Enhancing 5G Downlink Positioning Security: Embedding a Novel Authentication Scheme into Empty PRS Resource Elements

As wireless communication expands, there is a growing need for precise and secure location-based services. This work presents a novel authentication scheme designed to enhance security in 5G downlink positioning using the positioning reference signal (PRS). The proposed method embeds a hash-based message authentication code (HMAC) of the PRS into the empty resource elements (REs) of its comb-based structure, along with the original PRS sequence. Furthermore, a novel authentication similarity threshold is introduced, enabling the HMAC authentication process to operate under lower SNR conditions. In addition, the proposed method in the presence of channel estimation, synchronization and carrier frequency offset errors is quantified, reporting the percentage of erroneous bits in each extracted HMAC sequence. The robustness of the proposed threshold mechanism is highlighted, demonstrating its ability to tolerate bit errors caused by impairments of the physical layer. Simulations reveal that occupation of these REs does not affect position estimation.