发表机构
Beijing University of Posts and Telecommunications; Peking University Shenzhen Graduate School; Tsinghua University（北京邮电大学; 北京大学深圳研究生院; 清华大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究评估3GPP NR CSI码本在近场信道中的性能，发现平面波码本导致失配损失，建议优先采用多层多波束表示并辅以范围状态细化。
AI 中文摘要
3GPP TR 38.901 Rel-19引入了天线单元级球面波建模，而NR Type-I和增强型Type-II（eType-II）CSI码本继续使用平面波DFT波束。这种不匹配是否会在标准化多径信道中实质性降低有限反馈多层预编码的性能仍不清楚。为隔离其影响，我们在严格配对的远场（FF）和近场（NF）3GPP信道上评估了这两种码本，这些信道共享用户位置、多径参数、极化和链路预算，仅波前模型不同。仿真覆盖7-GHz UMi和24-GHz InH-linear场景中的Rank 1-4传输。我们发现奇异模式增益或等功率SVD（SVD-EP）速率没有系统性FF/NF偏移。相反，球面波相位重新排序了多径在平面波候选上的投影，从而改变了码字选择。对于归一化瑞利距离为0.1的Rank-4 InH-linear用户，给定FF选择的Type-I和eType-II码字在NF信道上分别产生2.28%和5.34%的中位直接失配损失；码本重选识别出更匹配的码字，并将这些损失降低至0.770%和3.28%。嵌套候选集比较进一步表明，放宽Type-I层间约束可将SVD-EP归一化速率提高20.7个百分点，而有限范围采样仅增加0.579个百分点。这些结果支持在大孔径NR CSI码本中优先考虑多层多波束表示，范围状态提供补充细化。
英文摘要
3GPP TR 38.901 Rel-19 introduces antenna-element-level spherical-wave modeling, while NR Type-I and enhanced Type-II (eType-II) CSI codebooks continue to use plane-wave DFT beams. Whether this mismatch materially degrades finite-feedback multilayer precoding in standardized multipath channels remains unclear. To isolate its impact, we evaluate both codebooks over strictly paired far-field (FF) and near-field (NF) 3GPP channels that share user locations, multipath parameters, polarization, and link budgets and differ only in their wavefront models. Simulations cover Rank 1-4 transmission in 7-GHz UMi and 24-GHz InH-linear scenarios. We find no systematic FF/NF shift in singular-mode gains or equal-power SVD (SVD-EP) rates. Instead, spherical-wave phases reorder multipath projections onto plane-wave candidates and thereby alter codeword selection. For Rank-4 InH-linear users at 0.1 normalized Rayleigh distance, given FF-selected Type-I and eType-II codewords incur median direct mismatch losses of 2.28% and 5.34% on the NF channel, respectively; codebook reselection identifies better-matched codewords and reduces these losses to 0.770% and 3.28%. Nested candidate-set comparisons further show that relaxing Type-I interlayer constraints improves the SVD-EP-normalized rate by 20.7 percentage points, whereas finite-range sampling adds only 0.579 points. These results support prioritizing multilayer multibeam representation in large-aperture NR CSI codebooks, with range states providing complementary refinement.
