Department of Information and Communication Engineering, Chosun University, Gwangju 61452, Korea.
Sensors (Basel). 2020 May 6;20(9):2645. doi: 10.3390/s20092645.
A long-range wide area network (LoRaWAN) adapts the ALOHA network concept for channel access, resulting in packet collisions caused by intra- and inter-spreading factor (SF) interference. This leads to a high packet loss ratio. In LoRaWAN, each end device (ED) increments the SF after every two consecutive failed retransmissions, thus forcing the EDs to use a high SF. When numerous EDs switch to the highest SF, the network loses its advantage of orthogonality. Thus, the collision probability of the ED packets increases drastically. In this study, we propose two SF allocation schemes to enhance the packet success ratio by lowering the impact of interference. The first scheme, called the channel-adaptive SF recovery algorithm, increments or decrements the SF based on the retransmission of the ED packets, indicating the channel status in the network. The second approach allocates SF to EDs based on ED sensitivity during the initial deployment. These schemes are validated through extensive simulations by considering the channel interference in both confirmed and unconfirmed modes of LoRaWAN. Through simulation results, we show that the SFs have been adaptively applied to each ED, and the proposed schemes enhance the packet success delivery ratio as compared to the typical SF allocation schemes.
长距离广域网 (LoRaWAN) 适应了 ALOHA 网络概念的信道接入方式，从而导致了由内部分散因子 (SF) 和外部分散因子 (SF) 干扰引起的分组冲突。这导致了高分组丢失率。在 LoRaWAN 中，每个终端设备 (ED) 在两次连续重传失败后递增 SF，从而迫使 ED 使用高 SF。当大量 ED 切换到最高 SF 时，网络失去了正交性的优势。因此，ED 数据包的碰撞概率急剧增加。在这项研究中，我们提出了两种 SF 分配方案，通过降低干扰的影响来提高分组成功率。第一种方案称为信道自适应 SF 恢复算法，根据 ED 数据包的重传情况递增或递减 SF，指示网络中的信道状态。第二种方法根据 ED 在初始部署期间的灵敏度为 ED 分配 SF。通过考虑 LoRaWAN 的确认和未确认模式下的信道干扰，通过广泛的仿真验证了这些方案。通过仿真结果表明，自适应地为每个 ED 应用了 SF，与典型的 SF 分配方案相比，所提出的方案提高了分组成功传输率。
