Nippon Telegraph and Telephone Corporation

Shoichi Oshima

Kenichi Matsunaga

Hiroshi Nakashima

Hiroki Morimura

Shingo Tsukada

Takayuki Ogasawara

Rieko Sato

Toshihiko Kondo

Ahmed Musa

A sensor control circuit periodically transmits packets in synchronism with a one-by-one monotonous change in count values from a real-time clock circuit. The count values repeat the change within a predetermined numerical value range. The sensor control circuit transmits the count values by adding them to the packets. A collection control circuit acquires values of a reference clock synchronized with a reference time of an upper network from a reference clock generation circuit in accordance with reception of the packets, stores the values in a storage circuit as time stamps representing arrival times of the packets, performs statistical processing of the time stamps and the count values concerning the packets received, and corrects the time stamps based on an packet transmission interval and a reference arrival time representing the arrival time of a head packet, which are obtained from the statistical processing.

Sensing system and time stamp correction method

In a sensor relay apparatus (), a storage unit () stores a communication protocol correspondence list (B) in which a sensor terminal (ST) and a communication protocol are registered in association with each other, and a communication format (C) to be used in the communication protocol, a relay processing unit () communicates with the sensor terminal (ST) specified in the communication protocol correspondence list (B) based on the communication protocol associated with the sensor terminal (ST), receives sensor data detected by the sensor terminal (ST), converts the format of the sensor data based on the communication format (C) in association with the communication protocol, and relays and transfers the sensor data to a processing apparatus (), and a relay managing unit () updates the communication protocol correspondence list (B) or the communication format (C) in the storage unit (), based on a communication protocol correspondence list or a communication format newly notified from the processing apparatus ().

Sensor relay apparatus and sensor relay system

Upon receiving a dummy packet, a data collection terminal slave device () appends, to a return packet, a timestamp indicating the reception time of the dummy packet and a timestamp indicating the transmission time of the return packet, and transmits the return packet to a data collection terminal master device (). When performing a time synchronization process, the data collection terminal master device () transmits the dummy packet to the data collection terminal slave device (). Upon receiving the return packet, the data collection terminal master device () calculates a synchronization deviation time of the data collection terminal master device () and the data collection terminal slave device () and a propagation delay time between the data collection terminal master device () and the data collection terminal slave device (), based on the transmission time of the dummy packet and the reception time of the return packet, and the reception time of the dummy packet and the transmission time of the return packet obtained from the timestamps of the return packet.

Sensing system and time synchronization method

In a sensor relay apparatus (), a communication control unit () receives sensor data from a sensor terminal (ST) via a terminal module () when a transmission data amount related to the sensor data to be transmitted from the sensor terminal (ST) is equal to or greater than a determination threshold. This can reduce the overhead time taken at the time of the transmission of the sensor data.

In a sensor data acquisition terminal (), an NTP back-end processing unit () synchronizes a terminal timing with a parent terminal timing by exchanging NTP packets for time synchronization with a parent terminal () based on NTP, and a protocol conversion unit () converts an NTP packet, which is output from the NTP back-end processing unit () and will be transmitted to the parent terminal (), to a TPSN packet based on TPSN, outputs the TPSN packet to a wireless processing unit (), converts a TPSN packet from the parent terminal (), which is output from the wireless processing unit (), to an NTP packet, and outputs the NTP packet to the NTP back-end processing unit ().

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Tokyo, Japan

Shoichi Oshima