Sensing is an activity of paramount importance for smart cities. The coverage of large areas based on reduced infrastructure and low energy consumption is desirable. In this context, Low Power Wide Area Network (LPWAN) plays an important role. In this paper, we investigate LoRa, a low-power technology offering large coverage, but low transmission rates. Radio range and data rate are tunable by using different spreading factors and coding rates, which are configuration parameters of the LoRa physical layer. LoRa can cover large areas but variations in the environment affect link quality. This work studies the propagation of LoRa signals in forest, urban, and suburban vehicular environments. Besides being environments with variable propagation conditions, we evaluate scenarios with node mobility. To characterize the communication link, we mainly use the Received Signal Strength Indicator (RSSI), Signal to Noise Ratio (SNR), and Packet Delivery Ratio (PDR). As for node mobility, speeds are chosen according to prospective applications. Our results show that the link reaches up to 250 m in the forest scenario, while in the vehicular scenario it reaches up to 2 km. In contrast, in scenarios with high-density buildings and human activity, the maximum range of the link reaches up to 200 m in the urban scenario.

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关于LoRa信号在森林，城市和郊区环境中传播的研究

传感是智慧城市最重要的活动。基于减少的基础设施和低能耗的大面积覆盖是可取的。在这种情况下，低功耗广域网（LPWAN）发挥着重要作用。在本文中，我们研究了LoRa，这是一种低功率技术，具有覆盖范围广，传输速率低的特点。通过使用不同的扩频因子和编码速率（它们是LoRa物理层的配置参数），可以调整无线电范围和数据速率。LoRa可以覆盖很大的区域，但是环境的变化会影响链路质量。这项工作研究了LoRa信号在森林，城市和郊区车辆环境中的传播。除了具有可变传播条件的环境之外，我们还评估具有节点移动性的方案。为了表征通信链接，我们主要使用接收信号强度指示器（RSSI），信噪比（SNR）和数据包传输率（PDR）。至于节点移动性，根据预期应用选择速度。我们的结果表明，在森林场景中，该链接可达250 m，而在车辆场景中，该链接可达2 km。相反，在具有高密度建筑物和人类活动的场景中，在城市场景中，链接的最大范围可达200​​ m。