Modern Industrial Internet of Things (IIoT) is often designed to support geographically disperse nodes in large quantities. Satellites have unparalleled superiority in terms of coverage, making themselves ideal candidates as wide area IIoT access points. Antenna arrays (AAs) empower the satellites with beamforming capability, a key feature to accommodate various technical challenges of IIoT. In this survey, we are mainly focused on the calibration of spaceborne beamformers. We define the system model of the calibration tasks, and formulate the parameters of interest for the AAs and the beamforming network. Classic parallel calibration strategies for downlink AA based on orthogonal CDMA (OCDMA) are reviewed, and then extended to the on-ground, wired calibration of the BFN for improved efficiency and reduced manpower. By breaking the orthogonality among the calibrating signals, a new non-orthogonal multiple access (NOMA)-based calibration scheme is demonstrated to be M× more efficient than its OCDMA precedent without evident penalty in the calibration accuracy, where $M$ is the number of array elements. We also report our latest progress on the NOMA-based co-channel transmission of the communication and the calibrating signals but without mutual interference. Prototypes and experimental scenarios are introduced. Theoretical analyses and computer simulations are further verified by hardware experiments.

中文翻译：

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面向IIoT的卫星的天线阵列校准：从正交CDMA到NOMA

现代工业物联网（IIoT）通常被设计为支持地理上分散的节点。卫星在覆盖范围方面具有无与伦比的优势，使其成为广域IIoT接入点的理想候选者。天线阵列（AA）使卫星具有波束成形功能，这是应对IIoT各种技术挑战的关键功能。在本次调查中，我们主要关注星载波束形成器的校准。我们定义了校准任务的系统模型，并为AA和波束形成网络制定了感兴趣的参数。回顾了基于正交CDMA（OCDMA）的下行链路AA的经典并行校准策略，然后将其扩展到BFN的地面有线校准，以提高效率并减少人力。$ M $是数组元素的数量。我们还报告了在基于NOMA的通信和校准信号同信道传输但没有相互干扰的最新进展。介绍了原型和实验方案。理论分析和计算机仿真通过硬件实验得到了进一步验证。