Zorbas Dimitrios, Caillouet Christelle, Abdelfadeel Hassan Khaled, Pesch Dirk
Tyndall National Institute, University College Cork, Cork T12R5CP, Ireland.
School of Engineering and Digital Sciences, Nazarbayev University, Nur-Sultan 010000, Kazakhstan.
Sensors (Basel). 2021 Feb 8;21(4):1193. doi: 10.3390/s21041193.
LoRa is a low-power and long range radio communication technology designed for low-power Internet of Things devices. These devices are often deployed in remote areas where the end-to-end connectivity provided through one or more gateways may be limited. In this paper, we examine the case where the gateway is not available at all times. As a consequence, the sensing data need to be buffered locally and transmitted as soon as a gateway becomes available. However, due to the Aloha-style transmission policy of current LoRa-based standards, such as the LoRaWAN, delivering a large number of packets in a short period of time by a large number of nodes becomes impossible. To avoid bursts of collisions and expedite data collection, we propose a time-slotted transmission scheduling mechanism. We formulate the data scheduling optimisation problem, taking into account LoRa characteristics, and compare its performance to low complexity heuristics. Moreover, we conduct a set of simulations to show the benefits of synchronous communications on the data collection time and the network performance. The results show that the data collection can reliably be achieved at least 10 times faster compared to an Aloha-based approach for networks with 100 or more nodes. We also develop a proof-of-concept to assess the overhead cost of communicating the schedule to the nodes and we present experimental results.
LoRa是一种专为低功耗物联网设备设计的低功耗、远距离无线通信技术。这些设备通常部署在偏远地区，通过一个或多个网关提供的端到端连接可能受到限制。在本文中，我们研究了网关并非始终可用的情况。因此，传感数据需要在本地进行缓冲，并在网关可用时立即传输。然而，由于当前基于LoRa的标准（如LoRaWAN）采用Aloha风格的传输策略，大量节点在短时间内发送大量数据包变得不可能。为了避免冲突突发并加快数据收集，我们提出了一种时隙传输调度机制。我们考虑LoRa特性，制定数据调度优化问题，并将其性能与低复杂度启发式算法进行比较。此外，我们进行了一组模拟，以展示同步通信在数据收集时间和网络性能方面的优势。结果表明，对于具有100个或更多节点的网络，与基于Aloha的方法相比，数据收集速度至少可以可靠地提高10倍。我们还开发了一个概念验证，以评估将调度信息传达给节点的开销成本，并展示了实验结果。
