Wireless factory automation: Radio channel evolution in repeated manufacturing processes

Wireless technologies have to be enhanced to meet the latency and reliability requirements of mission-critical machine-type communication (MTC) in automation systems. Investigating the characteristics of radio channels in typical factory environments is fundamental when designing the wireless industrial Internet of the future. In this paper, we provide results of an indoor channel measurement campaign in a representative factory automation lab. The measurements were performed at a carrier frequency of 2.25 GHz. We focus on communication between industrial robots and their controller entities over short distances. Our use case is a pick-and-place process with repetitions. We allow other active machinery and moving personnel nearby the automation cell. Based on the power delay profile and the corresponding power spectral density, we analyze the time evolution of channel snapshots on fixed spatial positions in repeated processes. Furthermore, we study the correlation of successive channel profiles along the process trajectory. By obtaining high channel correlation over time, we show that scattering and reflection effects from active and moving obstacles surrounding the manufacturing area are limited. Our findings allow a channel-aware planning of wireless control loops by optimized link adaption in wireless systems.