Latency in Cascaded Wired/Wireless Communication Networks for Factory Automation.

Unlike in the areas of process automation and condition monitoring, current wireless technologies cannot be used for many closed-loop control applications in factory automation. These applications require shorter cycle times, precise synchronicity in the microseconds range and higher reliability with low packet error rates. Furthermore, established Industrial Ethernet communication systems will not be completely replaced in the near future. Therefore, a wireless communication system for factory automation also requires seamless integration into existing networks. However, a resulting cascaded network will lead to additional latencies, which have a negative effect on the overall real-time performance. In this paper, we analyze the effect of frame structure conversion for different subnetworks with respect to the additional latencies they introduce. Therefore, we introduce an abstracted network model representing various subnetworks. We exemplify different protocol implementations and discuss them in terms of the resulting latencies and optimizations.