CSI Obfuscation: Single-Antenna Transmitters Can Not Hide from Adversarial Multi-Antenna Radio Localization Systems
This work addresses privacy concerns for users in telecommunication systems by revealing vulnerabilities in existing obfuscation methods, though it is incremental as it builds on blind multichannel identification concepts.
The paper tackles the problem of protecting user location privacy from radio-based localization systems by showing that single-antenna transmitters using CSI obfuscation are ineffective against multi-antenna receivers, and proposes a recovery method that enables reliable localization regardless of signal obfuscation, with evaluation on real-world measurements.
The ability of modern telecommunication systems to locate users and objects in the radio environment raises justified privacy concerns. To prevent unauthorized localization, single-antenna transmitters can obfuscate the signal by convolving it with a randomized sequence prior to transmission, which alters the channel state information (CSI) estimated at the receiver. However, this strategy is only effective against CSI-based localization systems deploying single-antenna receivers. Inspired by the concept of blind multichannel identification, we propose a simple CSI recovery method for multi-antenna receivers to extract channel features that ensure reliable user localization regardless of the transmitted signal. We comparatively evaluate the impact of signal obfuscation and the proposed recovery method on the localization performance of CSI fingerprinting, channel charting, and classical triangulation using real-world channel measurements. This work aims to demonstrate the necessity for further efforts to protect the location privacy of users from adversarial radio-based localization systems.