Experimental assessment of SDR-based 5G positioning: methodologies and insights

While GPS has traditionally been the primary positioning technology, 3GPP has more recently begun to include positioning services as native, built-in features of future-generation cellular networks. With Release 16 of the 3GPP, finalized in 2021, a significant standardization effort has taken place for positioning in 5G networks, especially in terms of physical layer signals, measurements, schemes, and architecture to meet the requirements of a wide range of regulatory, commercial and industrial use cases. However, experimentally driven research aiming to assess the real-world performance of 5G positioning is still lagging behind, root causes being (i) the slow integration of positioning technologies in open-source 5G frameworks, (ii) the complexity in setting up and properly configuring a 5G positioning testbed, and (iii) the cost of a multi-BS deployment. This paper sheds some light on all such aspects. After a brief overview of state of the art in 5G positioning and its support in open-source platforms based on software-defined radios (SDRs), we provide advice on how to set up positioning testbeds, and we demonstrate, via a set of real-world measurements, how to assess aspects such as reference signal configurations, localization algorithms, and network deployments. Our contribution further includes an assessment of the efficacy of utilizing measurements obtained from a single-link limited-size testbed to forecast localization performance in more elaborate (and hence more expensive) multi-node network settings. We posit that our methodological insights can assist in lowering the entry cost barriers associated with conducting 5G positioning experiments and, consequently, promote additional experimental research in this domain.