JP2011029762A - Relay node device and sensor network system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relay node device which relays by radio between a plurality of end node devices that collect various information and a host that requires information collected by the end node device in a predetermined period of time. <P>SOLUTION: If the relay node device determines that a request for information from the host to the end node device is not communicable at a lower stream side of the relay node device, a signal coping with the non-communication is transmitted to the host at the upper stream side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates generally to a network optimization method, and more specifically to a technique for reducing unnecessary traffic in a wireless sensor network.

  There is a need to wirelessly collect data from client devices (also referred to as clients, slave units, and end nodes, for example, measurement devices) using a wireless sensor network. As an example, there is a measuring device network in which a plurality of clients are connected to a host device (also called a host, a parent device, or a base station node) via a wireless network. In the present specification, for simplicity, the client device is referred to as a “client” and the host device is referred to as a “host”.

JP 2006-254420 A JP 2006-500807 A

  According to the prior art, when communication with a client device (for example, a terminal node) cannot be performed (referred to as a non-communication state), communication is retried until a timeout time elapses. As a result, unnecessary traffic increases due to retries. In addition, since it is necessary to wait until the timeout time elapses, the time for finishing the communication becomes longer.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a system that shortens a standby time related to a non-communication node on a network.

  According to an embodiment of the present invention, a relay node device that wirelessly relays a plurality of terminal node devices that collect various types of information and a host that requests the information collected by the terminal node device over a predetermined period of time. When the relay node device determines that the request for the information from the host to the end node device is non-communication on the downstream side of the relay node device, the non-communication is supported on the upstream host. Send a signal to

  According to an embodiment of the present invention, a plurality of terminal node devices that collect various types of information, a host that requests the information collected by the terminal node device over a predetermined period, the terminal node device, and the host, A relay node device that relays wirelessly, the sensor node system determines that the request for the information from the host to the end node device is non-communication downstream of the relay node device. In this case, the relay node device transmits a signal corresponding to non-communication to the host on the upstream side.

  With the above configuration, the present invention has an effect that communication with the target measuring device can be performed as much as possible by shortening the standby time related to the non-communication node on the network.

1 is a schematic diagram of a sensor network system using an exemplary embodiment of the present invention. It is a timing chart which shows operation | movement of a host, a relay node, and a terminal node. It is a flowchart of the process which a relay node performs. FIG. 4 is a block diagram of a client used for an exemplary embodiment of the present invention. FIG. 4 is a block diagram of a host used for an exemplary embodiment of the invention.

  Exemplary embodiments of the invention are described in detail below with reference to the drawings. The same reference signs represent the same component or corresponding components in different embodiments.

(System overview)
FIG. 1 is a schematic diagram of a sensor network system 100 using an exemplary embodiment of the present invention. System 100 is an ad hoc wireless sensor network. This system 100 is configured such that a small wireless sensor terminal in the vicinity spontaneously constructs a network. The system 100 includes a host 110, a PC (personal computer) 120, and clients 130, 140, and 150. Although three clients are provided in this embodiment, the number of clients is not limited to this. Host 110 is also referred to as a base station node. Clients 130 and 140 are also called intermediate nodes. Client 150 is also referred to as a terminal node. In this specification, the host and the client are collectively referred to as a node.

  The end node 150 is wirelessly coupled to the host 110 via the intermediate nodes 130 and 140. For example, the host 110 is coupled to the intermediate node 130 by the wireless links 111 and 112. Intermediate node 130 is coupled to intermediate node 140 by wireless links 131 and 132. Intermediate node 140 is coupled to end node 150 by wireless links 141 and 142. In general, a link in a direction away from the center of the network (for example, a host), that is, a downlink 101 is collectively referred to as a downlink. Conversely, links in the direction approaching the center (for example, host) of the network, that is, the uplink 102 are collectively referred to as uplink. Therefore, the wireless links 111, 131, and 141 are downlinks, and the wireless links 112, 132, and 142 are uplinks. In this specification, a node located in the down direction 101 from a certain node is referred to as a downstream node, and conversely, a node located in the up direction 102 from a certain node is referred to as an upstream node.

  The end node 150a is wirelessly coupled to the host 110 via the intermediate nodes 130a and 140a. For example, the host 110 is coupled to the intermediate node 130a by the wireless links 111a and 112a. Intermediate node 130a is coupled to intermediate node 140a by radio links 131a and 132a. The intermediate node 140a is coupled to the end node 150a by wireless links 141a and 142a.

  The end node 150b is wirelessly coupled to the host 110 via the intermediate nodes 130b and 140b. For example, the host 110 is coupled to the intermediate node 130b by the wireless links 111b and 112b. The intermediate node 130b is coupled to the intermediate node 140b by wireless links 131b and 132b. Intermediate node 140b is coupled to end node 150b by radio links 141b and 142b.

  The end node 150c is wirelessly coupled to the host 110 via the intermediate nodes 130c and 140c. For example, the host 110 is coupled to the intermediate node 130c by the wireless links 111c and 112c. Intermediate node 130c is coupled to intermediate node 140c by radio links 131c and 132c. The intermediate node 140c is coupled to the end node 150c by the radio links 141c and 142c.

  The wireless links 111, 131, 141, 112, 132, and 142 may be, for example, a short-range wireless network that conforms to IEEE 802.15.4 using the 2.4 GHz band. This IEEE 802.15.4 is one of wireless communication standards called PAN (Personal Area Network) or WPAN (Wireless Personal Area Network), and has low cost, low power consumption, high reliability and security. The wireless links 111, 131, 141, 112, 132, 142 are not limited to the specific wireless networks described above, and can be any suitable network that can typically exchange information in the form of packets.

  According to an embodiment, each node has an automatic relay function, and can spontaneously configure a network by sensing a communication environment. The exemplary network is a true mesh and the number of hops is virtually unlimited. In other words, embodiments of the present invention can use multi-hop wireless networks.

(Terminal node, sensor)
The end node 150 may be coupled to the sensor 152, for example, by wire. Specifically, the end node 150 can be connected to the sensor 152 by RS485, RS422, RS232C, UART (Universal Asynchronous Receiver Transmitter), or the like. Similarly, the end nodes 150a, 150b, and 150c may be coupled to the sensors 152a, 152b, and 152c, respectively, by wire, for example.

  The sensors 152, 152a, 152b, 152c can be any suitable sensor. Such sensors include, but are not limited to, temperature sensors, humidity sensors, acceleration (impact) sensors, optical sensors, and the like. The sensor 152 outputs data (“sensor data”) representing mechanical, electromagnetic, thermal, acoustic, and chemical parameters (eg, temperature).

  The end nodes 150, 150a, 150b, and 150c generate wireless signals by encoding and modulating sensor data received from the sensors 152, 152a, 152b, and 152c, respectively. The end node 150 sends this radio signal to the host 110 via the radio links 142, 132, 112. Similarly, end node 150a sends wireless signals to host 110 via wireless links 142a, 132a, 112a. The end node 150b sends a radio signal to the host 110 via the radio links 142b, 132b, and 112b. The end node 150c sends a radio signal to the host 110 via the radio links 142c, 132c, and 112c. There are various schemes for encoding and modulating a radio signal. In a specific embodiment, a scheme conforming to the above-mentioned IEEE 802.15.4 is used.

  Host 110 obtains sensor data by demodulating and decoding radio signals received from end nodes 150, 150a, 150b, 150c. The host 110 sends the obtained sensor data to the PC 120. The PC 120 is coupled to the host 110 by, for example, a wired connection. Specifically, the PC 120 can be connected to the host 110 via a USB (Universal Serial Bus) or the like.

  The PC 120 can visually display or statistically process sensor data received from the sensor 152 using, for example, software including a GUI (graphical user interface). Such software can perform, for example, confirmation of communication status, numerical display of sensor data, graph display, distribution color mapping of sensor values, recording of sensor data, export of sensor data, change of terminal settings, and the like.

  The sensor network system 100 includes four terminal nodes 150, 150a, 150b, and 150c and four sensors 152, 152a, 152b, and 152c, and two intermediate nodes correspond to each terminal node. The number of end nodes and the number of sensors are not limited to four, and can be generally any number. The number of intermediate nodes is not limited to 2 and can be generally any number.

(Relay node operation)
FIG. 2 is a timing chart showing operations of the host 110, the relay nodes 130 and 140, and the end node 150. FIG. 3 is a flowchart of a process 300 executed by the relay node 140. With reference to FIGS. 2 and 3, the operation of the sensor network system 100 will be described below with a focus on the operation of the relay node 140. Similar data transfer is performed for the end nodes 150a, 150b, and 150c.

  At block 302, process 300 begins. In block 304, it is determined whether the packet is from an upstream node (eg, host 110 or relay node 130) to a downstream node (end node 150). If the determination at block 304 is no, the process returns after block 302.

  In a specific example, at time t0, the host 110 transmits an instruction 210 “send sensor data output from the end node 150 to the host 110” to the relay node 130. The relay node 130 transmits (transfers) the same command 212 as the command 210 to the relay node 140.

  The relay node 140 receives the packet 212 from the host 110 to the end node 150. At this time, the determination in block 304 is YES, so the process proceeds to block 306. Here, the relay node 140 transmits (transfers) the same command 214 as the command 212 to the relay node 150, and stores it in the memory for later retransmission (306).

  Here, it is assumed that the uplink 142 from the end node 150 to the relay node 140 is in a disconnected state. In block 308, the relay node 140 determines whether an acknowledgment (ACK, reception confirmation) has been received from the end node 150. If the determination at block 308 is YES, the uplink 142 from the end node 150 to the relay node 140 is normal and the process 300 ends (309).

  If the determination in block 308 is NO, the relay node 140 waits for the waiting period tw. In block 310, it is determined whether the period tw has elapsed. If the determination at block 310 is no, return to block 308. If the determination at block 310 is yes, proceed to block 312.

  At block 312, check the number of times relay node 140 has sent the packet to end node 150. If the determination in block 312 is NO, that is, if the number of transmissions has not been exceeded n (n is an integer greater than or equal to 2), the process returns to block 306.

  If the determination at block 312 is YES, i.e., if the number of transmissions has already exceeded n, the process proceeds to block 314 and is not communicating to the upstream node (in this case, to the host 110 which is the origin of the packet 212). Packets (also referred to as non-communication information) 240, 242 are sent, and the process 300 ends at block 316. The packet indicating that there is no communication may include the identifier of the relay node 140 itself and / or the end node 150 located downstream from the relay node 140. Such an identifier may be, for example, a node number represented by a plurality of bits in the packet.

  When the state where the uplink 142 is disconnected is continued, the relay node 140 transmits (214 to 221) the same packet n times (here, n = 8) by the blocks 306, 308, 310, and 312. In this example, it is assumed that the uplink 142 is disconnected. However, the present invention is not limited to this, and the system 100 may exhibit the above-described behavior even when the downlink 141 is disconnected.

(Waiting period tw and number of retries)
The waiting period tw is, for example, on the order of 10 ms. In the above example, since n = 8, in addition to 214 which is the original transmission, the number of retries 215 to 221 that have been retransmitted is 7 (n−1). At this time, the loss time from when the relay node 140 receives the packet 212 to when the packet 240 is transmitted is less than 100 ms. Conventionally, when an acknowledge does not come from the end node 150, the system waits for the order of several seconds. That is, the timeout period was on the order of a few seconds. On the other hand, in this embodiment, non-communication information can be sent to the host 110 after waiting for an order of 0.1 seconds at the maximum. As a result, the host 110 can know that there is no communication between the relay node 140 and the end node 150 with a minimum loss time.

  The standby time tw and the number of retries (n−1) are not limited to the above example, and may be any appropriate value. In another embodiment, the waiting time tw may be changed according to the number of retries. For example, the transmission 214 to 217 (retry 1st to 3rd) is set to tw = 10 ms, and the transmission 218 to 221 (retry 4th to 8th) is set to tw = 20 ms. If the number of times increases, a longer waiting time may be secured.

(Use of non-communication information by the host)
When the non-communication information is received from the relay node 140, the host 110 can consider the information when collecting sensor data from the sensor thereafter. In other words, the host 110 considers information regarding non-communication regarding each node, conversely information regarding the goodness of communication indicating that communication can be reliably performed, and the like. Whether to send a request or the like).

  For example, the host 110 may have a map in its memory that represents the communication state of each node. Such a map may describe the communication state of each radio link, for example in the form of a matrix. If the communication status map indicates that the wireless link 141 or 142 to the node 150 is not communicating, the host 110 stops communication to the node 150 that is not communicating (for example, a request to collect sensor data). To do.

  In one embodiment, the host 110 has a list of nodes (herein referred to as a “transmission list”) in which sensor data is to be collected. The transmission list specifies that sensor data is collected in the order of nodes 150, 150a, 150b, and 150c, for example. As described above, when the node 150 is in a non-communication state, the transmission list is modified to specify that sensor data is collected in the order of the nodes 150a, 150b, and 150c without performing communication with the node 150. obtain. Based on the transmission list, the host 110 sends a request to the nodes 150a, 150b, and 150c next to the communication to the node 150 that has failed to communicate. When the host 110 sends a request to the node 150c, next, the request is sent to the node 150a. That is, when a node that is not communicating (here 150) is detected, the information is stored in the transmission list. As a result, the host 110 can not communicate with the non-communication node after detecting the non-communication node.

  As described above, the host 110 can reduce the waiting time for a node that does not respond by using the non-communication information regarding the non-communication node. As a result, the communication frequency for the communicable node can be increased. As a result, even if a non-communication node occurs, the overall communication efficiency does not decrease. As a result, traffic for retrying a request for a non-communication node can be reduced.

  In the above example, it is assumed that the single end node 150 is not communicating, but the present invention is not limited to this, and a plurality of end nodes may be not communicating. For example, when the end nodes 150 and 150b are not communicating, the transmission list specifies that communication is performed only for the two end nodes in the order of 150a and 150c. Thus, it is only necessary to communicate with the two nodes 150a and 150c that can communicate with each other. Compared to communication with four nodes, it is theoretically possible to perform communication with two nodes twice as often. In this way, the communication frequency can be increased for nodes that can communicate.

  The nodes that can be in a non-communication state are not limited to the end nodes 150, 150a, 150b, and 150c, and may be any intermediate node. For example, when there is no communication between the relay node 130 and the relay node 140, a retry or the like is appropriately performed on the relay node 140 as described above. Thereafter, the non-communication information is sent to the host 110, whereby the end node 150 is deleted from the transmission list, and the host 110 performs communication only with the end nodes 150a, 150b, and 150c.

  Also, for example, when the intermediate node 140c is not communicating (the wireless link 131c or 132c is not communicating), after retrying the relay node 140c, the non-communication information is transmitted to the host 110. As a result, the end node 150c is deleted from the transmission list, and the host 110 communicates only with the end nodes 150, 150a, and 150b.

(Client hardware)
FIG. 4 is a block diagram of an end node 150 used for an exemplary embodiment of the present invention.

  End node 150 is coupled to sensor 150. The end node 150 includes an RF unit 410 and an antenna 430. The sensor 152 outputs sensor data to the RF unit 410. The RF unit 410 converts the sensor data output from the sensor 152 into a radio signal, and sends it to the upstream node (host 110 or the like) from the antenna 430, for example. The sensor 152 may be a measuring device.

  The RF unit 410 includes a sensor interface 440, a DC (direct current) power supply 445, an MCU (micro controller unit) 450, a ROM (read only memory) 452, a RAM (random access memory) 454, a timer 456, a wireless transmission / reception unit 458, and an RF. An interface 460 is included. The sensor interface 440 converts the sensor signal output by the sensor 135 into an appropriate signal (for example, a 10-bit digital signal) that can be processed by the MCU 450. The DC power source 445 supplies a DC power source to each functional block of the RF unit 134. The DC power source 445 can be, for example, a lithium battery that supplies a direct current of 3V.

  The MCU 450 is a microprocessor used to realize the functions of the end node 132. The MCU 450 stores a program and data necessary for realizing the function of the end node 132 in the ROM 452 or the RAM 454. The timer 456 measures the timing of turning off the power, for example, and triggers the MCU 450 to cut off the power supply from the DC power supply 445 when a predetermined time has elapsed. MCU 450 may include peripheral elements such as ROM 452, RAM 454, and timer 456 therein. In this case, the cost for constructing the system can be reduced as compared with the case where a ROM or the like is mounted as an independent component.

  The wireless transmission / reception unit 458 converts data from the MCU 450 into a response packet to be sent to the host 110 or converts a request packet received from the host into data. The RF interface 460 converts the packet output from the wireless transmission / reception unit 458 into an RF signal and outputs the RF signal to the antenna, reproduces the packet from the RF signal received by the antenna, and outputs the packet to the wireless transmission / reception unit 458.

  The relay nodes 130 and 140 also have the same configuration as the end node 150 shown in FIG. 4 except that the sensors are not coupled. Alternatively, the relay nodes 130 and 140 may have the same configuration as the end node 150 to which the sensor is coupled as shown in FIG.

(Host hardware)
FIG. 5 is a block diagram of a host 110 used for an exemplary embodiment of the invention. The host 110 includes an RF unit 510 and an antenna 530. In general, the host 110 may communicate with any of a plurality of clients. The following description herein assumes that the host 110 communicates with the end node 150 via any intermediate node 130,140.

  The RF unit 510 converts the request for the end node 150 into a radio signal and sends it from the antenna 530 to the end node 150. The RF unit 510 converts the response from the end node 150 received by the antenna 530 into data and sends the data from the RF unit 510 to the PC 120 via the interface 540.

  The RF unit 510 includes an interface 540, a power supply 545, an MCU 550, a ROM 552, a RAM 554, a timer 556, a wireless transmission / reception unit 558, and an RF interface 560. The interface 540 converts various signals output by the PC 120 into appropriate signals (for example, 8-bit digital signals) that can be processed by the MCU 550. The power source 545 supplies DC power to each functional block of the host 110. The power source 545 receives, for example, 100V AC supplied from a household AC (AC) power outlet, converts it to DC 3V, and supplies DC voltage to each block.

  The MCU 550 is a microprocessor that is used to realize the functions of the host 110. The MCU 550 stores programs and data necessary for realizing the functions of the host 110 in the ROM 552 or the RAM 554. The timer 556 measures a timeout time 230, for example, and triggers the MCU 550 to transmit a request cancellation when a predetermined time has elapsed. MCU 550 may include peripheral elements such as ROM 552, RAM 554, and timer 556 therein. In this case, the cost for constructing the system can be reduced as compared with the case where a ROM or the like is mounted as an independent component.

  The wireless transmission / reception unit 558 converts data from the MCU 550 into a request packet or a request cancellation packet to be sent to the client, or converts a response packet received from the client into data. The RF interface 560 converts the packet output from the wireless transmission / reception unit 558 into an RF signal and outputs the RF signal to the antenna, reproduces the packet from the RF signal received by the antenna, and outputs the packet to the wireless transmission / reception unit 558.

  The embodiments of the present invention have been described in detail above.

  Hosts and clients according to embodiments of the present invention can typically be realized by a group of circuit elements including semiconductor elements mounted on a substrate. Typically, the host 110, the intermediate nodes 130 and 140, and the end node 150 are a combination of an analog circuit that handles an analog signal from a sensor and a high-frequency signal for a wireless network, and a digital circuit whose main element is an MCU. Can be realized.

  The control of the host device according to the present invention can typically be realized by software. That is, the procedure (or operation) shown in FIGS. 2 and 3 can be typically implemented by software stored on a computer readable medium. Examples of the computer readable medium include a hard disk drive and a semiconductor memory. Alternatively, procedures according to embodiments of the present invention may be implemented by a combination of software and hardware, or only by hardware. Control of client devices according to embodiments of the present invention may also typically be implemented by software.

  A part or all of the functional block groups shown in FIGS. 4 and 5 may be integrated and realized by being appropriately combined. For example, the RF unit 410 may be realized as a hybrid IC (integrated circuit). Further, for example, the end node 150 may be realized by integrating the RF unit 410, the sensor 152, and the antenna 430 on one substrate.

  The present invention is not limited to the embodiments, and can be implemented in various other forms without departing from the spirit or main features thereof.

  As described above, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is defined by the claims, and is not limited by the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  As described above, the present invention is particularly useful for sensor networks that use radio.

200 Procedure 110 Host 130, 140 Relay node 150 End node 210, 212, 214-221, 240, 242 Packet

Claims (7)

A relay node device that wirelessly relays a plurality of terminal node devices that collect various types of information and a host that requests the information collected by the terminal node device over a predetermined period,
When the relay node device determines that the request for the information from the host to the terminal node device is non-communication on the downstream side of the relay node device, it corresponds to non-communication to the host on the upstream side. A relay node device that transmits a signal.   The request is transmitted to a downstream relay node device a predetermined number of times, and if no reception confirmation is received from the downstream relay node device, it is determined that there is no communication. The relay node device described.   3. The relay node device according to claim 1, wherein the signal corresponding to non-communication includes an identifier of the terminal node device on its own and / or on the downstream side. 4. A plurality of terminal node devices that collect various types of information; a host that requests the information collected by the terminal node device over a predetermined period; and a relay node device that relays the terminal node device and the host wirelessly. A sensor network system comprising:
When the relay node device determines that the request for the information from the host to the terminal node device is non-communication on the downstream side of the relay node device,
The relay node device transmits a signal corresponding to non-communication to the host on the upstream side thereof.   The host that has received the signal corresponding to non-communication stops the request for the end node device that has requested the information, and requests the information from the end node device in the next order. 5. The sensor network system according to 4.   The request is transmitted a predetermined number of times to a downstream relay node device, and it is determined that there is no communication when no reception confirmation for the request is received from the downstream relay node device. 6. The sensor network system according to any one of 5 or 5.   The sensor network system according to any one of claims 4 to 6, wherein the signal corresponding to non-communication includes an identifier of the terminal node device on its own and / or on the downstream side.

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