Physical-layer characteristics, such as channel state information (CSI) and transmitter noise induced by hardware impairments, are often uniquely associated with a transmitter. This paper investigates transmitter anonymity at the physical layer from a signal design perspective. We consider an anonymous communication problem where the receiver should reliably decode the signal from the transmitter but should not make use of the signal to infer the transmitter's identity.Transmitter anonymity is quantified using a Kullback-Leibler divergence (KLD)-based metric, which enables the formulation of explicit anonymity constraints in the precoder design.We then propose an anonymous symbol-level precoding strategy that preserves reliable communication under spatial multiplexing while preventing transmitter identification. The proposed framework employs a partitioned equal-gain combining (P-EGC) scheme that leverages receiver diversity without requiring transmitter-specific CSI. Simulation results demonstrate anonymity-reliability tradeoffs across different signal-to-noise ratios (SNRs) and numbers of data streams. Moreover, the results reveal opposite trends of anonymity with respect to transmitter-dependent noise variations in the low-SNR and high-SNR regimes.

翻译：物理层特性，如信道状态信息（CSI）和由硬件损伤引起的发射机噪声，通常与发射机唯一关联。本文从信号设计的角度研究物理层的发射机匿名性。我们考虑一个匿名通信问题，其中接收机应可靠地解码来自发射机的信号，但不应利用该信号推断发射机的身份。发射机匿名性使用基于Kullback-Leibler散度（KLD）的度量进行量化，这使得在预编码器设计中能够制定显式的匿名性约束。随后，我们提出了一种匿名符号级预编码策略，该策略在空间复用下保持可靠通信的同时防止发射机识别。所提出的框架采用了一种分区等增益合并（P-EGC）方案，该方案利用接收机分集而不需要发射机特定的CSI。仿真结果展示了在不同信噪比（SNR）和数据流数量下的匿名性与可靠性权衡。此外，结果揭示了在低信噪比和高信噪比区域，匿名性相对于发射机相关噪声变化呈现相反的趋势。