NETWORK TERMINAL, NETWORK SYSTEM, TIME SYNCHRONIZATION METHOD, AND TIME SYNCHRONIZATION PROGRAM

• US 20120027030A1
• Filed: 04/05/2010
• Published: 02/02/2012
• Est. Priority Date: 04/10/2009
• Status: Active Grant

• Current Assignee: Omron Corporation, University of Tokyo
• Original Assignee: Omron Corporation, University of Tokyo
• Inventors: Naito, Takeshi, Kamijo, Shunsuke, Fujimura, Kaichi
• Granted Patent: US 8,867,434 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: G01V 1/22 Transmitting seismic signals to recording or processing apparatus
• CPC Class Codes: G01V 2200/12 Clock synchronization-related issues
• CPC Class Codes: G04G 5/00 Setting, i.e. correcting or changing, the time-indication radio-controlled time-pieces G04R
• CPC Class Codes: G04G 7/00 Synchronisation radio-controlled time-pieces G04R
• CPC Class Codes: G06F 1/14 Time supervision arrangements, e.g. real time clock

Abstract

A network terminal has communication section that communicates with other network terminals connected via a network, time-series data creation section that, at timing set beforehand, creates time information including a correspondence between an identification number of the own network terminal and a current time measured by a timer of the own network terminal and creates time-series data registering the time information, and additional registration section that, when the communication section receives the time-series data transmitted from another network terminal, creates time information including a correspondence between the identification number of the own network terminal and a current time measured by the timer of the own network terminal and additionally registers the time information to the time-series data received this time.

Claims

1. A network terminal, comprising:

communication section that communicates with other network terminals connected via a network;

time-series data creation section that, at timing set beforehand, creates time information including a correspondence between an identification number of the own network terminal and a current time measured by a timer of the own network terminal and creates time-series data registering the time information;

additional registration section that, when the communication section receives the time-series data transmitted from another network terminal, creates time information including a correspondence between the identification number of the own network terminal and a current time measured by the timer of the own network terminal and additionally registers the time information to the time-series data received this time;

transfer destination decision section that decides a network terminal as a transfer destination for each of time-series data created by the time-series data creation means section and time-series data to which the additional registration section additionally registers time information;

transfer section that, every time the transfer destination decision section decides a transfer destination of the time-series data, makes the communication section transfer the time-series data;

determination section that determines that time-series data to which the time information is additionally registered by the additional registration section satisfies a time-setting condition when the number of network terminals registering the time information a plurality of times exceeds a threshold number of network terminals set beforehand; and

time-setting section that, when the determination section determines that the time-setting condition is satisfied, performs time-setting by correcting a time measured by the timer of the own network terminal on a basis of time information registered in the time-series data.

2. The network terminal according to claim 1, wherein

the time-setting section calculates, for each of network terminals registering the time information a plurality of times, an average transferring processing time required for transferring of the time-series data between any two network terminals on a basis of time duration between time information firstly registered by this network terminal and time information last registered by this network terminal and a number of times of transferring between the time duration,

the time-setting section calculates an average origin point time using the calculated average transferring processing time for each of network terminals registering the time information a plurality of times, the average origin point time being an average of times measured by timers at specific timing, and

the time-setting section further calculates a correction time to correct a time measured by the timer of the own network terminal on a basis of the calculated average transferring processing time and average origin point time.

3. The network terminal according to claim 1, wherein the determination section determines that the time-setting condition is satisfied when the number of network terminals registering the time information a plurality of times and performing transferring during duration between the time information firstly registered and the time information last registered exceeding a transferring threshold number of times set beforehand exceeds a threshold number of network terminals set beforehand in the time-series data.

4. The network terminal according to claim 1, wherein

the transfer destination decision section sets, as a transmission destination, a network terminal having a minimum number of registrations of time information in the time-series data to be transferred this time among the network terminals connected via the network, and when the network terminal set as the transmission destination is not communicable directly, the transfer destination decision section decides, as a transfer destination, another network terminal that is located on a communication path with the network terminal and is directly communicable.

5. The network terminal according to claim 4, wherein when a transmission destination set in the time-series data transmitted from another network terminal received by the communication section is other than the own network terminal, the transfer destination decision section does not set a transmission destination for the time-series data.

6. The network terminal according to claim 1, further comprising first transfer prohibition section that prohibits transferring of time-series information that the time-setting section uses for time-setting of the timer of the own network terminal to another network terminal.

7. The network terminal according to claim 1, wherein when the communication section receives the time-series data transmitted from another network terminal after completion of time-setting of the timer by the time-setting section, the additional registration section creates the time information on a basis of a time measured by the timer before the time-setting by the time-setting section and additionally registers the time information to the time-series data received this time.

8. The network terminal according to claim 1, further comprising recreation instruction section that, when the transfer section fails to transfer the time-series data, makes a notice to instruct a network terminal creating the time-series data to recreate the time-series data.

9. The network terminal according to claim 1, wherein the transfer section transfers a status table with the time-series data, the status table registering a state of communicability for each of the network terminals connected via the network.

10. The network terminal according to claim 9, wherein

the status table is a table registering a communicable state and completion/incompletion of time-setting of the timer by the time-setting section for each of the network terminals connected via the network, wherein

the network terminal further comprises second transfer prohibition section that prohibits transferring of the status table and corresponding time-series information when a state of all of the network terminals registered in the status table shows either one of an incommunicable state and completion of time-setting for the timer.

11. A network system connecting a plurality of network terminals in a communicable manner via a network, each network terminal comprising:

communication section that communicates with other network terminals connected via the network;

time-series data creation section that, at timing set beforehand, creates time information including a correspondence between an identification number of the own network terminal and a current time measured by a timer of the own network terminal and creates time-series data registering the time information;

additional registration section that, when the communication section receives the time-series data transmitted from another network terminal, creates time information including a correspondence between the identification number of the own network terminal and a current time measured by the timer of the own network terminal and additionally registers the time information to the time-series data received this time;

transfer destination decision section that decides a network terminal as a transfer destination for each of time-series data created by the time-series data creation section and time-series data to which the additional registration section additionally registers time information;

transfer section that, every time the transfer destination decision section decides a transfer destination of the time-series data, makes the communication section transfer the time-series data;

determination section that determines whether time-series data to which the time information is additionally registered by the additional registration section satisfies a set time-setting condition or not; and

time-setting section that, when the determination section determines that the time-setting condition is satisfied, corrects a time measured by the timer of the own network terminal on a basis of time information registered in the time-series data, wherein

the determination section determines that, when the number of network terminals registering the time information a plurality of times exceeds a threshold number of network terminals set beforehand in the time-series data, the time-setting condition is satisfied.

12. A time synchronization method for terminals in a network system connecting a plurality of network terminals in a communicable manner via a network, each network terminal performing the steps of:

creating, at timing set beforehand, time information including a correspondence between an identification number of the own network terminal and a current time measured by a timer of the own network terminal and creating time-series data registering the time information;

when communication section receives the time-series data transmitted from another network terminal, creating time information including a correspondence between the identification number of the own network terminal and a current time measured by the timer of the own network terminal and additionally registering the time information to the time-series data received this time;

deciding a network terminal as a transfer destination for each of time-series data created by the own network terminal and time-series data to which time information is additionally registered by the own network terminal;

every time a transfer destination of the time-series data is decided, transferring the time-series data with the communication section;

when the number of network terminals registering the time information a plurality of times exceeds a threshold number of network terminals set beforehand in the time-series data to which the own network terminal additionally registers the time information, determining that a time-setting condition is satisfied; and

when it is determined that the time-setting condition is satisfied, performing time-setting by correcting a time measured by the timer of the own network terminal on a basis of time information registered in the time-series data.

13. A time synchronization program making a network terminal provided with communication section that communicates with other network terminals connected via a network function as:

time-series data creation section that, at timing set beforehand, creates time information including a correspondence between an identification number of the own network terminal and a current time measured by a timer of the own network terminal and creates time-series data registering the time information;

additional registration section that, when the communication section receives the time-series data transmitted from another network terminal, creates time information including a correspondence between the identification number of the own network terminal and a current time measured by the timer of the own network terminal and additionally registers the time information to the time-series data received this time;

transfer destination decision section that decides a network terminal as a transfer destination for each of time-series data created by the time-series data creation section and time-series data to which time information is additionally registered by the additional registration section;

transfer section that, every time the transfer destination decision section decides a transfer destination of the time-series data, makes the communication section transfer the time-series data;

determination section that determines that time-series data to which the time information is additionally registered by the additional registration section satisfies a time-setting condition when the number of network terminals registering the time information a plurality of times exceeds a threshold number of network terminals set beforehand; and

time-setting section that, when the determination section determines that the time-setting condition is satisfied, performs time-setting by correcting a time measured by the timer of the own network terminal on a basis of time information registered in the time-series data.