Casals Lluís, Gomez Carles, Vidal Rafael
Department of Network Engineering, Universitat Politècnica de Catalunya, 08860 Castelldefels, Spain.
Sensors (Basel). 2021 Sep 28;21(19):6478. doi: 10.3390/s21196478.
LoRaWAN has become a popular technology for the Internet of Things (IoT) device connectivity. One of the expected properties of LoRaWAN is high network scalability. However, LoRaWAN network performance may be compromised when even a relatively small number of devices use link-layer reliability. After failed frame delivery, such devices typically tend to reduce their physical layer bit rate by increasing their spreading factor (SF). This reaction increases channel utilization, which may further degrade network performance, even into congestion collapse. When this problem arises, all the devices performing reliable frame transmission end up using SF12 (i.e., the highest SF in LoRaWAN). In this paper, we identify and characterize the described network condition, which we call the SF12 Well, in a range of scenarios and by means of extensive simulations. The results show that by using alternative SF-management techniques it is possible to avoid the problem, while achieving a packet delivery ratio increase of up to a factor of 4.7.
LoRaWAN已成为物联网（IoT）设备连接的一项流行技术。LoRaWAN预期的特性之一是高网络可扩展性。然而，当即使相对少量的设备使用链路层可靠性时，LoRaWAN网络性能可能会受到影响。在帧传输失败后，此类设备通常倾向于通过增加扩频因子（SF）来降低其物理层比特率。这种反应会增加信道利用率，这可能会进一步降低网络性能，甚至导致拥塞崩溃。当出现此问题时，所有执行可靠帧传输的设备最终都会使用SF12（即LoRaWAN中的最高SF）。在本文中，我们在一系列场景中并通过广泛的模拟来识别和描述所描述的网络状况，我们将其称为SF12阱。结果表明，通过使用替代的SF管理技术，可以避免该问题，同时实现高达4.7倍的数据包交付率提升。
