In the current context of massive IoT, the Pure-Aloha scheme used in LoRaWAN is reaching its limit, and Slotted-Aloha is being considered as an alternative, as it offers twice Pure-Aloha's packet success rate. It however requires synchronization across the nodes. In this paper, we propose a new slot structure adapted to devices with low quality clock, and a duty-cycle efficient synchronization protocol for LoRaWAN class A devices with the lowest overhead to date. We discuss the conditions of its integration into LoRaWAN. The experimental results confirm that it succeeds in tracking each device's synchronization state, identifying the exact moment they desynchronize and resynchronizing them. The proposed protocol is also proven to be more duty-cycle efficient than existing fixed-rate synchronization solutions.

翻译：在当前大规模物联网的背景下，LoRaWAN中采用的纯Aloha方案正趋于其性能极限，而时隙Aloha因其能提供两倍于纯Aloha的数据包成功率，正被视为一种替代方案。然而，该方案需要节点间的同步。本文提出了一种适用于低质量时钟设备的新型时隙结构，以及一种迄今为止开销最低、面向LoRaWAN A类设备的高效占空比同步协议。我们讨论了将其集成到LoRaWAN中的条件。实验结果证实，该协议能成功跟踪各设备的同步状态，精确识别其失同步的时刻并完成重同步。所提协议也被证明比现有的固定速率同步方案具有更高的占空比效率。