JP5141119B2 - Multi-hop network system - Google Patents

Description

  The present invention relates to a multi-hop network system.

In on-site construction, the use of electronic data is spreading with the spread of CAD (Computer Aided Design). In recent years, the use of construction management systems has begun, and exchanging data created from design books (CAD, etc.) with surveying and heavy equipment construction support systems in the field has also been frequently performed. For this data exchange, a local area network (LAN) in the field (outdoor) is used in consideration of the amount of data to be exchanged.
JP 2005-236598 A

  However, when a wireless LAN is used in a place where infrastructure such as an existing power line cannot be used, such as a civil engineering site, when there is a wide area or an obstacle according to the characteristics of the wireless LAN. It is necessary to install a relay station. Ensuring the power to be supplied to the relay station (by using a battery or solar system when power cannot be taken from nearby) and maintenance require a large amount of labor and cost. However, the data transmitted / received at the civil engineering site includes a lot of measurement data and the like, and the data only needs to be finally delivered to the transmission destination. Therefore, the network need not be always connected. In Patent Document 1, each ad hoc network terminal that holds data periodically transmits data according to data transmission conditions, and the terminal that receives the data becomes a terminal that holds new data. A technique for giving each terminal the role of data transfer by repeating transmission and reception is disclosed.

  The present invention has been made in view of the above problems, and its main purpose is a wireless LAN capable of reliably reaching the destination even if there is a delay in transmission in a place where there is no existing communication infrastructure. It is to realize communication.

In order to solve the above-described problem, the present invention is a multi-hop network system that includes a plurality of nodes and servers, and transfers data from one node to a server directly or via another node. When a node includes a node that moves within a predetermined area, and each node uses at least one of data received from another node and data generated by itself as target data, and the node can communicate with the server. , When the target data is transmitted to the server and communication with the server is not possible, the target data is transmitted to another node, and a connectivity parameter indicating the ease of connection of the other node to the server is set. A storage unit that stores the target data when the target data is transmitted to another node according to the magnitude of the connectivity parameter of the other node; In accordance with the probability, and selects the destination node.
According to this configuration, it is possible to construct a delay-permitted network that does not require constant connection between the transmission source node and the transmission destination node. Then, by changing the data between nodes and increasing the transmission opportunities to the server, the data can be surely reached the server even if the transmission is delayed. In addition, since the destination node is selected according to the probability proportional to the size of the connectivity parameter, the node having the maximum connectivity parameter is not necessarily selected, so that data transmission is concentrated on the node that is easily connected to the server. And load distribution proportional to the magnitude of the connectivity parameter can be achieved.

Further, the present invention is a multi-hop network system in which each node periodically confirms communication with the server, and the connectivity parameter of the storage unit is determined depending on a result of communication enabled or disabled. And periodically confirming communication with another node, receiving the connectivity parameter as a response to the communication confirmation from the other node, and storing it in the storage unit .
According to this configuration, since the transmission destination node is selected based on the connectivity parameter that is a result (experience value) of periodic communication confirmation, the probability that the data reaches the server is improved by using the experience value. be able to.

Further, the present invention is a multi-hop network system, and when each node changes the connectivity parameter, the connectivity parameter is set to be larger than the previous connectivity parameter when communication with the server is possible. When the communication with the server is impossible, the connectivity parameter is set to be smaller than the previous connectivity parameter .
According to this configuration , the connectivity parameter is increased / decreased according to whether communication between the node and the server is possible or not, so that accuracy as an index indicating the ease of connection to the server can be improved. .

Further, the present invention is a multi-hop network system comprising a plurality of nodes and servers, and transferring data from one node directly or via another node to the server , wherein the plurality of nodes have a predetermined area. It includes nodes to move within, each node itself data and received from other nodes and the target data of at least one of the generated data, if itself allowing communications with the server, the said object data When the server itself is unable to communicate with the server, the target data is transmitted to another node, and the transit node address included in the data received from the other node is referred to, and the transit node address is calculating the number of transfers between nodes of the data, this is transmitted as the transfer count is large, the target data at a later time The features.
According to this configuration, it is possible to construct a delay-permitted network that does not require constant connection between the transmission source node and the transmission destination node. Then, by changing the data between nodes and increasing the transmission opportunities to the server, the data can be surely reached the server even if the transmission is delayed. Further, since the transmission of data is delayed as the number of transfers between nodes increases, unnecessary data transmission can be avoided.

The present invention is also a multi-hop network system in which each node has a total size of a predetermined value or less from at least one of data received from other nodes and data generated by itself. Select one or more data, and if the selected data is two or more, after combining those data, the selected data or two or more combined data is the target data To do.
According to this configuration, since the data is selected and combined so that the total value of the data sizes is equal to or less than the predetermined value, the data can be transferred efficiently.

Further, the present invention is a multi-hop network system, and when the server receives the data, the server acquires an address of a transmission source node included in the received data, and uses the address as a transmission destination It is characterized by transmitting arrival confirmation data.
According to this configuration, for the transfer of data from the node to the server, the arrival confirmation data is transmitted from the server to the node, so that the data transmission source node confirms that the data has reached the server. This eliminates the need to keep holding data wastefully.

  In addition, the problems disclosed in the present application and the solutions thereof will be clarified by the column of the best mode for carrying out the invention and the drawings.

  According to the present invention, it is possible to realize wireless LAN communication in which data can surely reach a destination even if transmission is delayed in a place where there is no existing communication infrastructure.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. The multi-network system according to the embodiment of the present invention includes a plurality of nodes and one center server, and includes a node that generates data, transmits the data to the center server, and a center server that receives the data. Even in a state where direct wireless communication is not possible, wireless data transmission / reception is realized by using a node that moves between the data transmission source node and the center server as a relay station. A node serving as a relay station combines data having different occurrence points into one packet and transmits it to another node or center server. In this case, efficient data transfer can be realized by selecting data so that the packet fits in the size calculated from the communication speed and processing time. At this time, if there is no communication partner node, the result of periodic communication confirmation is awaited for the next data transmission.

  There are objects, people, and the like that may move in the predetermined area. The predetermined area is, for example, a civil engineering work site. In this case, various construction machines and workers correspond to “objects and people”. However, the present invention is not limited to civil engineering work sites and can be widely applied. Then, when an object, a person, or the like including the node moves, there is a possibility of wireless communication with a node having data to be transmitted to another node (finally a center server that is a destination). Therefore, a node provided in the mobile body or the like can be used as a relay station.

  In construction management systems used at civil engineering construction sites, PCs (Personal Computers) are installed on heavy machinery, so PCs installed on moving heavy machinery can be used as nodes, and terminals carried by workers It can also be used as a node. It is not always necessary to establish a connection as in an ad hoc network. One relay station transmits data when a wireless communication state is established with another relay station, and the destination (site) Data hopping to the center server in the office).

≪System configuration and overview≫
FIG. 1 is a diagram illustrating a configuration of a multi-hop network system. The multihop network system 1 includes a plurality of nodes 2 and a center server 3. The node 2 has a function of generating data and transmitting it to the center server 3 and a function of relaying data transfer to the center server 3 by transferring data received from another node to another node. As described above, the node 2 is realized by, for example, a PC or a personal digital assistant (PDA) mounted on a heavy machine or the like that sequentially moves on a civil engineering work site (in a predetermined area). Note that the node 2 is a generic term for nodes, and in order to distinguish individual nodes, Ni (i = 1 to n) is used as indicated by the nodes N1, N2,. The center server 3 has a function of receiving, storing, and managing data from the plurality of nodes 2. The center server 3 is realized by a server computer.

  The node 2 transmits message data to the center server 3, and the center server 3 receives the message data from the node 2. As a response to the reception of the message data, the center server 3 transmits the arrival confirmation data to the node 2 that is the transmission source of the message data. When the node 2 receives the arrival confirmation data, one unit of data transfer is completed.

  Data is transferred between the node 2 that generated the data and the center server 3 by wireless communication. However, wireless communication between the node 2 and the center server 3 may not be possible due to wireless characteristics or the like. In the multi-hop network system 1, even if wireless communication between the node 2 and the center server 3 is not possible, data is bucketed to other nodes 2 selected according to the probability of communication with the center server 3. By sequentially transferring in a relay manner, the center server 3 is finally made reachable.

  FIG. 2 is a diagram illustrating a configuration of a node. The node 2 includes a wireless communication unit 21, a sensor 22, a processing unit 23, and a storage unit 24. The wireless communication unit 21 has a function of transmitting and receiving generated data wirelessly. Specifically, it is realized by an antenna or a NIC (Network Interface Card). The sensor 22 has a function of detecting some amount or state and outputting data corresponding to the detection result to the processing unit 23. For example, a GPS (Global Positioning System) device, an accelerometer, a speedometer, a thermometer, a hygrometer, and the like. The processing unit 23 has a function of acquiring data from the sensor 22 and storing the data in the storage unit 24 and a function of arranging the data into a message data format and transmitting the data to other nodes 2 and the center server 3. Specifically, it is realized by a CPU (Central Processing Unit) executing a program stored in a predetermined memory. The storage unit 24 stores data from the processing unit 23 and reads the stored data. Specifically, it is realized by a nonvolatile storage device such as a flash memory or a hard disk device.

  FIG. 3 is a diagram illustrating the configuration of the center server. The center server 3 includes a wireless communication unit 31, a processing unit 32, and a storage unit 33. The wireless communication unit 31 has a function of receiving message data from the node 2 wirelessly and transmitting arrival confirmation data as a response. Specifically, it is realized by an antenna or a NIC. The processing unit 32 has a function of decomposing the message data received from the node 2 into individual message data, storing the data in the storage unit 33, and a function of creating arrival confirmation data corresponding to the source node of each message data. Have. Specifically, it is realized by the CPU executing a program stored in a predetermined memory. The storage unit 33 stores data from the processing unit 32 and reads the stored data. Specifically, it is realized by a nonvolatile storage device such as a flash memory or a hard disk device.

<< Data structure >>
FIG. 4 is a diagram illustrating a configuration of data stored in the storage unit of the node. The storage unit 24 of each node 2 stores message data MD, a server connectivity table 24A, and a connection node table 24B.

  FIG. 4A is a diagram illustrating the configuration of the message data MD. The message data MD includes a transmission destination address MD1, a transit node address MD2, a delimiter MD3, and data MD4. The transmission destination address MD1 indicates the transmission destination address of the message data MD, and is the address of the center server 3 here. The transit node address MD2 is an address of the node 2 through which the message data MD has passed so far. The first address # 1 is the address of the node 2 that generated the data, and the last address #k is the address of the node 2. Therefore, the number of hops of message data MD (the number of transfers between nodes) can be specified by the number of addresses stored in the transit node address MD2 (that is, the value k). Furthermore, by referring to the transit node address MD2, another node may be selected as the transmission destination so that the message data MD is not frequently transferred between the same two nodes. The delimiter MD3 is a symbol for separating the control field including the transmission destination address MD1 and the transit node address MD2 from the data MD4 in the message data MD. The data MD4 is data generated at the node 2 (address # 1) and should be transferred from the node 2 to the center server 3.

  FIG. 4B is a diagram showing the configuration of the server connectivity table 24A. The server connectivity table 24A is a table that stores connectivity parameters for the center server 3 of the node 2 other than the node, and includes a record including the node address 24A1 and the connectivity parameter 24A2. The node address 24A1 is an address of a node 2 other than the node, and may be an IP (Internet Protocol) address of the node 2 or an ID unique to the node 2. The connectivity parameter 24A2 is an index indicating the ease of connection of the node 2 to the center server 3, and is accepted as reply data of the counterpart node when the node 2 performs ping as a periodic communication check. Details of the connectivity parameter will be described later.

  FIG. 4C is a diagram showing the configuration of the connection node table 24B. The connection node table 24B is a table indicating nodes that can communicate with the node 2 at that time, and includes a connection node address 24B1. The connection node address 24B1 stores the address of the node (including each node 2 and the center server 3) that responded when the node 2 pinged as a periodic communication check.

  FIG. 5 is a diagram showing the configuration of the connection node table 33A stored in the storage unit 33 of the center server 3. The connection node table 33A is a table indicating the nodes 2 with which the center server 3 can communicate at that time, and includes a connection node address 33A1. The connection node address 33A1 stores the address of the node 2 that has responded when the center server 3 pings as a periodic communication check.

≪System processing≫
FIG. 6 is a flowchart showing data transfer processing in each node. This process is a basic process executed by each node 2 in order to realize a delay-granting network between the node 2 and the center server 3 for which a constant connection is not guaranteed. Details of each step constituting this process will be described later.

  First, this process is started when data is received from a node 2 (other node) other than the node (S601) or when data is generated at the node 2 (own node) (S602). The combined data is transmitted to the next transfer destination node 2 or center server 3. When data is received from a node 2 other than the node (S601), the received data is stored in the message buffer B1 of the storage unit 24. When data is generated at the node 2 (S602), the generated data is stored in the message buffer B2 of the storage unit 24. Furthermore, depending on the timing and the size of the data, there are cases where data that has not yet been combined or data that has not been transferred to the message buffer B3 remains in the message buffers B1 and B2.

  In this process, first, the node 2 refers to the message buffers B1 and B2, combines them so that the total size of two or more message data is below a predetermined value, and stores the combined message data in the message buffer B3. (S603). One message data may be stored in the message buffer 3 as it is. Next, referring to the connection node table 24B of the storage unit 24, it is determined whether or not communication with the center server 3 is possible based on the presence or absence of the address of the center server 3 (S604).

  If communication with the center server 3 is not possible (N in S604), the node 2 cannot directly send message data to the center server 3, so the node m to which the message data is transferred is selected (S605). Subsequently, as a timing for transmitting message data to the node m, a time interval (transmission interval) T from the present time to transmission is determined (S606). Then, when the elapsed time t from the present time becomes the transmission interval T, the message data is transmitted to the selected node m (S607).

  On the other hand, if communication with the center server 3 is possible in the determination of S604 (Y in S604), the message data can be transmitted to the center server 3 because the node 2 can directly transmit the message data to the center server 3 (S608).

  Note that processing is not necessarily performed according to the flowchart illustrated in FIG. 6. For example, processing for combining message data may be performed until immediately before message data is transmitted to the node m or the center server 3.

FIG. 7 is a diagram illustrating an example of message data combining processing (S603 in FIG. 6). The storage unit 24 of the node 2 is provided with message buffers B1, B2, and B3 for separately storing the message data MD. First, message data M ₁ , M ₂ , M ₃ and M ₄ received from other nodes are stored in the message buffer B ₁ . On the other hand, message data O ₁ , O ₂ , O ₃ and O ₄ generated by the own node are stored in the message buffer B2. Node 2 selects one or more message data within a range in which the total size falls within a predetermined value (10 in the example of FIG. 7), and selects two or more message data. If they are combined, the selected message data or the combined two or more message data are stored in the message buffer B3 as target data.

As a specific example, first, combining the message data _{M 1} and _{O 2,} and stores the target data _{T 1} in the message buffer B3. Then, store the message data _{M 3} as it is as the target data _{T 2} in the message buffer B3. Subsequently, the message data M ₄ and O ₃ are combined and stored in the message buffer B ₃ as target data T ₃ . Furthermore, combining the message data _M 2, _{O 1} and _{O 4,} and stores the target data _{T 4} to the message buffer B3. Since the size of the target data T ₄ is 7, in order to set the size to 10, the transmission of the target data T ₄ is waited until the message data of size 3 is stored in the message buffer B 1 or B 2. Also good.

  For example, when the node N1 receives the message data MD of the destination address MD1 = N4, the transit node address MD2 = N2, the data MD4 = 21, 22 and generates the data 11 and 12, the destination address Message data MD of MD1 = N4, transit node address MD2 = N2, N1, data MD4 = 21, 22, 11, 12 is created and transmitted (not shown). Here, the transit node address MD2 indicates the longest path among the data included in the message data MD. Note that the shortest path may be indicated.

FIG. 8 is a diagram for explaining a method (S605 in FIG. 6) for selecting the next transfer destination node using the connectivity parameter of each node stored as the server connectivity table 24A. The connectivity parameter P ⁽ⁱ⁾ n is a connectivity parameter at the time Tn at the node Ni, and is an index indicating the ease of connection from the node Ni to the center server 3 in particular.

Here, when message data is to be transmitted from the node N1 to the center server 3, the connectivity parameters (P ⁽¹⁾ n, P ⁽²⁾ n, P ⁽³⁾ n, P ^{(4) of} each node. n, P ^{(5) One} of the nodes is selected as a transfer destination according to the probability proportional to the magnitude of n). As an example, if P ⁽¹⁾ n = 10, P ⁽²⁾ n = 5, P ⁽³⁾ n = 20, P ⁽⁴⁾ n = 0, P ⁽⁵⁾ n = 20, node N1 is selected. The probability that node N2 will be selected is 5/55, the probability that node N3 will be selected is 20/55, the probability that node N4 will be selected is 0, The probability that N5 is selected is 20/55. Specifically, for example, random numbers from 0 to 1 are generated. If the random number is 0 or more and 10/55 or less, the nodes N1 and 15/55 are generated if the node N1 is greater than 10/55 and 15/55 or less. If it is larger than 35/55 or less, node N3 is considered, and if it is larger than 35/55 and 1 (= 55/55) or less, node N5 is considered. When the node N1 is selected, the next node selection is performed after waiting for a moment without transmitting message data to other nodes.

  According to this selection method, the node Ni having the maximum connectivity parameter is not necessarily selected. Therefore, excessive concentration on the node Ni that is easily connected to the center server 3 is avoided, and the size of the connectivity parameter is increased. Proportional load distribution can be achieved.

  In FIG. 8, the node N2 can communicate with nodes other than the center server 3. If the center server 3 can communicate with the node N3 or N5, all the nodes can communicate with the center server 3.

  FIG. 9 is a flowchart showing the forwarding node selection process (S605 in FIG. 6). First, the node 2 acquires the node address and the connectivity parameter from the node that has responded to the ping, and stores it in the storage unit 24 as the server connectivity table 24A (S901). In this case, the connection node address 24B1 of the connection node table 24B is updated with the acquired node address. Next, the node to which the message data is transferred is selected according to the probability proportional to the size of the connectivity parameter 24A2 (S902). Details of this selection are as described with reference to FIG. Thus, the transmission destination of the message data is determined (S903).

FIG. 10 is a diagram illustrating a connectivity parameter change process according to whether communication with the center server is possible. This process is performed asynchronously with the process of transferring the data from the node 2 that generated the data to the center server 3 (data transfer process of FIG. 6), and the connection of each node 2 to the center server 3 The degree parameter is updated at any time according to the communication state with the center server 3. Therefore, each node 2 performs communication confirmation (for example, by ping) with the center server 3 every predetermined time (periodically). Note that the connectivity parameter P ^(k) _n (where n is the number of repetitions of a predetermined time) of the node Nk is the connectivity parameter 24A2 for the node address 24A1 of the own node Nk in the server connectivity table 24A of the storage unit 24. Stored. Hereinafter, each change processing example will be described.

In the change processing example 1, the initial value of the connectivity parameter is N (predetermined value), the connectivity parameter when communication with the center server 3 is N (predetermined value), and communication with the center server 3 is not possible The connectivity parameter is a value obtained by subtracting δ from the previous value. If the node 2 can communicate with the center server 3 even once, the connectivity parameter is set to N, and the connectivity parameter of the most recently connected node 2 is the maximum even if it is not connected at all. Based on the idea that Note that the minimum value of P ^(k) _n is 0.

In change processing example 2, the initial value of the connectivity parameter is N (predetermined value), and the connectivity parameter when communication with the center server 3 is possible is a value obtained by adding δ to the previous value. The connectivity parameter when communication is not possible is a value obtained by subtracting δ from the previous value. This is because the larger the number of times that the node 2 can communicate with the center server 3, the larger the connectivity parameter is set, and the longer the connection time to the center server 3 is, the larger the connectivity parameter of the node 2 is. Based on the idea that Note that the minimum value of P ^(k) _n is 0.

  In the change processing example 3, the initial value of the connectivity parameter is 1, and the connectivity parameter when communication with the center server 3 is possible, the previous value is multiplied by a coefficient α (for example, (n + 1) / n) greater than 1. The connectivity parameter when communication with the center server 3 is not possible is a value obtained by multiplying the previous value by a coefficient β (for example, (n−1) / n) that is greater than 0 and less than 1. In the change processing example 1 and the change processing example 2, once the connectivity parameter becomes 0, it is 0 no matter how many times communication is impossible, and the number (frequency) of communication failure is not reflected in the connectivity parameter. In order to solve such a problem, the change processing example 3 reflects the past communication enabled or disabled state in the connectivity parameter.

  FIG. 11 is a flowchart showing data transmission interval determination processing (S606 in FIG. 6). Further, accompanying the processing, a flowchart showing connection node table update processing and interrupt processing is included.

  First, in the transmission interval determination process, the node 2 acquires the transit node address MD2 of the message data MD stored in the message buffer B3 (S1101). As shown in FIG. 4A, the address of the node 2 through which the message data MD passes is sequentially stored in the relay node address MD2. Therefore, the number of transfers (number of hops) between the nodes 2 is calculated from the transit node address MD2 (S1102). Then, the transmission interval T is determined from the number of transfers (S1103). The transmission interval T is a time interval from the present time to transmission. In other words, the message data MD is transmitted after T has elapsed from the present time. The transmission interval T is set larger as the number of transfers (number of hops) between the nodes 2 is larger. For example, the relationship between the number of transfers and the transmission interval T may be stored in a table in advance, and the transmission interval T may be set with reference to this table. This means that a large number of transfers means that it is difficult to connect to the center server 3, so that a transmission interval is kept as long as possible (that is, at a late timing) so that useless data transmission is prevented. Then, it waits for the elapsed time t to reach the transmission interval T (N in S1104). When the elapsed time t reaches the transmission interval T (N in S1104), the transmission interval determination process is terminated. Thereafter, message data is transmitted to the node m (S607 in FIG. 6).

  In each node 2, the connection node table 24B is updated at regular intervals (periodically) asynchronously with data transfer processing (main processing) including transmission interval determination processing. This process is started as a process for a timer interrupt issued every predetermined time, for example. First, communication confirmation such as ping is performed, and the connection node table 24B is updated so as to add other nodes (including other nodes 2 and the center server 3) that have responded as connection node addresses 24B1 (S1111). . Next, it is determined whether or not the connection node address 24B1 has the address of the center server 3 (S1112). If there is an address of the center server 3 (Y in S1112), an interrupt is issued to the main process (S1113). If there is no address of the center server 3 (N in S1112), the process is terminated as it is.

  In the interrupt process activated by interrupting the main process as a result of the interrupt issued due to the presence of the address of the center server 3, the elapsed time t is set to the transmission interval T (S1121). This eliminates the waiting of S1104 in the transmission interval determination process. Next, since communication with the center server 3 is possible, message data is transmitted to the center server 3 (S1122). Then, the interrupt process is terminated and the process returns to the main process.

≪Send confirmation data transmission≫
As a response to the reception of the message data, the center server 3 transmits the arrival confirmation data to the transmission source node of the message data MD (the first node address # 1 of the transit node addresses MD2). The format and transfer method of the arrival confirmation data are basically the same as the message data, and the arrival confirmation data is the target data. The differences are shown below.
(1) The arrival confirmation data is combined only when the transmission destination is the same node.
(2) The next transfer destination node is randomly selected from communicable nodes.
In order to efficiently transmit arrival confirmation data, there are the following methods.
(1) The number of arrival confirmation data is reduced by taking a method of transmitting arrival confirmation data from the center server 3, for example, once per hour.
(2) The arrival confirmation data does not correspond to each received message data, but has a content that allows the received data number to be known, thereby reducing the size (data amount) of the arrival confirmation data. For example, when data from # 1 to # 100 is received, arrival confirmation data having the content “1-100” is transmitted.

  Although the embodiment of the present invention has been described above, in order to make each node 2 and center server 3 in the multi-hop network system 1 shown in FIG. 1 function, a program executed by a processing unit (CPU) is read by a computer. It is assumed that the multi-hop network system according to the embodiment of the present invention is realized by recording on a possible recording medium, causing the computer to read and execute the recorded program. Note that the program may be provided to the computer via a network such as the Internet, or a semiconductor chip or the like in which the program is written may be incorporated in the computer.

  According to the embodiment of the present invention described above, when a wireless LAN is used in a place where infrastructure such as an existing power line is not available, such as a civil engineering site, a relay station is installed on the site. Since it is not necessary to install, the cost is reduced, and the LAN can be easily used in the field (outdoors). Next, since the message data is selected and combined so that the total size is equal to or less than the predetermined value, the message data can be efficiently transferred. Then, the message data can be made to reach the center server 3 surely even at a later time by changing the message data between the nodes 2 and increasing the transmission opportunities to the center server 3.

  According to the above embodiment, since the destination node 2 is selected based on the connectivity parameter that is a result (experience value) of periodic communication confirmation, the accuracy with which the message data reaches the center server 3 is improved. be able to. Further, since the destination node 2 is selected according to the probability proportional to the magnitude of the connectivity parameter, the node 2 having the maximum connectivity parameter is not necessarily selected. It is possible to avoid concentration on the easily connected nodes 2 and to achieve load distribution proportional to the magnitude of the connectivity parameter.

  According to the above embodiment, the connectivity parameter is increased or decreased depending on whether communication between the node 2 and the center server 3 is possible or not, so that the index as an index indicating the ease of connection to the center server 3 can be obtained. The accuracy can be improved. Next, the larger the number of message data transfers, the longer the interval until transmission, so that unnecessary data transmission can be avoided. In response to the transfer of data from the node 2 to the center server 3, the arrival confirmation data is transmitted from the center server 3 to the node 2, so that the message data transmission source node sends the message data to the center server 3. It is possible to confirm that the message has arrived, and there is no need to keep holding the message data wastefully.

<< Other embodiments >>
Although the best mode for carrying out the present invention has been described above, the above embodiment is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and equivalents thereof are also included in the present invention. For example, the following embodiments can be considered.

(1) In the above embodiment, it is described that the node 2 is a PC or a portable information terminal mounted on a heavy machine or the like that sequentially moves on a civil engineering work site. However, the present invention can be applied to other cases. For example, by mounting the node 2 in an elevator or a car, the data transfer may be relayed while appropriately moving in a building where the elevator is installed or in an area where the car travels daily.

(2) In the above embodiment, when the node 2 transmits data to other nodes, the transmission destination is selected according to the probability proportional to the size of the connection parameter of each node. A destination may be selected (according to the same probability).

(3) In the above embodiment, it has been described that when node 2 transmits data to another node, it is transmitted to one node. However, a plurality of nodes (including all communicable nodes) are described. You may make it transmit.

(4) When data transfer is performed so as to loop between specific nodes, the node 2 may select a node other than the specific node as a transmission destination.

It is a figure which shows the structure of a multihop network system. It is a figure which shows the structure of a node. It is a figure which shows the structure of a center server. It is a figure which shows the structure of the data memorize | stored in the memory | storage part of a node, (a) shows the structure of message data, (b) shows the structure of a server connectivity table, (c) shows the structure of a connection node table Indicates. It is a figure which shows the structure of the data memorize | stored in the memory | storage part of a center server. It is a flowchart which shows the transfer process of the data in each node. It is a figure which shows the example of the combination process of message data. It is a figure explaining the system which selects the node of the transfer destination next. It is a flowchart which shows the selection process of a transfer destination node. It is a figure which shows the change process of a connectivity parameter. It is a flowchart which shows the determination process of the transmission interval of data.

Explanation of symbols

1 Multi-hop network system 2 Node 24 Storage unit 24A2 Connectivity parameter 3 Center server (server)
MD message data (data)
MD1 Destination address MD2 Node address via MD4 Data T Transmission interval

Claims (6)

A multi-hop network system comprising a plurality of nodes and servers, and transferring data from one node directly or via another node to the server,
The plurality of nodes include nodes that move within a predetermined area;
Each node
Target data is at least one of data received from other nodes and data generated by itself,
If it is possible to communicate with the server, the target data is transmitted to the server,
If it is impossible to communicate with the server, the target data is sent to another node,
A storage unit for storing a connectivity parameter indicating the ease of connection of the other node to the server;
When transmitting the target data to another node, a destination node is selected according to the probability according to the magnitude of the connectivity parameter of the other node. The multi-hop network system according to claim 1 ,
Each node
Periodically check communication with the server, change the connectivity parameter of the storage unit according to the result of communication enable or disable communication,
A multi-hop network system characterized by periodically confirming communication with another node, receiving the connectivity parameter as a response to the communication confirmation from the other node, and storing it in the storage unit. The multi-hop network system according to claim 2 ,
When each node changes the connectivity parameter,
When communication with the server is possible, the connectivity parameter is set to be larger than the previous connectivity parameter,
The multi-hop network system, wherein when the communication with the server is impossible, the connectivity parameter is set to be smaller than the previous connectivity parameter. A multi-hop network system comprising a plurality of nodes and servers, and transferring data from one node directly or via another node to the server,
The plurality of nodes include nodes that move within a predetermined area;
Each node
Target data is at least one of data received from other nodes and data generated by itself,
If it is possible to communicate with the server, the target data is transmitted to the server,
If it is impossible to communicate with the server, the target data is sent to another node,
Refer to the transit node address included in the data received from other nodes,
Calculate the number of transfers between nodes of the data from the via node address,
The multi-hop network system, wherein the target data is transmitted at a later timing as the number of times of transfer increases. A multi-hop network system according to any one of claims 1 to 4 ,
Each node
Select one or more data from at least one of data received from other nodes and data generated by itself so that the total size is less than or equal to a predetermined value. For example, a multi-hop network system characterized in that after combining these data, the selected data or two or more combined data is used as the target data. A multi-hop network system according to any one of claims 1 to 5 ,
The server
When the data is received, an address of a transmission source node included in the received data is acquired, and arrival confirmation data having the address as a transmission destination is transmitted.

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