Symbol-Aware Precoder Design for Physical-Layer Anonymous Communications

TL;DR

This paper introduces a novel symbol-aware precoder design that enhances transmitter anonymity in physical-layer communications by balancing reliable decoding and anonymity constraints, using a KLD-based metric and a partitioned equal-gain combining scheme.

Contribution

It proposes a new anonymous precoding framework that maintains reliable communication while preventing transmitter identification without requiring transmitter-specific CSI.

Findings

Demonstrates anonymity-reliability tradeoffs across SNRs and data streams.

Reveals opposite anonymity trends with transmitter noise variations at different SNR regimes.

Validates the effectiveness of the proposed scheme through simulations.

Abstract

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.