[简介] 文章深入探讨了基于AI的信道信息预测在6G通信系统中的应用，并从信道信息预测的信道模型、信道信息预测方案、数据收集方法、模型监控技术、仿真验证结果，以及基于AI的信道信息预测所面临的机会与挑战这7个维度展开分析。在信道信息预测方案的分析中，广泛探索了多种信道信息预测策略；在数据收集部分，详细分析了不同参考信号传输类型及数据收集范围的影响；在模型监控方面，讨论了3种可能的监控方式。此外，通过仿真验证，充分展示了基于AI的信道信息预测技术的有效性和优越性。

[简介]全球范围内已开启6G研究浪潮，为满足不断攀升的数据传输速率需求，扩大频带宽度、增加天线数量是直接有效手段。在6G应用场景与关键能力驱动下，6425~7125 MHz频段（U6G）超大规模多输入多输出（MIMO）技术成为满足6G需求的潜在使能技术之一。基于U6G超大规模MIMO系统的天线形态及信道特征，针对该技术面临的成本、开销、复杂度三重挑战，提出高效能U6G超大规模MIMO无线传输的总体设计目标，并展望其未来研究趋势。

[Introduction] In the context of edge computing environments in general and the metaverse in particular, federated learning (FL) has emerged as a distributed machine learning paradigm that allows multiple users to collaborate on training a shared machine learning model locally, eliminating the need for uploading raw data to a central server. It is perhaps the only training paradigm that preserves the privacy of user data, which is essential for computing environments as personal as the metaverse. However, the original FL architecture proposed is not scalable to a large number of user devices in the metaverse community. To mitigate this problem, hierarchical federated learning (HFL) has been introduced as a general distributed learning paradigm, and has since then inspired and led to a number of research works. In this paper, we present several types of HFL architectures, with a special focus on the three-layer client-edge-cloud HFL architecture, which is most pertinent to the metaverse due to its delay-sensitive nature. We also examine works that take advantage of the natural layered organization of three-layer client-edge-cloud HFL to tackle some of the most challenging problems in FL within the metaverse. Finally, we outline some future research directions of HFL in the metaverse.

[Introduction] Femtosecond laser direct inscription is a technique especially useful for prototyping purposes due to its distinctive advantages such as high fabrication accuracy, true 3D processing flexibility, and no need for mold or photomask. In this paper, we demonstrate the design and fabrication of a planar lightwave circuit (PLC) power splitter encoded with waveguide Bragg gratings (WBG) using a femtosecond laser inscription technique for passive optical network (PON) fault localization application. Both the reflected wavelengths and intervals of WBGs can be conveniently tuned. In the experiment, we succeeded in directly inscribing WBGs in 1×4 PLC splitter chips with a wavelength interval of about 4 nm and an adjustable reflectivity of up to 70% in the C-band. The proposed method is suitable for the prototyping of a PLC splitter encoded with WBG for PON fault localization applications.