Sixth-generation (6G) mobile communication networks are expected to have dense infrastructures, large antenna size, wide bandwidth, cost-effective hardware, diversified positioning methods, and enhanced intelligence. Such trends bring both new challenges and opportunities for the practical design of 6G. On one hand, acquiring channel state information (CSI) in real time for all wireless links becomes quite challenging in 6G. On the other hand, there would be numerous data sources in 6G containing high-quality location-tagged channel data, e.g., the estimated channels or beams between base station (BS) and user equipment (UE), making it possible to better learn the local wireless environment. By exploiting this new opportunity and for tackling the CSI acquisition challenge, there is a promising paradigm shift from the conventional environment-unaware communications to the new environment-aware communications based on the novel approach of channel knowledge map (CKM). This article aims to provide a comprehensive overview on environment-aware communications enabled by CKM to fully harness its benefits for 6G. First, the basic concept of CKM is presented, followed by the comparison of CKM with various existing channel inference techniques. Next, the main techniques for CKM construction are discussed, including both environment model-free and environment model-assisted approaches. Furthermore, a general framework is presented for the utilization of CKM to achieve environment-aware communications, followed by some typical CKM-aided communication scenarios. Finally, important open problems in CKM research are highlighted and potential solutions are discussed to inspire future work.

中文翻译：

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通过 6G 信道知识图进行环境感知通信的教程


第六代（6G）移动通信网络预计将具有密集的基础设施、大天线尺寸、宽带宽、高性价比的硬件、多样化的定位方法和增强的智能化。这些趋势给6G的实际设计带来了新的挑战和机遇。一方面，在 6G 中实时获取所有无线链路的信道状态信息 (CSI) 变得相当具有挑战性。另一方面，6G 中将有大量包含高质量位置标记信道数据的数据源，例如基站（BS）和用户设备（UE）之间的估计信道或波束，从而可以更好地了解本地无线环境。通过利用这一新机遇并应对 CSI 获取挑战，从传统的环境感知通信到基于信道知识图 (CKM) 新颖方法的新环境感知通信，范式转变有望实现。本文旨在全面概述 CKM 支持的环境感知通信，以充分利用其对 6G 的优势。首先，介绍了CKM的基本概念，然后将CKM与各种现有的信道推断技术进行了比较。接下来，讨论了 CKM 构建的主要技术，包括无环境模型和环境模型辅助方法。此外，提出了利用 CKM 实现环境感知通信的通用框架，然后介绍了一些典型的 CKM 辅助通信场景。最后，强调了 CKM 研究中重要的开放性问题，并讨论了潜在的解决方案，以启发未来的工作。