| Summary: | 碩士 === 國立中正大學 === 通訊工程研究所 === 106 === Numerous types of IoT application emerge rapidly nowadays, such as indoor positioning, industrial equipment monitoring and human body movement monitoring. The requirements of these IoT sensors for different applications are diverse. For instance, an IoT system monitoring a large-scale area needs to emphasize the transmission range of the wireless sensors; battery-powered wireless sensors need to reduce the energy consumption; multiple sensors also may need to address accurate time synchronization. For the IoT which requiring low-power, long-distance and accurate time synchronization, no single existing wireless technology can meet all these requirements. By taking the advantage of low-power 2.4 GHz RF and long-distance LoRa technology, this study proposed a new design to achieve these goals without comprising the need of time synchronization. In this work, we develop a special router with dual RF interfaces, which can reduce the energy consumption of the wireless sensor nodes while also extend the communication range at the same time. The proposed design also enabling the wireless sensors can be time synchronized in the order of sub-microseconds, which resolve the issue of the conventional Bluetooth Low Energy (BLE) is difficult to perform very accurate time synchronization over multiple wireless sensors. The proposed design allowing the battery-powered wireless sensor extending its sleep duration to at-most four minutes for saving valuable energy. By comparing to BLE the proposed design the wireless sensors can reduce the radio receiving time for 86%. The field experiment was conducted in a real factory to monitoring machine tools with 30 wireless sensors. The performance of communication distance, power consumption and time synchronization accuracy was evaluated to demonstrate the correctness of this design.
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