Block Data Delivery Time Control for Reliable Wireless Operation of Digital Factory Tools

Wireless communications have become an essential component of modern factory operations. Compared with wired communications, wireless communications can flexibly adapt to physical layout changes and movement of machines and human operators. However, wireless communications are more susceptible to influences from the surrounding environment, interference from other wireless systems and changes in signal strength due to changes in the physical environment. This requires the development of smarter communication systems that can guarantee the reliability of wireless links. In particular, the reliability of wireless links for time-sensitive communications is an important issue. This paper examines a scenario with mixed traffic of video and digital assembly tool in a factory which results in congestion where they merge at a wireless link, with increase in latency due to long waits in the wireless transmission queue. A method for traffic control at a bridge before the wireless link is proposed that balances packet delivery time (PDT) for the video streams and a new measure of block delivery time (BDT) for the digital tools. Analysis and simulations are used to show that traffic shaping with adjustable transmission weights can be effective for tuning the tradeoff between PDT of video streams and BDT of tool data. An example is presented that achieves 75% reduction of PDT for video packets to 5ms while keeping the BDT of tool data below 150ms.