Smart Factories

Vital KPIs for mobile network in wireless connected factories

A smart factory is a critical environment that must fulfill strict requirements for machine connectivity and reliability as well as data security and human safety, especially if connectivity is provided by wireless technologies.

Redundancy is a proven way to increase reliability. Every location in a smart factory must be served by at least four wireless access points. On-site tests are the only way to verify this access, not only upon installation but after every machinery reconfiguration or change to the building layout, since structural changes can impact the propagation conditions of radio waves.

Reliable ubiquitous wireless accessibility is necessary but not sufficient for trouble-free operation. Another requirement is the proper performance measured not only in achievable data throughput but also – and often more importantly – latency or the time needed for a signal to pass through the system. The latencies of previous mobile communications technologies, up to and including 4G, were not short enough to meet real-time control requirements. This is no longer true for 5G, which has latencies of a few milliseconds.

Latency comes in two forms: round-trip and one-way (Fig. 1). Augmented or virtual reality use cases need short round-trip latency for very quick image content updates when people wearing AR/VR glasses move their head, to keep the merged data consistent with the live image. By contrast, real-time control of a connected machine requires low one-way latency. Control commands, for example a stop command for a robot, must lead to immediate action.

The five phases of network testing

When planning a factory as a whole, wireless networks are implemented in phases based on a five-phase test plan. Fig.2 shows the first four phases for verifying that the network fulfuls strict reliability and performance requirements.

Phase 1: Rollout preparation

In Germany and some other countries, 5G frequencies are reserved for campus networks or private networks and factory operators can apply to use these frequencies. Setup and operation of the network can be organized inhouse, but is usually done by service providers. In countries without dedicated campus frequencies, factory connectivity involves booking resources from a major network operator, who in turn consolidates their network around the factory or installs additional base stations in the factory to meet requirements.

If the network uses campus frequency bands, the spectrum needs an initial check for interference. Experience shows that this cannot be taken for granted with a newly assigned and previously unused spectrum. R&S®TSMx6 network scanners, R&S®FPH/R&S®FSH handheld spectrum analyzers and R&S®MNT100/R&S®PR200 portable test receivers perform the necessary measurements.

Phase 2: Site acceptance testing

The second phase involves testing and validating newly deployed base stations. This includes simple functional tests such as download/upload tests, round-trip latency measurements, over-the-air (OTA) RF spectrum analyses and signal decoding to verify PCI, SSB and SIB data for 5G and LTE anchor signals.

Signal decoding also helps troubleshooting specific parameters in case of problems or unexpected results. The Rohde & Schwarz product portfolio has the right instruments for these tasks. QualiPoc Android, a smartphone based measurement software, evaluates the mobile network service from the user perspective with functional tests (DL, UL, ping/TWAMP). The R&S®Spectrum Rider FPH handheld spectrum analyzer is ideal for OTA spectrum measurements, while the R&S®5G site testing solution provides a comprehensive mobile network situational overview that allows quick identification of any weaknesses or problem areas.

Phase 3: Coverage and performance testing

Now comes the real test. The aim is to make sure the network delivers the required performance throughout the entire factory. R&S®TSMx6 network scanners measure over the entire factory site to see how many different network access points have good reference signal received power (RSRP) and good quality as signal to interference plus noise ratio (SINR) at every location. As previously mentioned, at least fourfold redundancy is desirable. QualiPoc Android can test the realtime capability of the connection by combining the emulated traffic profile, latency measurement and transmission quality in a single interactivity test (see Fig. 4 and 5). The R&S®SmartONE real-time optimization software enables immediate visualization of measurement results and targeted improvement of problem areas.

Phase 4: Service quality monitoring

Phase 4 measurements are necessary in factories where the wireless network is critical infrastructure where malfunction would result in large profitability and productivity losses. This means the factory owner needs a clearly defined service level agreement (SLA) with their network operator and the ability to continuously check compliance with the SLA. Custom RF sensors are distributed throughout the factory and in automated guided vehicles (AGV) and autonomous mobile robots (AMR). They periodically measure connection quality – including latency – at every location and report the results to the monitoring center (SmartMonitor), where they are visualized on a real-time dashboard. Tools like SmartAnalytics offer more detailed offline data analysis. The software uses machine learning to identify trends and anomalies and promptly indicates aberrations so that preventive measures can be taken before the fault case actually occurs.

Phase 5: Verifying prescribed compatibility with the outside world

Completion of phase 4 marks the end of the setup process and the network is operational. The final task is to ensure compliance with the license conditions for private networks that specify leakage signals outside the intended coverage area must remain below defined limits. This helps prevent interference with any neighbors using the same frequency band or an adjacent frequency band. Factory owners are recommended to check compliance and can do this with a walk test solution such as the R&S®Freerider4 or a network scanner mounted on a drone (Fig. 3).

Summary

Several industries will need to convert their current factories into smart factories. Conventionally organized operations will have difficulty competing with the flexibility and cost advantages of the new generation of factories. One feature is complete connectivity of equipment with low latency (5G) wireless communications. The right T&M support makes setting up and operating these networks easy. The Rohde & Schwarz product portfolio offers network operators and factory owners everything they need.