单射频链多用户语义通信：基于超表面调制
Single-RF-Chain Multiuser Semantic Communications via Metasurface Modulation
- The Chinese University of Hong Kong, Shenzhen（香港中文大学（深圳））
- Dalian University of Technology（大连理工大学）
- Aarhus University（奥胡斯大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文提出Semantic Prism框架，利用可编程超表面在单射频链接入点上实现多用户语义通信，通过学习型调制器联合映射语义与信道状态，现场测试验证其能同时服务七用户并显著提升重建性能。
AI中文摘要：
多用户传输采用多个射频（RF）链可实现灵活的空间复用，但会增加硬件复杂度和功耗。可编程超表面（MTS）为单射频链接入点（AP）引入空间自由度提供了一种替代手段。本文提出Semantic Prism，一种基于MTS的框架，用于向多个用户并发传输独立的语义消息。Semantic Prism将多用户语义表示联合映射到一个公共的AP符号序列及相应的离散MTS配置序列，使每个用户能从接收信号序列中恢复其预期消息。该映射通过一个学习型调制器实现，该调制器以多用户语义表示和信道状态信息（CSI）为输入，同时考虑MTS的离散相位控制约束。为便于实际部署，我们进一步开发了一种现场信道微调方法，以增强对CSI不确定性的鲁棒性。我们成功在400单元、2比特相位控制、工作于3.5GHz的MTS原型上实现了Semantic Prism。现场测试表明，Semantic Prism在基准方法上显著改善了多用户语义重建，并使单射频链AP能同时服务多达七个用户。
英文摘要：
Multiuser transmission with multiple radio-frequency (RF) chains enables flexible spatial multiplexing but incurs increased hardware complexity and power consumption. A programmable metasurface (MTS) provides an alternative means of introducing spatial degrees of freedom with a single-RF-chain access point (AP). This paper proposes \emph{Semantic Prism}, an MTS-enabled framework for concurrently transmitting independent semantic messages to multiple users. Semantic Prism jointly maps multiuser semantic representations to a common AP-symbol sequence and a corresponding sequence of discrete MTS configurations, enabling each user to recover its intended message from the received signal sequence. This mapping is realized by a learning-based modulator that takes both the multiuser semantic representations and channel state information (CSI) as inputs, while accounting for the discrete phase-control constraint of the MTS. To facilitate practical deployment, we further develop a field-channel fine-tuning method that enhances robustness to CSI uncertainty. We successfully implement Semantic Prism on a 400-element MTS prototype with 2-bit phase control operating at 3.5-GHz. Field tests show that Semantic Prism substantially improves multiuser semantic reconstruction over the considered baselines and enables a single-RF-chain AP to concurrently serve up to seven users.
