Deciding when to use wired or wireless networks on the factory floor

When it comes to establishing robust connectivity on the manufacturing floor, choosing whether to deploy a wired or a wireless connection depends on the application and factory circumstances.
 
Wired networks are usually the preferred choice when real-time data communication is required. “Wired technology is required when connectivity must be guaranteed and there are high data rates with low latency and high cycle times,” said Tom Weingartner, Director of Marketing, Industrial Ethernet Solutions at Analog Devices (ADI), which specializes in industrial semiconductor technology.
 
Wired communication enables “network redundancy,” i.e. when additional or alternate network communication mediums are installed to ensure a connection is always available.
 
Wireless networks, on the other hand, are installed in instances where it is not cost effective, or difficult to install cables. This would be the case “for existing plant infrastructure that does not support the use of wires from an edge device to a control unit,” Weingartner said.  

Wireless networks are used for devices or equipment that are highly mobile and need to be moved around on a frequent basis, such as for floor plan changes. “Wireless also has the advantage of easily being extended as is the case when a network must reach beyond the original production floor plan,” Weingartner added.
 
Wireless connectivity has a drawback, however. Weingartner noted that it was subject by nature to a higher sensitivity in noisy environments. He added that SmartMesh technology from ADI could address this issue by providing more than 99.9-percent data reliability in dynamically changing RF environments.

Applications determine the choice

It is worth noting that there are multiple connectivity choices and their use depends on the situation. “Specific types of media may be needed in areas where you have cable pathways near fluctuating power or high-vibration from motors or large air conditioners,” said Henry Martel, Senior Product Marketing Engineer for Antaira Technologies, which provides a wide range of industrial Ethernet networking solutions.
 
“The rule of ‘applications determine media’ is universal across all verticals in all industries,” Martel added.
 

Markus Weinlaender, Head of Product Management for SIMATIC Communication Modules at Siemens, pointed out that both wired and wireless protocols were able to support real-time data processing. Wireless LAN, for example, could be implemented for emergency stop buttons. “It is fast and reliable enough to support this high-demanding application,” Weinlaender said.

  “So, it is a matter of cabling cost, required bandwidth, existing infrastructure, and more,” Weinlaender said, adding that “the installed base may vary largely between different industries.”
 
The connectivity choice may differ depending on the functionality, Weingartner said. “In general, wireless connectivity is overlaid on wired connectivity as a means to monitor and gather data whereas wired connectivity is for data that controls critical systems.”

Industrial standards

Just like enterprise networks, Wi-Fi and Bluetooth solutions were already used in factory settings, said Fanny Lin, Product Manager at Siemens. Where Bluetooth is selected as the communications medium, it can be complemented by IO-Link (a short-distance point-to-point industrial networking standard) as the interface to end devices.
 
“Factory automation has many aspects,” Lin said, adding that bandwidth requirement, network resilience, security and redundancy were critical aspects to consider.
 
Nevertheless, real-time industrial data communication protocols PROFIBUS and PROFINET still hold sway. PI (PROFIBUS & PROFINET International), which has about 1,700 company members from around the world, is dedicated to automating as many production processes as possible, while linking them to enterprise systems so that data can promptly reach the right place for decision makers.

“A set of standards is currently being developed by PI Working Groups for sensor/actuator communications in conjunction with both PROFIBUS and PROFINET,” said Lin.