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Abstract: inflight broadband connectivity (commonly termed as inflight connectivity) can be considered one of the remaining milestones for ubiquitous Internet provision; therefore, several enabling technologies are being investigated to provide high-capacity, reliable, and affordable Internet access. multiple-input multiple-output (MIMO), based on the space–;time processing (STP) concept, is one of the dominant technologies that consistently appear on the list of inflight connectivity (IFC) enablers. STP shows the potential to significantly increase user throughput, improve spectral/energy efficiencies, and increase the capacity as well as reliability of airborne networks through spatial multiplexing/diversity techniques. This article presents the preliminary outcomes of substantial research on STP techniques for enabling IFC, as the exploratory study on this topic is still in its early stages. We explore the theoretical principles behind different STP techniques and their implementation in airborne networks in direct air-to-ground (A2G) scenarios for the provision of a reliable and high-speed IFC. We also analyze the current technologies and techniques used for IFC and highlight their benefits and limitations. We present a comprehensive review that compares different STP techniques using metrics such as bit error rate (BER), spectral efficiency (SE), and capacity. Last, but not least, we discuss the substantial research challenges encountered and the prospective future research avenues that require special attention for enhancing the deployment of STP systems in forthcoming airborne networks, particularly for enabling IFC. Overall, this research study contributes to the body of knowledge by providing insights into the use of STP techniques in airborne networks for enabling IFC. It emphasizes the theoretical foundations, presents a literature review, discusses challenges and limitations, identifies potential areas for future research, and provides a performance analysis.

面向机上宽带连接的空时处理：关键分析、挑战与未来方向

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