JP2012256149A - Wireless system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless system capable of collecting measurement data measured at a measurement terminal without losing the measurement data during communication.SOLUTION: A wireless network comprises: a measurement terminal 1 for measuring a prescribed physical amount to wirelessly transmit the measurement data at fixed intervals; a main device 2 for collecting the measurement data transmitted from the measurement terminal 1; and a relay device 3 interposed between the measurement terminal 1 and the main device 2 to relay the measured data. The relay device 3 includes a storage section 31 for storing the measurement data transmitted from the measurement terminal 1 establishing connection with the relay device 3 itself. The measurement data includes a time stamp (time information) based on the time when the measurement terminal 1 measures the measurement data.

Description

  The present invention relates to a wireless system that performs multi-hop wireless communication.

  Currently, a multi-hop wireless network method has been proposed in which a network is formed by a plurality of wireless terminals, and packets are relayed between adjacent wireless terminals, thereby enabling communication between wireless terminals that do not receive direct radio waves. . A sensor network system (wireless system) employing such a multi-hop wireless network system is disclosed in, for example, Patent Document 1.

  The conventional example described in Patent Document 1 includes a backbone device and a plurality of wireless devices. The backbone device is, for example, a computer having a wireless communication function, and manages the sensor information reported from each wireless device, and establishes and controls the path of the sensor network system. Prior to communication with a plurality of wireless devices, the backbone device executes a process of joining the wireless device to the wireless network to form a route. This route has a tree-like hierarchical relationship with the backbone device as the root.

  Each wireless device acquires various sensor information according to the sensor function of each wireless device, and reports to the backbone device. Prior to such a reporting process, the wireless device first executes a joining process to join the sensor network. In the participation process, the wireless device selects another wireless device that should form a parent-child relationship. At this time, the backbone device may be selected instead of another wireless device. This selection is performed so that the number of other wireless devices existing with the backbone device is minimized.

  And in this prior art example, the collision of radio packets at the time of relay processing is avoided by defining a specific transmission timing for each radio device constituting the network.

JP 2008-228176 A

  By the way, in the wireless system as in the above-described conventional example, the wireless device at the lowest level (position farthest from the backbone device) does not relay the wireless packet from the other wireless device, and does not relay the sensor information (measurement data). There is a case where only acquisition is performed, that is, a measurement terminal is used. And in such a measurement terminal, in order to make it easy to carry the terminal to a desired measurement location, it is common to use a battery provided for itself as an operating power supply without receiving an operating power supply from an external power supply. It is. For this reason, in such a measurement terminal, measurement data is transmitted at a predetermined interval so that it can be used for a long time with reduced battery consumption, and after transmission, the communication function is stopped until the next transmission, that is, in the sleep state Those that move to are common.

  However, in the above case, when measuring data transmitted from the measuring terminal is transmitted, there is a risk that the measured data may be lost during communication due to external noise or collision between radio signals. When the measurement data is lost in this way, the measurement terminal that has transmitted the measurement data is in the sleep state and cannot perform the retransmission process of the measurement data. Therefore, there is a problem that the lost measurement data cannot be collected by the backbone device.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a wireless system capable of collecting measurement data measured by a measurement terminal without being lost during communication.

  The wireless system of the present invention measures a predetermined physical quantity and wirelessly transmits measurement data including a measurement value at a predetermined interval. When the measurement data is transmitted, at least the communication function is transmitted until the measurement data is transmitted next. One or more measurement terminals to be stopped, a main device for collecting the measurement data of the measurement terminal, and one or more relay devices that are interposed between the measurement terminal and the main device to relay the measurement data And the relay device includes a storage unit that stores the measurement data transmitted from the measurement terminal that has established a connection with itself, and the measurement data includes the measurement data Time information based on the time when the terminal measured the measurement data is included.

  In this radio system, the relay device transmits and receives radio signals to and from the measurement terminal, and the measurement terminal and the relay device each include an electric field strength measurement unit that measures the electric field strength of the received radio signal. It is preferable that a wireless signal including information on the measured electric field strength is returned to the measurement terminal or the relay device.

  In this wireless system, the main device transmits a request signal for requesting transmission of the measurement data to the relay device, and the relay device stores the request terminal of the measurement terminal that it stores when receiving the request signal. It is preferable that a reply signal including measurement data is returned to the main apparatus.

  In this wireless system, when the relay device determines the establishment or disconnection of the connection with the measurement terminal or receives the measurement data transmitted from the measurement terminal, the relay device sends a notification signal to that effect to the main device. When the main apparatus receives the notification signal transmitted from the relay apparatus, the main apparatus transmits the request signal to the relay apparatus.

  In this wireless system, it is preferable that the storage unit includes a nonvolatile memory, and the relay device stores the measurement data transmitted from the measurement terminal in the memory.

  The present invention has an effect that measurement data measured by a measurement terminal can be collected without being lost during communication.

1A and 1B are diagrams showing an embodiment of a wireless system according to the present invention, where FIG. 1A is a schematic diagram, and FIG. 1B is a sequence diagram when requesting measurement data from a main device. It is a schematic block diagram which shows the structure of each part in a radio | wireless system same as the above, (a) is a schematic block diagram of a measurement terminal, (b) is a schematic block diagram of a main apparatus, (c) is a schematic block diagram of a relay apparatus. is there. FIG. 2A is a schematic diagram and FIG. 2B is a sequence diagram when a relay device transmits a notification signal in the above wireless system.

  Embodiments of a wireless system according to the present invention will be described below with reference to the drawings. As shown in FIG. 1A, the present embodiment includes a plurality (three in the figure) of measurement terminals 1, a main apparatus 2, and a plurality (three in the figure) of relay apparatuses 3, and these measurements are performed. The terminal 1, the main device 2, and the relay device 3 (hereinafter collectively referred to as “wireless devices”) constitute a wireless network. In the following description, in order to distinguish between the plurality of measuring terminals 1, the measuring terminal 1 is represented by reference numerals 1 </ b> A to 1 </ b> C as necessary, and in order to distinguish between the plurality of relay apparatuses 3, the relay apparatus as necessary. 3 is represented by reference numerals 3A to 3C.

  As shown in FIG. 2A, the measurement terminal 1 is a radio that transmits and receives radio signals to and from a measurement unit 10 that measures a predetermined physical quantity (temperature, power consumption, flow rate) such as a thermometer, a power meter, and a gas meter. A transmission / reception unit 11, a control unit 12 that controls each unit, and a battery 13 that is a driving power source are provided. In addition, the measurement terminal 1 includes an electric field strength measurement unit 14 that measures the electric field strength of a radio signal received by the radio transmission / reception unit 11.

  The radio transmission / reception unit 11 includes a transmission circuit unit (not shown) that transmits a radio signal via an antenna (not shown) and a reception circuit unit (not shown) that receives a radio signal via the antenna. To do. Since the configuration of the wireless transmission / reception unit 11 is well known in the art, detailed description thereof is omitted here.

  The control unit 12 includes, for example, a microcomputer and implements various functions by executing programs stored in the memory. The control unit 12 causes the measurement unit 10 to perform measurement processing at regular intervals, and acquires measurement data including the measured values. Then, the control unit 12 causes the wireless signal including the measurement data to be transmitted from the wireless transmission / reception unit 11 to the relay apparatus 3 that has established a connection with the wireless signal (set in the communication path).

  Here, in order to make it easy to carry the terminal to a desired measurement location, the measurement terminal 1 obtains the operating power from the battery 13 provided in the measuring terminal 1 without receiving the operating power from the external power source. ing. Further, when transmitting the measurement data, the control unit 12 shifts the wireless transmission / reception unit 11 to a sleep state in which the operation is stopped until the next measurement data is transmitted. Thereby, the power consumption in the wireless transmission / reception unit 11 is reduced, and the battery 13 can be used for a long time while suppressing the consumption of the battery 13.

  In this embodiment, each wireless device has a unique address (MAC address and network address), and the transmission destination and transmission source of the wireless signal can be specified by the MAC address and network address. For this reason, the MAC address and network address of each wireless device are stored in the memory of the control unit 12.

  The electric field strength measurement unit 14 includes a relay device 3 that establishes a connection with itself, and a measurement circuit (not shown) that measures the electric field strength of a radio signal received in a communication path between itself. . In this embodiment, an LQI (Link Quality Indication) value is used as an index of electric field strength. The control unit 12 determines the connection status with the relay device 3 based on the LQI value measured by the electric field strength measurement unit 14. For example, if the LQI value becomes zero or a value close to zero, the control unit 12 determines that the connection with the relay device 3 that has established a connection with itself is disconnected.

  As shown in FIG. 2B, the main device 2 includes a wireless transmission / reception unit 20 that transmits and receives wireless signals, and a collection unit 21 that collects and stores measurement data from each measurement terminal 1. The main device 2 includes a communication unit 22 that communicates with a management server (not shown) via a host network and a control unit 23 that controls each unit.

  The wireless transmission / reception unit 20 has the same configuration as the wireless transmission / reception unit 10 of the measurement terminal 1. The collection unit 21 includes, for example, a rewritable nonvolatile memory (for example, a flash memory), and collects the measurement data from each measurement terminal 1 by storing it for each measurement terminal 1. As the measurement data to be collected, only the latest measurement data of each measurement terminal 1 may be stored, or a plurality of measurement data received in the past may be stored.

  The communication unit 22 includes, for example, a wired LAN adapter, a wireless LAN adapter, and the like, and performs wired or wireless communication with an upper network. Therefore, for example, the measurement data of each measurement terminal 1 collected by the collection unit 21 can be transmitted to the management server via the host network. The management server can collectively manage all measurement terminals 1 including other main devices 2.

  The control part 23 consists of microcomputers (microcomputer), for example, and implement | achieves various functions by running the program stored in memory. When the wireless signal transmitted from each relay device 3 is received by the wireless transmission / reception unit 20, the control unit 23 causes the collection unit 21 to store the measurement data included in the wireless signal for each measurement terminal 1. Note that the MAC address and network address of each wireless device are stored in the memory of the control unit 23 as in the measurement terminal 1.

  The relay apparatus 3 is interposed between the measurement terminal 1 and the main apparatus 2 and relays measurement data. As shown in FIG. 2C, the relay apparatus 3 transmits and receives radio signals. A storage unit 31 that stores measurement data and a control unit 32 that controls each unit are provided. In addition, the relay device 3 includes an electric field strength measurement unit 33 that measures the electric field strength of a radio signal received by the radio transmission / reception unit 30.

  The wireless transmission / reception unit 30 has the same configuration as the wireless transmission / reception units 11 and 20 of the measurement terminal 1 and the main device 2. The storage unit 31 is composed of, for example, a rewritable volatile memory (eg, DRAM), and stores measurement data transmitted from the measurement terminal 1 that has established a connection with itself. Only the latest measurement data of each measurement terminal 1 may be stored in the storage unit 31, or a plurality of measurement data received in the past may be stored. In the present embodiment, the storage unit 31 stores measurement data for a plurality of times received in the past.

  The control unit 32 is composed of, for example, a microcomputer (microcomputer), and realizes various functions by executing a program stored in a memory. When the wireless transmission / reception unit 30 receives a wireless signal transmitted from the measurement terminal 1 that has established a connection with itself, the control unit 32 stores the measurement data included in the wireless signal in the storage unit 31. Remember every time. Note that the MAC address and network address of each wireless device are stored in the memory of the control unit 32 as in the measurement terminal 1 and the main device 2.

  The electric field strength measurement unit 33 has a measurement circuit (not shown) similar to the electric field strength measurement unit 14 of the measurement terminal 1 and is a radio signal transmitted from the measurement terminal 1 that establishes a connection with itself. Measure the electric field strength. The control unit 32 determines the connection status with the measurement terminal 1 based on the LQI value measured by the electric field strength measurement unit 33. For example, if the LQI value becomes zero or a value close to zero, the control unit 32 determines that the measurement terminal 1 that has established a connection with itself has left the connection.

  In the present embodiment, it is assumed that a wireless network has already been automatically configured between the wireless devices according to the communication path indicated by the broken line in FIG. Since the technology for automatically configuring a wireless network is well known in the art, detailed description thereof is omitted here. In the present embodiment, a radio signal including measurement data of the measurement terminal 1A is relayed by the relay devices 3B and 3A and transmitted to the main device 2. Both the radio signal including the measurement data of the measurement terminal 1B and the radio signal including the measurement data of the measurement terminal 1C are relayed by the relay devices 3C and 3A and transmitted to the main device 2.

  Hereinafter, the operation of the present embodiment will be described with reference to the drawings. As shown in FIGS. 1A and 1B, the measurement terminal 1A that establishes a connection with the relay device 3B periodically sends a radio signal including measurement data measured by itself to the relay device 3B. Send to. When the relay device 3B receives the radio signal, the relay device 3B stores the measurement data included in the radio signal in the storage unit 31 and returns a confirmation signal (ACK) notifying that the measurement data has been received to the measurement terminal 1A. At this time, the confirmation signal includes the LQI value measured by the electric field strength measurement unit 33. By receiving the confirmation signal, the measurement terminal 1A can confirm that the relay device 3B has received the measurement data, and can determine the connection status with the relay device 3B.

  In addition, the measurement terminals 1B and 1C that have established a connection with the relay device 3C periodically transmit a radio signal including measurement data to the relay device 3C, similarly to the measurement terminal 1A. Then, the relay device 3C stores the measurement data included in the radio signals from the measurement terminals 1B and 1C in the storage unit 31 and returns a confirmation signal to the measurement terminals 1B and 1C. By receiving the confirmation signal, the measurement terminals 1B and 1C can confirm that the relay device 3C has received the measurement data, and can determine the connection status with the relay device 3C. . By repeating the above operation, the measurement data of the measurement terminals 1A to 1C is accumulated in the relay apparatuses 3B and 3C.

  Here, the measurement data stored in the storage unit 31 of each relay device 3 includes a time stamp (time information) indicating the acquisition time of the measurement data. The time stamp is stored as, for example, a difference between a reference time measured by each relay device 3 itself and a time when a radio signal transmitted from each measurement terminal 1 is received, that is, an elapsed time from the reception time. In this case, each measuring terminal 1 does not need to include the time information in the measurement data and transmit it to each relay device 3, so that the transmission load of each measuring terminal 1 does not increase.

  Next, an operation in which the main apparatus 2 collects these measurement data periodically (or in accordance with a user operation) will be described. First, the main device 2 transmits a request signal for requesting transmission of the accumulated measurement data with the transmission destination as the relay device 3B. When the relay device 3A receives the request signal, the relay device 3A transmits the request signal to the relay device 3B set as the transmission destination and relays the request signal. When the relay device 3B receives the request signal, the relay device 3B reads the measurement data of the measurement terminal 1A from its own storage unit 31, and returns a reply signal including the measurement data with the main device 2 as the transmission destination. At this time, when the relay apparatus 3B has measurement data other than the measurement data included in the reply signal, the relay apparatus 3B also includes untransmitted information informing that there is untransmitted measurement data in the reply signal. When the relay device 3A receives the reply signal, the relay device 3A transmits and relays the reply signal toward the main device 2 set as the transmission destination.

  When the main apparatus 2 receives the reply signal, the main apparatus 2 collects measurement data of the measurement terminal 1A included in the reply signal. When the reply signal includes untransmitted information, the main apparatus 2 transmits a request signal including an acknowledgment signal (ACK) notifying that the measurement data has been received, with the transmission destination as the relay apparatus 3B. To do. When the relay device 3B receives the request signal, the relay device 3B reads untransmitted measurement data stored in its own storage unit 31, and returns a reply signal including the measurement data with the main device 2 as a transmission destination. Of course, when there is untransmitted measurement data, untransmitted information is included in the reply signal.

  When the above operation is repeated and there is no untransmitted measurement data stored in the storage unit 31 in the relay device 3B, the relay device 3B includes completion information informing that the transmission of the measurement data is completed in the reply signal. Send back. When the main apparatus 2 receives the reply signal, the main apparatus 2 transmits an end signal notifying that the collection of the measurement data is ended with the transmission destination as the relay apparatus 3B. Thereby, collection of the measurement data of the measurement terminal 1A is completed. Then, the main device 2 collects measurement data of the measurement terminals 1B and 1C possessed by the relay device 3C by executing the same process on the relay device 3C next.

  As described above, in the present embodiment, the measurement data of each measurement terminal 1 and the time stamp (time information) based on the time when the measurement data is measured are stored in the storage unit 31 of each relay device 3. Therefore, when the main device 2 collects the measurement data of each measurement terminal 1, even if the measurement data is lost during communication due to external noise or the like, the main device 2 transmits the measurement data to the relay device 3 again. Measurement data can be collected in the apparatus 2. In addition, the measurement data includes a time stamp (time information) based on the time measured by the measurement terminal 1. For this reason, even if the measurement data is lost during communication, when the main device 2 reacquires the lost measurement data, the main device 2 rearranges the measurement data in time series based on the time stamp included in the measurement data. be able to. That is, the main device 2 can collect measurement data along a time series regardless of the measurement data acquisition order.

  In addition, each measurement terminal 1 and each relay device 3 of the present embodiment include electric field strength measurement units 14 and 33 that measure the electric field strength of the received radio signal. Each measurement terminal 1 and each relay device 3 return a radio signal including information on the measured electric field strength (LQI value) to the measurement terminal 1 or relay device 3 that is the transmission source. For this reason, each measuring terminal 1 and each relay device 3 can grasp the connection status with the measuring terminal 1 or the relay device 3 that has established a connection with itself.

  Furthermore, in the present embodiment, the main device 2 transmits a request signal to each relay device 3, and each relay device 3 receives the request signal and stores the measurement data of the measurement terminal 1 stored in its own storage unit 31. Is sent back to the main device 2. For this reason, since the transmission timing of the measurement data from each relay apparatus 3 can be managed in the main apparatus 2, the probability that the measurement data will be lost due to the collision of the radio signals can be reduced. Even if the measurement data is lost during communication, the main device 2 can request each relay device 3 to retransmit the measurement data, so that the collection efficiency of the measurement data can be improved.

  In the present embodiment, the storage unit 31 includes a rewritable volatile memory. However, the storage unit 31 may include a rewritable nonvolatile memory such as a flash memory or an EEPROM. And each relay apparatus 3 memorize | stores the measurement data of each measurement terminal 1 which has established connection between itself in a volatile memory temporarily, and memorize | stores the said measurement data in a non-volatile memory permanently. You may let them. In this case, each relay device 3 can accumulate past measurement data of each measurement terminal 1 as long as the capacity of the nonvolatile memory permits. If there is no more free space in the non-volatile memory, you can select whether to overwrite the oldest stored measurement data with the latest measurement data or not store any more measurement data. Good. Moreover, the memory | storage part 31 itself may be comprised only with a non-volatile memory.

  By the way, when collecting the measurement data of each measurement terminal 1 as described above, the main device 2 periodically transmits a request signal to each relay device 3 or is stored in each relay device 3. It is necessary to check whether the measurement data is updated. For this reason, there is a problem that communication traffic increases during data collection.

  Therefore, when each relay device 3 receives the measurement data transmitted from the measurement terminal 1 that has established a connection with itself, the relay device 3 transmits a notification signal to that effect as the main device 2. It may be. When the main device 2 receives the notification signal, the main device 2 starts collecting measurement data by transmitting a request signal to the relay device that is the transmission source of the notification signal.

  Hereinafter, the operation when each relay device 3 transmits a notification signal will be described with reference to FIGS. For simplicity of explanation, only the case where measurement data is transmitted from the relay apparatus 3B to the main apparatus 2 will be described here. When the relay device 3B receives measurement data transmitted from the measurement terminal 1A that has established a connection with itself, the relay device 3B stores the measurement data in the storage unit 31 and notifies that the measurement data has been received. The signal is transmitted with the transmission destination as the main device 2. When the relay device 3A receives the notification signal, the relay device 3A transmits the notification signal to the main device 2 set as the transmission destination and relays it.

  When the main device 2 receives the notification signal, the main device 2 transmits a request signal for requesting transmission of the accumulated measurement data with the transmission destination as the relay device 3B. After that, as in the above embodiment, the request signal and the reply signal are alternately transmitted and received between the main device 2 and the relay device 3B until the collection of all measurement data stored in the relay device 3B is completed. . Also in the relay device 3C, when the measurement data transmitted from any one of the measurement terminals 1B and 1C established with itself is received, a notification signal is transmitted with the transmission destination as the main device 2. The same operation as described above is performed. As described above, the main device 2 can start collecting measurement data triggered by reception of the notification signal transmitted from each relay device 3 and collect measurement data of each measurement terminal 1.

  As described above, since collection of measurement data is started when the notification signal transmitted from each relay device 3 is received, it is necessary to periodically transmit a request signal from the main device 2 to each relay device 3. In addition, communication traffic during data collection can be reduced.

  Each relay device 3 determines the establishment or disconnection of the connection with the measurement terminal 1, and transmits a notification signal with the transmission destination as the main device 2 when determining that the connection has been established or disconnected. Also good. In this case, the main device 2 can always grasp the connection status between each relay device 3 and each measurement terminal 1 based on the notification signal. Note that the establishment or disconnection of the connection with the measurement terminal 1 may be determined based on, for example, the LQI value measured by the electric field strength measurement unit 33.

DESCRIPTION OF SYMBOLS 1 (1A-1C) Measuring terminal 14 Electric field strength measurement part 2 Main apparatus 3 (3A-3C) Relay apparatus 31 Memory | storage part 33 Electric field strength measurement part

Claims (5)

  One or more measurements that measure a predetermined physical quantity and wirelessly transmit measurement data including measurement values at regular intervals, and stop the communication function at least until the next measurement data is transmitted when the measurement data is transmitted A wireless network is configured by a terminal, a main device that collects the measurement data of the measurement terminal, and one or more relay devices that are interposed between the measurement terminal and the main device and relay the measurement data The relay device includes a storage unit that stores the measurement data transmitted from the measurement terminal that has established a connection with itself, and the measurement terminal measures the measurement data in the measurement data. A wireless system characterized in that time information based on the selected time is included.   The relay device transmits and receives radio signals to and from the measurement terminal, and the measurement terminal and the relay device each include an electric field strength measurement unit that measures the electric field strength of a radio signal to be received. The wireless system according to claim 1, wherein a wireless signal including information on the measured electric field strength is returned to the relay device.   The main device transmits a request signal for requesting the relay device to transmit the measurement data, and the relay device returns a response including the measurement data of the measurement terminal stored by itself when the relay device receives the request signal. 3. The wireless system according to claim 1, wherein a signal is returned to the main apparatus.   When the relay device determines the establishment or disconnection of the connection with the measurement terminal or receives the measurement data transmitted from the measurement terminal, the relay device transmits a notification signal to that effect to the main device, 4. The radio system according to claim 3, wherein the main apparatus transmits the request signal to the relay apparatus when receiving a notification signal transmitted from the relay apparatus.   5. The storage device according to claim 1, wherein the storage unit includes a nonvolatile memory, and the relay device stores the measurement data transmitted from the measurement terminal in the memory. Wireless system.

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