Wi-Fi sensing as a side-effect of communications is opening new opportunities for smart services integrating communications with environmental properties, first and foremost the position of devices and people. At the same time, this technology represents an unprecedented threat to people's privacy, as personal information can be collected directly at the physical layer without any possibility to hide or protect it. Several works already discussed the possibility of safeguarding users' privacy without hampering communication performance. Usually, some signal pre-processing at the transmitter side is needed to introduce pseudo-random (artificial) patterns in the channel response estimated at the receiver, preventing the extraction of meaningful information from the channel state. However, there is currently just one implementation of such techniques in a real system (openwifi), and it has never been tested for performance. In this work, we present the implementation of a location obfuscation technique within the openwifi project that enables fine manipulation of the radio signal at transmitter side and yields acceptable, if not good, performance. The paper discusses the implementation of the obfuscation subsystem, its performance, possible improvements, and further steps to allow authorized devices to "de-obfuscate" the signal and retrieve the sensed information.
The path toward 6G is still long and blurred, but a few key points seems to be already decided: Integration of many different access networks; Adoption of massive MIMO technologies; Use of frequencies above current radio spectrum up to THz and beyond; Inclusion of Artificial Intelligence and Machine Learning in standard management and operations. One additional point that is less discussed, but seems key for success, is the advanced use of Channel State Information (CSI) both for equalization and decoding purposes and for sensing ones. CSI-based sensing promises a plethora of new applications and a quantum leap in service personalization and customercentric network management. At the same time CSI analysis, being based on the physical characteristics of the propagated signal, poses novel threats to people's privacy and security: No software-based solution or cryptographic method above the physical layer can prevent the analysis of the CSI. The CSI analysis can reveal people's position or activity, allow tracking them, discover details on the environment that today can be seen only with cameras or radars. In this paper we discuss the current status of CSI-based sensing and present some technologies that can protect people's privacy and at the same time allow legitimate use of the information carried by the CSI to offer better services.
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