Time synchronization method, sensor data acquisition terminal, and sensor network system
In a sensor data acquisition terminal ( 10 ), an NTP back-end processing unit ( 12 ) synchronizes a terminal timing with a parent terminal timing by exchanging NTP packets for time synchronization with a parent terminal ( 20 ) based on NTP, and a protocol conversion unit ( 13 ) converts an NTP packet, which is output from the NTP back-end processing unit ( 12 ) and will be transmitted to the parent terminal ( 20 ), to a TPSN packet based on TPSN, outputs the TPSN packet to a wireless processing unit ( 14 ), converts a TPSN packet from the parent terminal ( 20 ), which is output from the wireless processing unit ( 14 ), to an NTP packet, and outputs the NTP packet to the NTP back-end processing unit ( 12 ).
1. A time synchronization method for a plurality of terminals wirelessly connected to a parent terminal, including a back-end processing step of generating a first NTP (Network Time Protocol packet indicating a time synchronization request that is addressed to the parent terminal, and synchronizing a terminal timing of a terminal with a parent terminal timing of the parent terminal in accordance with a second NTP packet indicating a time synchronization response from the parent terminal based on NTP, said method further comprising:
a step of converting the first NTP packet indicating the time synchronization request generated in the back-end processing step to a first TPSN (Timing-sync Protocol for Sensor Network) packet indicating the time synchronization request based on TPSN,
a wireless processing step of transmitting the first TPSN packet indicating the time synchronization request to the parent terminal and receiving a second TPSN packet indicating the time synchronization response that is returned from the parent terminal, by wireless communication; and
a step of converting the second TPSN packet indicating the time synchronization response received from the parent terminal in the wireless processing step, to the second NTP packet indicating the time synchronization response,
wherein the back-end processing step includes synchronizing the terminal timing of the terminal with the parent terminal timing of the parent terminal in accordance with the second NTP packet indicating the time synchronization response that is converted from the second TPSN packet indicating the time synchronization response.
2. The time synchronization method according to claim 1 , wherein the wireless processing step includes executing firmware corresponding to a plurality of different wireless standards on a module, and includes a step of performing wireless communication with the parent terminal based on firmware corresponding to a wireless standard selected in advance.
3. The time synchronization method according to claim 2 , wherein the wireless processing step includes a step of selecting firmware corresponding to a wireless standard matching a communication performance request received from the parent terminal.
4. The time synchronization method according to claim 3 , wherein the wireless processing step includes a step of selecting firmware corresponding to a wireless standard having a lowest power consumption, among wireless standards matching the communication performance request.
5. A sensor data acquisition terminal that collects sensor data detected by a plurality of wireless sensor terminals, and wirelessly transmits the sensor data to a parent terminal, comprising:
a wireless processing unit configured to exchange various packets with the parent terminal by wireless communication;
a back-end processing unit configured to generate a first NTP (Network Time Protocol) packet indicating a time synchronization request that is addressed to the parent terminal, and synchronize a terminal timing of a wireless sensor terminal with a parent terminal timing of the parent terminal in accordance with a second NTP packet indicating a time synchronization response from the parent terminal based on NTP; and
a protocol conversion unit configured to convert the first NTP packet indicating a the time synchronization request generated by the back-end processing unit, to a first TPSN (Timing-sync Protocol for Sensor Network) packet indicating the time synchronization request based on TPSN, and output the first TPSN packet indicating the time synchronization request to the wireless processing unit, and convert a second TPSN packet indicating the time synchronization response from the parent terminal, which is output from the wireless processing unit, to the second NTP packet indicating the time synchronization response, and output the second NTP packet indicating the time synchronization response to the back-end processing unit,
wherein the wireless processing unit transmits the first TPSN packet indicating the time synchronization request output from the protocol conversion unit, and receives the second TPSN packet indicating the time synchronization response from the parent terminal and outputs the second TPSN packet indicating the time synchronization response to the protocol conversion unit.
6. The sensor data acquisition terminal according to claim 5 , wherein the wireless processing unit includes a module of firmware corresponding to a plurality of different wireless standards, and performs wireless communication with the wireless sensor terminals based on firmware corresponding to a wireless standard selected from the wireless standards based on communication performance information obtained from the wireless sensor terminals.
7. The sensor data acquisition terminal according to claim 6 , wherein the wireless processing unit wirelessly transmits the sensor data to the parent terminal, based on a transmission timing unique to the sensor data acquisition terminal designated by the parent terminal, and a terminal timing obtained after time synchronization.
8. A sensor network system comprising a parent terminal, and a plurality of sensor data acquisition terminals that collect sensor data detected by a plurality of wireless sensor terminals and wirelessly transmit the sensor data to the parent terminal, wherein the sensor data acquisition terminal is a sensor data acquisition terminal cited in claim 7 .
9. A sensor network system comprising a parent terminal, and a plurality of sensor data acquisition terminals that collect sensor data detected by a plurality of wireless sensor terminals and wirelessly transmit the sensor data to the parent terminal, wherein the sensor data acquisition terminal is a sensor data acquisition terminal cited in claim 6 .
10. A sensor network system comprising a parent terminal, and a plurality of sensor data acquisition terminals that collect sensor data detected by a plurality of wireless sensor terminals and wirelessly transmit the sensor data to the parent terminal, wherein the sensor data acquisition terminal is a sensor data acquisition terminal cited in claim 5 .
11. The sensor data acquisition terminal according to claim 5 , wherein the wireless processing unit wirelessly transmits the sensor data to the parent terminal, based on a transmission timing unique to the sensor data acquisition terminal designated by the parent terminal, and a terminal timing obtained after time synchronization.
12. A sensor network system comprising a parent terminal, and a plurality of sensor data acquisition terminals that collect sensor data detected by a plurality of wireless sensor terminals and wirelessly transmit the sensor data to the parent terminal, wherein the sensor data acquisition terminal is a sensor data acquisition terminal cited in claim 11 .