From Pilot to Precoding Design: Blind Angular Spoofing For Location Privacy in MIMO Systems

TL;DR

This paper introduces a blind analog precoder design for uplink MIMO systems that effectively spoofs the angular signature observed by a base station, enhancing location privacy without channel-gain knowledge.

Contribution

It proposes a novel blind precoding method that manipulates perceived angles to spoof localization, outperforming existing pilot-only approaches in multipath scenarios.

Findings

Achieves near-perfect angular spoofing in simulations.

Outperforms pilot-only blind spoofing with lower error floors.

Shows a trade-off between spoofing accuracy and communication rate.

Abstract

This paper studies location privacy in uplink MIMO systems, where a user equipment seeks to spoof the angular signature observed by a single base station performing localization. We propose a blind analog precoder design that manipulates the perceived angle-of-arrival and angle-of-departure configuration without requiring channel-gain knowledge. The method enforces consistency between the received signal and a desired spoofed angular subspace, and is solved using an alternating optimization algorithm under practical amplitude constraints. Simulations in a multipath scenario show that the proposed approach achieves near-perfect angular spoofing and clearly outperforms pilot-only blind spoofing, which exhibits an error floor. The results also show a trade-off between spoofing accuracy and communication rate, depending on the chosen virtual geometry.