Scheduling Algorithm Considering Interference Interval for LPWA

LoRaWAN is one of the radio communication standards of low power wide area network (LPWA) using the chirp spread spectrum. In uplink communication of LoRaWAN, packet retransmission is used to compensate for packet loss due to packet collisions caused by interference coming from other systems on the same frequency band. However, simple packet re-transmission increases packet collisions on the massive system condition since collision avoidance is not considered in LoRaWAN. Therefore, in this paper, we propose an adaptive transmission timing control algorithm for avoiding periodic interference from other systems by estimating their intervals. In our method, an environment with multiple LoRa gateways and LoRa nodes are considered and the received power of interference signals at each LoRa gateway is shared among all LoRa gateways. LoRa gateways can distinguish the system of interfering signals by comparing with the Euclid distances between the data sets of the received power of the interfering signals and the data sets of the received power of the signals come from other interfering systems. In addition, whether the interfering system communicates periodically or not is figured out from the information of the interference interval. LoRa gateways predict the timings that the LoRaWAN system is less interfered considering the periodically interfering systems and control the packet transmission timing of LoRa nodes. The simulation results show the proposed method reduces the packet loss rate compared to the existing system without a significant decrease in throughput.