FreqTune-PASS：面向多用户夹持天线系统的频率调谐波束成形
FreqTune-PASS: Frequency-Tuned Beamforming for Multi-User Pinching-Antenna Systems
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- Lancaster University（兰卡斯特大学）
- Beijing University of Posts and Telecommunications（北京邮电大学）
机构由 AI 辅助整理，请以论文原文为准。
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中文总结 AI 辅助
针对多用户夹持天线系统中机械重构慢于用户切换的问题，提出固定PA位置、仅调谐频率偏移的FreqTune-PASS框架，显著提升总速率和最差用户速率，接近相干合并上界。
中文摘要 AI 辅助
夹持天线系统（PASS）通过激活沿介质波导分布的低成本辐射点来重构大规模传播环境。然而，现有的多用户PASS设计依赖于夹持天线（PA）位置优化或激活，其机械重构速度远慢于时分多址系统中用户切换的速度。为克服这一不匹配问题，提出了一种频率调谐波束成形框架（FreqTune-PASS），其中所有PA位置保持固定，仅在每个时隙调整用户特定的载波频率偏移。由于每个PA辐射信号经历波导内和自由空间延迟的不同组合，公共频率偏移会引发路径特定的相位旋转，从而在调度用户处重塑相干叠加。基于延迟域系统模型，分别构建了快时间尺度频率偏移优化和慢时间尺度PA部署问题。针对双PA情形，推导了闭式全局最优偏移；针对多PA情形，在等间距部署下开发了低复杂度一维搜索和近似闭式偏移。部署分析进一步表明，全孔径等间距最大化保证相位调谐跨度，并为均匀分布用户产生近似算术相对延迟。数值结果表明，与固定频率传输相比，所提框架显著提升了总速率和最差用户速率，并接近相干合并上界。
英文摘要
Pinching-antenna systems (PASS) reconfigure large-scale propagation environments by activating low-cost radiation points along a dielectric waveguide. However, existing multi-user PASS designs rely on pinching-antenna (PA) position optimization or activation, whose mechanical reconfiguration is much slower than user switching in time-division multiple access systems. To overcome this mismatch, a frequency-tuned beamforming framework (FreqTune-PASS) is proposed, where all PA positions remain fixed and only a user-specific carrier-frequency offset is adjusted in each slot. Since each PA-radiated signal experiences a distinct combination of in-waveguide and free-space delays, a common frequency offset induces path-specific phase rotations and thus reshapes the coherent superposition at the scheduled user. Based on a delay-domain system model, the fast-timescale frequency-offset optimization and the slow-timescale PA-deployment problems are formulated. A closed-form globally optimal offset is derived for the two-PA case, while a low-complexity one-dimensional search and an approximate closed-form offset under equal-spacing deployment are developed for the multi-PA case. The deployment analysis further shows that full-aperture equal spacing maximizes the guaranteed phase-tuning span and yields near-arithmetic relative delays for uniformly distributed users. Numerical results demonstrate that the proposed framework substantially improves both the sum rate and the worst-user rate over fixed-frequency transmission and approaches the coherent-combining upper bound.
