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arXiv · 2608.00080

Passive AoA Estimation of COTS 5G NR Handsets from Uplink SRS: A Practical USRP-B210 Implementation

Ricardo N. Barrios-Muñoz·Azim Akhtarshenas·David Gomez-Barquero·David López-Pérez
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Abstract

This paper presents a passive network-side framework for estimating the uplink angle of arrival (AoA) of unmodified commercial 5G handsets from native Sounding Reference Signal (SRS) transmissions. The proposed system operates on an srsRAN Project gNB and estimates AoA directly from the per-antenna SRS channel estimates using a calibrated two-element Universal Software Radio Peripheral (USRP) B210 receiver and a MUSIC-based estimator, requiring neither protocol modifications nor user-equipment cooperation. Independent SRS channel estimates enable simultaneous AoA estimation for up to four commercial handsets. The framework is evaluated through indoor and outdoor measurement campaigns. Indoor measurements on bands n40 and n78 achieve a root-mean-square error of 1.5 on n40 over a 30 broadside sector. Outdoor experiments in a live 5G standalone deployment demonstrate simultaneous multi-user operation and show that estimation accuracy is primarily governed by propagation conditions and received signalto-interference-plus-noise ratio (SINR) rather than transmitter distance. These results demonstrate the feasibility of passive uplink AoA estimation using native 5G signaling, low-cost SDR hardware, and commercial handsets.

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Ricardo N. Barrios-Muñoz, Azim Akhtarshenas, David Gomez-Barquero, David López-Pérez. 2026-09-09. Passive AoA Estimation of COTS 5G NR Handsets from Uplink SRS: A Practical USRP-B210 Implementation. https://arxiv.org/abs/2608.00080

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