AI 中文总结
本文针对6G的新型中频段XL-MIMO，综述其频谱规划、信道建模、算法进展，比较不同规模XL-MIMO系统性能，结合U6GHz频段现场试验，明确目标信噪比是影响XL-MIMO性能的关键因素。
AI 中文摘要
新型中频段（FR3，6-24 GHz）频谱有望在未来6G网络中发挥重要作用，它能在覆盖范围、容量和部署可行性之间提供良好的平衡。与此同时，超大規模多输入多输出（XL-MIMO）已成为开发这些频段的传播和空间复用潜力的关键使能技术。首先，本文系统综述了新型中频段频谱的频谱分配和标准化活动，以及各国和地区的6G频谱规划策略。其次，介绍了专为新型中频段信道测量开发的宽带大规模MIMO信道探测仪，该探测仪配备了超过1000个天线单元。第三，全面综述并分析了四种代表性XL-MIMO架构（包括共址、无小区和智能XL-MIMO）的传播特性和信道建模方法，特别强调了近场传播、空间非平稳性和容量性能。接着，总结了信道估计、波束成形和人工智能辅助信号处理的最新进展。此外，对配备1536个和768个天线单元的新型中频段XL-MIMO系统的性能进行了比较评估。最后，利用在6GHz以上（U6GHz）频段开展的实际通信环境原型系统现场试验，研究了实际部署条件下的实际系统性能。结果表明，目标信噪比是影响U6GHz频段XL-MIMO性能的关键因素。
英文摘要
The new mid-band (FR3, 6-24 GHz) spectrum is expected to play an important role in future 6G networks by providing a favorable balance among coverage, capacity, and deployment feasibility. Meanwhile, extremely large-scale multiple-input multiple-output (XL-MIMO) has emerged as a key enabling technology to exploit the propagation and spatial multiplexing potential of these frequency bands. Firstly, this paper provides a systematic review of spectrum allocation and standardization activities for new mid-band spectrum, together with the 6G spectrum planning strategies of countries and regions. Secondly, the wideband massive MIMO channel sounder is also introduced, which is specially developed for channel measurements of new mid-band with over a thousand elements. Thirdly, propagation characteristics and channel modeling approaches of four representative XL-MIMO architectures, including co-located, cell-free, and intelligent XL-MIMO, are comprehensively reviewed and analyzed, with particular emphasis on near-field propagation, spatial non-stationarity, and capacity performance. Then, recent advances in channel estimation, beamforming, and artificial-intelligence-assisted signal processing are summarized. In addition, the performance of new mid-band XL-MIMO systems equipped with 1536 and 768 antenna elements is comparatively evaluated. Finally, real communication environment prototype system field trials conducted in the Upper 6 GHz (U6GHz) band are used to investigate practical system performance under realistic deployment conditions. The results indicate that the target signal-to-noise ratio is a critical factor affecting XL-MIMO performance in the U6GHz band.
