Robots that stop dropping off the network: private 5G on CBRS spectrum for a Tier-1 auto plant

A supplier of axle shafts and gear sets lives on thin margins and strict customer rules: traceable safety-critical parts, falling defect rates and no late shipments. This plant had added autonomous mobile robots, wireless sensors and inspection cameras faster than its Wi-Fi could carry them. Robots dropped their session between access points, mostly near the big steel presses, and every dropout stopped a machine until someone walked over to recover it.

Adding access points never fixed it. Metal structures, welding equipment and more than a kilometer of aisles left gaps that a denser Wi-Fi layout only moved around. After comparing a Wi-Fi 6E upgrade with private cellular, we chose private 5G in the CBRS band. The spectrum is shared under 47 CFR Part 96: a Spectrum Access System authorizes and manages use of the band, and the plant operates on General Authorized Access, so there is no license to buy. Mobility is built into cellular, which is exactly what a roaming robot needs.

The design is edge first. Robot fleet management, local breakout and vision inference run on a compute rack inside the plant, so the line keeps moving if the internet link fails. Every device authenticates with a SIM or eSIM tied to an inventory record, and a lost or retired device is revoked in seconds. Separate quality-of-service profiles keep robot control low latency while inspection video takes the bandwidth. The production network sits in its own zone, apart from corporate devices, with logged flows out.

We started with a survey and a one-hall pilot, measuring before and after so leadership could see the difference before funding the rest. Rollout then covered the whole plant, and industrial 5G gateways brought the older robots along without replacing them. Two radio units moved after the pilot to clear the shadows behind the presses. The maintenance team did not trust predictive alerts at first, so the models ran in shadow mode for weeks, showing predictions next to actual failures, until the alerts earned their place in the work-order system.

The number the plant manager watches is the weekly count of robot connectivity stoppages: about 41 a week on Wi-Fi, about 2 a week on private 5G, and roughly 30 operator hours a week of robot recovery handed back to production. The floor that needed about 212 Wi-Fi access points now runs on 18 radio units, which is a good deal less to survey, power, patch and replace. For fairness, a well-tuned Wi-Fi network can hand a client between access points in about 40 milliseconds when 802.11r, k and v are all in use, but that depends on every client supporting them, and older industrial devices often do not. Cellular makes mobility a property of the network instead of a feature each device must bring. The use cases the business cared about now sit on top: reliable robot hand-offs, sensors on far more spindles, vision inspection of every part instead of a sample, and traceability that ties a serial number to its machine, tool and inspection images. The figures are modeled and the engagement is illustrative. What carries over is the method: lead with downtime and quality rather than with 5G, pilot with a baseline, plan for legacy devices and keep the plant able to run on its own.