天基大规模无线物联网系统物理层同步获取与随机接入技术研究

Restricted by factors such as topography, deployment cost, coverage and so on, terrestrial-based massive Internet of Things (IoT) systems (like NB-IoT, LoRa and Sigfox) nowadays cannot fulfill the goal of IoT to seamlessly connect anything in the world at all times and places. Satellite-based wireless access technique makes a breakthrough with its wide coverage and long communication range, and thus is an important and necessary supplement to the current terrestrial massive IoT networks. However, the deployment of satellite-based massive IoT networks incurs serious problems like large frequency offset, low SINR, and massive access devices covered by a single satellite. Therefore, it is rather challenging for the device to acquire the system synchronization and access the system. The purpose of this study is thus to investigate the available wireless communication mechanisms as well as the satellite communication systems that are suitable for such satellite-based applications, and propose a practical physical layer transmission structure. The focus of this study is the design of synchronization acquisition and random access schemes that are specially tailored to meet the low cost, wide/deep coverage, low power, as well as long battery life requirements for the massive IoT devices.

当前地基大规模物联网技术（如NB-IoT、LoRa、Sigfox等）受限于地形环境、基础设施部署的成本开销以及覆盖范围等因素，尚无法实现大规模物联网全球部署、无缝交互的愿景。基于卫星的大规模物联网无线接入技术由于其覆盖范围大、通信距离远等特点，可突破地理位置的局限性解决信息孤岛的问题，是对当前地基无线接入技术非常重要的补充以及支撑。然而，天基大规模物联网将带来大频偏、低SINR以及同一个卫星覆盖下接入设备数量巨大等问题，严重影响系统设备的同步获取与随机接入性能。本项目拟对现有的无线通信技术以及卫星通信系统进行深入研究，结合大规模物联网的频段特性，着重解决如何实现天基大规模物联网物理层传输结构设计问题，旨在提出一个新颖的适合天基大规模物联网的系统获取以及随机接入方案，满足大规模物联网设备低成本、广覆盖、深覆盖、低功率、长电池使用寿命的要求。

基于卫星的大规模物联网无线接入技术由于其覆盖范围大、通信距离远等特点，可突破地理位置的局限性解决信息孤岛的问题，是对当前地基无线接入技术非常重要的补充以及支撑。然而，天基大规模物联网带来的大频偏、低SINR等问题，使得物理层信号的设计成为一个难点，尤其是系统同步获取信号以及随机接入信号。本项目从理论上全面分析了当前地面蜂窝通信系统中基于Zadoff-Chu（ZC）序列的随机接入信号在频偏情况下的“能量衰减”和“能量泄露”问题，提出了一个新的具有抗频偏特性的检测准则，分析出了在使用该准则时能够满足应用场景需求的ZC序列的根值以及循环移位集合所具有的性质。在此基础上，结合天基大规模物联网系统的具体性能需求以及和地面通信系统的设计相兼容，本项目给出了具体的构建基于ZC序列的随机接入信号集合的设计方案。此外，本项目提出了两种同步信号设计方案，一是通过差分的方式进行同步信号设计，另一种是具有频偏适应性的同步信号设计方案。目前，两种方案都在改善中以适应天基系统低成本、广覆盖、深覆盖、低功率、长电池使用寿命等特性。该课题的研究将为天地一体化大规模物联网系统物理层的实现提供新的解决方案以及实现途径。