📝 SummarXiv

Abstract

Recently, a novel ultra-low-power indoor localization system based on Zero-Energy Devices (ZEDs) has shown promising results in ambient backscatter communication. In this paper, we study detection of multiple coexisting ZEDs in ambient backscatter systems under interference and synchronization uncertainty. Building on a Neyman-Pearson (NP) formulation previously applied to single-tag detection, we introduce a detector tailored to multi-tag scenarios. The core idea is to use a Near-Perfect Code (NPC) as the synchronization sequence, which substantially improves the peak-to-sidelobe (PSL) ratio and thus separability among concurrent tags. The proposed scheme replaces dual band-pass filtering with dual correlators, enabling an explicit Bayesian detector and tight control of the false-alarm rate; we further incorporate a contrast metric and multi-frequency combining to reveal secondary tags. Experiments on the CorteXlab testbed (part of the SLICES-EU infrastructure) confirm robustness at low SNR, with observed PSL improvements from about 11 dB to about 22 dB. These results advance scalable, reliable ambient backscatter localization in practical multi-tag environments.