JP2014155133A - Network system and communication method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that no consideration is given on optimal adjustment for the overall sensor network, though there is a disclosure on the adjustment of retransmission intervals and the number of retransmission times between communication terminals that are connected one-to-one by wire.SOLUTION: A network system includes a plurality of communication devices interconnected by radio communication. Each communication device includes: a communication unit for data transmission/reception; a communication path management unit for acquiring a communication path and communication performance of another communication device; and a timing management control unit for managing a time slot and for transmitting the time slot to the other communication device through the communication unit.

Description

  The present invention relates to network communication control using various types of wireless communication. In particular, it relates to communication control of an ad hoc network.

  In a multi-hop communication network, communication quality varies due to a complex combination of physical environment variations and communication circuit characteristics. For this reason, the communication time from the data transmission source to the final destination and the frequency of success / failure of communication vary, and it is difficult to maintain a certain accuracy in communication. As a method for improving the communication accuracy in such an environment, the network performance is automatically measured, the retransmission interval and the number of retransmissions are obtained, and the transmission parameter is corrected (see Patent Document 1). As a result, the communication is maintained with a certain accuracy even when the communication quality varies.

JP-A-6-252978

  In the sensor network, in order to acquire sensor information from a large number of communication terminals within a certain period of time, data is transmitted at a transmission timing assigned to each communication terminal. In addition, a fluctuation in communication quality is expected, and a margin is provided in advance for the transmission timing and the number of retransmissions. For example, the data transmission success rate is improved by setting a larger number of retransmissions or changing the transmission timing at random.

  However, it is not sufficient to change the transmission timing and the number of retransmissions in the sensor network. This is because the sensor network obtains data from a large number of communication terminals within a certain period of time, so there is no infinite time margin. The data collection frequency in the sensor network and the data transmission interval from the center change dynamically depending on the application and service request. It is necessary to change the transmission timing and the number of retransmissions following such a change.

  Patent Document 1 discloses the adjustment of the retransmission interval and the number of retransmissions between one-to-one communication terminals connected by wire, but under the above conditions, optimal adjustment is performed for the entire sensor network. Is not considered.

  In order to solve the above-described problem, the present invention includes a plurality of communication devices connected to each other by wireless communication, and each of the communication devices includes a communication unit that transmits and receives data, and another communication device. A communication path management unit that acquires the communication path and communication performance; and a timing management control unit that manages the time slot and transmits the time slot to another communication device through the communication unit.

  In a preferred embodiment, the communication management server is connectable to the network to which the ad hoc network communication device belongs, and needs to acquire the communication performance of the communication control unit that transmits and receives data and all the ad hoc network communication devices. A transmission timing calculation management unit that calculates an appropriate time slot, a transmission data calculation management unit that calculates an appropriate transmission data amount from the transmission data amount and necessary time slot of all ad hoc network communication devices, A system state management operation unit that determines and controls whether to perform communication is provided.

  In addition, the transmission timing calculation management unit may determine the number of time slots to be distributed to the communication device based on a predetermined condition.

  At this time, as a predetermined condition, the number of time slots may be determined based on a communication success rate between a communication device that distributes time slots and a predetermined communication device that receives data.

  Also, as a predetermined condition, if all transmissions are completed within a specified time, when time slots are allocated, if the communication performance is low, more time slots are allocated than when the communication performance is high. You may make it do.

  As a result, in data collection by wireless multi-hop, even if the communication success rate increases or decreases, data can be reliably acquired.

  In a preferred embodiment, the transmission data calculation management unit may determine the amount of transmission data transmitted by the communication device based on a predetermined condition.

  At this time, as a predetermined condition, after allotting the time slot, if all data does not finish transmission within the specified time, the amount of data to be transmitted is reduced, and all data is transmitted within the specified time. The amount of data that can be transmitted may be limited.

  Also, as a predetermined condition, if transmission of all data is not completed within the specified time, the data to be transmitted is distributed to another time, and the data amount and communication timing are adjusted so that only the minimum necessary data can be transmitted. May be.

  Thereby, in data collection by wireless multi-hop, even if the communication success rate increases or decreases, necessary data can be reliably acquired.

  In a preferred embodiment, the system management operation unit, the transmission data calculation management unit, and the transmission timing calculation management unit may determine the type of data to be transmitted and the number of time slots based on predetermined conditions.

  At this time, as a predetermined condition, if there is priority data transmission that may omit normal data transmission, such as when updating firmware at the same time, the required transmission data amount is calculated and time slots are allocated based on communication performance. May be.

  As a result, necessary data can be transmitted even if the communication success rate increases or decreases in data transmission that is prioritized as a system.

  ADVANTAGE OF THE INVENTION According to this invention, according to a radio | wireless communication environment, the parameter of a network can be adjusted and an optimal network can be constructed | assembled.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is a configuration example of an ad hoc network communication system. It is an example of an ad hoc network communication route table. It is an example of a transmission data management table. It is an example of a transmission timing table. It is an example of a communication path table. It is an example of a transmission timing management table. It is an example of a transmission data management table. It is an example of the ad hoc network which concerns on an Example, network topology, and a time slot. It is an example of the flowchart which shows the process outline | summary of the communication management server and the whole communication apparatus. It is an example of the time slot distribution method considering communication performance. It is an example of the distribution method of the time slot which considered the system state.

  Hereinafter, an ad hoc network communication system according to an embodiment of the present invention will be described with reference to the drawings.

  The ad hoc network is one of network construction methods mainly using various wireless communications. An ad hoc network is a network configured by autonomously connecting communication devices without requiring a dedicated base station or router. Ad hoc networks often do not require routing settings and the like in routers, wireless communication devices, etc., as compared to infrastructure networks.

  In an ad hoc network, when communication devices exist in a place where wireless communication does not reach each other, the communication devices cannot directly transmit and receive data. Therefore, in an ad hoc network, generally, a communication device that exists within a wireless reachable range serves as a relay, and performs multi-hop communication that transfers data like a so-called bucket relay.

  A sensor network is generally constructed by an ad hoc network, and a large number of devices (several hundreds or more) equipped with sensors collectively collect sensing data measured by each device (hereinafter referred to as “data collection device”). )). The sensor network is mainly used in a system that collects data from a large number of communication devices belonging to a predetermined network within a predetermined time. Specifically, it is used for a remote monitoring system such as a factory or a building, a smart grid system, a system for monitoring various states of a house, and the like.

  When the above-described ad hoc network is used, it is easy to construct a network composed of a large number of communication terminals in units of several hundred units, such as a sensor network. On the other hand, when such a large number of communication terminals are in a network environment where the communication band is narrow and the communication speed is low, a transmission timing control method such as TDMA (Time Division Multiple Access) is applied to transmit communication data between the communication terminals. The timing will be adjusted.

  Before describing the system configuration of the first embodiment, an outline of the present embodiment will be described.

  FIG. 8 is an example of a network topology of the ad hoc network according to the first embodiment. Here, an outline of the operation of the ad hoc network according to the present embodiment will be briefly described. The network topology is a logical communication path for data, and is different from a communication path physically connected by wireless or wired communication.

  The sensor network can be configured with a tree-type network topology as shown in FIG. For example, in FIG. 8A, it is assumed that a communication device 801 (GW) is a data collection device or a gateway (hereinafter “GW”) device for another network. Data collected by the communication device 804 (C) using a sensor or the like is transmitted to the communication device 801 (GW) via the communication device 803 (B). Hereinafter, the communication device 801 (GW) is the communication device (GW), the communication device 802 (A) is the communication device (A), the communication device 803 (B) is the communication device (B), and the communication device 804 (C). May be abbreviated as a communication device (C).

  Each time slot is assigned a number and is executed in the order of the assigned number. As shown in FIG. 8A, time slots are allocated to the communication devices (GW) to (C).

  In the example shown in the figure, the communication device (GW) does not have any time slot for wireless transmission because the communication media for transmitting data to the host server is different. The communication device (A) located immediately below the communication device (GW) has three time slots (1), (2), and (3). The communication device (B) located immediately below the communication device (GW) and having the communication device (C) immediately below has six time slots (4) (5) (6) (10) (11) (12) Have

  The communication device (C) located immediately below the communication device (B) has three time slots (7), (8), and (9).

  The time slot number indicates the transmission timing from the reference time. Each communication device (GW) to (C) shares a reference time. When the time corresponding to the number of the held time slot comes, each communication device (GW) to (C) transmits the data (measurement data) held so far to the higher-level communication device. The final destination of the data is the communication device (A).

  The host communication device viewed from the communication device (C) is the communication device (B).

  When the time corresponding to the time slot (1) arrives, the communication device (A) can transmit data to the communication device (GW). At the time corresponding to the time slots (2) and (3), the communication device (A) can retransmit the same data when transmission to the upper communication device (GW) fails. Similarly, when the time corresponding to the time slot (4) arrives, the communication device (B) can transmit data to the communication device (GW). At the time corresponding to the time slots (5) and (6), the communication device (B) can retransmit the same data when transmission to the upper communication device (GW) fails.

  When the time corresponding to the time slot (7) arrives, the communication device (C) can transmit data to the communication device (B). At the time corresponding to the time slots (8) and (9), the communication device (C) can retransmit the same data when the transmission to the upper communication device (B) fails.

  When the time corresponding to the time slot (10) arrives, the communication device (B) can transmit the data of the communication device (C) to the communication device (GW). At the time corresponding to the time slots (11) and (12), the communication device (B) can retransmit the same data when transmission to the upper communication device (GW) fails.

  More specifically, for example, the data collected by the communication device (C) is transmitted to the communication device (B) at the timing of the time slot (7) 812 shown in FIG. 8B. The communication device (B) transfers the data received from the communication device (C) to the communication device (GW) at the timing of the time slot (11) 813.

  Thereby, the data which the communication apparatus (C) collected with the sensor etc. can be transmitted to a communication apparatus (GW).

  In this example, retransmission time slots are prepared, but it is not necessary to prepare retransmission time slots. In addition, a time slot that is already retransmitted in one time slot may be included.

  In this specification, in the logical network, the data collection device (GW) side is referred to as upstream, and the end side (C) of the tree is referred to as downstream.

  Here, for example, since the communication speed between the communication devices of the sensor network is about 4.2 kbps, it is considerably slower than a wireless LAN (Local Area Network) or the like. Therefore, in the sensor network, the time interval of one time slot is set to about 500 msec. In addition, said numerical value is an illustration for description, Comprising: The range of this invention is not limited.

  FIG. 1 is a configuration example of an ad hoc network communication system according to an embodiment of the present invention. In this communication system, one communication device 100 and the other communication device 101 constitute a wireless ad hoc network. Hereinafter, the communication device 100 will be mainly described. The communication device 100 is connected to one server 140 via one network network 130, and is also connected to the other server 141 via the other network network 131.

  When viewed from the ad hoc network side, the network networks 130 and 131 are different networks from the ad hoc network. The network networks 130 and 131 are, for example, a mobile phone communication network, an optical line network, or a public wireless LAN network.

  The communication apparatus 100 includes a CPU (Central Processing Unit) 111, a memory 112, and a storage unit 114. Various programs included in the communication device 100 are stored in the storage unit 114, and are read and executed by the CPU 111 via the memory 112 as necessary. The communication device 100 is connected to network networks 130 and 131 via a communication unit 113.

  The communication unit 113 includes a first communication interface for performing ad hoc network communication with another communication device 101 and a second communication interface for connecting to the network networks 130 and 131. The communication unit 113 performs various communication controls such as selection of the network networks 130 and 131, disconnection from the network networks 130 and 131, packet transmission / reception, communication availability determination, and traffic volume measurement via the first communication interface. . Further, the communication unit 113 may use, for example, a wireless LAN ad hoc mode, specific low power wireless communication, or a dedicated network device as a second communication interface for performing ad hoc network communication.

  In the storage unit 114, a communication control unit 115, an ad hoc network control unit 116, a transmission data management control unit 121, and a transmission timing management control unit 117 are stored as programs. In addition, an ad hoc network communication path table 118, a transmission data management table 119, and a transmission timing management table 120 used for various controls are stored as data.

  The transmission data management table 119 is a table for managing the transmission data amount. The transmission data management table 120 manages the data type and the amount of data to be transmitted at once based on the data type. Data type refers to the type of data that the communication device 100 transmits to the communication management server 140 and other communication devices 101, sensor information, path control information, communication performance information, instruction information from the communication management server, and firmware update information. Etc. The transmission data management table 119 corresponds to the transmission data management control unit 121.

  The transmission timing management table 120 is a table for managing transmission timing. The transmission timing management table 119 manages time slots. The time slot indicates information related to the timing at which the communication apparatus 100 transmits data collected by a sensor or the like to another communication apparatus 101. The transmission timing management table 120 corresponds to the transmission timing control unit 117.

  The communication control unit 115 controls communication with the communication management servers 140 and 141 via the network networks 130 and 131. A communication protocol used for communication control is, for example, TCP / IP. However, other communication protocols may be used.

  The ad hoc network communication control unit 116 is in charge of communication control when an ad hoc network is constructed. The ad hoc network communication control unit 116 uses other routing protocols such as AODV (Ad hoc On-Demand Distance Vector) or OSLR (Optimized Link State Routing Protocol) to detect other communication devices 101 and Perform construction.

  The transmission data management control unit 121 acquires from the communication management server 140 the data type and the amount of data to be transmitted at once based on the data type through the communication unit 113. The acquired data type and the amount of data to be transmitted at once based on the data type are stored in the transmission data management table 119. The transmission data management control unit 121 processes the corresponding data into a prescribed data amount based on the data type and the data amount to be transmitted at once based on the data type, and transmits the data to the other communication device 101.

  The transmission timing management control unit 117 acquires a time slot from the communication management server 140 through the communication unit 113. The acquired time slot is stored in the transmission timing management table 120. The transmission timing management control unit 117 transmits data to another communication apparatus 101 based on the transmission timing described in the time slot.

  In this embodiment, the communication control unit 115, the ad hoc network control unit 116, the transmission data management control unit 121, and the transmission timing management control unit 117 are stored as programs in the storage unit 114 and executed by the CPU 111. Instead, at least a part of these functions may be realized by a dedicated hardware device.

  The communication management server 140 includes a CPU 151, a memory 152, and a storage unit 154. Various programs included in the communication management server 140 are stored in the storage unit 154 and read and executed by the CPU 151 via the memory 152 as necessary. The communication management server 140 further includes a communication unit 153 and is connected to the network 130.

  The communication unit 153 performs various communication controls such as selection of the network networks 130 and 131, disconnection from the network networks 130 and 131, packet transmission / reception, communication availability determination, and traffic volume measurement.

  In the storage unit 154, a communication control unit 155, a transmission timing calculation management unit 157, a transmission data calculation management unit 159, and a system state management operation unit 161 are stored as programs. Further, a communication path table 156, a transmission timing management table 158, a transmission data management table 160, and a database 162 used for various controls are stored as data.

  The communication control unit 155 generates a communication path table 156. Further, the communication control unit 155 performs communication control when communicating with other devices via the network 130.

  The transmission timing calculation management unit 157 confirms the optimality of the communication performance information acquired from the communication device 100 and the like in cooperation with the system state management operation unit 161. After confirmation, the number of time slots for each communication device is calculated, and a transmission timing management table 158 is generated. Information in the transmission timing management table 158 is transmitted to each communication device via the communication control unit 155.

  The transmission data calculation management unit 159 calculates the transmission data amount for each data type in cooperation with the communication performance information acquired from the communication device 100, the system state management operation unit 161, and the communication timing calculation management unit 157. Then, the transmission data management table 160 is generated. Information in the transmission timing management table 160 is transmitted to each communication device via the communication control unit 155.

  The system state management operation unit 161 acquires sensor information and system status acquired from the communication device 100 and records them in the database 160. The system state management operation unit 161 determines what communication data the ad hoc network system currently requires, what communication should be prioritized, and whether state control is necessary, and the like, and the transmission data calculation management unit 159 and the transmission The information is provided to the timing calculation management unit 157.

  The program may be stored in advance in the storage unit 154, or may be acquired via a storage medium or a communication network and stored in the storage unit 154 as necessary.

  The transmission timing calculation management unit 157 may determine the number of time slots to be distributed to the communication device 100.

  For example, the number of time slots may be determined based on the communication success rate between the communication device 101 that distributes time slots and the predetermined communication device 100 that receives data.

  Also, if all transmissions are completed within a specified time, when distributing time slots, if communication performance is low, more time slots may be distributed than when communication performance is high. Good.

  The transmission data calculation management unit 159 may determine the amount of transmission data that the communication apparatus 101 transmits.

  For example, after allotting the time slot and not transmitting all data within a specified time, the amount of data to be transmitted can be reduced and all data can be transmitted within a specified time. The amount of data may be limited.

  The transmission data calculation management unit 159 and the transmission timing calculation management unit 157 can distribute the data to be transmitted to another time so that only the minimum necessary data can be transmitted if the transmission of all the data is not completed within the specified time. The data amount and communication timing may be adjusted.

  The system state management operation unit 161, the transmission data calculation management unit 159, and the transmission timing calculation management unit 157 may determine the type of data to be transmitted and the number of time slots.

  For example, in the case of simultaneous update of firmware or the like, normal data transmission may be omitted, and if there is priority data transmission, a necessary transmission data amount may be calculated and time slots may be allocated based on communication performance.

  Note that details of processing related to the system state management operation unit 161, the transmission data calculation management unit 159, and the transmission timing calculation management unit 157 will be described later.

  FIG. 2 is an example of the ad hoc network communication path table 118. The ad hoc network communication path table 118 manages the configuration and state of the ad hoc network communication path. The ad hoc network communication route table 118 holds a communication device name 201, a link state 202, a rank 203, and a communication quality 204.

  The communication device name 201 is information for identifying a communication device belonging to an ad hoc network. The link state 202 is information indicating whether or not communication is possible and the state. The rank 203 is information indicating how far the communication apparatus is as a network from the communication apparatus 801 (GW) when each communication apparatus is a communication management server or a tree topology as shown in FIG. The communication quality 204 is a value obtained by indexing the communication quality with the peripheral device. The ad hoc network communication path table 118 is used when a network topology is constructed using a routing protocol such as OSLR or RPL. The ad hoc network communication path table 118 can be created by exchanging information such as the communication state and the number of hops between communication devices constituting the ad hoc network.

  FIG. 3 is an example of the transmission data management table 119. The transmission data management table 119 manages information on what type of data is transmitted by all communication terminals including the communication terminal 100 according to the time zone. The transmission data management table 119 holds a start time 301, an end time 302, a data type 303, and an allowable data amount 304.

  The start time 301 indicates the start time of the time when data of the data type specified by the data type 303 is transmitted. The end time 302 indicates the same end time. The allowable data amount 304 indicates the maximum value of the data amount transmitted at a time.

  FIG. 4 is an example of the transmission timing management table 120. The transmission timing management table 120 manages information on when and what type of data the communication terminal 100 should transmit. The transmission timing management table 120 holds a start time 401, an end time 402, a data type 403, and a retransmission count 404.

  The start time 401 indicates the start time at which the communication terminal 101 transmits data of the data type specified by the data type 403. The end time 402 indicates the end time. The number of retransmissions 404 indicates the maximum number of times that data can be retransmitted when it is determined that the transmission partner has not been reached when data is transmitted.

  FIG. 5 is an example of the communication path table 156. The communication path table 156 manages the configuration and state of communication paths of the communication terminal 100 included in the communication management server 140. The communication path table 156 holds the final transmission destination 501, the next transmission destination 502, the terminal type 503, and the reached hop count 504.

  The final transmission destination 501 is information for identifying communication devices belonging to the ad hoc network and devices belonging to the network networks 130 and 131, and the destinations to which the communication devices 100 and 101 and the communication management servers 140 and 141 transmit data. Represents. The next transmission destination 502 is the information that identifies the communication apparatus belonging to the ad hoc network and the apparatus belonging to the network 130, 131, etc. This is information indicating whether data should be transmitted to the communication device. The terminal type 503 represents the device type of the communication device name 501. The number of hops reached 504 indicates that a communication device belonging to an ad hoc network can be connected to the network networks 130 and 131 and the like, and how many times communication from the communication device can be performed to transmit data to the communication terminal.

  FIG. 6 is an example of the transmission timing management table 158. The transmission timing management table 158 manages the communication quality of the communication apparatuses 100 and 101 included in the communication management server 140 and the communication time required there. The transmission timing management table 158 holds a transmission device name 601, a reception device name 602, a communication quality 603, and a necessary slot number 604.

  The transmission device name 601 is information for identifying a device that transmits data among communication devices belonging to the ad hoc network. The receiving device name 602 is information for identifying a device that receives data transmitted from the transmitting device name 601 by the communication device. The communication quality 603 is an index of the communication success rate when data is transmitted between the transmission device name 601 and the reception device name 602. The necessary slot number 604 holds the number of time slots necessary until an index value for determining that communication is successful when data is transmitted between the transmitting device name 601 and the receiving device name 602. For example, if the index value for determining successful communication is 0.99, and transmission is performed once in one time slot, and if the communication success rate is 0.95, it will be 0.99 if one retransmission is performed. . In this case, the time slot is 2.

  FIG. 7 is an example of the transmission data management table 160. The transmission data management table 160 manages what type of data is transmitted to which communication terminal by the communication terminals 100 and the like. The transmission data management table 160 holds a transmission device name 701, a reception device name 702, a data type 703, and a data amount 704.

  The transmission device name 701 is information for identifying a device that transmits data among communication devices belonging to the ad hoc network. The receiving device name 702 is information for identifying a device that receives data transmitted from the transmitting device name 601 in the same communication device. The data type 703 is information indicating the type of data transmitted by the transmission device name 701. A data amount 704 represents a single data amount transmitted by the transmission device name 701.

  FIG. 8 is an example of the network topology, transmission schedule, and time slot of the ad hoc network according to the present embodiment.

  FIG. 8A shows an example of a network topology, which includes four communication devices (A) 802, a communication device (B) 803, a communication device (C) 804, and a communication device (GW) 801. The communication device is configured. The communication device (GW) 801 can communicate with each other between the communication device (A) 802 and the communication device (B) 803. The communication device (B) 803 can communicate with the communication device (C) 804. On the other hand, the communication device (GW) cannot communicate directly with the communication device (C) 804. It is a network topology having a tree structure with a communication device (GW) as a vertex.

  FIG. 8B is an example of the entire transmission schedule. The entire transmission schedule is divided by a specific time as one unit, and the specific time is further divided by the content to be transmitted. For example, if the time of one unit is 30 minutes, the first half 15 minutes of that is the data collection frame 821 and the latter half 15 minutes is the free communication frame 822.

FIG. 8C is an example of a time slot. In this example, the communication device (A), the communication device (B), and the communication device (C) are each assigned three time slots in one data transmission. The communication device (A) is the time slots (1), (2), and (3), the time slot (1) is for normal transmission, and the time slots (2) and (3) are for retransmission. Similarly, time slots (4), (5), and (6) are assigned to the communication device (B), and (7), (8), and (9) are assigned to the communication device (C). Since the data sent by the communication device (C) is relayed by the communication device (B), the time slots (10), (11), and (12) are similarly assigned to the data relayed by the communication device (B). .
FIG. 9 is an example of a flowchart showing an overall processing overview of the communication apparatus and the communication management server. In this example, there are a communication management server, a communication device GW, a communication device A, a communication device B, and a communication device C. Since the communication device GW is connected to the communication management server, in this example, the communication temporary server and the communication device GW are described as having similar functions.

  9 is configured by the network topology, transmission schedule, and time slot shown in FIG.

  First, the communication device A, the communication device B, and the communication device C create an ad hoc network route, measure communication performance with peripheral communication devices, and create an ad hoc network communication route table 118.

  Next, the communication apparatus A transmits communication performance to the communication management server (901). Similarly, the communication device B transmits the communication performance to the communication management server (902). Similarly, the communication device C transmits the communication performance to the communication management server (903). The communication device C transmits the communication performance to the communication management server via the communication device (B) because of the network topology of FIG.

  For the communication performance, the current route information of each communication device may be transmitted, the route information may be transmitted separately, or only when the route information is changed.

  The communication performance may be transmitted periodically by the communication device to the communication management server, or the communication management server may inquire of the communication device, or if the communication performance has changed or the communication schedule is to be changed. You may send or inquire suddenly when there are special circumstances.

  In this example, the communication device performs route creation. However, another device, for example, a communication management server, may create the route for the entire route creation.

  Next, the communication management server determines whether or not the entire time schedule needs to be changed (904). If it is determined that the time schedule needs to be changed (904: Yes), the entire time schedule is changed (905), and the process proceeds to the next step 906. On the other hand, if it is determined that it is not necessary to change the entire time schedule (904: No), the process proceeds to the next step 906.

  When the entire time schedule needs to be changed, for example, when updating the firmware of a communication terminal, if all data transmission is stopped and priority is given to the data transmission schedule of firmware update, the entire ad hoc network is reconstructed. For example, when data of a specific communication device is transmitted with priority. The process for changing the entire time schedule will be described later.

  Next, the communication management server calculates transmission timing (906). As a result of calculating the transmission timing, it is determined whether or not the transmission timing falls within the specified time (907). If it is determined that the time is within the specified time (907: Yes), the process proceeds to the next step 909. If it is determined that it does not fall within the specified time (907: No), the transmission data amount is calculated (908), and the process proceeds to the next step 909.

  For example, if the number of communication devices is too large to communicate within the specified time, and all communication devices cannot communicate with the number of time slots within the specified time, increase the number of retransmissions because the communication performance of each communication device is low. As a result, if all the communication devices cannot communicate with the number of time slots within the specified time, the number of hops from the communication device to the communication management server is large, so a large number of relays are required for one data transmission. As a result, all communication devices cannot communicate with the number of time slots within a specified time. The transmission timing calculation process and the transmission data amount calculation process will be described later.

  Next, the communication management server distributes transmission information (909). The communication device (A), the communication device (B), and the communication device (C) that have received the transmission information set the transmission information (910). An example of the setting result is the transmission data management table 119 and the transmission timing management table 120.

  In the example of the transmission timing management table in FIG. 4, the time of transmission is recorded, but the time slot number may be recorded. The time slot number indicates the transmission timing from the reference time. Each communication device (GW) to (C) shares a reference time.

  Finally, the communication devices (A), (B), and (C) transmit data based on the set transmission information. In this example, data is transmitted in the time slot of FIG. Therefore, first, the communication device (A) transmits data (911). Subsequently, the communication device (B) similarly transmits data (912). Subsequently, the communication device (C) similarly transmits data (913). Based on the network topology of FIG. 8A, data of the communication device (C) is relayed by the communication device (B).

  Screen images in the system implementing this embodiment are shown in FIGS. On the screen, the network topology is displayed, and the current network status and time slot assignment can be confirmed (FIGS. 8A, 10A, and 11A). Further, the communication schedule within the specified time can be visually confirmed, and what type of data, or what purpose and state of communication is performed within the specified time can be visually confirmed (FIG. 8B). ), FIG. 10 (b) and FIG. 11 (b)). In addition, it is possible to visually confirm how the time slots in that case are assigned (FIG. 8C, FIG. 10C and FIG. 11C).

  This screen may be included in the communication management server 140, the communication device 100, or another monitoring device.

  An example of a transmission timing calculation process is shown using FIG. 8 and FIG.

  First, it is assumed that the current ad hoc network is configured with the network topology, transmission schedule, and time slot of FIG.

  The communication management server 140 collects communication performance from the communication devices 100 and 101.

  The collected results are saved in the database 162, and the saved data is called, so that the transmission timing calculation management unit 157 calculates the transmission timings of all the communication devices.

  The communication success rate between the communication device and the communication device can be calculated by the following equation (1).

(1- (error rate) ^ maximum number of transmissions) (1)
The error rate is a value obtained by subtracting the communication success rate from 1. The maximum number of transmissions defines how many times the same packet is retransmitted including the number of retransmissions. In this example, the communication performance value is converted into an error rate, and the communication success rate is calculated.

  In the case of passing through a plurality of communication devices, it can be calculated by calculating a communication success rate between the communication devices and multiplying them.

  For example, the communication success rate from the communication device (C) to the communication device (GW) in the network topology and time slot of FIG. 8 can be calculated by the following equation (2).

(1- (error rate when transmitted from communication device (C) to communication device (B))) ^ 3
X (1- (error rate when transmitted from communication device (B) to communication device (GW))) ^ 3 (2)
Now, as a result of calculating the communication success rate of the above three paths from the communication device (A) to the communication device (GW), from the communication device (B) to the communication device (GW), from the communication device (C) to the communication device (GW), It is assumed that the communication success rate from the communication device (C) to the communication device (B) is low and does not exceed the threshold of the communication success rate.

  If the transmission timing calculation management unit 157 determines that the transmission timing is within the specified time, the transmission timing calculation management unit 157 increases the maximum number of transmissions so as to exceed the threshold of the communication success rate. The time slot is increased by an amount that increases the maximum number of transmissions.

  In this example, the case where the transmission timing calculation management unit 157 determines that it does not fall within the specified time is described in FIG. If the transmission timing calculation management unit 157 determines that the time does not fall within the specified time, the transmission timing calculation management unit 157 confirms the communication success rate of the other communication device.

  In this example, if the communication success rate from the communication device (A) to the communication device (GW) is high and the maximum number of transmissions is 2, the communication success rate threshold is exceeded. The communication from the communication device (C) to the communication device (B) is assumed to exceed the threshold of the communication success rate if the maximum number of transmissions is four.

  The transmission timing calculation management unit 157 sets the maximum number of transmissions required from the communication device (A) to the communication device (GW) twice, and allocates two time slots. On the other hand, the maximum number of transmissions required from the communication device (C) to the communication device (B) is set to 4 times, and time slots for 4 times are allocated.

  A time slot calculated based on the above processing is shown in FIG. The network topology and time schedule are not changed between FIGS. 8A and 8B and FIGS. 10A and 10B.

  In FIG. 10C, the communication device (A) is the time slot (1) (2), the time slot (1) is for normal transmission, and the time slot (2) is for retransmission. The communication device (B) becomes time slots (3), (4), and (5), and the communication device (C) assigns (6), (7), (8), and (9). The time slot (6) is used for normal transmission, and the time slots (7), (8), and (9) and the three time slots are used for retransmission, and a total of four transmission times are secured. Since the data sent by the communication device (C) is relayed by the communication device (B), the time slots (10), (11), and (12) are similarly assigned to the data relayed by the communication device (B).

  Even if the above processing is performed, if the communication timing calculation management unit 157 calculates that the data does not fall within the specified time, the transmission data calculation management unit 159 reduces the amount of data transmitted. By reducing the amount of data, the time slot time is shortened, and the above processing is performed in the shortened time slot, thereby ensuring communication equal to or greater than the communication success rate threshold.

  Further, the amount of transmission data may be reduced depending on the data type. For example, the data collection communication halves the transmission data amount, but the setting information distribution communication does not reduce the data amount.

  Further, the amount of transmission data may be reduced by changing the transmission time zone according to the data type. For example, communication for data collection is always transmitted within a specified time. On the other hand, the communication for distributing the setting information is divided and transmitted within a plurality of specified times.

  Note that the reduction amount of the transmission data amount for each data type and the change of the transmission time zone according to the data type may be defined in advance or may be changed dynamically.

  Further, the communication success rate threshold value may be held in advance by the communication management server 140, may be instructed from another server, or may be directly designated by the user.

  Further, the threshold value of the communication success rate may be changed depending on the data type. For example, the communication for data collection has a communication success rate of 95% or more, and the communication for setting information distribution that needs to be successful as much as possible has a communication success rate of 99% or more.

  When the communication success rate is too low, the communication management server 140 may instruct the communication device 100 to search for another route. Or you may instruct | indicate the route information which can be judged that a communication success rate becomes high.

  An example of processing for changing the entire time schedule will be described with reference to FIGS. 8 and 11.

  First, it is assumed that the current ad hoc network is configured with the network topology, transmission schedule, and time slot of FIG.

  The communication management server 140 collects communication performance from the communication devices 100 and 101.

  The collected results are saved in the database 162, and the saved data is called, so that the transmission timing calculation management unit 157 calculates the transmission timings of all the communication devices.

  In FIG. 8 of this example, it is assumed that data distribution for firmware update is performed in the free communication frame on the transmission schedule of FIG.

  Now, it is assumed that the system state management operation unit 161 determines the operation efficiency of the entire network system and determines that the firmware update process has the highest priority over data collection.

  In this case, the transmission timing calculation management unit 157 for distributing data optimal for firmware update assigns the maximum number of transmissions based on the communication success rate and a time slot based on the maximum transmission number.

  As a result, the entire transmission schedule is as shown in FIG. 11B, and all are changed to the firmware distribution frame within the specified time. Further, although there is no change in the network topology in FIG. 11A, the time slot configuration as shown in FIG.

  In FIG. 11C, the required maximum number of transmissions is determined to be 3 from the communication success rate of the communication device (GW), the communication device (A), and the communication device (B), and the time slots (1), (2) ( 3) Assign.

  Next, since the communication device (C) relays the communication device (C), similarly, it is determined that the required maximum number of transmissions is three from the communication success rate of the communication device (B) and the communication device (C), and the time slot (4) (5) (6) are assigned.

  Similarly, time slots (7), (8), and (9) are assigned to the communication device (GW), and time slots (10), (11), and (12) are assigned to the communication device (B).

  According to the present embodiment, in the ad hoc network, when the communication performance is different, the number of communication transmissions can be changed according to the communication performance. Further, the data amount can be adjusted according to the communication type. For this reason, in this embodiment, necessary data can be reliably communicated in the entire system.

  The above-described embodiments are examples for explaining the present invention, and are not intended to limit the scope of the present invention to the embodiments. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention. For example, the above-mentioned embodiment is described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. It is possible to add, delete, and replace other configurations for a part of the configuration of the embodiment.

  Information in the storage unit 154 and the storage unit 114 can be stored in a storage device such as a memory, a hard disk, an SSD (Solid State Drive), or a storage medium such as an IC card, an SD card, or a DVD.

DESCRIPTION OF SYMBOLS 100, 101 ... Communication apparatus 113 ... Communication part 114 ... Memory | storage part 115 ... Communication control part 116 ... Ad hoc network communication control part 117 ... Transmission timing management control part 118 ... Ad hoc network communication path table 119 ... Transmission data management table 120 ... Transmission timing Management table 121 ... transmission data management unit 130, 131 ... network network 140, 141 ... communication management server 153 ... communication unit 154 ... storage unit 155 ... communication control unit 156 ... communication path table 157 ... transmission timing calculation management unit 158 ... transmission timing Management table 159 ... transmission data calculation management table 160 ... transmission data management table 161 ... system state management operation unit 162 ... database

Claims (10)

A plurality of communication devices connected to each other by wireless communication;
Each of the communication devices includes a communication unit that transmits and receives data,
A communication path management unit for acquiring communication paths and communication performances of other communication devices;
And a timing management control unit that manages the time slot and transmits the time slot to another communication device through the communication unit. The wireless communication is a tree-type ad hoc network,
The ad hoc network includes a communication management device that collects communication performance information transmitted from the plurality of communication devices.
The communication management device determines the number of time slots to be acquired from or distributed to the other communication device based on communication performance with the other communication device, and timing calculation A control unit;
The network system according to claim 1, further comprising: a transmission data calculation management unit that calculates an amount of data to be transmitted for each data type based on communication performance with the other communication device. The timing calculation control unit transmits the determined number of time slots to the plurality of communication devices,
The communication device receives the determined number of timeslots sent from the communication management device;
The network system according to claim 2, wherein when the communication device transmits data to the other communication device, communication is performed based on the determined number of time slots. The transmission data calculation management unit transmits a data amount to be transmitted per time for each data type to the plurality of communication devices,
The communication device receives the amount of data to be transmitted per time for each data type sent from the communication management device,
The network system according to claim 2, wherein when the communication device transmits data to the other communication device, communication is performed based on a data amount to be transmitted once for each data type. The communication management device
A system state management operation unit that determines that firmware update of the plurality of communication devices should be prioritized over data collection from the plurality of communication devices;
A transmission timing calculation management unit that assigns a maximum number of transmissions and a time slot to each of the communication devices for the firmware update when receiving information that should be prioritized for firmware update from the system state management operation unit; The network system according to claim 2. The transmission timing calculation management unit calculates the communication success rate of each communication device from the error rate and the maximum number of transmissions,
If the communication success rate does not meet the predetermined communication success rate threshold and communication falls within a predetermined specified time, increase the maximum number of transmissions and time slot,
The network system according to claim 5, wherein if the communication does not fall within the predetermined specified time, the maximum number of transmissions and the time slot of the other communication device are changed based on the communication success rate of the other communication device. The transmission timing calculation management unit calculates a communication success rate between the first communication device and the second communication device from the error rate and the maximum number of transmissions among the plurality of communication devices,
If the communication success rate does not meet the predetermined communication success rate threshold and communication falls within a predetermined specified time, increase the maximum number of transmissions and time slot,
On the other hand, if the communication does not fit within the predetermined specified time, the maximum number of transmissions and the number of time slots between the third communication device communicating with the second communication device and the communication management device are set. 6. The network system according to claim 5, wherein the number is greater than the maximum number of transmissions and the number of time slots between the first communication device and the second communication device. The communication management device
The number of slots assigned to each communication device, and the topology of the tree-type ad hoc network;
A transmission schedule of the tree-type ad hoc network;
3. The network system according to claim 2, wherein the time slot assignment of each communication device is displayed on one screen. A plurality of communication devices connected to each other by wireless communication transmit and receive data,
Get the communication path and communication performance,
Managing time slots and transmitting the time slots to other communication devices through the communication unit;
Network system communication method. The wireless communication is a tree-type ad hoc network,
The communication management device that is a major element of the ad hoc network collects communication performance information transmitted from the plurality of communication devices,
Based on the communication performance with the other communication device, the number of time slots acquired from the other communication device or distributed to the other communication device, and transmitted once for each data type The network system communication method according to claim 9, wherein the data amount is calculated.

Images