JP2016092737A - Communication system, control method therefor and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system capable of coping with a case when a fault occurs in a specific radio communication channel.SOLUTION: The communication system includes a plurality of communication terminals and a communication device communicating with the plurality of communication terminals. The communication device makes one of the communication terminals function as an intermediary device which intermediates communication between the communication device and the one communication terminal, when the communication between the communication device and the one communication terminal is interrupted.SELECTED DRAWING: Figure 12

Description

  The present invention relates to a communication system, a communication system control method, and a program.

  In recent years, as a communication technology for smart meters, HEMS (Home Energy Management System) and BEMS (Building Energy Management System), it can realize ultra-low power consumption, downsizing, and cost reduction (in Japan, 920 MHz as a sub-giga band) A wireless sensor network system is receiving attention.

  The 920 MHz band is less attenuated due to radio wave propagation than the 2.4 GHz band and 5 GHz band used in wireless LAN (Local Area Network), etc., and is easy to get around obstacles. There is. Therefore, compared to a wireless LAN, a network can be configured with a larger number of terminals.

  The IEEE (Institute of Electrical and Electronics Engineers, Inc.) 802.15.4 standard is basically an asynchronous CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) control method. Type access control method is adopted. When the number of terminals is large, such as several hundred to several thousand, if communication is performed using a synchronous network system that is not a CSMA / CA access control system, it is difficult to set a schedule such as a superframe or a beacon. Therefore, in a large-scale network, a CSMA / CA access control asynchronous network method is used. However, in the CSMA / CA access control network, access rights are acquired in consideration of collisions with other terminals, and therefore there is a problem that the delay time of data transmission is not guaranteed.

  In a system with a small amount of control information such as a sensor network system, the overhead such as preamble and header becomes relatively large compared to the control information, and it is inefficient to transmit the control information individually to each wireless device. Become. In addition, a transmission time limit per unit time may be imposed, and in a large-scale network, it becomes difficult to individually transmit to all of many devices.

  Therefore, in order to perform efficient control to a large number of wireless devices, a technology is known in which control information for each device is packed from a wireless coordinator using a multicast frame or a broadcast frame and transmitted simultaneously in one frame. It has been.

  However, when a plurality of wireless devices that have received a broadcast or multicast frame try to transmit data frames in response that notify themselves that they have received correctly in order to improve communication reliability, a collision occurs. . For this reason, it is necessary to control the transmission of responses in consideration of collisions with other terminals. However, in the case of a large-scale network with hundreds to thousands of terminals, the collision probability increases and collisions are detected. In such a case, the number of insertions for a predetermined time (back-off time) increases, leading to an increase in power consumption. In addition, the time required until the data transmission ends normally is prolonged, and the transmission time becomes longer due to the insertion of the back-off time, and there is a possibility that the response cannot be transmitted due to the transmission time limitation described above.

  From such a background, it is desired to develop a technology capable of reducing the collision probability in a response in a system that performs simultaneous data transmission from a communication device to a plurality of communication terminals and responds from each of the plurality of communication terminals. ing. At that time, it is desired not to increase communication data and size transmitted from the communication device.

  In addition, a transmission time limit may be imposed on a wireless device in the 920 MHz band as described above. For example, according to the standard ARIB STD-T108 of the radio industry (ARIB), the total frequency of transmission time per device in a center frequency of 922.4 MHz to 928.0 MHz is suppressed to 360 seconds or less. It is stipulated that it must be. For this reason, the number of frames that the wireless coordinator can transmit to each wireless device is limited, and in a large-scale network with hundreds to thousands of terminals, there is a problem that transmission cannot be performed to all wireless devices due to transmission time limitations. .

  Therefore, in order to realize control for many wireless devices, there is a technique in which a wireless coordinator packs data of each wireless device together using a multicast frame or a broadcast frame, and transmits them simultaneously in one frame. However, since multicast frames and broadcast frames generally do not specify transmission of ACK packets to inform the transmission source that frames have been received, it is possible to know whether or not each wireless device has received correctly. There is a problem that you can not.

  Therefore, in order for the wireless coordinator to know whether or not each wireless device has received correctly, it is necessary for each wireless device to transmit a data frame for notifying that it has received correctly. However, in the case of a large-scale network with hundreds to thousands of terminals, if a plurality of received wireless devices attempt to transmit data frames for notification that they have been received correctly all at once, a frame collision will occur. End up.

  In the CSMA / CA network, carrier detection is performed to check whether another wireless device is currently communicating before the wireless device transmits data. If no carrier is detected, data transmission is started. If a carrier is detected, retransmission is performed after a predetermined time interval (backoff time). However, in this method, in the case of a large-scale network having hundreds to thousands of terminals, the probability of frame collision also increases, so the number of times to insert the back-off time increases, and data transmission ends normally. There are problems that it takes a long time or transmission is not possible due to the time limit of the back-off time. In addition, the wireless sensor network system is required to reduce power consumption, and in order to save power, it is effective to suppress an increase in the number of back-off time insertions caused by an increase in the frame collision probability.

  In relation to transmission in consideration of collision with other terminals, Patent Document 1 discloses a technique for reducing the packet discard rate without significantly modifying the system based on the existing IEEE 802.15.4 standard. Is disclosed. Specifically, in a wireless packet communication system that performs data packet communication between a wireless base station and a wireless terminal that perform wireless packet communication using a common wireless channel, data packet transmission is performed in a communication collision determination step a predetermined number of times. If it is determined to be impossible, the packet is retained instead of being discarded, and a re-determination step for re-determining whether or not there is a communication collision, It is described that a back-off time is set and the process returns to the re-determination step to determine the presence or absence of a communication collision.

  However, in the wireless sensor network system, low power consumption is demanded. However, in the technique disclosed in Patent Document 1, the wireless device must always perform carrier detection during collision determination. There is a problem that power consumption is not sufficient in that it cannot be transferred to.

  In addition, a wireless sensor network system according to the same applicant as the present application is a system that transmits a control data broadcast frame that is a multicast frame or a broadcast frame in order to simultaneously transmit control data from a coordinator to a plurality of devices. This is because the control data broadcast response frame, which is a data frame for notifying the coordinator that the plurality of devices have received the control data broadcast frame and received the control data correctly, has been received. Is a transmission system. Then, the plurality of received devices calculate the waiting time until the control data simultaneous response frame is transmitted based on their own address information, and measure the transmission timing as in time division transmission, thereby transmitting the response. A network system that reduces the collision rate of frames and consumes less power is provided.

  However, in this wireless sensor network system, when a failure occurs in the communication path between a specific device and the coordinator and the device always fails to receive a control data broadcast frame that is a broadcast frame, There is a problem that it is impossible to deal with a failure that a control data simultaneous response frame is not returned from the device.

  Therefore, the present invention has been made in view of the above-described problems of the prior art, and in a large-scale wireless sensor network system that performs asynchronous communication, a wireless coordinator uses a multicast frame or a broadcast frame to An object of the present invention is to provide a communication system that can cope with a failure in a specific wireless communication path when transmitting control data to the wireless device.

  In order to solve the above-described problem, a communication system according to the present invention described in claim 1 is a communication system including a plurality of communication terminals and a communication device that communicates with the plurality of communication terminals, When communication with one communication terminal is interrupted, the communication device replaces any one of the plurality of communication terminals other than the one communication terminal with the communication device and the one communication terminal. It is made to function as an intermediary device that mediates communication between the two.

  ADVANTAGE OF THE INVENTION According to this invention, the communication system which can respond also when a failure generate | occur | produces in a specific wireless communication path can be obtained.

It is a figure which shows an example of the star-type network comprised by one radio | wireless coordinator and three radio | wireless devices. FIG. 2 is a diagram illustrating an example of a frame transmitted from a wireless coordinator and a wireless device in the star network illustrated in FIG. 1. It is a figure which shows an example of the frame format in IEEE802.15.4 standard. 1 is a diagram illustrating an example of a cluster tree type network including one wireless coordinator, four relay apparatuses (relay devices), and five terminal apparatuses (end devices). FIG. It is a figure which shows an example of the hardware constitutions of the wireless device with which the communication system which concerns on this embodiment is provided. In the communication system which concerns on this embodiment, it is the figure which illustrated the transmission timing of the control data frame and response frame in the case of transmitting with a broadcast frame. It is the figure which illustrated the structure of the control data frame which a radio coordinator transmits to each radio device simultaneously. In the communication system which concerns on this embodiment, it is the figure which illustrated about device ID (Identifier) and control information which comprise a data part among the control data frames which a radio coordinator transmits to each of a radio device simultaneously. In the communication system which concerns on this embodiment, it is a figure which shows an example of the star type | mold network comprised by one radio | wireless coordinator and four radio devices. It is a functional block diagram of a radio coordinator and a radio device that constitute the communication system according to the present embodiment. In a star-type network consisting of one wireless coordinator and three wireless devices, an example is shown in which radio communication is interrupted due to a radio wave failure in the wireless communication path between the wireless coordinator and the wireless device. FIG. In a star-type network consisting of one wireless coordinator and three wireless devices, if a radio interference occurs in the wireless communication path between the wireless coordinator and the wireless device and the wireless communication is interrupted, a specific wireless It is a figure which shows the example in the case of making a device function as an intermediary device. It is a figure which shows the example which adds as a data byte the data which shows making a specific radio | wireless device function as an intermediary device at the head of the frame format of a broadcast frame. It is a figure which shows the example which transmits frame data with respect to other wireless devices other than a mediation device from a mediation device, when a response frame is not transmitted from a specific radio device. Based on the response to the first broadcast frame, the wireless device that has lost communication is determined, the next broadcast frame is transmitted to the wireless device and communication device that have lost communication, and the wireless device that has lost communication other than itself It is a figure which shows the example which performs unicast communication with respect to a device. FIG. 16 is a diagram illustrating an example in which only a wireless device and an intermediary device that cannot communicate in the second broadcast frame in FIG. 15 are set in the frame. FIG. 5 is a diagram illustrating an example of a frame transmitted from a wireless coordinator and a relay device by the cluster tree type network in FIG. 4. It is a figure which shows an example of the frame format in IEEE802.15.4 standard regarding the communication system which concerns on this embodiment. In the data part (Data) of the frame format of FIG. 18, it is a figure which shows the specific numerical value of device ID and control information which are the information to each wireless device. Operation after the wireless coordinator transmits the control data broadcast frame, receives all the control data broadcast frames transmitted by the relay device, and determines that each wireless device has received the control data broadcast frame correctly. It is a flow. Operation after the wireless coordinator transmits the control data broadcast frame, receives all the control data broadcast frames transmitted by the relay device, and determines that each wireless device has received the control data broadcast frame correctly. It is a flow. It is a figure which shows an example of the control data simultaneous transmission frame which the radio coordinator which comprises the communication system which concerns on this embodiment transmits. FIG. 23 is a diagram illustrating specific numerical values of device ID, control information, and relay information that are information to each wireless device in the data portion (Data) of the frame format of FIG. 22.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably. Hereinafter, although this embodiment is described, this embodiment is not limited to the embodiment described below. In the embodiment described below, a network system in which a communication device and a plurality of communication terminals are configured in a star shape will be described as an example of a communication system.

  First, a star network including one wireless coordinator and three wireless devices, and a frame transmitted from the wireless coordinator and the wireless device in the star network will be described. FIG. 1 is a diagram illustrating an example of a star network including one wireless coordinator and three wireless devices. FIG. 2 is a diagram illustrating an example of a frame transmitted from the wireless coordinator and the wireless device in the star network illustrated in FIG. The star type has a feature that the delay time of data transmission is small.

  The wireless coordinator 11 selects the wireless device 12 and transmits a control data frame to the wireless device 12 as shown in FIG. When the wireless device 12 receives the control data frame transmitted from the wireless coordinator 11, the wireless device 12 transmits an ACK packet for notifying the wireless coordinator 11 that the control data frame has been received. Thereafter, the wireless coordinator 11 exchanges the same processing with the wireless device 13 and the wireless device 14 individually.

  Here, a frame format in the IEEE 802.15.4 standard, which is a control data frame transmitted from the wireless coordinator 11 to each wireless device 12 to 14, will be described. FIG. 3 is a diagram showing an example of a frame format in the IEEE 802.15.4 standard. The other data frames have the same configuration. The control data frame includes a preamble, a SFD (Start Frame Delimiter), and a physical layer header (PHY Header). The control data frame includes a MAC (Media Access Control) layer header (MAC Header), a data part (Data), and an FCS (Frame Check Sequence).

  The preamble is a bit string for the receiving side to synchronize. SFD is a bit string representing the start of a control data frame. The physical layer header is information related to the physical layer in the OSI (Open Systems Interconnection) reference model, and includes a frame length field. The MAC layer header includes a frame control field, a data sequence number, and address information. The data part here includes control information. The FCS is error correction information added to check whether there is an error in the received control data frame.

  As can be seen from the frame format shown in FIG. 3, 23 bytes of wireless communication data (Preamble, SFD, PHY Header, MAC Header, FCS) are required for 10 bytes of control data (data portion). There is a system with a small amount of control data such as a so-called sensor network using a smart meter or the like with a built-in sensor as a wireless device. In the case of such a system, the size of data for wireless communication is larger than that of the data part, and it is very inefficient to transmit control data individually to each wireless device as shown in FIG. It is.

  Further, a cluster tree type network including one wireless coordinator, four relay devices, and five end devices will be described. FIG. 4 is a diagram illustrating an example of a cluster tree type network including one wireless coordinator, four relay apparatuses (relay devices), and five terminal apparatuses (end devices). The cluster tree type has a feature that it has a wider communication range than the star type and is resistant to radio interference generated in a specific wireless communication path.

  Returning to FIG. 1, the communication system shown in FIG. 1 includes a plurality of communication terminals and a communication device that communicates with the plurality of communication terminals, and a network is constructed by these devices. This network has a star shape in which a plurality of communication terminals are connected radially from the communication device, centering on the communication device. The star type network is advantageous in that it has a feature that the delay time of data transmission is small. However, the network topology in this embodiment is not limited to the star type, and may have other network topologies such as the above-described cluster tree type as another embodiment. Incidentally, the cluster tree type has a parent-child relationship in a star type network.

  FIG. 1 shows a communication system 10 configured in a star shape in which wireless devices 12, 13, and 14 as three communication terminals are wirelessly connected to a wireless coordinator 11 as a communication device.

  Examples of the wireless coordinator 11 include a wireless base station, a router, a PC (Personal Computer), a workstation, and a tablet terminal. In the present embodiment, the wireless coordinator 11 can transmit, as data, a control data frame for controlling a wireless device to a plurality of wireless devices 12, 13, and 14 that are wirelessly connected. The contents of the control data frame will be described later. The data is not limited to the control data frame and may be any data frame.

  Examples of the wireless devices 12, 13, and 14 include a device equipped with the wireless module 50 (FIG. 5) as a functional component, a smartphone, a tablet terminal, a game machine, and a PDA (Personal Digital Assistant). In addition, examples of the device include a watt-hour meter (smart meter) having a communication function in the meter, a temperature / humidity sensor, an illuminance sensor, a flow sensor, illumination, a switch, a power supply device, and the like. it can. Each of the wireless devices 12, 13, and 14 can receive a control data frame transmitted from the wireless coordinator 11 directly or via an access point (not shown).

  When each of the wireless devices 12, 13, and 14 receives the control data frame transmitted from the wireless coordinator 11, the wireless device 12, 13, and 14 transmits a response indicating that the wireless device 12, 13, and 14 have been correctly received to the wireless coordinator 11. Thereby, the wireless coordinator 11 can know that the wireless devices 12, 13, and 14 have correctly received the control data frame. If it cannot be received correctly, no response is sent.

  Communication between the wireless coordinator 11 and the plurality of wireless devices 12, 13, and 14 can be performed using a frequency such as a 920 MHz band, a 2.4 GHz band, and a 5 GHz band. When the communication system 10 is an EMS (Energy Management System), it is possible to suitably use a frequency in the 920 MHz band that has a small attenuation due to radio wave propagation, easily enters an obstacle, and has a high area coverage. The EMS is a system having a wireless communication function for performing power visualization, power saving control, storage battery control, and the like. This EMS is HEMS (Home EMS) for homes, FEMS (Factory EMS) for factories, BEMS (Building EMS) for commercial buildings, and CEMS (Community EMS) for the entire region. be called.

  In the embodiment described below, the wireless coordinator 11 and the plurality of wireless devices 12, 13, and 14 are wirelessly connected. However, as another embodiment, the coordinator and the plurality of devices may be connected to each other by wire. The number of coordinators and the number of devices may be any number.

  FIG. 5 is a diagram illustrating an example of a hardware configuration of a wireless device included in the communication system according to the present embodiment. Since the wireless device 12, the wireless coordinator 11, and the other wireless devices 13 and 14 can adopt the same configuration in performing wireless communication, only the wireless device 12 will be described here.

  The wireless device 12 includes a wireless module 50. The wireless module 50 includes a CPU (Central Processing Unit) 51 that controls the wireless device 12 and a memory 52 that stores software programs and data to be executed by the CPU 51 and provides a work area to the CPU 51. The wireless module 50 includes a wireless circuit 53 for performing wireless communication and an antenna 54. The wireless module 50 also includes an external interface 55 for receiving input of power and data input obtained from a sensor or the like mounted on the wireless device 12 and controlling the sensor or the like.

  The memory 52 includes an EEPROM (Electrically Erasable Programmable Read Only Memory) 56 that stores setting information and the like. The memory 52 includes a RAM (Random Access Memory) 57 that provides a work area to the CPU 51. Further, the memory 52 includes a flash memory 58 that stores received data and the like.

  In the wireless device 12, the CPU 51 executes software, transmits a response to the control data frame from the wireless coordinator 11, acquires data from a sensor or the like, and instructs the wireless circuit 53 to transmit as a data frame. be able to. The radio circuit 53 modulates a carrier wave, puts a data frame thereon, sends the data frame to the antenna 54, and wirelessly transmits from the antenna 54. Further, the radio circuit 53 can receive a control data frame from the radio coordinator 11 via the antenna 54. The radio circuit 53 demodulates the carrier wave, extracts a control data frame, and sends the control data frame to the CPU 51 to execute processing such as transmission of the response and data acquisition.

  Next, the operation of the communication system according to the present embodiment will be specifically described. In the present embodiment, the wireless coordinator 11 packs control information for a plurality of wireless devices as a multicast frame or a broadcast frame, etc., and transmits them simultaneously to the plurality of wireless devices 12, 13, and 14. In each of the wireless devices 12, 13, and 14, if their own terminal identification information is included in the packed control data frame, control information addressed to itself is included. Hereinafter, the communication processing performed between the wireless coordinator 11 and the plurality of wireless devices 12, 13, and 14 in the communication system according to the present embodiment will be described in detail with reference to FIGS.

  FIG. 6 is a diagram illustrating transmission timings of a control data frame and a response frame in the case where transmission is performed using a broadcast frame in the communication system according to the present embodiment. The wireless coordinator 11 according to the present embodiment broadcasts control data frames to a plurality of wireless devices 12, 13, and 14 (hereinafter also referred to as wireless device 1, wireless device 2, and wireless device 3). Control information can be transmitted to For this reason, unlike the case of the star-type network shown in FIG. In addition, since control information for a plurality of wireless devices 12, 13, and 14 is packed in a frame, a large number of wireless devices can be efficiently controlled even if each has a small amount of control information. Further, since transmission is performed in one frame to a plurality of wireless devices, control information can be transmitted to all wireless devices within the time even when a transmission time limit is imposed.

  In addition, when each of the wireless devices 12, 13, and 14 according to the present embodiment correctly receives the control data frame, the wireless device 12, 13, and 14 transmits a response frame that notifies the wireless coordinator 11 that it has been received correctly as a data frame. Thus, since the ACK packet is not defined for the broadcast frame, the conventional problem that the wireless coordinator cannot know whether or not each wireless device has received the control data frame correctly is solved. At this time, each of the wireless devices 12, 13, and 14 does not transmit a response frame all at once in response to receiving the control data frame, and as shown in FIG. 3 is transmitted while being shifted by a predetermined time. Thereby, it is possible to reduce the probability of a collision that occurs as a result of a plurality of wireless devices transmitting response frames substantially simultaneously.

  FIG. 7 is a diagram illustrating the configuration of a control data frame that the wireless coordinator 11 transmits to each of the wireless devices 1, 2, and 3 simultaneously. This is also an example of a frame format in the IEEE 802.15.4 standard, as in FIG. 3, and the configuration of the control data frame is the same as the conventional configuration shown in FIG. However, the data portion is different from the configuration of FIG. The content of the frame includes terminal identification information (device ID) and control information for each of the wireless devices 1, 2, and 3. These pieces of information are packed into one, put in a data part (Data) in the frame, and broadcasted in a broadcast frame.

  Note that the frame for simultaneous transmission is not limited to the broadcast frame used for transmitting the frame simultaneously to all wireless devices on the network. As other frames, multicast frames used for transmitting frames to a plurality of predetermined wireless devices at the same time can be used. That is, a multicast frame or a broadcast frame can be used.

  Next, the device ID and control information will be described in detail with reference to FIG. FIG. 8 is a diagram illustrating a device ID and control information constituting a data portion in a control data frame that is simultaneously transmitted to each wireless device by the wireless coordinator in the communication system according to the present embodiment. The device ID is terminal identification information for identifying each of the wireless devices 1, 2, and 3, and indicates a unique ID. In FIG. 8, 0xff01, 0xff02, and 0xff03 are assigned, respectively. Here, an ID is assigned to each wireless device, but a plurality of wireless devices may be divided into several groups, and an ID may be assigned to each group. In the embodiment described here, the terminal identification information is a device ID, but any information such as a serial number, a UUID (Universally Unique Identifier), an address, or the like can be used as long as it can identify a wireless device.

  The control information is information related to control performed by the wireless devices 1, 2, and 3 on a unit such as a sensor provided in the own device. When the wireless devices 1, 2, and 3 are devices that control a switch for switching on / off of an LED (Light Emitting Device) power source, the unit is a light on / off switch. Therefore, the control information is information for turning on or off. In the example of FIG. 8, lighting is set to 0x0001 and lighting is set to 0x0000. Therefore, in the example illustrated in FIG. 8, when the wireless devices 1 and 2 receive the control data frame, they turn on the LED power switch and transmit a response frame to the wireless coordinator 11 after the adjusted time. . On the other hand, the wireless device 3 turns off the LED power switch, and transmits a response frame to the wireless coordinator 11 after the adjusted time.

  Here, in the example in which the control information for the three wireless devices 1, 2, and 3 shown in FIGS. 7 and 8 is included in the frame, the case where the fourth wireless device 15 (wireless device 4) exists is illustrated. 9 will be used for explanation. FIG. 9 is a diagram illustrating an example of a star-type network including one wireless coordinator and four wireless devices in the communication system according to the present embodiment.

  In this case, since the control data frame is broadcast, the wireless device 4 can also receive the control data frame broadcast from the wireless coordinator 11. However, the wireless device 4 whose own device ID is not included in the data part does not need to return a response frame, and rather it is better not to transmit it in order to avoid frame collision probability and bandwidth consumption. Therefore, in a preferred embodiment, when receiving the control frame data, the wireless devices 1, 2, 3, 4 further check all the device IDs included in the data portion of the frame, and their device IDs are A response frame is returned only if it exists. If the device ID is not included, the response frame is not transmitted.

  Next, the configuration of the wireless coordinator and the wireless device that configure the communication system according to the present embodiment will be described. FIG. 10 is a functional block diagram of a wireless coordinator and a wireless device that constitute the communication system according to the present embodiment. Since the wireless devices 13 and 14 are the same as the wireless device 12, the description thereof is omitted here. The wireless coordinator 11 includes a data transmission unit 110 that transmits control data frames to a plurality of wireless devices 12, 13, and 14 simultaneously. The data transmission unit 110 according to the present embodiment includes a device ID and control information for identifying each wireless device in the data part of the control data frame to be transmitted. The data transmission unit 110 transmits the control data frame to each of the wireless devices 12, 13, and 14 as a multicast frame or a broadcast frame.

  The wireless device 12 includes a data reception unit 120 that receives a control data frame transmitted from the data transmission unit 110 of the wireless coordinator 11. Further, the wireless device 12 includes a response transmission unit 121 that transmits a response frame to the reception of the control data frame to the wireless coordinator 11. Specifically, the response transmission unit 121 searches the received control data frame for the device ID of the wireless device 12 that is the device itself, and when the device ID of the device itself is found, the response transmission unit 121 transmits the response frame to the wireless coordinator. 11 to send. Further, the wireless device 12 includes a data analysis unit 122 that determines whether or not the own device is designated to function as an intermediary device described later in the received control data frame.

  In the communication system described above, if a radio interference as shown in FIG. 11 occurs in a wireless communication path between a specific device (for example, the wireless device 12 in FIG. 1) and the wireless coordinator 11, wireless communication is not possible. If the communication is interrupted, the subsequent communication control cannot be performed. FIG. 11 shows a case where radio communication is interrupted due to a radio wave interference in a wireless communication path between a wireless coordinator and a wireless device in a star network including one wireless coordinator and three wireless devices. It is a figure which shows the example of.

  In this case, the wireless coordinator 11 assumes such a situation, and causes any one of the communication terminals under management other than the communication terminal that has lost communication to function as an intermediary device (mediation device). For example, in the case of FIG. 11, if the wireless communication path from the wireless device 13 to the wireless device 12 is secured by causing the wireless device 13 to function as an intermediary device, control data for the wireless device 12 can be transmitted. . This is shown in FIG. FIG. 12 is a diagram illustrating a star network including one wireless coordinator and three wireless devices. And it is a figure which shows the example in the case of making a specific wireless device function as an intermediary device, when a radio wave failure generate | occur | produces in the wireless communication path between a wireless coordinator and a wireless device, and wireless communication stops.

  As a first method, the wireless device arranged at the end of the data format of the broadcast frame shown in FIG. 7 can be specified by determining in advance that it functions as an intermediary device. In addition, as a mediating device designation method, it is possible to designate a wireless device arranged at a predetermined specific location from wireless device information sequentially arranged in the payload of the broadcast frame. For example, the first or last placed wireless device in the payload can function as an intermediary device. As a result, the designated device functions as an intermediary device.

  Further, as shown in FIG. 13, data indicating that a specific wireless device functions as an intermediary device (data indicating which device becomes an intermediary device) can be added to the broadcast frame. Specifically, it can be specified by adding 1 byte as an information byte (Information) to the head of the frame format. FIG. 13 is a diagram illustrating an example in which data indicating that a specific wireless device functions as an intermediary device is added as an information byte to the head of the frame format of a broadcast frame.

  In the second method, as shown in FIG. 14, a specific wireless device functions as an intermediary device, and the intermediary device receives a broadcast frame from the radio coordinator. Then, after a predetermined time has elapsed, a process of transmitting a broadcast frame having the same frame data (payload) as the received broadcast frame is performed. FIG. 14 is a diagram illustrating an example in which a broadcast frame is transmitted from an intermediary device to a wireless device other than the intermediary device when a response frame is not transmitted from a specific wireless device.

  In FIG. 14, when a failure occurs in a specific wireless communication path and communication with a specific wireless device is interrupted, the same payload data is transmitted from the mediation device in addition to the transmission from the wireless coordinator. That is, the wireless coordinator transmits control data of each wireless device to a plurality of wireless devices simultaneously using a multicast frame or a broadcast frame. In this case, by changing the radio wave propagation path, it is possible to perform data communication with the wireless device that has become unable to communicate with the wireless coordinator.

  The third method is a case where the wireless device information sequentially arranged in the payload of the broadcast frame is two of the mediation device and other wireless device information. Specifically, the broadcast frame transmitted by the mediation device is transmitted by unicast to a wireless device other than the mediation device. When there are two or more pieces of wireless device information, they are transmitted by broadcast.

  When the wireless device information sequentially arranged in the payload of the broadcast frame is two mediator devices and other wireless devices, the broadcast frame transmitted by the mediation device is only the wireless device other than the mediation device. Therefore, it transmits to the address by unicast. This makes it possible to reliably transmit information in the case of unicast communication. If there are two or more pieces of wireless device information, they are transmitted by broadcast communication.

  Further, the wireless device that is disconnected is determined based on the response to the first broadcast frame. FIG. 15 shows an example in which the next broadcast frame is transmitted to the wireless device and the mediating device whose communication is cut off, and the mediating device performs unicast communication with the wireless device whose communication is cut off other than itself.

  In FIG. 15, the mediation device is not specified in the first broadcast frame, and the wireless coordinator receives a control data simultaneous response frame from each device. Then, it is determined which wireless device is in communication. Further, in the second broadcast frame, as shown in FIG. 16, only the wireless device 2 and the mediating device that cannot communicate are set in the frame. Then, the mediation device that has received the frame transmits data to the wireless device 2 that is a wireless device other than itself by unicast communication.

  The mediation device receives the ACK response from the wireless device 2, and then, as the mediation device of the wireless device 2, the wireless device 3 transmits a response frame to the wireless coordinator. As a result, the control data can be reliably transmitted from the wireless coordinator to the wireless device that has failed due to the failure.

  Hereinafter, preferred embodiments of the present invention will be described. Here, a network configured in the above-described cluster tree type will be described with reference to FIG. 4 again. FIG. 4 is a diagram illustrating an example of a cluster tree type network including one wireless coordinator, four relay apparatuses (relay devices), and five terminal apparatuses (end devices). The cluster tree type has a feature that it has a wider communication range than the star type and is resistant to radio interference generated in a specific wireless communication path. The network configuration used in the present embodiment is a cluster tree type, but may be a mesh type. Furthermore, the number of relay devices and end devices is 4 and 5 respectively in this embodiment, but of course, it may be 4 and 5 or more, respectively.

  Next, an example of a frame transmitted from the wireless coordinator and the relay device by the cluster tree type network in FIG. 4 will be described. FIG. 17 is a diagram illustrating an example of a frame transmitted from the wireless coordinator and the relay device by the cluster tree type network in FIG.

  The wireless coordinator 11 includes a frame including control information for the relay devices 21 to 24 (hereinafter also referred to as relay devices 1 to 4) and further to the end devices 31 to 35 (hereinafter also referred to as end devices 1 to 5). A control data broadcast frame that is a broadcast frame is transmitted. By transmitting all at once in this way, the time for transmitting data for wireless communication such as a preamble can be reduced, so that data can be transmitted efficiently even in the 920 MHz band where a transmission time limit is imposed. Therefore, it is possible to make it difficult to cause a problem that data cannot be transmitted to each device due to a transmission time limitation, which is likely to occur in a large-scale network having hundreds to thousands of terminals. Furthermore, since transmission time can be reduced by transmitting all at once, power consumption can be reduced.

  When each relay device correctly receives the control data broadcast frame from the radio coordinator, each relay device sends a relay frame having a payload composed of the frame data (payload) of the received control data broadcast frame to each end device. To send. That is, control data is retransmitted from a relay device installed at a location different from the wireless coordinator. As a result, even if a failure occurs in a specific wireless communication path, the end device can receive control data more reliably as compared with the case where the wireless device is retransmitted.

  Further, the radio coordinator confirms that the relay device has correctly received the control data by the control data transmitted from the relay device. Therefore, the broadcast frame does not specify an ACK packet that informs the sender that the frame has been received, so the problem that the wireless coordinator cannot recognize whether each relay device has received control data correctly has been solved. Is done.

  Next, an example of a frame format in the IEEE 802.15.4 standard related to the communication system according to the present embodiment will be described. FIG. 18 is a diagram showing an example of a frame format in the IEEE 802.15.4 standard related to the communication system according to the present embodiment. The device ID and control information of each wireless device are packed into the data part (Data) in FIG. 18 and transmitted in a broadcast frame.

  Specific values in the data part (Data) of FIG. 18 are shown in FIG. FIG. 19 is a diagram illustrating specific numerical values of a device ID and control information, which are information to each wireless device, in the data portion (Data) of the frame format of FIG.

  The device ID is information indicating unique IDs of the end devices 1 to 5 and the relay devices 1 to 4. End device 1 is assigned 0xff01, end device 2 is assigned 0xff02, end device 3 is assigned 0xff03, end device 4 is assigned 0xff04, and end device 5 is assigned 0xff05. Relay device 1 is assigned 0xfe01, relay device 2 is assigned 0xfe02, relay device 3 is assigned 0xfe03, and relay device 4 is assigned 0xfe04. Here, an ID is assigned to each device, but an ID may be assigned to each group.

  Further, the control information is information on a device that is controlled by each wireless device. For example, as in the above-described example, it is assumed that a switch for switching on / off of the LED power supply is assigned to each wireless device, which is turned on at 0x0001 and turned off at 0x0000. In this case, when each wireless device correctly receives the control data broadcast frame shown in FIG. 19, the LEDs controlled by the end devices 1 and 2 and the relay devices 1 and 4 are controlled to be in a lighting state. Further, the LEDs controlled by the end devices 3, 4, 5 and the relay devices 2, 3 are controlled to be turned off.

  Next, after the wireless coordinator transmits the control data broadcast frame, it receives all the control data broadcast frames transmitted by the relay device, and determines that each wireless device has received the control data broadcast frame correctly. The operation will be described. FIG. 20 shows the process until the wireless coordinator receives all the control data broadcast frames transmitted by the relay device after transmitting the control data broadcast frame and determines that each wireless device has correctly received the control data broadcast frame. It is a flow which shows the operation | movement of.

  Note that the transmission frame transmitted by the operation of FIG. 20 is the frame shown in FIG. 17 described above. In FIG. 20, first, in step S201, the wireless coordinator sets a waiting time x for receiving a control data broadcast frame from each relay device and waiting. Here, x = 100 msec. Thereafter, in step S202, the wireless coordinator packs the device ID and control information of each wireless device shown in FIG. 18 and transmits a control data broadcast frame that is a broadcast frame.

  In step S203, after transmission, the radio coordinator determines whether or not the x time set in step S201 has elapsed. If it is determined that x time has elapsed (step S203: YES), the process proceeds to step S204. In step S204, as shown in FIG. 17, it is determined whether or not a control data broadcast frame, which is a relay frame transmitted by each relay device in the order of relay devices 1, 2, 4, and 3, has been received.

  When all four control data broadcast frames transmitted by the relay device have been received (step S204: YES), the wireless coordinator determines that the transmission of the control data broadcast frame transmitted by itself is successful. If all four control data broadcast frames transmitted by the relay device are not received (step S204: NO), the wireless coordinator determines that transmission of the control data broadcast frame transmitted by itself has failed.

  Therefore, the broadcast frame does not specify an ACK packet that informs the sender that the frame has been received, so the problem that the wireless coordinator cannot recognize whether each relay device has received control data correctly has been solved. Is done. Furthermore, since the relay device retransmits the control data broadcast frame, it is possible to cope with a failure in a specific wireless communication path.

  Next, after the wireless coordinator transmits the control data broadcast frame, it receives all the control data broadcast frames transmitted by the relay device, and determines that each wireless device has received the control data broadcast frame correctly. The operation will be described. FIG. 21 shows the process until the wireless coordinator receives all the control data broadcast frames transmitted by the relay device after transmitting the control data broadcast frame and determines that each wireless device has correctly received the control data broadcast frame. It is a flow which shows the operation | movement of.

  Note that the transmission frame transmitted by the operation of FIG. 21 is the frame shown in FIG. 17 described above. In FIG. 21, first, in step S211, the radio coordinator sets a waiting time x for receiving control data broadcast frames from each relay device and waiting. Here, x = 100 msec. Thereafter, in step S212, the wireless coordinator packs the device ID and control information of each wireless device shown in FIG. 18 and transmits a control data broadcast frame that is a broadcast frame.

  In step S213, after transmission, the radio coordinator determines whether or not the x time set in step S211 has elapsed. When it is determined that x time has elapsed (step S213: YES), the process proceeds to step S214. In step S214, as shown in FIG. 17, it is determined whether or not a control data broadcast frame, which is a relay frame transmitted by each relay device in the order of relay devices 1, 2, 4, and 3, has been received.

  When all four control data broadcast frames transmitted by the relay device have been received (step S214: YES), the wireless coordinator determines that the transmission of the control data broadcast frame transmitted by itself is successful, and ends the processing. . If all four control data broadcast frames transmitted by the relay device are not received (step S214: NO), the wireless coordinator determines that transmission of the control data broadcast frame transmitted by itself has failed. And it returns to step S212 again and transmits a control data simultaneous transmission frame.

  As described above, in this embodiment, the wireless coordinator retransmits the control data broadcast frame until all the relay frames transmitted by the relay device are received. Therefore, even if a failure occurs in a specific wireless communication path, the relay device and the end device can reliably receive the control data.

  As described above, FIG. 18 is a diagram illustrating an example of a frame format in the IEEE 802.15.4 standard related to the communication system according to the present embodiment, and is an example of a control data broadcast frame transmitted by the wireless coordinator. When the wireless coordinator designates a relay device, in the example of FIG. 18, it is determined in advance that the four device IDs arranged last in the data portion (Data) are relay devices. In other words, the relay device specifies that a device arranged at a predetermined specific location of device information sequentially arranged in the payload of the control data broadcast frame is to perform. Thereby, the relay device can be dynamically changed for each frame.

  Next, an example of a control data simultaneous transmission frame transmitted by the wireless coordinator configuring the communication system according to the present embodiment will be described. FIG. 22 is a diagram illustrating an example of a control data simultaneous transmission frame transmitted by the wireless coordinator configuring the communication system according to the present embodiment. In the data part (Data) of FIG. 18, the ID of each wireless device, control information, and relay information indicating whether or not the device is a relay device are packed into a broadcast frame and transmitted.

  Specific values in the data part (Data) of FIG. 18 are shown in FIG. FIG. 23 is a diagram illustrating specific numerical values of device ID, control information, and relay information, which are information to each wireless device, in the data portion (Data) of the frame format of FIG.

  The relay information is information indicating whether each wireless device is a relay device or an end device. For example, if the relay information is 0x0001, it is a relay device, and if it is 0x0000, it is an end device. Thereby, the relay device can be dynamically changed for each frame.

  In other words, information indicating that the relay device is a relay device that performs mediation processing is added to the device information that is sequentially arranged in the payload of the control data broadcast frame. Thereby, the relay device can be dynamically changed for each frame.

  Note that the operation flow of the wireless coordinator according to the present embodiment shown in FIGS. 20 and 21 can be executed by a program on a computer. In other words, the wireless coordinator constituting the communication system and the CPU built in the control unit of the wireless device load the program stored in the memory, and each processing step of the program is sequentially executed.

  As described above, according to the present invention, in an asynchronous communication system, it is possible to cope with a failure in a specific wireless communication path, and at the same time, communication that can reduce power consumption. A system, a control method for a communication system, and a program can be obtained.

  As mentioned above, although embodiment of this invention has been described so far, embodiment of this invention is not limited to embodiment mentioned above. That is, other embodiments, additions, changes, deletions, and the like can be changed within the scope that can be conceived by those skilled in the art, and as long as the effects of the present invention are exhibited in any aspect, the scope of the present invention is included. It is included.

DESCRIPTION OF SYMBOLS 10 Communication system 11 Wireless coordinator 12, 13, 14, 15 Wireless device 21, 22, 23, 24 Relay device 31, 32, 33, 34, 35 End device 50 Wireless module 51 CPU
52 Memory 53 Radio Circuit 54 Antenna 55 External Interface 56 EEPROM
57 RAM
58 Flash memory 110 Data transmission unit 120 Data reception unit 121 Response transmission unit 122 Data analysis unit

JP 2010-041340 A

Claims (10)

A communication system including a plurality of communication terminals and a communication device that communicates with the plurality of communication terminals,
When communication between the communication device and the one communication terminal is interrupted, the communication device replaces any one of the plurality of communication terminals other than the one communication terminal with the communication device. A communication system that functions as an intermediary device that mediates communication with a communication terminal. The communication device simultaneously transmits control data including identification information for identifying each of the plurality of communication terminals and control information for causing each of the plurality of communication terminals to perform a predetermined operation to the plurality of communication terminals. Including control data transmission means for transmitting to
Each of the plurality of communication terminals includes control data receiving means for receiving the control data, and control data analysis means for determining whether or not to function as the mediating device based on the control data,
The communication system according to claim 1, wherein the control data includes information for identifying a communication terminal that functions as the mediation device.   The communication terminal functioning as the mediating device transmits the control data simultaneously to the one communication terminal and to the communication terminals excluding the one communication terminal from the plurality of communication terminals. 2. The communication system according to 2.   The plurality of communication terminals include a response transmission unit that transmits a response to the reception of the control data to the communication device, and the communication device includes the response among the plurality of communication terminals that transmitted the control data. Determining that a failure has occurred in the communication path between the communication terminal and the communication terminal that does not transmit the response, and simultaneously transmitting the control data to the communication terminal that does not transmit the response and the communication terminal that functions as the mediation device The communication system according to claim 2.   The communication terminal that functions as the mediation device transmits the control data to the communication terminal that does not transmit the response, and receives the response from the communication terminal that does not transmit the response, and transmits the response to the communication device. 5. The communication system according to claim 4, wherein the communication terminal that does not transmit a response indicating that the control data has been received.   The plurality of communication terminals include one or more relay devices and one or more termination devices each receiving control data retransmitted from the mediation device, and the communication devices are connected to the mediation device and the termination devices. The communication system according to claim 2, wherein the control data is transmitted simultaneously.   The intermediary device transmits a response indicating that the control data has been received to the communication device simultaneously, and simultaneously transmits the control data to the termination device. Communications system.   The one or more relay devices simultaneously transmit control data indicating that the control data has been received to the communication device within a predetermined time, and control data transmitted from all the one or more relay devices. 8. The communication system according to claim 6, wherein, when received, the communication device determines that the simultaneous transmission of the control data is successful. 9. A control method of a communication system including a plurality of communication terminals and a communication device that communicates with the plurality of communication terminals,
When communication between the communication device and the one communication terminal is interrupted, the communication device replaces any one of the plurality of communication terminals other than the one communication terminal with the communication device. A control method comprising a step of functioning as an intermediary device that mediates communication with one communication terminal. In a computer of a communication system including a plurality of communication terminals and a communication device that communicates with the plurality of communication terminals,
When communication between the communication device and the one communication terminal is interrupted, the communication device replaces any one of the plurality of communication terminals other than the one communication terminal with the communication device. A program for executing processing for functioning as an intermediary device that mediates communication with one communication terminal.

Images