JP2008204136A - Sensor network system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for surely transmitting a crime-prevention signal to a base even when a node whose battery is running out or fails exists on a sensor network system. <P>SOLUTION: A lower node time-serially transmits a signal detected by a crime prevention sensor based on an adjacent node list to higher M nodes at most. The M nodes 1 transmit crime prevention signals to the higher M nodes of an adjacent node list of its own. This operation is repeated so that the same crime-prevention signal can be transmitted via a plurality of nodes 1 to a base 2 by a plurality of routes. The data system transmitted include the address and data ID of the node 1 as the transmission destination. This procedure is repeated by each node 1 so that the crime prevention signal can be finally transmitted to the base 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a node that transmits sensor data, a base that receives sensor data from the node, and a sensor network system that includes the node and the base.

In recent years, a sensor network system has been studied in which a small electronic circuit having a wireless communication function is added to a sensor and various information in the real world is taken into an information processing device in real time. The sensor network system is considered to have a wide range of applications. For example, a ring-type small electronic circuit that integrates a wireless circuit, processor, sensor, and battery is used to constantly monitor the pulse, etc. A medical application is also considered in which a health condition is determined based on a monitor result transmitted (see, for example, Non-Patent Document 1).

To put the sensor network system into widespread practical use, wireless communication functions, sensors, and electronic circuits equipped with power supplies such as batteries (hereinafter referred to as nodes) are maintenance-free and transmit sensor data for a long time. It is important to continue to do this and to reduce the size of the outer shape. For this reason, development of ultra-compact nodes that can be installed anywhere is underway. At the present stage, it is considered necessary from the standpoint of maintenance cost and usability to be usable without replacing the battery for a period of about one year.
For example, Non-Patent Document 2 introduces a prototype of a small node having a diameter of about 3 cm called “Mica2Dot”. The Mica2Dot includes an RF chip that integrates functions necessary for wireless communication and a processor chip with low power consumption. In this prototype, 99% of the time is in a standby state, and only the remaining 1% of time is intermittently activated and the sensor is moved to perform wireless communication of the results. Operation is possible.
There are two types of sensor network systems: a small node that performs wireless communication as described above, and a device that collects sensed data wirelessly and connects to a wired network such as the Internet (hereinafter referred to as a base). I need a device. The node is often driven by a battery in consideration of its small size and mobility, whereas the base is often stationary and driven by an AC power source.
Sokwoo Rhee et al. `` Artifact-Resistant Power-Efficient Design of Finger-Ring Plethysmographic Sensors '', IEEE Transactions On Biomedical Engineering, Vol.48, No.7, July 2001, pp.795-805 Crossbow “Smarter Sensors In Silicon”, Internet, URL: http://www.xbow.com/Support/Support_pdf_files/Motetraining/Hardware.pdf

When the sensor network system is used for a crime prevention system in a facility such as a building, the following problems occur. As described above, the node is strongly required to be driven by a battery because of the ease of installation. However, battery life is limited in its life.
When the security sensor is activated and a signal is transmitted from the node, this signal is transmitted to the base via another node. However, if the battery of the node in the middle is exhausted, the node does not have a signal transmission function. Therefore, the signal stops. This prevents the security system from functioning. That is, there is a problem that reliability is inferior when applied to crime prevention in a system using a battery that may be consumed at any time.

  According to a first aspect of the present invention for solving the above-mentioned problems, the sensor comprises a node that transmits a sensor sensing signal and a base that receives the sensor sensing signal from the node, and uses a wireless network system to provide the sensor. In the sensor network system for transmitting the sensing signal to the server, the node that has received the sensing signal has a higher base closer to the base than the node described in the adjacent node list that is information of the node to which the signal is transmitted. The sensor network system transmits a data frame including the sensing signal in time series in order.

  According to a second aspect of the present invention, in the sensor network system according to the first aspect, the data frame includes a transmission destination address and a data ID.

  A third aspect of the present invention is characterized in that a data frame including the sensing signal is transmitted in time series in order from the top to the top M of the neighboring nodes described in the neighboring node list. In the sensor network system according to the first aspect.

  According to a fourth aspect of the present invention, adjacent nodes described in the adjacent node list are described in the list as nodes having higher reception sensitivity values (RSSI) from the nodes that communicate with each other in advance. The sensor network system according to the first aspect is characterized in that.

  A fifth aspect of the present invention includes a node that transmits a sensor sensing signal and a base that receives the sensor sensing signal from the node, and uses a wireless network system to store the sensor sensing signal as a server. In the sensor network system that communicates to the node, the node that has received the sensing signal is time-sequentially in order from the top closer to the base with respect to the node described in the adjacent node list that is the information of the node to which the signal is transmitted. In addition, the sensor network system transmits a data frame including the sensing signal without an ACK signal notifying the transmission source of the reception.

  According to the present invention, there is an effect that it is possible to construct a system in which a crime prevention signal is reliably transmitted to the base even when a node that has run out of battery or has failed is present on the sensor network system.

  An outline of a typical embodiment of the present invention is as follows. Each node transmits information (hereinafter referred to as an adjacent node list) to which node a signal is transmitted among nodes (hereinafter referred to as upper nodes) that are closer to the base than themselves (hereinafter referred to as lower nodes). I already have it. This information is specifically the address of the upper node, and this information can be obtained by each node when the sensor network system is constructed in advance. Each node that has received a signal (hereinafter referred to as a security signal) detected by a security sensor based on this information is time-sequentially signaled to, for example, up to M upper nodes in its adjacent node list. Send. The M nodes further transmit a security signal to the upper M upper nodes in the adjacent node list owned by the M nodes. By repeating this, the same crime prevention signal is transmitted to the base via a plurality of routes via a number of nodes. Thereby, even if a plurality of nodes on the sensor network system are not operating due to running out of batteries, the probability that the security signal is transmitted to the base is increased.

  The structure of the data frame transmitted at this time is shown in FIG. The data frame 40 includes a source address Src41, a destination address Dest42, a base address BaseID43, and a signal (hereinafter referred to as data) that can uniquely distinguish a detection signal detected by a security sensor from a detection signal of a similar security sensor detected by another node. Data ID 44, detection signal Data 45 of the security sensor, and CRC 46 for parity check. Here, each data is composed of 8 bits. The host node receiving the signal can identify whether the signal has already been received in the past by referring to the data ID. That is, if the content of this data ID is the same as the past data ID (stored in the CPU and updated to a new ID each time it is received), it can be understood that the data has already been received from a different node. If the signal has been received in the past, this upper node does not transmit the signal again. This process prevents the same signal from being transmitted repeatedly from the same node. By repeating this procedure for each node, a security signal is finally transmitted to the base.

  FIG. 1 shows an embodiment of a sensor network system, which will be described in detail. It comprises a node 1 from N1 to N10 on which sensors are mounted, and a base 2 connected to the server 3 by a LAN cable. Bidirectional wireless connection is established between each node 1 and between node 1 and base 2. The arrows mean that they can communicate with each other in both directions. Here, the radio means a radio represented by a communication method such as weak, specific power saving, ZigBee, or Bluetooth.

  The hardware configuration of the base 2 is shown in FIG. The radio unit 20 includes an antenna (ANT) 21, a radio module (RFM) 22, a microcomputer (CPU) 23, a control circuit (LOGIC) 24, a voltage regulator (REG) 25, and a real time clock (RTC) 26. In addition, a LAN board 28 on which a TCP / IP conversion IC 27 is mounted is mounted so that communication with the server 3 can be performed. The LAN board 28 performs wired communication between the server 3 and the base 2. The LAN board 28 and the wireless unit 20 are connected by connectors CN2 and CN4.

  On the other hand, the configuration of the node 1 is shown in FIG. The radio unit 30 includes an antenna (ANT) 31, a radio module (RFM) 32, a microcomputer (CPU) 33, a control circuit (LOGIC) 34, and a real time clock (RTC) 36, and is driven by a built-in battery 35. The node 1 from N1 to N10 includes a sensor 39 that can detect a human motion such as a human sensor and a wireless unit 30 that can wirelessly transmit the detected signal.

  For example, when a human sensor mounted on the node N8 senses a human motion, the detected signal is transmitted to the upper node by the wireless module mounted on the node N8. The transmission destination of this signal is a node described in the adjacent node list stored in the memory in the CPU mounted on the wireless unit, and is sequentially transmitted to the node positioned higher. . The order described in the adjacent node list is the order in which each node communicates in advance and the radio wave transmitted from the node N8 can be received most strongly. That is, the order of reception sensitivity value (RSSI) is high. In the absence of disturbance, this reception sensitivity value is inversely proportional to the square of the distance between the nodes, and therefore, it is described from the upper node having a short distance between the nodes. For example, in the case of the node N8, there are three higher-order nodes N4, N9 and N10 that are close to the base in terms of distance. In the case of the node N10, if the radio wave does not reach because the distance to the node N8 is longer than the other nodes, only the nodes N4 and N9 are described in the adjacent node list. Therefore, signals can be transmitted wirelessly to the nodes N4 and N9. In the node N10, a signal can be sent to the adjacent nodes N5, N6, and N9.

  The partner node to which each node can send its own data wirelessly is determined by the distance between itself and the partner node. Specifically, the distance differs depending on the radio system. For example, it is possible to send its own signal to the partner node even if the distance is about 3 to 5 m when the transmission output is low, such as weak wireless, and about 100 m when the transmission output is high such as specific small power. It is. Therefore, since the distance between nodes can be increased in the wireless system having a high transmission output, a wide range of sensor network systems can be constructed.

  A transmission flowchart of the present invention is shown in FIG. First, a human sensor at a certain node detects a person (S50). The top M nodes in the adjacent node list possessed by the detected node are prepared for transmission such as the order of nodes to be transmitted (S51). Next, a data frame without an ACK signal is transmitted to the corresponding node according to the order (S52). Further, it is determined whether or not a data frame without an ACK signal has been transmitted to M nodes (S53), and if not completed, the process returns to S52. When the transmission is completed in S53, it is determined whether the transmission has reached the base (S54). When the base is reached, this transmission flow is terminated. If the base has not been reached in S54, the received node further determines whether the data IDs match (S55). If the data IDs match, the data has already been received, so this transmission flow ends. If the data IDs do not match in S55, the data is not received, so transmission to the upper M nodes of the adjacent node list held by the received node such as the order of the nodes to be transmitted. Preparation is made (S56). Next, the process returns to S52.

  For example, it is assumed that the human sensor at the node N4 detects a human intrusion and the output state of the human sensor has changed. The signal change is transmitted to the radio unit mounted on the node N4. The wireless unit to which the signal change is transmitted transmits the signal change to the top M number of upper nodes described in the list based on the adjacent node list that the wireless unit has. At this time, the upper nodes listed in the adjacent node list are listed in the list from the node having the highest reception sensitivity value (RSSI) as a result of each node communicating beforehand, and the reception sensitivity value is below a certain level. The node is removed from the list because it is difficult to receive. Therefore, the number of nodes described in the adjacent node list varies depending on the node. In an environment with many disturbances, the reception capability is low, so the number of nodes listed in the adjacent node list that has a reception sensitivity value above a certain level is small. The number of nodes increases. Therefore, since there are many disturbances, when there is only one node described in the adjacent node list having a reception sensitivity value (RSSI) above a certain level, the above-mentioned top M nodes are M = 1. .

  On the other hand, when the disturbance is small, the number of nodes described in the adjacent node list is large. If it is assumed that there are 10 nodes, M = 10. However, for example, the upper three nodes in the adjacent node list are sufficient as the upper node of the transmission destination. This is because a large number of nodes being described means that the radio wave environment is good, and it can be determined that the accuracy of communication is high. Therefore, in this case, M = 3. Since the value of M differs depending on the environment to which the sensor network system according to the present invention is applied, it is determined on the spot according to the environmental situation.

Here, it is assumed that the list of the node N4 is written in the order of the node N1, the node N5, and the node N9. Therefore, the node N4 provides the node N1 with its own ID as the source address, the ID of the node N1 as the destination address, the base ID as the final destination address, the signal change information and the data ID of the human sensor, It is transmitted as a series of data (hereinafter referred to as a data frame). At this time, the node N5 naturally receives the signal from the node N4, but the node N5 discards this data because the node N1 is included in the data as the transmission destination address. Node N9 performs the same processing as node N5.
In addition, the node N1 that has received the signal from the node N4 transmits a signal (hereinafter referred to as an ACK signal) that is normally received to the node N4, but does not transmit an ACK signal in the present invention.

  When the signal transmission to the node N1 is completed, the node N4 transmits a signal similar to the data transmitted to the node N1 to the second highest node N5 in the adjacent list. However, the ID of the node N5 is used instead of the node N1 as the transmission destination address. This signal is also received by the nodes N1 and N9 as described above, but the received data is discarded because the destination address is not its own node.

  The node N5 that has received the signal from the node N4 transmits an ACK signal that is originally received to the node N4, but does not transmit an ACK signal in the present invention.

  When the signal transmission to the node N5 is completed, the node N4 transmits a signal similar to the data transmitted to the node N1 to the third highest node N9 in the adjacent list. However, the ID of the node N9 is used as the transmission destination address instead of the node N1. This signal is also received by the nodes N1 and N5 as described above, but the received data is discarded because the destination address is not its own node.

The node N9 that has received the signal from the node N4 transmits an ACK signal that is originally received to the node N4, but does not transmit an ACK signal in the present invention.
As described above, the signal detected by the human sensor of the node N4 is transmitted in time series in the order of the upper nodes described in the adjacent node list. At this time, the upper node receiving the data does not transmit an ACK signal.

  Further, the node N5 repeats the operation performed by the node N4 for the top three nodes in the adjacent node list described therein, for example, the node N1, the node N2, and the node N3. However, since the same data has already been transmitted from the node N4, the node N1 discards the received data. In this operation, the received data frame includes the data ID, and the data ID is the same, and is discarded. For the nodes N2 and N3, the operation similar to that performed by the node N4 for the nodes N5 and N9 is performed.

  Furthermore, the node described in the adjacent node list of the node N1, the node N2, and the node N3 is only the base. Therefore, the nodes N1, N2, and N3 transmit detection signals of the human sensor of the node N4 toward the base. As a result, the detection signal of the human sensor at the node N4 is sent to the base through three types of routes: node N1 → base, node N5 → node N2 → base, and node N5 → node N3 → base. As a result, a plurality of routes are secured as described above even if any one of the nodes is out of order or out of battery, so the probability that a signal is sent to the base is increased. Here, if the nodes N1, N2, and N3 transmit toward the base at the same time, radio wave collision occurs, and the base cannot receive signals from any of the nodes.

  However, in the present invention, signals are transmitted in time series from the upper node to the upper node described in the adjacent node list. Thereby, for example, the signal sent from the node N4 to the node N1 precedes the signal sent via the node N5 → the node N2. Further, the signal sent from the node N5 to the node N2 is temporally ahead of the signal sent from the node N5 to the node N3. As a result, the signal of the node N4 transmitted through the three types of routes has a time difference until it reaches the base, and therefore no signal collision occurs.

As described above, the receiving node does not transmit an ACK signal indicating that it has been received. This is because when an ACK signal is transmitted, it takes much time to transmit the detection signal of the node N4 to the base. Since this is a fatal defect for the system installed for the purpose of crime prevention, in the present invention, the system is configured without transmitting an ACK signal. The drawback due to this is that confirmation of whether or not the signal is reliably transmitted has not been made, but this system compensates for this drawback by securing a plurality of signal paths.
The detection signal sent to the base is sent to the server through the LAN, and the intruder signal can be confirmed at the center.

It is a figure which shows one Embodiment of a sensor network system. It is a figure which shows the hardware constitutions of a base. It is a figure which shows the hardware constitutions of a node. It is a figure which shows the structure of a data frame. It is a figure which shows a transmission flowchart.

Explanation of symbols

1 node
2 base
3 servers
39 Sensor

Claims (5)

A node that transmits a sensor sensing signal;
A base for receiving a sensor sensing signal from the node;
In a sensor network system that transmits a sensing signal of the sensor to a server using a wireless network system,
The node that has received the sensing signal includes the sensing signal in chronological order from the upper level closer to the base relative to the node described in the adjacent node list that is information of the node to which the signal is transmitted. A sensor network system that transmits data frames.   The sensor network system according to claim 1, wherein the data frame includes a transmission destination address and a data ID.   2. The sensor network according to claim 1, wherein a data frame including the sensing signal is transmitted in time series in order from the top to the top M nodes among the neighboring nodes described in the neighboring node list. system.   The adjacent node described in the adjacent node list is described in the list as an upper node from a node having a high reception sensitivity value (RSSI) by communicating with each node in advance. The described sensor network system. A node that transmits a sensor sensing signal;
A base for receiving a sensor sensing signal from the node;
In a sensor network system that transmits a sensing signal of the sensor to a server using a wireless network system,
The node that has received the sensing signal indicates that it has received the information in the time series in order from the higher level closer to the base with respect to the node described in the adjacent node list that is information of the node to which the signal is transmitted. A sensor network system for transmitting a data frame including the sensing signal without an ACK signal for informing the user.

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