodes 120 in a tournament format, and only a predetermined number of winner nodes have the authority to communicate with the ferry.

  Alternatively, in the negotiation with other nodes, the communication availability negotiation unit 122 communicates with the ferry 110 based on the priority of the data 1241 addressed to the ferry stored in the data storage unit 124 of each node 120. You may decide whether you have the authority to do so. Specifically, for example, when the ferry addressed data 1241 is composed of a plurality of data, the priority of the highest priority data among these data and the average value of the priorities of all data are set as the node priority, and the node The upper predetermined number of nodes 120 with high priority may be authorized to communicate with the ferry 110. Also, for example, when the data addressed to the ferry 1241 is composed of the same number of data in all nodes, the priority of each data is set as the node priority, and the upper predetermined number of nodes 120 having a higher node priority communicate with the ferry 110. May be included.

  The data exchange unit 123 has a function of transmitting / receiving data to / from surrounding communication terminals through the communication unit 121. The data exchange unit 123 exchanges data with the ferry 110 when the communication availability negotiation unit 122 determines that the own node 120 has the authority to communicate with the ferry 110. Specifically, the data exchange unit 123 first transmits the ferry addressed data 1241 stored in the data storage unit 124 to the ferry 110 through the communication unit 121. Next, the data exchange unit 123 receives the data transmitted from the ferry 110 through the communication unit 121 and stores the data as data 1242 in the data storage unit 124.

  The communication availability negotiation unit 122 and the data exchange unit 123 may be realized by, for example, a computer and a program that configure the node 120.

  Referring to FIG. 3, the ferry 110 includes a communication unit 111, a data storage unit 112, and a data exchange unit 113.

  The communication unit 111 has the same function as the communication unit 121 of the node 120.

  The data storage unit 112 has a function of storing data 1121 transmitted to the node 120 and data 1122 received from the node 120. Hereinafter, the data 1121 transmitted to the node 120 is referred to as node-addressed data. The type of data is arbitrary. For example, any of text data, image data, and audio data may be used, or they may be mixed. The data may be called content. The data storage unit 112 is configured by a memory such as a RAM and a storage medium such as a hard disk, for example.

  The data exchange unit 113 has a function of transmitting / receiving data to / from surrounding communication terminals through the communication unit 111. Specifically, when the data exchange unit 113 receives the data transmitted from the node 120 through the communication unit 111, the data exchange unit 113 stores the received data 1122 in the data storage unit 112. In addition, the data exchange unit 113 transmits the node-addressed data 1121 stored in the data storage unit 112 to the node 120 that has transmitted the received data to its own terminal.

  The data exchange unit 113 may be realized by a computer and a program that constitute the ferry 113, for example.

  Next, the operation of the communication system according to the present embodiment will be described.

  Referring to FIG. 1, among the plurality of nodes 120, the nodes 120-1 to 120-7 move in the area 140, and the nodes 120-8 to 120-12 move in the area 150. On the other hand, the ferry 110 is moving on the route 130. Each node 120 executes the process shown in the flowchart of FIG. 4, and the ferry 110 executes the process shown in the flowchart of FIG.

  Referring to FIG. 4, the communication availability negotiation unit 122 of each node 120 monitors the arrival of the scheduled time when the ferry 110 arrives at a specific point in the area where the node 120 moves (step S101). Then, the communication availability negotiation unit 122 executes the following process when the scheduled time arrives.

  First, the communication feasibility negotiation unit 122 determines whether or not the current node 120 currently exists at a location within a certain distance from the specific point (step S102). If the own node 120 does not exist at a certain distance from the specific point, the communication availability negotiation unit 122 returns to step S101, and the next scheduled time when the ferry 110 arrives at the specific point in the area is reached. To monitor.

  On the other hand, if the own node 120 exists at a location within a certain distance from the specific point, the communication availability negotiation unit 122 communicates with the other node 120 within a certain distance from the specific point with the ferry 110. Negotiations are made on the presence or absence of communication authority (step S103). If it is determined by the negotiation that the own node 120 does not have the authority to communicate with the ferry 110 (NO in step S104), the communication availability negotiation unit 122 returns to step S101, and the ferry 110 is located at a specific point in the area. The arrival of the next scheduled time to arrive at is monitored. On the other hand, if it is determined that the own node 120 has the authority to communicate with the ferry 110 through the negotiation (YES in step S104), the communication availability negotiation unit 122 notifies the data exchange unit 123 accordingly.

  Upon receiving the above notification, the data exchange unit 123 reads the ferry addressed data 1241 from the data storage unit 124 and transmits it to the ferry 110 through the communication unit 121 (step S105). In addition, when the data exchange unit 123 subsequently receives data from the ferry 110 through the communication unit 121, the data exchange unit 123 stores the data in the data storage unit 124 as data 1242 (step S106).

  When the data exchange unit 123 finishes the data exchange operation, the communication availability negotiation unit 122 returns to step S101 and monitors the arrival of the next scheduled time when the ferry 110 arrives at the specific point.

  Referring to FIG. 5, the data exchange unit 113 of the ferry 110 monitors whether or not data has been received from the node 120 (step S111). Then, when the data exchange unit 113 receives data transmitted from a certain node 120 through the communication unit 111, the data exchange unit 113 stores the received data as received data 1122 in the data storage unit 112 (step S112). Subsequently, the data exchange unit 113 reads the node-addressed data 1121 from the data storage unit 112, and transmits the node-addressed data 1121 to the node 120 that is the transmission source of the received data through the communication unit 111 (step S113). Then, the data exchange unit 113 returns to step S111 and monitors reception of data from the other nodes 120.

  FIG. 6 is a schematic diagram showing the positional relationship between the ferry 110 and the node 120 in the area 140 when the ferry 110 reaches the point B1 of the area 140 at the scheduled time t1. In this example, among the seven nodes moving in the area 140, five nodes 120-1 to 120-5 exist at a location within a certain distance from the point B1, and the remaining two nodes 120-6, 120-7 does not exist in a place within a certain distance from the point B1. Now, assuming that the threshold value that determines the maximum number of nodes 120 that can communicate with the ferry 110 is 3, for example, among the five nodes 120, negotiation is performed as to which node has the authority to communicate with the ferry 110. . As a result of this negotiation, for example, it is determined that three nodes 120-1, 120-2, and 120-3 have authority to communicate with the ferry 110, and the remaining two nodes 120-4 and 120-5 are determined. Is determined not to have the authority. Then, data exchange is performed between the ferry 110 and the three nodes 120-1 to 120-3.

  As described above, according to the present embodiment, when the ferry 110 moves into the areas 140 and 150, even if there are many nodes 120 within the wireless communicable range of the ferry 110, It is possible to prevent the occurrence of flatting.

  The reason is that each node 120 has its own node 120 at a certain distance from the specific position when the scheduled time of arrival of the ferry 110 at the specific position in the area of the own node is reached. In order to limit the number of nodes 120 having authority to communicate with the ferry 110 to a threshold value or less, the node 120 negotiates with other nodes 120 whether or not any node 120 has authority to communicate with the ferry 110, and the own node has communication authority. This is to perform data exchange communication with the ferry 110 only in the case of

  In the present embodiment, data exchange between the ferry 110 and the node 120 has been described. However, data exchange may be performed between a plurality of nodes 120 moving in the area. For example, the data exchange unit 123 of each node 120 may exchange possessed data with other nodes 120 using, for example, an epidemic method described in Non-Patent Document 2. As a result, the node 120 that could not exchange data with the ferry 110 can exchange data with the ferry 110 through another node 120 that exchanged data with the ferry 110.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  First, an outline of the present embodiment will be described. DTN includes characteristic technical elements for information exchange / distribution methods such as storage, transportation and transfer, but it does not include technical elements such as efficient information transfer and information transfer methods considering immediacy. Not. This part is an application technology using DTN, and is premised on examination at the application layer. For example, as shown in FIG. 7, when information is exchanged with all the nodes in the area or all the nodes that the ferry encounters, the traffic in the area increases (a phenomenon similar to a broadcast storm occurs), and the ferry is flushed. There is a possibility that congestion will occur due to collisions caused by simultaneous communication. In addition, it affects the overall lap time of the ferry that circulates between areas, causing problems in the efficiency and immediacy of information transmission. In the present embodiment, such a problem is solved.

  In the present embodiment, there are a communication terminal (referred to as a ferry) mounted on a mobile that circulates in a specific area at a fixed time, and an in-area node group that exchanges information with the ferry when the ferry approaches the area. . In this embodiment, as shown in FIG. 8, the nodes that exchange information with the ferry are limited, and only a plurality of designated nodes in the communicable range (here, the radius is 50 m centered on the ferry) are the ferry. A method for exchanging information. As a result, the traffic load in the area can be reduced, the redundancy of information to be transmitted can be eliminated, the ferry restraint time for information transmission in each area is reduced, and the efficiency of information transmission is improved.

  Hereinafter, the configuration and operation of the present embodiment will be described in detail.

  Referring to FIG. 9, a communication terminal (node) 1 according to this embodiment includes a data reception processing unit 2, a data transmission processing unit 3, a GPS 4, a data storage unit 5, an area information storage unit 6, and a node. It has a selection processing unit 7 and a DTN function 8. This node 1 functions as an in-area node.

  The data reception processing unit 2 receives information from other communication terminals. The information here includes information such as position information of other nodes, Janken results, Janken tournament information, and data received from the ferry. The data transmission processing unit 3 transmits information to the outside. The information here includes information such as position information of the own node, Janken results, Janken tournament information, and data to be transmitted to the ferry.

  The GPS 4 detects the coordinate position (latitude, longitude, altitude) of its own node. The data storage unit 5 stores arbitrary data to be transmitted. The area information storage unit 6 stores and holds the information received by the data reception processing unit 2. The node selection processing unit 7 performs a process of narrowing down the nodes that communicate with the ferry from the data held in the area information storage unit 6. The narrowing-down process here refers to determining a node having the right to communicate with the ferry from the positional relationship with the ferry, the janken, and the result of information priority comparison.

  Next, the operation of the communication terminal 1 according to this embodiment will be described.

(1) Operation example 1
First, a description will be given of a case where the nodes that can communicate with the ferry are narrowed down based on the proximity of the straight line distance to the ferry position information using the node position information.

  FIG. 10 shows the upper N in the ferry communicable range when the ferry arrives at a specific position in the area (for example, a radius of 50 m around the ferry), and the ferry arrival coordinate position and the node coordinate position are close by a linear distance. It is explanatory drawing of the method of communicating only with the node (regular number example: 10) of a node. The ferry arrives at a fixed coordinate position at a fixed time. Further, the node 1 knows in advance the arrival time of the ferry, the arrival coordinate position, and the prescribed number. In addition, each node 1 in the area knows in advance the information of other nodes 1 (information for identifying a node: node ID).

  When the arrival time of the ferry is reached, the node 1 acquires its current position by the GPS 4, and calculates the linear distance between the arrival position of the ferry and its own coordinate position by the node selection processing unit 7. Then, the node 1 determines whether the ferry communication range is inside / outside from the calculation result in the node selection processing unit 7, and does not communicate with the ferry if the ferry communication range is out. On the other hand, when within the communicable range, the node 1 broadcasts the straight distance between the ferry and the own node to other nodes by the data transmission processing unit 3. Each node 1 sorts the linear distances from the ferry of each node 1 received by broadcasting in ascending order, and starts communication with the ferry when the own node is in the prescribed number. Nodes that rank higher than the specified number do not communicate. Note that the maximum value of the communicable distance between the nodes 1 is longer than the maximum value of the communicable distance between the node 1 and the ferry.

  FIG. 11 shows a flowchart of a method of narrowing down the nodes that can communicate with the ferry from the proximity of the straight line distance to the ferry position information using the node position information. When the specified time (scheduled time when the ferry arrives at the specific point) is reached, the node 1 executes the processing shown in FIG.

  In the process of step S201, the node 1 itself obtains its own position information from the GPS, calculates the linear distance between the position of the ferry and the position of the own node 1, and the communicable range of the ferry (eg, radius 50 m) It is determined whether it is. If it is outside the communicable range of the ferry, the process of FIG. 11 is terminated. On the other hand, if it is within the communicable range of the ferry, the straight line distance between itself and the ferry is broadcast to all other nodes 1 in the area together with the ID of the own node. And the process of step S202 is performed.

  In the process of step S202, the node 1 receives the information regarding the straight line distance between the ferry from the other node 1 and the other node sent asynchronously as area information and records it in the area information storage unit 6. save. The straight line distance between the node 1 and the ferry is recorded and stored in the area information storage unit 6. The process in step S202 ends after a predetermined time has elapsed from the start of the process in step S202 (eg, 3 minutes), and the process proceeds to step S203.

  In the process of step S203, the area information storage unit 6 that stores the linear distance between the ferry of each node 1 recorded in step S202 is referred to and sorted in order from the shortest linear distance between the node and the ferry. Determine the ranking of the nodes. When the rank of the own node is equal to or less than the prescribed number, the communication enable flag (1) is set to the ID of the own node in the area information storage unit 6 and the process of FIG. If the rank of the own node exceeds the prescribed number, the communication flag (1) is not set and the processing in FIG. 11 is terminated.

  Thereafter, the node 1 with the communicable flag (1) set up exchanges retained data with the ferry.

  Note that the node 1 may exchange stored data with another node 1 that moves in the same area. The information transmission / exchange method between the nodes may be a flatting method that distributes data to all communicable nodes or an epidemic method that replicates data to nodes that are encountered during movement.

(2) Operation example 2
Next, the case where the nodes that can communicate with the ferry are narrowed down by Janken will be described.

  FIG. 12 is an explanatory diagram of a method of determining “Janken” to narrow down nodes that can communicate with the ferry. The information that each node 1 has in advance is the same as that in the first operation example. Each node 1 obtains the current position from the GPS 4 when the arrival time of the ferry is reached, and calculates a linear distance from the arrival position of the ferry. Each node 1 broadcasts its own node ID to other nodes 1 when the linear distance is within the communication range with the ferry. On the other hand, nodes outside the communication range do nothing.

  Each time a broadcast transmitted from another node 1 is received, each node 1 shares the node ID existing in the communicable range by recording the received node ID in the area information storage unit 6. Next, each node 1 prepares tournament information so as to be less than the prescribed number, and multicasts it to nodes within the communicable range. As a result, the tournament information indicating the Janken opponent is shared among the nodes within the communication range. Each node 1 plays with the opponent determined based on the tournament information, and notifies the progress of the tournament to the nodes within the communication range while multicasting the result. Communication with the ferry is started from the node 1 which has won the tournament and finished the battle.

  FIG. 13 shows a flowchart of a method for narrowing down the nodes that can communicate with the ferry by means of Janken. When the predetermined time (scheduled time when the ferry arrives at the specific point) is reached, the node 1 executes the processing shown in FIG.

  When the predetermined time is reached, the node 1 performs the processes of steps S211 and S212 similar to the steps S201 and S202 of FIG.

  After the process of step S212, in the process of step S213, first, the node 1 refers to the area information storage unit 6 that stores the linear distance between the ferry of each node 1 recorded in the process of step S212, and communicates. The IDs of all nodes 1 existing within the possible range are acquired. Next, the node 1 creates a list of node IDs in ascending order of node IDs, creates tournament information so that the number is less than the specified number, and stores it in the area information recording unit 6. Then, the process of step S214 is performed.

  In the process of step S214, the node 1 refers to the tournament information created in the process of step S213, and notifies the other node 1 serving as the opponent of the barge request. The other node 1 that has received the notification of the Janken request refers to the tournament information stored in the area information recording unit 6, returns the competition acceptance notification if it is a notification from the opponent of the own node, and starts Janken. To do. The Janken method is performed by exchanging lists of 10 times of Goo (1), Choki (2), and Par (3). In a state where the nodes share the same list, the hand that the node has made and the hand that has made the zero array of the opponent list are checked in order from the zero array of the list, and the victory or defeat of Janken is determined. The winner is the one with the highest number of wins for the 10 Janken results in the list. If the Janken result is won together with the node ID in the tournament result storage area of the area information recording unit 6, 1 is written, if it is lost, 0 is written, and the tournament result is multicast to the nodes within the communicable range. Here, the number of times in which a match is allowed in one match is 10 times, and if no match is found in both matches, both nodes are lost and the process is terminated. Thereafter, the tournament information is referenced and played repeatedly until the tournament ends. The node 1 that has won at the end of the tournament sets a communicable flag (1) for its own node ID in the area information recording unit 6 and ends the processing of FIG. The losing node 1 ends the processing of FIG. 13 without setting the communication enable flag (1).

  Thereafter, the node 1 with the communicable flag (1) set up exchanges retained data with the ferry.

  Note that the node 1 may exchange stored data with another node 1 that moves in the same area. The information transmission / exchange method between the nodes may be a flatting method that distributes data to all communicable nodes or an epidemic method that replicates data to nodes that are encountered during movement.

(3) Operation example 3
Next, a case where the nodes that can communicate with the ferry are narrowed down based on the information value of the node 1 and the result of Janken will be described.

  FIG. 14 is an explanatory diagram of a method for narrowing down the nodes that can communicate with the ferry by performing the tournament in consideration of the priority of the information held by each node 1 and determining whether or not to perform the Janken. The information held by each node 1 is the same as in the first operation example. Furthermore, in this operation example, the number of information held by the node 1 is limited, and is uniform for all nodes in the area, and a priority score of 1 to 5 is set for each piece of information. Further, in this operation example, each node in the area moves to a predetermined distance (for example, a distance within the maximum communicable length of the ferry) at the scheduled time when the ferry reaches the specific point.

  The difference from the operation example 2 is that, in accordance with the tournament information, the total value information of the value scores of the individual information held is exchanged before the Janken. The score indicating the priority of the information indicates the urgency or importance of the information, and it is assumed that a high one is preferentially passed to the ferry. Node 1 that exchanged the total value of information priorities compares it with its own priority score, and if it is high, it is considered that it has won the game. And proceed with the tournament. Only when the priority scores are the same, the nodes 1 perform the janken and decide to win or lose. The Janken method is the same as in Operation Example 2.

  FIG. 15 is a flowchart of a method for narrowing down the nodes 1 that can communicate with the ferry based on the information value of the nodes 1 and the result of Janken. The node 1 executes the process shown in FIG. 15 at a predetermined time (scheduled time when the ferry arrives at the specific point).

  When the predetermined time comes, the node 1 performs the processes of steps S221 and S222 similar to the steps S201 and S202 of FIG.

  After the process of step S222, in the process of step S223, the same process as step S213 of FIG.

  Next, the node 1 performs the process of step S224. In the process of step S224, the tournament information created in the process of step S223 is referred to, and the information priority exchange request and the individual priority score of the information held are added to the other node 1 that is the opponent of the own node 1. Send the value. The opponent terminal that has received the notification refers to the tournament information, and if it is the opponent of the own node, returns it together with the total value of the priority scores of the individual information holding the acceptance notification. The total value of the priority scores possessed by the own node 1 is compared with the received opponent's priority score. If the own node is larger, the value 1 is set, and if it is smaller, the value 0 is set to the tournament result storage area 6. Is recorded and stored together with the node ID, and the tournament result is multicast to the node 1 within the communicable range. Only when the priority scores are the same, node 1 proceeds to step S225. In step S225, the same soap processing as described in step S214 in the operation example 2 is performed to determine a winner.

  Thereafter, the tournament information is referenced and played repeatedly until the tournament ends. The node 1 that has won at the end of the tournament sets the communicable flag (1) for its own node ID in the area information recording unit 6 and ends the processing of FIG. The losing node 1 ends the processing of FIG. 15 without setting the communication enable flag (1).

  Thereafter, the node 1 with the communicable flag (1) set up exchanges retained data with the ferry.

  Note that the node 1 may exchange stored data with another node 1 that moves in the same area. The information transmission / exchange method between the nodes may be a flatting method that distributes data to all communicable nodes or an epidemic method that replicates data to nodes that are encountered during movement.

  Thus, according to the present embodiment, information can be exchanged between the ferry and a plurality of nodes while suppressing traffic in the area. Furthermore, it is possible to reduce the time required for patrols of ferries that circulate between areas, and the efficiency of information transmission is improved.

  The present invention can be applied to inter-vehicle communication and terminal-to-terminal communication, and can be used particularly for data exchange between a communication terminal moving in a closed area and a communication terminal moving between closed areas.

DESCRIPTION OF SYMBOLS 100 ... Communication system 110 ... Communication terminal (ferry)
120: Communication terminal (node)
121: Communication unit 122 ... Communication availability negotiation unit 123 ... Data exchange unit 124 ... Data storage unit 130 ... Path 140, 150 ... Area

Claims (8)

A communication system comprising: a first communication terminal that moves on a predetermined route; and a plurality of second communication terminals that move within a closed area including the route and that can wirelessly communicate with the first communication terminal. Because
The first communication terminal is
A first wireless communication unit that wirelessly transmits and receives data to and from other communication terminals;
A first data storage unit for storing data to be transmitted to the second communication terminal and data received from the second communication terminal;
A first data exchange unit that exchanges the data through the first wireless communication unit with the second communication terminal existing within a wireless communication range of the own communication terminal;
Each of the second communication terminals is
A second wireless communication unit that wirelessly transmits and receives data to and from other communication terminals;
A second data storage unit for storing data to be transmitted to the first communication terminal and data received from the first communication terminal;
If the communication terminal is within a certain distance from the specific position when the first communication terminal arrives at a specific position on the route in the closed area, In order to limit the number of the second communication terminals having the authority to communicate with the communication terminal to be equal to or less than a threshold, it is possible to determine which of the second communication terminals has the authority to communicate with the first communication terminal. A communication availability negotiation unit that negotiates with the second communication terminal and the second wireless communication unit;
When the communication availability negotiation unit determines that the own communication terminal has authority to communicate with the first communication terminal, the exchange of the data with the first communication terminal through the second wireless communication unit A communication system having a second data exchange unit for performing A method for wirelessly exchanging data between a first communication terminal moving on a predetermined route and a second communication terminal moving in a closed area including the route,
When the second communication terminal arrives at a scheduled time when the first communication terminal arrives at a specific position on the route in the closed area, the own communication terminal exists within a certain distance from the specific position. If so, any of the second communication terminals communicates with the first communication terminal in order to limit the number of the second communication terminals having authority to communicate with the first communication terminal to a threshold value or less. Whether or not it has authority to negotiate with the other second communication terminal by radio,
When the second communication terminal determines that the own communication terminal has an authority to communicate with the first communication terminal by the negotiation, the second communication terminal exchanges data with the first communication terminal by radio. Data exchange method. A second communication terminal that moves within a closed area including the route of the first communication terminal that moves on a predetermined route and is capable of wireless communication with the first communication terminal;
A wireless communication unit that transmits and receives data to and from other communication terminals wirelessly;
A data storage unit for storing data to be transmitted to the first communication terminal and data received from the first communication terminal;
If the communication terminal is within a certain distance from the specific position when the first communication terminal arrives at a specific position on the route in the closed area, In order to limit the number of the second communication terminals having the authority to communicate with the communication terminal to be equal to or less than a threshold, it is possible to determine which of the second communication terminals has the authority to communicate with the first communication terminal. A communication availability negotiation unit that negotiates with the second communication terminal and the second wireless communication unit;
Data that exchanges the data with the first communication terminal through the wireless communication unit when the communication availability negotiation unit determines that the own communication terminal has the authority to communicate with the first communication terminal. A communication terminal having an exchange unit. In the negotiation, the communication availability negotiation unit of each of the second communication terminals determines which of the second communication terminals based on the distance between each of the second communication terminals and the specific position at the scheduled time. The communication system according to claim 3, wherein it is determined whether or not two communication terminals have authority to communicate with the first communication terminal. The communication availability negotiation unit of each of the second communication terminals determines, in the negotiation, which of the second communication terminals has an authority to communicate with the first communication terminal by means of a barge. The communication terminal according to claim 3. The communication availability negotiation unit of each of the second communication terminals is based on the priority of the second data stored in the second data storage unit of each of the second communication terminals in the negotiation. 4. The communication terminal according to claim 3, wherein any one of the second communication terminals determines whether or not it has an authority to communicate with the first communication terminal. The data exchange unit of each of the second communication terminals is stored in the second data storage unit with the other second communication terminal existing within the wireless communication range of the own communication terminal. The communication terminal according to claim 3, wherein the exchanged data is exchanged. A second communication terminal that moves within a closed area including the route of the first communication terminal that moves on a predetermined route and is capable of wireless communication with the first communication terminal, A second communication terminal comprising: a wireless communication unit that transmits and receives data to and from the communication terminal; and a data storage unit that stores data to be transmitted to the first communication terminal and data received from the first communication terminal. Configure the computer
If the communication terminal is within a certain distance from the specific position when the first communication terminal arrives at a specific position on the route in the closed area, In order to limit the number of the second communication terminals having the authority to communicate with the communication terminal to be equal to or less than a threshold, it is possible to determine which of the second communication terminals has the authority to communicate with the first communication terminal. A communication availability negotiation unit that negotiates with the second communication terminal and the second wireless communication unit;
Data that exchanges the data with the first communication terminal through the wireless communication unit when the communication availability negotiation unit determines that the own communication terminal has the authority to communicate with the first communication terminal. Program to function as an exchange unit.

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