JP2015104013A - Radio communications system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communications system capable of reducing the probability of collision of transmission data while establishing a communication channel.SOLUTION: The radio communications system includes plural repeaters 3a-3f having a function to relay radio communications between a slave unit 1 as a transmission source of a measurement data and a master unit 2 as a transmission target of the measurement data. Until a communication channel is established for transmitting the data from the slave unit 1 to the master unit 2, the slave unit 1 and the repeaters 3a-3f transmit the data in a broadcast manner. When a transmission target is determined in a part of the communication channel from the slave unit 1 to the master unit 2, in the slave unit 1 and the repeaters 3a-3f, a node (slave unit 1 or repeater 3a-3f) which has the determined transmission target transmits the data to the determined transmission target in a unicast manner.

Description

  The present invention relates to a radio communication system, and more particularly to a radio communication system that relays and transmits a slave station and a master station by a relay station.

  Conventionally, a network system that performs multi-hop wireless communication between a base station node device and a plurality of child node devices has been proposed (see, for example, Patent Document 1).

  In this network system, a measuring device is connected to each of a plurality of child node devices. When a base station node device requests data from a child node device connected to a certain measuring device, if the connection relationship with this child node device is unknown, a request packet for requesting data is sent to the transmission destination. It transmits by broadcast without specifying the child node device to be.

  When the child node device receives the request packet from the base station node device, if the transmission destination address of the request packet does not match the device ID, the child node device functions as a relay node and sends the request packet to another child device. Broadcast transmission to the node device. As described above, the reception and broadcast transmission of the request packet by the child node device are repeated, so that the request packet is eventually received by the child node device to which the destination measuring device is connected. The child node device connected to the transmission destination measurement device creates a response packet to the request packet from the base station node device, specifies the transmission destination node device, and transmits it by unicast. Here, the header of the response packet includes the device ID of the child node device that created the response packet and the communication path to the base station node device, and reception and unicast transmission by the child node device are repeated. Thus, the data is finally transmitted to the base station node device.

JP 2013-74355 A

  In the network system of Patent Document 1, when a request packet is broadcast from a base station node device to a specific child node device, relay processing is performed between the nodes, so that the transmission destination child node device and the base station node device The connection relationship between them is specified. Therefore, in a state where the connection relationship with the base station node device is not specified, the data of the measuring device cannot be transmitted from the child node device side to the base station node device, and the request is made from the base station node device. I had to wait for the packet to be sent.

  In addition, in the wireless communication system, when transmission data collides between nodes, there is a problem that communication quality is deteriorated, data retransmission is increased, and power consumption is increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a wireless communication system that reduces the probability that transmission data collides when a communication path is established.

  The wireless communication system of the present invention performs wireless communication between a first node of a transmission source having a wireless communication function, a second node of a transmission destination having a wireless communication function, and the first node and the second node. A plurality of third nodes having a relay function. In a state where a communication path for transmitting data from the first node to the second node has not been established, the first node and the third node transmit data by broadcast. When the transmission destination is determined in at least a part of the communication path from the first node to the second node, the node in which the transmission destination is determined among the first node and the third node transmits data by unicast. It is characterized by that.

  In this wireless communication system, when the second node that is the final destination of the data transmitted by the first node receives the data, the final destination that indicates that the second node that is the final destination has received the data It is also preferable to send a reply with the information added to the ACK.

  This wireless communication system preferably includes the following configuration. When the third node receives the ACK with the final destination information added from the upper node of the communication path, when the next data is received from the lower node of the communication path, The final destination information is added to the ACK and returned.

  In this wireless communication system, when the second node receives data from the first node, the second node traces back the communication path through which the data has been transmitted to the third node that communicates directly with the first node. It is also preferable to return the final destination information.

  In this wireless communication system, when the second node and the third node receive the data transmitted by broadcast, the weight until the ACK is returned is larger than when the data transmitted by unicast is received. It is also preferable to lengthen the time.

  This wireless communication system preferably includes the following configuration. When the second node receives the data transmitted by broadcast, the wait time until the second node returns an ACK is the third time when the third node receives the data transmitted by broadcast. The time is set shorter than the wait time until the node returns ACK.

  This wireless communication system preferably includes the following configuration. Each of the first node and the third node resends data to the upper node by unicast when data transmission to an upper node in the communication path becomes impossible while the communication path is established. If the first node and the third node fail to transmit data again, the first node and the third node transmit data by broadcasting to reconstruct the communication path to the second node.

  This wireless communication system preferably includes the following configuration. When determining the transmission destination node, the first node or the third node returns the ACK if the received signal strength of the ACK is less than a predetermined threshold even if an ACK is received from an upper node. The higher order node is not a destination node. The first node or the third node excludes the upper node from transmission destination candidates.

  In this wireless communication system, if the third node fails to transmit data to the upper node and receives data from the lower node next time, the communication to the upper node is interrupted when an ACK is returned. Is also preferably notified to the lower node.

  In this wireless communication system, when the second node and the third node receive data from a lower node, if the ACK for the same data is returned from another node to the lower node, the lower node It is also preferable not to return an ACK to the node.

  In this wireless communication system, when the third node receives again the same data as previously transmitted data, the third node preferably discards the received data again and returns an ACK to the transmission source.

  According to the present invention, since the first node and the third node transmit data by broadcast, even if the communication path is not determined, the data transmitted from the first node can be transmitted directly or via the third node. Via the second node. In addition, when the transmission destination is determined in at least a part of the communication path, the node in which the transmission destination is determined among the first node and the third node transmits data by unicast. Reduced ACKs. As a result, the amount of communication decreases, and the probability that transmission data collides decreases.

(A)-(d) is explanatory drawing explaining the communication procedure of the radio | wireless communications system of this embodiment. In the wireless communication system of the present embodiment, (a) is a block diagram of a slave unit, (b) is a block diagram of the master unit, and (c) is a block diagram of a repeater. It is explanatory drawing explaining the signal format of ACK used with the radio | wireless communications system of this embodiment. It is explanatory drawing explaining the communication procedure of the radio | wireless communications system of this embodiment. It is explanatory drawing explaining the communication procedure of the radio | wireless communications system of this embodiment. (A) (b) is explanatory drawing explaining the communication procedure of the radio | wireless communications system of this embodiment. It is explanatory drawing explaining the communication procedure of the radio | wireless communications system of this embodiment. It is explanatory drawing explaining the communication procedure of the radio | wireless communications system of this embodiment. (A) (b) is explanatory drawing explaining the communication procedure of the radio | wireless communications system of this embodiment. It is explanatory drawing explaining the communication procedure of a radio | wireless communications system.

  An embodiment of a wireless communication system according to the present invention will be described with reference to the drawings.

  FIG. 1A shows a schematic configuration of the wireless communication system of the present embodiment. The wireless communication system of this embodiment includes a slave unit (first node) 1 that is a data transmission source, a master unit (second node) 2 that is a data transmission destination, and a plurality of units (for example, six units in FIG. 1). ) 3a, 3b, 3c, 3d, 3e and 3f. In the following description, when individual relay devices are specified and described, they are expressed as relay devices 3a, 3b, 3c, 3d, 3e, and 3f. When all the relay devices are described generically, they are expressed as relay devices 3. To do. Although the wireless communication system of the present embodiment includes six repeaters 3, the number of repeaters 3 is not limited to six, and it is sufficient if the number is necessary for signal relay. Further, there may be a plurality of slave units 1 that are data transmission sources, and the master unit 2 may collect data from the plurality of slave units 1 via the relay unit 3.

  The handset 1, the base unit 2, and the relay unit 3 are respectively wireless communication units that do not require a wireless license (for example, a specific low-power wireless module, a wireless communication unit that conforms to the IEEE 802.15.1 standard, IEEE 802.15. Wireless communication unit compliant with the standard No. 4). Here, if the handset 1 and the base unit 2 are within the communication range of each other, wireless communication is directly performed between the handset 1 and the base unit 2, but the handset 1 and the base unit 2 cannot communicate directly. In this case, wireless communication is performed between the slave unit 1 and the master unit 2 via the relay unit 3. Therefore, the plurality of repeaters 3 are arranged so that other adjacent repeaters 3 exist in the communication area so that the wireless communication between the slave unit 1 and the master unit 2 can be relayed. Has been built.

  Next, the structure of the subunit | mobile_unit 1, the main | base station 2, and the relay machine 3 is demonstrated based on Fig.2 (a)-(c).

  As shown in FIG. 2A, the slave unit 1 includes an MCU (Micro Control Unit) 10, a measurement unit 11, a storage unit 12, a wireless communication unit 13, an antenna 14, an operation unit 15, and a display. Unit 16 and power supply unit 17. The subunit | mobile_unit 1 wirelessly transmits the data which the measurement part 11 measured with the predetermined measurement timing to the main | base station 2. FIG.

  The MCU 10 performs overall control of the slave unit 1.

  The measurement unit 11 is for measuring temperature, for example, and includes a thermistor whose electric resistance changes according to the ambient temperature, and measures the ambient temperature by measuring the resistance value of the thermistor. Note that the measurement target of the measurement unit 11 is not limited to temperature, and it is only necessary to measure a physical quantity according to the purpose of use and application such as ambient humidity and illuminance.

  The storage unit 12 is configured by an electrically rewritable nonvolatile memory such as an EEPROM (electrically erasable and programmable read-only memory) or a flash memory. The storage unit 12 writes and reads data by the MCU 10 and stores identification information (slave unit ID) assigned to the slave unit 1, measurement data by the measurement unit 11, communication path information, and the like. .

  The wireless communication unit 13 includes a wireless module that conforms to a specific low power wireless communication standard, for example, and transmits or receives a wireless signal via the antenna 14.

  The operation unit 15 is used to set, for example, a lower limit value and an upper limit value of a measurement range by the measurement unit 11, a measurement interval, a measurement data transmission interval, and the like.

  The display unit 16 includes, for example, one or a plurality of light emitting diodes, and lighting / extinguishing is controlled by the MCU 10.

  The power supply unit 17 supplies, for example, power necessary for the operation to the internal circuit of the child device 1 using a battery as a power source.

  As shown in FIG. 2B, the base unit 2 includes an MCU 20, a storage unit 21, a wireless communication unit 22, an antenna 23, a wired communication unit 24, an operation unit 25, a display unit 26, a power source, Part 27.

  The MCU 20 performs overall control of the parent device 2.

  The storage unit 21 is configured by an electrically rewritable nonvolatile memory such as an EEPROM or a flash memory. The storage unit 21 writes and reads data by the MCU 20, and stores identification information assigned to the parent device 2, measurement data collected from the child device 1, communication path information, and the like.

  The wireless communication unit 22 includes, for example, a wireless module that conforms to a specific low power wireless communication standard, and transmits or receives a wireless signal via the antenna 23.

  The wired communication unit 24 is connected to, for example, a server (not shown) via a communication line, and transmits data collected from the slave unit 1 to the server in a wired manner.

  The operation unit 25 is used, for example, for performing operation settings of the parent device 2.

  The display unit 26 includes, for example, one or a plurality of light emitting diodes, and lighting / extinguishing is controlled by the MCU 20.

  The power supply unit 27 receives supply of power from, for example, a commercial power supply, and supplies power necessary for operation to the internal circuit of the parent device 2.

  As shown in FIG. 2C, the repeater 3 includes an MCU 30, a storage unit 31, a wireless communication unit 32, an antenna 33, an operation unit 34, a display unit 35, and a power supply unit 36. Yes.

  The MCU 30 performs overall control of the repeater 3.

  The storage unit 31 is configured by an electrically rewritable nonvolatile memory such as an EEPROM or a flash memory. The storage unit 31 writes and reads data by the MCU 30, identification information assigned to the own device, data received by the wireless communication unit 32, data transmitted by the wireless communication unit 32 in the past, communication path Save the information etc.

  The wireless communication unit 32 includes, for example, a wireless module conforming to a specific low power wireless communication standard, and transmits or receives a wireless signal via the antenna 33.

  The operation unit 34 is used, for example, for setting the operation of the relay device 3.

  The display unit 35 includes, for example, one or a plurality of light emitting diodes, and lighting / extinguishing is controlled by the MCU 30.

  The power supply unit 36 supplies, for example, power necessary for operation to the internal circuit of the repeater 3 using a battery as a power source. Since the relay machine 3 uses a battery as a power source, the relay machine 3 can be installed and used at any place. The power supply unit 36 may receive power supplied from a commercial power supply and supply power necessary for operation to the internal circuit of the repeater 3.

  Next, in the wireless communication system of the present embodiment, a process of transmitting measurement data from the slave unit 1 to the master unit 2 in a state where the communication path between the slave unit 1 and the master unit 2 is not established is shown in FIG. This will be described with reference to (a) to (d).

  A communication procedure in a case where the slave unit 1 transmits measurement data for the first time in a state where the communication path between the slave unit 1 and the master unit 2 has not been established will be described with reference to FIG.

  The MCU 10 of the handset 1 starts from the sleep mode at a predetermined sampling interval (for example, an interval of several seconds to several minutes), and causes the measurement unit 11 to measure the temperature. The MCU 10 of the slave unit 1 stores the measurement data of the measurement unit 11, the sequence number assigned to the transmission data, and the slave unit ID, and creates transmission data with the destination address as the broadcast address. And MCU10 of the subunit | mobile_unit 1 transmits the produced transmission data by broadcast from the wireless communication part 13 (process T1 of Fig.1 (a)).

  In the example of FIG. 1, there are three relay units 3d, 3e, and 3f within the communication range of the slave unit 1, and data transmitted from the slave unit 1 is received by these three relay units 3d, 3e, and 3f. The When the wireless communication unit 32 of the relay device 3d receives the transmission data from the child device 1, the MCU 30 of the relay device 3d controls the wireless communication unit 32 to receive an ACK (acknowledgment) to the transmission source child device 1. Is returned (process T2 in FIG. 1A). Similarly, the relay devices 3e and 3f also return an ACK to the child device 1 (processes T3 and T4 in FIG. 1A). When receiving the ACK returned after the data is transmitted, the slave unit 1 switches to the sleep mode after a predetermined time has elapsed to reduce power consumption.

  Next, a process of relaying and transmitting data received from the slave unit 1 by the relay unit 3d will be described. The MCU 30 of the relay unit 3d extracts the measurement data, the sequence number, and the slave unit ID from the transmission data from the slave unit 1, and includes the measurement data, the sequence number, and the slave unit ID, and the transmission data with the destination address as the broadcast address. Create The MCU 30 of the repeater 3d transmits this transmission data by broadcast from the wireless communication unit 32 (process T5 in FIG. 1A). In the example of FIG. 1, there are three repeaters 3a, 3b, 3e and a slave unit 1 within the communication range of the repeater 3d, and data transmitted by broadcast from the repeater 3d is transmitted to these repeaters 3a, 3b. , 3e. Since the handset 1 is switched to the sleep mode when receiving ACK after data transmission, the handset 1 does not receive the transmission data from the repeater 3d. Note that the relay units 3e and 3f also transmit data received from the slave unit 1 by broadcast in the same manner as the relay unit 3d, but the description thereof is omitted.

  When the wireless communication unit 32 of the relay device 3b receives the transmission data from the relay device 3d, the MCU 30 of the relay device 3b returns an ACK to the transmission source relay device 3d (process T6 in FIG. 1A). Similarly, ACK is returned from the relay devices 3a and 3e to the relay device 3d (processes T7 and T8 in FIG. 1A).

  Next, processing for relay transmission of data received by the relay device 3b from the relay device 3d will be described. The MCU 30 of the relay device 3b creates transmission data using the destination address as a broadcast address, including the measurement data extracted from the transmission data from the relay device 3d, the sequence number, and the slave device ID. Then, the MCU 30 of the repeater 3b transmits this transmission data by broadcast from the wireless communication unit 32 (process T9 in FIG. 1A). In the example of FIG. 1, the master unit 2 and the relay units 3a, 3c to 3f exist within the communication range of the relay unit 3b, and the data transmitted by broadcast from the relay unit 3b is the base unit 2 and the relay units 3a, 3c to 3f. 3f. Note that the relay units 3a and 3e also transmit data received from the relay unit 3d in the same manner as the relay unit 3b, but the description thereof is omitted.

  When the master unit 2 and the relay units 3a, 3c to 3f receive data from the relay unit 3b, the master unit 2 and the relay units 3a, 3c to 3f send back an ACK. 3c to 3f are set to a time shorter than the wait time until the ACK is returned. Therefore, the ACK from the parent device 2 is first returned to the relay device 3b.

  When the wireless communication unit 22 of the parent device 2 receives the transmission data from the relay device 3b, the MCU 20 of the parent device 2 takes in the measurement data, the sequence number, and the child device ID included in the transmission data, and the new child device 1 It is determined that measurement data has been received from. The MCU 20 of the base unit 2 adds the final destination information (for example, a 1-bit flag) indicating that the base unit 2 as the final destination has received data to the ACK, and transmits the ACK to the relay unit 3b of the transmission source ( Process T10 in FIG. FIG. 3 shows a signal format of data for returning an ACK. The reply data includes a preamble D1, data D2 called SFD (Start Frame Delimiter) indicating the start of data, data D3 indicating data length, data D4 storing ACK, and CRC ( It consists of data D5 called Cyclic Redundancy Check. Here, a flag of final destination information and information indicating the number of relay stages (the number of hops) are added to the data D4.

  When the ACK returned from the base unit 2 is received by the wireless communication unit 32 of the relay unit 3b, the MCU 30 of the relay unit 3b receives the data transmitted by the base unit based on the final destination information added to the ACK. It can be determined that the signal has been received by the parent device 2, and the communication route to the parent device 2 is determined in the relay device 3b. That is, if the flag of the final destination information added to the ACK is set, the relay device 3 can determine that the own device can communicate with the parent device 2 directly or via another relay device 3. The upper node (master unit 2 or other relay unit 3) that has returned the ACK is set as the destination node.

  Note that transmission data is also transmitted to the base unit 2 from the relay unit 3a. However, the MCU 20 of the base unit 2 uses the sequence number and the slave unit ID included in the transmission data and the previously received data. It is determined that the same data has been transmitted. In this case, the MCU 20 of the parent device 2 causes the wireless communication unit 22 to return the ACK without setting the final destination information flag to the transmission source relay device 3a. Further, the data transmitted from the relay device 3a is also received by the relay device 3d, but the MCU 30 of the relay device 3d uses the sequence number and the slave device ID included in the transmission data to transmit the previously transmitted data. Judge that received. In this case, the MCU 30 of the relay device 3d discards the received data and causes the wireless communication unit 32 to return only ACK to the transmission source relay device 3a.

  In this way, when the first measurement data is transmitted from the slave unit 1, the measurement data is transmitted from the slave unit 1 to the master unit 2 via the relay unit 3d and the relay unit 3b. Further, the relay device 3b determines that the own device is communicating with the parent device 2 based on the final destination information added to the ACK returned from the parent device 2, and determines the transmission destination node as the parent device. Set to 2. As a result, a route connecting the relay device 3b and the parent device 2 among the communication routes from the child device 1 to the parent device 2 is determined.

  Next, a communication procedure when the handset 1 transmits measurement data for the second time will be described with reference to FIG.

  When a predetermined sampling interval elapses from the previous measurement, the MCU 10 of the slave unit 1 starts from the sleep mode and causes the measurement unit 11 to measure the temperature. The MCU 10 of the slave unit 1 stores the measurement data of the measurement unit 11, the sequence number, and the slave unit ID, creates transmission data with the destination address as a broadcast address, and transmits this transmission data from the wireless communication unit 13 by broadcast. (Processing T11 in FIG. 1B).

  Data transmitted by broadcast from the slave unit 1 is received by the relay units 3d, 3e, and 3f. When the wireless communication unit 32 of the relay device 3d receives the transmission data from the child device 1, the MCU 30 of the relay device 3d controls the wireless communication unit 32 and returns an ACK to the transmission-source child device 1 (FIG. 1). Process T12 of (b)). Similarly, the relay devices 3e and 3f return ACK to the child device 1 (processes T13 and T14 in FIG. 1B). When receiving the ACK returned after the data is transmitted, the slave unit 1 switches to the sleep mode after a predetermined time has elapsed, thereby reducing power consumption.

  Next, the MCU 30 of the relay unit 3d creates transmission data including the measurement data extracted from the transmission data from the slave unit 1, the sequence number, and the slave unit ID, and having the destination address as a broadcast address. The MCU 30 of the relay unit 3d transmits this transmission data by broadcast from the wireless communication unit 32 (process T15 in FIG. 1B). Data transmitted by broadcast from the repeater 3d is received by the repeaters 3a, 3b, 3e within the communication range of the repeater 3d. The slave unit 1 is also within the communication range of the relay unit 3d. However, since the slave unit 1 is switched to the sleep mode after receiving the ACK, the transmission data from the relay unit 3d is not received by the slave unit 1. Note that the relay units 3e and 3f also transmit data received from the slave unit 1 by broadcast in the same manner as the relay unit 3d, but the description thereof is omitted.

  When the wireless communication unit 32 of the relay device 3b receives the transmission data from the relay device 3d, the MCU 30 of the relay device 3b adds the final destination information returned from the parent device 2 during the previous communication to the ACK, and performs wireless communication. The unit 32 sends a reply to the transmission source relay device 3d (process T16 in FIG. 1A). When the ACK returned from the repeater 3b is received by the wireless communication unit 32 of the repeater 3d, the MCU 30 of the repeater 3d determines that the repeater 3b is the master 2 based on the final destination information added to the ACK. It is determined that it is a repeater that is communicating with. The MCU 30 of the relay device 3d sets the destination node to the relay device 3b, and the communication route to the parent device 2 is also determined in the relay device 3d. In addition, when the relay devices 3a and 3e receive the transmission data from the relay device 3d, the relay devices 3a and 3e return ACK to the relay device 3d (processes T17 and T18 in FIG. 1B).

  Next, the MCU 30 of the relay device 3b creates transmission data having the destination address as the address of the parent device 2, including the measurement data extracted from the transmission data from the relay device 3d, the sequence number, and the slave device ID. The MCU 30 of the relay device 3b transmits the transmission data from the wireless communication unit 32 by unicast (process T19 in FIG. 1B). When the wireless communication unit 22 of the parent device 2 receives the transmission data from the relay device 3b, the MCU 20 of the parent device 2 captures the measurement data, the sequence number, and the child device ID included in the transmission data. Further, the MCU 20 of the parent device 2 causes the wireless communication unit 22 to transmit an ACK to the transmission source relay device 3b (process T20 in FIG. 1B), and transmits data from the child device 1 to the parent device 2. A series of processing ends.

  As described above, when the second measurement data is transmitted from the slave unit 1, the measurement data is transmitted from the slave unit 1 to the master unit 2 via the relay unit 3d and the relay unit 3b. Further, the relay device 3d sets the destination node in the relay device 3b based on the final destination information added to the ACK from the relay device 3b, and relays the communication path from the child device 1 to the parent device 2. The route from the machine 3d to the parent machine 2 is fixed.

  Next, a communication procedure when the handset 1 transmits measurement data for the third time will be described with reference to FIG.

  When a predetermined sampling interval elapses from the previous measurement, the MCU 10 of the slave unit 1 starts from the sleep mode and causes the measurement unit 11 to measure the temperature. The MCU 10 of the slave unit 1 stores the measurement data of the measurement unit 11, the sequence number, and the slave unit ID, creates transmission data with the destination address as a broadcast address, and transmits the broadcast data from the wireless communication unit 13 (FIG. 1). (C) Process T21).

  Data transmitted by broadcast from the slave unit 1 is received by the relay units 3d, 3e, and 3f. When the wireless communication unit 32 of the relay device 3d receives the transmission data from the child device 1, the MCU 30 of the relay device 3d adds the final destination information returned from the relay device 3b during the previous communication to the ACK, and performs wireless communication. A reply is sent from the unit 32 to the child machine 1 as the transmission source (process T22 in FIG. 1C). When the ACK returned from the relay device 3d is received by the wireless communication unit 13 of the slave device 1, the MCU 10 of the slave device 1 determines that the relay device 3d is the master device 2 based on the final destination information added to the ACK. It is determined that the relay station is communicating with the relay station 3d, and the destination node is set to the relay station 3d. Thereby, the communication path from the subunit | mobile_unit 1 to the main | base station 2 is established. Note that the relay devices 3e and 3f also return an ACK to the child device 1 (processes T23 and T24 in FIG. 1C). When receiving the ACK returned after the data is transmitted, the slave unit 1 switches to the sleep mode after a predetermined time has elapsed, thereby reducing power consumption.

  The MCU 30 of the relay device 3d creates transmission data having the destination address as the address of the relay device 3b including the measurement data extracted from the transmission data from the slave device 1, the sequence number, and the slave device ID. Transmission is performed by unicast (process T25 in FIG. 1C). Note that the relay units 3e and 3f also transmit data received from the slave unit 1 by broadcast in the same manner as the relay unit 3d, but the description thereof is omitted.

  When the wireless communication unit 32 of the relay device 3b receives the transmission data from the relay device 3d, the MCU 30 of the relay device 3b returns an ACK to the transmission source relay device 3d (process T26 in FIG. 1C). .

  Further, the MCU 30 of the relay device 3b creates transmission data having the destination address as the address of the parent device 2, including the measurement data extracted from the transmission data from the relay device 3d, the sequence number, and the slave device ID. The MCU 30 of the repeater 3b transmits the transmission data from the wireless communication unit 32 by unicast (process T27 in FIG. 1C). When the wireless communication unit 22 of the parent device 2 receives the transmission data from the relay device 3b, the MCU 20 of the parent device 2 captures the measurement data, the sequence number, and the child device ID included in the transmission data. In addition, the MCU 20 of the parent device 2 transmits an ACK from the wireless communication unit 22 to the transmission source relay device 3b (process T28 in FIG. 1C), and transmits a series of data from the child device 1 to the parent device 2. Processing ends.

  As described above, when the third measurement data is transmitted from the slave unit 1, the measurement data is transmitted from the slave unit 1 to the master unit 2 via the relay unit 3d and the relay unit 3b. Further, the slave unit 1 determines that the relay unit 3d is communicating with the base unit 2 based on the final destination information added to the ACK from the relay unit 3d, and determines the transmission destination node as the relay unit 3d. The communication path from the child device 1 to the parent device 2 is determined.

  Next, a communication procedure when the handset 1 transmits measurement data after the fourth time will be described with reference to FIG.

  When a predetermined sampling interval elapses from the previous measurement, the MCU 10 of the slave unit 1 starts from the sleep mode and causes the measurement unit 11 to measure the temperature. The MCU 10 of the slave unit 1 stores the measurement data of the measurement unit 11, the sequence number, and the slave unit ID, creates transmission data with the destination address as the address of the relay unit 3d, and transmits it by unicast from the wireless communication unit 13 (Process T29 in FIG. 1D).

  Data transmitted by unicast from the slave unit 1 is received by the relay unit 3d, and an ACK is returned from the relay unit 3d to the source slave unit 1 (process T30 in FIG. 1D). When receiving the ACK returned after the data is transmitted, the slave unit 1 switches to the sleep mode after a predetermined time has elapsed, thereby reducing power consumption.

  Upon receiving the transmission data transmitted from the slave unit 1, the MCU 30 of the relay unit 3d creates transmission data including the measurement data, the sequence number, and the slave unit ID and having the destination address as the address of the relay unit 3b. The MCU 30 of the relay unit 3d transmits the transmission data from the wireless communication unit 32 by unicast (process T31 in FIG. 1 (d)).

  When the relay device 3b receives the transmission data from the relay device 3d, the relay device 3b returns an ACK to the transmission source relay device 3d (process T32 in FIG. 1D).

  Further, the MCU 30 of the relay device 3b creates transmission data having the destination address as the address of the parent device 2, including the measurement data extracted from the transmission data received from the relay device 3d, the sequence number, and the slave device ID. The MCU 30 of the repeater 3b transmits this transmission data from the wireless communication unit 32 by unicast (process T33 in FIG. 1 (d)).

  When the wireless communication unit 22 of the parent device 2 receives the transmission data from the relay device 3b, the MCU 20 of the parent device 2 captures the measurement data, the sequence number, and the child device ID included in the transmission data. Further, the MCU 20 of the parent device 2 causes the wireless communication unit 22 to transmit ACK to the transmission source relay device 3b (process T34 in FIG. 1 (d)), and a series in which data is transmitted from the child device 1 to the parent device 2. This process ends.

  As described above, after the communication path from the slave unit 1 to the master unit 2 is determined, each node interposed in the communication path from the slave unit 1 to the master unit 2 transmits data by unicast. Compared with the case where ACK is returned, the number of ACKs returned is reduced. As a result, the amount of communication decreases, and the probability that transmission data collides decreases.

  The wireless communication system according to the present embodiment includes a transmission-source child device 1 (first node) having a wireless communication function, a transmission-destination parent device 2 (second node) having a wireless communication function, and a plurality of relay devices. 3 (third node). The plurality of relay devices 3 have a function of relaying wireless communication between the child device 1 and the parent device 2. Until a communication path for transmitting data from the child device 1 to the parent device 2 is established, the child device 1 and the relay device 3 transmit data by broadcast. When the transmission destination is determined in at least a part of the communication path from the child device 1 to the parent device 2, the node (the child device 1, the relay device 3) in which the transmission destination is determined among the child device 1 and the relay device 3 is unidirectional. Send data by casting.

  As described above, since the slave unit 1 and the relay unit 3 transmit data by broadcasting in a state where the communication path is not established, the data transmitted from the slave unit 1 is transmitted directly or via the relay unit 3. To the base unit 2. When the transmission destination is determined in at least a part of the communication path, the node in which the transmission destination is determined among the slave unit 1 and the relay unit 3 transmits data by unicast, so compared to the case where each node transmits by broadcast. The number of ACKs that are returned is reduced. As a result, the amount of communication decreases and the probability that transmission data collides decreases.

  In the wireless communication system according to the present embodiment, when the master unit 2 receives data from the slave unit 1, the master unit 2 as the final destination adds a final destination information indicating that the data has been received to the ACK and sends back. . Therefore, the node (slave unit 1 or relay unit 3) that has received this ACK can determine that it can communicate with the base unit 2, and can set the transmission destination to the base unit.

  In the wireless communication system of the present embodiment, the following processing is performed. When the relay device 3 receives the ACK to which the final destination information is added from the upper node (master device 2 or another relay device 3) on the communication path, the relay device 3 (the child device 1 or another relay device 3). ), The final destination information is added to the ACK and sent back to the lower node.

  In this way, when receiving the ACK with the final destination information added from the upper node, the relay station 3 adds the final destination information to the ACK and sends it back to the lower node when the next data is received. By sending back ACK, the transmission destination is determined in order from the upper node to the lower node.

  Further, in the wireless communication system of the present embodiment, when the master unit 2 receives data from the slave unit 1, the relay unit 3 that directly communicates with the slave unit 1 by tracing back the communication path through which the data has been transmitted. Until this time, it is also preferable that the handset 1 returns the final destination information before transmitting the next data.

  FIG. 4 is an explanatory diagram for explaining this communication procedure. In the same procedure as the first data transmission from the child device 1 to the parent device 2 described with reference to FIG. 1 (a), the measurement data transmitted by the child device 1 is transmitted via the relay device 3d to the relay device 3b. The relay device 3b broadcasts transmission data including measurement data (process T9 in FIG. 4). When the base unit 2 receives the transmission data from the relay unit 3b, the base unit 2 returns an ACK to which the final destination information is added to the source relay unit 3b (process T10 in FIG. 4). The relay device 3b determines that its own device is communicating with the parent device 2 based on the final destination information added to the ACK from the parent device 2, and the route connecting the relay device 3b and the parent device 2 is determined. Determine. The master unit 2 traces the communication path from the slave unit 1 to the master unit 2 in the reverse direction, and adds the final destination information to the relay unit 3d that is a node directly above the slave unit 1 and directly communicates with the slave unit 1. The dedicated command is transmitted all at once (process T35 in FIG. 4). This dedicated command is relayed to the relay device 3d by tracing the communication path in the reverse direction. The relay device 3 (relay device 3d in the example of FIG. 4) that has received this dedicated command is a node that constitutes a communication path from the child device 1 to the parent device 2 based on the final destination information added to the dedicated command. And the higher-order node that directly communicates with the own device is determined as the transmission destination. Therefore, the communication path from the node on the higher level side of the slave unit 1 (relay unit 3d) to the master unit 2 is determined uniformly, and the relay unit 3d in the middle of the communication path can determine the data transmission destination. Therefore, when the slave unit 1 transmits the next data, data is transmitted by unicast from the upper node of the slave unit 1 to the master unit 2, so that the communication path can be constructed in a short time. it can. When the slave unit 1 broadcasts the next data, an ACK with final destination information added from the relay unit 3d is returned to the slave unit 1, so that the communication path from the slave unit 1 to the master unit 2 is determined. .

  Further, in the present embodiment, when the master unit 2 and the relay unit 3 receive data by broadcast from the lower node of the communication path, the ACK is received compared to when the data is received by unicast from the lower node of the communication path. The wait time until replying may be increased.

  FIG. 5 is an explanatory diagram for explaining this communication procedure. As described with reference to FIG. 1B, when data is transmitted from the slave unit 1 in a state where the transmission destination of the relay unit 3b is determined, the data transmitted by broadcast from the relay unit 3d is transmitted to the relay unit. Received at 3a and 3b. Since the transmission destination has not been determined, the relay device 3a transmits the transmission data including the measurement data received from the relay device 3d by broadcast (process T36 in FIG. 5). On the other hand, since the transmission destination of the relay device 3b is fixed to the master device 2, the relay device 3b transmits the transmission data including the measurement data received from the relay device 3d to the master device 2 by unicast. (Processing T19 in FIG. 5).

  Here, when the base unit 2 receives the data from the lower node by broadcast, the base unit 2 makes the wait time until the ACK is returned longer than when the base unit 2 receives the data from the lower node by unicast. Accordingly, the base unit 2 can preferentially send back an ACK to the relay unit 3b that has transmitted data by unicast, that is, the relay unit 3b that has established a communication path (process T20 in FIG. 5).

  In the relay unit 3 as well, when data is received by broadcast from a lower node (another relay device 3), the wait time until the ACK is returned is larger than when data is received from a lower node by unicast. It is long. Therefore, the repeater 3 can also preferentially return an ACK to the lower-order repeater 3 that has transmitted data by unicast, that is, the lower-order repeater 3 whose communication path is fixed.

  Further, in the wireless communication system of the present embodiment, when the master unit 2 receives broadcast-transmitted data, the wait time until the master unit 2 returns an ACK is the broadcast-transmitted data. Is preferably set to a time shorter than the wait time until the repeater 3 returns an ACK. As shown in FIG. 1A, when the relay device 3b transmits data by broadcast (process T9), the data transmitted from the relay device 3b is not only the master device 2, but also other relay devices 3a, 3c to 3f. Also received. Therefore, the ACK is returned from the other relay devices 3a, 3c to 3f to the relay device 3b. Here, since the base unit 2 sends back an ACK in a shorter wait time than the relay unit 3, the ACK from the base unit 2 is sent back to the source relay unit 3 b in preference to the other relay units 3. Therefore, the time until the communication path is determined can be shortened.

  In addition, after a communication path from the slave unit 1 to the master unit 2 is determined, some communication trouble may occur and communication may be disabled. In the wireless communication system of this embodiment, the communication path is as follows. Is rebuilding. When the communication path to the base unit 2 is established and the data transmission to the upper node in the communication path becomes impossible, the slave unit 1 and the relay unit 3 retransmit the data by unicast to the upper node. When each of the slave unit 1 and the relay unit 3 fails to transmit data again, the slave unit 1 and the relay unit 3 transmit data by broadcasting to reconstruct the communication path to the master unit 2.

  6A and 6B are explanatory diagrams for explaining this communication procedure. When communication between the relay device 3e and the relay device 3b is interrupted when data is transmitted from the slave device 1 to the master device 2 via the relay device 3e and the relay device 3b by unicast. First, the repeater 3e retransmits data to the repeater 3b by unicast (process T37 in FIG. 6A). Here, when the repeater 3e fails to communicate with the repeater 3b again due to a failure of the repeater 3b or a deterioration of the communication environment, the repeater 3e reconstructs the communication path. The transmission data is transmitted by broadcast (process T38 in FIG. 6B). Signals transmitted by broadcast from the relay device 3e are received by the relay devices 3a and 3c, and ACKs are returned from the relay devices 3a and 3c to the transmission source relay device 3e (processes T39 and T40 in FIG. 6B). . The relay devices 3a and 3c that have received the transmission data from the relay device 3e transmit the measurement data by broadcast (processes T41 and T42 in FIG. 6B), respectively. When the data transmitted from any one of the relay devices 3a and 3c is received by the master device 2, the master device 2 transmits an ACK flagged with final destination information to the sender relay device 3. Each time data is transmitted from the slave unit 1, ACKs with the final destination information flag set are sequentially transmitted to lower nodes, and a new communication path is constructed.

  In the wireless communication system of the present embodiment, it is also preferable to employ the following communication procedure. When determining the transmission destination node, the slave unit 1 or the relay unit 3 receives the ACK from the upper node, and if the received signal strength of the ACK is less than a predetermined threshold, the upper unit that has returned the ACK The node is not the destination node. And the subunit | mobile_unit 1 or the relay machine 3 excludes this high-order node from the candidate of a transmission destination.

  FIG. 7 is an explanatory diagram for explaining this communication procedure. When the relay unit 3d receives the measurement data transmitted from the slave unit 1 and transmits the transmission data created based on the measurement data by broadcast in a state where the communication path is not fixed, the relay unit 3d transmits The received data is received by the repeaters 3a, 3b, 3e. Thereafter, when the relay device 3b in the communication area of the parent device 2 transmits the measurement data by broadcast (process T19 in FIG. 7), this measurement data is received by the parent device 2, and the final destination information is added from the parent device 2. ACK is returned to the transmission source relay 3b. Here, the repeater 3b determines that the reply is from the base unit 2 based on the flag of the final destination information added to the ACK, and receives the received signal strength (RSSI: Received Signal Strength Indicator) of the received ACK. Compare the level with the threshold. If the received signal strength is less than the threshold, the relay device 3b does not set the parent device 2 that has returned ACK as a transmission destination node. Then, the relay device 3b excludes the parent device 2 that has returned an ACK whose received signal strength is less than the threshold from the transmission destination candidates. In this way, if the received signal strength is less than the threshold value, it is excluded from the transmission destination candidates. Therefore, a node having a higher received signal strength than the threshold value is set as the transmission destination, and stable communication can be performed. Become.

  Further, in the wireless communication system of the present embodiment, when the relay 3 fails to transmit data to the upper node, the next time it receives data from the lower node, the relay device 3 returns the ACK to the lower node to the upper node. The lower-level node may be notified that the communication is interrupted. The lower node (slave unit 1 or lower level repeater 3) that is notified that communication with the upper node is disconnected determines that some trouble has occurred in communication with the parent device 2, and transmits, for example, By setting the interval longer, the number of transmissions can be reduced to reduce power consumption.

  In this embodiment, when the base unit 2 and the relay unit 3 receive data from the lower node (slave unit 1 or relay unit 3), an ACK for the same data is returned from the other node to the lower node. In this case, it is preferable not to return an ACK to the lower node.

  FIG. 8 is an explanatory diagram for explaining this communication procedure. When the slave unit 1 broadcasts the transmission data to the master unit 2 in a state where the communication path is not fixed, this transmission data is received by the relay units 3d, 3e, 3f in the communication range of the slave unit 1. The When the relay units 3d, 3e, and 3f receive the transmission data from the slave unit 1, the relay units 3d, 3e, and 3f send back an ACK signal after a wait time set to a random time for each relay unit elapses. If ACK for data is returned from another node, ACK is not returned.

  The relay units 3d, 3e, 3f continue to receive until the wait time elapses after receiving the transmission data. When the relay unit 3e returns an ACK (process T43 in FIG. 8), the relay unit 3e The ACK returned by is also received by the other repeaters 3d and 3f. Here, the sequence number of the received data is included in the ACK, and the MCU 30 of the relay devices 3d and 3f transmits the ACK for the same transmission data from the other relay device 3e from the sequence number in the received ACK. ACK is not returned. Accordingly, since only one ACK is returned for one transmission data, the number of ACK replies can be reduced, and the possibility of transmission data colliding can be reduced.

  In the wireless communication system according to the present embodiment, when the repeater 3 receives the same data as the previously transmitted data again, it is also preferable to discard the received data again and return an ACK to the transmission source node. .

  When the communication path is unconfirmed, the relay 3 transmits data by broadcast. Therefore, data previously transmitted by a certain relay device 3 is received by another relay device 3, and the other relay device 3 transmits this data by broadcast, so that the data previously transmitted by the relay device 3 is received again. there's a possibility that. For example, as shown in FIGS. 9A and 9B, when the relay device 3e transmits data by broadcast (process T44), the relay device 3a that has received this transmission data transmits data by broadcast (process T45). The repeater 3e receives the same data as that transmitted. In this case, the relay device 3e returns an ACK to the other relay device 3a of the transmission source (process T46), and the received data is discarded. As a result, the other relay device 3a of the transmission source can determine that the data transmission has succeeded since the ACK is returned. In addition, since the repeater 3e that has received the previously transmitted data again discards the received data, the same data is not transmitted from the repeater 3 again, and the amount of communication may be reduced and the signals may collide. Can be reduced.

  By the way, in the wireless communication system as described above, for example, a power meter is connected to any one of the repeaters 3, and when the measured value of the power meter is to be acquired from the master device 2, the master device is as follows. 2 and a communication path between the repeater 3 to which the power meter is connected.

  Communication processing in this case will be described with reference to FIG. In the example of FIG. 10, it is assumed that the power meter 4 is connected to the relay 3f.

  Since the communication path to the relay device 3 to which the power meter 4 is connected is unknown, the base unit 2 broadcasts a request signal that specifies the identification ID of the power meter 4 and requests a return of the measurement value ( Process T50 in FIG. 10). The request signal transmitted from the parent device 2 by broadcast is received by the relay devices 3a, 3b, 3c in the communication area of the parent device 2. The relay device 3c that has received the request signal from the parent device 2 returns an ACK to the transmission source parent device 2 (processing T51), and then transmits the request signal by broadcast (processing T52). Similarly to the relay device 3c, the other relay devices 3a and 3b also transmit a request signal by broadcast after returning an ACK to the transmission source master device 2. The request signal transmitted by broadcast from the repeater 3c is received by the repeater 3f to which the power meter 4 is connected. Based on the identification ID of the power meter 4 added to the request signal, the relay device 3f determines that the master device 2 requests the measured value of the power meter 4 connected to the own device, and the power meter 4 Is sent back to the transmission source repeater 3c by unicast (process T53). The relay device 3f returns the data to be returned to the relay device 3c with a flag of final destination information indicating that communication with the power meter 4 is possible. The relay 3c that has received this data determines that the relay 3f can communicate with the power meter 4 based on the flag of the final destination information added to the data, and acquires the measured value of the power meter 4. In this case, the transmission destination is set to the repeater 3f. Further, when receiving the data (measured value of the power meter 4) from the relay device 3f, the relay device 3c returns this data by broadcasting (process T54). Since the data returned by broadcast from the relay device 3c is received by the parent device 2 within the communication area of the relay device 3c, the parent device 2 can acquire the measured value of the power meter 4.

  Thereafter, when the base unit 2 broadcasts again a request signal for requesting a return of the measurement value by specifying the identification ID of the power meter 4, the relay unit 3c that has received this request signal sets the flag of the final destination information. The added ACK is returned to the base unit 2. As a result, the base unit 2 can acquire information on the communication path to the relay unit 3f to which the power meter 4 is connected based on the final destination information added to the ACK from the relay unit 3c. A request signal can be transmitted to the repeater 3c by casting, and the measured value of the power meter 4 can be acquired.

  In the wireless communication system that performs communication processing as shown in FIG. 10, when the base unit 2 and the relay unit 3 receive data from a lower node, an ACK for the same data is returned from another node to the lower node. If so, it is also preferable not to send an ACK back to the lower node.

  For example, when the base unit 2 broadcasts a measurement data request signal in a state where the communication path between the relay unit 3f to which the power meter 4 is connected and the base unit 2 is not fixed, the transmission data is It is received by the repeaters 3a, 3b, 3c in the communication range of the master unit 2. When the relay devices 3a, 3b, and 3c receive the request signal from the master device 2, the relay devices 3a, 3b, and 3c send back an ACK signal after a wait time set to a random time for each relay device has elapsed. If ACK for data is returned from another node, ACK is not returned. Also, when the relay device 3c transmits the measurement data returned from the relay device 3f by broadcast, the measurement data returned from the relay device 3c by broadcast is transmitted to the parent device 2 and the relay device within the communication range of the relay device 3c. It is received by the machines 3b and 3e. Here, when the base unit 2 and the relay units 3b and 3e receive the transmission data from the relay unit 3c, the base unit 2 and the relay unit 3b return an ACK signal. If an ACK for the same transmission data is returned from another node, Do not reply ACK. As a result, the number of ACKs returned from the repeater decreases, so the communication volume decreases and the probability that transmission data collides decreases.

1 Slave unit (first node)
2 Base unit (second node)
3, 3a-3f Repeater (third node)
4 Wattmeter

Claims (11)

A first node of a transmission source having a wireless communication function;
A destination second node having a wireless communication function;
A plurality of third nodes having a function of relaying wireless communication between the first node and the second node;
In a state where a communication path for transmitting data from the first node to the second node is not established, the first node and the third node transmit data by broadcast,
When the transmission destination is determined in at least a part of the communication path from the first node to the second node, the node in which the transmission destination is determined among the first node and the third node transmits data by unicast. A wireless communication system.   When the second node, which is the final destination of data transmitted by the first node, receives the data, it adds final destination information indicating that the second node, which is the final destination, has received the data to the ACK. The wireless communication system according to claim 1, wherein the wireless communication system sends a reply.   When the third node receives ACK with the final destination information added from an upper node of the communication path, the third node sets the final destination information to ACK when receiving the next data from the lower node of the communication path. The wireless communication system according to claim 2, wherein the wireless communication system is added and sent back to the lower node.   When the second node receives the data from the first node, the second destination information is traced back to the third node that directly communicates with the first node through the communication path through which the data has been transmitted. The wireless communication system according to claim 2, wherein a reply is made.   When the second node and the third node receive the data transmitted by broadcast, the second node and the third node increase the wait time until the ACK is returned compared to the case of receiving data transmitted by unicast. The wireless communication system according to any one of claims 1 to 4, wherein the wireless communication system is characterized in that:   When the second node receives the data transmitted by broadcast, the wait time until the second node returns an ACK is the third time when the third node receives the data transmitted by broadcast. 6. The wireless communication system according to claim 1, wherein a time shorter than a wait time until the node returns an ACK is set.   Each of the first node and the third node retransmits data by unicast to the upper node when data transmission to an upper node in the communication path becomes impossible while the communication path is established. The wireless communication system according to any one of claims 1 to 6, wherein when data transmission fails again, data is transmitted by broadcast to reconstruct a communication path to the second node. .   When determining the transmission destination node, the first node or the third node returns the ACK if the received signal strength of the ACK is less than a predetermined threshold even if an ACK is received from an upper node. The wireless communication system according to any one of claims 1 to 7, wherein the upper node is not set as a transmission destination node, and the higher node is excluded from transmission destination candidates.   When the third node receives data from the lower node next time when data transmission to the upper node fails, the third node notifies the lower node that communication to the upper node is interrupted when an ACK is returned. The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system.   When receiving data from a lower node, the second node and the third node do not return an ACK to the lower node if an ACK for the same data is returned from another node to the lower node. The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system.   11. The method according to claim 1, wherein, when the same data as the previously transmitted data is received again, the third node discards the received data again and returns an ACK to the transmission source. 11. The wireless communication system according to item.

Images