Sensor-Net system and sensor node

• US 8,438,249 B2
• Filed: 02/11/2008
• Issued: 05/07/2013
• Est. Priority Date: 06/07/2007
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Urano, Takehiro, Muro, Keiro, Odaka, Toshiyuki, Ogushi, Minoru, Wakisaka, Yoshihiro
• Primary Examiner(s): Zele, Krista
• Assistant Examiner(s): SCOTT, RANDY A
• Application Number:
  US12/068,704
• Publication Number:
  US 20080307075A1
• Time in Patent Office: 1,912 Days
• Field of Search: 709/220, 709/223, 709/224, 709/228
• 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 first sensor node of a plurality of sibling sensor nodes 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 continuous operation, the first sensor node intermittently activating to an operation mode and then deactivating to a sleep mode for a predetermined sleep time period, wherein the router node has a storage unit for storing a respective time configuration flag for each corresponding to each of the sibling sensor nodes;

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

wherein the first sensor node issues a command transmission request to the router node while activated to the operation mode prior to a next deactivation to the sleep mode;

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

wherein the sensor node in the operation mode sets an internal lime based on the time setting command from the router node, adds a time stamp to an observation value based on the internal time, and then transmits the observation value to the router node; and

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

wherein a processing unit of a management server connected to the gateway node calculates an influence between a first wearer wearing one sensor node and a second wearer wearing another sensor node, the influence is calculated based on a correlation determined between a first observation value transmitted by the sensor node worn by the first wearer and a second observation value transmitted by the sensor node worn by the second wearer that are both stored in an observation value storage unit of the management server.

2. A sensor-Net system according to claim 1, wherein the gateway node has a plurality of sibling router nodes, and has a management table for managing the sibling router nodes and the sibling sensor nodes;

and the gateway node, upon reception of the 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 sibling router nodes.

3. A sensor-Net system according to claim 1, wherein the first sensor node, after having sent the observation value to the router node, stores the observation value having the latest time added into the storage unit of the first sensor node, then enters into sleep mode of the intermittent operation.

4. A sensor-Net system according to claim 1, wherein the a management server is connected to the gateway node through a network and includes a communication unit for connecting to the network

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

5. A sensor-Net system according to claim 1, wherein the sensor nodes worn by the first and second wearer have respective acceleration sensors;

the sensor nodes worn by the first and second wearer transmit output data of the respective acceleration sensors as the first and second observation values; and

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

6. A sensor-Net system according to claim 1, wherein the router node, upon reception of the command transmission request from the first sensor node, transmits a command present, and transmits the latest time of the router node as the second time setting command.

7. A sensor-Net system according to claim 1, wherein the first sensor node, upon reception of the command present from the router node, waits for a time period in a stand-by state, and corrects the internal time based on the latest time of the router node received as the second time setting command.

8. A sensor-Net system, comprising a gateway node, and a first sensor node of a plurality of sensor nodes connected to the gateway node through a wireless communication, the gateway node being in continuous operation, the first sensor node intermittently activating to an operation mode and then deactivating to a sleep mode for a predetermined sleep time period,

wherein the first sensor node issues a time request command to the gateway node on a regular basis or upon connecting to the gateway node while activated to the operation mode prior to a next deactivation to the sleep mode, invokes an internal timer upon receiving a reply to the time request command from the gateway node, and transmits a polling request to the gateway node upon being activated to the operation mode following the next deactivation to the sleep mode;

wherein the gateway node transmits the reply to the time request command to the first sensor node and obtains a reference time upon receiving the time request command from the first sensor node, and transmits the reference time to the first sensor node upon receiving the polling command from the first sensor node;

wherein the first sensor node Stops the internal timer upon receiving the reference time, calculates an active time of the internal timer as a time difference between when the internal timer was invoked and when the internal timer was stopped, and then determines a current time by adding the active time of the internal timer to the reference time received from the gateway node,

wherein the first sensor node sets an internal time to the current time, adds a time stamp to an observation value based on the internal time, and then transmits the observation value to the gateway node; and

wherein a processing unit of a management server connected to the gateway node calculates an influence between a first wearer wearing one sensor node and a second wearer wearing another sensor node, the influence is calculated based on a correlation determined between a first observation value transmitted by the sensor node worn by the first wearer and a second observation value transmitted by the sensor node worn by the second wearer that are both stored in an observation value storage unit of the management server.

9. A sensor-Net system according to claim 8, wherein the management server is connected to the gateway node through a network and includes a communication unit for connecting to the network;

and

wherein the management server receives the observation value received by the gateway node from the first sensor node for storage in the storage unit.

10. A sensor node connected through a wireless communication to a gateway node being in continuous operation, the sensor node being in intermittent operation, 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 to the gateway node on a regular basis or upon connecting to the gateway node while activated to an operation mode prior to a next deactivation to a sleep mode, invokes an internal timer upon receiving a reply to the time request command from the gateway node, and, upon being activated to the operation mode following the next deactivation to the sleep mode, transmits a polling request to the gateway node and receives a reference time transmitted by the gateway node, the reference time being obtained by the gateway node upon receiving the time request command from the sensor node; and

wherein the sensor node stops the internal timer upon receiving the reference time, calculates an active time of the internal timer as a time difference between when the internal timer was invoked and when the internal timer was stopped, and then determines a current time by adding the active time of the internal timer to the reference time received from the gateway node, sets an internal time to the current time, adds a time stamp to an observation value based on the internal time, and then transmits the observation value to the gateway node; and

wherein a management server connected to the gateway node calculates an influence between a first wearer wearing one sensor node and a second wearer wearing another sensor node, the influence is calculated based on a correlation determined between a first observation values transmitted by the sensor node worn by the first wearer and a second observation value transmitted by the sensor node worn by the second wearer that are both stored in an observation value storage unit of the management server.

11. A sensor node according to claim 10, 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 internal timer to calculate the active time.