InDUSTRy 4.0/SMART FACToRIES


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 real-time


capability of the connection by combining the emulated traffic profile, latency measurement and transmission quality in a single interactivity test (see box out). The R&S SmartonE real-time optimisation


software enables immediate visualisation 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 centre (SmartMonitor), where they are visualised 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.


Fig. 5: Interactivity scores for various application classes. The S-shaped latency curve passes through a range of quality zones whose positions and widths vary from one application to the next.


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 neighbours 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 Freerider 4 or a network scanner mounted on a drone (Fig. 3).


SummaRy


Several industries will need to convert their current factories into smart factories. Conventionally organised 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.


Rohde & Schwarz www.rohde-schwarz.com


A nEW METHoD FoR MEASURInG nETWoRK PERFoRMAnCE E


nsuring superior network performance with full coverage is essential in factories. The latency and data


throughput must meet the minimum requirements everywhere in the coverage area. A new method implemented in the smartphone based QualiPoc Android software solution makes such measurements easy and reliable. Latencies are conventionally measured with


Fig. 3: The environment of smart factories should be periodically checked for interference, which may originate from the campus network.


ping echoes. Ping is part of the internet control message protocol (ICMP) used to exchange diagnostic and error messages in computer networks. However, the ping method has inherent accuracy shortcomings, which impact low latencies such as those needed in 5G factory networks. It is not suited for precise measurements of very low latencies and cannot emulate traffic patterns. A better method is based on the two way active measurement protocol (TWAMP), which the Internet Engineering Task Force has specified for measuring end-to-end performance between two nodes of an IP network. What TWAMP can do in a measurement application strongly depends on its


implementation. The Rohde & Schwarz solution is part of the QualiPoc Android measurement software and computes a meaningful overall score from several metrics. This innovative method has been proposed for standardisation. The QualiPoc smartphone sends a stream of


application-specific data packets via the UDP transport protocol emulating a realistic traffic profile of a specific use case class to a TWAMP capable server (TWAMP reflector), which immediately sends them back (Fig. 4). The QualiPoc software determines the round-


trip latency from reflected data, its range of variation (minimum and maximum measured values) and the packet error rate, and combines these three KPIs to form an interactivity score for this specific use case class. This is a scalable QoE model that can be tailored to different application classes. Fig. 5 shows example score curves for example use cases. The software is attractive not only for service


measurements, but also for every real-time wireless application. Suitable profiles are being developed in cooperation with the respective industries.


Fig. 4: The interactivity test based on the two way active measurement protocol (TWAMP) can measure the delay (latency) between two IP nodes and other KPIs such as packet losses.


FACToRy&HAnDLInGSoLUTIonS | DECEMbER/JAnUARy 2022 11


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