The 5G‑Real‑Lab project in the Braunschweig‑Wolfsburg mobility region ran from 1 December 2019 to 30 June 2023 and was funded by the German Federal Ministry for Digital and Transport through the 5G Innovation Programme. The Physikalisch‑Technische Bundesanstalt (PTB) served as the technical lead, coordinating with the national network operators Deutsche Telekom and Vodafone, as well as with regional test‑field partners such as the Niedersachsen Test Field and Wolfsburg Digital. The project’s goal was to create an open, cross‑sector real‑lab that could demonstrate 5G use cases for a smart region and smart city, and to embed these demonstrations into existing living‑lab and test‑field infrastructures.

Technically, the PTB focused on passive intermodulation (PIM) measurement, a key challenge for 5G base‑station performance. In work package TP1.3 the PTB developed a vectorial PIM measurement system capable of simultaneously capturing amplitude and phase of the PIM signal. Calibration relied on five standards—short, open, load, power sensor, and phase reference—characterised with SI traceability. The “WithoutThru” algorithm was employed to correct measurement errors, and the entire calibration and measurement workflow was automated in MATLAB to minimise operator‑induced variability. The resulting system achieved source‑location accuracy within the centimetre range, as confirmed by a dedicated milestone (M08). When compared with a conventional scalar PIM system, the vectorial approach delivered lower measurement uncertainty and remained within the uncertainty bounds of the scalar method, demonstrating its superior precision.

Field validation was carried out in collaboration with Deutsche Telekom. In September 2020 a dynamic PIM measurement was performed at a multiband antenna site in Peine. The mobile PIM analyzer recorded a ten‑second trace while the antenna was lightly tapped to induce mechanical stress. The resulting data clearly revealed the onset of PIM problems, confirming the system’s sensitivity to real‑world disturbances. Additional measurements were conducted at a flat‑roof site equipped with new multiband antennas, further validating the system’s robustness under varying deployment scenarios. Throughout the project all twelve work packages were completed on schedule, with ten milestones achieved, including the first calibrated field measurement (M02) and the establishment of a laboratory measurement platform (M03).

Beyond the technical achievements, the project fostered close cooperation between academia, industry, and public administration. Regular consortium meetings, presentations at the MULCOPIM conference and the 5G Forum, and the publication of two conference papers in 2022 disseminated the findings to a broad audience. The PTB’s contributions were integrated into the overall 5G‑Real‑Lab report, which outlines how the lab’s outcomes can be scaled and transferred to other regions. The collaboration with network operators ensured that the demonstrations were carried out on live 5G networks, synchronised with the rollout of Multi‑Access Edge Computing and other 5G technology components. This alignment with the national 5G deployment strategy positioned Germany as a leading market for 5G applications and provided a blueprint for future smart‑city initiatives.