| （英） |
In recent years, Low Power Wide Area-networks (LPWA) that use the sub-GHz band, such as LoRa, have become widely used due to the spread of the Internet of Things (IoT). However, as the number of LPWAs increases, the sub-GHz band becomes congested and packet collisions become a problem. In their research, Osada et al. proposed a packet collision avoidance method based on the reciprocal phase synchronization phenomenon of nonlinear oscillators and demonstrated autonomous asynchronization without the need for centralized control for many devices implemented in WiSUN. In this paper, we apply this autonomous decentralized collision avoidance method to LoRa and evaluate its performance by implementing it in a real device. In the experiment, we prepared terminals controlled by an Arduino Pro Mini microcontroller with a commercially available LoRa module called ES920LR, transmitted from each terminal, and measured the time when the packets arrived. The method of implementing this technique was to monitor the transmission time of the terminal and the communication time of the other terminals before and after the transmission time, and to determine the next transmission time based on the time difference. Experimental results showed that this method can effectively desynchronize the timing of packet transmission between LoRa devices and autonomously reduce collisions when multiple devices are connected, resulting in a reduced collision rate compared to a method that transmits at regular intervals without special implementation. |