Sensor-net system and sensor node

• US 20080307075A1
• Filed: 02/11/2008
• Published: 12/11/2008
• Est. Priority Date: 06/07/2007
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Odaka, Toshiyuki, Muro, Keiro, Wakisaka, Yoshihiro, Ogushi, Minoru, Urano, Takehiro
• Granted Patent: US 8,438,249 B2
• Time in Patent Office: Days
• US Class Current: 709/220
• CPC Class Codes: G06F 1/14 Time supervision arrangements, e.g. real time clock
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04W 74/06 using polling
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: H04W 88/16 Gateway arrangements

Abstract

A sensor-Net system includes sensor nodes which are in intermittent operation so as to save power by repeating activated state and inactivated state at a regular interval. Synchronization of time in the system is executed by aligning to the intermittent operation of the sensor nodes. A management server issues a setTime command for configuring the time to each gateway node at a specified interval. Each router node sets or corrects the time of it based on the time received from the gateway node and thereafter turns ON the time configuration flag for each sensor node in order to expand the setTime command to all of its sibling sensor nodes. The router node, upon reception of a polling, which is a command request, from the sensor node, obtains the time at that time, then uses the time to generate a setTime command to transmit to that sensor node.

Claims

1. A sensor-Net system, comprising a base station gateway node, a router node connected to the base station gateway node in a wireless communication, and a sensor node connected to the base station gateway node and to the router node in a wireless communication, the base station gateway node and the router node being in operation all the time, the sensor node being in intermittent operation,

wherein the router node transmits, when setting the clocks of the gateway node, the router node, and the sensor node, at the timing of being requested with a command transmission from the sensor node, the time setting command based on the latest time of the router node to the sensor node requesting the command transmission;

and

the sensor node, upon reception of the latest time from the router node, sets the time based on the latest time of the router node.

2. A sensor-Net system according to claim 1,

wherein the gateway node has a plurality of the router nodes and the sensor nodes as siblings, and has a management table for managing the sibling router nodes and the sibling sensor nodes;

and

the gateway node, upon reception of a time setting command from a management server connected through a network, refers to the management table to expand immediately the time setting command to the sibling router nodes to synchronize the time in the router nodes.

3. A sensor-Net system according to claim 1,

wherein the router node has a storage unit for storing a time configuration flag each corresponding to all of the sibling sensor nodes;

the router node, receiving a time setting command from the gateway node, at the timing of setting the latest time of the router node, turns on the time configuration flags held in the storage unit;

the router node, upon reception of the command transmission request from the sensor node, checks to see the ON or OFF status of the time configuration flag, and transmits, only when the time configuration flag is ON, the time setting command based on the latest time of the router node to the sensor node having transmitted the command transmission request;

the router node turns off the time configuration flag held in the storage unit at the timing of receiving the reply to the time setting command.

4. A sensor-Net system according to claim 2,

wherein the router node has a storage unit for holding a time configuration flag each corresponding to all of the sibling sensor nodes;

the router node, receiving the time setting command from the gateway node, turns on the time configuration flag held in the storage unit, at the timing of setting the latest time of the router node;

the router node, when receiving the command transmission request from the sensor node, checks to see the ON or OFF status of the time configuration flag, and transmits, only when the time configuration flag is ON, the time setting command based on the latest time of the router node to the sensor node having sent the command transmission request.

the router node turns off the time configuration flag held in the storage unit at the timing of receiving the reply to the time setting command.

5. A sensor-Net system according to claim 3,

wherein the sensor node, based on the latest time of the sensor node set based on the time setting command from the router node, adds the time to the observation value held, then transmits the observation value to the router node.

6. A sensor-Net system according to claim 4,

wherein the sensor node, based on the latest time of the sensor node set based on the time setting command from the router node, adds the time to the observation value held, then transmits the observation value to the router node.

7. A sensor-Net system according to claim 5,

wherein the sensor node, after having sent the observation value to the router node, stores the observation value having the time added into the storage unit of the sensor node, then enters into sleep mode of the intermittent operation.

8. A sensor-Net system according to claim 6,

wherein the sensor node, after having sent the observation value to the router node, stores the observation value having the time added into the storage unit of the sensor node, then enters into sleep mode of the intermittent operation.

9. A sensor-Net system according to claim 5, further comprising:

a management server connected to the gateway node through a network, including a communication unit for connecting to the network, a processing unit, and a storage unit;

wherein the management server receives the observation value received by the router node through the gateway node for storing in an observation value storage unit in the storage unit.

10. A sensor-Net system according to claim 6,

wherein the management server is made up a communication unit for connecting to the network, a processing unit, and a storage unit;

the management server receives the observation value received by the router node through the gateway node for storing in an observation value storage unit in the storage unit.

11. A sensor-Net system according to claim 9,

wherein the processing unit of the management server calculates the influence between a first wearer wearing the first sensor node and a second wearer wearing the second sensor node based on the observation value transmitted by the first sensor node and the observation value transmitted by the second sensor node, both stored in the observation value storage unit.

12. A sensor-Net system according to claim 10,

wherein the processing unit of the management server calculates the influence between a first wearer wearing the first sensor node and a second wearer wearing the second sensor node based on the observation value transmitted by the first sensor node and the observation value transmitted by the second sensor node, both stored in the observation value storage unit.

13. A sensor-Net system according to claim 11,

wherein the first and second sensor nodes have an acceleration sensor, respectively;

the first and second sensor nodes transmit the output data of the acceleration sensor as the observation value;

the processing unit of the management server determines the correlation of action between the first and second wearers based on the output data of the acceleration sensor in order to calculate the influence.

14. A sensor-Net system according to claim 12,

wherein the first and second sensor nodes have an acceleration sensor, respectively;

the first and second sensor nodes transmit the output data of the acceleration sensor as the observation value;

the processing unit of the management server determines the correlation of action between the first and second wearers based on the output data of the acceleration sensor in order to calculate the influence.

15. A sensor-Net system, comprising a gateway node, and a sensor node connected to the gateway node through a wireless communication, the gateway node being in operation all the time, the sensor node being in intermittent operation,

wherein the sensor node issues a time request command on a regular basis or at the timing of connecting to the gateway node, and invokes its internal timer at the time when receiving a reply to the time request command from the gateway node;

the gateway node obtains a reference time at the time when receiving the time request command from the sensor node, and transmits the reference time to the sensor node at the time when receiving a next command transmission request from the sensor node;

the sensor node stops the timer at the time when receiving the reference time, calculates the active time of the timer from the difference between the timer stopping time and the timer activated time, and then performs the time configuration by adding the reference time received from the gateway node to the timer activated time.

16. A sensor-Net system according to claim 15,

wherein the sensor node performs the time setting, and thereafter transmits the observation values stored in the sensor node to the gateway node.

17. A sensor-Net system according to claim 16, further comprising:

a management server connected to the gateway node through a network, including a communication unit for connecting to the network, a processing unit, and a storage unit;

wherein the management server receives the observation value received by the gateway node from the gateway node in order to store in the observation value storage unit in the storage unit.

18. A sensor-Net system according to claim 17,

wherein the processing unit of the management server calculates the influence between a first wearer wearing the first sensor node and a second wearer wearing the second sensor node based on the observation value transmitted by the first sensor node and the observation value transmitted by the second sensor node, both stored in the observation value storage unit.

19. A sensor node connected through a wireless communication to a gateway node being in operation all the time, for intermittently operating, comprising:

a processing unit, a storage unit, an RF transceiver unit, and a real time clock,

wherein the processing unit issues a time request command on a regular basis or at the timing of connecting to the gateway node, and invokes its internal timer at the time when receiving a reply to the time request command from the gateway node;

the processing unit, after issuing the time request command, when transmitting a next command transmission request to the gateway node, receives a reference time obtained by the gateway node at the time when receiving the time request command from the sensor node;

the sensor node stops the timer at the time when receiving the reference time, calculates the active time of the timer from the difference between the timer stopping time and the timer activated time, and then sets the time of the real time clock by adding the reference time received from the gateway node to the timer activated time.

20. A sensor node according to claim 19,

wherein the processing unit is a microprocessor incorporating a timer which is operable in a low power consumption mode;

and

the timer incorporated in the microprocessor is used as the timer to calculate the activated time.