Direct-to-satellite IoT DtS IoT communication structure is a promising solution to provide connectivity and extend the coverage of traditional low-power and long-range technologies, especially for isolated and remote areas where deploying traditional infrastructure is impracticable. Despite their bounded visibility, the Low Earth Orbit LEO satellites complement the terrestrial networks, offering broader gateway coverage and terrestrial network traffic offloading. However, the dynamics of LEO and the nature of such integration come with several challenges affecting the efficacy of the network. Therefore, this paper proposes Beacon based Uplink LoRaWAN BU LoRaWAN to enhance satellite-terrestrial communication efficiency. The proposed scheme exploits the LoRaWAN class B synchronization mechanism to provide efficient uplink transmission from LoRaWAN devices placed on the ground to satellite gateways. BU LoRaWAN proposes an uplink transmission slot approach to synchronize ground devices uplink traffic with LEO based orbiting gateways. It also uses a queue data structure to buffer end devices ready to send packets until the appropriate moment. BU LoRaWAN avoids possible transmission collision by optimizing a random transmission slot for an end device within the beacon window. The proposed system is implemented and evaluated using OMNeT network simulator and FLoRaSat framework. The result demonstrates the feasibility of the proposed system. BU-LoRaWAN achieves better performance compared to the standard LoRaWAN, which manages to deliver almost double the traffic delivered by the standard one.

翻译：直连卫星物联网通信架构是一种极具前景的解决方案，可为传统低功耗广域网技术提供连接并扩展其覆盖范围，尤其适用于部署传统基础设施不可行的偏远和孤立地区。尽管低地球轨道卫星的可见时间有限，但其作为地面网络的补充，能够提供更广阔的网关覆盖并分流地面网络流量。然而，LEO卫星的动态特性以及此类集成架构的本质，也给网络效能带来了若干挑战。为此，本文提出基于信标的LoRaWAN上行传输方案，以提升星地通信效率。该方案利用LoRaWAN B类同步机制，为部署在地面的LoRaWAN设备到卫星网关的上行传输提供高效支持。BU-LoRaWAN提出一种上行传输时隙方法，使地面设备的上行流量与基于LEO的轨道网关同步。同时采用队列数据结构缓存准备发送数据包的终端设备，直至合适的传输时机。该方案通过在信标窗口内为终端设备优化随机传输时隙，避免了可能的传输冲突。所提系统使用OMNeT网络模拟器和FLoRaSat框架进行实现与评估。结果表明该系统具有可行性。与标准LoRaWAN相比，BU-LoRaWAN实现了更优的性能，其成功传输的业务量接近标准方案的两倍。