The integration of sensing capabilities into 6G wireless networks, known as integrated sensing and communication (ISAC), introduces severe privacy risks by enabling unauthorized user localization through the eavesdropping reference signals. Existing physical-layer defense strategies, such as artificial noise or conventional artificial multipath, suffer from critical limitations including significant communication performance degradation, reliance on unrealistic assumptions about adversarial channel state information (CSI), and increased system overhead. To address these challenges, this paper proposes a novel transparent artificial multipath (TAM) framework. It employs constant-envelope precoding and combining matrices to transparently encrypt reference signals in the frequency domain. This design ensures that legitimate base stations can perform channel estimation and localization without any performance loss, while adversaries receive a deliberately distorted channel impulse response, preventing accurate user localization and tracking. The proposed method is power-efficient, requires no prior knowledge of the adversarial CSI, and incurs negligible additional dynamic signaling overhead. Furthermore, we present a scalable multi-user extension that allows sharing the time-frequency resources without interference. Both theoretical analysis and extensive simulations demonstrate that TAM successfully misleads adversaries, inducing distance estimation errors of hundreds of meters, while fully maintaining the communication and localization performance for legitimate users. While physical-layer security solutions had a limited practical impact in various standards, the use of physical-layer techniques for privacy protection due to sensing is a necessity. We show that the proposed solution can be seamlessly integrated. into current 5G and future 6G standards.
Chen-Hu Kun, P. Popovski, Ana García Armada· IEEE Transactions on Wireles...· 0 citations
In dense deployments, massive multi-user multiple-input multiple-output (MU-MIMO) base stations can acquire instantaneous channel state information (CSI) for only a limited subset of users per scheduling interval, restricting multiuser diversity. We therefore propose Digital Twin User pre-Screening (DiTUS), a digital-twin (DT)-aided framework that identifies promising users before instantaneous CSI acquisition. DiTUS forms spatial covariances from DT-inferred departure angles and path powers. Optional Gaussian-process (GP) calibration mitigates path-power bias, while the dominant rank-r eigenspace of the aggregate covariance yields common reference beams. It prescreens the pool using DiTUS-P, a low-complexity projection-energy rule, or DiTUS-L, a greedy log-determinant rule that promotes spatial compatibility. A two-level protocol collects scalar beam reports from shortlisted users and requests r-dimensional effective-channel vectors only from the scheduled set. The framework also supports proportional-fair scheduling. At 15 dB under DT imperfections, simulations with 128 candidates, a 64-user effective-CSI acquisition budget, and a 64-user shortlist show that DiTUS-L achieves 35.06 +/- 0.49 bps/Hz versus 30.28 +/- 0.60 bps/Hz for semi-orthogonal user selection (SUS) with full-dimensional CSI from 64 users, demonstrating that DT-based prescreening preserves substantial multiuser-diversity gains by identifying strong, spatially compatible users before acquiring effective-channel vectors.
Namhyun Kim, Mahmoud Saad Abouamer, Jeonghun Park et al.· 0 citations
This work focuses on encoded teleportation, in which quantum information is encoded using a quantum error-correcting code and transmitted as a codeword, and develops a unified framework that captures the interaction between entanglement availability, decoherence, and coding decisions.
Mahmoud Saad Abouamer, Jakob Kaltoft Søndergaard, P. Popovski· arXiv.org· 0 citations
Experiments show that aeSFT identifies useful synthetic data using substantially fewer real test samples than mean-based sequential testing, matches the power of fixed-sample sign-flip testing and the paired $t$-test, while keeping the false-positive rate below the target level.
Zhenyu Tao, Wei Xu, Xiaohu You et al.· 0 citations
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